Battery cell, battery device, electric device

Abstract

The application discloses a battery monomer, a battery device and a power consumption equipment. The battery monomer comprises an electrode assembly and an electrolyte. The electrode assembly comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, and the positive electrode active material layer comprises a lithium-containing phosphate. The electrolyte comprises a carboxylic acid ester solvent and a linear carbonate solvent. The mass percentage of the carboxylic acid ester solvent is 5% to 25% based on the total mass of the electrolyte, and the mass percentage of the linear carbonate solvent is 20% to 49% based on the total mass of the electrolyte. The electrolyte further comprises a non-lithium salt additive. The non-lithium salt additive comprises a phosphate ester additive. The non-lithium salt additive further comprises at least one of a carbonate additive, a sulfate additive, a borate additive, a silane additive and a sulfonic acid lactone additive. The total mass percentage of the non-lithium salt additive is 0.1% to 5% based on the total mass of the electrolyte.

Description

[0001] This application claims priority to PCT international application No. PCT / CN2025 / 092194 filed on April 29, 2025, entitled “Battery Cell, Battery Device, and Electrical Equipment,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of batteries, and in particular, to battery cells, battery devices, and electrical equipment. Background Art

[0003] Currently, market developments indicate that batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also growing. However, the cycle life of current battery cells under fast-charging conditions cannot meet these demands. Summary of the Invention

[0004] The present application provides a battery cell, comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising a lithium-containing phosphate;

[0005] The electrolyte includes a carboxylate solvent and a linear carbonate solvent, and the carboxylate solvent includes a compound represented by Formula I:

[0006] Formula I,

[0007] Wherein, R1 includes any one of a C1-C5 alkyl group and a C1-C5 haloalkyl group, and R2 includes any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group and a C1-C5 haloalkyl group;

[0008] The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate;

[0009] Based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent is 10%-25%, and the mass proportion of the linear carbonate solvent is 20%-49%;

[0010] The electrolyte further includes a non-lithium salt additive, wherein the non-lithium salt additive includes a phosphate additive, and the non-lithium salt additive further includes at least one of a carbonate additive, a sulfate additive, a borate additive, a silane additive, and a sultone additive. Based on the total mass of the electrolyte, the total mass of the non-lithium salt additive accounts for 0.1%-5%.

[0011] The battery cell provided in the present application can improve the fast charging performance of the battery cell while improving the cycle life of the battery cell by adapting appropriate amounts of carboxylate solvents, linear carbonate solvents and non-lithium salt additives in the electrolyte, thereby achieving a balance between fast charging performance and cycle life.

[0012] According to some embodiments of the present application, the non-lithium salt additives include carbonate additives and phosphate additives, with the combined mass percentage of the carbonate additives and the phosphate additives being 1.2%-5% based on the total mass of the electrolyte. This forms a stable SEI film, reduces side reactions caused by solvent molecules and interface contact, and improves the cycle life of the battery cells.

[0013] According to some embodiments of the present application, the non-lithium salt additives include carbonate additives and phosphate additives, and the combined mass percentage of the carbonate additives and the phosphate additives is 0.1%-0.5% based on the total mass of the electrolyte. This forms a stable SEI film, reduces side reactions caused by solvent molecules and interface contact, and improves the cycle life of the battery cells.

[0014] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate, and the phosphate additive includes tris(trimethylsilyl)phosphate. The combined mass percentage of vinylene carbonate and tris(trimethylsilyl)phosphate, based on the total mass of the electrolyte, is 0.1%-0.5%. This allows for the formation of a SEI film of moderate thickness on the material surface, maintaining interfacial stability while minimizing increases in internal resistance.

[0015] According to some embodiments of the present application, the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate. This reduces the viscosity of the electrolyte and increases the migration rate of lithium ions.

[0016] According to some embodiments of the present application, the electrolyte further includes a cyclic carbonate solvent, including one or more of ethylene carbonate, propylene carbonate, and butylene carbonate. This allows for the formation of a stable SEI film on the negative electrode surface, improving the electrolyte's ionic conductivity and, consequently, the battery's cycling performance and fast-charging performance.

[0017] According to some embodiments of the present application, the cyclic carbonate solvent accounts for 20%-40% of the total mass of the electrolyte. This allows for the formation of a stable SEI film on the negative electrode surface, improving the ionic conductivity of the electrolyte and, in turn, the cycling performance and fast-charging performance of the battery cell.

