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 film layer, and the positive pole film layer comprises a lithium iron phosphate material and a lithium supplement agent; the negative electrode plate comprises a negative electrode film layer, the negative electrode film layer comprises a negative electrode active material, and the negative electrode active material comprises graphite; the isolating membrane is positioned between the positive pole piece and the negative pole piece; the electrolyte comprises lithium salts, the lithium salts comprise an organic lithium salt and an inorganic lithium salt, the organic lithium salt comprises at least one of fluorine-containing lithium sulfimide, fluorine-containing lithium oxalato borate and fluorine-containing lithium oxalato phosphate, the inorganic lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate and lithium fluorosulfonate, and the organic lithium salt comprises at least one of fluorine-containing lithium sulfimide, fluorine-containing lithium oxalato borate and fluorine-containing lithium oxalato phosphate. The mass ratio of the inorganic lithium salt to the organic lithium salt is (6-2): 1. As a result, a battery cell having both a long life and high power 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 not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace. Batteries in related technologies cannot meet the requirements of long life and high power at the same time. Summary of the invention

[0003] The first aspect of the present application provides a battery cell, the battery cell comprising a positive electrode plate, the positive electrode plate comprising a positive electrode film layer, the positive electrode film layer comprising a lithium iron phosphate material and a lithium supplement; a negative electrode plate, the negative electrode plate comprising a negative electrode film layer, the negative electrode film layer comprising a negative electrode active material, the negative electrode active material comprising graphite; a separator, the separator is located between the positive electrode plate and the negative electrode plate; and an electrolyte, the electrolyte comprising a lithium salt, the lithium salt comprising an organic lithium salt and an inorganic lithium salt, the organic lithium salt comprising at least one of fluorine-containing lithium sulfonyl imide, fluorine-containing lithium oxalate borate, and fluorine-containing lithium oxalate phosphate, the inorganic lithium salt comprising at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the mass ratio of the inorganic lithium salt to the organic lithium salt is (6-2):1. Therefore, on the one hand, while improving the cycle performance of the battery cell, a dense solid electrolyte interface film (CEI film) is formed on the surface of the lithium supplement, reducing the risk of oxidative decomposition of the electrolyte and improving the cycle performance of the battery; on the other hand, the combination of organic lithium salts and inorganic lithium salts can form a solid electrolyte interface film (SEI film) with low impedance and good toughness on the graphite surface, thereby improving the power performance of the battery cell.

[0004] According to some embodiments of the present application, the organic lithium salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluorosulfonyl)imide, and the mass proportion of the organic lithium salt is 1%-4% based on the total mass of the electrolyte.

[0005] According to some embodiments of the present application, the inorganic lithium salt includes lithium hexafluorophosphate, and based on the total mass of the electrolyte, the mass proportion of the inorganic lithium salt is 7.5%-12%.

[0006] Therefore, by making the content of organic lithium salt and inorganic lithium salt within the above range, a low-impedance and tough SEI film is formed on the negative electrode surface, the lithium ion deintercalation rate is increased, the probability of SEI film damage caused by graphite expansion is reduced, and the cycle performance of the battery cell is improved.

[0007] According to some embodiments of the present application, the OI value of the graphite is 2 to 5. Thus, by reducing the OI value of the graphite, the rate of lithium insertion and extraction is increased, and the dynamic performance of the battery cell is improved.

[0008] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 8 μm-14 μm. Thus, by reducing the volume average particle size of the graphite, the rate of lithium insertion and extraction is increased, and the dynamic performance of the battery cell is improved.

[0009] According to some embodiments of the present application, the graphite includes artificial graphite. Therefore, the number of active sites of artificial graphite is relatively small, which can increase the cycle life of the battery cell.

[0010] According to some embodiments of the present application, the lithium supplement comprises Li x M y O z , the M includes at least one of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn, 0<x≤5, 1≤y≤3, 2≤z≤8.

[0011] According to some embodiments of the present application, the lithium supplement includes at least one of Li2NiO2 and Li5FeO4.

[0012] According to some embodiments of the present application, the lithium supplement comprises Li n NiO m , Li e FeO f At least one of the following, wherein 0<m≤2, 0≤n≤2, 0≤e≤5, 0<f≤4.

[0013] According to some embodiments of the present application, the lithium supplement comprises NiO m and Li p FeO q At least one of the following, wherein 0<m≤2, 0≤p≤1, 0<q≤2.

[0014] Therefore, 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.

[0015] According to some embodiments of the present application, the electrolyte further comprises a solvent, and the solvent comprises a cyclic carbonate and a linear carbonate, thereby increasing the dielectric constant of the electrolyte, reducing the viscosity of the electrolyte, and increasing the migration rate of lithium ions.

[0016] According to some embodiments of the present application, 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 dielectric constant of the electrolyte is increased, the viscosity of the electrolyte is reduced, and the migration rate of lithium ions is increased.

[0017] According to some embodiments of the present application, the cyclic carbonate includes at least one of ethylene carbonate or propylene carbonate; and / or the linear carbonate includes at least one of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0018] According to some embodiments of the present application, the linear carbonate includes dimethyl carbonate and ethyl methyl carbonate, and based on the total mass of the electrolyte, the mass proportion of the dimethyl carbonate is 30%-40%, and the mass proportion of the ethyl methyl carbonate is 30%-40%. Thus, the viscosity of the electrolyte is reduced.

[0019] According to some embodiments of the present application, the electrolyte includes linear carboxylate, and the mass proportion of the linear carboxylate is 5%-15% based on the total mass of the electrolyte, thereby improving the conductivity of the electrolyte and the dynamic performance of the battery cell.

[0020] According to some embodiments of the present application, the linear carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate, and ethyl acetate, thereby improving the conductivity of the electrolyte and the dynamic performance of the battery cell.

[0021] According to some embodiments of the present application, the electrolyte further includes an additive, and the additive includes at least one of a fluorine-containing additive or a phosphorus-containing additive. Thus, a stable CEI film is formed on the positive electrode surface, reducing the risk of continuous gas generation caused by electrolyte decomposition due to high voltage in the formation stage.

