[go: up one dir, main page]
More Web Proxy on the site http://driver.im/

CN115000514A - Electrolyte, negative electrode, lithium ion battery and vehicle - Google Patents

Electrolyte, negative electrode, lithium ion battery and vehicle Download PDF

Info

Publication number
CN115000514A
CN115000514A CN202110224657.6A CN202110224657A CN115000514A CN 115000514 A CN115000514 A CN 115000514A CN 202110224657 A CN202110224657 A CN 202110224657A CN 115000514 A CN115000514 A CN 115000514A
Authority
CN
China
Prior art keywords
electrolyte
lithium
carbonate
negative electrode
additive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202110224657.6A
Other languages
Chinese (zh)
Inventor
刘刚
王圣
刘行
段柏禹
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BYD Co Ltd
Original Assignee
BYD Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BYD Co Ltd filed Critical BYD Co Ltd
Priority to CN202110224657.6A priority Critical patent/CN115000514A/en
Publication of CN115000514A publication Critical patent/CN115000514A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/056Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566Liquid materials
    • H01M10/0567Liquid materials characterised by the additives
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/058Construction or manufacture
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00Batteries for particular applications
    • H01M2220/20Batteries in motive systems, e.g. vehicle, ship, plane
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Physics & Mathematics (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application discloses electrolyte, negative pole, lithium ion battery and vehicle. The electrolyte includes: lithium salts, organic solvents, and additives; the additive comprises a first additive, the first additive is a thiadiazole compound, and the thiadiazole compound has the following structural formula:
Figure DDA0002956693230000011
wherein R is 1 And R 2 Are respectively selected from hydrogen atom, halogen atom, ether group, amino group and C 1 ‑C 10 Alkyl radical, C 2 ‑C 10 Alkenyl radical, C 2 ‑C 10 Alkynyl, C 3 ‑C 10 Cycloalkyl and C 2 ‑C 8 At least one nitrogen-containing polycyclic ring; c 1 ‑C 10 Alkyl radical, C 2 ‑C 10 Alkenyl radical, C 2 ‑C 10 Alkynyl, C 3 ‑C 10 Cycloalkyl and C 2 ‑C 8 The hydrogen atoms in the nitrogen-containing polycyclic ring may be partially or fully substituted with a substituent. The electrolyte has higher reduction potential, an SEI film is preferentially formed on a negative electrode, and the formed SEI film has better elasticity, so that the performance of the battery is favorably improved.

