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WO2022133963A1 - 电池组、电池包、电学装置以及电池组的制造方法及制造设备 - Google Patents

电池组、电池包、电学装置以及电池组的制造方法及制造设备 Download PDF

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Publication number
WO2022133963A1
WO2022133963A1 PCT/CN2020/139184 CN2020139184W WO2022133963A1 WO 2022133963 A1 WO2022133963 A1 WO 2022133963A1 CN 2020139184 W CN2020139184 W CN 2020139184W WO 2022133963 A1 WO2022133963 A1 WO 2022133963A1
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WIPO (PCT)
Prior art keywords
cell
pole piece
battery
negative pole
type
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Application number
PCT/CN2020/139184
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English (en)
French (fr)
Inventor
刘倩
梁成都
叶永煌
金海族
Original Assignee
宁德时代新能源科技股份有限公司
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to EP20945720.9A priority Critical patent/EP4047711A4/en
Priority to PCT/CN2020/139184 priority patent/WO2022133963A1/zh
Priority to CN202080055106.5A priority patent/CN114982035B/zh
Publication of WO2022133963A1 publication Critical patent/WO2022133963A1/zh
Priority to US17/887,220 priority patent/US20220399607A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/267—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders having means for adapting to batteries or cells of different types or different sizes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/0404—Machines for assembling batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/0431—Cells with wound or folded electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/482—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/387—Tin or alloys based on tin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/249—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders specially adapted for aircraft or vehicles, e.g. cars or trains
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
    • H01M50/509—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing characterised by the type of connection, e.g. mixed connections
    • H01M50/51—Connection only in series
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/258—Modular batteries; Casings provided with means for assembling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of energy storage devices, and in particular, to a battery pack, a battery pack, an electrical device, a method for manufacturing a battery pack, and a manufacturing device for a battery pack.
  • Secondary batteries have the advantages of small size, high energy density, high power density, many cycles of use and long storage time, and are widely used in some electronic equipment, electric vehicles, electric toys and electric equipment, such as mobile phones, notebook computers, Battery cars, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes and electric tools, etc. Secondary batteries are used as power drive power sources for new energy vehicles or large-capacity storage units in energy storage power stations. Usually, multiple single cells need to be connected in series or in parallel to obtain battery packs and battery packs with higher volumetric energy density.
  • a technical solution is proposed to connect a plurality of single cells of different chemical systems in series and/or parallel to form a battery group, wherein a type of cell, for example, has a high energy density ternary batteries containing lithium nickel cobalt manganate lithium metal oxide, another type of batteries such as lithium iron phosphate batteries with high safety.
  • a type of cell for example, has a high energy density ternary batteries containing lithium nickel cobalt manganate lithium metal oxide, another type of batteries such as lithium iron phosphate batteries with high safety.
  • the capacity decay characteristics and the charge-discharge characteristics of the cycle process are significantly different.
  • the long-term cycle performance of the battery pack is often limited by the single cells with worse cycle performance, which makes it difficult for some cells in the battery pack to give full play to their electrical performance advantages.
  • the present application is made in view of the above-mentioned problems in the prior art, and its purpose is to provide a battery pack, by matching the total charging capacity of the negative pole pieces of the cells of different chemical systems, to The capacity design of the chemical system cells is optimized to achieve a long cycle life of the hybrid series module.
  • a first aspect of the present application provides a battery pack including at least first type cells and second type cells connected in series, wherein the first type cells and the second type cells are of different chemistries System batteries, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, and N and M are positive integers;
  • the first negative electrode of the first cell is The ratio of the total charging capacity of the pole piece to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2.
  • the SOH of the battery state of health of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell
  • the ratio of the total charging capacity of the first negative pole piece to the total charging capacity of the second negative pole piece is 0.9 to 1.1.
  • the ratio of the discharge capacity of the first negative pole piece to the discharge capacity of the second negative pole piece is 0.8 to 1.2.
  • the ratio of the discharge capacity of the first negative pole piece to the discharge capacity of the second negative pole piece is 0.9 to 1.1.
  • the ratio of the rated capacity of the first type of batteries to the rated capacity of the second type of batteries is 0.8 to 1.2, optionally 0.9 to 1.1.
  • the first negative pole piece and the second negative pole piece also satisfy at least one of the following conditions: (1) the compaction density of the first negative pole piece and the density of the second negative pole piece; The ratio of the compaction density is 0.85 to 1.15, optionally 0.95 to 1.05; (2) the ratio of the coating mass per unit area of the first negative pole piece to the coating mass per unit area of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05; (3) the ratio of the porosity of the first negative pole piece to the porosity of the second negative pole piece is 0.8 to 1.25, optionally 0.9 to 1.1.
  • the density of the first negative pole piece and the density of the second negative pole piece are independently 1.0 g/cm 3 to 1.9 g/cm 3 , optionally 1.2 g/cm 3 to 1.8 g/cm 3 .
  • the coating mass per unit area of the first negative pole piece and the coating mass per unit area of the second negative pole piece are independently 6 mg/cm 2 to 17 mg/cm 2 , optionally 8 mg /cm 2 to 14 mg/cm 2 .
  • the porosity of the first negative pole piece and the porosity of the second negative pole piece are each independently 15% to 35%, optionally 20% to 30%.
  • the negative active material of the first negative pole piece and the negative active material of the second negative pole piece can be independently selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials.
  • the ratio of the number of the first type of batteries to the number of the second type of batteries is 0.1 to 50, optionally 2 to 10.
  • a second aspect of the present application provides a battery pack, including the battery pack described in the first aspect.
  • a third aspect of the present application provides an electrical device, comprising the battery pack according to the first aspect or the battery pack according to the second aspect, and using the battery pack or the battery pack as the electrical device power supply or energy storage unit.
  • a fourth aspect of the present application provides a method for manufacturing a battery pack, comprising the steps of: obtaining a first-type battery cell and a second-type battery cell, wherein the first-type battery cell and the second-type battery cell are of different chemical systems batteries, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, and N and M are positive integers;
  • the first negative electrode of the first cell is The ratio of the total charging capacity of the sheet to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2; the first type of cell and the second type of cell are electrically connected in a manner including a series connection , to form the battery pack described in the first aspect.
  • a fifth aspect of the present application provides a battery pack manufacturing equipment, including: a clamping arm unit, the clamping arm unit is used to obtain a first type of battery cell and a second type of battery cell, the first type of battery cell
  • the cells of the second type are cells of different chemical systems, the cells of the first type include N first cells, the cells of the second type include M second cells, and N and M are positive integers ; in the case that the state of health SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell,
  • the ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is 0.8 to 1.2; the assembling unit is used to combine the The first type of battery cell and the second type of battery cell are electrically connected in a manner including series connection to form the battery pack described in the first aspect above; and a control unit for controlling the clip arm unit and the assembly unit
  • a battery pack includes at least a first type of battery cell and a second type of battery cell with different chemical systems connected in series.
  • the total charging capacity of the battery is set within a specific range to ensure that the life decay rates of cells of different chemical systems are as close as possible during long-term use, thereby avoiding the short life of certain types of cells in the hybrid series module, and significantly improving the model.
  • the overall cycle life of the group is set within a specific range to ensure that the life decay rates of cells of different chemical systems are as close as possible during long-term use, thereby avoiding the short life of certain types of cells in the hybrid series module, and significantly improving the model.
  • the battery pack and the electrical device in the present application include the battery pack, they have at least the same technical advantages as the battery pack.
  • FIG. 1 is a schematic diagram showing one example of a cell of the present application.
  • FIG. 2 is an exploded view showing one example of the cell of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram showing one example of the battery pack of the present application.
  • FIG. 4 is a schematic diagram showing one example of the battery pack of the present application.
  • FIG. 5 is an exploded view showing one example of the battery pack of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram showing an example of an electrical device using the battery pack of the present application as a power source.
  • a “range” disclosed herein is defined in the form of a lower limit and an upper limit, a given range being defined by the selection of a lower limit and an upper limit, the selected lower limit and the upper limit defining the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive, and may be arbitrarily combined, ie, any lower limit may be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is to be understood that the ranges of 60-110 and 80-120 are also contemplated.
  • the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where both a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" have been listed in the text, and "0-5" is just an abbreviated representation of the combination of these numerical values.
  • a parameter is expressed as an integer greater than or equal to 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.
  • the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • reference to the method may further include step (c), indicating that step (c) may be added to the method in any order, eg, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • the "comprising” and “comprising” mentioned in this document indicate an open type, and can also be a closed type.
  • the terms “comprising” and “comprising” can mean that other components not listed may also be included or included, or only the listed components may be included or included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B.” More specifically, the condition “A or B” is satisfied by either of the following: A is true (or present) and B is false (or absent); A is false (or absent) and B is true (or present) ; or both A and B are true (or present).
  • cell refers to a battery cell that can be independently charged and discharged.
  • the components of the battery cell may include positive pole pieces, negative pole pieces, separators, electrolytes, and outer packaging for encapsulating the positive pole pieces, negative pole pieces, separators, and electrolytes.
  • the application does not have any special restrictions on the type and shape of the cells, which may be soft-wrapped cells, cylindrical cells, or square cells and other types of cells.
  • the batteries in this application can be lithium-ion batteries, potassium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, etc., and are particularly preferably lithium-ion batteries.
  • active ions are inserted and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the "chemical system" of the battery cell is divided according to the composition of the positive electrode active material used in the positive electrode sheet in the battery cell, and the elements or substances that are doped or coated with the positive electrode active material are not limited.
  • a battery cell whose positive active material is lithium iron phosphate (including doped with Mn or V element) can be defined as a lithium iron phosphate chemical system battery cell.
  • a battery cell whose positive active material is nickel cobalt lithium manganate (generally referred to as NCM) can be defined as a battery cell of an NCM chemical system.
  • the chemical system of the cell can be further limited according to the relative contents of nickel , cobalt , and manganese in the positive electrode active material.
  • the positive active material is LiNi 0.6 Co 0.2 Mn 0.2 O 2 (generally referred to as NCM622) battery can be defined as NCM622 chemical system battery, the positive active material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 ( Generally referred to as NCM811) cells can be defined as NCM811 chemical system cells.
  • the nickel-cobalt-aluminate lithium system battery (commonly referred to as NCA) as the positive electrode material can be defined as the NCA chemical system battery.
  • NCA nickel-cobalt-aluminate lithium system battery
  • a hybrid system cell can also be used, for example, a hybrid system cell including NCM and NCA.
  • the battery cell of the present application includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer contains a negative electrode active material.
  • the negative electrode active material of the negative electrode film layer may include common negative electrode active materials, for example, natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate one or more of them.
  • the silicon-based material may be selected from one or more of elemental silicon, silicon oxide, and silicon-carbon composite.
  • the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.
  • the negative electrode film comprises negative electrode active material and optional binder, optional conductive agent and other optional auxiliary agents, and is usually formed by coating and drying the negative electrode slurry.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the conductive agent may include one or more of superconducting carbon, carbon black (eg, acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • carbon black eg, acetylene black, ketjen black
  • carbon dots carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA) , one or more of sodium alginate (SA) and carboxymethyl chitosan (CMCS).
  • the binder may include one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS) or several.
  • Other optional auxiliary agents are, for example, thickeners (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, and the like.
  • the negative pole piece does not exclude other additional functional layers other than the negative electrode film layer.
  • the negative electrode sheet of the present application may further include a conductive primer layer (eg, a conductive agent and a bonding agent) disposed on the surface of the negative electrode current collector sandwiched between the negative electrode current collector and the first negative electrode film layer. composition).
  • the negative electrode sheet of the present application may further include a protective cover layer covering the surface of the second negative electrode film layer.
  • the negative electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be a foil composed of copper foil, silver foil, iron foil, or an alloy of the above metals.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. ) formed on the base layer of polymer materials (such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.). formed on the base layer).
  • polymer materials such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.
