Battery cell, battery apparatus, and electric device

Abstract

Provided are a battery cell, a battery apparatus, and an electric device. The battery cell comprises: a positive electrode sheet, the positive electrode sheet comprising a positive electrode film layer, and the positive electrode film layer comprising a lithium iron phosphate material and a lithium supplementing agent; 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, 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 lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, and lithium difluoro(oxalato)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 being (6-2):1. Therefore, battery cells having long service life and high power can be obtained.

Description

Battery cells, battery devices and electrical equipment Technical Field

[0001] This application relates to the field of batteries, specifically to battery cells, battery devices, and electrical equipment. Background Technology

[0002] Batteries are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. However, current battery technologies cannot simultaneously meet the demands for long lifespan and high power output. Summary of the Invention

[0003] The first aspect of this application provides a battery cell, the battery cell comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode film layer comprising lithium iron phosphate material and a lithium replenishing agent; a negative electrode sheet, the negative electrode sheet comprising a negative electrode film layer comprising a negative electrode active material comprising graphite; a separator membrane located between the positive electrode sheet and the negative electrode sheet; and an 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 lithium fluorosulfonylimide, lithium fluorooxalate borate, and lithium fluorooxalate phosphate, the inorganic lithium salt comprising at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium fluorosulfonate, the mass ratio of the inorganic lithium salt to the organic lithium salt being (6-2):1. Thus, on the one hand, while improving the cycle performance of the battery cell, a dense solid electrolyte interphase (CEI) film is formed on the surface of the lithium replenisher, reducing the risk of electrolyte oxidation and decomposition and improving the cycle performance of the battery; on the other hand, the combination of organic lithium salt and inorganic lithium salt can form a solid electrolyte interphase (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 this application, the organic lithium salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluorosulfonyl)imide, and the mass percentage of the organic lithium salt is 1%-4% based on the total mass of the electrolyte.

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

[0006] Therefore, by keeping the contents of organic and inorganic lithium salts within the above range, a low-resistance and tough SEI film is formed on the negative electrode surface, which improves the lithium ion insertion / extraction rate, reduces the probability of SEI film damage caused by graphite expansion, and improves the cycle performance of the battery cell.

[0007] According to some embodiments of this application, the OI value of the graphite is 2-5. Therefore, by reducing the OI value of the graphite, the lithium insertion / extraction rate is increased, thereby improving the kinetic performance of the battery cell.

[0008] According to some embodiments of this application, the volume average particle size Dv50 of the graphite is 8 μm-14 μm. Therefore, by reducing the volume average particle size of the graphite, the lithium insertion / extraction rate is increased, thereby improving the kinetic performance of the battery cell.

[0009] According to some embodiments of this application, the graphite includes artificial graphite. Therefore, artificial graphite has a relatively small number of active sites, which can improve the cycle life of the battery cell.

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

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

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

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

[0014] Therefore, the decomposition of lithium replenishment agents can compensate for the active lithium ions consumed in the formation of the SEI film, thereby improving the initial efficiency and energy density of the battery cell.

[0015] According to some embodiments of this application, the electrolyte further includes a solvent, which comprises cyclic carbonates and linear carbonates. This increases the dielectric constant of the electrolyte, reduces its viscosity, and improves the migration rate of lithium ions.

[0016] According to some embodiments of the present application, the mass percentage of the cyclic carbonate is 15-25% and the mass percentage of the linear carbonate is 50-70% based on the total mass of the electrolyte. In this way, the dielectric constant of the electrolyte is increased, the viscosity of the electrolyte is reduced, and the migration rate of lithium ions is improved.

[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, methyl ethyl carbonate, or diethyl carbonate.

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

[0019] According to some embodiments of the present application, the electrolyte includes linear carboxylic acid ester, the mass percentage of the linear carboxylic acid ester is 5-15% based on the total mass of the electrolyte. In this way, the conductivity of the electrolyte is improved, and the kinetic performance of the battery cell is improved.

[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, or ethyl acetate. In this way, the conductivity of the electrolyte is improved, and the kinetic performance of the battery cell is improved.

[0021] According to some embodiments of the present application, the electrolyte further includes an additive, the additive includes at least one of a fluorine-containing additive or a phosphorus-containing additive. In this way, a stable CEI film is formed on the surface of the positive electrode, and the risk of continuous gas production caused by electrolyte decomposition due to high pressure during the formation stage is reduced.

[0022] According to some embodiments of the present application, the additive includes a fluorine-containing additive and a phosphorus-containing additive, and the mass percentage of the sum of the fluorine-containing additive and the phosphorus-containing additive is 0.05-1% based on the total mass of the electrolyte. In this way, a stable CEI film is formed on the surface of the positive electrode, and the risk of continuous gas production caused by electrolyte decomposition due to high pressure during the formation stage is reduced.

[0023] According to some embodiments of the present application, the mass percentage of the fluorine-containing additive is 0.05-0.5% and the mass percentage of the phosphorus-containing additive is 0.05-0.5% based on the total mass of the electrolyte. In this way, a stable CEI film is formed on the surface of the positive electrode, and the risk of continuous gas production caused by electrolyte decomposition due to high pressure during the formation stage is reduced.

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

[0025] According to some embodiments of the present application, the additive further comprises a carbonate additive, the carbonate additive comprising at least one of vinylene carbonate, propylene carbonate, 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 cell is improved.

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

[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 the mass fraction of the first carbon coating layer is 0.5%-1.5% based on the total mass of the lithium iron phosphate; and / or at least part of the surface of the lithium supplementing agent has a second carbon coating layer, and the mass fraction of the second carbon coating layer is 1%-5% based on the total mass of the lithium supplementing agent. Thus, carbon coating at least part of the surface of the lithium iron phosphate can improve the electronic conductivity of the electrode sheet; carbon coating at least part of the surface of the lithium supplementing agent can reduce the number of active sites exposed by the lithium supplementing agent and reduce the probability of reaction with the electrolyte.