Description

Electrolyte, negative electrode, lithium ion battery and vehicle
Technical Field
The invention relates to the field of new energy, in particular to an electrolyte, a negative electrode, a lithium ion battery and a vehicle.
Background
The lithium ion battery has the advantages of high working voltage, large specific capacity, long cycle life, no memory effect, environmental friendliness and the like, and is widely applied to electronic products such as communication tools, notebook computers and the like. With the application of the lithium ion battery in electric vehicles and hybrid electric vehicles, people have higher requirements on the specific capacity of the lithium ion battery, and the silicon-carbon composite material relieves the problem of silicon volume expansion to a certain extent, so that the problems of capacity attenuation and electrode structure damage of the battery are solved.
However, the cycle performance of the battery has a close relationship with the formation, morphology, and structure of an SEI film (solid electrolyte interface film). In order to ensure that a good and stable SEI film is formed on the surface of a silicon-carbon composite negative electrode, a negative electrode film-forming additive is added into a conventional electrolyte system, the most frequently used and most effective electrolyte additive is fluoroethylene carbonate (FEC), but the FEC is easily decomposed at high temperature to generate hydrofluoric acid, so that the decomposition of lithium salt and a solvent is initiated, a large amount of gas is generated, the components of the electrolyte are changed, and the performance of a battery is reduced.
Disclosure of Invention
In view of the above-described drawbacks or deficiencies in the prior art, it is desirable to provide an electrolyte, a negative electrode, a lithium ion battery, and a vehicle.
In a first aspect, the present invention provides an electrolyte comprising: lithium salts, organic solvents, and additives;
the additive comprises a first additive, wherein the first additive is a thiadiazole compound, and the thiadiazole compound has the following structural formula:
Figure BDA0002956693210000021
wherein R is 1 And R 2 Are respectively selected from hydrogen atom, halogen atom, ether group, amino group and C 1 -C 10 Alkyl radical, C 2 -C 10 Alkenyl radical, C 2 -C 10 Alkynyl, C 3 -C 10 Cycloalkyl and C 2 -C 8 At least one nitrogen-containing polycyclic ring;
C 1 -C 10 alkyl radical, C 2 -C 10 Alkenyl radical, C 2 -C 10 Alkynyl, C 3 -C 10 Cycloalkyl and C 2 -C 8 The hydrogen atoms in the nitrogen-containing polycyclic ring may be partially or fully substituted with a substituent.
Alternatively, the substituent includes at least one of a halogen atom, a cyano group, a carboxyl group, and a sulfonic acid group.
The thiadiazole compound is selected from at least one of the following compounds:
Figure BDA0002956693210000022
Figure BDA0002956693210000031
as an optional scheme, the mass fraction of the first additive is 0.1-10% based on the total mass of the electrolyte.
As an optional scheme, the mass fraction of the first additive is 0.5% -5% based on the total mass of the electrolyte.
As an option, the additive further comprises: and a second additive, wherein the second additive is at least one selected from vinylene carbonate, fluoro-carbonate, di-fluoro-ethylene carbonate, ethylene sulfite, methylene methanedisulfonate, 1, 3-propane sultone, 1, 3-propylene sultone, vinyl sulfate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate.
Optionally, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis fluorooxalato borate, lithium bis (trifluoromethylsulfonyl) imide and lithium bis fluorosulfonyl imide.
Alternatively, the organic solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl methyl carbonate, γ -butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.
Optionally, the organic solvent is ethylene carbonate and ethyl methyl carbonate, and the mass ratio of the ethylene carbonate to the ethyl methyl carbonate is 1 (1-3).
In a second aspect, the present invention provides a negative electrode of a lithium ion battery, including a negative electrode current collector and a negative electrode active material layer located on a surface of the negative electrode current collector, where a surface of the negative electrode active material layer has an interface protective film, and the interface protective film is obtained by the electrolyte formation according to the first aspect.
In a third aspect, the present invention provides a lithium ion battery comprising: the electrolyte according to the first aspect and/or the negative electrode according to the second aspect.
In a fourth aspect, the present invention provides a vehicle, comprising: the lithium ion battery of the third aspect.
The electrolyte provided by the application comprises a first additive, wherein the first additive comprises a thiadiazole compound, the thiadiazole compound has a higher reduction potential, and a five-membered ring of a carbon-nitrogen diene structure of the thiadiazole compound is beneficial to generating a polymer SEI film on the surface of a negative electrode through electroreduction polymerization, so that the SEI film has good elasticity, is suitable for the volume change of silicon in a silicon-carbon negative electrode in the charge and discharge process of a battery, and improves the cycle performance of the battery; meanwhile, in the polymerization process of the thiadiazole compound, the lone electron pair of the nitrogen atom and the carbon-carbon double bond form a delocalized large pi bond, which is beneficial to improving the conductivity of the SEI film and further improving the performance of the battery; and high-temperature storage experiments prove that the high-temperature-resistant and low-temperature-resistant FEC battery has better high-temperature stability compared with the existing FEC battery, and is beneficial to improving the high-temperature performance of the battery.
Drawings
Fig. 1 is the reduction potential test results of example 1 and comparative example 1.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail with reference to examples.