  • the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be an aluminum foil, and the composite current collector may include a polymer material base layer and a layer formed on the polymer material. A metal layer on at least one surface of the material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) Glycol ester PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers etc.
  • metal materials aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.
  • Glycol ester PET polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers etc.
  • the positive electrode active material can be a known positive electrode active material for battery cells in the art.
  • the positive active material may include one or more of the following: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for battery cells can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include but are not limited to lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)), lithium nickel cobalt aluminum oxide (such as One or more of LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds.
  • lithium cobalt oxides such as LiCoO 2
  • lithium nickel oxides such as LiNi
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (eg, LiFePO 4 (LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (eg, LiMnPO 4 ), lithium manganese phosphate and carbon One or more of the composite materials, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composite materials.
  • lithium iron phosphate eg, LiFePO 4 (LFP)
  • composites of lithium iron phosphate and carbon lithium manganese phosphate (eg, LiMnPO 4 )
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer also optionally includes a binder.
  • binders that can be used in the positive film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene tri- Element copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene-propylene tri- Element copolymer
  • vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer vinyliden
  • the positive electrode film layer may also optionally contain a conductive agent.
  • the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (such as N- Methylpyrrolidone), a uniform positive electrode slurry is formed; the positive electrode slurry is coated on the positive electrode current collector, and the positive electrode sheet can be obtained after drying, cold pressing and other processes.
  • a solvent such as N- Methylpyrrolidone
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), bisfluorosulfonylidene Lithium Amide (LiFSI), Lithium Bistrifluoromethanesulfonimide (LiTFSI), Lithium Trifluoromethanesulfonate (LiTFS), Lithium Difluorooxalate Borate (LiDFOB), Lithium Dioxalate Borate (LiBOB), Lithium Difluorophosphate One or more of (LiPO 2 F 2 ), lithium difluorodioxalate phosphat
  • the solvent may be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate ( DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC) ), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and Eth
  • the content of the solvent is 60-99 wt %, for example, 65-95 wt %, or 70-90 wt %, or 75- 89% by weight, or 80-85% by weight. In an embodiment of the present application, based on the total weight of the electrolyte, the content of the electrolyte is 1-40 wt %, for example 5-35 wt %, or 10-30 wt %, or 11- 25% by weight, or 15-20% by weight.
  • the electrolyte may optionally contain additives.
  • the additives may include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance of the battery, such as additives to improve battery overcharge performance, additives to improve battery high temperature performance, Additives to improve low temperature performance of batteries, etc.
  • the cell further includes a separator, which separates the anode side from the cathode side of the cell, and provides selective permeation or barrier to substances of different types, sizes and charges in the system
  • the separator can insulate the electrons, physically isolate the positive and negative active materials of the cell, prevent the internal short circuit and form an electric field in a certain direction, and at the same time enable the ions in the battery to pass through the separator to move between the positive and negative electrodes.
  • the material used to prepare the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.
  • the above-mentioned positive electrode sheet, negative electrode sheet and separator can be made into electrode assemblies/bare cell cores through a winding process or a lamination process.
  • the cell may include an outer package, and the outer package may be used to encapsulate the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the cell may be a hard case, such as a hard plastic case, an aluminum case, a steel case, and the like.
  • the outer package of the battery cell may be a soft package, such as a bag-type soft package.
  • the material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • FIG. 1 is a schematic diagram showing one example of the battery cell 5 of the present application.
  • FIG. 2 is an exploded view showing one example of the battery cell 5 of the present application shown in FIG. 1 .
  • the outer package may include a casing 51 and a cover plate 53 , the casing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity.
  • the housing 51 has an opening that communicates with the accommodating cavity, and a cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be rolled or laminated to form the electrode assembly 52 , the electrode assembly is packaged in the accommodating cavity, and the electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 included in the battery cell 5 may be one or more.
  • a “battery pack” is formed by electrically connecting a certain number of cells together and putting them into a frame in order to protect the cells from external impact, heat, vibration, etc.
  • the shape of the battery cell of the present application can be cylindrical, square or any other shape.
  • the battery pack contains two or more cells, the specific number of which depends on the application of the battery pack and the parameters of a single battery pack.
  • FIG. 3 is a schematic diagram showing one example of the battery pack of the present application.
  • a plurality of cells 5a, 5b may be arranged in sequence along the length direction of the battery pack 4 (5a may be the first cell, 5b may be the second cell). Of course, it can also be arranged in any other manner. Further, the plurality of battery cells 5a and 5b can be fixed by fasteners.
  • the battery pack 4 may further include a housing having an accommodating space, and the plurality of packs 5a, 5b are accommodated in the accommodating space.
  • a battery pack includes at least a first type of battery cell and a second type of battery cell connected in series, the first type of battery cell and the second type of battery cell are cells of different chemical systems, the first type of battery cell
  • the cell includes N cells, the first type of cell includes a first cell; the second type of cell includes M cells, and the second type of cell includes a second cell; N and M is a positive integer; the SOH of the battery state of health of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell
  • the ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is 0.8 to 1.2.
  • SOH represents the state of health (State of Health), which refers to the ratio of the total capacity of the current cell to the initial total capacity of the cell. For example, it can be 100%, 98%, 95%, 90%, 85%, 80%, 75%, 70%.
  • SOC represents the state of charge (State Of Charge), which refers to the ratio of the remaining power of the current cell to the rated capacity under the same conditions, for example, it can be 100%, 99%, 90%, 80%, 70%, 60% %, 50%, 40%, 30%, 20%, 10%, 0%.
  • the range referred to by "the state of health SOH of the first cell is the same as the SOH of the second cell” in this application refers to the state of health SOH of the first cell
  • the ratio of the absolute value of the difference from the SOH of the second cell to the average value of the two is not more than 5%.
  • the state of charge SOC of the first cell is the same as the SOC of the second cell
  • the SOH of the first cell and the SOH of the second cell can be obtained by testing methods known in the art.
  • the following methods can be used to test:
  • the discharge capacity measured from step 3) to step 4) is recorded as Capx.
  • the percentage of Capx to the rated capacity C is the SOH.
  • the SOC of the first battery cell and the SOC of the second battery cell can be obtained by testing methods known in the art. As an example, the following methods can be used to test:
  • adjusting the SOH of the first cell and the SOH of the second cell to the same method can be performed by using a method known in the art.
  • the following methods can be used to adjust:
  • the SOH of a certain cell can be adjusted as the target SOH of the higher SOH cell.
  • the adjustment method refer to the cycle life test method in GB/T 31484-2015 "Cycle Life Requirements and Test Methods of Power Batteries for Electric Vehicles" until the percentage of the actual capacity of the cells to the rated capacity reaches the target value.
  • the cycle life test process is as follows:
  • Steps 3) to 4) are one charge-discharge cycle for the battery cell.
  • the method of adjusting the SOC of the first battery cell and the SOC of the second battery cell to be the same can be performed by using a method known in the art.
  • the following methods can be used to adjust:
  • the method of adjusting SOC is as follows:
  • the steps to adjust the SOC process are as follows: 1) Let the cell to be tested stand at 25°C for 30 minutes; 2) 0.33C constant current discharge to the cell discharge termination voltage, and then stand for 30 minutes ; 3) 0.33C constant current charge to the cell charging termination voltage, constant voltage charging to the current ⁇ 0.05C, let stand for 5 minutes; 4) 0.33C constant current discharge to the cell discharge termination voltage, then stand for 5 minutes.
  • the total charging capacity of the negative electrode sheet refers to the amount of lithium ions that the negative electrode electrode sheet can accept, and the unit is mAh or Ah.
  • the total charging capacity of the negative pole piece of the first battery cell and the total charging capacity of the negative pole piece of the second battery cell can be obtained by testing methods known in the art. As an example, the following methods can be used to test:
  • the negative pole piece is provided with one side of the negative electrode film layer and the lithium piece as the counter electrode, and the coin cell half-cell is assembled;
  • the test voltage is 0.05-2.0V, the test temperature is 25°C, the charge/discharge rate is 0.1C, and no less than 10 parallel samples are taken.
  • the total charging capacity of the negative pole piece the charging capacity of the negative pole piece per unit area ⁇ the total area of the negative pole piece in the battery cell. It is the sum of the area of the negative electrode film layer participating in the charge-discharge reaction on the upper and lower surfaces of the negative electrode pole piece (usually, the area of the negative electrode film film participating in the charge-discharge reaction in the secondary battery is equal to the total area of the positive electrode film region).
  • the first type of battery and the second type of battery are both lithium-ion batteries, the first type of battery and the second type of battery are in the same SOH and SOC state, the said When the ratio of the total charging capacity of the first negative pole piece of the first battery cell to the total charging capacity of the second negative pole piece of the second battery cell is within the above range, the first type of battery cell and the The negative pole pieces of the second type of cells have the same ability to intercalate lithium ions (the amount of lithium ions that can be intercalated), so that the life decay rates of cells of different types of chemical systems during series use are basically the same, thereby significantly improving The overall cycle life of the battery pack.
  • the state of health (SOH) of the first battery cell is the same as the SOH of the second battery cell
  • the state of charge (SOC) of the first battery cell is the same as that of the second battery cell.
  • the ratio of the total charging capacity of the first negative pole piece to the total charging capacity of the second negative pole piece is 0.9 to 1.1.
  • the first battery can be further improved.
  • the ability of lithium ions (the amount of lithium ions that can be inserted) of the negative pole pieces of the second-type cell and the second-type cell is consistent, so that the life decay rate of cells of different types of chemical systems can be consistent during series use. , thereby further improving the overall cycle life of the battery pack.
  • the first negative pole piece and the second negative pole piece also satisfy at least one of the following conditions:
  • the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05;
  • the ratio of the coating mass per unit area of the first negative pole piece to the coating mass per unit area of the second negative pole piece is 0.85 to 1.15, optionally 0.95 to 1.05;
  • the ratio of the porosity of the first negative pole piece to the porosity of the second negative pole piece is 0.8 to 1.25, optionally 0.9 to 1.1.
  • the compaction density of the negative electrode sheet refers to the density of the negative electrode film layer on one side surface of the negative electrode current collector.
  • the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is further controlled within the above range, it can ensure that the first cell and the second cell have good kinetics And there are fewer side reactions on the surface of the negative electrode, thereby further improving the kinetic performance and cycle life of the battery pack.
  • the compaction density of the first negative pole piece and the compaction density of the second negative pole piece are each independently 1.0 g/cm 3 to 1.9 g/cm 3 .
  • 1.2 g/cm 3 to 1.8 g/cm 3 are optionally 1.0 g/cm 3 to 1.9 g/cm 3 .
  • the compaction density of the negative pole piece can be measured by a method known in the art.
  • the coating mass per unit area of the negative electrode sheet refers to the mass of the negative electrode film layer provided on the surface of one side of the negative electrode current collector per unit area.
  • the ratio of the coating mass per unit area of the first negative pole piece to the coating mass per unit area of the second negative pole piece is further controlled to be within the above range, since the amount of the negative electrode graphite is equivalent, the amount of lithium ions that can be embedded will be reduced.
  • the number of active sites is the same, the consumption rate of lithium ion film formation and the loss rate of active material are similar, and the aging rate of the battery cell is relatively close, so the consistency of the overall performance of the battery pack can be further improved.
  • the coating mass per unit area of the first negative pole piece and the coating mass per unit area of the second negative pole piece are each independently 6 mg/cm 2 to 17 mg/cm 2 .
  • 8 mg/cm 2 to 14 mg/cm 2 are optionally 8 mg/cm 2 to 14 mg/cm 2 .
  • the coating quality per unit area of the negative pole piece can be measured by a method known in the art. As an example, the following methods can be used to test:
  • the active material layer on one side can be wiped off first), cut into small discs with an area of S1, weigh the small discs, and record their mass as M1;
  • the porosity of the negative electrode sheet refers to the ratio of the void volume to the total volume of the negative electrode electrode sheet in the negative electrode electrode sheet with the negative electrode film layer on both the upper and lower surfaces of the negative electrode current collector.
