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WO2024087450A1 - 叠片电芯及锂离子电池 - Google Patents

叠片电芯及锂离子电池 Download PDF

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Publication number
WO2024087450A1
WO2024087450A1 PCT/CN2023/079998 CN2023079998W WO2024087450A1 WO 2024087450 A1 WO2024087450 A1 WO 2024087450A1 CN 2023079998 W CN2023079998 W CN 2023079998W WO 2024087450 A1 WO2024087450 A1 WO 2024087450A1
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WO
WIPO (PCT)
Prior art keywords
protective layer
electrode sheet
layer
laminated battery
protective
Prior art date
Application number
PCT/CN2023/079998
Other languages
English (en)
French (fr)
Inventor
张健
彭冲
Original Assignee
珠海冠宇电池股份有限公司
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.)
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Application filed by 珠海冠宇电池股份有限公司 filed Critical 珠海冠宇电池股份有限公司
Publication of WO2024087450A1 publication Critical patent/WO2024087450A1/zh

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Classifications

    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers

Definitions

  • the present application belongs to the field of lithium-ion batteries, and specifically relates to a laminated battery cell and a lithium-ion battery.
  • lithium-ion batteries Before being used in actual scenarios, lithium-ion batteries must undergo mechanical abuse testing.
  • mechanical abuse testing refers to testing the performance of batteries under simulated extreme conditions, such as extrusion testing, needle puncture testing, etc.
  • the probability of failure of lithium-ion batteries during mechanical abuse testing is very high. The reason is that when the battery is mechanically damaged, a more serious short circuit will occur inside, such as a short circuit between the current collector and the current collector of the adjacent electrode sheet, a short circuit between the active layer and the active layer of the adjacent electrode sheet, and a short circuit between the current collector and the active layer of the adjacent electrode sheet, causing thermal runaway. Therefore, how to improve the safety performance of lithium-ion batteries is a technical problem that needs to be solved urgently in this field.
  • the present application provides a laminated battery core, which can prevent the internal short circuit of the lithium-ion battery during mechanical abuse by disposing a first protective layer and a second protective layer, so that the lithium-ion battery has excellent safety performance.
  • the present application also provides a lithium-ion battery, which has good safety performance because it includes the above-mentioned laminated battery core.
  • a laminated battery cell comprising an electrode sheet assembly and a protection assembly, wherein the protection assembly is located on the surface of the outer electrode sheet of the electrode sheet assembly; the electrode sheet assembly comprises at least one functional electrode sheet, wherein the functional electrode sheet comprises a first current collector, a first protection layer and an active layer, wherein the first protection layer is located between the first current collector and the active layer; the protection assembly comprises a second current collector and a second protection layer, and the second protection layer is away from the electrode sheet assembly; the first protection layer and the second protection layer each independently comprise conductive particles and a binder; the conductive particles are inorganic fillers having a conductive coating layer on the surface, wherein the conductive coating layer accounts for 2% to 40% of the mass content of the conductive particles, and the thickness of the first protective layer and the thickness of the second protective layer are each greater than 0.5 ⁇ m.
  • At least a portion of the conductive coating layer constitutes the outermost layer of the conductive particles.
  • the conductive coating layer covers at least a portion of the inorganic filler.
  • the thickness of the first protective layer is A
  • the thickness of the second protective layer is B
  • a ⁇ B is A
  • the thickness of the first protective layer and the thickness of the second protective layer are each independently 1 ⁇ m to 10 ⁇ m.
  • the first protective layer and the second protective layer independently include 40% to 98% of conductive particles, 2% to 30% of adhesive, and 0% to 40% of non-conductive particles by mass content.
  • the first protective layer and the second protective layer each have an independent resistance of 10 to 2000 m ⁇ ; and/or the resistivity of the conductive particles is 1 to 100 ⁇ cm; and/or the average particle size of the conductive particles is 0.05 to 5 ⁇ m.
  • the conductive coating layer includes at least one of tin oxide, indium oxide, ATO, FTO, ITO, AZO, and carbon materials.
  • ATO refers to antimony-doped tin dioxide
  • FTO refers to fluorine-doped tin dioxide
  • ITO refers to tin-doped indium oxide
  • AZO is aluminum-doped zinc oxide.
  • the inorganic filler includes at least one of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, lithium iron phosphate, nickel cobalt manganese oxide, and lithium iron manganese phosphate.
  • a second aspect of the present application provides a lithium-ion battery comprising the above-mentioned laminated battery cell.
  • the first protective layer and the second protective layer play a role of physical isolation, so that the current collector of the electrode sheet is not easily exposed, and the current collector inside the battery cell is prevented from contacting the active layer or current collector of the adjacent electrode sheet, thereby reducing the probability of short circuit and significantly improving the safety performance of the battery.
  • the conductive particles can ensure the conductivity of the protective layer, so that the battery has excellent safety performance and good cycle performance.
  • the lithium-ion battery provided in the present application including the above-mentioned laminated battery core, has good safety performance and Cycle performance.
  • FIG1 is a schematic structural diagram of a laminated battery cell according to an embodiment of the present application.
  • FIG2 is a schematic diagram of the cross-sectional structure of a laminated battery cell obtained by cutting along the plane where the cutting line a shown in FIG1 is located;
  • FIG3 is a schematic structural diagram of a functional electrode sheet according to an embodiment of the present application.
  • FIG4 is a schematic diagram of the structure of a protection component according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of the structure of a protection component according to another embodiment of the present application.
  • the laminated battery cell provided in the present application includes an electrode sheet assembly 1 and a protection assembly 2, wherein the protection assembly 2 is located on the surface of the outer electrode sheet of the electrode sheet assembly 1; the electrode sheet assembly 1 includes at least one functional electrode sheet 101, and the functional electrode sheet 101 includes a first current collector 1011, a first protection layer 1012 and an active layer 1013, and the first protection layer 1012 is located between the first current collector 1011 and the active layer 1013; the protection assembly 2 includes a second current collector 2011 and a second protection layer 2012, and the second protection layer 2012 is away from the electrode sheet assembly 1; the first protection layer 1012 and the second protection layer 2012 each independently include conductive particles and a binder.
  • the laminated battery cell includes an electrode sheet assembly 1 and a protection assembly 2 which are stacked.
  • the electrode sheet assembly 1 has two opposite outer sides in the stacking direction of the laminated battery cell, and the protection assembly 2 is located on the outer side of the electrode sheet assembly 1 .
  • the number of the protection components 2 is one or two. According to the number of the protection components 2, the protection components 2 are selected to be arranged on one side or both sides of the electrode sheet assembly 1. For example, when the number of the protection components 2 is one, the protection component 2 is located at any outer side of the electrode sheet assembly 1; when the number of the protection components 2 is two, the two protection components 2 are arranged at two outer sides of the electrode sheet assembly 1.
  • the protection component 2 can protect the electrode sheet assembly, and the protection component 2 is separated from the electrode sheet assembly 1 by the diaphragm 103.
  • the electrode sheet assembly of the present application includes electrode sheets stacked in sequence, and the electrode sheets are separated by a diaphragm 103.