[0022] According to some embodiments of the present application, the additive includes a fluorine-containing additive and a phosphorus-containing additive, and based on the total mass of the electrolyte, the sum of the mass of the fluorine-containing additive and the phosphorus-containing additive accounts for 0.05%-1%. Thus, a stable CEI film is formed on the positive electrode surface, reducing the risk of continuous gas generation caused by electrolyte decomposition due to high voltage in the formation stage.

[0023] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorine-containing additive is 0.05%-0.5%, and the mass proportion of the phosphorus-containing additive is 0.05%-0.5%. Thus, a stable CEI film is formed on the positive electrode surface, reducing the risk of continuous gas generation caused by electrolyte decomposition due to high voltage in the formation stage.

[0024] According to some embodiments of the present application, the fluorine-containing additive includes at least one of fluoroethylene carbonate, difluoroethylene carbonate, and perfluoroalkyl substituted ethylene carbonate; and / or the phosphorus-containing additive includes at least one of tris(trimethylsilyl)phosphate, triphenylphosphine oxide, tris(2,2,2-trifluoroethyl)phosphite, trimethylolpropane, tris(2,2,2-trifluoroethyl)phosphate, and 2-trifluoroethoxy-2-oxy-1,3,2-dioxaphospholane. Thus, a stable CEI film is formed on the positive electrode surface, reducing the risk of continuous gas generation caused by electrolyte decomposition due to high voltage in the formation stage.

[0025] According to some embodiments of the present application, the additive further comprises a carbonate additive, and the carbonate additive comprises at least one of vinylene carbonate, propylene carbonate, and vinyl ethylene carbonate. Thus, the content of polymer in the SEI film is increased, the stability of the SEI film is improved, and the cycle life of the battery monomer is increased.

[0026] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate, and based on the total mass of the electrolyte, the mass proportion of the vinylene carbonate is 0.5%-3%. Thus, a SEI film containing a polymer can be formed on the surface of the negative electrode, thereby improving the stability of the SEI film and increasing the life of the battery cell.

[0027] According to some embodiments of the present application, at least part of the surface of the lithium iron phosphate has a first carbon coating layer, and based on the total mass of the lithium iron phosphate, the mass proportion of the first carbon coating layer is 0.5%-1.5%; and / or at least part of the surface of the lithium supplement has a second carbon coating layer, and based on the total mass of the lithium supplement, the mass proportion of the second carbon coating layer is 1%-5%. Thus, carbon coating at least part of the surface of the lithium iron phosphate can improve the electronic conductivity of the pole piece; carbon coating at least part of the surface of the lithium supplement can reduce the number of active sites exposed by the lithium supplement and reduce the probability of reaction with the electrolyte.

[0028] According to some embodiments of the present application, based on the total mass of the positive electrode film layer, the mass proportion of the lithium supplement agent is 0.5%-5%, thereby improving the lithium supplement effect and the energy density of the battery cell.

[0029] According to some embodiments of the present application, the coating weight of the positive electrode film layer is 10 mg / cm 2 -25mg / cm 2 .

[0030] According to some embodiments of the present application, the compaction density of the positive electrode film layer is 2.2 g / cm 3 -2.6g / cm 3 .

[0031] Therefore, by setting the coating weight and the compaction density of the positive electrode film layer within the above ranges, the energy density of the battery cell is increased.

[0032] According to some embodiments of the present application, the coating weight of the negative electrode film layer is 5 mg / cm 2 -15mg / cm 2 .

[0033] According to some embodiments of the present application, the compaction density of the negative electrode film layer is 1.2 g / cm 3 -1.7g / cm 3 .

[0034] Therefore, by setting the coating weight and the compaction density of the negative electrode film layer within the above ranges, the energy density of the battery cell is increased.

[0035] According to some embodiments of the present application, the isolation film includes a base film, and at least one side of the base film has a coating, thereby reducing the risk of oxidation of the base film due to high pressure during formation.

[0036] According to some embodiments of the present application, the thickness of the isolation film is 7 μm-15 μm, thereby reducing the risk of oxidation of the base film due to high pressure during formation.

[0037] According to some embodiments of the present application, the liquid injection coefficient of the battery cell is 3g / Ah-3.8g / Ah, thereby increasing the content of electrolyte in the battery cell and improving the dynamic performance of the battery cell.

[0038] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0039] The third aspect of the present application provides an electrical device, including the battery cell provided by the first aspect of the present application or the battery device provided by the second aspect of the present application, wherein the battery cell or the battery device is used to provide electrical energy.

[0040] 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

[0041] 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:

[0042] Figure 1It is a schematic diagram of a battery cell according to an embodiment of the present application.

[0043] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown.

[0044] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0045] Figure 4 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0046] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0047] Figure 6 FIG. 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.

[0048] Description of reference numerals:

[0049] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] At present, judging from the development of the market situation, batteries are being used more and more widely. They can be applied to energy storage power systems such as hydropower, thermal power, wind power and solar power stations. However, the battery cells in related technologies cannot meet the requirements of long life and high power at the same time.

[0056] This application is intended to develop a battery cell with both long life and high power. 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 cycle performance of the battery cell is improved. However, the lithium supplement is easy to produce high-valent transition metal oxides in the battery cell, and these high-valent transition metal oxides have the risk of oxidizing the electrolyte. Adding fluorine-containing organic lithium salts to the electrolyte can, on the one hand, promote the formation of a dense CEI film on the surface of the high-valent transition metal oxide, reduce the risk of oxidizing the electrolyte, and improve the cycle performance of the battery cell; on the other hand, the combination of organic and inorganic lithium salts can optimize the SEI film composition on the graphite surface, forming a SEI film with low impedance and good toughness, which can not only increase the deintercalation rate of lithium ions in graphite, but also effectively improve the damage of the SEI film caused by the expansion of graphite during charging, and improve the power performance of the battery cell.

[0057] 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.