[0018] According to some embodiments of the present application, the electrolyte further includes a lithium salt additive, wherein the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bisoxalatoborate, and lithium fluorosulfonate. This forms a stable SEI film on the negative electrode surface, reducing side reactions between the electrolyte and the electrode surface.

[0019] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the weight of the lithium salt additive accounts for 0.1% to 4% of the total weight of the electrolyte, thereby improving the SEI impedance and enhancing power performance.

[0020] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the weight of the lithium salt additive accounts for 0.1%-0.5% of the total weight of the electrolyte. This improves the SEI impedance and enhances power performance.

[0021] According to some embodiments of the present application, the electrolyte further comprises an electrolyte salt comprising a lithium fluorinated sulfonyl imide and lithium hexafluorophosphate, with the electrolyte salt comprising 12% to 18% of the total mass of the electrolyte. This improves the ionic conductivity of the electrolyte while reducing HF generation and SEI film corrosion.

[0022] According to some embodiments of the present application, the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):1.

[0023] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass of the lithium hexafluorophosphate accounts for 4%-14%.

[0024] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorinated lithium sulfonyl imide is 4%-8%.

[0025] By setting the contents of lithium hexafluorophosphate and lithium fluorinated sulfonyl imide within the above ranges, the ionic conductivity of the electrolyte is improved while the generation of HF is reduced, thereby reducing the corrosion of the SEI film.

[0026] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature is 10 mS / cm-13.5 mS / cm, thereby increasing the migration rate of lithium ions and improving the fast charging performance of the battery cell.

[0027] According to some embodiments of the present application, the porosity of the positive electrode sheet is 25%-30%, thereby increasing the content of positive electrode active material and improving the transmission rate of lithium ions.

[0028] According to some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.3 g / cm 3 -2.6g / cm 3 This increases the energy density of the battery cell.

[0029] According to some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.45 g / cm 3 -2.58g / cm 3 This increases the energy density of the battery cell.

[0030] According to some embodiments of the present application, the coating weight of the positive electrode active material layer on one side is 0.27 g / 1540.25 mm 2 -0.33g / 1540.25mm 2 This increases the energy density of the battery cell.

[0031] According to some embodiments of the present application, the coating weight of the positive electrode active material layer on one side is 0.28 g / 1540.25 mm 2 -0.32g / 1540.25mm 2 This increases the energy density of the battery cell.

[0032] According to some embodiments of the present application, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate, thereby improving the cycle performance of the battery cell.

[0033] According to some embodiments of the present application, the lithium-containing phosphate includes lithium iron phosphate, and the average particle size of the lithium iron phosphate primary particles is 300 nm to 800 nm, thereby shortening the lithium ion deintercalation path and increasing the lithium ion deintercalation rate.

[0034] According to some embodiments of the present application, the lithium-containing phosphate includes a doping element, wherein the doping element includes one or more of V, Ti, Mg, and Nb. Doping the lithium iron phosphate with these elements can reduce iron dissolution, increase the rate of lithium ion insertion and extraction, improve battery power performance, and enhance the compaction density of the positive electrode active material layer.

[0035] According to some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass proportion of the V element is 0.02%-0.2%, the mass proportion of the Ti element is 0.03%-0.2%, the mass proportion of the Nb element is 0.02%-0.2%, and the mass proportion of the Mg element is 0.02%-0.1%. This reduces iron dissolution, increases the rate of lithium ion insertion and extraction, improves the power performance of the battery, and can also improve the compaction density of the positive electrode active material layer.

[0036] According to some embodiments of the present application, the electrode assembly further includes a negative electrode sheet having a porosity of 25%-30%, thereby increasing the content of the negative electrode active material and improving the lithium ion transmission rate.

[0037] According to some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes a carbon-based material, thereby improving the cycle performance of the battery cell.

[0038] According to some embodiments of the present application, the carbon-based material includes graphite, thereby improving the cycle performance of the battery cell.

[0039] According to some embodiments of the present application, the graphite includes secondary particles, at least part of the surface of which has amorphous carbon. This improves the electronic and ion conductivity of the graphite, thereby helping to improve the fast charging performance of the battery cell.

[0040] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 7 μm-12 μm, thereby shortening the solid phase migration path of lithium ions and improving the fast charging capability of the battery cell.