  • the ratio of the porosity of the first negative pole piece to the porosity of the second negative pole piece is further controlled to be within the above range, since the kinetic performance of the negative pole piece is equivalent and the degree of side reactions is equivalent, the electrical The charging, rate and power performance between the cores are consistent, and at the same time, a better life performance matching can be achieved.
  • the porosity of the first negative pole piece and the porosity of the second negative pole piece are each independently 15% to 35%. Optionally 20% to 30%.
  • the porosity of the negative pole piece refers to the ratio of the pore volume in the pole piece to the total volume, which can be obtained by testing by methods known in the art.
  • the following method can be used to conduct the test: for example, the AccuPyc II 1340 automatic true density tester of Micromeritics Company of the United States is used, and the test is carried out with reference to the national standard GB/T 24586-2009.
  • the specific test steps are as follows: let the cell stand at 25°C for 30 minutes; discharge it with a constant current of 0.33C to the discharge termination voltage of the cell, and then let it stand for 30 minutes; then disassemble the cell and take out the negative pole piece; soak in DMC The pole piece is 20 hours, and the DMC is replaced once during this period, and the drying room is dried for > 2 hours until it is completely dry; punch > 30 small rounds with a diameter of 14mm with a punching machine.
  • the negative active material of the first negative electrode and the negative active material of the second negative electrode can be independently selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon One or more of base materials, tin-based materials, and lithium titanate.
  • the negative active material of the first negative electrode and the negative active material of the second negative electrode have the same gram capacity.
  • the negative electrode active material of the first negative electrode and the negative active material of the second negative electrode have the same composition
  • the negative electrodes of the first type of battery cell and the second type of battery cell can be better
  • the ability of the chip to intercalate lithium ions is consistent, so that the life decay rates of cells of different types of chemical systems during series use are basically the same, thereby significantly improving the overall cycle life of the battery pack.
  • the ratio of the rated capacity of the first type of cells to the rated capacity of the second type of cells is 0.8 to 1.2.
  • 0.9 to 1.1 the ratio of the rated capacity of the first type of cells to the rated capacity of the second type of cells.
  • the rated capacity of the first cell and the rated capacity of the second cell can be obtained by testing methods known in the art, or the cell, or the battery module to which the cell belongs, or the battery to which the cell belongs.
  • the capacity of the battery cells identified in the GBT certification document of the package shall prevail.
  • the ratio of the number of the first type of cells to the number of the second type of cells is 0.1 to 50, optionally 1 to 30.
  • the first type of battery cells and the second type of battery cells are electrically connected, so as to output electric energy externally or store electric energy with required voltage and current.
  • the first type of battery cells and the second type of battery cells may be electrically connected in series or in a series/parallel combination.
  • the first type of battery cell and the second type of battery cell can be charged/discharged synchronously, which facilitates the realization of different types of batteries in the battery pack.
  • the capacity fading characteristics of the cells in the chemical system remain consistent, which is conducive to achieving a long cycle life of the battery pack.
  • the first type of battery cell and the second type of battery cell are electrically connected in series.
  • the electrical connection manner of the first type of cells and the second type of cells further includes parallel connection.
  • the parallel connection of the first type of batteries and the second type of batteries may be that a plurality of first type of batteries and the second type of batteries are connected in series to form sub-modules, and then on this basis, the same Two or more sub-modules of the total voltage are connected in parallel. This can further improve the external output current of the battery pack.
  • Another aspect of the present application provides a method for manufacturing a battery pack, which includes the steps of: obtaining a first type of battery cell and a second type of battery cell, wherein the first type of battery cell and the second type of battery cell are of different chemical systems batteries, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, and N and M are positive integers;
  • the first negative electrode of the first cell is The ratio of the total charging capacity of the sheet to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2; the first type of cell and the second type of cell are electrically connected in a manner including a series connection , to form the battery pack as described above.
  • the battery pack using the manufacturing method of the present application can ensure that the life decay rates of cells of different chemical systems during long-term use are as close as possible, thereby avoiding the short life of certain types of cells in the hybrid series module, and significantly improving the module. the overall cycle life.
  • the technical features of the battery pack in the present application are also applicable to the manufacturing method of the battery pack, and produce corresponding beneficial effects.
  • Both the first type of cells and the second type of cells can be obtained commercially or prepared by methods known in the art.
  • the positive pole piece, the separator and the negative pole piece can be formed by a stacking process or a winding process to form a battery cell; the battery cell is put into an outer package, injected with an electrolyte, and after encapsulation and other subsequent processes, a battery is obtained. monomer.
  • the positive electrode sheet can be prepared according to conventional methods in the art.
  • the positive electrode active material, the conductive agent and the binder are dispersed in a solvent to form a uniform positive electrode slurry, such as N-methylpyrrolidone (NMP); the positive electrode slurry is coated on the positive electrode current collector, and the After drying, cold pressing and other processes, a positive electrode sheet is obtained.
  • NMP N-methylpyrrolidone
  • the negative pole piece can be prepared according to conventional methods in the art.
  • the negative electrode active material, conductive agent, binder and thickener are dispersed in a solvent to form a uniform negative electrode slurry, the solvent is deionized water, for example; the negative electrode slurry is coated on the negative electrode current collector, and dried After drying, cold pressing and other processes, a negative electrode piece is obtained.
  • a manufacturing equipment for a battery pack including: a clamping arm unit, the clamping arm unit is used to obtain a first type of battery cell and a second type of battery cell, the first type of battery cell and the second type of battery cell.
  • Class cells are cells of different chemical systems, the first type of cells includes N first cells, the second type of cells includes M second cells, and N and M are positive integers;
  • SOH of the first cell is the same as the SOH of the second cell, and the state of charge SOC of the first cell is the same as the SOC of the second cell, the first cell
  • the ratio of the total charging capacity of the first negative pole piece of a cell to the total charging capacity of the second negative pole piece of the second cell is 0.8 to 1.2;
  • a type of battery cell and the second type of battery cell are electrically connected in a manner including series connection to form a battery pack as described above; and a control unit for controlling the clamping arm unit and the assembling unit .
  • a battery pack which includes any one or several battery packs of the present application.
  • the number of battery packs contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack may further include auxiliary components such as a battery management system module (BMS) and cooling/heating components.
  • BMS battery management system module
  • the battery pack includes more than two battery packs, each battery pack being a battery pack as described herein.
  • the battery pack has high safety, and at the same time, the capacity decay trend of the cells of different chemical systems is basically the same, so its cycle life can be significantly improved.
  • the battery pack 1 may include a battery case and a plurality of battery packs 4 provided in the battery case.
  • the battery box includes an upper box body 2 and a lower box body 3 .
  • the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery pack 4 .
  • the plurality of battery packs 4 can be arranged in the battery case in any manner.
  • the battery pack or battery pack can be used as a power source for an electrical device to provide power to the electrical device; it can also be used as an energy storage unit for the electrical device.
  • the electrical device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric vehicles, etc.) Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electrical device may select an electrochemical device, such as a battery pack or a battery pack, according to its usage requirements.
  • FIG. 8 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • the electrical device can use a battery pack or a battery module.
  • the positive electrode material, the conductive carbon Super P, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of N-methylpyrrolidone (abbreviated as NMP) solvent at a weight ratio of 95:3:2 to form a Uniform and stable slurry with a viscosity of 10000mPa ⁇ s, the slurry does not gel, stratify or settle within 24 hours of standing.
  • NMP N-methylpyrrolidone
  • the positive electrode material slurry is uniformly coated on the Al foil of the positive electrode current collector, and after drying, the polar piece is cold-pressed to a design compaction, and divided into strips for use to obtain a positive electrode polar piece.
  • Negative active materials such as graphite and conductive carbon, binder polystyrene butadiene copolymer (SBR), thickener sodium carboxymethyl cellulose (CMC) in an appropriate weight ratio of 95:2:2:1.
  • SBR binder polystyrene butadiene copolymer
  • CMC thickener sodium carboxymethyl cellulose
  • the positive electrode, separator and negative electrode are wound together to form a bare cell, then placed in the battery case, injected with electrolyte, followed by chemical formation, sealing and other processes, and finally obtained Rechargeable power cells.
  • the battery pack is a first-type cell and a second-type cell that are electrically connected in series, the first-type cell and the second-type cell are cells of different chemical systems, and the first-type cell includes 6 A first cell, the second type of cell includes three second cells, which are arranged in the manner of BAAAAAAAB (A represents the first cell, and B represents the second cell).
  • the discharge capacity measured from step 3) to step 4) is recorded as Capx.
  • the percentage of Capx to the rated capacity C is the SOH.
  • the negative pole piece is provided with one side of the negative electrode film layer and the lithium piece as the counter electrode, and the coin cell half-cell is assembled;
  • the test voltage is 0.05-2.0V, the test temperature is 25°C, the charge/discharge rate is 0.1C, and no less than 10 parallel samples are taken.
  • the total charging capacity of the negative pole piece the charging capacity of the negative pole piece per unit area ⁇ the total area of the negative pole piece in the battery cell. It is the sum of the area of the negative electrode film layer participating in the charge-discharge reaction on the upper and lower surfaces of the negative electrode pole piece (usually, the area of the negative electrode film film participating in the charge-discharge reaction in the secondary battery is equal to the total area of the positive electrode film region).
  • the battery to be tested use the battery charger and discharge machine and the high and low temperature box to test the standard rate full charge capacity and discharge capacity of the battery at 25°C, and the discharge capacity is the capacity of the battery.
  • the charging and discharging rate is 0.33C (C represents the rated capacity of the battery cell.
  • the charging/discharging current is the rate multiplied by the rated capacity of the battery cell, and the rated capacity is based on the battery cell capacity identified in the GBT certification document of the battery cell. ).
  • the test process for the capacity of the cell is as follows: 1) stand at 25°C for 30 minutes; 2) 0.33C constant current discharge to the discharge termination voltage (for example, the NCM chemical system cell is set to 2.8V, the LFP chemical system is set to 2.8V The battery is set to 2.5V), and then let stand for 30 minutes; 3) 0.33C constant current charging to the end-of-charge voltage (for example, the NCM chemical system battery is set to 4.2V, 4.25V, 4.3V according to the specific battery type , 4.35V, 4.4V, 4.45V, etc., the LFP chemical system cell is generally 3.65V, and the charging termination voltage of the cell is recognized as the industry's well-known information), constant voltage charging to the current ⁇ 0.05C, and then let stand for 5 minutes; 4 )0.33C constant current discharge to discharge termination voltage.
  • 0.33C constant current discharge to the discharge termination voltage for example, the NCM chemical system cell is set to 2.8V, the LFP chemical system is set to 2.8V The battery is set to 2.5V
  • the measured discharge capacity is the capacity value of the cell.
  • relevant terms and test methods refer to GB/T 19596, GB/T 31484-2015, GB/T 31485-2015, GB/T 31486-2015 and "Safety Requirements for Power Batteries for Electric Vehicles".
  • Steps 1) to 4) are one charge-discharge cycle for the battery pack.
  • Comparative Example 1 the ratio of the total charge capacity of the first negative electrode piece to the total charge capacity of the second negative electrode piece is 0.78, that is, less than 0.8 (not within the range of 0.8 to 1.2) and other conditions Under exactly the same conditions, the capacity retention rate of the battery pack at the 1000th cycle was significantly lower than that of Examples 1 and 2.
  • Comparative Example 2 when the ratio of the total charge capacity of the first negative electrode piece to the total charge capacity of the second negative electrode piece is 1.3, that is, exceeds 1.2 (not within the range of 0.8 to 1.2) and other conditions are exactly the same, Compared with Examples 1 and 2, the capacity retention rate of the battery pack at the 1000th cycle also decreased significantly.
  • the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.85 to 1.15.
  • the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.95 to 1.05.
  • both the density of the first negative pole piece and the density of the second negative pole piece are in the range of 1.0 g/cm 3 to 1.9 g/cm 3 .
  • both the density of the first negative pole piece and the density of the second negative pole piece are in the range of 1.2 g/cm 3 to 1.8 g/cm 3 .