  • the electrode sheets are divided into functional electrode sheets and non-functional electrode sheets according to whether the first protective layer 101 is provided, and the number of functional electrode sheets 101 is one or more.
  • Each functional electrode sheet 101 includes a first current collector 1011, and the first current collector 1011 has two largest surfaces, and a first protective layer 1012 and an active layer 1013 are provided on the largest surface. Only an active layer is provided on the current collector of the non-functional electrode sheet, and no protective layer is provided.
  • the active layer 1013 is disposed on one side or on both sides, and correspondingly, the first protective layer 1012 is disposed on one side or on both sides, as long as the first protective layer 1012 is located between the active layer 1013 and the first current collector 1011 .
  • the protection assembly 2 includes a second current collector 2011, and the second current collector 2011 has two largest surfaces, and a second protection layer 2012 is disposed on the largest surface.
  • the second protection layer 2012 is located on the surface of the second current collector 2011 away from the electrode sheet assembly 1.
  • a second active layer may be coated on the surface of the second current collector 2011 close to the electrode sheet assembly 1. 2013.
  • a second protective layer may also be provided between the second active layer 2013 and the second current collector 2011.
  • the first protective layer 1012 and the second protective layer 2012 each independently include conductive particles and a binder and 0% to 40% of non-conductive particles.
  • the first protective layer 1012 and the second protective layer 2012 are composed of conductive particles and a binder.
  • the conductive particles provide a good conductive network for the first protective layer 1012 and the second protective layer 2012.
  • the binder can ensure that the first protective layer 1012 and the second protective layer 2012 are fixedly bonded to the first current collector 1011 and the second current collector 2011.
  • the applicant has found through research that the first protective layer 1012 and the second protective layer 2012 can play a role of physical isolation when the battery is mechanically damaged, so that the current collectors in the electrode sheet assembly 1 and the protective assembly 2 are not easily exposed, and the current collectors inside the laminated battery core are prevented from contacting the active layer or current collector of the adjacent electrode sheet, thereby reducing the possibility of short circuit and significantly improving the safety performance of the battery.
  • the conductive particles make the first protective layer 1012 and the second protective layer 2012 conductive, which can ensure smooth electronic conduction between the active layer and the current collector, so that the battery has excellent safety performance and good cycle performance.
  • the second active layer 2013 may be coated on the surface of the second current collector 2011 close to the electrode sheet assembly 1. At this time, a second protective layer may also be provided between the second active layer 2013 and the second current collector 2011.
  • the present application does not limit the peeling force between the first protective layer 1012 and the first current collector 1011, and the peeling force between the first protective layer 1012 and the first active layer 1013, which can be adjusted according to actual needs.
  • the peeling force between the first protective layer 1012 and the first current collector 1011 is greater than the peeling force between the first protective layer 1012 and the first active layer 1013, which can further reduce the possibility of the first current collector 1011 and the first active layer 1013 contacting and causing a short circuit in the battery.
  • the peeling force between the first protective layer 1012 and the first current collector 1011 and the peeling force between the first protective layer 1012 and the first active layer 1013 can be controlled.
  • the peeling force between the first protective layer 1012 and the first current collector 1011 is greater than the peeling force between the first protective layer 1012 and the first active layer 1013.
  • the peeling force between the first protective layer 1012 and the first current collector 1011 is greater than the peeling force between the first protective layer 1012 and the first active layer 1013 .
  • the present application does not limit the thickness of the first protective layer 1012 and the second protective layer 2012, which can be adjusted according to actual conditions.
  • the thickness of the first protective layer 1012 is A
  • the thickness of the second protective layer 2012 is B, satisfying A ⁇ B, which is more conducive to improving the safety of the battery.
  • the thickness of the first protective layer 1012 and the second protective layer 2012 are each independently 1 ⁇ m to 10 ⁇ m, preferably 2 ⁇ m to 5 ⁇ m.
  • the provision of the first protective layer 1012 and the second protective layer 2012 may lead to an increase in the battery impedance.
  • the applicant has found that when the first protective layer 1012 and the second protective layer 2012 have an independent resistance of 10m ⁇ to 2000m ⁇ , and more preferably 100m ⁇ to 1000m ⁇ , the battery can still maintain good cycle performance.
  • the resistance of the first protective layer 1012 and the second protective layer 2012 refers to the resistance value through the thickness of the first protective layer 1012 and the second protective layer 2012.
  • the resistance of the first protective layer 1012 and the second protective layer 2012 can be controlled by selecting conductive particles with different resistivities and controlling the content of the conductive particles in the first protective layer 1012 and the second protective layer 2012 .
  • the resistivity of the conductive particles can be controlled to be 1-100 ⁇ cm by controlling the type and particle size of the conductive particles.
  • the average particle size Dv50 of the conductive particles in the present application is 0.05 to 5 ⁇ m, preferably 0.1 to 1 ⁇ m.
  • Conductive particles contain conductive substances. When the content of conductive substances is low, it is not conducive to the cycle performance of the battery; when the content of conductive substances is high, it is easy to agglomerate and difficult to separate in the protective layer.
  • the applicant has found that when the conductive particles are inorganic fillers with a conductive coating layer on the surface, the conductive coating layer provides a good conductive network for the protective layer, and the excellent dispersibility of the inorganic filler itself provides the conductive particles with good dispersibility. This can further enhance the physical isolation and conductive properties of the protective layer.
  • the conductive coating layer has conductivity and is composed of a conductive material. At least a portion of the conductive coating layer constitutes the outermost layer of the conductive particles, and the conductive coating layer only needs to cover at least a portion of the inorganic filler. In order to obtain better conductive properties, the higher the coverage, the better.
  • the conductive coating layer includes at least one of tin oxide, indium oxide, ATO, FTO, ITO, AZO and carbon materials, preferably at least one of ATO, FTO, ITO and AZO, and more preferably ATO.
  • ATO refers to antimony-doped tin dioxide, wherein the antimony doping amount is 0 to 30%;
  • FTO refers to fluorine-doped tin dioxide, wherein the fluorine doping amount is 0 to 10%;
  • ITO refers to tin-doped indium oxide, wherein the tin doping amount is 0 to 30%;
  • AZO is aluminum-doped zinc oxide, wherein the aluminum doping amount is ⁇ 20%.
  • the inorganic filler has the characteristics of high mechanical strength, good stability and good heat resistance.
  • the present application does not limit the specific type of the inorganic filler.
  • the inorganic filler includes at least one of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium iron manganese phosphate.
  • the lithium-ion battery can be further guaranteed to have both good conductivity and safety performance.
  • the conductive coating layer accounts for 2% to 40% of the mass content of the conductive particles, the battery has relatively balanced safety performance and cycle performance.
  • the present application does not specifically limit the type of adhesive, as long as it can ensure effective bonding between the protective layer and the current collector.
  • the adhesive includes at least one of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene butadiene rubber, and styrene acrylic rubber.
  • the present application also limits the content of conductive particles and the content of adhesive in the first protective layer and the second protective layer.
  • the thickness of the first protective layer and the second protective layer independently include 40% to 98% conductive particles, 2% to 30% adhesive and 0% to 40% non-conductive particles according to the mass content.