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

[0029] According to some embodiments of the present application, the coating weight of the positive electrode film layer is 10 mg / cm 2 -25 mg / 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 -2.6 g / cm 3 .

[0031] Thus, by making the coating weight and the compaction density of the positive electrode film layer in the above range, the energy density of the battery cell is improved.

[0032] According to some embodiments of the present application, the coating weight of the negative electrode film layer is 5 mg / cm 2 -15 mg / 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 -1.7 g / cm 3 .

[0034] Thus, by making the coating weight and the compaction density of the negative electrode film layer in the above range, the energy density of the battery cell is improved.

[0035] According to some embodiments of the present application, the separator film comprises a base film, at least one side of the base film having a coating layer. Thus, the risk of the base film being oxidized due to high pressure during formation is reduced.

[0036] According to some embodiments of the present application, the thickness of the separator film is 7 μm-15 μm. Thus, the risk of the base film being oxidized due to high pressure during formation is reduced.

[0037] According to some embodiments of the present application, the injection coefficient of the battery cell is 3 g / Ah-3.8 g / Ah. Thus, the content of electrolyte in the battery cell is increased, and the kinetic performance of the battery cell is improved.

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

[0039] The third aspect of the present application provides a power utilization device comprising the battery cell provided in the first aspect of the present application or the battery device provided in the second aspect of the present application, the battery cell or the battery device being used to provide electric energy.

[0040] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0041] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description. The accompanying drawings are only for purposes of illustration and are not considered limitations on the present application. Moreover, like reference numerals designate similar parts throughout the several views in the drawings. In the drawings:

[0042] FIG. 1 is a schematic view of a battery cell according to an embodiment of the present application.

[0043] Fig. 2 is an exploded view of the battery cell of the embodiment of the application shown in Fig. 1.

[0044] Fig. 3 is a schematic view of the battery module of the embodiment of the application.

[0045] Fig. 4 is a schematic view of the battery pack of the embodiment of the application.

[0046] Fig. 5 is an exploded view of the battery pack of the embodiment of the application shown in Fig. 4.

[0047] Fig. 6 is a schematic view of the use of the battery device of the embodiment of the application as a power source for a power consuming device.

[0048] BRIEF DESCRIPTION OF DRAWINGS 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 case; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0049] The embodiments of the technical solutions of the application will be described in detail below. The following embodiments are only used to more clearly illustrate the technical solutions of the application, and therefore only serve as examples, and cannot limit the protection scope of the application.

[0050] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor does it necessarily refer to a particular alternative embodiment. It will be explicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0051] If not specifically stated, all embodiments and optional embodiments of the application can be combined with each other to form new technical solutions.

[0052] If not specifically stated, all technical features and optional technical features of the application can be combined with each other to form new technical solutions.

[0053] If not specifically stated, all steps of the application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can also comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0054] At present, from the development of market situation, the application of battery is more and more widely, which can be applied to the energy storage power supply system of hydropower, thermal power, wind power and solar power station, but the battery monomer in the related art cannot meet the demand of long life and high power at the same time.

[0055] The present application aims to develop a battery monomer with long life and high power. By setting lithium supplement in the positive electrode film layer, the lithium consumption caused by the formation of SEI film in the formation stage is compensated, and the cycle performance of the battery monomer is improved. However, the lithium supplement can easily produce high-valence transition metal oxides in the battery monomer, which has the risk of oxidizing the electrolyte. The addition of fluorine-containing organic lithium salt in the electrolyte can form a dense CEI film on the surface of high-valence transition metal oxides, reduce the risk of oxidizing the electrolyte, and improve the cycle performance of the battery monomer. On the other hand, the combination of organic and inorganic lithium salt can optimize the composition of SEI film on the surface of graphite, form a SEI film with low impedance and good toughness, which can not only improve the deintercalation rate of lithium ions in graphite, but also effectively improve the damage of SEI film caused by the expansion of graphite during charging, and improve the power performance of the battery monomer.

[0056] The battery monomer proposed in the present application can be used in power consumption equipment using battery monomer as power supply or various energy storage systems using battery monomer as energy storage element. The power consumption equipment can include but is not limited to mobile phones, tablets, notebook computers, electric toys, electric tools, electric cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric plane toys, etc., spacecraft can include airplanes, rockets, space shuttles and spacecraft, etc.

[0057] The first aspect of the present application proposes a battery monomer, which comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode film layer, the positive electrode film layer comprises a lithium iron phosphate material and a lithium supplement; a negative electrode sheet, the negative electrode sheet comprises a negative electrode film layer, the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises graphite; a separator film between the positive electrode sheet and the negative electrode sheet; and an electrolyte, the electrolyte comprises a lithium salt, the lithium salt comprises an organic lithium salt and an inorganic lithium salt, the organic lithium salt comprises at least one of fluorine-containing sulfuryl imide lithium, fluorine-containing oxalate borate lithium and fluorine-containing oxalate phosphorus lithium, the inorganic lithium salt comprises 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.

[0058] The battery cell provided 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 oxidation of electrolyte by high-valence transition metal oxide formed by the lithium supplement, 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-valence transition metal oxide, reduce the direct contact between the transition metal oxide and the electrolyte, reduce the risk of oxidation and decomposition of the electrolyte, and improve the cycle performance of the battery cell. The combination of the organic lithium salt and the inorganic lithium salt can also form a SEI film with low impedance and good toughness 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 content of the organic lithium salt is too high, which may cause corrosion of the positive electrode current collector and significantly increase 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 content of the organic lithium salt is too low, which cannot form a SEI film with low impedance and good toughness, and is not conducive to the long life and high power of the battery cell.

[0059] In the present application, the test method of the content of the organic lithium salt and the inorganic lithium salt is as follows: a certain amount of electrolyte in the battery cell is weighed, diluted to 100 mL with ultrapure water, and detected by ion chromatography automatic sampling. The test is carried out according to the standard JY / T 020-1996 or GB / T 6040-2002.