[0058] 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 film layer, the positive electrode film layer comprising a lithium iron phosphate material and a lithium supplement; a negative electrode plate, the negative electrode plate comprising a negative electrode film layer, the negative electrode film layer comprising a negative electrode active material, the negative electrode active material comprising graphite; a separator, the separator is located between the positive electrode plate and the negative electrode plate; and an electrolyte, the electrolyte comprising a lithium salt, the lithium salt comprising an organic lithium salt and an inorganic lithium salt, the organic lithium salt comprising at least one of fluorine-containing lithium sulfonyl imide, fluorine-containing lithium oxalate borate, and fluorine-containing lithium oxalate phosphate, the inorganic lithium salt comprising at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the mass ratio of the inorganic lithium salt to the organic lithium salt is (6-2):1.

[0059] The battery cell proposed in the present application improves the cycle performance of the battery cell by setting a lithium supplement in the positive electrode film layer. In order to reduce the risk of high-valent transition metal oxides formed by the lithium supplement to oxidize the electrolyte, an organic lithium salt is added to the electrolyte. The organic lithium salt can promote the formation of a dense CEI film on the surface of the high-valent transition metal oxide, reduce the direct contact between the transition metal oxide and the electrolyte, reduce the risk of the electrolyte being oxidized and decomposed, and improve the cycle performance of the battery cell. The combination of organic lithium salt and inorganic lithium salt can also form a low-impedance and tough SEI film on the surface of the negative electrode, thereby improving the power performance of the battery cell. Specifically, when the lower limit of the mass ratio of the inorganic lithium salt to the organic lithium salt is less than 2:1, the organic lithium salt content is too much, and there is a risk of corroding the positive electrode current collector and causing a significant increase in the internal resistance of the battery cell; when the upper limit of the mass ratio of the inorganic lithium salt to the organic lithium salt is greater than 6:1, the organic lithium salt content is less, and a low-impedance and tough SEI film cannot be formed, which is not conducive to the long life and high power of the battery cell.

[0060] In the present application, the test method for the content of organic lithium salt and inorganic lithium salt is: weigh a quantitative electrolyte in the battery monomer, dilute to 100 mL with ultrapure water, and perform automatic sampling detection by ion chromatography, and test according to the reference standard JY / T 020-1996 or GB / T6040-2002.

[0061] As an example, the mass ratio of the inorganic lithium salt to the organic lithium salt is (6-2):1, for example, it can be 6:1, 5:1, 4:1, 3.65:1, 3:1 or 2:1, etc., or it can be a range consisting of any of the above values.

[0062] According to some specific embodiments of the present application, the mass ratio of the inorganic lithium salt to the organic lithium salt is (4-3):1.

[0063]

Positive electrode

[0064] The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector along the thickness direction thereof, wherein the positive electrode film layer comprises a lithium iron phosphate material and a lithium supplementing agent.

[0065] 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.).

[0066] According to some embodiments of the present application, the lithium supplement comprises Li x M y O z , the M includes at least one of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn, 0<x≤5, 1≤y≤3, 2≤z≤8. 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 or 5, etc., or may be a range consisting of any of the above values.

[0068] As an example, y may be 1, 1.5, 2, 2.5 or 3, etc., or may be a range consisting of any of the above values.

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

[0070] According to some embodiments of the present application, the lithium supplement agent includes at least one 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 At least one 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 At least one of the following, wherein 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] In the present application, a method for detecting a lithium supplement is provided: a battery cell is discharged at 0.1C to 2.0V and then disassembled, a positive electrode plate is taken out for powder scraping, and the powder is tested by an X-ray diffractometer (XRD). At least one characteristic peak corresponding to the lithium supplement exists in the spectrum.

[0081] According to some embodiments of the present application, at least part of the surface of the lithium iron phosphate has a first carbon coating layer, and based on the total mass of the lithium iron phosphate, the mass proportion of the first carbon coating layer can be 0.5%-1.5%, for example, 0.5%, 0.7%, 0.9%, 1.1%, 1.3% or 1.5%, or can be a range composed of any of the above values. Thereby, the electronic conductivity between the lithium iron phosphate particles is improved, thereby improving the electronic conductivity of the pole piece.

[0082] According to some embodiments of the present application, at least part of the surface of the lithium supplement agent has a second carbon coating layer. Based on the total mass of the lithium supplement agent, the mass proportion of the second carbon coating layer can be 1%-5%, for example, it can be 1%, 2%, 3%, 4% or 5%, etc., or it can be a range composed of any of the above numerical values. Thus, the second carbon coating layer on the surface of the lithium supplement agent can accelerate the release of lithium ions in the lithium supplement agent, so as to quickly form pores on the pole piece, so that the electrolyte can quickly infiltrate the pole piece, improve the transmission efficiency of lithium ions, and improve the kinetic performance of the battery cell. According to some specific embodiments of the present application, based on the total mass of the lithium supplement agent, the mass proportion of the second carbon coating layer can be 1%-5%. According to some specific embodiments of the present application, based on the total mass of the lithium supplement agent, the mass proportion of the second carbon coating layer can be 2%-4%.

[0083] According to some embodiments of the present application, based on the total mass of the positive electrode film layer, the mass proportion of the lithium supplement agent can be 0.5%-5%, for example, 0.5%, 1%, 2%, 3%, 4% or 5%, or can be a range composed of any of the above values. Thus, the lithium supplement effect is improved.

[0084] 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.

[0085] In some embodiments, the positive electrode film 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. It may further be a composite of superconducting carbon and carbon nanotubes, thereby improving the electronic conductivity of the positive electrode sheet.

[0086] According to some embodiments of the present application, the coating weight of the positive electrode film layer can be 10 mg / cm 2 -25mg / cm 2 , for example, can be 10 mg / cm 2 , 12mg / cm 2 、14mg / cm 2 、16mg / cm 2 、18.5mg / cm 2 , 20mg / cm 2 , 22mg / cm 2 , 24mg / cm 2 or 25 mg / cm 2etc., or can be a range of any of the above values. Thus, while increasing the energy density of the battery cell, the tortuosity of the positive electrode sheet is reduced, the diffusion rate of lithium ions is increased, and the dynamic performance of the battery cell is improved. According to some specific embodiments of the present application, the coating weight of the positive electrode film layer can be 15 mg / cm 2 -20mg / cm 2 .