  • the inventors of the present application have found through intensive research that: when the compaction density of the negative pole piece is within an appropriate range, the porosity of the negative pole piece is moderate, thereby improving the interface side reaction between the negative pole piece and the electrolyte, inhibiting the The consumption of electrolyte and negative electrode active layer material can effectively improve the cycle life of the battery cell; and since the total volume of pores to be filled in the negative electrode plate is moderate, there is no need to use too much electrolyte, which is conducive to improving the battery core. energy density.
  • the life decay rate of the two types of cells during use can be basically Consistent, can significantly improve the overall life and overall performance of the battery pack.
  • the compacted density can be tested using methods known in the art.
  • An exemplary test method for the compaction density of the negative film layer is as follows: take the negative pole piece coated on one side and after cold pressing (if it is a pole piece coated on both sides, the negative film layer on one side can be wiped off first), Punch out a small disc with an area of S1, weigh its weight, and denote it as M1; test the thickness of the negative electrode film layer, denoted as H; then wipe off the negative electrode film layer, and weigh the weight of the negative electrode current collector, denoted as M2;
  • the battery packs of the following Examples 3 to 10 can be obtained by the above-mentioned "Cell Preparation" method.
  • the compaction densities of the negative electrode pieces of the first type of cells are the same as each other, but the compaction densities of the negative electrode pieces of the second type of cells are different from each other.
  • the ratio of the compaction density of the negative pole pieces of the first type of cells to the compaction density of the negative pole pieces of the second type of cells is the same, but the ratio of the compaction density of the negative pole pieces of the first type of cells
  • the compaction densities of the sheets are different from each other, and the compaction densities of the negative pole sheets of the second type of cells are different from each other.
  • the ratio of the compaction density of the first negative pole piece to the compaction density of the second negative pole piece is 0.82 or 1.18, that is, less than 0.85 or greater than 1.15 (not within the range of 0.85 to 1.15) and other
  • the capacity retention rate of the battery pack at the 1000th cycle is lower than that of Examples 3 and 4.
  • the compaction density of the first negative pole piece (the compaction density of the second negative pole piece) is 0.95 or 1.95, that is, less than 1 or more than 1.9 (not within the range of 1 to 1.9) and other conditions
  • the capacity retention rate of the battery pack at the 1000th cycle was lower than that of Examples 7 and 8.
  • the ratio of the coating mass per unit area of the negative electrode active material of the first negative electrode pole piece to the coating mass per unit area of the negative electrode active material of the second negative electrode pole piece is 0.85 to 1.15;
  • the ratio of the coating mass per unit area of the negative active material of the first negative pole piece to the coating mass per unit area of the negative active material of the second negative pole piece is 0.95 to 1.05;
  • the coating mass per unit area of the negative active material of the first negative pole piece and the coating mass per unit area of the negative active material of the second negative pole piece are both in the range of 6 mg/cm 2 to 17 mg/cm 2 ;
  • the coating mass per unit area of the negative active material of the first negative pole piece and the coating mass per unit area of the negative active material of the second negative pole piece are both 8 mg/cm 2 to 14 mg/cm 2 . In the range.
  • the inventors of the present application have found through intensive research that the coating quality of the active material layer of the negative electrode pole piece needs to be controlled within an appropriate range.
  • the material layer is polarized to improve the power performance of the cell; on the other hand, it can ensure the high energy density of the cell and the module, and reduce the manufacturing cost of the cell per watt-hour.
  • the coating mass per unit area of the negative electrode active material of the first negative electrode pole piece as much as possible to be consistent with the coating mass per unit area of the negative electrode active material of the second negative electrode pole piece, it is possible to make the two
  • the life-span decay rate of these batteries is basically the same during use, which can further improve the overall life and comprehensive performance of the battery pack.
  • Example 11 Regarding the preparation of the cells, a method similar to the "Preparation of Cells" in the above-mentioned Example 1 was adopted, except that the coating mass per unit area of the negative electrode active material was changed to the values shown in the following Examples 11 to 18.
  • the battery packs of the following Examples 11 to 18 can be obtained by the above-mentioned "Cell Preparation" method.
  • the coating mass per unit area of the negative active material of the negative electrode sheet of the first type of cell is the same, but the coating mass per unit area of the negative active material of the negative electrode sheet of the second type of cell is the same. The qualities are different from each other.
  • the ratios are the same, but the coating mass per unit area of the negative electrode active material of the negative electrode sheet of the first type of cell is different from each other, and the coating mass per unit area of the negative electrode active material of the negative electrode sheet of the second type of cell is different from each other.
  • the ratio of the coating mass per unit area of the negative active material of the first negative electrode sheet to the coating mass per unit area of the negative active material of the second negative electrode sheet is 0.83 or 1.18, that is, less than 0.85 or greater than 1.15 (outside the range of 0.85 to 1.15) and other conditions are exactly the same (Examples 13 and 14), the capacity retention rate of the battery pack at the 1000th cycle is lower than that of Examples 11 and 12.
