Battery monomer, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, wherein the electrode assembly comprises a positive plate, a negative plate and an isolating membrane positioned between the positive plate and the negative plate; the negative plate comprises a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer comprises a negative material, the negative material comprises a negative active material, and the negative active material comprises graphite; the positive plate comprises a positive current collector and a positive active layer positioned on at least one side of the positive current collector, the positive active layer comprises a positive material, the positive material comprises a positive active material, and the positive active material comprises lithium iron phosphate and a lithium manganese iron phosphate material; the surface density of the positive electrode active layer is 200 to 370 mg / 1540.25 mm < 2 >; and when the battery monomer is in a 100% SOC state, the compaction density of the positive electrode active layer is 2.27-2.67 g / cm < 3 >. The battery monomer has the advantages of low cost, high energy density and long cycle life.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery device and an electrical device. Background Art

[0002] In recent years, as the application scope of batteries has become more and more extensive, batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As batteries have made great progress, higher requirements have been put forward for their cycle performance and energy density. Summary of the invention

[0003] The present application is made in view of the above problems, and its purpose is to provide a battery cell, a battery device and an electric device. The battery cell of the present application has improved cycle performance and energy density while taking into account low cost.

[0004] In order to achieve the above-mentioned object, the first aspect of the present application provides a battery cell, comprising an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet;

[0005] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one side of the negative electrode current collector, the negative electrode active layer comprises a negative electrode material, the negative electrode material comprises a negative electrode active material, and the negative electrode active material comprises graphite;

[0006] The positive electrode plate comprises a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector, the positive electrode active layer comprises a positive electrode material, the positive electrode material comprises a positive electrode active material, and the positive electrode active material comprises a lithium iron phosphate material and a lithium iron manganese phosphate material;

[0007] When the battery cell is in the 100% SOC state, the surface density of the positive electrode active layer is 200-370 mg / 1540.25 mm 2 The compaction density of the positive electrode active layer is 2.27-2.67 g / cm 3 .

[0008] Therefore, when the positive electrode active material of the present invention is mixed with the lithium iron phosphate material, the surface density of the positive electrode active layer of the battery cell at 100% SOC is limited to 200-370 mg / 1540.25 mm 2 , and the compaction density of the positive electrode active layer of the battery cell at 100% SOC is limited to 2.27-2.67g / cm 3 , developed battery cells that combine low cost, high energy density and long cycle life.

[0009] In any embodiment, when the battery cell is at 100% SOC, the surface density of the positive electrode active layer is 240-340 mg / 1540.25 mm 2 . As a result, the cycle performance and energy density of the battery cell are improved at the same time.

[0010] In any embodiment, when the battery cell is at 100% SOC, the compaction density of the positive electrode active layer is 2.40-2.67 g / cm 3 . As a result, the cycle performance and energy density of the battery cell are improved at the same time.

[0011] In any embodiment, when the battery cell is at 100% SOC, the compaction density of the negative electrode active layer is 1.04-1.48 g / cm 3 , optional: 1.23-1.42g / cm 3 Therefore, limiting the compaction density of the negative electrode active layer in the battery cell at 100% SOC to the above range is beneficial to improving the energy density of the battery cell while ensuring the cycle performance of the battery cell.

[0012] In any embodiment, when the battery cell is at 100% SOC, the surface density of the negative electrode active layer is 79-170 mg / 1540.25 mm 2 or 100-155mg / 1540.25mm 2 This further increases the energy density of the battery cells.

[0013] In any embodiment, based on the mass of the positive electrode material, the mass percentage of manganese is 2.1%-25%. Therefore, limiting the mass content of manganese in the positive electrode material to the above range is conducive to improving the energy density of the battery cell while ensuring the cycle performance of the battery cell.

[0014] In any embodiment, the positive electrode active material further includes one or more elements of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb.

[0015] In any embodiment, the powder compaction density of the positive electrode material at 30000N is 2.3-2.7g / cm 3 , optional: 2.43-2.6g / cm 3 .

[0016] In any embodiment, the BET specific surface area of ​​the positive electrode material is 7.5-16 m 2 / g.

[0017] In any embodiment, the volume average particle size Dv50 of the positive electrode material is 0.35-2 μm, and can be 0.35-1.2 μm.

[0018] In any embodiment, the mass ratio of the lithium iron phosphate material to the lithium iron manganese phosphate material is 1:9-9:1, and can be optionally 3:7-7:3.

[0019] In any embodiment, the positive electrode active material further comprises carbon; and / or,

[0020] Optionally, based on the mass of the positive electrode material, the mass percentage of the carbon is 1%-3%.

[0021] Thereby, the conductivity of the positive electrode active material is further improved.

[0022] In any embodiment, the positive electrode plate further includes a positive electrode conductive layer, and the positive electrode conductive layer is disposed between the positive electrode current collector and the positive electrode active layer.

[0023] In any embodiment, the thickness of the positive electrode conductive layer is 0.5-2 μm.

[0024] In any embodiment, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0025] In any embodiment, the battery cell includes one or more of the following:

[0026] The positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers;

[0027] The positive electrode conductive agent at least includes superconducting carbon and carbon nanotubes;

[0028] The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

[0029] In any embodiment, based on the mass of the positive electrode conductive layer, the mass percentage of the positive electrode conductive agent is 30%-50%; and / or,

[0030] Based on the mass of the positive electrode conductive layer, the mass percentage of the positive electrode binder is 50%-70%.

[0031] In any embodiment, the chemical formula of the lithium iron phosphate material is Li x Fe (1-s) M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3, s is greater than or equal to 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, and M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb; and / or,

[0032] The chemical formula of the lithium manganese iron phosphate material is Li x Fe (1-t-s) Mn t M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3, t is greater than 0 and less than 1, s is greater than or equal to 0 and less than 1, 1-ts is greater than 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, and M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb.

[0033] In any embodiment, the positive electrode active layer further includes a lithium supplement, and the lithium supplement includes one or more of lithium nickel cobalt manganese oxide, lithium ferrite, lithium nickel oxide, lithium cobalt oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium oxide, lithium fluoride, lithium sulfide, and lithium nitride;

[0034] Optionally, the lithium ferrite in the lithium supplement is lithium-rich lithium ferrite;

[0035] Optionally, the lithium nickelate in the lithium supplement is lithium-rich lithium nickelate.

[0036] In any embodiment, the negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is disposed between the negative electrode current collector and the negative electrode active layer.

[0037] In any embodiment, the thickness of the negative electrode conductive layer is 0.5-2 μm.

[0038] In any embodiment, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder.

[0039] In any embodiment, the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or,

[0040] The negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0041] In any embodiment, based on the mass of the negative electrode conductive layer, the mass percentage of the negative electrode conductive agent is 20%-40%; and / or,

[0042] Based on the mass of the negative electrode conductive layer, the mass percentage of the negative electrode binder is 60%-80%.

[0043] In any embodiment, the negative electrode active layer is a single-layer or multi-layer structure, and the volume average particle size Dv50 of the negative electrode active material in the negative electrode active layer is 7.5-19.5 μm.

[0044] In any embodiment, the negative electrode active layer is a single-layer structure, and the volume average particle size Dv50 of the negative electrode active material is 8.0-17.5 μm.

[0045] In any embodiment, the negative electrode active layer includes a first negative electrode active layer close to the negative electrode current collector and a second negative electrode active layer disposed on the first negative electrode active layer.

[0046] In any embodiment, the thickness ratio of the second negative electrode active layer to the first negative electrode active layer is 2:8-8:2.

[0047] In any embodiment, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer is 7.5-19.5 μm, and can be 12.5-18.5 μm.