[0087] It should be noted that the coating weight of the positive electrode film layer referred to here refers to the coating weight of the positive electrode film layer on a single side of the positive electrode sheet.

[0088] According to some embodiments of the present application, the compaction density of the positive electrode film layer can be 2.2 g / cm 3 -2.6g / cm 3 , for example, can be 2.2 g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 or 2.6 g / cm 3 etc., or can be a range of any of the above values. Thus, while increasing the energy density of the battery cell, the tortuosity of the positive electrode sheet is reduced, the diffusion rate of lithium ions is increased, and the dynamic performance of the battery cell is improved. According to some specific embodiments of the present application, the compaction density of the positive electrode film layer is 2.3 g / cm 3 -2.5g / cm 3 .

[0089] The present application provides a method for testing the coating weight of the positive electrode film layer: the battery cell is disassembled to obtain the positive electrode sheet, for example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punched into small discs with an area of ​​S1, weighed, recorded as M1, and measured for its thickness H1. Then wipe off the positive electrode film layer of the weighed positive electrode sheet, weigh the weight of the positive electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (M1-M0) / S1, the thickness of the positive electrode film layer = H1-H0, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0090] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as lithium iron phosphate material, lithium supplement agent, conductive agent, 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.

[0091]

Negative electrode

[0092] 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.

[0093] 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.).

[0094] According to some embodiments of the present application, the coating weight of the negative electrode film layer is 5 mg / cm 2 -15mg / cm 2 , for example, can be 5 mg / cm 2 , 7mg / cm 2 、8.6mg / cm 2 , 9mg / cm 2 、11mg / cm 2 、13mg / cm 2 or 15mg / cm 2 etc., or can be any range of the above values. Thus, the energy density of the battery cell is improved. According to some specific embodiments of the present application, the coating weight of the negative electrode film layer can be 7 mg / cm 2 -11mg / cm 2 .

[0095] It should be noted that the coating weight of the negative electrode film layer referred to here refers to the coating weight of the negative electrode film layer on a single side of the negative electrode sheet.

[0096] According to some embodiments of the present application, the compaction density of the negative electrode film layer can be 1.2 g / cm 3 -1.7g / cm 3 , for example, can be 1.2 g / cm 3 , 1.32g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 or 1.7 g / cm 3 The above-mentioned arbitrary numerical ranges may also be used.

[0097] The test method for the coating weight of the negative electrode film layer of the present application refers to the test method for the coating weight of the positive electrode film layer.

[0098] According to some embodiments of the present application, the compaction density of the negative electrode film layer may be the compaction density of the negative electrode film layer in the negative electrode sheet corresponding to the battery cell in a 100% SOC state.

[0099] According to some embodiments of the present application, the compaction density of the negative electrode film layer may be the compaction density of the negative electrode film layer in the negative electrode sheet corresponding to the battery cell in a 0% SOC state.

[0100] According to some embodiments of the present application, the negative electrode film layer includes graphite, and the volume average particle size Dv50 of the graphite is 8 μm-14 μm. Thus, the volume average particle size of the graphite is reduced, the rate of lithium ion insertion and extraction between graphite layers is increased, the impedance of the battery cell is reduced, and the dynamic performance is improved.

[0101] As an example, the volume average particle size Dv50 of the graphite may be 8 μm, 10 μm, 12 μm, 14 μm, etc., or may be within a range consisting of any of the above values.

[0102] In the present application, Dv50 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, for example, with reference to the standard GB / T 19077-2016 / ISO 13320:2009, and is measured using a laser particle size analyzer (Malvern Master Size 2000).

[0103] According to some embodiments of the present application, the negative electrode film layer includes graphite, and the graphite material has a layered structure. The OI value can measure the ability of the graphite material itself to deintercalate lithium ions, and the OI value of graphite is 2-5. Therefore, by reducing the OI value of graphite, the dynamic performance of the battery is improved.

[0104] As an example, the OI value of the graphite may be 2, 3, 4 or 5, or may be a range consisting of any of the above values.

[0105] According to some embodiments of the present application, the graphite includes artificial graphite. Therefore, compared with natural graphite, artificial graphite has fewer surface active sites, which can increase the life of the battery cell.

[0106] 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).

[0107] In some embodiments, the negative electrode film layer may further optionally include a conductive agent. 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. It may further be selected to use superconducting carbon and carbon nanotubes in combination to further improve the conductivity of the negative electrode film layer and the conductivity between the negative electrode film layer and the negative electrode current collector.

[0108] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0109] 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.

[0110]

Electrolyte

[0111] Typically, the electrolyte includes a solvent, a lithium salt and additives.

[0112] According to some embodiments of the present application, the total mass proportion of the lithium salt in the electrolyte can be 8%-13%. For example, it can be 8%, 9%, 10%, 11%, 12% or 13%, etc., or it can be a range composed of any of the above values. Thereby, the ion conductivity of the electrolyte is improved. According to some specific embodiments of the present application, the total mass proportion of the lithium salt can be 10%-12%.

[0113] According to some embodiments of the present application, the inorganic lithium salt includes lithium hexafluorophosphate, and the mass proportion of the inorganic lithium salt can be 7.5%-12% based on the total mass of the electrolyte, thereby improving the ionic conductivity of the electrolyte. By making the content of the inorganic lithium salt within the above range, a low-impedance and moderately hard SEI film is formed on the surface of the negative electrode, effectively inhibiting the expansion of the pole piece during the cycle caused by the expansion of graphite, and improving the cycle performance of the battery cell.

[0114] As an example, the mass percentage of the inorganic lithium salt may be 7.5%, 8%, 9%, 10%, 11% or 12%, etc., or may be a range consisting of any of the above values.