In a first aspect, an embodiment of the present invention provides an electrolyte, including: lithium salts, organic solvents, and additives;
the additive comprises a first additive, the first additive is a thiadiazole compound, and the thiadiazole compound has the following structural formula:
Figure BDA0002956693210000051
wherein R is 1 And R 2 Are respectively selected from hydrogen atom, halogen atom, ether group, amino group and C 1 -C 10 Alkyl radical, C 2 -C 10 Alkenyl radical, C 2 -C 10 Alkynyl, C 3 -C 10 Cycloalkyl and C 2 -C 8 At least one nitrogen-containing polycyclic ring;
C 1 -C 10 alkyl radical, C 2 -C 10 Alkenyl radical, C 2 -C 10 Alkynyl, C 3 -C 10 Cycloalkyl and C 2 -C 8 The hydrogen atoms in the nitrogen-containing polycyclic ring may be partially or fully substituted with a substituent.
It should be noted that, in the following description,
the thiadiazole compound of the embodiment of the present invention may be used alone as an additive for an electrolyte, and may be used in combination with an existing additive, such as FEC.
The thiooxy double bond in the thiadiazole compound has a strong electron withdrawing ability, so that the lowest unoccupied orbital (LUMO) of the five-membered heterocyclic ring is reduced. According to the front line orbit theory, the lower LUMO energy level can enable molecules to have higher reduction potential, so that the thiadiazole compound can be reduced by electrons more easily obtained at the negative electrode of a lithium battery. Through cyclic voltammetry tests, as shown in fig. 1, the thiadiazolated compounds in the examples of the present application have a higher reduction potential than ethylene carbonate, indicating that the additives of the examples of the present application can undergo a reduction reaction on the surface of the silicon anode in preference to ethylene carbonate.
The thiadiazole compound contains a conjugated carbon-nitrogen diene structure, electrons can be captured on the surface of the silicon cathode to form free radicals, then polymerization reaction is carried out, an SEI film containing a polymer chain segment is formed, the polymer chain segment enables the SEI film to have good elastic performance, and the SEI film can bear the volume change of a silicon material without cracking, so that the continuous reduction reaction of electrolyte does not occur any more, and the consumption of the electrolyte and active lithium is prevented.
Due to the occurrence of electropolymerization reaction, the conjugated diene structure of the thiadiazole compound is destroyed, a new five-membered heterocyclic ring is formed in a polymer chain segment, and due to the existence of lone electron pairs on nitrogen atoms, a large pi bond delocalized on the whole five-membered ring is formed, so that lithium ions can be better transmitted in an SEI film, and the ionic conductivity of the SEI film is improved.
Wherein, C 1 -C 10 Alkyl radical, C 3 -C 10 Cycloalkyl radical, C 2 -C 10 Alkenyl radical, C 2 -C 10 Alkynyl, and C 2 -C 8 The number of carbon atoms in the nitrogen-containing multi-element ring is preferably 1-5, which is beneficial to reducing the space structure, forming a chain polymer by the thiadiazole compound and improving the elasticity of the SEI film;
C 1 -C 10 alkyl radical, C 3 -C 10 Cycloalkyl, C 2 -C 10 Alkenyl radical, C 2 -C 10 Alkynyl group and C 2 -C 8 The hydrogen atoms in the nitrogen-containing polycyclic ring may be partially or whollyThe lithium ion battery is substituted by substituent groups, so that the activity of alkyl, alkenyl, alkynyl, cycloalkyl or a nitrogen-containing polycyclic ring is further improved, an SEI (solid electrolyte interphase) film can be generated on the negative electrode of the lithium ion battery, a solvent is protected, the consumption of electrolyte and active lithium is reduced, and the performance of the battery is improved.
In summary, the electrolyte solution of the embodiment of the application includes the first additive, the first additive includes a thiadiazole compound, the thiadiazole compound has a high reduction potential, and a five-membered ring of a carbonitrideene structure of the thiadiazole compound is beneficial to electroreduction polymerization on the surface of a negative electrode to generate a polymer SEI film, so that the SEI film has good elasticity, and is adapted to volume change of silicon in the charge and discharge processes of a battery, and the cycle performance of the battery is improved; meanwhile, in the polymerization process of the thiadiazole compound, the lone electron pair of the nitrogen atom and a carbon-carbon double bond form a delocalized large pi bond, so that the conductivity of the SEI film is improved, the performance of the battery is further improved, and high-temperature storage experiments prove that the thiadiazole compound has better high-temperature stability compared with the existing FEC, and the high-temperature performance of the battery is improved.
Further, the substituent includes at least one of a halogen atom, a cyano group, a carboxyl group, and a sulfonic acid group. Wherein, the self bond energy of halogen atom, cyano, carboxyl and sulfonic group is high, so that the oxidation is not easy, and the consumption of electrolyte is reduced; and the cyano group also has stronger coordination capability, can be combined with active sites (such as high-valence metal ions, such as nickel) on the surface of the positive electrode, and plays a role in shielding the active ions on the surface of the positive electrode, thereby reducing the decomposition effect of the positive electrode on the electrolyte.
Preferably, the thiadiazole compound according to the embodiment of the present invention is selected from the group consisting of 1,2, 5-thiadiazole-1, 1-dioxide (structural formula shown in formula I, CAS number: 140651-41-8), 3-ethoxy-4-methoxy-1, 2, 5-thiadiazole-1, 1-dioxide (structural formula shown in formula II, CAS number: 1379185-66-6), 4-methoxy-N, N-dimethyl-1, 1-dioxy-1, 2, 5-thiadiazole-3-amine (structural formula shown in formula III, CAS number: 90103-63-2), 3, 4-dimethoxy-1, 2, 5-thiadiazole-1, 1-dioxide (structural formula shown in formula IV, CAS number: 55904-83-1), 3, 4-dichloro- [1,2,5] thiadiazole-1, 1-dioxide (structural formula shown in formula V, CAS number: 55904-85-3), 3, 4-diethoxy-1, 2, 5-thiadiazole-1, 1-dioxide (structural formula is shown in formula VI, CAS number: 55904-84-2):