  • Embodiments 11 and 12 of the present application can improve the capacity retention rate of the battery pack at the 1000th cycle, and can significantly improve the overall life and comprehensive performance of the battery pack.
  • the coating mass per unit area of the negative active material of the first negative electrode sheet (the coating mass per unit area of the negative active material of the second negative electrode sheet) is 5.5 or 17.5, that is, less than 6.0 or greater than 17.0 (Examples 17 and 18) (Examples 17 and 18) (not within the range of 6.0 to 17.0), the capacity retention rate of the battery pack at the 1000th cycle was lower than that of Examples 15 and 16.
  • the 1000th cycle capacity retention rate of the battery pack can be improved, and the overall life and comprehensive performance of the battery pack can be further improved.
  • the positive pole pieces of the first type of cells are all LiFePO 4 , but the positive pole pieces of the first type of cells can also be made of other materials, such as LiMn 0.5 Fe 0.5 PO 4 , LiMn 0.6 Fe 0.4 PO 4 , LiMn 0.7 Fe 0.3 PO 4 , Na 3 V 2 (PO 4 ) 2 O 2 F, LiFe 0.998 Ti 0.002 PO 4 , LiFe 0.995 Ti 0.005 PO 4 .
  • Table 6 shows Examples 19 to 25 when the positive electrode pieces of the first-type battery cells or the second-type battery cells are made of different materials.
  • Example 24 the positive pole piece of the first type of cell is LiFe 0.995 Ti 0.005 PO 4 and the positive pole piece of the second type of cell is LiNi 0.70 Co 0.065 Mn 0.24 Ti 0.003 W 0.002 O2
  • the 1000th cycle capacity retention rate of the module is 96% and 98% respectively, showing the most excellent cycle life.

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Abstract

本申请涉及一种电池组，该电池组包括至少以串联连接的第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括N个第一电芯，所述第二类电芯包括M个第二电芯，N和M为正整数；在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2。

Description

电池组、电池包、电学装置以及电池组的制造方法及制造设备 技术领域
本申请涉及储能器件技术领域，尤其涉及一种电池组、电池包、电学装置以及电池组的制造方法和电池组的制造设备。
背景技术
二次电池具有体积小、能量密度高、功率密度高、循环使用次数多和存储时间长等优点，在一些电子设备、电动交通工具、电动玩具和电动设备上应用广泛，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等。二次电池作为新能源汽车的动力驱动电源或储能电站的大容量存储单元，通常需要将多个单体电芯进行串、并联，得到具有较高体积能量密度的电池组、电池包。
为了提高成组后二次电池的安全性，提出了将多个不同化学体系的单体电芯进行串联和/或并联以形成电池组的技术方案，其中一类电芯例如为具有高能量密度的含锂镍钴锰酸锂金属氧化物的三元电芯，另一类电芯例如为具有较高安全性的磷酸铁锂电芯。然而，对于化学体系不同的单体电芯，其容量衰减特性、循环过程的充放电特性等均具有显著差异，将不同电化学特性的电芯串联成电池组后，由于短板效应，电池组的长期循环性能往往受限于循环性能更差的单体电芯，造成电池组部分电芯很难充分发挥其电性能优势。
因此，如何匹配电池组中不同化学体系的单体电芯，以实现电池组的长期循环性能，是二次电池领域一项急需解决的技术问题。
发明内容
对于混合串联电芯的关键技术，现有技术仅仅停留在概念层面，对于不同化学体系电芯的如何进行匹配并没有具体的实施方案说明。特别是，现有技术中，对于将多种电芯混合串联所形成的电池组的容量特性、循环寿命等指标没有任何记载和披露。
本申请是鉴于现有技术中存在的上述问题而完成的，其目的在于，提供一种电池组，通过对不同化学体系的电芯的负极极片的总充电容量进行匹配，对电池组中不同化学体系电芯的容量设计进行优化，从而实现混合串联模组的长循环使用寿命。
本申请的第一方面提供一种电池组，该电池组包括至少以串联连接的第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括N个第一电芯，所述第二类电芯包括M个第二电芯，N和M为正整数；在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2。
可选的，在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一负极极片的总充电容量与所述第二负极极片的总充电容量之比为0.9至1.1。
可选的，所述第一负极极片的放电容量与所述第二负极极片的放电容量之比为0.8至1.2。可选的，所述第一负极极片的放电容量与所述第二负极极片的放电容量之比为0.9至1.1。
可选的，所述第一类电芯的额定容量与所述第二类电芯的额定容量之比为0.8至1.2，可选地为0.9至1.1。
可选的，所述第一负极极片与所述第二负极极片还至少满足以下条件之一：(1)所述第一负极极片的压实密度与所述第二负极极片的压实密度之比为0.85至1.15，可选地为0.95至1.05；(2)所述第一负极极片的单位面积涂布质量与所述第二负极极片的单位面积涂布质量之比为0.85至1.15，可选地为0.95至1.05；(3)所述第一负极极片的孔隙率与所述第二负极极片的孔隙率之比为0.8至1.25，可选地为0.9至1.1。
可选的，所述第一负极极片的密度和所述第二负极极片的密度各自独立地为1.0g/cm 3至1.9g/cm 3，可选地为1.2g/cm 3至1.8g/cm 3。
可选的，所述第一负极极片的单位面积涂布质量和所述第二负极极片的单位面积涂布质量各自独立地为6mg/cm 2至17mg/cm 2，可选地为8mg/cm 2至14mg/cm 2。
可选的，所述第一负极极片的孔隙率和所述第二负极极片的孔隙率各自独立 地为15％至35％，可选地为20％至30％。
可选的，所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质可以独立地选自人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种；可选地，所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质的组分相同。
可选的，所述第一类电芯的数量与所述第二类电芯的数量之比为0.1至50，可选地为2至10。
本申请的第二方面提供一种电池包，包括上述第一方面所述的电池组。
本申请的第三方面提供一种电学装置，包括上述第一方面所述的电池组或上述第二方面所述的电池包，且以所述电池组或所述电池包作为所述用电装置的电源或者能量存储单元。
本申请的第四方面提供一种电池组的制造方法，包括如下步骤：获取第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括N个第一电芯，所述第二类电芯包括M个第二电芯，N和M为正整数；在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2；将所述第一类电芯和第二类电芯以包括串联的方式电连接，以形成上述第一方面所述的电池组。
本申请的第五方面提供一种电池组的制造设备，其中，包括：夹臂单元，所述夹臂单元用于获取第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括N个第一电芯，所述第二类电芯包括M个第二电芯，N和M为正整数；在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2；组装单元，所述组装单元用于将所述第一类电芯和所述第二类电芯以包括串联的方式进行电连接，以形成上述第一方面所述的电池组；以及控制单元，所述控制单元用于控制所述夹臂单元和所述组装单元。
[技术效果]
本申请中，电池组包括至少以串联连接具有不同化学体系的第一类电芯和第二 类电芯，本申请中对电池组中第一类电芯和第二类电芯的负极极片的总充电容量设定在特定范围内，保证不同化学体系电芯在长期使用过程中的寿命衰减速率尽量接近，从而避免了混合串联模组中某类电芯的寿命短板，显著提升了模组的整体循环使用寿命。
由于本申请中的电池包和电学装置包括所述电池组，因而至少具有与所述电池组相同的技术优势。
附图说明
图1是示出本申请的电芯的一个示例的示意图。
图2是示出图1所示的本申请的电芯的一个示例的分解图。
图3是示出本申请的电池组的一个示例的示意图。
图4是示出本申请的电池包的一个示例的示意图。
图5是示出图4所示的本申请的电池包的一个示例的分解图。
图6是示出将本申请的电池组用作电源的电学装置的一个示例的示意图。
标号说明
5、5a、5b  电芯
51  壳体
52  电极组件
53  盖板
4  电池组
1  电池包
2  上箱体
3  下箱体
具体实施方式
本文所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出 的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
在本申请中，如果没有特别的说明，本文所提到的所有实施方式以及优选实施方式可以相互组合形成新的技术方案。
在本申请中，如果没有特别的说明，本文所提到的所有技术特征以及优选特征可以相互组合形成新的技术方案。
在本申请中，如果没有特别的说明，本文所提到的所有步骤可以顺序进行，也可以随机进行，但是优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
在本申请中，如果没有特别的说明，本文所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种及两种以上。
在本文的描述中，除非另有说明，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
[电芯]
本申请中，“电芯”是指能够独立进行充放电的电池单体。电芯的组成构件可以包括正极极片、负极极片、隔膜、电解液以及用于封装正极极片、负极极片、隔膜和电解液的外包装等。本申请对电芯的类型、形状没有特别的限制，其可以是软包电芯，也可以是柱形电芯、或是方形电芯等各类电芯。本申请中的电芯可以是锂 离子电芯、钾离子电芯、钠离子电芯、锂硫电芯等，特别优选是锂离子电芯。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解液在正极极片和负极极片之间起到传导离子的作用。
本申请中，电芯的“化学体系”是按照电芯中正极极片所使用的正极活性材料的组分进行划分，对正极活性材料的掺杂或包覆的元素或物质不作限定。例如，正极活性材料为磷酸铁锂(包括经Mn或V元素掺杂)的电芯均可以定义为磷酸铁锂化学体系电芯。正极活性材料为镍钴锰酸锂(一般简称NCM)的电芯可以定义为NCM化学体系电芯。进一步地，可以依据正极活性材料中镍、钴、锰元素的相对含量，对电芯化学体系进一步限定，如，正极活性材料为LiNi 0.5Co 0.2Mn 0.3O 2(一般简称NCM523)的电芯可以定义为NCM523化学体系电芯，正极活性材料为LiNi 0.6Co 0.2Mn 0.2O 2(一般简称NCM622)的电芯可以定义为NCM622化学体系电芯,正极活性材料为LiNi 0.8Co 0.1Mn 0.1O 2(一般简称NCM811)的电芯可以定义为NCM811化学体系电芯。镍钴铝酸锂体系电芯(一般称NCA)为正极材料的电芯可以定义为NCA化学体系电芯。此外，本申请中，也可采用混合体系电芯，例如包括NCM和NCA的混合体系电芯。
下面，首先对本申请中的电芯所具备的负极极片、正极极片、电解液、隔膜的基本结构进行说明。
<负极极片>
本申请的电芯中包括负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层，所述负极膜层包含负极活性材料。
在本申请的一个实施方式中，负极膜层的负极活性材料，可以包括常用负极活性材料，例如，天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。所述硅基材料可选自单质硅、硅氧化物、硅碳复合物中的一种或几种。所述锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或几种。
本申请的电芯中，所述负极膜片包含负极活性材料以及可选的粘结剂、可选的导电剂和其他可选助剂，通常是由负极浆料涂布干燥而成的。负极浆料通常是将负极活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
作为示例，导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
作为示例，粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或几种。作为示例，粘结剂可包括丁苯橡胶(SBR)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或几种。其他可选助剂例如是增稠剂(如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