  • the protective layer in addition to the conductive particles and the adhesive, can also be made conductive by adding other conductive agents or non-conductive agents to adjust the conductivity of the protective layer.
  • Non-conductive agents such as alumina ceramics are used to reduce the conductivity of the protective layer, and conductive agents such as carbon nanotubes are added to increase the conductivity of the protective layer. It should be noted that the above additional additives are not necessary for the protective layer of the present application.
  • the functional electrode sheets in the electrode sheet assembly are negative electrode sheets and/or positive electrode sheets
  • the electrode sheets of the protection assembly are negative electrode sheets and/or positive electrode sheets.
  • all functional electrode sheets 101 in the electrode sheet assembly 1 are positive electrode sheets
  • the composition of the negative electrode sheets 102 in the electrode sheet assembly can refer to conventional negative electrode sheets in the art
  • the protection components 2 are all positive electrode sheets.
  • the present application does not limit the material of the active layer, and the active layer may include active substances, conductive agents, adhesives and other components according to conventional compositions in the art.
  • the active substances, conductive agents, adhesives and other components may be conventional materials in the art.
  • the positive electrode active material includes one or more of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide;
  • the conductive agent includes one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene;
  • the adhesive includes one or more of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber, and styrene-propylene rubber.
  • PVDF polyvinylidene fluoride
  • the functional electrode sheet of the present application can be prepared by conventional technical means in the field. Specifically, the raw materials constituting the first protective layer can be uniformly dispersed in a solvent to obtain a protective layer slurry, the raw materials constituting the active layer can be uniformly dispersed in a solvent to obtain an active layer slurry, and then the protective layer slurry is coated on at least one surface of the first current collector, and the first protective layer is obtained after drying, and then the active layer slurry is coated on the first protective layer, and dried to obtain the functional electrode sheet of the present application.
  • the present application does not specifically limit the coating method, and any coating method such as gravure coating, extrusion coating, spraying, screen printing, etc. can be used to coat the protective layer slurry and the active layer slurry.
  • the lithium-ion battery provided in the present application includes the above-mentioned laminated battery core, wherein the lithium-ion battery can be prepared by conventional methods in the art.
  • the laminated battery core can be subjected to processes such as baking, liquid injection, formation, and packaging to obtain the above-mentioned lithium-ion battery.
  • the present application provides a first protective layer and a second protective layer to physically isolate the battery when it is mechanically damaged, so that the current collectors in the electrode sheet assembly and the protective assembly are not easily exposed, and the current collectors in the laminated battery core are prevented from contacting the active layer or current collector of the adjacent electrode sheet, thereby reducing the possibility of short circuit and significantly improving the safety performance of the battery.
  • the protective layer and the second protective layer are conductive, which can ensure smooth electronic conduction between the active layer and the current collector, so that the battery has excellent safety performance and good cycle performance.
  • the lithium-ion battery of the present application because it includes the above-mentioned positive electrode sheet, also has excellent safety performance and good cycle performance.
  • the electrode sheet peeling force test method is as follows: the positive electrode sheet is cut into a positive electrode sheet small piece with a length of 240 mm and a width of 30 mm, and the tape is cut into tape small pieces according to the specifications of a length of 200 mm and a width of 24 mm using NITTO No. 5000NS tape, and one side of the tape small piece is glued to a steel plate (260 mm*50 mm), and the positive electrode sheet is glued to the other side of the tape small piece, ensuring that the positive electrode sheet is small.
  • the positive electrode sheet is completely covered with the tape sheet, and a hand-held roller (diameter 95mm, width 45mm, weight 2kg) is used to roll back and forth 3 times to bond the positive electrode sheet and the tape sheet together, and then a tensile testing machine (tensile testing machine model Dongguan Kejian KJ-1065 series) is used for testing (180-degree peeling).
  • the testing equipment automatically records the tensile force value that changes with the peeling displacement, and draws a curve of the tensile force value changing with the peeling displacement.
  • the horizontal axis is the peeling displacement
  • the vertical axis is the tensile force value.
  • the tensile force value when the curve is flat and the peeling displacement is greater than 5mm is the peeling force;
  • peeling force between the protective layer and the current collector is greater than the peeling force between the protective layer and the active material layer
  • peeling usually occurs at the interface between the active material and the protective layer.
  • this test phenomenon also shows that the peeling force between the protective layer and the current collector is greater than the peeling force between the protective layer and the active material layer.
  • the method for determining the resistivity of the conductive particles is as follows: the resistivity of the conductive particles is tested using a powder resistance tester, and the test pressure of the powder is set to 20KN;
  • the method for determining the average particle size of the conductive particles is as follows: Use a laser particle size tester to test the particle size distribution of the conductive particles, and calculate the particle size from small to large. The volume of the particles and the particle size corresponding to 50% of the total volume are the average particle size.
  • step 3 coating the positive electrode protective layer slurry prepared in step 1) on two functional surfaces of an aluminum foil (thickness of 9 ⁇ m) and drying to obtain a first protective layer, and then coating the positive electrode active layer slurry prepared in step 2) on the first protective layer to obtain a functional electrode sheet;
  • step 1) coating the positive electrode protective layer slurry prepared in step 1) on two functional surfaces of an aluminum foil (thickness of 9 ⁇ m), drying to obtain a second protective layer, and then coating the positive electrode active layer slurry prepared in step 2) on the second protective layer on one surface to obtain a protective component;
  • 96wt% of artificial graphite, 1wt% of carbon black, 1.5wt% of styrene-butadiene rubber, and 1.5wt% of sodium carboxymethyl cellulose are mixed, deionized water is added, and a negative electrode active layer slurry with a solid content of 40% is obtained after stirring; the negative electrode slurry is coated on the upper and lower surfaces of a copper foil (thickness of 5 ⁇ m) by an extrusion coating process, and dried to obtain a negative electrode sheet;
  • the functional electrode sheet, the separator, and the negative electrode sheet are stacked in sequence to obtain an electrode sheet assembly, and then the protective assembly, the separator, the electrode sheet assembly, the separator, and the protective assembly are stacked in sequence, and fixed with adhesive tape to obtain a laminated battery cell;
  • the positive electrode active layer on the protective assembly is close to the electrode sheet assembly
  • the battery cell is sealed for a second time and folded to obtain the lithium-ion battery of this embodiment.
  • step 5 "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 2 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 2 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 1 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 1 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 the "single-side thickness of the first protective layer is rolled to 3 ⁇ m, and the single-side thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by The condition is changed to "the thickness of one side of the first protective layer is rolled to 4 ⁇ m, and the thickness of one side of the second protective layer is rolled to 4 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 5 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 5 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 2 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • Example 1 Compared with Example 1, in the preparation of the positive electrode sheet, in step 5), "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 2 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 5 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • the "single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 2 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 8 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 1 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 Compared with Example 1, in the preparation of the positive electrode sheet, in step 5), "the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by “the single-sided thickness of the second protective layer is rolled to 2 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 15 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 15 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 1) "95wt% ATO-coated TiO2 as conductive particles (ATO accounts for 10% of the conductive particles) and 5wt% PVDF mixed” is replaced by "30wt% ATO-coated TiO2 , 60% TiO2 as conductive particles (ATO accounts for 10% of the conductive particles) and 10wt% PVDF mixed", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 4) is replaced by "coating the positive electrode active layer slurry prepared in step 2) on an aluminum foil (with a thickness of 9 ⁇ m) to obtain a protective component".