Figure BDA0002956693210000071
in a practical manner, the mass fraction of the first additive is 0.1% to 10% based on the total mass of the electrolyte, for example: 0.1%, 0.5%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%. 8%, 9% and 10%. The mass fraction range of the embodiment is beneficial to forming an SEI film on a negative electrode, the SEI film has organic solvent insolubility and can stably exist in an organic electrolyte solution, and solvent molecules cannot pass through the passivation film, so that damage to an electrode material caused by co-embedding of the solvent molecules is effectively prevented, and the cycle performance and the service life of the electrode are greatly improved.
In a preferred embodiment, the mass fraction of the first additive is 0.5% to 5% based on the total mass of the electrolyte. The more preferable mass fraction of the first additive is 1%, and the mass range ensures that the electrolyte generates an SEI film at the negative electrode, avoids the excessive first additive from increasing the viscosity of the electrolyte, and ensures that the electrolyte has good conductivity.
As an implementable manner, the additive further comprises: and a second additive selected from at least one of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), vinylethylene carbonate (VEC), vinyl sulfite (ES), Methylene Methanedisulfonate (MMDS), 1,3 Propanesultone (PS), 1, 3-propene sultone (1,3-PST), Vinyl Sulfate (VS), Lithium Difluorophosphate (LD), Lithium Difluorobis (LDP), and Lithium Tetrafluoro (LTP).
The second additive in the electrolyte is mainly used for being matched with the first additive, an SEI film with low impedance and high stability is formed on a negative electrode, the SEI film is insoluble in an organic solvent and can stably exist in an organic electrolyte solution, and solvent molecules cannot pass through the SEI film, so that co-embedding of the solvent molecules can be effectively prevented, damage to an electrode material due to co-embedding of the solvent molecules is avoided, and the cycle performance and the service life of the electrode are greatly improved.
In an implementable manner, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bis (trifluoromethylsulfonyl) imide and lithium bis fluorosulfonyl imide. The lithium salt reduces the fluorine content, thereby reducing the generated hydrofluoric acid and being beneficial to improving the high-temperature performance of the electrolyte.
As a practical mode, the concentration of the lithium salt is 0.1mol/L to 1.2 mol/L. The concentration range of the embodiment of the application is beneficial to the moderate dielectric constant of the electrolyte and the effective conduction of lithium ions.
In an implementation manner, the organic solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl methyl carbonate, γ -butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.
In a specific embodiment, the organic solvent is ethylene carbonate and ethyl methyl carbonate, and the mass ratio of the ethylene carbonate to the ethyl methyl carbonate is 1 (1-3). Preferably 3: 7. The cyclic ethylene carbonate has higher dielectric constant and high viscosity, and the linear ethyl methyl carbonate has low viscosity, so that when the cyclic ethylene carbonate and the linear ethyl methyl carbonate are used in a matching manner, the overall ionic conductivity of the electrolyte can be improved, and in addition, the cyclic ethylene carbonate can also participate in the negative electrode to form an SEI film, so that the side reaction of the negative electrode can be effectively prevented; the linear carbonate may also be dimethyl carbonate, diethyl carbonate or a mixture thereof.
In the electrolyte of the embodiment of the application, the thiadiazole compound has a high reduction potential, which is favorable for generating an SEI film on a negative electrode in preference to a solvent, and the five-membered ring of the carbonitridene structure of the thiadiazole compound is favorable for generating a polymer SEI film on the surface of the negative electrode through electroreduction polymerization, so that the SEI film has good elasticity and is suitable for the volume change of silicon in the charge and discharge processes of a battery; meanwhile, in the polymerization process of the thiadiazole compound, the lone electron pair of the nitrogen atom and the carbon-carbon double bond form a delocalized large pi bond, which is beneficial to improving the conductivity of the SEI film and further improving the performance of the battery;
and high-temperature storage experiments prove that the high-temperature-resistant and low-temperature-resistant FEC battery has better high-temperature stability compared with the existing FEC battery, and is beneficial to improving the high-temperature performance of the battery.
In a second aspect, an embodiment of the present invention provides a negative electrode of a lithium ion battery, where the negative electrode of the lithium ion battery includes a negative electrode current collector and a negative electrode active material layer located on a surface of the negative electrode current collector, and an interface protective film is provided on a surface of the negative electrode active material layer, where the interface protective film is obtained by formation of the electrolyte solution described in the first aspect. Thus, the negative electrode has all the features and advantages of the electrolyte described above, and thus, the description thereof is omitted.
In a third aspect, embodiments of the present invention provide a lithium ion battery. The lithium ion battery comprises the electrolyte of the first aspect and/or the negative electrode of the second aspect. Therefore, the lithium ion battery has all the features and advantages of the electrolyte and/or the negative electrode, and the description thereof is omitted. In general, the lithium ion battery has the advantage of being capable of having good high-temperature cycle performance.