另外，本申请的电芯中，负极极片并不排除除了负极膜层之外的其他附加功能层。例如在某些实施方式中，本申请的负极极片还可包括夹在负极集流体和第一负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还可包括覆盖在第二负极膜层表面的覆盖保护层。
本申请的电芯中，所述负极集流体可以是金属箔片或复合集流体，例如金属箔片可以是铜箔、银箔、铁箔、或者上述金属的合金构成的箔片。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层，可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基层(如聚丙烯PP、聚对苯二甲酸乙二醇酯PET、聚对苯二甲酸丁二醇酯PBT、聚苯乙烯PS、聚乙烯PE及其共聚物等材料制成的基层)上而形成。
<正极极片>
本申请的电芯中，正极极片包括正极集流体以及设置在正极集流体至少一个表面且包括正极活性材料的正极膜层。例如，正极集流体具有在自身厚度方向相背的两个表面，正极膜层设置于正极集流体的两个相背表面中的任意一者或两者上。本申请的电芯中，所述正极集流体可以是金属箔片或复合集流体，例如所述金属箔片可以是铝箔，而所述复合集流体可包括高分子材料基层和形成于该高分子材料基层至少一个表面上的金属层。所述复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯PP、聚对苯二甲酸乙二醇酯PET、聚对苯二甲酸丁二醇酯PBT、聚苯乙烯PS、聚乙烯PE及其共聚物等的基材)上而形成。
在本申请的电芯中，所述正极活性材料可采用本领域公知的用于电芯的正极活性材料。例如，该正极活性材料可包括以下的一种或多种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还 可以使用其他可被用作电芯正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811))、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的一种或几种。
在一些实施方式中，正极膜层还可选地包括粘结剂。可用于正极膜层的粘结剂的非限制性例子可以包括以下的一种或多种：聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂。
在一些实施方式中，正极膜层还可任选地包含导电剂。用于正极膜层的导电剂的例子可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或几种。
在本申请的一个实施方式中，可以通过以下方式制备正极：将上述用于制备正极的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成均匀的正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
<电解液>
电解液在正极极片和负极极片之间起到传导离子的作用。所述电解液包括电解质盐和溶剂。在一些实施方式中，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
在本申请的一个实施方式中，溶剂可选自以下的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、 碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)。
在本申请的一个实施方式中，以所述电解液的总重量为基准计，所述溶剂的含量为60-99重量％，例如65-95重量％，或者70-90重量％，或者75-89重量％，或者80-85重量％。在本申请的一个实施方式中，以所述电解液的总重量为基准计，所述电解质的含量为1-40重量％，例如5-35重量％，或者10-30重量％，或者11-25重量％，或者15-20重量％。
在本申请的一个实施方式中，所述电解液中还可任选地包含添加剂。例如添加剂可以包括以下的一种或多种：负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
<隔离膜>
在本申请的一个实施方式中，所述电芯还包括隔离膜，隔离膜将电芯的阳极侧与阴极侧隔开，对体系内不同种类、尺寸和电荷的物质提供选择性透过或阻隔，例如隔离膜可以对电子绝缘，将电芯的正负极活性物质物理隔离，防止内部发生短路并形成一定方向的电场，同时使得电池中的离子能够穿过隔离膜在正负极之间移动。
在本申请的一个实施方式中，用来制备隔离膜的材料可包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料可以相同或不同。
在本申请的一个实施方式中，上述正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件/裸电芯。
在本申请的一个实施方式中，电芯可包括外包装，该外包装可用于封装上述电极组件及电解液。在一些实施方式中，电芯的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。在另一些实施方式中，所述电芯的外包装可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
图1是示出本申请的电芯5的一个示例的示意图。图2是示出图1所示的本申请的电芯5的一个示例的分解图。
所述外包装可包括壳体51和盖板53，壳体51可包括底板和连接于底板上的侧板，所述底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52，该电极组件封装于所述容纳腔中，所述电解液浸润于电极组件52中。电芯5所含电极组件52的数量可以为一个或多个。
[电池组]
本申请中，“电池组”是为了保护电芯免受外部冲击、热、振动等影响，将一定数目的电芯电连接在一起并放入一个框架中而形成的。本申请的电芯的形状可以是圆柱形、方形或其他任意的形状。
本申请中，可以将若干个电芯组装在一起以构成电池组，电池组中包含两个或更多个电芯，具体数量取决于电池组的应用和单个电池组的参数。
图3是示出本申请的电池组的一个示例的示意图。参照图3，在电池组4中，多个电芯5a、5b可以是沿电池组4的长度方向依次排列设置(其中5a可以为第一电芯，5b可以为第二电芯)。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电芯5a、5b进行固定。可选地，电池组4还可以包括具有容纳空间的外壳，多个组5a、5b容纳于该容纳空间。
<关于第一类电芯与第二类电芯的设计>
本申请中，电池组包括至少以串联连接的第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括N个电芯，所述第一类电芯包括第一电芯；所述第二类电芯包括M个电芯，所述第二类电芯包括第二电芯；N和M为正整数；在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2。
其中，“SOH”表示健康状态(State of Health)，其是指当前电芯的总容量与该电芯的初始总容量的比值。例如可以为100％、98％、95％、90％、85％、80％、75％、70％。“SOC”表示荷电状态(State Of Charge)，其是指当前电芯的剩余电量与相同条件下额定容量的比值，例如可以为100％、99％、90％、80％、70％、60％、 50％、40％、30％、20％、10％、0％。
应当理解的是，由于测试的精度及不可避免的测试误差，本申请中“第一电芯的健康状态SOH与第二电芯的SOH相同”所指的范围是第一电芯的健康状态SOH与第二电芯的SOH的差值的绝对值与二者的平均值的比值不超过5％。同理，“第一电芯的荷电状态SOC与第二电芯的SOC相同”所指的范围是第一电芯的荷电状态SOC与第二电芯的SOC的差值的绝对值与二者的平均值的比值不超过5％。
(关于SOH的测试)
本申请中，第一电芯的SOH以及第二电芯的SOH可采用本领域公知的方法测试得到。作为示例的，可以采用如下方法进行测试：
参考GB/T 31484-2015《电动汽车用动力蓄电池循环寿命要求及试验方法》测试电芯的实际容量，使用相同测试流程测得的实际容量与新鲜出厂电芯额定容量的比值为SOH。
实际容量(计为：Capx)测试步骤：
将待测电芯在25℃下静置30分钟；2)0.33C(C代表电芯额定容量。其中，充/放电电流为倍率乘以电芯额定容量，额定容量以该电芯、或该电芯所属电池模组或该电芯所属电池包的GBT认证文件中所认定的电芯容量为准)恒流放电至电芯放电终止电压，之后静置30分钟；3)0.33C恒流充电至电芯充电终止电压，恒压充电至电流<0.05C，静置5分钟；4)0.33C恒流放电至电芯放电终止电压，之后静置5分钟。由步骤3)至步骤4)测得的放电容量记为Capx。
Capx占额定容量C的百分比即为SOH。
(关于SOC的测试)
本申请中，第一电芯的SOC以及第二电芯的SOC可采用本领域公知的方法测试得到。作为示例的，可以采用如下方法进行测试：
参考GB/T 31484-2015《电动汽车用动力蓄电池循环寿命要求及试验方法》测试电芯在与额定容量测试流程相同的放电条件下可释放出的容量，该放电容量记为Capy，该容量占电芯实际容量Capx的百分比即为SOC。
本申请中，将第一电芯的SOH与第二电芯的SOH调整至相同的方法，可以采用本领域公知的方法进行。作为示例的，可以采用如下方法进行调节：
如果某一个电芯的SOH较低，则该电芯的SOH可以作为SOH较高电芯的目标SOH进行调整。调整的方法参考GB/T 31484-2015《电动汽车用动力蓄电池循环 寿命要求及试验方法》中循环寿命的测试方法直至电芯实际容量占额定容量的百分比达到目标值。
循环寿命的测试流程如下：
1)将待测电芯在25℃下静置30分钟；2)0.33C恒流放电至电芯放电终止电压，之后静置30分钟；3)0.33C恒流充电至电芯充电终止电压，恒压充电至电流<0.05C，静置5分钟；4)0.33C恒流放电至电芯放电终止电压，之后静置5分钟。
步骤3)～步骤4)为电芯一个充放电循环。
重复上述步骤3)～步骤4)n次，直至第n次的放电容量Capn＝目标SOH*额定容量。
本申请中，将第一电芯的SOC与第二电芯的SOC调整至相同的方法，可以采用本领域公知的方法进行。作为示例的，可以采用如下方法进行调节：
调节SOC的方法如下：
1)设定目标SOC，例如0％SOC；2)将待测电芯在25℃下静置30分钟；3)0.33C恒流放电至电芯放电终止电压，之后静置30分钟，电芯即达到0％SOC。如果目标SOC是x％SOC，调节SOC流程的步骤如下：1)将待测电芯在25℃下静置30分钟；2)0.33C恒流放电至电芯放电终止电压，之后静置30分钟；3)0.33C恒流充电至电芯充电终止电压，恒压充电至电流<0.05C，静置5分钟；4)0.33C恒流放电至电芯放电终止电压，之后静置5分钟。由步骤3)至步骤4)测得的放电容量记为Capx；5)0.33C恒流充电至电芯充电终止电压，恒压充电至电流<0.05C，静置5分钟；6)0.33C恒流放电至剩余容量＝x％SOC*Capx，之后静置5分钟。
(关于负极极片的总充电容量的测试)
本申请中，负极极片的总充电容量指的是负极极片可接纳锂离子的量，单位为mAh或者Ah。第一电芯的负极极片的总充电容量以及第二电芯的负极极片的总充电容量可采用本领域公知的方法测试得到。作为示例的，可以采用如下方法进行测试：
(1)极片取样要求如下：
取单面涂布且经冷压后的负极极片(若是双面涂布的极片，可先擦拭掉其中一面的负极膜层)、或者是从电芯中拆解得到的负极极片(将电芯在25℃下静置30分钟；以0.33C恒流放电至电芯放电终止电压，之后静置30分钟进行满放，然后拆解电芯，取出负极极片，若是双面涂布的极片，可先擦拭掉其中一面的负 极膜层，用DMC溶液进行适当冲洗，烘干待用)。用直尺测量负极极片的长度和宽度，负极极片的面积等于长度和宽度的乘积。负极极片取样位置为：选取距离边缘>15mm的中部任意位置；
(2)将负极极片设置有负极膜层的一侧与锂片作为对电极，组装扣电半电池；
(3)单位面积负极极片充电容量、负极极片总充电容量：
测试电压0.05-2.0V，测试温度25℃，充/放电倍率0.1C，取平行样不少于10个，分别测试扣式半电池的充电容量，去掉最低以及最高值后取平均值，得到该面积下负极极片的充电容量；将上述测试得到的负极极片的充电容量除以负极极片的面积，即可以得到单位面积负极极片充电容量；
负极极片总充电容量＝单位面积负极极片充电容量×电芯中负极膜片的总面积，其中，如果负极极片为在集流体的上下表面均有负极膜层，负极膜片的总面积为负极极片上下表面参与充放电反应的负极膜层的面积之和(通常，二次电池中参与充放电反应的负极膜片的面积等于正极膜片区的总面积)。
本申请中，例如，在第一类电芯和第二类电芯都为锂离子电池的情况下，第一类电芯和第二类电芯在相同的SOH和SOC的状态下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比在上述范围内时，可以尽可能地使第一类电芯和第二类电芯的负极极片可嵌入锂离子的能力(可嵌入锂离子量)一致，从而能够使得不同类型的化学体系的电芯在串联使用过程中的寿命衰减速率基本一致，从而显著提升电池组的整体循环使用寿命。
在本申请的一些实施方式中，在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一负极极片的总充电容量与所述第二负极极片的总充电容量之比为0.9至1.1。本申请中，当第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比在上述范围内时，可以进一步地提高第一类电芯和第二类电芯的负极极片可嵌入锂离子的能力(可嵌入锂离子量)一致，从而能够使得不同类型的化学体系的电芯在串联使用过程中的寿命衰减速率一致性，从而进一步提升电池组的整体循环使用寿命。
在本申请的一些实施方式中，所述第一负极极片与所述第二负极极片还满足至少满足以下条件之一：
(1)所述第一负极极片的压实密度与所述第二负极极片的压实密度之比为 0.85至1.15，可选地为0.95至1.05；
(2)所述第一负极极片的单位面积涂布质量与所述第二负极极片的单位面积涂布质量之比为0.85至1.15，可选地为0.95至1.05；
(3)所述第一负极极片的孔隙率与所述第二负极极片的孔隙率之比为0.8至1.25，可选地为0.9至1.1。
本申请中，负极极片的压实密度指的是在负极集流体的单侧表面上的负极膜层的密度。本申请中，当进一步控制第一负极极片的压实密度与第二负极极片的压实密度之比在上述范围内时，可以保证第一电芯及第二电芯具有良好的动力学且在负极极片表面的副反应较少，从而进一步提高电池组的动力学性能以及循环寿命。
在本申请的一些实施方式中，所述第一负极极片的压实密度和所述第二负极极片的压实密度各自独立地为1.0g/cm 3至1.9g/cm 3。可选地为1.2g/cm 3至1.8g/cm 3。
(关于压实密度的测试)
本申请中，负极极片的压实密度可以采用本领域公知的方法测试得到。作为示例的，可以采用如下方法进行测试：取单面涂布且经冷压后的负极极片(若是双面涂布的极片，可先擦拭掉其中一面的负极膜层)、或者是从电芯中拆解得到的负极极片(从电芯中拆解得到的负极极片可使用DMC进行简单冲洗，去除极片表面及内部残余的电解液或反应副产物)，冲切成面积为S1的小圆片，称其重量，记为M1；测试负极膜层的厚度，记为H；然后将负极膜层擦拭掉，称量负极集流体的重量，记为M2；负极膜层的压实密度dc＝(M1-M2)/S1/H。