[0048] In any embodiment, the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is 7.5-19.5 μm, and optionally 7.5-15.5 μm.

[0049] In any embodiment, the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is smaller than the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer. This is beneficial to improve the discharge power of the battery cell, while increasing the energy density of the battery cell and reducing the cost.

[0050] In any embodiment, the graphite in the first negative electrode active layer and the second negative electrode active layer is independently selected from one or more of natural graphite and composite graphite.

[0051] In any embodiment, the composite graphite includes a body and a coating layer coated on the surface of the body; the body includes artificial graphite, and the coating layer includes amorphous carbon.

[0052] In any embodiment, the composite graphite includes secondary particles.

[0053] In any embodiment, the powder resistivity of the composite graphite at 8 MPa is 0.01-0.04 Ω·cm.

[0054] In any embodiment, the powder compaction density of the composite graphite under a pressure of 20000N is 1.5-1.85g / cm 3 , optional: 1.55-1.75g / cm 3 .

[0055] In any embodiment, the negative electrode material has a charge capacity of 350-550 mAh / g at a rate of 0.1C.

[0056] In any embodiment, the negative electrode active material further comprises a silicon material.

[0057] In any embodiment, the silicon material includes one or more of silicon-oxygen compounds and silicon-carbon compounds; and / or,

[0058] Based on the mass of the negative electrode material, the mass percentage of the silicon element is 0.3%-10%, and can be optionally 1%-6%.

[0059] In any embodiment, the battery cell further comprises an electrolyte, and the conductivity of the electrolyte at room temperature is 10-20 mS / cm, and can be optionally 12-17 mS / cm.

[0060] In any embodiment, the battery cell further includes a separator, wherein the separator includes a porous base film and a functional film layer disposed on at least one side of the porous base film.

[0061] In any embodiment, the thickness of the porous base membrane is 5-7 μm; and / or,

[0062] The porosity of the porous base film is 20%-70% or 30%-50%.

[0063] In any embodiment, the functional membrane layer includes a first functional membrane layer and a second functional membrane layer respectively arranged on both sides of the porous base membrane, the first functional membrane layer includes inorganic material particles, the second functional membrane layer includes composite particles, and the composite particles include non-fluoropolymer particles and inorganic material particles attached to the surface of the non-fluoropolymer particles or located in the non-fluoropolymer particles.

[0064] In any embodiment, the thickness of the positive electrode current collector is 9-17 μm; and / or,

[0065] The thickness of the negative electrode current collector is 4.5-8 μm.

[0066] In any embodiment, the battery cell has a liquid injection coefficient of 2.4-3.1 g / Ah.

[0067] In any embodiment, the volume energy density of the battery cell is 400-550Wh / L or 430-500Wh / L.

[0068] The second aspect of the present application further provides a battery device, comprising the battery cell of the first aspect of the present application; the battery device comprises a battery module, a battery pack or an energy storage device.

[0069] The third aspect of the present application further provides an electrical device, comprising the battery cell of the first aspect of the present application or the battery device of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic diagram of a battery assembly according to one embodiment of the present application.

[0071] Figure 2 It is an exploded view of a battery cell according to one embodiment of the present application.

[0072] Figure 3 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0073] Figure 4 yes Figure 3 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0074] Figure 5 Schematic diagram of an electrical device using a battery pack according to an embodiment of the present application as a power source.

[0075] Description of reference numerals:

[0076] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0077] Below, the embodiments of the battery cells, battery modules, battery packs and electrical devices of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0078] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0079] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0080] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0081] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0082] [Battery Cell]

[0083] A battery cell, also known as a rechargeable battery or storage battery, refers to a battery that can be recharged to activate the active material after being discharged and continue to be used.

[0084] Normally, a battery cell includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the charge and discharge process of the battery, active ions (such as lithium ions) are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, and at the same time allow active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct active ions.

[0085] One embodiment of the present application provides a battery cell, comprising an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet;

[0086] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one side of the negative electrode current collector, the negative electrode active layer comprises a negative electrode material, the negative electrode material comprises a negative electrode active material, and the negative electrode active material comprises graphite;

[0087] The positive electrode plate comprises a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector, the positive electrode active layer comprises a positive electrode material, the positive electrode material comprises a positive electrode active material, and the positive electrode active material comprises a lithium iron phosphate material and a lithium iron manganese phosphate material;

[0088] When the battery cell is at 100% SOC, the surface density of the positive electrode active layer is 200-370 mg / 1540.25 mm 2 (e.g. 220mg / 1540.25mm 2 , 240mg / 1540.25mm 2 、260mg / 1540.25mm 2 、280mg / 1540.25mm 2 、300mg / 1540.25mm 2 、320mg / 1540.25mm 2 、340mg / 1540.25mm 2 or any range of the above values), the compaction density of the positive electrode active layer is 2.27-2.67 g / cm 3 (e.g. 2.27 g / cm 3 , 2.3g / cm 3 , 2.32g / cm 3, 2.35g / cm 3 , 2.36g / cm 3 , 2.38g / cm 3 , 2.4g / cm 3 , 2.41g / cm 3 , 2.43g / cm 3 , 2.45g / cm 3 , 2.48g / cm 3 , 2.51g / cm 3 , 2.53g / cm 3 , 2.6g / cm 3 , 2.67g / cm 3 or any range consisting of the above values).

[0089] The inventors of the present application have discovered that when the positive electrode active materials lithium iron manganese phosphate and lithium iron phosphate are mixed, increasing the mixing ratio of lithium iron manganese phosphate (that is, increasing the manganese content in the positive electrode active layer) is beneficial to increasing the voltage platform of the positive electrode active material and to increasing the energy density of the battery cell; however, compared to lithium iron phosphate, the upper limit of the compaction density of lithium iron manganese phosphate in the positive electrode plate is lower, which means that when the proportion of lithium iron manganese phosphate is continued to be increased in order to continue to increase the energy density, the risk of powdering and cracking of the positive electrode active layer is greatly increased, which has a greater impact on the cycle life of the battery cell.

[0090] The present application intends to develop a battery cell with low cost, high energy density and high cycle life by rationally designing a positive electrode sheet of positive electrode active materials including lithium manganese iron phosphate material and lithium iron phosphate material and by limiting the surface density and compaction density of the positive electrode active layer under 100% SOC state.

[0091] Specifically, by limiting the surface density of the positive electrode active layer to 200-370 mg / 1540.25 mm 2, it is possible to regulate the total amount of positive electrode active materials in the positive electrode active layer, reduce the adverse effect of too low surface density of the positive electrode active layer on the energy density of the battery cell, and reduce the adverse effect of too high surface density of the positive electrode active layer on the cycle performance of the battery cell due to the long lithium ion transmission distance. However, when the positive electrode active layer is in the above-mentioned surface density range, the corresponding compaction density range of the positive electrode active layer at 100% SOC state is relatively large: on the one hand, if the compaction density of the positive electrode active layer at 100% SOC state is too large, it will lead to an increase in material defects in the positive electrode active layer, affecting the cycle performance of the battery cell, and excessive compaction is not conducive to the rapid deintercalation of lithium ions in the positive electrode film layer, which is not conducive to the long-term cycle performance of the battery cell; on the other hand, if the compaction density of the positive electrode active layer at 100% SOC state is too small, the energy density of the battery cell will be too low. Therefore, in the positive electrode active layer of the positive electrode active material including lithium manganese iron phosphate and lithium iron phosphate, by limiting the above-mentioned positive electrode active layer density and further limiting the compaction density of the positive electrode active layer in the 100% SOC state, it is beneficial to improve the energy density of the battery cell while ensuring the cycle performance of the battery cell.