  • step 5 the “single-side thickness of the first protective layer is rolled to 3 ⁇ m, and the single-side thickness of the second protective layer is rolled to 3 ⁇ m” in Example 1 is replaced by “single-side thickness of the first protective layer is rolled to 3 ⁇ m”, and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • steps 3), 4), and 5 are replaced by "coating the positive electrode active layer slurry prepared in step 2) on two functional surfaces of an aluminum foil (with a thickness of 9 ⁇ m), drying, and obtaining a positive electrode sheet; rolling the positive electrode sheet using a roller press to roll the single-side thickness of the active layer to 45 ⁇ m;
  • the functional electrode sheet and the protection component are replaced with the positive electrode sheet prepared in this embodiment.
  • step 1) Compared with Example 1, in the preparation of the positive electrode sheet, in step 1), "ATO-coated TiO 2 as conductive particles" in Example 1 is replaced with “ATO as conductive particles", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 5 "the single-sided thickness of the first protective layer is rolled to 3 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 3 ⁇ m" in Example 1 is replaced by "the single-sided thickness of the first protective layer is rolled to 0.5 ⁇ m, and the single-sided thickness of the second protective layer is rolled to 0.5 ⁇ m", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • step 1) "95wt% ATO-coated TiO2 as conductive particles (ATO accounts for 10% of the conductive particles) and 5wt% PVDF mixed” is replaced by "95wt% ATO-coated TiO2 as conductive particles (ATO accounts for 60% of the conductive particles) and 5wt% PVDF mixed", and the other conditions remain unchanged;
  • the functional electrode sheets and the protective components are replaced with the functional electrode sheets and the protective components prepared in this embodiment.
  • the lithium-ion batteries of the above embodiments and comparative examples were tested for needle puncture pass rate, screw extrusion pass rate, capacity retention rate, and energy density.
  • the test methods are as follows:
  • Test method Fully charge the lithium-ion battery, then place it on the test bench of the needle puncture test equipment, and pierce the battery from the middle of the battery at a speed of 100mm/s with a tungsten steel needle with a diameter of 3mm and a needle tip length of 3.62mm. If the battery does not catch fire or explode, the test is considered to have passed.
  • the number of passes/the number of tests is the needle puncture pass rate, and the number of tests is 30.
  • Test method fully charge the lithium-ion battery, then put it on the test bench of the extrusion equipment, put the M2*4 (screw diameter is 2mm, screw length is 4mm) screw in the middle of the battery, then start the extrusion equipment, the extrusion plate presses down at a speed of 100mm/s, and the test is stopped when the extrusion force reaches 13KN.
  • the battery is considered to have passed the test if it does not catch fire or explode.
  • the number of passes/tested number is the screw test pass rate, and the number of tests is 30.
  • Test method At 45°C, charge and discharge the lithium-ion battery at a rate of 1.5C charge/0.5C discharge, and record the discharge capacity Q2 of the 500th charge and discharge and the discharge capacity Q1 of the first charge and discharge.
  • the capacity retention rate Q2/Q1 ⁇ 100%.
  • Test method Charge the lithium-ion battery to an upper voltage of 4.45V, then discharge it at 0.2C to a lower voltage of 3.0V. The discharge energy is recorded as E. Then calculate the energy density of the lithium-ion battery using the following formula:
  • Energy density E/(length ⁇ width ⁇ height of lithium-ion battery).