The negative electrode of lithium batteries is mainly a silicon negative electrode, such as pure silicon, silicon oxide or a silicon carbon composite.
The positive electrode of the lithium battery may be a ternary nickel cobalt manganese material, for example, LiNi 0.33 Co 0.33 Mn 0.33 O 2 (NCM111 type), LiNi 0.4 Co 0.2 Mn 0.4 O 2 (NCM424 type), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523 type), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622 type), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811 type).
In a fourth aspect, the present disclosure provides a vehicle including the lithium ion battery of the third aspect. For example, a plurality of battery packs composed of the lithium ion batteries described above may be included. Thus, the vehicle has all the features and advantages of the lithium ion battery described above, and the description thereof is omitted.
The present invention is illustrated below by way of specific examples, which are intended to be illustrative only and not to limit the scope of the present invention in any way, and reagents and materials used therein are commercially available, unless otherwise specified, and conditions or steps thereof are not specifically described.
The lithium ion batteries of examples 1 to 15 and comparative examples 1 to 4 were prepared as follows:
(1) preparing an electrolyte:
mixing ethylene carbonate and methyl ethyl carbonate into a mixed solvent according to the mass ratio of 3:7, and adding lithium hexafluorophosphate (LiPF) into the mixed solvent 6 ) And adding an additive into the electrolyte until the molar concentration is 1.0mol/L, and uniformly stirring to obtain the electrolyte.
(2) Preparing a positive plate:
uniformly mixing NCM, Carbon Nano Tube (CNT) and polyvinylidene fluoride (PVDF) in a mass ratio of 100:2:2 to obtain paste, uniformly coating the paste on an aluminum foil serving as a positive current collector, and drying in a vacuum oven at 60 ℃ for 24 hours to obtain the positive plate.
(3) Preparing a negative plate:
uniformly mixing a carbon-coated silicon material, a conductive agent super-p, a thickening agent sodium carboxymethyl cellulose (CMC) and a binder Styrene Butadiene Rubber (SBR) according to a mass ratio of 100:2:2:3, uniformly coating the obtained paste on a copper foil serving as a negative current collector, and drying for 24 hours in a vacuum oven at 60 ℃ to obtain the negative plate.
(4) Preparing a lithium ion battery:
preparing a soft package lithium battery with a silicon negative electrode of SL523450, preparing a bare cell from a positive plate, a negative plate and an isolating membrane by a winding process in an argon glove box with water and oxygen content less than 5ppm, filling the cell into an aluminum plastic membrane packaging shell, injecting the electrolyte, sequentially sealing, standing, carrying out hot and cold pressing, forming, capacity grading and the like, and thus obtaining the lithium ion battery P1.
Preparation of a CR2016 button cell: and (3) adopting the coated silicon negative electrode plate to the lithium plate, wherein the injection amount is about 100mg, and thus obtaining the battery for the reduction potential test of the electrolyte.
Wherein the formation process comprises the following steps: the simulation battery is charged to 1.5V by 45mA (0.05C) current and is kept at 1.5V for 10 hours, so that the battery pole piece is fully soaked by electrolyte; after sufficient aging, the cell was first charged with a small current of 9mA (C/100) for 15h to form a stable and complete SEI film, then charged to 4.2V with a current of 45mA (0.05C) and then discharged to 3V.
TABLE 1 concrete kinds and contents of additives in examples 1-15 and comparative examples 1-2
Figure BDA0002956693210000111
Figure BDA0002956693210000121
Wherein the structural formula of the imidazolidinone (CAS number: 378750-35-7) is shown as
Figure BDA0002956693210000122
The structural formula of the 1,2, 5-thiadiazole (CAS number: 23091-39-6) is shown in the specification
Figure BDA0002956693210000123
The performance test process and test results of the lithium ion battery are described as follows:
(1) reduction potential test
The button cell batteries in the examples and the comparative examples are subjected to cyclic voltammetry, the scanning speed is 0.2mV/s, and the scanning range is 0.005-2.5V. The test equipment was an electrochemical workstation of chenhua model CHI 600C.
(2) High temperature storage test of electrolyte
The electrolytes of examples and comparative examples were sealed in square aluminum-plastic bags, respectively, stored in a 60 ℃ incubator for 7 days, and the volume expansion rates before and after the storage were calculated by size exclusion. The volume expansion (%) is the percentage of the volume after storage at high temperature divided by the volume before storage.
(3) Silicon negative electrode normal/high temperature battery cycle test and elasticity test of negative electrode surface SEI film after cycle
The pouch cells of examples and comparative examples (10 for each condition, the results were averaged) were cycled 400 times between 3.0V and 4.2V at room temperature (25 ℃) and elevated temperature of 60 ℃ respectively at 900mA (1C). The test instrument can be a domestic blue model CT2001C test cabinet, and the capacity retention rate is calculated. The capacity retention (%) was calculated as a percentage obtained by dividing the discharge capacity at the 150 th cycle by the initial discharge capacity at the first cycle.
After the completion of the cycle, the batteries of examples and comparative examples were disassembled, and the silicon negative electrode was cut to 1X 1cm 2 The Young's modulus of the pellets was measured by an atomic force microscope (AFM, Bruker Dimension Icon) probe method, and the elasticity of the SEI film on the surface of the negative electrode was measured by the Young's modulus, which indicates that the elasticity of the SEI film was better when the Young's modulus was small. Young's modulus calculation method F ═ (2/pi) (E/(1-v2)) δ 2tan (σ), where F is probe force, E is young's modulus, v is Poisson coefficient (here 0.5), δ is SEI film thickness, and σ is half cone tip apex angle. The method is publicly reported in the literature.