[0041] According to some embodiments of the present application, the graphite has a degree of graphitization of 90%-94%, thereby improving the ion conductivity and electron conductivity of the graphite and enhancing the rate performance of the battery.

[0042] According to some embodiments of the present application, the compaction density of the negative electrode active material layer is 1.3 g / cm 3 -1.52g / cm 3 This increases the energy density of the battery cell.

[0043] According to some embodiments of the present application, the coating weight of the negative electrode active material layer on one side is 0.12 g / 1540.25 mm 2 -0.15g / 1540.25mm 2 This increases the energy density of the battery cell.

[0044] According to some embodiments of the present application, the coating weight of the negative electrode active material layer on one side is 0.125 g / 1540.25 mm 2 -0.14g / 1540.25mm 2 This increases the energy density of the battery cell.

[0045] According to some embodiments of the present application, each layer of the positive electrode sheets is provided with a positive electrode tab, and each layer of the negative electrode sheets is provided with a negative electrode tab, thereby improving current transmission efficiency, reducing the resistance of the battery cells, and improving the rate performance of the battery.

[0046] According to some embodiments of the present application, the size of the battery cell along the width direction of the battery cell is 120mm-350mm, the size of the battery cell along the height direction of the battery cell is 80mm-120mm, and the size of the battery cell along the thickness direction of the battery cell is 25mm-80mm.

[0047] 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.

[0048] The third aspect of the present application provides an electrical device, comprising 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 provides electrical energy for the electrical device.

[0049] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0051] Figure 1 Schematic diagram of a battery cell according to one embodiment of the present application.

[0052] Figure 2 Schematic diagram of an electrical device using a battery as a power source according to one embodiment of the present application.

[0053] Description of reference numerals:

[0054] 1 battery cell. DETAILED DESCRIPTION

[0055] The following embodiments of the technical solution of the present application are described in detail. 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 are not intended to limit the scope of protection of the present application.

[0056] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0057] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0058] 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.

[0059] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating 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), indicating 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.

[0060] Currently, market developments indicate that batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also growing. However, the cycle life of battery cells in related technologies cannot meet these requirements under fast-charging conditions.

[0061] Compared with ternary battery cells, lithium iron phosphate battery cells are widely used because of their lower cost and better cycle performance. However, fast charging has a negative impact on the long-term cycle life of battery cells. Therefore, the fast charging capability and cycle capacity of lithium iron phosphate battery cells need to be comprehensively improved. In order to improve the fast charging performance of battery cells, solvents with lower viscosity and higher conductivity are added to the battery cells to increase the transmission rate of lithium ions and improve the fast charging performance of battery cells. However, if the content of carboxylic acid ester solvents is too high, the reaction activity of the electrolyte system will increase, the side reactions will be aggravated during the cycle, and the gas production will be large, which is also not conducive to long-term cycle performance. The present application controls the content of carboxylic acid ester solvents and linear carbonate solvents within a suitable range, and at the same time adapts film-forming additives that can improve the cycle stability of battery cells. It can improve the fast charging performance of battery cells while increasing the cycle life of battery cells. At the same time, by controlling the content of additives that can improve the cycle life within a suitable range, the film-forming impedance can be further reduced. The battery cells use lithium-containing phosphate as the positive electrode active material to further improve the cycle performance of the battery cells.

[0062] The battery cells proposed in this application can be used in electrical devices that use the battery cells as power sources or various energy storage systems that use the battery cells as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power 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. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0063] In a first aspect, the present application provides a battery cell, comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a lithium-containing phosphate;

[0064] The electrolyte includes a carboxylate solvent and a linear carbonate solvent, and the carboxylate solvent includes a compound represented by Formula I:

[0065] Formula I,

[0066] Wherein, R1 includes any one of a C1-C5 alkyl group and a C1-C5 haloalkyl group, and R2 includes any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group and a C1-C5 haloalkyl group;

[0067] The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate;

[0068] Based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent is 10%-25%, and the mass proportion of the linear carbonate solvent is 20%-49%;

[0069] The electrolyte further includes a non-lithium salt additive, wherein the non-lithium salt additive includes at least one of a carbonate additive, a sulfate additive, a borate additive, a phosphate additive, a silane additive, and a sultone additive. Based on the total mass of the electrolyte, the total mass of the non-lithium salt additive accounts for 0.1%-5%.