[0060] For example, the mass ratio of the inorganic lithium salt to the organic lithium salt is (6-2):1, which can be 6:1, 5:1, 4:1, 3.65:1, 3:1 or 2:1, or can be a range composed of any of the above values.

[0061] 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.

[0062]

Positive electrode sheet

[0063] The positive electrode sheet includes 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. The positive electrode film layer includes a lithium iron phosphate material and a lithium supplement.

[0064] In some embodiments, the positive electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0065] According to some embodiments of the present application, the lithium supplement agent comprises Li x M y O z , the M comprises at least one of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, Zn, 0

[0066] As an example, x can be 1, 2, 3, 4, 5, or the like, or can be a range composed of any of the above values.

[0067] As an example, y can be 1, 1.5, 2, 2.5, or 3, or the like, or can be a range composed of any of the above values.

[0068] As an example, z can be 2, 3, 4, 5, 6, 7, or 8, or the like, or can be a range composed of any of the above values.

[0069] According to some embodiments of the present application, the lithium supplement agent comprises at least one of Li2NiO2, Li5FeO4. Thus, the lithium supplement effect is improved.

[0070] According to some embodiments of the present application, when the lithium in the lithium supplement agent is completely or partially stripped, the lithium supplement agent comprises Li n NiO m and Li e FeO f , at least one of which, 0

[0071] As an example, m can be 0.5, 1, 1.5, or 2, or the like, or can be a range composed of any of the above values.

[0072] As an example, n can be 0, 0.5, 1, 1.5, or 2, or the like, or can be a range composed of any of the above values.

[0073] As an example, e can be 0, 1, 2, 3, 4, or 5, or the like, or can be a range composed of any of the above values.

[0074] As an example, f can be 1, 2, 3, or 4, or the like, or can be a range composed of any of the above values.

[0075] According to some embodiments of the present application, when the lithium in the lithium supplement agent is completely stripped, the lithium supplement agent comprises NiO m and Li p FeO q , at least one of which, 0

[0076] As an example, m can be 0.5, 1, 1.5, or 2, or can be a range consisting of any of the aforementioned values.

[0077] As an example, p can be 0, 0.2, 0.4, 0.6, 0.8, or 1, or can be a range consisting of any of the aforementioned values.

[0078] As an example, q can be 0.5, 1, 1.5, or 2, or can be a range consisting of any of the aforementioned values.

[0079] In this application, a method for detecting a lithium supplement agent is provided: after a battery monomer is discharged at 0.1C to 2.0V, it is disassembled, the positive electrode sheet is scraped, and the powder is tested by an X-ray diffractometer (XRD). At least one characteristic peak corresponding to the lithium supplement agent exists in the spectrum.

[0080] 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 the mass percentage of the first carbon coating layer can be 0.5%-1.5%, for example, can be 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, or 1.5%, or can be a range consisting of any of the aforementioned values, based on the total mass of the lithium iron phosphate. In this way, the electronic conduction capacity between lithium iron phosphate particles is improved, and the electronic conductivity of the electrode sheet is further improved.

[0081] 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, and the mass percentage of the second carbon coating layer can be 1%-5%, for example, can be 1%, 2%, 3%, 4%, or 5%, or can be a range consisting of any of the aforementioned values, based on the total mass of the lithium supplement agent. In this way, 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, quickly form pores on the electrode sheet, make the electrolyte quickly infiltrate the electrode sheet, improve the transmission efficiency of lithium ions, and improve the kinetic performance of the battery monomer. According to some specific embodiments of the present application, the mass percentage of the second carbon coating layer can be 1%-5%, based on the total mass of the lithium supplement agent. According to some specific embodiments of the present application, the mass percentage of the second carbon coating layer can be 2%-4%, based on the total mass of the lithium supplement agent.

[0082] According to some embodiments of the present application, the mass percentage of the lithium supplement agent can be 0.5%-5%, for example, can be 0.5%, 1%, 2%, 3%, 4%, or 5%, or can be a range consisting of any of the aforementioned values, based on the total mass of the positive electrode film layer. In this way, the lithium supplement effect is improved.

[0083] In some embodiments, the positive electrode film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0084] In some embodiments, the positive electrode film layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Further optionally, a combination of super conductive carbon and carbon nanotubes can be used, thereby improving the electronic conductivity of the positive electrode tab.

[0085] According to some embodiments of the present application, the coating weight of the positive electrode film layer can be 10 mg / cm 2 -25 mg / cm 2 , for example, 10 mg / cm 2 , 12 mg / cm 2 , 14 mg / cm 2 , 16 mg / cm 2 , 18.5 mg / cm 2 , 20 mg / cm 2 , 22 mg / cm 2 , 24 mg / cm 2 , or 25 mg / cm 2 , or a range consisting of any of the above values. In this way, the energy density of the battery cell is improved while the tortuosity of the positive electrode tab is reduced, the diffusion rate of lithium ions is improved, and the kinetic 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 -20 mg / cm 2 .

[0086] It should be noted that the coating weight of the positive electrode film layer referred to herein refers to the coating weight of the single-sided positive electrode film layer on the positive electrode tab.

[0087] According to some embodiments of the present application, the compaction density of the positive electrode film layer can be 2.2 g / cm 3 -2.6 g / cm 3 , for example, 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 , or 2.6 g / cm 3or can be a range composed of any of the above numerical values. Thus, while the energy density of the battery cell is improved, the tortuosity of the positive electrode sheet is reduced, the diffusion rate of lithium ions is improved, and the kinetic performance of the battery cell is improved. According to some embodiments of the present application, the compaction density of the positive electrode film layer is 2.3 g / cm 3 -2.5 g / cm 3 .

[0088] The present application provides a method for testing the coating weight of a positive electrode film layer: a positive electrode sheet is disassembled from a battery cell, for example, a single-sided coated positive electrode sheet (if a double-sided coated electrode sheet, the positive electrode film layer on one side can be wiped off first), punched into a small disc with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then the positive electrode film layer of the above weighed positive electrode sheet is wiped off, the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. 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.