[0092] Furthermore, since the 100% SOC state is the highest state in which the corresponding battery cell can release energy, at this time, lithium ions in the positive electrode active layer are released, and the compaction density and surface density parameters of the positive electrode active layer are highly consistent between different battery cells. Therefore, this application limits the numerical range of the surface density and compaction density of the positive electrode active layer corresponding to the battery cell in the 100% SOC state.

[0093] In this application, 100% SOC refers to the highest state in which a battery cell can release energy. There is no unique process for charging a battery cell to 100% SOC. For example, it can be charged at 25°C at a constant current of 0.33C to a charge cutoff voltage, and then charged at the charge cutoff voltage to a state where the current is less than 0.05C.

[0094] In some embodiments, when the battery cell is at 100% SOC, the surface density of the positive electrode active layer is 240-340 mg / 1540.25 mm 2 . As a result, the cycle performance and energy density of the battery cell are improved at the same time.

[0095] In some embodiments, when the battery cell is at 100% SOC, the compaction density of the positive electrode active layer is 2.40-2.67 g / cm 3 , for example 2.45g / cm 3 , 2.48g / cm 3 , 2.5g / cm 3 , 2.52g / cm 3 , 2.54g / cm 3 , 2.56g / cm3 , 2.58g / cm 3 , 2.6g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.66g / cm 3 , 2.67g / cm 3 Or any range of the above values. Thus, the cycle performance and energy density of the battery cell are improved at the same time.

[0096] In some embodiments, when the battery cell is at 100% SOC, the compaction density of the negative electrode active layer is 1.04-1.48 g / cm 3 , optional: 1.23-1.42g / cm 3 , for example 1.1 g / cm 3 , 1.2g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 Or any range of the above values. Therefore, limiting the compaction density of the negative electrode active layer in the battery cell 100% SOC state to the above range is beneficial to improving the energy density of the battery cell while ensuring the cycle performance of the battery cell.

[0097] In some embodiments, when the battery cell is at 100% SOC, the surface density of the negative electrode active layer is 79-170 mg / 1540.25 mm 2 , optional: 90-170mg / 1540.25mm 2 , more optional 100-155mg / 1540.25mm 2 , for example 79mg / 1540.25mm 2 、80mg / 1540.25mm 2 、82mg / 1540.25mm 2 、84mg / 1540.25mm 2 、85mg / 1540.25mm 2 、87mg / 1540.25mm 2 、88mg / 1540.25mm 2 、90mg / 1540.25mm 2 、92mg / 1540.25mm 2 、95mg / 1540.25mm 2 、94mg / 1540.25mm 2 、96mg / 1540.25mm 2 、98mg / 1540.25mm 2、99mg / 1540.25mm 2 、100mg / 1540.25mm 2 、120mg / 1540.25mm 2 、140mg / 1540.25mm 2 、150mg / 1540.25mm 2 、160mg / 1540.25mm 2 、170mg / 1540.25mm 2 Or any range of the above values. This further improves the energy density of the battery cell.

[0098] In the present application, the surface density and compaction density of the positive electrode active layer (negative electrode active layer) are tested by conventional methods in the art. For example, a specific test method is:

[0099] Cut and weigh the positive electrode sheet (negative electrode sheet) of a fixed area, weigh and calculate the weight of the positive electrode collector (negative electrode collector) of the same area in advance, and measure the average thickness of the positive active layer (negative active layer) on the positive electrode sheet (negative electrode sheet).

[0100] The surface density of the positive electrode active layer (negative electrode active layer) is obtained by subtracting the weight of the positive electrode collector (negative electrode collector) from the weight of the positive electrode sheet (negative electrode sheet) and then dividing by the fixed area.

[0101] The compaction density of the positive electrode active layer (negative electrode active layer) is obtained by dividing the area density of the positive electrode active layer (negative electrode active layer) by the average thickness of the positive electrode active layer (negative electrode active layer).

[0102] When the battery cell is in the 100% SOC state, the surface density and compaction density of the positive electrode active layer (negative electrode active layer) when the battery cell is in the 100% SOC state are obtained by testing according to the above method.

[0103] In some embodiments, based on the mass of the positive electrode material, the mass percentage of manganese element is 2.1%-25%, for example, 2.5%, 2.7%, 3%, 4%, 5%, 6%, 6.5%, 7%, 7.3%, 7.5%, 8%, 8.5%, 9%, 9.3%, 9.5%, 9.6%, 9.9%, 10%, 10.5%, 11%, 11.5%, 11.9%, 12%, 12.5%, 13%, 13.5%, 13.9%, 14%, 14.5%, 15%, 15.5%, 15.8%, 16%, 16.5%, 16.8%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 22%, 23%, 24%, 25% or any range thereof. Thus, limiting the mass content of manganese in the positive electrode material to the above range is beneficial to improving the energy density of the battery cell while ensuring the cycle performance of the battery cell.

[0104] In some embodiments, the positive electrode active material further includes one or more elements of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb.

[0105] In some embodiments, the powder compaction density of the positive electrode material at 30000N is 2.3-2.7 g / cm 3 , optional: 2.43-2.6g / cm 3 , for example 2.34 g / cm 3 , 2.38g / cm 3 , 2.4g / cm 3 , 2.45g / cm 3 , 2.5g / cm 3 , 2.54g / cm 3 , 2.6g / cm 3 , 2.65g / cm 3 , 2.7g / cm 3 Or any range consisting of the above values.

[0106] In some embodiments, the BET specific surface area of ​​the cathode material is 7.5-16 m 2 / g, for example 7.5m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m2 / g, 14m 2 / g, 15m 2 / g, 16m 2 / g or any range consisting of the above values.

[0107] In some embodiments, the volume average particle size Dv50 of the positive electrode material is 0.35-2μm, which can be 0.85-2μm or 0.35-1.2μm, for example, 0.35μm, 0.4μm, 0.54μm, 0.6μm, 0.65μm, 0.68μm, 0.7μm, 0.75μm, 0.8μm, 0.82μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.5μm, 1.7μm, 1.8μm, 1.9μm, 2μm or a range consisting of any of the above values.

[0108] In the present application, the BET specific surface area of ​​the positive electrode material is tested by conventional methods in the art. For example, a specific test method is: disassemble the positive electrode sheet of the battery cell, clean the positive electrode sheet, dry and calcine the positive electrode sheet, and collect the positive electrode material in the positive electrode active layer. Referring to GB / T 19587-2017, the nitrogen adsorption specific surface area analysis test method is used for testing, and the BET specific surface area of ​​the positive electrode material is calculated by the BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be performed by the Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.

[0109] The volume average particle size Dv50 refers to the particle size that reaches 50% of the cumulative volume from the small particle size side in the volume-based particle size distribution of the powder particles. In the present application, the volume average particle size Dv50 is tested using conventional methods in the field. For example, a specific test method is: disassemble the positive electrode sheet of the battery cell, clean the positive electrode sheet, and collect the positive electrode material in the positive electrode active layer after drying and calcining the positive electrode sheet. The Dv50 particle size of the positive electrode material can be measured by Malvern 3000 laser particle size analyzer according to the standard process and requirements of GB / T 19077.1-2016 / ISO 13320:2009 particle size distribution laser diffraction method.

[0110] In the present application, the compaction density of the positive electrode material powder is tested by conventional methods in the art. For example, a specific test method is: for the positive electrode plate of the battery cell, the positive electrode plate is cleaned, and the positive electrode plate is dried and calcined, and then the positive electrode material in the positive electrode active layer is collected. The positive electrode material powder is weighed in the compaction density tester mold. The tester automatically applies the target pressure to the powder until the powder is compacted. According to the cross-sectional area of ​​the mold and the thickness of the powder at this time, the volume of the powder can be calculated. According to compaction density = mass / volume, the compaction density result of the powder can be measured.