[0070] The battery cell provided in the present application can improve the fast charging performance of the battery cell while improving the cycle life of the battery cell by adapting appropriate amounts of carboxylate solvents, linear carbonate solvents and non-lithium salt additives in the electrolyte, thereby achieving a balance between fast charging performance and cycle life.

[0071] In this application, non-lithium salt additives refer to salt compounds that cannot dissociate into lithium ions in a solvent; carbonate additives refer to compounds containing a carbonate structure (RO−CO−OR′, where R and R′ are organic groups) in their molecular structure; sulfate additives refer to compounds containing a sulfate structure (−OSO3R, where R is an organic group) in their molecular structure; borate additives refer to compounds containing a borate structure (B(OR)3, where R is an organic group) in their molecular structure; phosphate additives refer to compounds containing a phosphate structure (−OPO(OR)2, where R is an organic group) in their molecular structure; silane additives are a class of compounds formed with silane (SiH4) as the parent body, in which some hydrogen atoms are replaced by organic groups; sultone additives refer to a class of compounds containing a sultone structure (containing one sulfur atom, two oxygen atoms and a cyclic structure).

[0072] In this application, the testing of relevant substances in the electrolyte can refer to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents", and the additives and solvents of the electrolyte are qualitatively and quantitatively analyzed by gas chromatography.

[0073] As an example, the carboxylate solvent can comprise 10%, 15%, 20%, 25%, or any other range of values ​​based on the total mass of the electrolyte. Low viscosity carboxylate solvents can improve electrolyte conductivity, but they are also more reactive and more prone to side reactions with active materials, resulting in increased gas production. By maintaining the carboxylate solvent content within the aforementioned range, electrolyte conductivity can be improved while also preventing excessive gas production, thereby ensuring longevity.

[0074] As an example, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent can be 20%, 25%, 30%, 35%, 40%, 45%, 49%, etc., or can be a range composed of any of the above values. Linear carbonates and carboxylates also play a role in improving conductivity. Their conductivity is lower than that of carboxylates, but their activity is lower. By keeping the content of linear carbonates within the above range, a complementary effect can be formed with the carboxylates, which not only ensures the level of conductivity, but also avoids excessive side reactions, taking into account both life and fast charging capabilities.

[0075] As an example, based on the total mass of the electrolyte, the total mass proportion of the non-lithium salt additives can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., or can be a range consisting of any of the above values.

[0076] According to some embodiments of the present application, the additive includes a carbonate additive and a phosphate additive. Based on the total mass of the electrolyte, the sum of the mass proportions of the carbonate additive and the phosphate additive is 1.2%-5%.

[0077] According to some embodiments of the present application, the additives include carbonate additives and phosphate additives, and the combined mass percentage of the carbonate additives and the phosphate additives is 0.1%-0.5% based on the total mass of the electrolyte. This allows for the formation of a stable interface film on the electrode surface, reducing side reactions between the electrolyte and the electrode surface and improving the cycle life of the battery cells.

[0078] As an example, the sum of the mass proportions of the carbonate additive and the phosphate additive may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., or may be within a range consisting of any of the above values.

[0079] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate (VC), and the phosphate additive includes tris(trimethylsilyl)phosphate (TMSP). The combined mass percentage of vinylene carbonate and tris(trimethylsilyl)phosphate, based on the total mass of the electrolyte, is 0.1%-0.5%. As a result, VC forms a stable SEI (solid electrolyte interface) film on the negative electrode surface, effectively preventing further decomposition of the electrolyte and co-intercalation of solvent molecules and lithium ions, thereby protecting the electrode material and improving the battery's cycling performance and stability. TMSP preferentially forms a stable CEI (solid electrolyte interface) film on the positive electrode surface, effectively inhibiting oxidative decomposition of the electrolyte and improving the battery's cycling performance and stability. By ensuring the combined mass of VC and TMSP is within the above range, a stable and appropriate interfacial film can be formed on the positive and negative electrode surfaces, ensuring the stability of the active material interface without excessively increasing the interfacial impedance, thus ensuring both material stability and interfacial impedance.

[0080] As an example, the carbonate additive includes vinylene carbonate, and the phosphate additive includes tris(trimethylsilyl)phosphate. Based on the total mass of the electrolyte, the sum of the mass proportions of the vinylene carbonate and the tris(trimethylsilyl)phosphate can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., or can be a range consisting of any of the above numerical values.