[0089] In some embodiments, the positive electrode sheet can be prepared by: dispersing the above-mentioned components for preparing the positive electrode sheet, such as lithium iron phosphate material, lithium supplement, conductive agent, binder and any other components, in a solvent (such as N-methyl pyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0090]

Negative electrode sheet

[0091] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite.

[0092] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0093] According to some embodiments of the present application, the coating weight of the negative electrode film layer is 5 mg / cm 2 -15 mg / cm 2 , for example, can be 5 mg / cm 27 mg / cm 2 8.6 mg / cm 2 9 mg / cm 2 11 mg / cm 2 13 mg / cm 2 or 15 mg / cm 2 , or can be a range consisting of any of the aforementioned values. In this way, the energy density of the battery cell is improved. According to some embodiments of the present application, the coating weight of the negative electrode film layer can be 7 mg / cm 2 - 11 mg / cm 2 .

[0094] It should be noted that the coating weight of the negative electrode film layer referred to here refers to the coating weight of the single-sided negative electrode film layer on the negative electrode sheet.

[0095] According to some embodiments of the present application, the compaction density of the negative electrode film layer can be 1.2 g / cm 3 - 1.7 g / cm 3 , for example, can be 1.2 g / cm 3 , 1.32 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , or 1.7 g / cm 3 , or can be a range consisting of any of the aforementioned values.

[0096] 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.

[0097] According to some embodiments of the present application, the compaction density of the negative electrode film layer can be the compaction density of the negative electrode film layer in the negative electrode sheet corresponding to the battery cell under 100% SOC state.

[0098] According to some embodiments of the present application, the compaction density of the negative electrode film layer can be the compaction density of the negative electrode film layer in the negative electrode sheet corresponding to the battery cell under 0% SOC state.

[0099] According to some embodiments of the present application, the negative electrode film layer comprises graphite, and the volume average particle size Dv50 of the graphite is 8 μm-14 μm. In this way, the volume average particle size of the graphite is reduced, the rate of lithium ion intercalation and deintercalation between graphite layers is improved, the impedance of the battery cell is reduced, and the kinetic performance is improved.

[0100] For example, the volume average particle size Dv50 of the graphite can be 8 μm, 10 μm, 12 μm, or 14 μm, or can be a range consisting of any of the aforementioned values.

[0101] In the present application, Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50%, which is determined by using a laser particle size analyzer (Malvern Master Size 2000) according to the standard GB / T 19077-2016 / ISO 13320:2009.

[0102] According to some embodiments of the present application, the negative electrode film layer comprises 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. The OI value of the graphite is 2-5. Thus, by reducing the OI value of the graphite, the kinetic performance of the battery is improved.

[0103] For example, the OI value of the graphite can be 2, 3, 4, or 5, or can be a range consisting of any of the above values.

[0104] According to some embodiments of the present application, the graphite comprises artificial graphite. Thus, compared with natural graphite, the number of active sites on the surface of artificial graphite is less, which can improve the life of the battery cell.

[0105] In some embodiments, the negative electrode film layer can further optionally comprise a binder. The binder can 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).

[0106] In some embodiments, the negative electrode film layer can further optionally comprise a conductive agent. The conductive agent can be selected from at least one of super-conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Further, the super-conductive carbon and the carbon nanotubes can be used 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.

[0107] In some embodiments, the negative electrode film layer can further optionally comprise other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0108] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and then performing processes such as drying and cold pressing to obtain the negative electrode sheet.

[0109]

Electrolyte

[0110] Generally, the electrolyte comprises a solvent, a lithium salt, and an additive.

[0111] According to some embodiments of the present application, the total mass percentage of the lithium salt in the electrolyte can be 8-13%. For example, it can be 8%, 9%, 10%, 11%, 12% or 13%, or a range consisting of any of the aforementioned values. In this way, the ionic conductivity of the electrolyte is improved. According to some specific embodiments of the present application, the total mass percentage of the lithium salt can be 10-12%.

[0112] According to some embodiments of the present application, the inorganic lithium salt includes lithium hexafluorophosphate, and the mass percentage of the inorganic lithium salt based on the total mass of the electrolyte can be 7.5-12%, thereby improving the ionic conductivity of the electrolyte. By having the content of the inorganic lithium salt within the above range, a SEI film with low impedance and moderate hardness is formed on the surface of the negative electrode, effectively inhibiting the expansion of the electrode sheet during the cycle process caused by the expansion of graphite, and improving the cycle performance of the battery cell.

[0113] For example, the mass percentage of the inorganic lithium salt can be 7.5%, 8%, 9%, 10%, 11% or 12%, or a range consisting of any of the aforementioned values.

[0114] According to some embodiments of the present application, the organic lithium salt includes at least one of lithium bisfluorosulfonylimide (LIFSI) and lithium bis-trifluorosulfonylimide (LITFSI), and the mass percentage of the organic lithium salt based on the total mass of the electrolyte can be 1-4%. In this way, the impedance of the SEI film is reduced, the ionic conductivity of the SEI film is improved, the kinetic performance of the battery is improved, and the probability of the formation of aluminum fluoride between fluorine and the positive electrode current collector aluminum due to excessive content of the organic lithium salt is reduced, thereby reducing the risk of corrosion of the positive electrode current collector.

[0115] For example, the mass percentage of the organic lithium salt based on the total mass of the electrolyte can be 1%, 2%, 3% or 4%, or a range consisting of any of the aforementioned values.

[0116] According to some embodiments of the present application, the solvent includes a cyclic carbonate and a linear carbonate. In this way, the dielectric constant of the electrolyte is improved, the viscosity of the electrolyte is reduced, and the migration rate of lithium ions is improved.