  • Example 1 By comparing Example 1 with Examples 9 and 10, it can be seen that when the thickness of the second protective layer is less than that of the first protective layer, the safety will be reduced. When the thickness of the first protective layer remains unchanged, as the thickness of the second protective layer increases, the safety performance of the battery is also significantly improved. 7 and 8, it can be seen that when the thickness of the second protective layer is greater than or equal to the thickness of the first protective layer, the safety will be improved. When the thickness of the first protective layer remains unchanged, as the thickness of the second protective layer increases, the safety performance of the battery is also significantly improved.
  • Example 1 By comparing Example 1 and Comparative Example 3, it can be seen that the use of an inorganic filler having a conductive coating layer as a conductive material can further reduce the probability of short circuit between the positive electrode current collector and the negative electrode active layer, improve the safety performance of the battery, and at the same time have good cycle performance.
  • Example 1 By comparing Example 1 and Comparative Example 4, it can be seen that as the thickness of the protective layer increases, the safety performance of the lithium-ion battery can be improved accordingly.
  • the thickness of the protective layer does not exceed 0.5 ⁇ m, it is difficult to achieve the protective effect.
  • Example 1 By comparing Example 1 with Comparative Example 5, it can be seen that when the conductive coating layer accounts for 2% to 40% of the mass content of the conductive particles, the battery has relatively balanced safety performance and cycle performance.

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Abstract

本申请提供一种叠片电芯及锂离子电池，该叠片电芯包括电极片组件和保护组件，所述保护组件位于所述电极片组件外侧极片的表面；所述电极片组件中包括至少一个功能电极片，所述功能电极片包括第一集流体、第一保护层和活性层，所述第一保护层位于所述第一集流体和活性层之间；所述保护组件包括第二集流体和第二保护层，且所述第二保护层远离所述电极片组件；所述第一保护层、第二保护层各自独立的包括导电颗粒和粘结剂，可避免锂离子电池在机械滥用时内部发生短路，使锂离子电池具有优异的安全性能。

Description

叠片电芯及锂离子电池
本申请要求于2022年10月24日提交中国专利局、申请号为202211304492.4、申请名称为“叠片电芯及锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请属于锂离子电池领域，具体涉及一种叠片电芯及锂离子电池。
背景技术
锂离子电池在应用于实际场景之前，必须经过机械滥用测试。其中，机械滥用测试是指检测电池在模拟极端条件下的性能，例如挤压测试、针刺测试等。锂离子电池在机械滥用测试时失效概率很高，原因在于电池在受到机械破坏的情况下，内部会发生较为严重的短路，例如集流体与相邻电极片的集流体接触发生短路，活性层与相邻电极片的活性层接触发生短路，集流体与相邻电极片的活性层接触发生短路，引发热失控。因此，如何改善锂离子电池的安全性能是本领域亟待解决的技术问题。
发明内容
本申请提供一种叠片电芯，该叠片电芯通过第一保护层和第二保护层的设置，可避免锂离子电池在机械滥用时内部发生短路，使锂离子电池具有优异的安全性能。
本申请还提供一种锂离子电池，该电池由于包括上述叠片电芯，因此具有良好的安全性能。
本申请的一方面，提供一种叠片电芯，包括电极片组件和保护组件，保护组件位于电极片组件外侧极片的表面；电极片组件中包括至少一个功能电极片，功能电极片包括第一集流体、第一保护层和活性层，第一保护层位于第一集流体和活性层之间；保护组件包括第二集流体和第二保护层，且第二保护层远离电极片组件；第一保护层、第二保护层各自独立的包括导电颗粒 和粘结剂；导电颗粒为表面具有导电包覆层的无机填料，其中，导电包覆层占导电颗粒的质量含量为2％～40％，第一保护层的厚度、第二保护层的厚度各自大于0.5μm。
根据本申请的一实施方式，导电包覆层至少一部分构成导电颗粒的最外层。
根据本申请的一实施方式，导电包覆层被覆至少一部分的无机填料。
根据本申请的一实施方式，第一保护层的厚度为A，第二保护层的厚度为B，A≤B。
根据本申请的一实施方式，第一保护层的厚度、第二保护层的厚度各自独立的为1μm～10μm。
根据本申请的一实施方式，第一保护层、第二保护层各自独立的按照质量含量包括40％～98％的导电颗粒、2％～30％的粘接剂以及0％～40％的非导电颗粒。
根据本申请的一实施方式，第一保护层、第二保护层各自独立的电阻为10～2000mΩ；和/或，导电颗粒的电阻率为1～100Ω·cm；和/或，导电颗粒的平均粒径为0.05～5μm。
根据本申请的一实施方式，导电包覆层包括氧化锡、氧化铟、ATO、FTO、ITO、AZO、碳材料中的至少一种。其中，ATO是指锑掺杂二氧化锡、FTO是指氟掺杂二氧化锡、ITO是指锡掺杂氧化铟、AZO为铝掺杂的氧化锌。根据本申请的一实施方式，无机填料包括氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁、磷酸铁锂、镍钴锰酸锂、磷酸铁锰锂中的至少一种。
本申请的第二方面，提供一种锂离子电池，包括上述的叠片电芯。
本申请的实施，至少具有以下有益效果：
本申请中提供的叠片电芯，第一保护层和第二保护层起到物理隔绝的作用，使电极片的集流体不容易裸露出来，避免电芯内部集流体与相邻电极片的活性层或集流体接触，进而降低短路概率，显著提升电池的安全性能。同时导电颗粒能够保证保护层的导电性能，从而使电池在获得优异安全性能的同时兼具良好的循环性能。
本申请提供的锂离子电池，包括上述叠片电芯，具有良好的安全性能和 循环性能。
附图说明
图1是本申请一实施例的叠片电芯的结构示意图；
图2是沿着图1所示的切割线a所在的平面切割得到的叠片电芯的剖面结构示意图；
图3是本申请一实施例的功能电极片的结构示意图；
图4是本申请一实施例的保护组件的结构示意图；
图5是本申请另一实施例的保护组件的结构示意图。
附图标记说明：
1-电极片组件；
2-保护组件；
101-功能电极片；
102-负极片；
103-隔膜；
104-正极耳；
105-负极耳；
1011-第一集流体；
1012-第一保护层；
1013-活性层；
2011-第二集流体；
2012-第二保护层；
2013-第二活性层。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合本申请的实施例和附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所 获得的所有其他实施例，都属于本申请保护的范围。