[0115] According to some embodiments of the present application, the organic lithium salt includes at least one of lithium bis(fluorosulfonyl)imide (LIFSI) and lithium bis(trifluorosulfonyl)imide (LITFSI), and the mass proportion of the organic lithium salt can be 1%-4% based on the total mass of the electrolyte. Thus, the impedance of the SEI film is reduced, the ionic conductivity of the SEI film is increased, and the kinetic performance of the battery is improved. At the same time, the probability of fluorine and the positive electrode current collector aluminum forming aluminum fluoride due to excessive content of the organic lithium salt is reduced, and the risk of corroding the positive electrode current collector is reduced.

[0116] As an example, based on the total mass of the electrolyte, the mass proportion of the organic lithium salt may be 1%, 2%, 3% or 4%, etc., or may be a range consisting of any of the above values.

[0117] According to some embodiments of the present application, the solvent includes cyclic carbonate and linear carbonate, thereby increasing the dielectric constant of the electrolyte, reducing the viscosity of the electrolyte, and increasing the migration rate of lithium ions.

[0118] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate can be 15%-25%, and the mass proportion of the linear carbonate can be 50%-70%. Thus, the dielectric constant of the electrolyte is increased, the viscosity of the electrolyte is reduced, and the migration rate of lithium ions is increased.

[0119] As an example, based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate can be 15%, 17%, 19%, 21%, 23% or 25%, etc., or can be a range consisting of any of the above values.

[0120] According to some specific embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate may be 22%-25%.

[0121] As an example, based on the total mass of the electrolyte, the mass proportion of the linear carbonate can be 50%, 55%, 60%, 65% or 70%, etc., or can be a range consisting of any of the above values.

[0122] According to some embodiments of the present application, the cyclic carbonate includes at least one of ethylene carbonate (EC) or propylene carbonate.

[0123] According to some embodiments of the present application, the linear carbonate includes at least one of dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0124] According to some embodiments of the present application, the linear carbonate includes dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), and based on the total mass of the electrolyte, the mass proportion of the dimethyl carbonate may be 30%-40%, and the mass proportion of the ethyl methyl carbonate may be 30%-40%. Thus, the viscosity of the electrolyte is reduced.

[0125] As an example, based on the total mass of the electrolyte, the mass proportion of DMC can be 30%, 32%, 34%, 36%, 38% or 40%, etc., or can be a range consisting of any of the above values.

[0126] As an example, based on the total mass of the electrolyte, the mass proportion of EMC can be 30%, 32%, 34%, 36%, 38% or 40%, etc., or can be a range consisting of any of the above values.

[0127] According to some embodiments of the present application, the electrolyte may further include a linear carboxylate, and the mass proportion of the linear carboxylate is 5%-15% based on the total mass of the electrolyte. Thus, the conductivity of the electrolyte is improved, and the dynamic performance of the battery cell is improved; and the content of the linear carboxylate is controlled not to exceed 15%, thereby improving the high temperature stability of the electrolyte.

[0128] As an example, the mass proportion of the linear carboxylic acid ester may be 5%, 7%, 9%, 11%, 13% or 15%, etc., or may be a range consisting of any of the above values.

[0129] According to some embodiments of the present application, the linear carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate, and ethyl acetate, thereby improving the conductivity of the electrolyte and the dynamic performance of the battery cell.

[0130] According to some embodiments of the present application, the decomposition voltage of the lithium supplement is relatively high. In order to improve the high-voltage resistance of the electrolyte, the electrolyte further includes an additive, and the additive includes at least one of a fluorine-containing additive or a phosphorus-containing additive. As a result, the above-mentioned types of additives can be decomposed in priority to the solvent, and a stable CEI film can be formed after decomposition, reducing the risk of transition metal dissolution in the positive electrode material under high-voltage conditions, reducing the risk of oxidative decomposition of the electrolyte, improving the cycle stability of the electrolyte, and improving the cycle performance of the battery cell.

[0131] According to some embodiments of the present application, the additive includes a fluorine-containing additive and a phosphorus-containing additive, and based on the total mass of the electrolyte, the sum of the masses of the fluorine-containing additive and the phosphorus-containing additive accounts for 0.05%-1%. Thus, by making the sum of the masses of the fluorine-containing additive and the phosphorus-containing additive within the above range, the stability of the CEI film is improved, the risk of the electrolyte being oxidized and decomposed during the formation stage is reduced, the cycle stability of the electrolyte is improved, and the cycle performance of the battery cell is improved.

[0132] In the present application, the type and content of electrolyte additives can be tested with reference to GB / T 9722-2006 Chemical Reagent Gas Chromatography. Specifically, a certain amount of electrolyte is tested using a gas chromatograph, and the different adsorption and desorption capacities of the components of the electrolyte in the chromatographic column are utilized to separate the components of the electrolyte, and the separated samples are tested using a gas chromatograph-mass spectrometer (GC-MS).

[0133] As an example, the sum of the masses of the fluorine-containing additive and the phosphorus-containing additive may account for 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, or may be a range consisting of any of the above values.

[0134] According to some specific embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorine-containing additive is 0.05%-0.5%, and the mass proportion of the phosphorus-containing additive is 0.05%-0.5%. Thus, the stability of the CEI membrane is improved, the risk of high-voltage oxidation of the electrolyte in the formation stage is reduced, the cycle stability of the electrolyte is improved, and the cycle performance of the battery cell is improved.

[0135] As an example, the mass proportion of the fluorine-containing additive may be 0.05%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, etc., or may be a range consisting of any of the above values.

[0136] As an example, the mass proportion of the phosphorus-containing additive may be 0.05%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, etc., or may be a range consisting of any of the above values.

[0137] According to some embodiments of the present application, the fluorine-containing additive includes at least one of fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), and perfluoroalkylethylene carbonate.