The results of the reduction potential test of the electrolytes of examples 1 to 15 and comparative examples 1 to 4 according to the procedure and method described above are shown in table 1:
TABLE 1 reduction potential test results of examples 1 to 15 and comparative examples 1 to 4
Figure BDA0002956693210000131
Figure BDA0002956693210000141
TABLE 2 high-temperature storage test results of electrolytes of examples 1 to 15 and comparative examples 1 to 4
Figure BDA0002956693210000142
Figure BDA0002956693210000151
Table 3 cycle test results of examples 1 to 15 and comparative examples 1 to 4 and elasticity test results of SEI film on surface of negative electrode after cycle
Figure BDA0002956693210000152
Figure BDA0002956693210000161
According to the results shown in table 1 and fig. 1:
in comparison with comparative examples 1 to 4, the additives of the electrolytes of examples 1 to 15 include thiadiazole compounds, each having a reduction potential higher than that of comparative examples 1 to 4; and the reduction potentials of examples 1-6, examples 8-12, and example 15 were all higher at 1.25-1.4V (vs. Li/Li) + ). Therefore, the additive of the embodiment of the invention can be reduced to form a film in preference to solvent molecules during the battery cycle process, and plays a role in protecting the electrolyte.
As can be seen from the reduction potentials of examples 1 and 15 and comparative example 2, the additive of the examples of the present invention can be used alone or in combination with an existing negative electrode film-forming additive (e.g., FEC); comparing the reduction potentials of example 15 and comparative example 2, the thiadiazole compound is advantageous for increasing the reduction potential of the electrolyte, and is further advantageous for preferentially reducing to form a film.
The reduction potential of example 1 is higher, the additive of example 1 is 1,2, 5-thiadiazole-1, 1-dioxide, the additive of comparative example 3 is imidazolinone (five-membered ring does not contain sulfur), and the additive of comparative example 4 is 1,2, 5-thiadiazole (five-membered ring does not contain sulfur oxygen double bond), compared to comparative examples 3 and 4. Therefore, sulfur in the additive in the embodiments of the present invention can lower the LUMO level of the molecule and increase the reduction potential, so that the molecule is more easily polymerized in the negative electrode of the battery.
According to the results shown in table 2:
compared to comparative examples 1-4, the electrolytes of the additives of examples 1-6 have much lower volume expansion rates at high temperatures than comparative examples 1-4. Therefore, it is demonstrated that the electrolyte solutions of examples 1-6 contain thiadiazole compounds at the same amount of additives, so that the electrolyte solutions can be stable at high temperature, generate little gas, and are beneficial to improving the performance of the battery.
The electrolytes of examples 1 to 12 have a lower volume expansion rate after storage at high temperature than those of examples 13 to 14, compared to examples 13 to 14. Therefore, the mass range of the thiadiazole compound in the electrolyte disclosed by the embodiment of the invention is in a range from 0.1% to 10%, which is beneficial to improving the high-temperature storage performance of the electrolyte.
According to the results shown in table 3:
as can be seen from the capacity retention rates of the batteries subjected to the cycle tests at 25 ℃ and 60 ℃ in table 3, the capacity retention rates of the silicon negative electrode batteries of examples 1 to 6 after 400 cycles are all higher than those of comparative examples 1 to 4, so that the additive thiadiazole compound in the embodiment of the invention is beneficial to improving the cycle performance of the batteries under the condition of the same additive amount; after 60 ℃ circulation, the capacity retention rate is over 50%, and the additive further improves the high-temperature circulation performance of the battery.
From the young's modulus results in table 3, it can be seen that the young's moduli of the silicon negative electrode batteries of examples 1 to 6 after the completion of the cycle were all lower than those of comparative examples 1 to 4, smaller young's moduli, thus indicating that the additives of the examples of the present invention have better elasticity in the SEI film formed on the negative electrode with the same amount of the additives. The possible reason for the analysis is that the additives of examples 1 to 6 facilitate the formation of an SEI film containing a polymer segment at the negative electrode, making the SEI film elastic, thereby improving the cycle performance of the silicon negative electrode battery.
In conclusion, the electrolyte has higher reduction potential, which is beneficial to preferentially forming an SEI film on the surface of a negative electrode, and the thiadiazole compound in the electrolyte enables the SEI film to have good elasticity, so that the electrolyte is suitable for the volume change of silicon in the charge and discharge process of a battery, and the cycle performance of the battery is improved; in addition, compared with the existing FEC, the electrolyte has better high-temperature stability, and is beneficial to improving the high-temperature performance of the battery.
The foregoing description is only exemplary of the preferred embodiments of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention according to the present application is not limited to the specific combination of the above-mentioned features, but also covers other embodiments where any combination of the above-mentioned features or their equivalents is made without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims (12)