[0117] According to some embodiments of the present application, the mass percentage of the cyclic carbonate based on the total mass of the electrolyte can be 15-25%, and the mass percentage of the linear carbonate based on the total mass of the electrolyte can be 50-70%. In this way, the dielectric constant of the electrolyte is improved, the viscosity of the electrolyte is reduced, and the migration rate of lithium ions is improved.

[0118] For example, the mass percentage of the cyclic carbonate based on the total mass of the electrolyte can be 15%, 17%, 19%, 21%, 23% or 25%, or a range consisting of any of the aforementioned values.

[0119] According to some embodiments of the present application, the mass percentage of the cyclic carbonate is 22-25% based on the total mass of the electrolyte.

[0120] For example, the mass percentage of the linear carbonate can be 50%, 55%, 60%, 65%, 70%, or the like, or a range formed by any of the above values.

[0121] According to some embodiments of the present application, the cyclic carbonate includes at least one of ethylene carbonate (EC) or propylene carbonate.

[0122] According to some embodiments of the present application, the linear carbonate includes at least one of dimethyl carbonate, methyl ethyl carbonate, or diethyl carbonate.

[0123] According to some embodiments of the present application, the linear carbonate includes dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC), the mass percentage of the dimethyl carbonate is 30-40% based on the total mass of the electrolyte, and the mass percentage of the methyl ethyl carbonate is 30-40%. In this way, the viscosity of the electrolyte is reduced.

[0124] For example, the mass percentage of the DMC can be 30%, 32%, 34%, 36%, 38%, 40%, or the like, or a range formed by any of the above values.

[0125] For example, the mass percentage of the EMC can be 30%, 32%, 34%, 36%, 38%, 40%, or the like, or a range formed by any of the above values.

[0126] According to some embodiments of the present application, the electrolyte can further include a linear carboxylic acid ester, and the mass percentage of the linear carboxylic acid ester is 5-15% based on the total mass of the electrolyte. In this way, the conductivity of the electrolyte is improved, and the kinetic performance of the battery cell is improved. In addition, the content of the linear carboxylic acid ester is controlled to be no more than 15%, and the high-temperature stability of the electrolyte is improved.

[0127] For example, the mass percentage of the linear carboxylic acid ester can be 5%, 7%, 9%, 11%, 13%, 15%, or the like, or a range formed by any of the above values.

[0128] According to some embodiments of the present application, the linear carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate, or ethyl acetate. In this way, the conductivity of the electrolyte is improved, and the kinetic performance of the battery cell is improved.

[0129] According to some embodiments of the present application, the decomposition voltage of the lithium supplement agent is high, and in order to improve the high-voltage resistance of the electrolyte, the electrolyte further comprises an additive, and the additive comprises at least one of a fluorine-containing additive or a phosphorus-containing additive. In this way, the above-mentioned kinds of additives can be preferentially decomposed from the solvent, and after decomposition, a stable CEI film can be formed, reducing the risk of transition metal dissolution in the positive material under high-voltage formation conditions, reducing the risk of electrolyte oxidative decomposition, improving the cycle stability of the electrolyte, and improving the cycle performance of the battery cell.

[0130] According to some embodiments of the present application, the additive comprises a fluorine-containing additive and a phosphorus-containing additive, and the mass ratio of the sum of the fluorine-containing additive and the phosphorus-containing additive to the total mass of the electrolyte is 0.05%-1%. In this way, by setting the sum of the mass of the fluorine-containing additive and the phosphorus-containing additive in the above range, the stability of the CEI film is improved, the risk of electrolyte oxidative decomposition during the formation stage is reduced, the cycle stability of the electrolyte is improved, and the cycle performance of the battery cell is improved.

[0131] In the present application, the type and content of the electrolyte additive can be tested according to GB / T 9722-2006 Chemical Reagents Gas Chromatography. Specifically, a certain amount of electrolyte is tested using a gas chromatograph, and the separation of each component of the electrolyte is achieved by using the different adsorption and desorption capacities of each component of the electrolyte in the chromatographic column. The separated sample is tested using a gas chromatograph-mass spectrometer (GC-MS).

[0132] For example, the mass ratio of the sum of the fluorine-containing additive and the phosphorus-containing additive can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, or can be a range composed of any of the above values.

[0133] According to some specific embodiments of the present application, the mass ratio of the fluorine-containing additive is 0.05%-0.5%, and the mass ratio of the phosphorus-containing additive is 0.05%-0.5%, based on the total mass of the electrolyte. In this way, the stability of the CEI film is improved, the risk of high-voltage oxidative electrolyte during the formation stage is reduced, the cycle stability of the electrolyte is improved, and the cycle performance of the battery cell is improved.

[0134] For example, the mass ratio of the fluorine-containing additive can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, etc., or can be a range composed of any of the above values.

[0135] For example, the mass ratio of the phosphorus-containing additive can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, etc., or can be a range composed of any of the above values.

[0136] According to some embodiments of the present application, the fluorine-containing additive includes at least one of fluoroethylene carbonate (FEC), bis-fluoroethylene carbonate (DFEC), and perfluoroalkyl carbonate.

[0137] 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-oxo-1,3,2-dioxaphospholane (TFEOP).

[0138] According to some embodiments of the present application, the additive further includes a carbonate additive, which includes at least one of vinylene carbonate (VC), propylene carbonate, and vinyl ethylene carbonate. In this way, by adding the carbonate additive to the electrolyte, a SEI film containing a polymer can be formed on the surface of the negative electrode, the stability of the SEI film is improved, and the life of the battery cell is improved.

[0139] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate, and the mass fraction of the vinylene carbonate based on the total mass of the electrolyte can be 0.5%-3%. In this way, by adding the carbonate additive to the electrolyte, a SEI film containing a polymer can be formed on the surface of the negative electrode, the stability of the SEI film is improved, and the life of the battery cell is improved.

[0140] For example, the mass fraction of the vinylene carbonate based on the total mass of the electrolyte can be 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%, or can be a range consisting of any of the above values. According to some specific embodiments of the present application, the mass fraction of the vinylene carbonate can be 1%-2%.