本申请中，负极极片的单位面积涂布质量指的是在单位面积的负极集流体单侧表面设置的负极膜层的质量。本申请中，当进一步控制第一负极极片的单位面积涂布质量与第二负极极片的单位面积涂布质量之比在上述范围内时，由于负极石墨的用量相当，可嵌入锂离子的活性位点数量相当，锂离子成膜消耗和活性物质的损失速率相当，电芯的老化速率比较接近，因而可进一步提高电池组综合性能的一致性。
在本申请的一些实施方式中，所述第一负极极片的单位面积涂布质量和所述第二负极极片的单位面积涂布质量各自独立地为6mg/cm 2至17mg/cm 2。可选地为8mg/cm 2至14mg/cm 2。
(关于负极极片的单位面积涂布质量的测试)
本申请中，负极极片的单位面积涂布质量可以采用本领域公知的方法测试得到。作为示例的，可以采用如下方法进行测试：
将电芯在25℃下静置30分钟；以0.33C恒流放电至电芯放电终止电压，之后静置30分钟进行满放，然后拆解电芯，取待测负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的活性物质层)，冲切成面积为S1的小圆片，对小圆片进行称重，其质量记为M1；然后将负极极片置于去离子水中，使负极活性物质层与负极集流体完全剥离，称取负极集流体的质量记为M2；由此，负极极片的单位面积涂布质量可以依据公式计算得到：负极极片的单位面积涂布质量＝(M1-M2)/S1。
本申请中，负极极片的孔隙率指的是在负极集流体上、下表面均设置负极膜层的负极极片中，其空隙体积在上述负极极片总体积的占比。本申请中，当进一步控制第一负极极片的孔隙率与第二负极极片的孔隙率之比在上述范围内时，由于负极极片的动力学性能相当，且副反应程度相当，因而电芯之间的充电、倍率、功率性能一致性较好，同时可以达到较好的寿命性能匹配。
在本申请的一些实施方式中，所述第一负极极片的孔隙率和所述第二负极极片的孔隙率各自独立地为15％至35％。可选地为20％至30％。
(关于孔隙率的测试)
本申请中，负极极片的孔隙率是指极片中孔隙体积占总体积的比例，可以采用本领域公知的方法测试得到。作为示例的，可以采用如下方法进行测试：例如采用美国Micromeritics公司的AccuPyc II 1340型全自动真密度测试仪，参考国标GB/T 24586-2009进行测试。
具体测试步骤如下：将电芯在25℃下静置30分钟；以0.33C恒流放电至电芯放电终止电压，之后静置30分钟；然后拆解电芯，取出负极极片；用DMC浸泡极片20h，期间更换一次DMC，干燥房晾＞2h至完全干燥；用冲片机冲切＞30片直径为14mm小圆片，小圆片要求边缘完整，无掉粉；用万分尺测厚，每片至少1次，取均值，自封袋封装，标注厚度；利用小分子直径的惰性气体(氦气)置换法，结合阿基米德原理和玻尔定律，精确测量被测材料的真实体积；孔隙率P＝(V2-V1)/V2*100％，表观体积V2＝S*H*A，式中：S-面积，cm 2；H-厚度，cm；A-样品数，EA；V1－样品真体积，cm 3，测试得到；V2－样品表观体积，cm 3。
在本申请的一些实施方式中，所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质可以独立的选自人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。可选地，所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质的克容量相同。本申请中，当第一负极极片的负极活性物质和第二负极极片的负极活性物质物质的组分相同时，可以更好地使第一类电芯和第二类电芯的负极极片可嵌入锂离子的能力(可嵌入锂离子量)一致，从而能够使得不同类型的化学体系的电芯在串联使用过程中的寿命衰减速率基本一致，从而显著提升电池组的整体循环使用寿命。
在本申请的一些实施方式中，所述第一类电芯的额定容量与所述第二类电芯的额定容量之比为0.8至1.2。可选地为0.9至1.1。本申请中，在控制第一负极极片与第二负极极片的总充电容量关系的基础上，进一步控制第一电芯与第二电芯的额定容量在上述范围内时，由于混合串联模组中电芯容量的一致性较好，模组的容量不受单一电芯容量短板的影响，因此可以提高模组的能量吞吐量。
本申请中，第一电芯的额定容量与第二电芯的额定容量可以采用本领域公知的方法测试得到，也可以以该电芯、或该电芯所属电池模组或该电芯所属电池包的GBT认证文件中所认定的电芯容量为准。
在本申请的一些实施方式中，所述第一类电芯的数量与所述第二类电芯的数量之比为0.1至50，可选地为1至30。
在本申请的电池组中，第一类电芯和第二类电芯进行电连接，以便于以所需的电压和电流对外输出电能或进行储存电能。其中，第一类电池单体和第二类电池单体可以以串联或串/并联组合的方式电连接。在本申请中，当第一类电芯和第二类电芯至少以串联的方式电连接后，第一类电芯和第二类电芯可以同步进行充/放电，便于实现电池组中不同化学体系电芯的容量衰减特性保持一致，有利于实现电池组具有较长的循环使用寿命。在一个具体的示例中，第一类电芯和第二类电芯的电连接方式为串联连接。
在本申请的一些实施方案中，第一类电芯和第二类电芯的电连接方式还包括并联。本申请中，将第一类电芯和第二类电芯的并联，可以是多个第一类电芯与第二类电芯先进行串联形成子模块，再在此基础上，将具有相同总电压的2个以上的子模块进行并联。这样可以进一步提升电池组的对外输出电流。
[制造方法]
本申请另一方面提供一种电池组的制造方法，其包括如下步骤：获取第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括N个第一电芯，所述第二类电芯包括M个第二电芯，N和M为正整数；在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2；将所述第一类电芯和第二类电芯以包括串联的方式电连接，以形成如上所述的电池组。
采用本申请的制造方法的电池组可保证不同化学体系电芯在长期使用过程中的寿命衰减速率尽量接近，从而避免了混合串联模组中某类电芯的寿命短板，显著提升了模组的整体循环使用寿命。
本申请中电池组的技术特征也适用于电池组的制造方法中，并产生相应的有益效果。
第一类电芯和第二类电芯均可商购获得或采用本领域已知的方法制备得到。作为示例，可以将正极极片、隔离膜和负极极片经堆叠工艺或卷绕工艺形成电池单体；将电池单体装入外包装中，注入电解液，经封装等后续工序后，得到电池单体。
正极极片可按照本领域常规方法制备。例如，将正极活性物质、导电剂和粘结剂分散于溶剂中，形成均匀的正极浆料，溶剂例如是N-甲基吡咯烷酮(NMP)；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，得到正极极片。
负极极片可以按照本领域常规方法制备。例如，将负极活性物质、导电剂、粘结剂和增稠剂分散于溶剂中，形成均匀的负极浆料，溶剂例如是去离子水；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，得到负极极片。
[制造设备]
本申请另一方面提供一种电池组的制造设备，包括：夹臂单元，所述夹臂单元用于获取第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括N个第一电芯，所述第二类电芯包括M个第二电芯，N和M为正整数；在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2；组装单元，所述组装单元用于将所述第一类电芯和所述第二 类电芯以包括串联的方式电连接，以形成如上所述的电池组；以及控制单元，所述控制单元用于控制所述夹臂单元和所述组装单元。
[电池包]
本申请另一方面还提供一种电池包，其中包括本申请任意一种或几种电池组。电池包所含电池组的数量可以根据电池包的应用和容量进行调节。可选地，电池包中还可以进一步包含电池管理系统模块(BMS)、冷却/加热部件等辅助构件。
在一些实施方式中，电池包包括两个以上的电池组，每个电池组均为本申请所述的电池组。该电池包具有较高的安全性，同时其中的不同化学体系电芯的容量衰减趋势基本一致，因而其循环寿命能得到显著提升。
图6和图7作为一个示例的电池包1。参照图6和图7，在电池包1中可以包括电池箱和设置于电池箱中的多个电池组4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池组4的封闭空间。多个电池组4可以按照任意的方式排布于电池箱中。
[用电装置]
本申请另一方面还提供一种用电装置，所述用电装置包括本申请所述的电池组或电池包。所述电池组或电池包可用作用电装置的电源，用于给用电装置提供动力；也可以作为用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。所述用电装置可以根据其使用需求来选择电化学装置，如电池组或电池包。
图8是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。该用电装置可以采用电池包或电池模组。
实施例
下面，通过具体实施例详细描述本申请的技术方案及其优点。
《电芯制备》
参考GB/T 31484-2015《电动汽车用动力蓄电池循环寿命要求及试验方法》，各实施例和对比例中的电芯的制备方法如下。
1、正极浆料的制备
将正极材料与导电炭Super P、粘结剂聚偏二氟乙烯(PVDF)按95:3:2重量比在适量的N-甲基吡咯烷酮(简写为NMP)溶剂中充分搅拌混合，使其形成均匀的、粘度为10000mPa·s的稳定浆料，浆料静置24小时内，不发生凝胶、分层或者沉降等现象。
2、正极极片的制备
将正极材料浆料均匀涂覆于正极集流体Al箔上，干燥后把极片冷压到设计压密，分条备用，得到正极极片。
3、电解液的制备
将等量体积的碳酸乙烯酯溶解在碳酸丙烯酯中，然后将六氟磷酸锂盐均匀溶解在该混合溶剂中(六氟磷酸锂浓度为1.0M/L)备用，得到电解液。
4、负极极片的制备
将负极活性材料例如石墨与导电炭、粘结剂聚苯乙烯丁二烯共聚物(SBR)、增稠剂羧甲基纤维素钠(CMC)按95:2:2:1重量比在适量的水溶剂中充分搅拌混合，使其形成均匀的负极稳定浆料；将此浆料均匀涂覆于负极集流体Cu箔上，干燥后把极片冷压到设计压密，分条备用。
5、隔离膜
选用PE作为隔离膜。
6、电芯的制备
采用常规的电芯制作工艺，将正极极片、隔离膜和负极极片一起卷绕成裸电芯，然后置入电池壳体中，注入电解液，随之进行化成、密封等工序，最终得到可充电动力电芯。
《电池组的组装》
电池组以串联形式电连接的第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，所述第一类电芯包括6个第一电芯，所述第二类电芯包括3个第二电芯，以BAAABAAAB的方式进行排布(A代表第一电芯，B代表第二电芯)。
《电芯及电池组的测试方法》
1、第一电芯及第二电芯的SOH测试方法
参考GB/T 31484-2015《电动汽车用动力蓄电池循环寿命要求及试验方法》测试电芯的实际容量，使用相同测试流程测得的实际容量与新鲜出厂电芯额定容量的 比值为SOH。
实际容量(计为：Capx)测试步骤：
将待测电芯在25℃下静置30分钟；2)0.33C(C代表电芯额定容量。其中，充/放电电流为倍率乘以电芯额定容量，额定容量以该电芯、或该电芯所属电池模组或该电芯所属电池包的GBT认证文件中所认定的电芯容量为准)恒流放电至电芯放电终止电压，之后静置30分钟；3)0.33C恒流充电至电芯充电终止电压，恒压充电至电流<0.05C，静置5分钟；4)0.33C恒流放电至电芯放电终止电压，之后静置5分钟。由步骤3)至步骤4)测得的放电容量记为Capx。
Capx占额定容量C的百分比即为SOH。
2、第一电芯及第二电芯的SOC测试方法
参考GB/T 31484-2015《电动汽车用动力蓄电池循环寿命要求及试验方法》测试电芯在与额定容量测试流程相同的放电条件下可释放出的容量，该放电容量记为Capy，该容量占电芯实际容量Capx的百分比即为SOC。
3、第一电芯及第二电芯的负极极片的总充电容量的测试方法
(1)极片取样要求如下：
取单面涂布且经冷压后的负极极片(若是双面涂布的极片，可先擦拭掉其中一面的负极膜层)、或者是从电芯中拆解得到的负极极片(将电芯在25℃下静置30分钟；以0.33C恒流放电至电芯放电终止电压，之后静置30分钟进行满放，然后拆解电芯，取出负极极片，若是双面涂布的极片，可先擦拭掉其中一面的负极膜层，用DMC溶液进行适当冲洗，烘干待用)。用直尺测量负极极片的长度和宽度，负极极片的面积等于长度和宽度的乘积。负极极片取样位置为：选取距离边缘>15mm的中部任意位置；
(2)将负极极片设置有负极膜层的一侧与锂片作为对电极，组装扣电半电池；
(3)单位面积负极极片充电容量、负极极片总充电容量：
测试电压0.05-2.0V，测试温度25℃，充/放电倍率0.1C，取平行样不少于10个，分别测试扣式半电池的充电容量，去掉最低以及最高值后取平均值，得到该面积下负极极片的充电容量；将上述测试得到的负极极片的充电容量除以负极极片的面积，即可以得到单位面积负极极片充电容量；
负极极片总充电容量＝单位面积负极极片充电容量×电芯中负极膜片的总面积，其中，如果负极极片为在集流体的上下表面均有负极膜层，负极膜片的总面积 为负极极片上下表面参与充放电反应的负极膜层的面积之和(通常，二次电池中参与充放电反应的负极膜片的面积等于正极膜片区的总面积)。
4、第一电芯及第二电芯的容量的测试方法：
挑选待测电芯，使用电芯充放电机以及高低温箱，测试电芯在25℃下的标准倍率满充充电容量和放电容量，该放电容量即是电芯的容量。其中，充放电倍率为0.33C(C代表电芯额定容量。其中，充/放电电流为倍率乘以电芯额定容量，额定容量以该电芯的GBT认证文件中所认定的电芯容量为准)。
具体的：电芯的容量的测试流程如下：1)在25℃下静置30分钟；2)0.33C恒流放电至放电终止电压(如，NCM化学体系电芯设为2.8V，LFP化学体系电芯设为2.5V)，之后静置30分钟；3)0.33C恒流充电至充电终止电压(如，NCM化学体系电芯根据具体电芯类型为设定为4.2V、4.25V、4.3V、4.35V、4.4V、4.45V等，LFP化学体系电芯一般为3.65V，电芯的充电终止电压认定为业界公知信息)，恒压充电至电流<0.05C，之后静置5分钟；4)0.33C恒流放电至放电终止电压。此时，测得的放电容量即电芯的容量值。相关术语和测试方法参考GB/T 19596、GB/T 31484-2015、GB/T 31485-2015、GB/T 31486-2015以及《电动汽车用动力蓄电池安全要求》。
5、电池组容量保持率的测试方法：
参考GB/T 31484-2015《电动汽车用动力蓄电池循环寿命要求及试验方法》。
(1)1000圈容量保持率(/25℃)测试方法：
初始容量(计为：Cap0)测试步骤：
1)将新出厂的电池组在25℃下静置30分钟；2)0.33C(C代表电芯额定容量。其中，充/放电电流为倍率乘以电芯额定容量，额定容量以该电芯、或该电芯所属电池模组或该电芯所属电池包的GBT认证文件中所认定的电芯容量为准)恒流放电至电池组放电终止电压，之后静置30分钟；3)0.33C恒流充电至电池组充电终止电压，恒压充电至电流<0.05C，静置5分钟；4)0.33C恒流放电至电池组放电终止电压，之后静置5分钟。由步骤3)至步骤4)测得的放电容量计为Cap0。