1. An electrolyte, comprising: lithium salts, organic solvents, and additives;
the additive comprises a first additive, wherein the first additive is a thiadiazole compound, and the thiadiazole compound has a structural formula as follows:
Figure FDA0002956693200000011
wherein R is 1 And R 2 Are respectively selected from hydrogen atom, halogen atom, ether group, amino group and C 1 -C 10 Alkyl radical, C 2 -C 10 Alkenyl radical, C 2 -C 10 Alkynyl, C 3 -C 10 Cycloalkyl and C 2 -C 8 At least one nitrogen-containing polycyclic ring;
said C is 1 -C 10 Alkyl radical, said C 2 -C 10 Alkenyl radical, said C 2 -C 10 Alkynyl, said C 3 -C 10 Cycloalkyl and said C 2 -C 8 The hydrogen atoms in the nitrogen-containing polycyclic ring may be partially or fully substituted with a substituent.
2. The electrolyte of claim 1, wherein the substituent comprises at least one of a halogen atom, a cyano group, a carboxyl group, and a sulfonic acid group.
3. The electrolyte of claim 1, the thiadiazole compound being selected from at least one of the following compounds:
Figure FDA0002956693200000012
Figure FDA0002956693200000021
4. the electrolyte of claim 1, wherein the mass fraction of the first additive is 0.1% to 10% based on the total mass of the electrolyte.
5. The electrolyte of claim 4, wherein the first additive is present in an amount of 0.5% to 5% by mass, based on the total mass of the electrolyte.
6. The electrolyte of any one of claims 1-5, wherein the additive further comprises a second additive selected from at least one of vinylene carbonate, fluoro-carbonate, di-fluoro-ethylene carbonate, ethylene carbonate, ethylene sulfite, methylene methanedisulfonate, 1, 3-propane sultone, 1, 3-propene sultone, vinyl sulfate, lithium difluorophosphate, lithium difluorobis-oxalate, lithium tetrafluorooxalate phosphate.
7. The electrolyte of any one of claims 1-5, wherein the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis fluorooxalato borate, lithium bis (trifluoromethylsulfonyl) imide, and lithium bis fluorosulfonyl imide.
8. The electrolyte of any one of claims 1-5, wherein the organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl methyl carbonate, γ -butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.
9. The electrolyte according to claim 8, wherein the organic solvent is ethylene carbonate and ethyl methyl carbonate, and the mass ratio of the ethylene carbonate to the ethyl methyl carbonate is 1 (1-3).
10. The negative electrode of the lithium ion battery is characterized by comprising a negative electrode current collector and a negative electrode active material layer positioned on the surface of the negative electrode current collector, wherein the surface of the negative electrode active material layer is provided with an interface protective film, and the interface protective film is obtained by the formation of the electrolyte according to any one of claims 1 to 9.
11. A lithium ion battery, comprising: the electrolyte of any one of claims 1 to 9 and/or the negative electrode of claim 10.
12. A vehicle comprising the lithium ion battery of claim 11.
CN202110224657.6A 2021-03-01 2021-03-01 Electrolyte, negative electrode, lithium ion battery and vehicle Pending CN115000514A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110224657.6A CN115000514A (en) 2021-03-01 2021-03-01 Electrolyte, negative electrode, lithium ion battery and vehicle