[0141] 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, or can be a range consisting of any of the above values. In this way, the kinetic performance and cycle life of the battery are improved.

[0142] [Separator]

[0143] In some embodiments, a separator is further included in the battery cell. The present application does not have a particular limitation on the type of the separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0144] According to some embodiments of the present application, the separator film comprises a base film having a coating layer on at least one side of the base film. The material of the base film comprises at least one of polyethylene or polypropylene. In this way, the risk of oxidation of the separator film under high pressure conditions is reduced.

[0145] According to some embodiments of the present application, the coating layer can be a ceramic coating layer.

[0146] According to some embodiments of the present application, the thickness of the separator film can be 7-15 μm. For example, it can be 7 μm, 9 μm, 11 μm, 13 μm or 15 μm, or it can be a range consisting of any of the above values.

[0147] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator film can be used to form an electrode assembly by a winding process or a stacking process.

[0148] In some embodiments, the battery cell can comprise an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte as described above.

[0149] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate and polybutylene succinate, etc. can be listed.

[0150] The shape of the battery cell is not particularly limited in the present application, and it can be cylindrical, square or any other shape. For example, FIG. 1 is a battery cell 5 of a square structure as an example.

[0151] In some embodiments, referring to FIG. 2, the outer package can comprise a shell 51 and a cover plate 53. The shell 51 can comprise 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 communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator film can be used to form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0152] The second aspect of the present application provides a battery device comprising the battery cell provided by the first aspect of the present application, and the battery device is at least one of a battery module, a battery pack and an energy storage device.

[0153] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0154] FIG. 3 is a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0155] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0156] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0157] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to 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.

[0158] In addition, the present application also provides a power consuming device, which includes at least one of the battery cell, the battery module, or the battery pack provided by the present application. The battery cell, the battery module, or the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0159] As the power consuming device, the battery cell, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0160] FIG. 6 is a power consuming device as an example. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the power consuming device for the battery, a battery pack or a battery module can be used.

[0161] As another example, the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device generally requires thinning, and a battery monomer can be used as a power source.

[0162] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, further detailed description will be made in combination with embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all. The description of at least one exemplary embodiment below is actually only illustrative, but not as any limitation on the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0163] Embodiment 1

[0164] 1. Positive electrode tab

[0165] The positive electrode tab includes a positive electrode current collector aluminum foil, and the aluminum foil has a positive electrode film layer on both surfaces, the compaction density is 2.39 g / cm 3 , the coating weight of the single-sided positive electrode film layer 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 lithium phosphate material, lithium supplement Li2NiO2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) with mass ratios of 94.5%, 2.5%, 0.8%, and 2.2% respectively, the lithium phosphate surface has a first carbon coating layer, and the mass ratio of the first carbon coating layer based on the total mass of the lithium phosphate is 1.5%.

[0166] 2. Negative electrode tab

[0167] The negative electrode tab includes a negative electrode current collector copper foil, and the copper foil has a negative electrode film layer on both surfaces, the compaction density is 1.32 g / cm 3 , the coating weight of the single-sided negative electrode film layer is 8.6 mg / cm 2 , based on the total mass of the single-sided negative electrode film layer, the negative electrode film layer includes artificial graphite (OI value is 3.63), conductive agent carbon black, binder styrene butadiene rubber (SBR), and thickening agent carboxymethyl cellulose sodium (CMC-Na) with mass ratios of 96.6%, 0.4%, 1.8%, and 1.2% respectively.

[0168] 3. Electrolyte

[0169] The electrolyte comprises a solvent, an electrolyte salt and an additive, the solvent comprises EC, DMC and EMC, the mass ratio of EC, DMC and EMC is 24:38:38, the additive comprises TMSP, FEC and VC, the mass percentage of TMSP is 0.23% based on the total mass of the electrolyte, the mass percentage of FEC is 0.12% based on the total mass of the electrolyte, and the mass percentage of VC is 1.39% based on the total mass of the electrolyte; the electrolyte salt is LiPF6 and LIFSI, the mass percentage of LiPF6 is 9.383% based on the total mass of the electrolyte, and the mass percentage of LIFSI is 2.57% based on the total mass of the electrolyte.

[0170] 4. Separated film

[0171] The polypropylene film has a thickness of 12 μm.

[0172] 5. Battery cell

[0173] The battery cell comprises a positive electrode sheet, a separated film, a negative electrode sheet and an electrolyte.

[0174] Performance test

[0175] 1. DCR test

[0176] At 25°C, the battery cell is charged at 1 / 3C constant current to 3.65V, then charged at 3.65V constant voltage to a current of 0.05C, and after 5min of standing, discharged at 1 / 3C constant current for 90min, and after 120min of standing, the voltage V1 is recorded. Then discharged at 4C for 30s, the voltage V2 is recorded, and (V2-V1) / 4C is obtained, thereby obtaining the internal resistance DCR of the battery cell.

[0177] 2. 1000 cycle capacity retention rate

[0178] At 25°C, the corresponding battery cell is charged at 1 / 3C constant current to 3.65V, then charged at 3.65V constant voltage to a current of 0.05C, and after 5min of standing, discharged at 1 / 3C to 2.5V, and the obtained capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery cell, and the discharge capacity Cn of the battery cell after the n-th cycle is recorded. n , then the capacity retention rate P of the battery cell after each cycle n = Cn / C0x 100%. In the test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and the 1000th cycle corresponds to n=1000. n

[0179] 3. 60°C storage for 150 days capacity retention rate

[0180] ​The corresponding battery monomer was charged at 1 / 3C to 3.65V at 25℃, and then charged at 3.65V to 0.05C, and then left for 5min, and then discharged at 1 / 3C to 2.5V, and the capacity obtained was recorded as the initial capacity CO. After charging at 1 / 3C to 3.65V and then constant voltage to 0.05C, the battery monomer was taken out after being placed in a constant temperature oven at 60℃ for 150 days, and discharged at 1 / 3C to 2.5V at room temperature. The battery monomer after taking out was charged at 1 / 3C to 3.65V at 25℃, and then charged at 3.65V to 0.05C, and then left for 5min, and then discharged at 1 / 3C to 2.5V, and the capacity C was recorded n , and the capacity retention rate was (C n / C0) x 100%.