[0138] According to some embodiments of the present application, the phosphorus-containing additive includes at least one of tris(trimethylsilyl) phosphate (TMSP), triphenylphosphine oxide (TPPO), tris(2,2,2-trifluoroethyl) phosphate (TFEP), trimethylolpropane (TMP), and 2-trifluoroethoxy-2-oxy-1,3,2-dioxaphospholane (TFEOP).

[0139] According to some embodiments of the present application, the additive further comprises a carbonate additive, and the carbonate additive comprises at least one of vinylene carbonate (VC), propylene carbonate, and vinyl ethylene carbonate. Thus, by adding carbonate additives to the electrolyte, a SEI film containing a polymer can be formed on the surface of the negative electrode, thereby improving the stability of the SEI film and increasing the life of the battery cell.

[0140] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate, and based on the total mass of the electrolyte, the mass proportion of the vinylene carbonate can be 0.5%-3%. Thus, by adding carbonate additives to the electrolyte, a SEI film containing a polymer can be formed on the surface of the negative electrode, thereby improving the stability of the SEI film and increasing the life of the battery cell.

[0141] As an example, based on the total mass of the electrolyte, the mass proportion of the vinylene carbonate can be 0.5%, 1%, 1.5%, 2%, 2.5% or 3%, etc., or can be a range composed of any of the above values. According to some specific embodiments of the present application, the mass proportion of the vinylene carbonate can be 1%-2%.

[0142] According to some embodiments of the present application, the injection coefficient of the battery cell is 3g / Ah-3.8g / Ah. For example, it can be 3g / Ah, 3.2g / Ah, 3.4g / Ah, 3.6g / Ah or 3.8g / Ah, etc., or can be a range of any of the above values. Thereby, the dynamic performance and cycle life of the battery are improved.

[0143] [Isolation film]

[0144] 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.

[0145] According to some embodiments of the present application, the isolation film includes a base film, at least one side of the base film has a coating, and the material of the base film includes at least one of polyethylene or polypropylene, thereby reducing the risk of the isolation film being oxidized under high pressure conditions.

[0146] According to some embodiments of the present application, the coating may be a ceramic coating.

[0147] According to some embodiments of the present application, the thickness of the isolation film may be 7 μm-15 μm, for example, 7 μm, 9 μm, 11 μm, 13 μm or 15 μm, or a range consisting of any of the above values.

[0148] 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.

[0149] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0150] 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.

[0151] 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 battery cell 5 is a square structure as an example.

[0152] 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.

[0153] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0154] 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, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0155] Figure 3 4 is an example of a battery module. Figure 3In 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.

[0156] 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.

[0157] 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.

[0158] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 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.

[0159] In addition, the present application also provides an electric 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 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.

[0160] As the electrical equipment, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0161] Figure 6 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.

[0162] 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 cell may be used as a power source.

[0163] 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.

[0164] Example 1

[0165] 1. Positive electrode

[0166] The positive electrode sheet includes a positive electrode current collector aluminum foil, and there are positive electrode film layers on both surfaces of the aluminum foil, with a compaction density of 2.39g / cm 3 The coating weight of the single-sided positive electrode film is 18.5 mg / cm 2 Based on the total mass of the single-sided positive electrode film layer, the positive electrode film layer includes 94.5% lithium iron phosphate material, 2.5% lithium supplement Li2NiO2, 0.8% conductive agent carbon black, and 2.2% binder polyvinylidene fluoride (PVDF) by mass. The surface of the lithium iron phosphate has a first carbon coating layer. Based on the total mass of the lithium iron phosphate, the mass proportion of the first carbon coating layer is 1.5%.

[0167] 2. Negative electrode

[0168] The negative electrode sheet includes a negative electrode current collector copper foil, and the two surfaces of the copper foil have negative electrode film layers with a compaction density of 1.32g / cm 3 The coating weight of the single-sided negative electrode film is 8.6 mg / cm 2 Based on the total mass of a single-sided negative electrode film layer, the negative electrode film layer includes 96.6% by mass of artificial graphite (OI value is 3.63), 0.4% of conductive agent carbon black, 1.8% of binder styrene-butadiene rubber (SBR), and 1.2% of thickener sodium carboxymethyl cellulose (CMC-Na).

[0169] 3. Electrolyte

[0170] The electrolyte includes solvents, electrolyte salts and additives. The solvents include EC, DMC and EMC, wherein the mass ratio of EC, DMC and EMC is 24:38:38. The additives include TMSP, FEC and VC, wherein, based on the total mass of the electrolyte, the mass proportion of TMSP is 0.23%, the mass proportion of FEC is 0.12%, and the mass proportion of VC is 1.39%; the electrolyte salts are LiPF6 and LIFSI, wherein, based on the total mass of the electrolyte, the mass proportion of LiPF6 is 9.383%, and the mass proportion of LIFSI is 2.57%.

[0171] 4. Isolation film

[0172] Polypropylene film, thickness 12μm.

[0173] 5. Battery Cell

[0174] A battery cell includes a positive electrode plate, a separator, a negative electrode plate and an electrolyte.

[0175] Performance Testing

[0176] 1.DCR test

[0177] At 25°C, charge the battery cell at 1 / 3C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C, leave it for 5 minutes, discharge at 1 / 3C constant current for 90 minutes, leave it for 120 minutes and record the voltage V1. Then discharge at 4C for 30s and record the voltage V2, then (V2-V1) / 4C, get the internal resistance DCR of the battery cell.

[0178] 2.1000 cycle capacity retention rate

[0179] At 25°C, charge the corresponding battery cell at a constant current of 1 / 3C to 3.65V, then charge at a constant voltage of 3.65V to a current of 0.05C, leave for 5 minutes, and then discharge at 1 / 3C to 2.5V. The resulting capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery cell, and record the discharge capacity C0 of the battery cell after the nth cycle. n , then the battery cell capacity retention rate P after each cycle n =C n / C0×100%. In this test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 1000th cycle corresponds to n=1000.