[0111] In some embodiments, the mass ratio of the lithium iron phosphate material to the lithium iron manganese phosphate material is 1:9-9:1, and can be optionally 3:7-7:3, for example, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 or a range consisting of any of the above values.

[0112] In some embodiments, the positive electrode active material further comprises carbon;

[0113] Optionally, based on the mass of the positive electrode material, the mass percentage of the carbon is 1%-3%, for example, 1%, 1.5%, 2%, 2.5%, 3% or a range consisting of any of the above values.

[0114] Thereby, the conductivity of the positive electrode active material is further improved.

[0115] In some embodiments, the positive electrode plate further includes a positive electrode conductive layer, and the positive electrode conductive layer is disposed between the positive electrode current collector and the positive electrode active layer.

[0116] In some embodiments, the thickness of the positive electrode conductive layer is 0.5-2 μm, such as 0.5 μm, 1 μm, 1.5 μm, 2 μm or any range thereof.

[0117] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0118] In some embodiments, the battery cell includes one or more of the following:

[0119] The positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers;

[0120] The positive electrode conductive agent at least includes superconducting carbon and carbon nanotubes;

[0121] The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

[0122] In some embodiments, based on the mass of the positive electrode conductive layer, the mass percentage of the positive electrode conductive agent is 30%-50%, for example, 30%, 35%, 40%, 45%, 50% or a range consisting of any of the above values; and / or,

[0123] Based on the mass of the positive electrode conductive layer, the mass percentage of the positive electrode binder is 50%-70%, for example, 50%, 55%, 60%, 65%, 70% or a range consisting of any of the above values.

[0124] In some embodiments, the chemical formula of the lithium iron phosphate material is Li x Fe (1-s) M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3 (e.g., 0.5, 0.6, 0.8, 0.9, 1, 1.1, 1.2, 1.3, or any range thereof), s is greater than or equal to 0 and less than 1 (e.g., 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or any range thereof), and y is greater than or equal to 0.5 and less than or equal to 1.3 (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range consisting of the above values), z is greater than or equal to 3 and less than or equal to 5 (for example, 3, 4, 5 or any range consisting of the above values), and M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb.

[0125] In some embodiments, the chemical formula of the lithium manganese iron phosphate material is Li x Fe (1-t-s) Mn t M s P y O z, wherein x is greater than or equal to 0.5 and less than or equal to 1.3 (e.g., 0.5, 0.6, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range thereof), t is greater than or equal to 0 and less than 1 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any range thereof), s is greater than or equal to 0 and less than 1 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any range thereof), 1-ts is greater than or equal to 0 and less than 1 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0. 7, 0.8, 0.9 or any range consisting of the above values), y is greater than or equal to 0.5 and less than or equal to 1.3 (for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range consisting of the above values), z is greater than or equal to 3 and less than or equal to 5 (for example, 3, 4, 5 or any range consisting of the above values), and M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb.

[0126] In some embodiments, the positive electrode active layer further includes a lithium supplement, and the lithium supplement includes one or more of lithium nickel cobalt manganese oxide, lithium ferrite, lithium nickel oxide, lithium cobalt oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium oxide, lithium fluoride, lithium sulfide, and lithium nitride;

[0127] Optionally, the lithium ferrite in the lithium supplement is lithium-rich lithium ferrite;

[0128] Optionally, the lithium nickelate in the lithium supplement is lithium-rich lithium nickelate.

[0129] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is disposed between the negative electrode current collector and the negative electrode active layer.

[0130] In some embodiments, the thickness of the negative electrode conductive layer is 0.5-2 μm, such as 0.5 μm, 1 μm, 1.5 μm, 2 μm or any range thereof.

[0131] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder.

[0132] In some embodiments, the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or,

[0133] The negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0134] In some embodiments, based on the mass of the negative electrode conductive layer, the mass percentage of the negative electrode conductive agent is 20%-40%, for example, 20%, 25%, 30%, 35%, 40% or a range consisting of any of the above values; and / or,

[0135] Based on the mass of the negative electrode conductive layer, the mass percentage of the negative electrode binder is 60%-80%, for example, 60%, 65%, 70%, 75%, 80% or a range consisting of any of the above values.

[0136] In some embodiments, the negative electrode active layer is a single-layer or multi-layer structure, and the volume average particle size Dv50 of the negative electrode active material in the negative electrode active layer is 7.5-19.5 μm, for example, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm or a range consisting of any of the above numerical values.

[0137] In the present application, a multi-layer structure refers to a structure with two or more layers.

[0138] In some embodiments, the negative electrode active layer is a single-layer structure, and the volume average particle size Dv50 of the negative electrode active material is 8.0-17.5 μm, for example, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm or a range consisting of any of the above numerical values.

[0139] In some embodiments, the negative electrode active layer includes a first negative electrode active layer close to the negative electrode current collector and a second negative electrode active layer disposed on the first negative electrode active layer.

[0140] In some embodiments, the thickness ratio of the second negative electrode active layer to the first negative electrode active layer is 2:8-8:2, for example, 1:1.

[0141] In some embodiments, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer is 7.5-19.5 μm, optionally 12.5-18.5 μm, for example, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm or a range consisting of any of the above numerical values.

[0142] In some embodiments, the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is 7.5-19.5 μm, optionally 7.5-15.5 μm, for example, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm or a range consisting of any of the above numerical values.

[0143] In some embodiments, the volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is smaller than the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer. This is beneficial to improve the discharge power of the battery cell, while increasing the energy density of the battery cell and reducing the cost.

[0144] In some embodiments, the graphite in the first negative electrode active layer and the second negative electrode active layer is independently selected from one or more of natural graphite and composite graphite.

[0145] In some embodiments, the composite graphite includes a body and a coating layer coated on a surface of the body; the body includes artificial graphite, and the coating layer includes amorphous carbon.

[0146] In some embodiments, the composite graphite includes secondary particles.

[0147] In some embodiments, the powder resistivity of the composite graphite at 8 MPa is 0.01-0.04 Ω·cm.

[0148] In some embodiments, the powder compaction density of the composite graphite under a pressure of 20000N is 1.5-1.85g / cm 3 , optional: 1.55-1.75g / cm 3 .

[0149] In some embodiments, the negative electrode material has a charge capacity of 350-550 mAh / g at a 0.1C rate.

[0150] In some embodiments, the negative electrode active material further includes a silicon material.

[0151] In some embodiments, the silicon material includes one or more of silicon-oxygen compounds and silicon-carbon compounds; and / or,

[0152] Based on the mass of the negative electrode material, the mass percentage of the silicon element is 0.3%-10%, and can be optionally 1%-6%, such as 1%, 2%, 3%, 5%, 6% or a range consisting of any of the above values.

[0153] In the present application, the mass proportions of manganese and carbon in the positive electrode material and the mass proportion of silicon in the negative electrode material are tested using conventional methods in the art. For example, a specific test method is: disassemble the positive electrode sheet (negative electrode sheet) of the battery cell, clean the positive electrode sheet (negative electrode sheet), dry and calcine the positive electrode sheet (negative electrode sheet), collect the positive electrode material (negative electrode material) in the positive electrode active layer (negative electrode active layer), select multiple points in the positive electrode material or the negative electrode material for testing by SEM-EDS coupling instrument, take the average value, and obtain the mass proportion of manganese and carbon in the positive electrode material or the mass proportion of silicon in the negative electrode material.

[0154] In the present application, the charge capacity in grams of the negative electrode material at a rate of 0.1C is tested using conventional methods in the art. For example, one of the specific test methods is: disassemble the negative electrode sheet coated on both sides of the battery cell, scrape the negative electrode material from one side of the negative electrode current collector and weigh it, take multiple negative electrode sheets of the same area to perform the above operation, and take the average weight to obtain the weight m of the negative electrode material on a single side of the negative electrode sheet. Use the above-mentioned single-sided negative electrode sheet of the same area to prepare a button battery, charge it at a rate of 0.1C to the upper cut-off voltage at 25°C, then charge it at a constant voltage to 0.05C, let it stand for 30 minutes, and then discharge it at a rate of 0.1C to the lower cut-off voltage. Repeat the charge and discharge twice, and record the last charge capacity as Cn. Divide the last charge capacity Cn by the weight m of the negative electrode material on a single side to get the test result.

[0155] In some embodiments, the battery cell further includes an electrolyte, and the conductivity of the electrolyte at room temperature is 10-20 mS / cm, and can be optionally 12-17 mS / cm.

[0156] In some embodiments, the battery cell further includes a separator, wherein the separator includes a porous base film and a functional film layer disposed on at least one side of the porous base film.

[0157] In some embodiments, the porous base membrane has a thickness of 5-7 μm; and / or,

[0158] The porosity of the porous base film is 20%-70%, and can be 30%-50%.

[0159] In some embodiments, the functional membrane layer includes a first functional membrane layer and a second functional membrane layer respectively arranged on both sides of the porous base membrane, the first functional membrane layer includes inorganic material particles, the second functional membrane layer includes composite particles, and the composite particles include non-fluorinated polymer particles and inorganic material particles attached to the surface of the non-fluorinated polymer particles or located in the non-fluorinated polymer particles.

[0160] In some embodiments, the thickness of the positive electrode current collector is 9-17 μm; and / or,

[0161] The thickness of the negative electrode current collector is 4.5-8 μm.

[0162] In some embodiments, the battery cell has a liquid injection coefficient of 2.4-3.1 g / Ah.

[0163] In some embodiments, the volume energy density of the battery cell is 400-550Wh / L, optionally 430-500Wh / L.

[0164] In this application, positive electrode material refers to the material of the positive electrode active layer collected from the surface of the positive electrode current collector after the positive electrode sheet is cleaned, dried and calcined. Positive electrode material includes positive electrode active material and / or its calcined product, and also includes auxiliary agents and / or its calcined product used to prepare positive electrode sheets. The auxiliary agents include but are not limited to positive electrode binders, positive electrode conductive agents, positive electrode film-forming agents, etc.

[0165] In this application, negative electrode material refers to the material of the negative electrode active layer collected from the surface of the negative electrode current collector after the negative electrode sheet is cleaned, dried and calcined. Negative electrode material includes negative electrode active material and / or its calcined product, and also includes additives and / or its calcined product used to prepare the negative electrode sheet. The additives include but are not limited to negative electrode binders, negative electrode thickeners, negative electrode conductive agents, negative electrode film-forming agents, etc.

[0166] In the present application, the mass percentage of manganese element in the positive electrode material, the type of element in the active material of the positive electrode material, the powder compaction density of the positive electrode material, the BET specific surface area of ​​the positive electrode material, and the volume average particle size Dv50 of the positive electrode material can be tested when the battery cell is in any state between 0% SOC and 100% SOC. The above-mentioned state changes of the battery cell basically have no effect on the test results.

[0167] [Positive electrode]

[0168] The battery cell will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li in the battery cell is different when it is discharged to different states. In the list of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0169] In the list of positive electrode active materials in this application, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0170] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0171] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0172] In some embodiments, the positive electrode active material may also adopt the positive electrode active material for battery cells known in the art. As an example, the positive electrode active material may also include at least one of the following materials: lithium transition metal oxides and modified compounds thereof. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium iron oxide (such as Li 5 FeO4 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and at least one of its modified compounds.

[0173] In some embodiments, the positive electrode active layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0174] In some embodiments, the positive electrode active layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0175] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0176] [Negative electrode]

[0177] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0178] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0179] In some embodiments, the negative electrode active material may also adopt the negative electrode active material for battery cells known in the art. As an example, the negative electrode active material may also include at least one of the following materials: soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0180] In some embodiments, the negative electrode active layer may further include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0181] In some embodiments, the negative electrode active layer may further include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0182] In some embodiments, the negative electrode active layer may further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0183] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0184] [Electrolyte]

[0185] The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.

[0186] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0187] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0188] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0189] In some embodiments, the electrolyte may further include additives. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge performance of the battery cell, additives that improve the high or low temperature performance of the battery cell, etc.

[0190] [Isolation film]

[0191] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0192] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0193] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0194] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0195] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0196] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The electrode assembly 52 is an example of a battery cell having a square structure.

[0197] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0198] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more. The specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0199] In the battery module, the plurality of battery cells may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells may be fixed by fasteners.

[0200] Optionally, the battery module may further include a housing having a receiving space, and a plurality of battery cells are received in the receiving space.

[0201] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0202] Figure 3 and Figure 4 1 is a battery pack 1 as an example. Figure 3 and Figure 4 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0203] In addition, the present application also provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as power sources for electrical devices, or as energy storage units for electrical devices. Electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0204] As an electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0205] Figure 5 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0206] [Example]

[0207] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0208] Example 1

[0209] (1) Positive electrode sheet: A positive electrode conductive layer is arranged on both sides of the positive electrode current collector aluminum foil (thickness of 13 μm), and a positive electrode active layer is arranged on the positive electrode conductive layer on both sides. The positive electrode conductive layer is a film layer formed by mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyacrylate and the solvent evenly and then coating it on the surface of the positive electrode current collector and drying it. The thickness is 1 μm, and the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 50%, and the mass content of the positive electrode binder in the positive electrode conductive layer is 50%. The positive electrode active layer includes positive electrode active materials lithium manganese iron phosphate and lithium iron phosphate (mass ratio 7:3), binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black, and the mass ratio of the three is 97:2:1.

[0210] (2) Negative electrode sheet: Negative electrode conductive layers are arranged on both sides of the negative electrode current collector copper foil (thickness of 6 μm), and negative electrode active layers are arranged on the negative electrode conductive layers on both sides. The negative electrode conductive layer is formed by mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene butadiene rubber SBR, the thickener sodium carboxymethyl cellulose (CMC-Na) and the solvent water evenly, and then coating it on the surface of the negative electrode current collector to form a film layer with a thickness of 1 μm. The mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%. The negative electrode active layer includes two layers, an upper layer (away from the current collector) and a lower layer (close to the current collector). The thickness ratio of the two negative electrode active layers is 1:1. The two negative electrode active layers include the negative electrode active material, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) in a mass ratio of 96:1:2:1. The Dv50 particle size of the negative electrode active material in the upper layer is 12.3μm, and the Dv50 particle size of the negative electrode active material in the lower layer is 15.31μm. The negative electrode active materials in the upper and lower layers are a mixture of composite graphite and silicon with a mass ratio of 97:3 (the composite graphite particles include artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%), wherein the Dv50 of the composite graphite particles is 15.4μm, and the powder compaction density under a pressure of 20000N is 1.74g / cm 3 .

[0211] The compaction density of the entire negative electrode active layer at 100% SOC of the battery is 1.41 g / cm 3 .

[0212] (3) Isolation film: A polyethylene (PE) film coated with nano-aluminum oxide was used as the isolation film with a thickness of 5 μm.

[0213] (4) Electrolyte: comprising organic solvents ethyl acetate EA, ethylene carbonate EC, and ethyl methyl carbonate EMC (mass ratio 50:35:15), and the electrolyte comprising 10.5 mass% lithium hexafluorophosphate (LiPF 6) and 4.5% by mass of lithium bis(fluorosulfonyl)imide LiFSI as lithium salt, and also include 2.5% by mass of additives vinylene carbonate VC, 1% by mass of fluoroethylene carbonate FEC, 0.5% by mass of 1,3-propylene sultone PS, 0.5% by mass of vinyl sulfite DTD and 0.5% by mass of lithium difluorophosphate LiPO 2 F 2 The conductivity of the electrolyte is 13mS / cm.

[0214] (5) Battery cell: including stacked positive electrode sheets, separators, and negative electrode sheets to obtain an electrode assembly. The electrode assembly is added to the outer packaging square aluminum shell (length 600mm, thickness 19mm, height 105mm), and then injected with electrolyte after drying, with an injection coefficient of 2.9g / Ah. After packaging, high-temperature static, formation, secondary injection, aging, capacity and other processes, a battery cell is obtained.

[0215] The battery monomer preparation methods of Examples 2-19 and Comparative Examples 1-4 are similar to those of Example 1, and the different parameters are described below and in Table 1.

[0216] Example 8

[0217] The compaction density of the entire negative electrode active layer at 100% SOC of the battery cell is 1.34 g / cm 3 .

[0218] The remaining parameters are shown in Table 1, and the parameters not shown are the same as those in Example 1.

[0219] Example 13

[0220] In the negative electrode sheet, the negative electrode active materials in the upper and lower layers are a mixture of composite graphite and silicon with a mass ratio of 94:6 (the composite graphite particles include artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%), wherein the Dv50 of the composite graphite particles is 15.4μm, and the powder compaction density under a pressure of 20000N is 1.74g / cm 3 The Dv50 particle size of the negative electrode active material in the upper layer was 12.2 μm, and the Dv50 particle size of the negative electrode active material in the lower layer was 15.12 μm.

[0221] The compaction density of the entire negative electrode active layer at 100% SOC of the battery cell is 1.37 g / cm 3 .

[0222] The remaining parameters are shown in Table 1, and the parameters not shown are the same as those in Example 1.

[0223] Embodiment 18

[0224] In the negative electrode sheet, the negative electrode active materials in the upper and lower layers are both composite graphite, the Dv50 particle size of the composite graphite in the lower layer is 15.43 μm, and the Dv50 particle size of the composite graphite in the upper layer is 12.4 μm.

[0225] The compaction density of the entire negative electrode active layer at 100% SOC of the battery cell is 1.44 g / cm 3 .

[0226] The remaining parameters are shown in Table 1, and the parameters not shown are the same as those in Example 1.

[0227] Embodiment 19

[0228] The negative electrode active layer in the negative electrode sheet is a single layer, and the negative electrode active material in the negative electrode active layer is composite graphite (the composite graphite particles include artificial graphite and a carbon coating layer, the carbon coating layer is coated on the surface of the artificial graphite, and the mass content of the carbon coating layer is 3.5%), wherein the Dv50 of the composite graphite particles is 15.4μm, and the powder compaction density under a pressure of 20000N is 1.74g / cm 3 .

[0229] The compaction density of the entire negative electrode active layer at 100% SOC of the battery cell is 1.44 g / cm 3 .

[0230] The remaining parameters are shown in Table 1, and the parameters not shown are the same as those in Example 1.

[0231] Parameter Test

[0232] Test of the mass proportion of manganese and carbon in the positive electrode material and the mass proportion of silicon in the negative electrode material: disassemble the positive electrode sheet (negative electrode sheet) of the battery cell, use DMC (dimethyl carbonate) to fully clean the positive electrode sheet (negative electrode sheet), dry and calcine the positive electrode sheet (negative electrode sheet), collect the positive electrode material (negative electrode material) in the positive electrode active layer (negative electrode active layer), select multiple points (for example, 50) in the positive electrode material or the negative electrode material for testing by SEM-EDS combination instrument, take the average value, and obtain the mass proportion of manganese and carbon in the positive electrode material or the mass proportion of silicon in the negative electrode material.

[0233] Test method for surface density and compaction density of positive electrode active layer (negative electrode active layer):

[0234] Cut and weigh the positive electrode sheet (negative electrode sheet) of a fixed area, weigh and calculate the weight of the positive electrode collector (negative electrode collector) of the same area in advance, and measure the average thickness of the positive active layer (negative active layer) on the positive electrode sheet (negative electrode sheet).

[0235] The surface density of the positive electrode active layer (negative electrode active layer) is obtained by subtracting the weight of the positive electrode collector (negative electrode collector) from the weight of the positive electrode sheet (negative electrode sheet) and then dividing by the fixed area.

[0236] The compaction density of the positive electrode active layer (negative electrode active layer) is obtained by dividing the area density of the positive electrode active layer (negative electrode active layer) by the average thickness of the positive electrode active layer (negative electrode active layer).

[0237] When the battery cell is in the 100% SOC state, the compaction density of the positive electrode active layer (negative electrode active layer) in the 100% SOC state of the battery cell is obtained by testing according to the above method. The process of charging the battery cell to 100% SOC can be, for example, charging the battery cell at 25°C at a constant current of 0.33C to a voltage of 4.1V, and then charging at a constant voltage of 4.1V to a state where the current is less than 0.05C.

[0238] BET specific surface area test method for positive electrode materials: disassemble the positive electrode plates of the battery cells, use DMC (dimethyl carbonate) to fully clean the positive electrode plates, dry and calcine the positive electrode plates, and collect the positive electrode materials in the positive electrode active layer. Refer to GB / T 19587-2017, use the nitrogen adsorption specific surface area analysis test method to test, and use the BET (BrunauerEmmett Teller) method to calculate the BET specific surface area of ​​the positive electrode material, where the nitrogen adsorption specific surface area analysis test can be performed by the Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.

[0239] The volume average particle size Dv50 refers to the particle size that reaches 50% of the volume cumulatively from the small particle size side in the particle size distribution based on the volume of the powder particles. The positive electrode plates of the battery cells are disassembled, and the positive electrode plates are fully cleaned with DMC (dimethyl carbonate), and the positive electrode plates are dried and calcined, and the positive electrode materials in the positive electrode active layer are collected. The Dv50 particle size of the positive electrode material can be measured by Malvern 3000 laser particle size analyzer according to the standard process and requirements of GB / T 19077.1-2016 / ISO 13320:2009 particle size distribution laser diffraction method.

[0240] The test method of charging gram capacity of negative electrode materials at a rate of 0.1C is as follows: disassemble the negative electrode sheets coated on both sides of the battery cell, scrape off the negative electrode material from one side of the negative electrode current collector and weigh it, take 6 negative electrode sheets of the same area to perform the above operation, and take the average weight to obtain the weight m of the negative electrode material on a single side of the negative electrode sheet. Use the above single-sided negative electrode sheets of the same area to prepare button batteries, charge to the upper cutoff voltage at a rate of 0.1C at 25°C, then charge to 0.05C at a constant voltage, let stand for 30 minutes, and discharge to the lower cutoff voltage at a rate of 0.1C. Repeat the charge and discharge twice, and record the last charge capacity as Cn. Divide the last charge capacity Cn by the weight m of the negative electrode material on a single side to obtain the test result.

[0241] The powder compaction density test method of the positive electrode material: For the positive electrode plate of the battery cell, DMC (dimethyl carbonate) is used to fully clean the positive electrode plate, and the positive electrode plate is dried and calcined, and the positive electrode material in the positive electrode active layer is collected. The positive electrode material powder is weighed and placed in the compaction density tester mold. The tester automatically applies the target pressure to the powder until the powder is compacted. The volume of the powder can be calculated based on the cross-sectional area of ​​the mold and the thickness of the powder at this time. According to the compaction density = mass / volume, the powder compaction density result can be measured.

[0242] Battery Test

[0243] (1) Volume energy density test of battery cells:

[0244] Place the battery cell at 25°C, charge it to 4.1V at a constant current of 0.33C, and then charge it to 0.05C at a constant voltage; discharge it to 2.5V at a constant current of 0.33C, and record the discharge capacity A0 and discharge platform voltage V at this time; use a caliper to measure the length, thickness, and height of the battery cell (generally calculated based on the outer shell size of the battery cell, excluding the height of the electrode terminals and the insulating film outside the outer shell), and calculate the volume of the battery cell V0; the volume energy density of the battery cell VED = (A0×V) / V0, unit Wh / L.

[0245] (2) Cycle performance test of battery cells:

[0246] At 30°C, charge the battery cell at a constant current of 1C to a charge cut-off voltage of 4.1V (the charge cut-off voltage of a battery cell whose positive electrode active material is pure lithium iron phosphate is 3.8V), and then discharge it at a constant current of 1C to 2.0V. This is one charge and discharge cycle. Record the first discharge capacity C0. Repeat the above charge and discharge cycle 1000 times, record the last discharge capacity Cn, and calculate the cycle capacity retention rate (i.e., Cn / C0×100%).

[0247] In the following table, the chemical formula of the lithium iron manganese phosphate material also includes the M1 element in addition to Li, Fe, and Mn. The mass content of the M1 element in the lithium iron manganese phosphate material is trace, so it is not expressed in its chemical formula, but it is still considered that the M1 element is included in the lithium iron manganese phosphate material shown in the table. The sum of the subscripts of Fe and Mn in the chemical formula of the lithium iron manganese phosphate material and the total number of moles of the M1 element in the chemical formula is 1. The chemical formula of the lithium iron phosphate material also includes the M2 element in addition to Li and Fe. The mass content of the M2 element in the lithium iron phosphate material is trace, so it is not expressed in its chemical formula, but it is still considered that the M2 element is included in the lithium iron phosphate material shown in the table. The sum of the subscript of Fe in the chemical formula of the lithium iron phosphate material and the total number of moles of the M2 element in the chemical formula is 1. The M1 element and the M2 element may be the same or different.

[0248]

[0249]

[0250] Table 2

[0251]

[0252] It can be seen from the above table that compared with the comparative example 1 in which the compaction density of the positive electrode active layer is too high at 100% SOC of the battery, the cycle performance of the battery cells of Examples 1-19 of the present application is significantly improved.

[0253] Table 3

[0254]

[0255]

[0256] It can be seen from the above table that compared with the comparative example 2 in which the compaction density of the positive electrode active layer is too low at 100% SOC of the battery, the energy density of the battery cells of Examples 1-19 of the present application is significantly higher.

[0257] Table 4

[0258]

[0259] It can be seen from the above table that compared with the comparative example 3 in which the positive electrode active layer density is too high, the cycle performance of the battery cells of the examples 1-19 of the present application is significantly improved.

[0260] Table 5

[0261]

[0262] It can be seen from the above table that compared with the comparative example 4 in which the positive electrode active layer density is too low, the energy density of the battery cells of the examples 1-19 of the present application is significantly higher.

[0263] Table 6

[0264]

[0265] It can be seen from the above table that the compaction density of the positive electrode active layer is reduced when the battery is in the 100% SOC state, which is beneficial to improving the cycle performance of the battery cell.

[0266] Table 7

[0267]

[0268]

[0269] It can be seen from the above table that the compaction density of the positive electrode active layer increases when the battery is in the 100% SOC state, which is beneficial to improving the energy density of the battery cell.

[0270] Table 8

[0271]

[0272] It can be seen from the above table that the increase in the density of the positive electrode active surface is beneficial to improving the energy density of the battery cell.

[0273] Table 9

[0274]

[0275] It can be seen from the above table that the density of the positive electrode active surface is reduced, which is beneficial to improving the cycle performance of the battery cell.

[0276] Table 10

[0277]

[0278] It can be seen from the above table that the compaction density of the negative electrode active layer is reduced when the battery is in the 100% SOC state, which is beneficial to improving the cycle performance of the battery cell.

[0279] Table 11

[0280]

[0281] It can be seen from the above table that increasing the mass content of manganese in the positive electrode material is beneficial to improving the energy density of the battery cell.

[0282] Table 12

[0283]

[0284] It can be seen from the above table that reducing the mass content of manganese in the positive electrode material is beneficial to improving the cycle performance of the battery cell.

[0285] Table 13

[0286]

[0287] As can be seen from the table above, the increase in the mass percentage of silicon in the negative electrode active material is beneficial to improving the energy density of the battery cell. Gr is composite graphite.

[0288] Table 14

[0289]

[0290] It can be seen from the above table that the mass proportion of lithium manganese iron phosphate material in the positive electrode active material increases, which is beneficial to improving the energy density of the battery cell.

[0291] Table 15

[0292]

[0293] It can be seen from the above table that the mass proportion of lithium manganese iron phosphate material in the positive electrode active material is reduced, which is beneficial to improving the cycle performance of the battery cell.

[0294] Table 16

[0295]

[0296] As can be seen from the table above, the reduction in the mass percentage of silicon in the negative electrode active material is beneficial to improving the cycle performance of the battery cell. Gr is composite graphite.

[0297] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet; The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on at least one side of the negative electrode current collector, the negative electrode active layer comprises a negative electrode material, the negative electrode material comprises a negative electrode active material, and the negative electrode active material comprises graphite; The positive electrode plate comprises a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector, the positive electrode active layer comprises a positive electrode material, the positive electrode material comprises a positive electrode active material, and the positive electrode active material comprises a lithium iron phosphate material and a lithium iron manganese phosphate material; When the battery cell is in the 100% SOC state, the surface density of the positive electrode active layer is 200-370 mg / 1540.25 mm 2 The compaction density of the positive electrode active layer is 2.27-2.67 g / cm 3 .

2. The battery cell according to claim 1, wherein: When the battery cell is in the 100% SOC state, the surface density of the positive electrode active layer is 240-340 mg / 1540.25 mm 2 .

3. The battery cell according to claim 1 or 2, wherein: The battery cell is in the 100% SOC state, and the compaction density of the positive electrode active layer is 2.40-2.67 g / cm 3 .

4. The battery cell according to any one of claims 1 to 3, wherein: The battery cell is in the 100% SOC state, and the compaction density of the negative electrode active layer is 1.04-1.48 g / cm 3 , optional: 1.23-1.42g / cm 3 .

5. The battery cell according to any one of claims 1 to 4, wherein: When the battery cell is in the 100% SOC state, the surface density of the negative electrode active layer is 79-170 mg / 1540.25 mm 2 , optional: 100-155mg / 1540.25mm 2 .

6. The battery cell according to any one of claims 1 to 5, wherein: Based on the mass of the positive electrode material, the mass percentage of manganese element is 2.1%-25%.

7. The battery cell according to any one of claims 1 to 6, wherein: The positive electrode active material also includes one or more elements selected from the group consisting of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb.

8. The battery cell according to any one of claims 1 to 7, wherein: The powder compaction density of the positive electrode material at 30000N is 2.3-2.7g / cm 3 , optional: 2.43-2.6g / cm 3 .

9. The battery cell according to any one of claims 1 to 8, wherein: The BET specific surface area of ​​the positive electrode material is 7.5-16 m 2 / g.

10. The battery cell according to any one of claims 1 to 9, wherein: The volume average particle size Dv50 of the positive electrode material is 0.35-2 μm, and can be optionally 0.35-1.2 μm.

11. The battery cell according to any one of claims 1 to 10, wherein: The mass ratio of the lithium iron phosphate material to the lithium iron manganese phosphate material is 1:9-9:1, and can be optionally 3:7-7:

3.

12. The battery cell according to any one of claims 1 to 11, wherein: The positive electrode active material also includes carbon; Optionally, based on the mass of the positive electrode material, the mass percentage of the carbon is 1%-3%.

13. The battery cell according to any one of claims 1 to 12, wherein: The positive electrode plate further includes a positive electrode conductive layer, and the positive electrode conductive layer is arranged between the positive electrode current collector and the positive electrode active layer.

14. The battery cell according to claim 13, wherein: The thickness of the positive electrode conductive layer is 0.5-2 μm.

15. The battery cell according to claim 13 or 14, wherein: The positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

16. The battery cell according to claim 15, characterized in that One or more of the following: The positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; The positive electrode conductive agent at least includes superconducting carbon and carbon nanotubes; The positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid and fluorine-containing acrylic resin.

17. The battery cell according to claim 15 or 16, wherein: Based on the mass of the positive electrode conductive layer, the mass percentage of the positive electrode conductive agent is 30%-50%; and / or, Based on the mass of the positive electrode conductive layer, the mass percentage of the positive electrode binder is 50%-70%.

18. The battery cell according to any one of claims 1 to 17, wherein: The chemical formula of the lithium iron phosphate material is Li x Fe (1-s) M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3, s is greater than or equal to 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, and M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb; and / or, The chemical formula of the lithium manganese iron phosphate material is Li x Fe (1-t-s) Mn t M s P y O z , wherein x is greater than or equal to 0.5 and less than or equal to 1.3, t is greater than 0 and less than 1, s is greater than or equal to 0 and less than 1, 1-ts is greater than 0 and less than 1, y is greater than or equal to 0.5 and less than or equal to 1.3, z is greater than or equal to 3 and less than or equal to 5, and M includes one or more elements selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Hf, Ni, Co, Ru, Ag, and Pb.

19. The battery cell according to any one of claims 1 to 18, wherein: The positive electrode active layer also includes a lithium supplement, which includes one or more of lithium nickel cobalt manganese oxide, lithium ferrite, lithium nickel oxide, lithium cobalt oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium oxide, lithium fluoride, lithium sulfide, and lithium nitride; optionally, the lithium ferrite in the lithium supplement is lithium-rich lithium ferrite; optionally, the lithium nickel oxide in the lithium supplement is lithium-rich lithium nickel oxide.

20. The battery cell according to any one of claims 1 to 19, wherein: The negative electrode plate further includes a negative electrode conductive layer, and the negative electrode conductive layer is disposed between the negative electrode current collector and the negative electrode active layer.

21. The battery cell according to claim 20, wherein: The thickness of the negative electrode conductive layer is 0.5-2 μm.

22. The battery cell according to claim 20 or 21, wherein: The negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder.

23. The battery cell according to claim 22, wherein: The negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; and / or, The negative electrode binder includes one or more of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

24. The battery cell according to claim 22 or 23, wherein: Based on the mass of the negative electrode conductive layer, the mass percentage of the negative electrode conductive agent is 20%-40%; and / or, Based on the mass of the negative electrode conductive layer, the mass percentage of the negative electrode binder is 60%-80%.

25. The battery cell according to any one of claims 1 to 24, wherein: The negative electrode active layer is a single-layer or multi-layer structure, and the volume average particle size Dv50 of the negative electrode active material in the negative electrode active layer is 7.5-19.5 μm.

26. The battery cell according to any one of claims 1 to 25, wherein: The negative electrode active layer is a single-layer structure, and the volume average particle size Dv50 of the negative electrode active material is 8.0-17.5 μm.

27. The battery cell according to any one of claims 1 to 27, wherein: The negative electrode active layer includes a first negative electrode active layer close to the negative electrode current collector and a second negative electrode active layer disposed on the first negative electrode active layer.

28. The battery cell according to claim 27, wherein: The thickness ratio of the second negative electrode active layer to the first negative electrode active layer is 2:8-8:

2.

29. The battery cell according to claim 27 or 28, wherein: The volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer is 7.5-19.5 μm, and can be 12.5-18.5 μm.

30. The battery cell according to any one of claims 27 to 29, wherein: The volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is 7.5-19.5 μm, and can be 7.5-15.5 μm.

31. The battery cell according to any one of claims 27 to 30, wherein: The volume average particle size Dv50 of the negative electrode active material in the second negative electrode active layer is smaller than the volume average particle size Dv50 of the negative electrode active material in the first negative electrode active layer.

32. The battery cell according to any one of claims 27 to 31, wherein: The graphite in the first negative electrode active layer and the second negative electrode active layer is independently selected from one or more of natural graphite and composite graphite.

33. The battery cell according to claim 32, wherein: The composite graphite comprises a main body and a coating layer coated on the surface of the main body; the main body comprises artificial graphite, and the coating layer comprises amorphous carbon.

34. The battery cell according to claim 32 or 33, wherein: The composite graphite includes secondary particles.

35. The battery cell according to any one of claims 32 to 34, wherein: The powder resistivity of the composite graphite at 8 MPa is 0.01-0.04 Ω·cm.

36. The battery cell according to any one of claims 32 to 35, wherein: The powder compaction density of the composite graphite under a pressure of 20000N is 1.5-1.85g / cm 3 , optional: 1.55-1.75g / cm 3 .

37. The battery cell according to any one of claims 1 to 36, wherein: The charge capacity of the negative electrode material at a rate of 0.1C is 350-550 mAh / g.

38. The battery cell according to any one of claims 1 to 37, wherein: The negative electrode active material further includes a silicon material.

39. The battery cell according to claim 38, wherein: The silicon material includes one or more of silicon-oxygen compounds and silicon-carbon compounds; and / or, Based on the mass of the negative electrode material, the mass percentage of the silicon element is 0.3%-10%, and can be optionally 1%-6%.

40. The battery cell according to any one of claims 1 to 39, wherein: The battery cell also includes an electrolyte, and the conductivity of the electrolyte at room temperature is 10-20 mS / cm, and can be optionally 12-17 mS / cm.

41. The battery cell according to any one of claims 1 to 40, wherein: The battery cell further includes a separator, wherein the separator includes a porous base film and a functional film layer disposed on at least one side of the porous base film.

42. The battery cell according to claim 41, wherein: The thickness of the porous base film is 5-7 μm; and / or, The porosity of the porous base film is 20%-70%, and can be 30%-50%.

43. The battery cell according to claim 41 or 42, wherein: The functional membrane layer includes a first functional membrane layer and a second functional membrane layer respectively arranged on both sides of the porous base membrane, the first functional membrane layer includes inorganic material particles, the second functional membrane layer includes composite particles, and the composite particles include non-fluorinated polymer particles and inorganic material particles attached to the surface of the non-fluorinated polymer particles or located in the non-fluorinated polymer particles.

44. The battery cell according to any one of claims 1 to 43, wherein: The thickness of the positive electrode current collector is 9-17 μm; and / or, The thickness of the negative electrode current collector is 4.5-8 μm.

45. The battery cell according to any one of claims 1 to 44, wherein: The injection coefficient of the battery cell is 2.4-3.1g / Ah.

46. ​​The battery cell according to any one of claims 1 to 45, wherein: The volume energy density of the battery cell is 400-550Wh / L, and can be optionally 430-500Wh / L.

47. A battery device comprising the battery cell according to any one of claims 1 to 46; the battery device comprises a battery module, a battery pack or an energy storage device.

48. An electrical device comprising the battery cell according to any one of claims 1 to 46 or the battery device according to claim 47.

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