请参照图1至图5，本申请提供的叠片电芯，包括电极片组件1和保护组件2，保护组件2位于电极片组件1外侧极片的表面；电极片组件1中包括至少一个功能电极片101，功能电极片101包括第一集流体1011、第一保护层1012和活性层1013，第一保护层1012位于第一集流体1011和活性层1013之间；保护组件2包括第二集流体2011和第二保护层2012，且第二保护层2012远离电极片组件1；第一保护层1012、第二保护层2012各自独立的包括导电颗粒和粘结剂。
本申请中，叠片电芯包括层叠设置的电极片组件1和保护组件2，电极片组件1在叠片电芯的层叠方向上具有相对的两个外侧，保护组件2位于电极片组件1的外侧。
保护组件2的数量为一个或两个。根据保护组件2的数量，选择在电极片组件1的一侧或两侧设置保护组件2，例如当保护组件2的数量为一个时，该保护组件2位于电极片组件1的任意一个外侧；当保护组件2的数量为两个时，这两个保护组件2分设在电极片组件1的两个外侧。保护组件2能起到保护电极片组件的作用，保护组件2与电极片组件1之间通过隔膜103隔开。
本申请电极片组件包括依次层叠设置的电极片，电极片之间通过隔膜103隔开。根据是否设置第一保护层101将电极片分为功能电极片和非功能电极片，功能电极片101的数量为一个或多个。每个功能电极片101均包括第一集流体1011，第一集流体1011具有两个最大的表面，在最大的表面上设置第一保护层1012和活性层1013。非功能电极片的集流体上只设置活性层，不设置保护层。
在功能电极片101中，活性层1013是单面设置或双面设置，相应地，第一保护层1012是单面设置或双面设置，满足第一保护层1012位于活性层1013和第一集流体1011之间即可。
保护组件2包括第二集流体2011，第二集流体2011具有两个最大的表面，在最大的表面上设置第二保护层2012。第二保护层2012位于第二集流体2011远离电极片组件1的表面上。为了进一步提高电池的容量，可以选择在第二集流体2011靠近电极片组件1的表面上涂覆第二活性层 2013。此时，第二活性层2013与第二集流体2011之间也可以设置第二保护层。
第一保护层1012、第二保护层2012各自独立的包括导电颗粒和粘结剂以及0％～40％的非导电颗粒，优选地，第一保护层1012、第二保护层2012由导电颗粒和粘结剂组成。导电颗粒赋予第一保护层1012和第二保护层2012良好的导电网络。粘接剂能够保证第一保护层1012、第二保护层2012固定粘接于第一集流体1011和第二集流体2011上。
申请人经研究发现，第一保护层1012和第二保护层2012能够在电池遭受机械破坏时，起到物理隔绝的作用，使电极片组件1和保护组件2中的集流体不容易裸露出来，避免叠片电芯内部集流体与相邻电极片的活性层或集流体接触，从而降低短路的可能性，显著提升电池的安全性能。同时导电颗粒使第一保护层1012和第二保护层2012具有导电性，能够保证活性层与集流体之间的电子导通顺畅，从而使电池在获得优异安全性能的同时兼具良好的循环性能。
为了进一步提高电池的容量，可以选择在第二集流体2011靠近电极片组件1的表面上涂覆第二活性层2013。此时，第二活性层2013与第二集流体2011之间也可以设置第二保护层。
本申请对第一保护层1012与第一集流体1011之间的剥离力、第一保护层1012与第一活性层1013之间的剥离力不作限定，可以根据实际需求调整。在一种优选实施方式中，第一保护层1012与第一集流体1011之间的剥离力大于第一保护层1012与第一活性层1013之间的剥离力，可进一步减小第一集流体1011与第一活性层1013接触导致电池短路的可能性。
通过调整第一保护层1012和第一活性层1013中粘接剂的种类和数量，可以控制第一保护层1012与第一集流体1011之间的剥离力的大小以及第一保护层1012与第一活性层1013之间的剥离力的大小。
具体地，当第一保护层1012和第一活性层1013中粘接剂的种类相同时，通过控制第一保护层1012的粘接剂的含量大于第一活性层1013中的粘接剂的含量，从而实现第一保护层1012与第一集流体1011之间的剥离力大于第一保护层1012与第一活性层1013之间的剥离力。
当第一保护层1012与第一活性层1013中的粘接剂的含量相同时，通 过选择粘接力相对更强的粘接剂加入第一保护层1012中，粘接力相对更弱的粘接剂加入第一活性层1013中，从而实现第一保护层1012与第一集流体1011之间的剥离力大于第一保护层1012与第一活性层1013之间的剥离力。
本申请对第一保护层1012和第二保护层2012的厚度不作限定，具体可以根据实际情况调整，在一种优选实施方式中，第一保护层1012的厚度为A，第二保护层2012的厚度为B，满足A≤B，更有利于提升电池的安全性。
随着第一保护层1012、第二保护层2012厚度的增加，锂离子电池的安全性能也能够得到相应提升，但同时也会导致电池体积能量密度的相应下降，为了兼顾锂离子电池的安全性能和体积能量密度，在一种优选实施方式中，第一保护层1012的厚度、第二保护层2012的厚度各自独立的为1μm～10μm，优选为2μm～5μm。
本申请中，第一保护层1012、第二保护层2012的设置可能会导致电池阻抗的增加，为了避免电池阻抗的增加，申请人研究发现，当第一保护层1012、第二保护层2012各自独立的电阻为10mΩ～2000mΩ，进一步优选为100mΩ～1000mΩ时，电池仍然能够保持良好的循环性能。其中，第一保护层1012、第二保护层2012各自的电阻是指通过第一保护层1012、第二保护层2012各自厚度的电阻值。
通过选择不同电阻率的导电颗粒、控制导电颗粒在第一保护层1012、第二保护层2012中所占的含量等能够实现对第一保护层1012、第二保护层2012的电阻的控制。
在一些实施例中，可以通过控制导电颗粒的种类和粒径，控制导电颗粒的电阻率为1～100Ω·cm。
为了实现第一保护层1012、第二保护层2012在集流体上的涂覆，且能够使导电颗粒更加致密的分布于第一保护层1012、第二保护层2012上，使锂离子电池兼具良好的能量密度和安全性能，本申请导电颗粒的平均粒径Dv50为0.05～5μm，优选为0.1～1μm。
导电颗粒含有导电性物质，当导电性物质含量较少时，不利于电池的循环性能；当导电性物质含量较多时，容易发生团聚，难以在保护层中分 散均匀。申请人经研究发现，当导电颗粒为表面包覆有导电包覆层的无机填料时，导电包覆层赋予了保护层良好的导电网络，无机填料自身优异的分散性能赋予了导电颗粒良好的分散性能。这样能够进一步保护层的物理隔绝作用和导电性能。
具体地，导电包覆层具有导电性，由导电性物质所构成。导电包覆层至少一部分构成导电颗粒的最外层，导电包覆层只要被覆至少一部分的无机填料即可。为了得到较优良的导电特性，被覆率越高越好。
其中，导电包覆层包括氧化锡、氧化铟、ATO、FTO、ITO、AZO、碳材料中的至少一种，优选为ATO、FTO、ITO、AZO中的至少一种，进一步优选为ATO。其中，ATO是指锑掺杂二氧化锡，其中锑的掺杂量0～30％；FTO是指氟掺杂二氧化锡，氟的掺杂量0～10％；ITO是指锡掺杂氧化铟，锡的掺杂量0～30％；AZO为铝掺杂的氧化锌，铝的掺杂量≤20％。
无机填料具有机械强度高、稳定性好、耐热性好的特点，本申请对无机填料的具体种类不作限定，在一种优选实施方式中，无机填料包括氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁、磷酸铁锂、镍钴锰酸锂、磷酸铁锰锂中的至少一种。
通过控制导电包覆层占导电颗粒的质量含量，能够进一步保证锂离子电池兼具良好的导电性和安全性能。在一种优选实施方式中，当导电包覆层占导电颗粒质量含量的2％～40％时，电池具有较为均衡的安全性能和循环性能。
本申请对粘接剂的种类不作特殊限定，只要能够保证保护层与集流体有效粘接即可。在一种优选实施方式中，粘接剂包括聚偏氟乙烯(PVDF)、丙烯酸改性PVDF、聚丙烯酸酯类聚合物、聚酰亚胺、丁苯橡胶、苯丙橡胶中的至少一种。
综合考虑锂离子电池的安全性能和循环性能，本申请也对第一保护层和第二保护层中各自的导电颗粒的含量与粘接剂的含量进行限定，具体的，第一保护层的厚度、第二保护层各自独立的按照质量含量包括40％～98％的导电颗粒和2％～30％的粘接剂以及0％～40％的非导电颗粒。
本申请中，保护层除了包括导电颗粒和粘接剂以外，还可以通过额外添加其他导电剂或者非导电剂来调节保护层导电性的强弱，例如额外增加 非导电剂如氧化铝陶瓷来降低保护层的导电性，额外增加导电剂如碳纳米管来增加保护层的导电性。需要说明的是，以上额外添加物对于本申请的保护层来讲不是必要的。
本申请中，电极片组件中的功能电极片是负极片和/或正极片，保护组件的电极片是负极片和/或正极片。
在如图2所示的一种实施方式中，电极片组件1中所有功能电极片101均是正极片，电极片组件中的负极片102的组成可参考本领域的常规负极片，保护组件2均是正极片。