步骤1)～步骤4)为电池组一个充放电循环。
重复上述步骤1)～步骤4)1000次，第1000次测得的放电容量计为Capn，第1000次的容量保持率为：Capn/Cap0*100％。
通过上述《电芯制备》方法，可得到以下的实施例1的电池组和比较例1的电池组。实施例1的电池组和比较例1的电池组中，第二类电芯负极容量(第二类电芯容量)彼此不同。
此外，通过上述的测试方法，可以得到示出实施例1与比较例1之间的比较结果的以下的表1。
Figure PCTCN2020139184-appb-000001
根据上述表1可知，比较例1中，第一负极极片的总充电容量与第二负极极片的总充电容量之比为0.78，即小于0.8(不在0.8至1.2的范围以内)而其他条件完全相同的情况下，电池组第1000圈的容量保持率相比于实施例1、2显著下降。比较例2中，第一负极极片的总充电容量与第二负极极片的总充电容量之比为1.3，即超过1.2(不在0.8至1.2的范围以内)而其他条件完全相同的情况下，电池组第1000圈的容量保持率相比于实施例1、2也发生显著下降。
由此可知，本申请的实施例1、2相比于比较例，通过保证第一电芯与第二电芯在相同SOH和SOC状态下负极极片的总充电容量在一定范围内，可提高电池组第1000圈的容量保持率，显著提升电池组的整体循环使用寿命。
<关于压实密度的设计>
本申请中，可选的，所述第一负极极片的压实密度与所述第二负极极片的压实密度之比为0.85至1.15。可选的，所述第一负极极片的压实密度与所述第二负极极片的压实密度之比为0.95至1.05。可选的，所述第一负极极片的密度和所述第二负极极片的密度都处于1.0g/cm 3至1.9g/cm 3的范围内。可选的，所述第一负极极片的密度和所述第二负极极片的密度都处于1.2g/cm 3至1.8g/cm 3的范围内。
本申请的发明人通过潜心研究发现：负极极片的压实密度在适当的范围内时，负极极片的孔隙率适中，由此，可以改善负极极片中与电解液的界面副反应，抑制对电解液和负极活性层材料的消耗，可有效提升电芯的循环寿命；并且，由于负极极片中所需填充的孔隙总体积适中，因而无需使用过多的电解液，有利于提升电芯的能量密度。
本申请中，通过尽可能地使所述第一负极极片的压实密度与所述第二负极极片的压实密度一致，从而能够使得两种电芯在使用过程中的寿命衰减速率基本一致，可显著提升电池组的整体寿命和综合性能。
下面，通过具体实施例详细描述本申请的技术方案及其优点。
《电芯制备》
关于电芯的制备，采用与上述实施例1的《电芯制备》类似的方式，只是 对于压实密度，改变成以下的实施例3～10所示的值。
《压实密度的测试方法》
压实密度可采用本领域已知的方法进行测试。负极膜层的压实密度的示例性测试方法如下：取单面涂布且经冷压后的负极极片(若是双面涂布的极片，可先擦拭掉其中一面的负极膜层)，冲切成面积为S1的小圆片，称其重量，记为M1；测试负极膜层的厚度，记为H；然后将负极膜层擦拭掉，称量负极集流体的重量，记为M2；负极膜层的压实密度dc＝(M1-M2)/S1/H。
通过上述《电芯制备》方法，可得到以下的实施例3～10的电池组。实施例3～6的电池组中，第一类电芯的负极极片的压实密度彼此相同，但第二类电芯的负极极片的压实密度彼此不同。实施例7～10的电池组中，第一类电芯的负极极片的压实密度与第二类电芯的负极极片的压实密度之比相同，但第一类电芯的负极极片的压实密度彼此不同，第二类电芯的负极极片的压实密度彼此不同。
此外，通过上述的测试方法，可以得到示出实施例3～6之间的比较结果的以下的表2。
Figure PCTCN2020139184-appb-000002
根据上述表2可知，在第一负极极片的压实密度与第二负极极片的压实密度之比为0.82或1.18，即小于0.85或大于1.15(不在0.85至1.15的范围以内)而其他条件完全相同的情况下(比较例2、3)，电池组第1000圈的容量保持率相比于实施例3、4下降。
由此可知，本申请的实施例3、4相比于实施例5、6，可提高电池组第1000圈的容量保持率，可显著提升电池组的整体寿命和综合性能。
此外，通过上述的测试方法，可以得到示出实施例7～10之间的比较结果的以下的表3。
Figure PCTCN2020139184-appb-000003
根据上述表3可知，在第一负极极片的压实密度(第二负极极片的压实密度)为0.95或1.95，即小于1或大于1.9(不在1至1.9的范围以内)而其他条件完全相同的情况下(实施例9、10)，电池组第1000圈的容量保持率相比于实施例7、8下降。
由此可知，本申请的实施例7、8相比于实施例9、10，可提高电池组第1000圈的容量保持率，可进一步提升电池组的整体寿命和综合性能。
<关于涂布质量的设计>
本申请中，可选的，所述第一负极极片的负极活性物质的单位面积涂布质量与所述第二负极极片的负极活性物质的单位面积涂布质量之比为0.85至1.15；可选的，所述第一负极极片的负极活性物质的单位面积涂布质量与所述第二负极极片的负极活性物质的单位面积涂布质量之比为0.95至1.05；可选的，所述第一负极极片的负极活性物质的单位面积涂布质量和所述第二负极极片的负极活性物质的单位面积涂布质量都处于6mg/cm 2至17mg/cm 2的范围内；可选的，所述第一负极极片的负极活性物质的单位面积涂布质量和所述第二负极极片的负极活性物质的单位面积涂布质量都处于8mg/cm 2至14mg/cm 2的范围内。
本申请的发明人通过潜心研究发现：负极极片活性物质层的涂布质量需控制在适当的范围内，一方面可以控制活性物质层的厚度，提高负极活性物质层内部反应均匀性，降低活性物质层极化，提升电芯的功率性能；另一方面，可以保证电芯和模组的能量密度较高，降低每瓦时电芯的制造成本。
本申请中，通过尽可能地使所述第一负极极片的负极活性物质的单位面积涂布质量与所述第二负极极片的负极活性物质的单位面积涂布质量一致，从而能够使得两种电芯在使用过程中的寿命衰减速率基本一致，可进一步提升电池组的整体寿命和综合性能。
下面，通过具体实施例详细描述本申请的技术方案及其优点。
《电芯制备》
关于电芯的制备，采用与上述实施例1的《电芯制备》类似的方式，只是 对于负极活性物质的单位面积涂布质量，改变成以下的实施例11～18所示的值。
《负极活性物质的单位面积涂布质量的测试方法》
取单面涂布且经冷压后的极片(若是双面涂布的极片，可先擦拭掉其中一面的活性物质层)，冲切成面积为S1的小圆片，对小圆片进行称重，其质量记为M1；然后将上述极片表面的活性物质层用溶剂浸泡，使负极活性物质层与负极集流体完全剥离，称取负极集流体的质量记为M2；由此，负极极片的单位面积涂布质量可以依据公式计算得到：负极极片的单位面积涂布质量＝(M1-M2)/S1。
通过上述《电芯制备》方法，可得到以下的实施例11～18的电池组。实施例11～14的电池组中，第一类电芯的负极极片的负极活性物质的单位面积涂布质量相同，但第二类电芯的负极极片的负极活性物质的单位面积涂布质量彼此不同。实施例15～18的电池组中，第一类电芯的负极极片的负极活性物质的单位面积涂布质量与第二类电芯的负极极片的负极活性物质的单位面积涂布质量之比相同，但第一类电芯的负极极片的负极活性物质的单位面积涂布质量彼此不同，第二类电芯的负极极片的负极活性物质的单位面积涂布质量彼此不同。
此外，通过上述的测试方法，可以得到示出实施例11～14之间的比较结果的以下的表4。
Figure PCTCN2020139184-appb-000004
根据上述表4可知，在第一负极极片的负极活性物质的单位面积涂布质量与第二负极极片的负极活性物质的单位面积涂布质量之比为0.83或1.18，即小于0.85或大于1.15(不在0.85至1.15的范围以内)而其他条件完全相同的情况下(实施例13、14)，电池组第1000圈的容量保持率相比于实施例11、12下降。
由此可知，本申请的实施例11、12相比于实施例13、14，可提高电池组第1000圈的容量保持率，可显著提升电池组的整体寿命和综合性能。
此外，通过上述的测试方法，可以得到示出实施例15～18之间的比较结果的以下的表5。
Figure PCTCN2020139184-appb-000005
根据上述表5可知，在第一负极极片的负极活性物质的单位面积涂布质量(第二负极极片的负极活性物质的单位面积涂布质量)为5.5或17.5，即小于6.0或大于17.0(不在6.0至17.0的范围以内)而其他条件完全相同的情况下(实施例17、18)，电池组第1000圈的容量保持率相比于实施例15、16下降。
由此可知，本申请的实施例15、16相比于实施例17、18，可提高电池组第1000圈的容量保持率，可进一步提升电池组的整体寿命和综合性能。
此外，上述的实施例及比较例中，第一类电芯的正极极片都为LiFePO 4，但是第一类电芯的正极极片也可为其他材料，例如LiMn 0.5Fe 0.5PO 4、LiMn 0.6Fe 0.4PO 4、LiMn 0.7Fe 0.3PO 4、Na 3V 2(PO 4) 2O 2F、LiFe 0.998Ti 0.002PO 4、LiFe 0.995Ti 0.005PO 4。
以下，通过表6示出第一类电芯或第二类电芯的正极极片为不同材料时的实施例19～25。
Figure PCTCN2020139184-appb-000006
根据上述表6可知，经过掺杂及包覆且优化设计后的实施例23(第一类电芯的正极极片为LiFe 0.998Ti 0.002PO 4且第二类电芯的正极极片为LiNi 0.65Co 0.079Mn 0.27Zr 0.001O2)、实施例24(第一类电芯的正极极片为LiFe 0.995Ti 0.005PO 4且第二类电芯的正极极片为LiNi 0.70Co 0.065Mn 0.24Ti 0.003W 0.002O2)中，模组第1000圈容量保持率分别为96％和98％，显示出了最为优异的循环寿命。
本说明书中各实施例或实施方式采用递进的方式描述，每个实施例重点说明的都是与其他实施例的不同之处，各个实施例之间相同相似部分相互参见即可。
在本说明书的描述中，参考术语“一个实施方式”、“一些实施方式”、“示意性实施方式”、“示例”、“具体示例”、或“一些示例”等的描述意指结合实施方式或示例描述的具体特征、结构、材料或者特点包含于本申请的至少一个实施方式或示例中。在本说明书中，对上述术语的示意性表述不一定指的是相同的实施方式或示例。而且，描述的具体特征、结构、材料或者特点可以在任何的一个或多个实施方式或示例中以合适的方式结合。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (14)

  1. 一种电池组，该电池组包括至少以串联连接的第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，
    所述第一类电芯包括N个第一电芯，
    所述第二类电芯包括M个第二电芯，N和M为正整数；
    在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2。
  2. 如权利要求1所述的电池组，其中，
    在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一负极极片的总充电容量与所述第二负极极片的总充电容量之比为0.9至1.1。
  3. 如权利要求1或2所述的电池组，其中，
    所述第一负极极片的放电容量与所述第二负极极片的放电容量之比为0.8至1.2，可选地为0.9至1.1。
  4. 如权利要求1-3任一项所述的电池组，其中，
    所述第一类电芯的额定容量与所述第二类电芯的额定容量之比为0.8至1.2，可选地为0.9至1.1。
  5. 如权利要求1-4任一项所述的电池组，其中，所述第一负极极片与所述第二负极极片还至少满足以下条件之一：
    (1)所述第一负极极片的压实密度与所述第二负极极片的压实密度之比为0.85至1.15，可选地为0.95至1.05；
    (2)所述第一负极极片的单位面积涂布质量与所述第二负极极片的单位面积涂布质量之比为0.85至1.15，可选地为0.95至1.05；
    (3)所述第一负极极片的孔隙率与所述第二负极极片的孔隙率之比为0.8至1.25，可选地为0.9至1.1。
  6. 如权利要求1-5任一项所述的电池组，其中，
    所述第一负极极片的密度和所述第二负极极片的密度各自独立地为1.0g/cm 3至1.9g/cm 3，可选地为1.2g/cm 3至1.8g/cm 3。
  7. 如权利要求1-6任一项所述的电池组，其中，
    所述第一负极极片的单位面积涂布质量和所述第二负极极片的单位面积涂布质量各自独立地为6mg/cm 2至17mg/cm 2，可选地为8mg/cm 2至14mg/cm 2。
  8. 如权利要求1-7任一项所述的电池组，其中，
    所述第一负极极片的孔隙率和所述第二负极极片的孔隙率各自独立地为15％至35％，可选地为20％至30％。
  9. 如权利要求1-8任一项所述的电池组，其中，
    所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质可以独立地选自人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种；
    可选地，所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质的组分相同。
  10. 如权利要求1-9任一项所述的电池组，其中，
    所述第一类电芯的数量与所述第二类电芯的数量之比为0.1至50，可选地为2至10。
  11. 一种电池包，其中，包括权利要求1-10中任一项所述的电池组。
  12. 一种用电装置，其中，包括权利要求1-10中任一项所述的电池组或权利要求11所述的电池包，且以所述电池组或电池包作为所述用电装置的电源或者能量存储单元。
  13. 一种电池组的制造方法，其中，包括如下步骤：
    获取第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，
    所述第一类电芯包括N个第一电芯，
    所述第二类电芯包括M个第二电芯，N和M为正整数；
    在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、 且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2；
    将所述第一类电芯和第二类电芯以包括串联的方式电连接，以形成权利要求1至10中任一项所述的电池组。
  14. 一种电池组的制造设备，其中，包括：
    夹臂单元，所述夹臂单元用于获取第一类电芯和第二类电芯，所述第一类电芯和第二类电芯为不同的化学体系电芯，
    所述第一类电芯包括N个第一电芯，
    所述第二类电芯包括M个第二电芯，N和M为正整数；
    在所述第一电芯的电池健康状态SOH与所述第二电芯的SOH相同、且所述第一电芯的荷电状态SOC与所述第二电芯的SOC相同的情况下，所述第一电芯的第一负极极片的总充电容量与所述第二电芯的第二负极极片的总充电容量之比为0.8至1.2；
    组装单元，所述组装单元用于将所述第一类电芯和所述第二类电芯以包括串联的方式电连接，以形成权利要求1-10中任一项所述的电池组；以及
    控制单元，所述控制单元用于控制所述夹臂单元和所述组装单元。
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