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110224657.6A CN115000514A (en) 2021-03-01 2021-03-01 Electrolyte, negative electrode, lithium ion battery and vehicle

Publications (1)

Publication Number Publication Date
CN115000514A true CN115000514A (en) 2022-09-02

Family

ID=83018118

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110224657.6A Pending CN115000514A (en) 2021-03-01 2021-03-01 Electrolyte, negative electrode, lithium ion battery and vehicle

Country Status (1)

Country Link
CN (1) CN115000514A (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007172990A (en) * 2005-12-21 2007-07-05 Sony Corp Electrolyte and battery
CN102856586A (en) * 2011-06-28 2013-01-02 夏普株式会社 Nonaqueous secondary battery and flame retardant for use in the same
KR20140022348A (en) * 2012-08-14 2014-02-24 솔브레인 주식회사 Electrolyte and lithium secondary battery comprising the same
CN111883828A (en) * 2020-07-24 2020-11-03 香河昆仑化学制品有限公司 Non-aqueous electrolyte of lithium ion battery and lithium ion battery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007172990A (en) * 2005-12-21 2007-07-05 Sony Corp Electrolyte and battery
CN102856586A (en) * 2011-06-28 2013-01-02 夏普株式会社 Nonaqueous secondary battery and flame retardant for use in the same
KR20140022348A (en) * 2012-08-14 2014-02-24 솔브레인 주식회사 Electrolyte and lithium secondary battery comprising the same
CN111883828A (en) * 2020-07-24 2020-11-03 香河昆仑化学制品有限公司 Non-aqueous electrolyte of lithium ion battery and lithium ion battery

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MIRIFICO, MV: "ELECTROREDUCTION OF 3, 4-DIPHENYL-1, 2, 5-THIADIAZOLE-1, 1-DIOXIDE IN ACETONITRILE SOLUTION AND REACTIONS WITH PROTON DONORS", 《ELECTROCHIMICA ACTA》, vol. 36, no. 1, 31 December 1991 (1991-12-31), pages 167 - 171, XP026506371, DOI: 10.1016/0013-4686(91)85197-F *

Similar Documents

Publication Publication Date Title
CN109873206B (en) Lithium ion battery electrolyte and lithium ion battery
CN109818064B (en) High-temperature high-voltage non-aqueous electrolyte and lithium ion battery containing same
CN109216759B (en) Lithium ion battery electrolyte and lithium ion battery
CN111883839B (en) High-voltage electrolyte and lithium ion battery based on same
KR20220062105A (en) Additives for battery electrolytes, lithium ion battery electrolytes and lithium ion batteries
CN111525190B (en) Electrolyte and lithium ion battery
CN113078356B (en) High-voltage lithium cobalt oxide lithium ion battery non-aqueous electrolyte and lithium ion battery
CN108736065B (en) Electrolyte and lithium ion battery containing electrolyte and/or anode
CN111755746B (en) Lithium ion battery electrolyte and lithium ion battery
WO2023040119A1 (en) Electrolyte additive, electrolyte containing same, and lithium-ion battery
CN108987802B (en) Non-aqueous electrolyte for high-voltage lithium ion battery
WO2023020314A1 (en) Non-aqueous electrolyte solution and lithium battery
CN113130990A (en) Electrolyte and secondary battery using same
CN109473717B (en) Electrolyte suitable for high-voltage high-nickel power battery and high-voltage high-nickel power battery
WO2023045164A1 (en) Non-aqueous electrolyte and lithium-ion battery thereof
CN110957528A (en) Additive for battery electrolyte, lithium ion battery electrolyte and lithium ion battery
CN112349963B (en) Electrolyte containing silicon solvent and mono-alkane lithium sulfate salt and lithium ion battery
CN110492177B (en) Additive for battery electrolyte, lithium ion battery electrolyte and lithium ion battery
CN112713307A (en) High-voltage non-aqueous electrolyte and lithium ion battery based on same
CN117219859A (en) Lithium ion battery electrolyte, preparation method and application
CN111129589A (en) Ternary high-voltage lithium ion battery non-aqueous electrolyte and lithium ion battery thereof
CN113871712B (en) Lithium ion battery electrolyte, preparation method thereof and lithium ion battery
CN114927758A (en) Electrolyte for improving high-temperature performance of lithium ion battery and lithium ion battery
CN115000514A (en) Electrolyte, negative electrode, lithium ion battery and vehicle
CN114583265B (en) Electrolyte, positive electrode, lithium ion battery and vehicle

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination