Battery monomer, battery device and electric equipment

Abstract

The invention discloses a battery monomer, a battery device and electric equipment, the battery monomer comprises a positive pole piece, the positive pole piece comprises a positive pole current collector and a positive pole film layer located on at least one side of the positive pole current collector, the positive pole film layer comprises a lithium iron phosphate material and a lithium supplement agent, and under the condition that the battery is discharged to 2.5 V at the rate of 0.04 C, the lithium iron phosphate material is added to the lithium supplement agent, and the lithium iron phosphate material is added to the lithium supplement agent. Based on the total mass of the positive electrode film layer, the content of lithium is 4.0%-4.3%; a negative pole piece; and the isolating membrane is positioned between the positive pole piece and the negative pole piece. Therefore, the battery monomer with good cycle performance and energy density is obtained.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular, to battery cells, battery devices and electrical equipment. Background Art

[0002] Batteries are used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, and are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as military equipment and aerospace. The two core demands of energy storage batteries are high safety and long life. The battery cells in related technologies have a fast initial capacity decay and cannot meet customers' increasingly high requirements for life. Summary of the invention

[0003] The first aspect of the present application provides a battery cell, the battery cell includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer includes a lithium iron phosphate material and a lithium supplement, and the lithium content is 4.0%-4.3% based on the total mass of the positive electrode film layer when the battery cell is discharged to 2.5V at a rate of 0.04C; a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite; and a separator, the separator is located between the positive electrode plate and the negative electrode plate. Thus, a battery cell with both good cycle performance and energy density is obtained.

[0004] According to some embodiments of the present application, when the battery cell is discharged to 2.5V at a rate of 0.04C, the lithium content is 4.0%-4.2% based on the total mass of the positive electrode film layer, thereby improving the cycle performance of the battery cell and the energy density of the battery cell.

[0005] According to some embodiments of the present application, when the battery cell is discharged to 2.5V at a rate of 0.04C, the lithium content is 4.0%-4.1% based on the total mass of the positive electrode film layer, thereby improving the cycle performance of the battery cell and the energy density of the battery cell.

[0006] According to some embodiments of the present application, a first gap is provided between the lithium iron phosphate material and the lithium supplement agent on a longitudinal section along the thickness direction of the positive electrode sheet, and the first gap is 50nm-500nm, thereby improving the wetting effect of the electrolyte on the positive electrode sheet and improving the dynamic performance of the battery cell.

[0007] According to some embodiments of the present application, the positive electrode film layer includes at least the following lithium supplement and lithium iron phosphate material: on the longitudinal section along the thickness direction of the positive electrode sheet, the average value of the longest diameter of the lithium supplement is a, and the average value of the longest diameter of the lithium iron phosphate material is b, and they satisfy: 5μm≤ab≤11μm. Thus, the particle size of the lithium supplement is increased, and the particle size of the lithium iron phosphate material is reduced, thereby reducing the side reactions of the lithium supplement and improving the conductivity of the positive electrode active material.

[0008] According to some embodiments of the present application, 1 μm≤b≤2 μm, and 7 μm≤a≤12 μm. Thus, by making a and b within the above ranges, the conductivity of the positive electrode active material is improved.

[0009] According to some embodiments of the present application, the lithium supplement comprises a matrix, wherein the matrix comprises Li x N y O z , wherein 1≤x≤6, 1≤y≤6, 2≤z≤12, and N includes one or more of Na element, Ni element, Co element, Mn element, Al element, and Fe element.

[0010] According to some embodiments of the present application, the lithium supplement includes a matrix, and the matrix includes one or two of Li2NiO2 and Li5FeO4.

[0011] According to some embodiments of the present application, the lithium supplement comprises a matrix, wherein the matrix comprises Li n NiO m and Li e FeO f One or two of the following, wherein 0<m≤2, 0≤n≤2, 0≤e≤5, 0<f≤4.

[0012] According to some embodiments of the present application, the lithium supplement comprises a matrix, wherein the matrix comprises NiO m and Li p FeO q One or two of the following, where 0<m≤2, 0≤p≤1, 0<q≤2.

[0013] Therefore, the decomposition of the lithium supplement can make up for the active lithium ions consumed in forming SEI, thereby increasing the energy density of the battery cell.

[0014] According to some embodiments of the present application, the molar content of the Li element in the lithium supplement is greater than the molar content of the Li element in the lithium iron phosphate material, thereby improving the lithium supplement effect and the energy density of the battery cell.

[0015] According to some embodiments of the present application, at least part of the surface of the substrate has a coating layer, and the coating layer includes one or more of C element, Al element, Zr element, P element, S element, Si element, and B element. Thus, the stability of the lithium supplement is improved, the ionic conductivity of the lithium supplement is improved, and the dynamic performance of the battery cell is improved.

[0016] According to some embodiments of the present application, the coating layer has a thickness of 10 nm to 200 nm, thereby improving the stability of the lithium supplement agent, improving the ionic conductivity of the lithium supplement agent, and improving the dynamic performance of the battery cell.

[0017] According to some embodiments of the present application, there is a second gap between the substrate and the coating layer, and the second gap is 5nm-50nm. Thus, the second gap can be filled with more electrolyte, thereby enhancing the liquid retention capacity of the positive electrode plate and reducing the internal resistance of the battery cell.

[0018] According to some embodiments of the present application, the matrix includes doping elements, and the doping elements include one or more of Al, Mn, Ti, Ni, Si, B, S, and P. Thus, the structural stability of the lithium supplement is improved, and the side reaction between the lithium supplement and the electrolyte is reduced.

[0019] According to some embodiments of the present application, based on the total mass of the matrix, the mass proportion of the doping element is 0.01%-0.2%, thereby improving the structural stability of the lithium supplement and reducing the side reaction between the lithium supplement and the electrolyte.

[0020] According to some embodiments of the present application, N includes Fe elements, and the molar ratio of Fe atoms to O atoms in the lithium supplement is 1:(2-2.5). Specifically, the lithium supplement decomposes to release oxygen, and the molar ratio of Fe atoms to O atoms varies with the degree of decomposition. The released oxygen pushes open the explosion-proof valve, thereby improving the safety of the battery cell.

[0021] According to some embodiments of the present application, the positive electrode film layer further includes a conductive agent, and the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, thereby improving the conductivity of the positive electrode sheet.

[0022] According to some embodiments of the present application, when the battery is charged to 4.5V at a rate of 0.05C, gas is generated in the battery cell, and the gas includes oxygen, and the mass proportion of the oxygen is 30%-80% based on the total mass of the gas. Thus, when overcharged, the explosion-proof valve can be pushed open by the released oxygen, thereby improving the safety of the battery cell.

[0023] According to some embodiments of the present application, the battery further comprises: an electrolyte, the electrolyte comprising a solvent, an electrolyte salt and an additive, the molar concentration of the electrolyte salt in the electrolyte is 1.1 mol / L-1.5 mol / L, the additive comprises one or more of a phosphorus-containing additive, a fluorine-containing additive and a sulfur-containing additive, and the solvent comprises a cyclic carbonate and a linear carbonate. Thus, the Li consumption in the process of forming the SEI film is reduced, the energy density of the battery cell is increased, and at the same time, the stability of the positive electrode active material and the SEI film is increased, and the cycle performance of the battery cell is improved.

[0024] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application.

[0025] A third aspect of the present application provides an electrical device, comprising the battery cell provided by the first aspect of the present application, wherein the battery cell is used to provide electrical energy.

[0026] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0028] Figure 1 A longitudinal cross-sectional SEM image of a positive electrode sheet according to an embodiment of the present application.

[0029] Figure 2 It is a schematic diagram of a battery cell according to an embodiment of the present application.

[0030] Figure 3 yes Figure 2 An exploded view of a battery cell according to an embodiment of the present application is shown.

[0031] Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0032] Figure 5 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0033] Figure 6 yes Figure 5 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0034] Figure 7FIG. 1 is a schematic diagram of an electrical device using a battery device according to an embodiment of the present application as a power source.

[0035] Description of reference numerals:

[0036] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 cover plate; 6 lithium iron phosphate particles; 71 lithium supplement agent matrix; 72 lithium supplement agent coating layer; 73 second gap. DETAILED DESCRIPTION

[0037] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0038] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0039] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0040] 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.

[0041] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the 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, the method may further 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.

[0042] At present, judging from the development of the market situation, batteries are being used more and more widely. They can be used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations. However, the energy storage batteries in related technologies cannot meet the requirements of high energy density and long cycle life at the same time.

[0043] The present application aims to develop a battery cell with excellent energy density and cycle performance, and to improve the energy density of the battery cell by setting a lithium supplement in the positive electrode film layer. By controlling the lithium content in the positive electrode film layer when the battery cell is discharged to 2.5V at a rate of 0.04C, the utilization rate of the positive electrode active material is increased, and the cycle life of the battery cell is increased.

[0044] The battery cell proposed in this application can be used in electrical equipment that uses the battery cell as a power source or various energy storage systems that use the battery cell as an energy storage element. Electrical equipment may include, but is not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0045] In a first aspect, the present application proposes a battery cell, the battery cell comprising a positive electrode plate, the positive electrode plate comprising a positive electrode collector and a positive electrode film layer located on at least one side of the positive electrode collector, the positive electrode film layer comprising a lithium iron phosphate material and a lithium supplement, and under the condition that the battery cell is discharged to 2.5V at a rate of 0.04C, based on the total mass of the positive electrode film layer, the lithium content is 4.0%-4.3%; a negative electrode plate, the negative electrode plate comprising a negative electrode collector and a negative electrode film layer located on at least one side of the negative electrode collector, the negative electrode film layer comprising a negative electrode active material, and the negative electrode active material comprising graphite; and a separator, the separator is located between the positive electrode plate and the negative electrode plate.

[0046] The present application aims to develop a battery cell with good cycle performance and energy density. By setting a lithium supplement in the positive electrode film layer, the lithium consumption caused by the formation of the SEI film in the formation stage is compensated, and the energy density of the battery cell is improved. By controlling the lithium content in the positive electrode film layer of the battery cell to be within a suitable range under the condition of 0.04C discharge rate to 2.5V, the number of lithium ions in the positive electrode film layer is increased, the gram capacity of the positive electrode active material is increased, and the energy density and cycle life of the battery cell are improved. Specifically, when the lower limit of the lithium content in the positive electrode film layer of the battery cell is lower than 4.0% under the condition of 0.04C discharge rate to 2.5V, the battery cell cannot have a high energy density and cycle life at the same time; the upper limit of the lithium content in the positive electrode film layer of the battery cell is 4.3% under the condition of 0.04C discharge rate to 2.5V. At this time, the content of the lithium supplement is continued to increase. Although the cycle performance is good, the mass proportion of the LFP material is reduced, which will reduce the energy density of the battery cell.

[0047] In the present application, under the condition that the battery cell is discharged to 2.5V at a rate of 0.04C, the testing method of lithium content is as follows: after the battery cell is discharged to 2.5V at a rate of 0.04C, the battery cell is disassembled, the positive electrode sheet is taken out and cleaned with dimethyl carbonate (DMC) solvent, and the positive electrode powder is scraped out after drying, and the lithium content in the positive electrode sheet can be tested using a Thermo ICAP7400 inductively coupled plasma-optical emission spectrometer (ICP-OES).

[0048] As an example, when the battery cell is discharged to 2.5V at a rate of 0.04C, the lithium content is 4.0%, 4.05%, 4.1%, 4.12%, 4.15%, 4.18%, 4.2%, 4.22%, 4.3%, etc. based on the total mass of the positive electrode film layer, or it can be a range composed of any of the above values.

[0049] According to some specific embodiments of the present application, when the battery cell is discharged to 2.5V at a rate of 0.04C, the lithium content is 4.0%-4.2% based on the total mass of the positive electrode film layer, thereby improving the cycle performance of the battery cell and the energy density of the battery cell.

[0050] According to some specific embodiments of the present application, when the battery cell is discharged to 2.5V at a rate of 0.04C, the lithium content is 4.0%-4.1% based on the total mass of the positive electrode film layer, thereby improving the cycle performance of the battery cell and the energy density of the battery cell.

[0051]

Positive electrode

[0052] 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.

[0053] 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.).

[0054] According to some embodiments of the present application, on the longitudinal section along the thickness direction of the positive electrode plate, there is a first gap between the lithium iron phosphate material and the lithium supplement agent, and the first gap can be 50nm-500nm. Specifically, after the lithium iron phosphate material and the lithium supplement agent are mixed, the first gap is formed at the junction of the lithium iron phosphate material and the lithium supplement agent, and the existence of the first gap can improve the wetting effect of the electrolyte on the positive electrode plate and improve the dynamic performance of the battery cell.

[0055] In the present application, the testing method for the first gap is to use plasma to cut the positive electrode plate along its thickness direction to obtain a cross-section of the positive electrode plate, and obtain a cross-sectional image through a scanning electron microscope (SEM observation). After selecting the lithium supplement agent particles, it can be observed that there is a gap at the junction between it and the surrounding active particles. Then, the maximum distance between the edge of the lithium supplement agent and the edge of the lithium iron phosphate material is measured, which is the size of the first gap.

[0056] As an example, the first gap may be 50 nm, 100 nm, 200 nm, 300 nm, 400 nm or 500 nm, etc., or may be a range consisting of any of the above values.

[0057] According to some embodiments of the present application, on the longitudinal section along the thickness direction of the positive electrode sheet, the average value of the longest diameter of the lithium supplement is a, and the average value of the longest diameter of the lithium iron phosphate material is b, and they satisfy: 5μm≤ab≤11μm. Thus, by making the difference between a and b within the above range, a first gap is formed at the junction of the positive electrode active material and the lithium supplement, thereby improving the wetting effect of the electrolyte on the positive electrode sheet.

[0058] As an example, ab may be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, etc., or may be a range consisting of any of the above values.

[0059] The longest diameter of the lithium supplement and lithium iron phosphate material of this application is defined as follows:

[0060] The positive electrode sheet including the lithium supplement agent particles and the lithium iron phosphate material is cut along the thickness direction of the sheet to expose the longitudinal section of the positive electrode film layer, and the longest diameters of the lithium supplement agent and the lithium iron phosphate material are determined by performing a scanning electron microscope (SEM) test on the longitudinal section of the positive electrode film layer. Specifically, the longest diameter of the lithium supplement agent refers to the longest straight line passing through the center point of the lithium supplement agent and extending to the periphery of the particle, and the longest diameter of the lithium iron phosphate material refers to the longest straight line passing through the center point of the lithium iron phosphate material and extending to the periphery of the particle.

[0061] In this application, the calculation method of the average value of the longest diameter of the lithium supplement and the lithium iron phosphate material is as follows:

[0062] Randomly select 30 lithium supplement agent particles in the longitudinal section of the positive electrode film layer, measure the longest diameters of the 30 lithium supplement agent particles respectively and take the average value; randomly select 30 lithium iron phosphate material particles in the longitudinal section of the positive electrode film layer, measure the longest diameters of the 30 lithium iron phosphate material particles respectively and take the average value.

[0063] According to some embodiments of the present application, the average value of the longest diameter of the lithium iron phosphate material can be 1 μm-2 μm, for example, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, or a range of any of the above values. Thus, the particle size of the positive electrode active material is reduced, the rate at which lithium ions are released from the positive electrode active material is increased, and the conductivity of the positive electrode active material is improved.

[0064] According to some embodiments of the present application, the average value of the longest diameter of the lithium supplement agent can be 7μm-12μm, for example, it can be 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm or 12μm, etc., or it can be a range composed of any of the above values. Thus, the particle size of the lithium supplement agent is increased, the specific surface area of ​​the lithium supplement agent is reduced, the number of active sites on the surface of the lithium supplement agent is reduced, the side reaction between the lithium supplement agent and the electrolyte is reduced, the stability of the electrolyte under high voltage conditions is improved, and the life of the battery cell is improved.

[0065] According to some embodiments of the present application, the lithium iron phosphate material includes an olivine structured lithium iron phosphate material. Thus, the structure of the positive electrode active material is relatively stable, the probability of collapse of the positive electrode active material during the battery cell cycle can be reduced, and the stability and safety of the battery cell can be improved.

[0066] According to some embodiments of the present application, the lithium supplement comprises a matrix, wherein the matrix comprises Li x N y O z , wherein 1≤x≤6, 1≤y≤6, 2≤z≤12, and N includes one or more of Na, Ni, Co, Mn, Al, and Fe. Thus, the decomposition of the lithium supplement can make up for the active lithium ions consumed in forming the SEI film, thereby improving the initial efficiency and energy density of the battery cell.

[0067] As an example, x may be 1, 2, 3, 4, 5 or 6, etc., or may be a range consisting of any of the above values.

[0068] As an example, y may be 1, 2, 3, 4, 5 or 6, etc., or may be a range consisting of any of the above values.

[0069] As an example, z can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, etc., or can be a range consisting of any of the above values.

[0070] According to some embodiments of the present application, the lithium supplement agent includes one or both of Li2NiO2 and Li5FeO4, thereby improving the lithium supplement effect.

[0071] According to some embodiments of the present application, when the lithium in the lithium supplement is completely or partially removed, the lithium supplement includes Li n NiO m and Li e FeO f One or two of the following, wherein 0<m≤2, 0≤n≤2, 0≤e≤5, 0<f≤4.

[0072] As an example, m may be 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0073] As an example, n may be 0, 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0074] As an example, e can be 0, 1, 2, 3, 4 or 5, etc., or can be a range consisting of any of the above values.

[0075] As an example, f may be 1, 2, 3 or 4, etc., or may be a range consisting of any of the above values.

[0076] According to some embodiments of the present application, when all lithium in the lithium supplement is removed, the lithium supplement includes NiO m and Li p FeO q One or two of the following, where 0<m≤2, 0≤p≤1, 0<q≤2.

[0077] As an example, m may be 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0078] As an example, p may be 0, 0.2, 0.4, 0.6, 0.8 or 1, etc., or may be a range consisting of any of the above values.

[0079] As an example, q may be 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0080] According to some embodiments of the present application, when the lithium replenisher in the positive electrode film layer is not completely decomposed, the molar content of the Li element in the lithium replenisher is greater than the molar content of the Li element in the lithium iron phosphate material.

[0081] According to some embodiments of the present application, at least part of the surface of the substrate has a coating layer, and the coating layer includes one or more of C element, Al element, Zr element, P element, S element, Si element, and B element. Thus, the coating layer can reduce the probability of direct contact between the substrate and the air, reduce the probability of the substrate reacting with water and carbon dioxide in the air, improve the air stability of the substrate, reduce the generation of impurity lithium on the surface of the substrate, and at the same time, improve the conductivity of the substrate and improve the utilization rate of active lithium ions.

[0082] According to some embodiments of the present application, the thickness of the coating layer may be 10 nm-200 nm. For example, it may be 10 nm, 50 nm, 100 nm, 150 nm or 200 nm, or may be a range of any of the above values. Thus, the probability of active lithium ions being released due to excessive thickness of the coating layer is reduced, the decomposition efficiency of the matrix is ​​increased, and the lithium supplementation effect is improved.

[0083] In the present application, the testing method for the thickness of the coating layer is to cut the positive electrode sheet including the lithium replenisher particles and the lithium iron phosphate material along the thickness direction of the electrode sheet to expose the longitudinal section of the positive electrode film layer. By performing SEM testing on the longitudinal section of the positive electrode film layer, after selecting the lithium replenisher particles, it can be observed that the lithium replenisher particles are a core-shell structure, and the thickness of the shell layer is measured as the thickness of the coating layer.

[0084] According to some embodiments of the present application, the lattice of the lithium supplement agent shrinks after lithium is removed, and a second gap is provided between the substrate and the coating layer, and the second gap may be 5nm-50nm. For example, the second gap may be 5nm, 10nm, 20nm, 30nm, 40nm or 50nm, or may be a range of any of the above values. Thus, the liquid retention capacity of the positive electrode sheet is improved, the transmission efficiency of active lithium ions is improved, and the internal resistance of the battery is reduced.

[0085] In the present application, the test method of the second gap is to cut the positive electrode sheet including the lithium supplement agent particles and the lithium iron phosphate material along the thickness direction of the sheet to expose the longitudinal section of the positive electrode film layer, and perform SEM test on the longitudinal section of the positive electrode film layer. After the lithium supplement agent is decomposed, it can be observed that there is a gap between the matrix and the coating layer of the lithium supplement agent particles in the longitudinal section. The maximum distance between the edge of the lithium supplement agent matrix and the inner edge of the coating layer is measured, which is the size of the second gap. The existence of the second gap helps to make the electrolyte and the lithium supplement agent matrix fully contact during the cycle, and helps the lithium supplement agent to fully release lithium ions.

[0086] refer to Figure 1 , Figure 1 The SEM image of the longitudinal section of the positive electrode sheet including lithium iron phosphate particles 6 and lithium supplement particles, the lithium supplement particles are Li5FeO4, Figure 1It can be seen that there is a second gap 73 between the lithium supplement agent matrix 71 and the lithium supplement agent coating layer 72 .

[0087] According to some embodiments of the present application, the matrix includes doping elements, and the doping elements include one or more of Al, Mn, Ti, Ni, Si, B, S, and P. Thus, the doping elements can improve the structural stability of the matrix, reduce the probability of the matrix structure being destroyed due to the release of lithium ions and then generating grain boundary cracks, reduce the side reaction between the matrix and the electrolyte, and reduce the dissolution of N elements in the matrix.

[0088] According to some embodiments of the present application, based on the total mass of the matrix, the mass proportion of the doping element may be 0.01%-0.2%. For example, it may be 0.01%, 0.05%, 0.1%, 0.15% or 0.2%, etc., or may be a range of any of the above values. Thus, the structural stability of the matrix is ​​improved.

[0089] According to some embodiments of the present application, N includes Fe elements, and the molar ratio of Fe atoms to O atoms in the lithium supplement is 1: (2-2.5). Specifically, the lithium supplement decomposes to produce oxygen, and the molar ratio of Fe atoms to O atoms in the lithium supplement is different depending on the degree of decomposition. Therefore, after the lithium supplement decomposes to release oxygen, when the internal pressure or temperature of the battery is too high, the explosion-proof valve can be pushed open by oxygen, thereby improving the safety of the battery.

[0090] According to some embodiments of the present application, the positive electrode film layer further includes a conductive agent, thereby improving the conductivity of the positive electrode film layer.

[0091] As an example, the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0092] In some embodiments, the positive electrode film 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.

[0093] [Negative electrode]

[0094] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0095] 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.

[0096] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, 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.).

[0097] In some embodiments, the negative electrode film layer may further include a binder. 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).

[0098] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0099] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0100] 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.

[0101] [Electrolytes]

[0102] 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.

[0103] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes a solvent, an electrolyte salt and an additive, the molar concentration of the electrolyte salt in the electrolyte solution is 1.1 mol / L-1.5 mol / L, the additive includes one or more of a phosphorus-containing additive, a fluorine-containing additive, and a sulfur-containing additive, and the solvent includes a cyclic carbonate and a linear carbonate.

[0104] According to some embodiments of the present application, the molar concentration of the electrolyte salt in the electrolyte may be 1.1 mol / L-1.5 mol / L, for example, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, etc., or may be a range consisting of any of the above numerical values.

[0105] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0106] According to some embodiments of the present application, the additive includes one or more of a phosphorus-containing additive, a fluorine-containing additive, and a sulfur-containing additive. Based on the total mass of the electrolyte, the sum of the masses of the phosphorus-containing additive, the fluorine-containing additive, and the sulfur-containing additive may account for 0.2%-2%. For example, it may be 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, etc., or may be a range consisting of any of the above numerical values.

[0107] According to some embodiments of the present application, the phosphorus-containing additive includes one or more of lithium difluorophosphate (LiDFP), tris(trimethylsilyl) phosphate (TMSP), triphenylphosphine oxide (TPPO), triethyl phosphate (TEP), trimethylolpropane (TMP), and trifluoroethyl ethylene phosphate (TFEOP).

[0108] According to some embodiments of the present application, the fluorine-containing additive includes one or more of fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), and perfluoroalkylethylene carbonate.

[0109] According to some embodiments of the present application, the electrolyte further includes a boron-containing additive, and the boron-containing additive includes one or more of tris(trimethylsilyl)borate (TMSB), lithium tetrafluoroborate (LiBF4), lithium dioxalatoborate (LiBOB), and lithium difluorooxalatoborate (LiDFOB).

[0110] According to some embodiments of the present application, the sulfur-containing additive includes one or more of ethylene sulfite (ES), propylene sulfite (PS), diethylene sulfate (DTD), 4-methylethylene sulfate (PCS), and 1,3-propylene sultone (PST).

[0111] According to some embodiments of the present application, the additive further includes a carbonate additive.

[0112] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate (VC).

[0113] According to some embodiments of the present application, the solvent includes cyclic carbonate and linear carbonate, and based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate is 15%-25%, and the mass proportion of the linear carbonate is 50%-70%. Thus, the stability of the electrolyte is improved.

[0114] According to some embodiments of the present application, the cyclic carbonate includes at least one of ethylene carbonate (EC) or propylene carbonate.

[0115] According to some embodiments of the present application, the linear carbonate includes at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate.

[0116] [Isolation film]

[0117] According to some embodiments of the present application, the isolation membrane includes: a base membrane, the material of the base membrane includes polyethylene; an adhesive layer, the adhesive layer is located on at least one side of the base membrane; and a ceramic layer, the ceramic layer is located on the side of the adhesive layer away from the base membrane. Thus, the adhesive layer can reduce the probability of wrinkles on the base membrane, and the ceramic layer can reduce the risk of puncture of the isolation membrane, thereby improving the safety of the battery.

[0118] According to some embodiments of the present application, the isolation film is disposed between the positive electrode sheet and the negative electrode sheet, and the ceramic layer is close to the positive electrode sheet, thereby reducing the probability of oxidation of the base film under high pressure conditions.

[0119] [Battery Cell]

[0120] In some embodiments, the battery may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0121] According to some embodiments of the present application, when the battery cell is charged to 4.5V at a rate of 0.05C, gas is generated in the battery cell, and the gas includes oxygen. Based on the total mass of the gas, the mass proportion of the oxygen is 30%-80%. Therefore, when the battery is overcharged, the lithium supplement decomposes to produce a large amount of oxygen, and the oxygen can push open the explosion-proof valve, thereby improving the safety of the battery cell.

[0122] As an example, the oxygen content may be 30%, 40%, 50%, 60%, 70% or 80%, etc., or may be a range consisting of any of the above values.

[0123] In the present application, the test method for oxygen content is to dig out the liquid injection hole of the battery cell, connect an external gas pipe to collect the gas generated by 4.5V overcharge, and use a JJG 700-1999 gas chromatograph to measure the oxygen content in the gas.

[0124] In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery 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.

[0125] The present application has no particular limitation on the shape of the battery, which may be cylindrical, square or any other shape. For example, Figure 2 The battery cell 5 is a square structure as an example.

[0126] In some embodiments, reference Figure 3 , 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.

[0127] In some embodiments, batteries may be assembled into a battery module. The number of batteries 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.

[0128] Figure 4 4 is an example of a battery module. Figure 4In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0129] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0130] 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.

[0131] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application.

[0132] Figure 5 and Figure 6 1 is a battery pack 1 as an example. Figure 5 and Figure 6 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.

[0133] In addition, the present application also provides an electric device, the electric device includes at least one of the battery cells, battery modules or battery packs provided in the present application, and the battery cells, the battery modules and the battery packs are used to provide electrical energy. The battery, battery module or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device 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.

[0134] As the electrical equipment, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0135] Figure 7 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, etc. In order to meet the power consumption device's requirements for high power and high energy density of the battery, a battery pack or a battery module can be used.

[0136] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery may be used as a power source.

[0137] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0138] Example 1

[0139] 1. Positive electrode

[0140] The positive electrode sheet includes a positive electrode current collector aluminum foil, and there are positive electrode films on both surfaces of the aluminum foil. The thickness of the single-sided positive electrode film layer is 100 μm, and the compaction density is 2.4 g / cm 3 The coating weight of the single-sided positive electrode film is 24 mg / cm 2 Based on the total mass of a single-sided positive electrode film layer, the positive electrode film layer includes 95.3% by mass of lithium iron phosphate material, 1.9% of lithium supplement Li5FeO4 (the surface is coated with carbon material with a thickness of about 100 nm. Based on the total mass of the lithium supplement, the mass proportion of the coating layer is 2.5%), 1% of conductive agent carbon black, and 1.8% of binder polyvinylidene fluoride (PVDF).

[0141] 2. Negative electrode

[0142] The negative electrode sheet includes a negative electrode current collector copper foil, and there are negative electrode films on both surfaces of the copper foil. The thickness of the single-sided negative electrode film is 57 μm, and the compaction density is 1.44 g / cm 3 The coating weight of the single-sided negative electrode film is 8.2 mg / cm 2 Based on the total mass of a single-sided negative electrode film layer, the negative electrode film layer includes 97.2% by mass of artificial graphite (94% degree of graphitization), 0.8% of conductive agent carbon black, 0.8% of binder styrene-butadiene rubber (SBR), and 1.2% of thickener sodium carboxymethyl cellulose (CMC-Na).

[0143] 3. Electrolyte

[0144] It includes solvents, electrolyte salts and additives. The solvents include EC, DMC and EMC, wherein the mass ratio of EC, DMC and EMC is 31:32:37. The electrolyte salt is LiPF6, and the molar concentration of LiPF6 is 1.2 mol / L. The additives include LiDFP, FEC, LIDFOB, LiBF4, PS and VC. Based on the total mass of the electrolyte, the mass proportion of LiDFP is 0.039%, the mass proportion of FEC is 0.23%, the mass proportion of LIDFOB is 0.0246%, the mass proportion of LiBF4 is 0.0091%, the mass proportion of PS is 0.54%, and the mass proportion of VC is 3.34%.

[0145] 4. Isolation film

[0146] Polyethylene film.

[0147] 5. Battery Cell

[0148] It includes a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

[0149] Performance Testing

[0150] 1. Energy density

[0151] At 25°C, the lithium-ion battery was charged at a constant current of 1 / 3C to 3.65V, charged at a constant voltage of 3.65V to a current of 0.05C, left to stand for 5 minutes, and then discharged at 1 / 3C to 2.5V. The discharge capacity was recorded as C. After measuring the size of the battery cell, its volume was calculated as V, and its volume energy density was obtained to be 3.22×C / V.

[0152] 2.45℃ Cycle Capacity Retention Rate

[0153] At 45°C, the lithium-ion battery was charged to 3.65V at a constant current of 1 / 3C, charged to a current of 0.05C at a constant voltage of 3.65V, left to stand for 5 minutes, and then discharged to 2.5V at a constant current of 1 / 3C, recording the discharge capacity C0; (2) the lithium-ion battery was then charged to 3.65V at a constant current of 1.0C, left to stand for 5 minutes, and then discharged to 2.5V at a constant current of 1 / 3C, recording the discharge capacity C1. Repeat the above step (2) 300 times, and record the discharge capacity C1 of the lithium-ion battery after the 300th cycle. 300 , capacity retention rate P 300 =C 300 / C0×100%.

[0154] 3. Test method for lithium content in positive electrode film

[0155] After discharging the battery cell to 2.5V at a rate of 0.04C, the battery cell is disassembled, the positive electrode sheet is taken out and cleaned with dimethyl carbonate (DMC) solvent, and the positive electrode powder is scraped out after drying. The lithium content in the positive electrode sheet can be tested using a Thermo ICAP7400 inductively coupled plasma-optical emission spectrometer (ICP-OES).

[0156] Example 2-Example 5

[0157] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the content of the lithium supplement agent in the positive electrode film layer is different.

[0158] Comparative Example 1

[0159] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the positive electrode film layer does not contain a lithium supplement.

[0160] Example 6

[0161] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the type of lithium supplement in the positive electrode film layer is different.

[0162] The differences between Examples 1 to 6 and Comparative Example 1 are shown in Table 1.

[0163] Table 1

[0164]

[0165] It can be seen from Examples 1 to 5 that the battery cells proposed in the present application have both high energy density and cycle capacity retention rate, indicating that the present application can adjust the lithium content in the positive electrode film layer and improve the cycle life and energy density of the battery cells by adding lithium supplements of different masses to the positive electrode film layer.

[0166] It can be seen from the comparison between Example 1, Example 2 and Comparative Example 1 that when the positive electrode film layer does not contain a lithium supplement, the energy density and cycle capacity retention rate of the battery cell are low; when the lithium content in the positive electrode film layer is 1.5%-1.9%, compared with not adding a lithium supplement to the positive electrode film layer, the energy density and cycle performance of the battery cell can be improved at the same time.

[0167] It can be seen from the comparison between Examples 3 to 5 and Comparative Example 1 that as the lithium content in the positive electrode film layer gradually increases, the energy density of the battery cell decreases slightly, and the cycle performance gradually improves. Because as the content of the lithium supplement in the positive electrode film layer gradually increases, the mass proportion of the corresponding lithium iron phosphate material gradually decreases, resulting in a slight decrease in the energy density of the battery cell. However, a battery cell with an energy density greater than or equal to 410Wh / L and a cycle capacity retention rate greater than or equal to 97.3% can still be obtained.

[0168] It can be seen from Examples 1 to 3 that when the lithium content in the positive electrode film layer is 4.0%-4.2%, the energy density of the battery cell is greater than or equal to 420Wh / L, and the cycle capacity retention rate is greater than or equal to 93%, indicating that when the content of the lithium supplement in the positive electrode film layer is 1.5%-2.5%, a battery cell with both high energy density and cycle performance can be obtained.

[0169] It can be seen from Examples 1 and 6 that different types of lithium supplements can be selected, and the lithium content in the positive electrode film layer can be controlled by adjusting the amount of the lithium supplement added, thereby obtaining a battery cell with good cycle performance and energy density.

[0170] Embodiment 7, Embodiment 8

[0171] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the particle size of the lithium iron phosphate is different.

[0172] Embodiment 9, Embodiment 10

[0173] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the particle size of the lithium supplement is different.

[0174] Example 11, Example 12

[0175] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the thickness of the coating layer on the surface of the lithium supplement agent is different.

[0176] The differences between Examples 7 and 12 are detailed in Table 2.

[0177] Table 2

[0178]

[0179] It can be seen from Examples 7 to 10 that when the lithium content in the positive electrode film layer is within an appropriate range, positive electrode active materials and lithium supplement agents of different particle sizes can obtain battery cells with higher energy density and cycle performance. On this basis, by adjusting the particle size of the positive electrode active material, the rate of lithium insertion and extraction can be increased, and the conductivity of the positive electrode active material can be improved; by adjusting the particle size of the lithium supplement agent, the specific surface area of ​​the lithium supplement agent can be reduced, and the side reactions between the lithium supplement agent and the electrolyte can be reduced.

[0180] It can be seen from Example 11 and Example 12 that the surface of the lithium supplement agent can also have a carbon coating layer of different thicknesses. By adjusting the thickness of the coating layer, the release rate of lithium ions can be increased and the lithium supplement effect can be improved.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: include: A positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprising a lithium iron phosphate material and a lithium supplement, and the lithium content of the positive electrode film layer is 4.0%-4.3% based on the total mass of the positive electrode film layer when the battery cell is discharged to 2.5V at a rate of 0.04C; A negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material, and the negative electrode active material comprising graphite; A separator is located between the positive electrode sheet and the negative electrode sheet.

2. The battery cell according to claim 1, characterized in that: When the battery cell is discharged to 2.5V at a rate of 0.04C, the lithium content is 4.0%-4.2% based on the total mass of the positive electrode film layer.

3. The battery cell according to claim 1 or 2, characterized in that: When the battery cell is discharged to 2.5V at a rate of 0.04C, the lithium content is 4.0%-4.1% based on the total mass of the positive electrode film layer.

4. The battery cell according to any one of claims 1 to 3, characterized in that: On a longitudinal section along the thickness direction of the positive electrode sheet, there is a first gap between the lithium iron phosphate material and the lithium supplement, and the first gap is 50nm-500nm.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The positive electrode film layer at least includes the following lithium supplement and lithium iron phosphate material: On the longitudinal section along the thickness direction of the positive electrode sheet, the average value of the longest diameter of the lithium supplement is a, the average value of the longest diameter of the lithium iron phosphate material is b, and they satisfy: 5μm≤ab≤11μm.

6. The battery cell according to claim 5, characterized in that: 1μm≤b≤2μm, 7μm≤a≤12μm.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The lithium supplement agent includes a matrix, and the matrix includes Li x N y O z , Among them, 1≤x≤6, 1≤y≤6, 2≤z≤12, and N includes one or more of Na element, Ni element, Co element, Mn element, Al element, and Fe element.

8. The battery cell according to any one of claims 1 to 6, characterized in that: The lithium supplement agent includes a matrix, and the matrix includes one or two of Li2NiO2 and Li5FeO4.

9. The battery cell according to any one of claims 1 to 6, characterized in that: The lithium supplement agent includes a matrix, and the matrix includes Li n NiO m and Li e FeO f One or two of the following, wherein 0<m≤2, 0≤n≤2, 0≤e≤5, 0<f≤4.

10. The battery cell according to any one of claims 1 to 6, characterized in that: The lithium supplement comprises a matrix, wherein the matrix comprises NiO m and Li p FeO q One or two of the following, where 0<m≤2, 0≤p≤1, 0<q≤2.

11. The battery cell according to any one of claims 1 to 10, characterized in that: The molar content of the Li element in the lithium supplement is greater than the molar content of the Li element in the lithium iron phosphate material.

12. The battery cell according to any one of claims 7 to 11, characterized in that: At least part of the surface of the substrate has a coating layer, and the coating layer includes one or more of the C element, the Al element, the Zr element, the P element, the S element, the Si element, and the B element.

13. The battery cell according to claim 12, characterized in that: The coating layer has a thickness of 10 nm to 200 nm.

14. The battery cell according to claim 12 or 13, characterized in that: There is a second gap between the substrate and the coating layer, and the second gap is 5nm-50nm.

15. The battery cell according to any one of claims 12 to 14, characterized in that: The matrix includes doping elements, and the doping elements include one or more of Al element, Mn element, Ti element, Ni element, Si element, B element, S element, and P element.

16. The battery cell according to claim 15, characterized in that: Based on the total mass of the substrate, the mass proportion of the doping element is 0.01%-0.2%.

17. The battery cell according to claim 7, characterized in that: N includes Fe element, and the molar ratio of Fe atoms to O atoms in the lithium supplement is 1:(2-2.5).

18. The battery cell according to any one of claims 1 to 17, characterized in that: The positive electrode film layer also includes a conductive agent, which includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

19. The battery cell according to any one of claims 1 to 18, characterized in that: When the battery cell is charged to 4.5V at a rate of 0.05C, gas is generated in the battery cell. The gas includes oxygen. Based on the total mass of the gas, the mass proportion of the oxygen is 30%-80%.

20. The battery cell according to any one of claims 1 to 19, characterized in that: Also includes: An electrolyte, the electrolyte comprising a solvent, an electrolyte salt and an additive, wherein the molar concentration of the electrolyte salt in the electrolyte is 1.1 mol / L-1.5 mol / L, the additive comprises one or more of a phosphorus-containing additive, a fluorine-containing additive and a sulfur-containing additive, and the solvent comprises a cyclic carbonate and a linear carbonate.

21. A battery device, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 20.

22. An electrical equipment, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 20, wherein the battery cell is used to provide electrical energy.

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