[0180] 3. Capacity retention rate after 150 days storage at 60℃

[0181] At 25°C, the corresponding battery cell is charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left for 5 minutes, and then discharged to 2.5V at 1 / 3C. The obtained capacity is recorded as the initial capacity C0. Charge to 3.65V at 1 / 3C and then constant voltage to 0.05C, then take out the battery cell after 150 days in a 60°C constant temperature oven, and discharge to 2.5V at 1 / 3C at room temperature. The battery cell after removal is charged to 3.65V at 25°C at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left for 5 minutes, and then discharged to 2.5V at 1 / 3C, and the capacity C is recorded. n , the capacity retention rate is (Cn / C0)×100%.

[0182] Example 2, Example 3, Comparative Example 2, Comparative Example 3

[0183] The positive electrode sheet, negative electrode sheet, electrolyte solvent and additives in the battery cell are the same as those in Example 1, except that the mass proportions of LiPF6 and LIFSI are different, and the mass ratios of inorganic lithium salt and organic lithium salt are different.

[0184] Example 4

[0185] The positive electrode sheet, negative electrode sheet, electrolyte solvent and additives in the battery cell are the same as those in Example 1, except that the organic lithium salt is LITFSI.

[0186] Comparative Example 1

[0187] 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.

[0188] The differences between Example 1-Example 4 and Comparative Example 1-Comparative Example 3 are shown in Table 1:

[0189] Table 1

[0190]

[0191] It can be seen from the comparison between Examples 1 to 3 and Comparative Examples 1 to 3 that the battery cell proposed in the present application has a lower internal resistance and a higher cycle capacity retention rate and a higher high-temperature capacity retention rate. This indicates that the present application can improve the high-temperature cycle performance of the battery cell by adding a lithium supplement to the positive electrode film layer; by controlling the relative content of the organic lithium salt and the inorganic lithium salt in the electrolyte within a reasonable numerical range, the side reaction between the transition metal oxide formed by the lithium supplement and the electrolyte can be reduced, thereby improving the cycle performance of the battery; at the same time, the SEI formed by the combination of the organic lithium salt and the inorganic lithium salt has a low impedance, which can increase the rate of lithium ion deintercalation in graphite and improve the power performance of the battery cell.

[0192] It can be seen from Example 4 and Example 1 that different types of organic lithium salts have the effect of improving the cycle performance and power performance of battery cells.

[0193] Embodiment 5, Embodiment 6

[0194] The positive electrode sheet, negative electrode sheet, electrolyte solvent and additives in the battery cell are the same as those in Example 1, except that the content of TMSP is different.

[0195] Embodiment 7, Embodiment 8

[0196] The positive electrode sheet, negative electrode sheet, electrolyte solvent and additives in the battery cell are the same as those in Example 1, except that the content of FEC is different.

[0197] The differences between Examples 5 and 8 are detailed in Table 2.

[0198] Table 2

[0199]

[0200] It can be seen from Examples 1 and 5 to 8 that by controlling the content of phosphorus-containing additives and fluorine-containing additives in the electrolyte, the internal resistance, cycle capacity retention rate and high-temperature capacity retention rate of the battery cell can be adjusted, thereby obtaining a battery cell with both long life and low internal resistance.

[0201] Embodiment 9, Embodiment 10

[0202] The positive electrode sheet, negative electrode sheet, electrolyte salt and additives in the battery cell are the same as those in Example 1, except that the electrolyte solvent also includes methyl acetate (MA), and the content of MA is different, see Table 3 for details.

[0203] Table 3

[0204]

[0205]

[0206] It can be seen from Example 1, Example 9 and Example 10 that by adding different contents of MA into the electrolyte, the internal resistance of the battery cell can be further reduced, thereby improving the dynamic performance of the battery cell.

[0207] Embodiment 11

[0208] 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 is different.

[0209] Example 12, Example 13

[0210] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the compaction density of the positive electrode film layer is different.

[0211] The types of lithium supplements in Example 11 and the compaction densities of the positive electrode film layers in Examples 12 and 13 are detailed in Table 4.

[0212] Table 4

[0213]

[0214] It can be seen from Example 1 and Example 11 that different types of lithium supplements can improve the cycle performance of the battery.

[0215] It can be seen from Example 1, Example 12 and Example 13 that a battery cell having both long life and low internal resistance can be obtained by forming positive electrode film layers with different compaction densities.

[0216] Example 14 and Example 15

[0217] The positive electrode sheet and electrolyte in the battery cell are the same as those in Example 1, except that the OI value of the negative electrode graphite is different.

[0218] Example 16 and Example 17

[0219] The positive electrode sheet and electrolyte in the battery cell are the same as those in Example 1, except that the volume average particle size of the negative electrode graphite is different.

[0220] Example 18 and Example 19

[0221] The positive electrode sheet and electrolyte in the battery cell are the same as those in Example 1, except that the compaction density of the negative electrode film layer is different.

[0222] The differences in the negative electrode plates in Examples 14 to 19 are detailed in Table 5.

[0223] Table 5

[0224]

[0225]

[0226] It can be seen from Example 1, Example 14 and Example 15 that by reducing the OI value of graphite, the internal resistance of the battery cell can be reduced, and at the same time, the battery cell has excellent cycle performance.

[0227] It can be seen from Example 1, Example 16 and Example 17 that by reducing the volume average particle size of graphite, the internal resistance of the battery monomer can be reduced, and at the same time, the battery monomer has excellent cycle performance.

[0228] It can be seen from Example 1, Example 18 and Example 19 that a battery cell having both long life and low internal resistance can be obtained by forming negative electrode film layers with different compaction densities.

[0229] 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 film layer, the positive electrode film layer comprising a lithium iron phosphate material and a lithium supplement; A negative electrode sheet, the negative electrode sheet comprising a negative electrode film layer, the negative electrode film layer comprising a negative electrode active material, and the negative electrode active material comprising graphite; a separator, the separator being located between the positive electrode sheet and the negative electrode sheet; and An electrolyte, wherein the electrolyte includes a lithium salt, wherein the lithium salt includes an organic lithium salt and an inorganic lithium salt, wherein the organic lithium salt includes at least one of fluorine-containing lithium sulfonyl imide, fluorine-containing lithium oxalate borate, and fluorine-containing lithium oxalate phosphate, and the inorganic lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the mass ratio of the inorganic lithium salt to the organic lithium salt is (6-2):

1.