[0181] Example 2, Example 3, Comparative Example 2, Comparative Example 3

[0182] The positive electrode sheet, the negative electrode sheet, the electrolyte solvent and the additive in the battery monomer were the same as in Example 1, and the difference was that the mass ratio of LiPF6 and LIFSI was different, and the mass ratio of inorganic lithium salt and organic lithium salt was different.

[0183] Example 4

[0184] The positive electrode sheet, the negative electrode sheet, the electrolyte solvent and the additive in the battery monomer were the same as in Example 1, and the difference was that the organic lithium salt was LITFSI.

[0185] Comparative Example 1

[0186] The negative electrode sheet and the electrolyte in the battery monomer were the same as in Example 1, and the difference was that the positive electrode film layer did not contain a lithium supplement agent.

[0187] The differences in Example 1-Example 4 and Comparative Example 1-Comparative Example 3 are shown in Table 1:

[0188] Table 1

[0189] As can be seen from Example 1-Example 3 and Comparative Example 1-Comparative Example 3, the battery monomer proposed in the application has a lower internal resistance, a higher cycle capacity retention rate and a high temperature capacity retention rate. It is shown that by adding a lithium supplement agent to the positive electrode film layer, the high temperature cycle performance of the battery monomer can be improved; 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 agent and the electrolyte can be reduced, and the cycle performance of the battery can be improved. At the same time, the SEI impedance formed by the combination of the organic lithium salt and the inorganic lithium salt is low, which can improve the deintercalation rate of lithium ions in graphite and improve the power performance of the battery monomer.

[0190] As can be seen from Example 4 and Example 1, different kinds of organic lithium salts have the effect of improving the cycle performance and power performance of the battery monomer.

[0191] Example 5, Example 6

[0192] The positive electrode sheet, the negative electrode sheet, the electrolyte solvent and the additive in the battery monomer are the same as in Example 1, except that the content of TMSP is different.

[0193] Example 7, Example 8

[0194] The positive electrode sheet, the negative electrode sheet, the electrolyte solvent and the additive in the battery monomer are the same as in Example 1, except that the content of FEC is different.

[0195] The differences in Example 5-Example 8 are shown in Table 2.

[0196] Table 2

[0197] As can be seen from Example 1, Example 5-Example 8, by controlling the content of the phosphorus-containing additive and the fluorine-containing additive in the electrolyte, the internal resistance and the cycle capacity retention rate and the high-temperature capacity retention rate of the battery monomer can be adjusted, and then a battery monomer with long service life and low internal resistance is obtained.

[0198] Example 9, Example 10

[0199] The positive electrode sheet, the negative electrode sheet, the electrolyte salt and the additive in the battery monomer are the same as in Example 1, except that the electrolyte solvent further includes methyl acetate (MA), and the content of MA is different, as shown in Table 3.

[0200] Table 3

[0201] As can be seen from Example 1, Example 9 and Example 10, by adding different contents of MA in the electrolyte, the internal resistance of the battery monomer can be further reduced, thereby improving the kinetic performance of the battery monomer.

[0202] Example 11

[0203] The negative electrode sheet and the electrolyte in the battery monomer are the same as in Example 1, except that the type of lithium supplementing agent is different.

[0204] Example 12, Example 13

[0205] The negative electrode sheet and the electrolyte in the battery monomer are the same as in Example 1, except that the compaction density of the positive electrode film layer is different.

[0206] The type of lithium supplementing agent in Example 11 and the compaction density of the positive electrode film layer in Example 12 and Example 13 are shown in Table 4.

[0207] Table 4

[0208] As can be seen from Example 1 and Example 11, different kinds of lithium supplementing agents can all improve the cycle performance of the battery.

[0209] As can be seen from Example 1, Example 12 and Example 13, the positive electrode film layers with different compaction densities can all obtain battery monomers with both long life and low internal resistance.

[0210] Example 14 and Example 15

[0211] The battery monomers are the same as Example 1 in the positive electrode sheet and the electrolyte, except that the OI value of the negative electrode graphite is different.

[0212] Example 16 and Example 17

[0213] The battery monomers are the same as Example 1 in the positive electrode sheet and the electrolyte, except that the volume average particle size of the negative electrode graphite is different.

[0214] Example 18 and Example 19

[0215] The battery monomers are the same as Example 1 in the positive electrode sheet and the electrolyte, except that the compaction density of the negative electrode film layer is different.

[0216] The differences of the negative electrode sheets in Example 14-Example 19 are shown in Table 5.

[0217] Table 5

[0218] As can be seen from Example 1, Example 14 and Example 15, by reducing the OI value of the graphite, the internal resistance of the battery monomer can be reduced, and at the same time, the battery monomer has excellent cycle performance.

[0219] As can be seen from Example 1, Example 16 and Example 17, by reducing the volume average particle size of the graphite, the internal resistance of the battery monomer can be reduced, and at the same time, the battery monomer has excellent cycle performance.

[0220] As can be seen from Example 1, Example 18 and Example 19, the negative electrode film layers with different compaction densities can all obtain battery monomers with both long life and low internal resistance.