本申请对活性层的材料不作限定，可按照本领域的常规组成包括活性物质、导电剂、粘接剂等组分。其中，活性物质、导电剂、粘接剂等组分都可以选用本领域的常规物质。
以正极片为例，正极活性物质包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂、锰酸锂中的一种或多种，导电剂包括导电炭黑、碳纳米管、导电石墨、石墨烯中的一种或多种，粘接剂包括聚偏氟乙烯(PVDF)、丙烯酸改性PVDF、聚丙烯酸酯类聚合物、聚酰亚胺、丁苯橡胶、苯丙橡胶中的一种或多种。
本申请的功能电极片可采用本领域常规技术手段制备得到，具体的，可将组成第一保护层的原料在溶剂中均匀分散得到保护层浆料，将组成活性层的原料在溶剂中均匀分散得到活性层浆料，然后将保护层浆料涂布于第一集流体的至少一个表面，干燥后得到第一保护层，再将活性层浆料涂布于第一保护层上，干燥即可得到本申请的功能电极片。
本申请对涂布的方式不作具体限定，可以采用凹版涂布、挤压涂布、喷涂、丝网印刷等任意一种涂布方式实现保护层浆料和活性层浆料的涂布。
本申请提供的锂离子电池，包括上述叠片电芯，其中，锂离子电池可以采用本领域常规方法制备得到，具体的，可将叠片电芯再经过烘烤、注液、化成、封装等工序即可得到上述锂离子电池。
本申请通过设置第一保护层和第二保护层，能够在电池遭受机械破坏时，起到物理隔绝的作用，使电极片组件和保护组件中的集流体不容易裸露出来，避免叠片电芯内部集流体与相邻电极片的活性层或集流体接触，从而降低短路的可能性，显著提升电池的安全性能。同时导电颗粒使第一 保护层和第二保护层具有导电性，能够保证活性层与集流体之间的电子导通顺畅，从而使电池在获得优异安全性能的同时兼具良好的循环性能
本申请的锂离子电池，由于包括上述正极片，因此也具有优异的安全性能和良好的循环性能。
为使本申请的目的、技术方案和优点更加清楚，下面将结合本申请的实施例，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
以下，通过具体实施例和对比例对本申请提供的正极片及锂离子电池进行详细的介绍，其中极片剥离力测试方法如下：将正极片裁切成长度240mm、宽度30mm的正极片小片，使用NITTO No.5000NS胶带，将胶带按照长度200mm、宽度24mm的规格裁切成胶带小片，将胶带小片的一面粘在钢板(260mm*50mm)上，将正极片小片粘在胶带小片的另一面上，保证正极片小片完全覆盖住胶带小片，使用手持滚筒(直径95mm，宽度45mm，重量2kg)往复滚动3次，将正极片小片与胶带小片粘接在一起，然后使用拉力机(拉力机型号东莞科建KJ-1065系列)测试(180度剥离)，测试设备自动记录随着剥离位移变化的拉力值，作出拉力值随剥离位移变化的曲线，横坐标为剥离位移，纵坐标为拉力值，取曲线走平且剥离位移大于5mm时的拉力值即为剥离力；
由于保护层与集流体之间的剥离力大于保护层与活性物质层之间的剥离力，因此正极片进行剥离力测试时，通常是活性物质与保护层的界面出现剥离，但是这一测试现象也说明了保护层与集流体之间的剥离力大于保护层与活性物质层之间的剥离力；
保护层的电阻率的测定方法如下：将正极集流体放置于体相电阻仪上，电阻仪的探针直径为15mm，测定出正极集流体的电阻为R1，再将带有正极保护层的正极集流体放置于体相电阻仪上，测定出正极保护层和正极集流体的整体电阻R2，其中，正极保护层的电阻R＝R2-R1；
导电颗粒电阻率的测定方法如下：采用粉末电阻测试仪测试导电颗粒的电阻率，设置粉末的测试压力为20KN；
导电颗粒的平均粒径的测定方法如下：使用激光粒度测试仪测试导电颗粒的粒径分布，取粒径其从小到大开始计算，颗粒的体积和占总体积为50％时对应的粒径数值为平均粒径。
实施例1
本实施例叠片电芯及锂离子电池的制备包括以下步骤：
1、正极片的制备
1)将95wt％ATO包覆的TiO2作为导电颗粒(ATO在导电颗粒中的占比为10％)和5wt％的PVDF混合，加入NMP，经过搅拌得到固含量为40％的正极保护层浆料；
2)将96wt％的钴酸锂、1wt％的炭黑、1wt％的碳纳米管、2wt％的PVDF混合，加入NMP，经过搅拌得到固含量为70％的正极活性层浆料；其中，ATO包覆的TiO2的平均粒径为0.4μm。
3)将步骤1)制备得到的正极保护层浆料涂覆在铝箔(厚度为9μm)的两个功能表面上，干燥，得到第一保护层，再向第一保护层上涂覆步骤2)制备得到的正极活性层浆料，得到功能电极片；
4)将步骤1)制备得到的正极保护层浆料涂覆在铝箔(厚度为9μm)的两个功能表面上，干燥，得到第二保护层，再在一个表面的第二保护层涂覆步骤2)制备得到的正极活性层浆料，得到保护组件；
5)使用辊压机对功能电极片、保护组件进行辊压，使功能电极片上的第一保护层的单面厚度辊压至3μm，使保护组件上的第二保护层的单面厚度辊压至3μm，活性层的单面厚度辊压至45μm，再使用分条机对功能电极片、保护组件进行分切，最后在功能电极片、保护组件上焊接正极耳104并贴上保护胶纸。
2、负极片的制备
将96wt％的人造石墨、1wt％的炭黑、1.5wt％的丁苯橡胶、1.5wt％质量的羧甲基纤维素钠混合，加入去离子水，经过搅拌得到固含量为40％，的负极活性层浆料；将负极浆料通过挤压涂布的工艺涂覆在铜箔(厚度为5μm)的上下两个表面，烘干得到负极片；
使用辊压机对负极片进行辊压，再使用分条机对负极片进行分切，最 后在负极片上焊接负极耳105并贴上保护胶纸。
3、叠片电芯的制备
按照功能电极片、隔膜、负极片依次进行层叠设置，得到电极片组件，再按照保护组件、隔膜、电极片组件、隔膜、保护组件的次序进行层叠设置，并贴上胶纸固定，得到叠片电芯；
其中保护组件上的正极活性层靠近电极片组件；
4、锂离子电池的制备
1)使用冲型模具将铝塑膜进行冲型，然后使用冲型的铝塑膜将叠片电芯封装起来，得到电芯，烘烤至水分合格，注入电解液；
2)使用锂离子电池化成设备，对电芯进行充放电，使电芯硬化，并分选出电芯的容量；
3)对电芯进行二次封口，并进行折边，即得到本实施例的锂离子电池。
实施例2
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至2μm，第二保护层的单面厚度辊压至2μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例3
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至1μm，第二保护层的单面厚度辊压至1μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例4
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替 换为“第一保护层的单面厚度辊压至4μm，第二保护层的单面厚度辊压至4μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例5
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至5μm，第二保护层的单面厚度辊压至5μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例6
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至2μm，第二保护层的单面厚度辊压至3μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例7
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至2μm，第二保护层的单面厚度辊压至5μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例8
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至2μm，第二保护层的单面厚度辊压至8μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例9
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至1μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例10
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第二保护层的单面厚度辊压至3μm”替换为“第二保护层的单面厚度辊压至2μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例11
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至15μm，第二保护层的单面厚度辊压至15μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
实施例12