2. The battery cell according to claim 1, characterized in that: The organic lithium salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluorosulfonyl)imide. Based on the total mass of the electrolyte, the mass proportion of the organic lithium salt is 1%-4%.

3. The battery cell according to claim 1 or 2, characterized in that: The inorganic lithium salt includes lithium hexafluorophosphate, and based on the total mass of the electrolyte, the mass proportion of the inorganic lithium salt is 7.5%-12%.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The OI value of the graphite is 2-5.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The volume average particle size Dv50 of the graphite is 8 μm-14 μm.

6. The battery cell according to any one of claims 1 to 5, characterized in that: The graphite includes artificial graphite.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The lithium supplement comprises Li x M y O z , the M includes at least one of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn, 0<x≤5, 1≤y≤3, 2≤z≤8.

8. The battery cell according to any one of claims 1 to 6, characterized in that: The lithium supplement includes at least one of Li2NiO2 and Li5FeO4.

9. The battery cell according to any one of claims 1 to 6, characterized in that: The lithium supplement comprises Li n NiO m , Li e FeO f At least one 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 NiO m and Li p FeO q At least one of the following, wherein 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 electrolyte further includes a solvent, and the solvent includes a cyclic carbonate and a linear carbonate.

12. The battery cell according to claim 11, characterized in that: 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%.

13. The battery cell according to claim 11 or 12, characterized in that: The cyclic carbonate comprises at least one of ethylene carbonate or propylene carbonate; and / or The linear carbonate includes at least one of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

14. The battery cell according to any one of claims 11 to 13, characterized in that: The linear carbonate includes dimethyl carbonate and ethyl methyl carbonate. Based on the total mass of the electrolyte, the mass proportion of the dimethyl carbonate is 30%-40%, and the mass proportion of the ethyl methyl carbonate is 30%-40%.

15. The battery cell according to any one of claims 11 to 14, characterized in that: The electrolyte includes linear carboxylic acid ester, and based on the total mass of the electrolyte, the mass proportion of the linear carboxylic acid ester is 5%-15%.

16. The battery cell according to claim 15, characterized in that: The linear carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate and ethyl acetate.

17. The battery cell according to any one of claims 1 to 16, characterized in that: The electrolyte further includes an additive, wherein the additive includes at least one of a fluorine-containing additive and a phosphorus-containing additive.

18. The battery cell according to claim 17, characterized in that: The additives include fluorine-containing additives and phosphorus-containing additives. Based on the total mass of the electrolyte, the sum of the mass of the fluorine-containing additive and the phosphorus-containing additive accounts for 0.05%-1%.

19. The battery cell according to claim 17 or 18, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the fluorine-containing additive is 0.05%-0.5%, and the mass proportion of the phosphorus-containing additive is 0.05%-0.5%.

20. The battery cell according to any one of claims 17 to 19, characterized in that: The fluorine-containing additive comprises at least one of fluoroethylene carbonate, difluoroethylene carbonate and perfluoroalkylethylene carbonate; and / or The phosphorus-containing additive includes at least one of tris(trimethylsilyl)phosphate, triphenylphosphine oxide, tris(2,2,2-trifluoroethyl)phosphite, trimethylolpropane, tris(2,2,2-trifluoroethyl)phosphate, and 2-trifluoroethoxy-2-oxy-1,3,2-dioxaphospholane.

21. The battery cell according to any one of claims 17 to 20, characterized in that: The additives further include carbonate additives, and the carbonate additives include at least one of vinylene carbonate, propylene carbonate, and vinyl ethylene carbonate.

22. The battery cell according to claim 21, characterized in that: The carbonate additive includes vinylene carbonate. Based on the total mass of the electrolyte, the mass proportion of the vinylene carbonate is 0.5%-3%.

23. The battery cell according to any one of claims 1 to 22, characterized in that: At least part of the surface of the lithium iron phosphate has a first carbon coating layer, and based on the total mass of the lithium iron phosphate, the mass proportion of the first carbon coating layer is 0.5%-1.5%; and / or At least part of the surface of the lithium supplement agent has a second carbon coating layer, and based on the total mass of the lithium supplement agent, the mass proportion of the second carbon coating layer is 1%-5%.

24. The battery cell according to any one of claims 1 to 23, characterized in that: Based on the total mass of the positive electrode film layer, the mass proportion of the lithium supplement agent is 0.5%-5%.

25. The battery cell according to any one of claims 1 to 24, characterized in that: The coating weight of the positive electrode film layer is 10 mg / cm 2 -25mg / cm 2 .

26. The battery cell according to any one of claims 1 to 25, characterized in that: The compaction density of the positive electrode film layer is 2.2 g / cm 3 -2.6g / cm 3 .

27. The battery cell according to any one of claims 1 to 26, characterized in that: The coating weight of the negative electrode film layer is 5 mg / cm 2 -15mg / cm 2 .

28. The battery cell according to any one of claims 1 to 27, characterized in that: The compaction density of the negative electrode film layer is 1.2 g / cm 3 -1.7g / cm 3 .

29. The battery cell according to any one of claims 1 to 28, characterized in that: The isolation film includes a base film, at least one side of which has a coating layer.

30. The battery cell according to any one of claims 1 to 29, characterized in that: The thickness of the isolation film is 7 μm-15 μm.

31. The battery cell according to any one of claims 1 to 30, characterized in that: The liquid injection coefficient of the battery monomer is 3g / Ah-3.8g / Ah.

32. A battery device, characterized in that: Comprising the battery cell according to any one of claims 1 to 31, the battery device is at least one of a battery module, a battery pack, and an energy storage device.

33. An electrical equipment, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 31 or the battery device according to claim 32, wherein the battery cell or the battery device is used to provide electrical energy.

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