[0221] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising: a positive electrode tab including a positive electrode film layer, the positive electrode film layer including a lithium iron phosphate material and a lithium supplement agent; a negative electrode tab including a negative electrode film layer, the negative electrode film layer including a negative electrode active material, the negative electrode active material including graphite; a separator film between the positive electrode tab and the negative electrode tab; and an electrolyte including a lithium salt, the lithium salt including an organic lithium salt and an inorganic lithium salt, the organic lithium salt including at least one of lithium fluorosulfonylimide, lithium fluorinated oxalate borate, lithium fluorinated oxalate phosphate, the inorganic lithium salt including at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium fluorosulfonate, a mass ratio of the inorganic lithium salt and the organic lithium salt being (6-2) :

1. The organic lithium salt includes at least one of lithium bisfluorosulfonylimide, lithium bis-trifluorosulfonylimide, a mass percentage of the organic lithium salt based on a total mass of the electrolyte being 1% to 4%. The inorganic lithium salt includes lithium hexafluorophosphate, a mass percentage of the inorganic lithium salt based on a total mass of the electrolyte being 7.5% to 12%. An OI value of the graphite being 2 to 5. A volume average particle size Dv50 of the graphite being 8 μm to 14 μm.

2. The battery cell of claim 1, wherein, The graphite including artificial graphite.

3. The battery cell of claim 1 or 2, wherein, The lithium supplement agent including at least one of Li 2 NiO 2, Li 5 FeO 4.

4. The battery cell of any one of claims 1-3, wherein, The electrolyte further including a solvent, the solvent including a cyclic carbonate and a linear carbonate.

5. The battery cell of any one of claims 1-4, wherein, A mass percentage of the cyclic carbonate based on a total mass of the electrolyte being 15% to 25%, a mass percentage of the linear carbonate based on a total mass of the electrolyte being 50% to 70%.

6. The battery cell of any one of claims 1-5, wherein, The cyclic carbonate including at least one of ethylene carbonate or propylene carbonate; and / or 7. The battery cell of any one of claims 1-6, wherein, The lithium supplement agent comprises Li x M y O z , the M comprises at least one of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, Zn, 0 < x ≤ 5, 1 ≤ y ≤ 3, 2 ≤ z ≤ 8.

8. The battery cell of any one of claims 1-6, wherein, The linear carbonate including at least one of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate.

9. The battery cell of any one of claims 1-6, wherein, The lithium supplement agent comprises Li n NiO m 、Li e FeO f at least one of, wherein 0 10. The battery cell of any one of claims 1-6, wherein, The lithium supplement agent comprises NiO m and Li p FeO q at least one of, wherein 0 < m ≤ 2, 0 ≤ p ≤ 1, 0 < q ≤ 2.

11. The battery cell of any one of claims 1-10, wherein, The linear carbonate including dimethyl carbonate and methyl ethyl carbonate, a mass percentage of the dimethyl carbonate based on a total mass of the electrolyte being 30% to 40%, a mass percentage of the methyl ethyl carbonate based on a total mass of the electrolyte being 30% to 40%.

12. The battery cell of claim 11, wherein, The electrolyte including a linear carboxylic acid ester, a mass percentage of the linear carboxylic acid ester based on a total mass of the electrolyte being 5% to 15%.

13. The battery cell of claim 11 or 12, wherein, The linear carboxylic acid ester including at least one of methyl formate, methyl acetate, ethyl formate, ethyl acetate. The electrolyte further including an additive, the additive including at least one of a fluorine-containing additive or a phosphorus-containing additive.

14. The battery cell of any one of claims 11-13, wherein, The additive including the fluorine-containing additive and the phosphorus-containing additive, a mass percentage of a sum of the fluorine-containing additive and the phosphorus-containing additive based on a total mass of the electrolyte being 0.05% to 1%.

15. The battery cell of any one of claims 11-14, wherein, A mass percentage of the fluorine-containing additive based on a total mass of the electrolyte being 0.05% to 0.5%, a mass percentage of the phosphorus-containing additive based on a total mass of the electrolyte being 0.05% to 0.5%.

16. The battery cell of claim 15, wherein, The fluorine-containing additive including at least one of fluoroethylene carbonate, bis-fluoroethylene carbonate, perfluoroalkyl-substituted ethylene carbonate; and / or 17. The battery cell of any one of claims 1-16, wherein, ​ 18. The battery cell of claim 17, wherein, ​ 19. The battery cell of claim 17 or 18, wherein, ​ 20. The battery cell of any one of claims 17-19, wherein, ​ 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, 2-trifluoroethoxy-2-oxo-1,3,2-dioxaphospholane.

21. The battery cell of any one of claims 17-20, wherein, The additive further includes a carbonate-based additive, and the carbonate-based additive includes at least one of vinylene carbonate, propylene carbonate, and vinyl ethylene carbonate.

22. The battery cell of claim 21, wherein, The carbonate-based additive includes vinylene carbonate, and a mass percentage of the vinylene carbonate is 0.5%-3% based on a total mass of the electrolyte.

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

24. The battery cell of any one of claims 1-23, wherein, A mass percentage of the lithium supplement agent is 0.5%-5% based on a total mass of the positive electrode film layer.

25. The battery cell of any one of claims 1-24, wherein, The coating weight of the positive electrode film layer is 10 mg / cm 2 - 25 mg / cm 2 .

26. The battery cell of any one of claims 1-25, wherein, The compacted density of the positive electrode film layer is 2.2 g / cm 3 - 2.6 g / cm 3 .

27. The battery cell of any one of claims 1-26, wherein, The coating weight of the negative electrode film layer is 5 mg / cm 2 - 15 mg / cm 2 .

28. The battery cell of any one of claims 1-27, wherein, The compaction density of the negative electrode film layer is 1.2 g / cm 3 -1.7 g / cm 3 .

29. The battery cell of any one of claims 1-28, wherein, The separator film includes a base film, and at least one side of the base film has a coating layer.

30. The battery cell of any one of claims 1-29, wherein, A thickness of the separator film is 7-15 microns.

31. The battery cell of any one of claims 1-30, wherein, An injection coefficient of the battery cell is 3-3.8 g / Ah.

32. A battery device, wherein, The battery device includes at least one of a battery module, a battery pack, and an energy storage device.

33. An electrical device, comprising: The battery cell or the battery device is used to provide electric energy.

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