与实施例1相比，在正极片的制备中，步骤1)中，将“95wt％ATO包覆的TiO2作为导电颗粒(ATO在导电颗粒中的占比为10％)和5wt％的PVDF混合”替换为“30wt％ATO包覆的TiO2、60％TiO2作为导电颗粒(ATO在导电颗粒中的占比为10％)和10wt％的PVDF混合”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
对比例1
与实施例1相比，在正极片的制备中，将步骤4)替换为“将步骤2)制备得到的正极活性层浆料涂覆在铝箔(厚度为9μm)，得到保护组件”，
步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至3μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
对比例2
与实施例1相比，在正极片的制备中，将步骤3)、4)、5)替换为“将步骤2)制备得到的正极活性层浆料涂覆在铝箔(厚度为9μm)的两个功能表面上，干燥，得到正极片；使用辊压机对正极片进行辊压，使活性层的单面厚度辊压至45μm；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的正极片。
对比例3
与实施例1相比，在正极片的制备中，步骤1)中，将实施例1中“ATO包覆的TiO2作为导电颗粒”替换为“ATO作为导电颗粒”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
其余同实施例1。
对比例4
与实施例1相比，在正极片的制备中，步骤5)中，将实施例1中“第一保护层的单面厚度辊压至3μm，第二保护层的单面厚度辊压至3μm”替换为“第一保护层的单面厚度辊压至0.5μm，第二保护层的单面厚度辊压至0.5μm”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
对比例5
与实施例1相比，在正极片的制备中，步骤1)中，将“95wt％ATO包覆的TiO2作为导电颗粒(ATO在导电颗粒中的占比为10％)和5wt％的PVDF混合”替换为“95wt％ATO包覆的TiO2作为导电颗粒(ATO在导电颗粒中的占比为60％)和5wt％的PVDF混合”，其余条件不变；
在叠片电芯的制备中，将功能电极片、保护组件替换为本实施例制备得到的功能电极片、保护组件。
对以上实施例和对比例的锂离子电池进行针刺通过率、螺丝挤压通过率、容量保持率、能量密度的测试，测试方法如下：
a、针刺通过率
测试方法：将锂离子电池充满电，然后将其放入针刺测试设备的测试台上，将直径为3mm，针尖长度为3.62mm的钨钢针，以100mm/s的速度从电池的中间部位刺过并刺穿电池，电池不起火、不爆炸视为测试通过。通过数量/测试数量即为针刺通过率，测试数量为30个。
b、螺丝挤压通过率
测试方法：将锂离子电池充满电，然后将其放入挤压设备的测试台上，将M2*4(螺杆直径为2mm，螺杆长度为4mm)的螺丝置于电池中间，然后启动挤压设备，挤压板以100mm/s的速度下压，当其挤压力达到13KN停止测试，电池不起火、不爆炸视为测试通过。通过数量/测试数量即为螺丝测试通过率，测试数量为30个。
c、容量保持率
测试方法：在45℃下，使锂离子电池以1.5C充电/0.5C放电的倍率进行充放电，记录其第500次充放电的放电容量Q2与第1次的充放电的放电容量Q1，容量保持率＝Q2/Q1×100％。
d、能量密度
测试方法：将锂离子电池充电至上限电压4.45V，然后以0.2C放电至下限电压3.0V，放电能量记为E，然后通过以下公式计算出锂离子电池的能量密度：
能量密度＝E/(锂离子电池的长度×宽度×高度)。
具体测试结果如表1和表2所示：
表1
表2
由表1和表2可知，对比实施例1～12与对比例1和2可以看出，加入第一保护层和第二保护层能够明显提升电池的安全性能。
对比实施例1与实施例9、10可以看出，当第二保护层小于第一保护层的厚度时，安全性会有所降低。当第一保护层的厚度不变时，随着第二保护层的厚度增加，电池的安全性能也有明显的提升。对比实施例2和实施例6、 7、8可以看出，当第二保护层大于等于第一保护层的厚度时，安全性会有所提升。当第一保护层的厚度不变时，随着第二保护层的厚度增加，电池的安全性能也有明显的提升。
对比实施例1和对比例3可以看出，采用具有导电包覆层的无机填料作为导电材料，能够进一步降低正极集流体与负极活性层的短路几率，提升电池的安全性能，同时兼具良好的循环性能。
对比实施例1和对比例4可以看出，随着保护层厚度的增加，锂离子电池的安全性能也能够得到相应提升，当保护层厚度不超过0.5μm，难以实现保护的作用。
对比实施例1和对比例5可以看出，当导电包覆层占导电颗粒质量含量的2％～40％时，电池具有较为均衡的安全性能和循环性能。
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 (12)

  1. 一种叠片电芯，其特征在于，包括电极片组件和保护组件，所述保护组件位于所述电极片组件外侧极片的表面；
    所述电极片组件中包括至少一个功能电极片，所述功能电极片包括第一集流体、第一保护层和活性层，所述第一保护层位于所述第一集流体和活性层之间；
    所述保护组件包括第二集流体和第二保护层，且所述第二保护层远离所述电极片组件；所述第一保护层的厚度、所述第二保护层的厚度各自大于0.5μm；
    所述第一保护层、第二保护层各自独立的包括导电颗粒和粘结剂，所述导电颗粒为表面具有导电包覆层的无机填料，所述导电包覆层占所述导电颗粒的质量含量为2％～40％。
  2. 根据权利要求1所述的叠片电芯，其特征在于，所述导电包覆层至少一部分构成导电颗粒的最外层。
  3. 根据权利要求1或2所述的叠片电芯，其特征在于，所述导电包覆层被覆至少一部分的无机填料。
  4. 根据权利要求1-3任一项所述的叠片电芯，其特征在于，所述第一保护层的厚度为A，所述第二保护层的厚度为B，A≤B。
  5. 根据权利要求1-4任一项所述的叠片电芯，其特征在于，所述第一保护层的厚度、所述第二保护层的厚度各自独立的为1μm～10μm。
  6. 根据权利要求1-5任一项所述的叠片电芯，其特征在于，所述第一保护层、所述第二保护层各自独立的按照质量含量包括40％～98％的导电颗粒、2％～30％的粘接剂以及0％～40％的非导电颗粒。
  7. 根据权利要求1-6任一项所述的叠片电芯，其特征在于，所述第一保护层、第二保护层各自独立的电阻为10～2000mΩ。
  8. 根据权利要求1-6任一项所述的叠片电芯，其特征在于，所述导电颗粒的电阻率为1～100Ω·cm。
  9. 根据权利要求1-6任一项所述的叠片电芯，其特征在于，
    所述导电颗粒的平均粒径为0.05～5μm。
  10. 根据权利要求1所述的叠片电芯，其特征在于，所述导电包覆层包括氧化锡、氧化铟、ATO、FTO、ITO、碳材料中的至少一种。
  11. 根据权利要求7-10任一项所述的叠片电芯，其特征在于，所述无机填料包括氧化铝、氧化镁、氧化钛、氧化锌、氧化硅、勃姆石、氧化钴、磷酸铁、磷酸铁锂、镍钴锰酸锂、磷酸铁锰锂中的至少一种。
  12. 一种锂离子电池，其特征在于，包括权利要求1-11任一项所述的叠片电芯。
PCT/CN2023/079998 2022-10-24 2023-03-07 叠片电芯及锂离子电池 WO2024087450A1 (zh)

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CN1485939A (zh) * 2002-09-27 2004-03-31 Tdk��ʽ���� 锂二次电池
WO2016111185A1 (ja) * 2015-01-05 2016-07-14 Ｎｅｃエナジーデバイス株式会社 電極およびそれを用いたリチウムイオン二次電池
CN114068870A (zh) * 2020-12-14 2022-02-18 珠海冠宇电池股份有限公司 一种正极片及包括该正极片的锂离子电池
CN114156429A (zh) * 2021-11-29 2022-03-08 珠海冠宇电池股份有限公司 一种极片和锂离子电池

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1485939A (zh) * 2002-09-27 2004-03-31 Tdk��ʽ���� 锂二次电池
WO2016111185A1 (ja) * 2015-01-05 2016-07-14 Ｎｅｃエナジーデバイス株式会社 電極およびそれを用いたリチウムイオン二次電池
CN114068870A (zh) * 2020-12-14 2022-02-18 珠海冠宇电池股份有限公司 一种正极片及包括该正极片的锂离子电池
CN114156429A (zh) * 2021-11-29 2022-03-08 珠海冠宇电池股份有限公司 一种极片和锂离子电池

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