[0081] According to some embodiments of the present application, the carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate. As such, these carboxylate solvents have a relatively low molecular weight, which can reduce the viscosity of the electrolyte and increase the migration rate of lithium ions.

[0082] According to some embodiments of the present application, the electrolyte further includes a cyclic carbonate solvent, and the cyclic carbonate solvent includes one or more of ethylene carbonate (EC), propylene carbonate, and butylene carbonate.

[0083] When EC is included in the electrolyte, it has a high dielectric constant and can effectively dissolve lithium salts such as lithium hexafluorophosphate (LiPF6), giving the electrolyte good ionic conductivity. This ensures the rapid transfer of lithium ions between the positive and negative electrodes of the battery, which is crucial for the battery's charge and discharge performance. Because EC can effectively dissolve lithium salts and has high electrochemical stability, it can exist stably at higher voltages, allowing the battery to operate at higher voltages, thereby improving the battery's energy density.

[0084] During the first charge and discharge process of the battery, EC undergoes a reduction reaction on the surface of the negative electrode, forming a solid electrolyte interface film (SEI film). The SEI film can prevent the electrolyte from further reacting with the negative electrode active material, improving the cycle stability and safety of the battery cell.

[0085] The addition of EC can also lower the freezing point of the electrolyte. At low temperatures, EC helps maintain the fluidity of the electrolyte, so that lithium ions can still maintain a certain transmission capacity, thereby improving the battery's charge and discharge efficiency and capacity retention rate at low temperatures.

[0086] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate solvent is 20%-40%. For example, it can be 20%, 23%, 25%, 30%, 35%, 40%, etc., or it can be a range composed of any of the above numerical values. Thus, a stable SEI film is formed, the degree of ion dissociation of the electrolyte is improved, and the impact on the low-temperature performance of the battery cell is reduced. If the content of cyclic carbonate solvents exceeds 40%, on the one hand, it will lead to excessive generation of SEI, increase the interfacial impedance, and hinder the diffusion of lithium ions through the interface to the interior of the material. At the same time, it will lead to a decrease in the proportion of linear carbonate solvents and carboxylate solvents with lower viscosity, increase the viscosity of the electrolyte, reduce the liquid phase transmission rate of lithium ions, affect the ionic conductivity, and thus affect the fast charging cycle performance of the lithium-ion battery.

[0087] According to some embodiments of the present application, the electrolyte further includes a lithium salt additive, including one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium fluorosulfonate. Thus, these lithium salt additives can form a stable SEI film on the negative electrode surface, reducing side reactions between the electrolyte and the electrode surface, reducing electrolyte decomposition, and reducing gas production by the battery cells under high temperature conditions.

[0088] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate. Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.1%-4%.

[0089] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the weight percentage of the lithium salt additive is 0.1%-0.5% based on the total weight of the electrolyte. For example, the weight percentage may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., or any range consisting of the above values.

[0090] Lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate can increase the dissociation of lithium salts and improve the conductivity of lithium electrolytes. They can also significantly improve the cycling stability of LiPF6-based electrolyte systems. They also exhibit excellent thermal stability in high-temperature environments, inhibiting the generation of hydrofluoric acid and slowing the decomposition of lithium hexafluorophosphate. They can also improve interfacial stability by forming a good solid electrolyte interface (SEI film). However, excessive use of additives can lead to the formation of a denser interfacial film, resulting in an abnormal increase in interfacial impedance and deteriorating fast-charging performance.

[0091] It should be noted that as the battery cells are charged and discharged, when the amount of carbonate additives, sulfate additives, borate additives, phosphate additives, silane additives, and sultone additives added is small, and the additives in the electrolyte will be consumed during the formation and charge-discharge cycle to generate relevant components in the SEI film and / or CEI film, after disassembling the battery cells to obtain the electrolyte, when the content of carbonate additives, sulfate additives, borate additives, phosphate additives, silane additives, and sultone additives is tested by gas chromatography, the content may be 0.

[0092] Furthermore, regarding the addition of certain substances, such as additives, to the electrolyte, the content of additives in the battery cell electrolyte is related to the formation process, different battery life cycles, or different battery storage conditions due to the additives' role in film formation on the surface of the active material. Therefore, the additive content in a freshly prepared electrolyte may differ from that in an electrolyte obtained by reverse disassembling a battery cell. However, those skilled in the art can determine the approximate content range of the relevant substances in the fresh electrolyte based on the performance level of the battery cell (such as the number of cycles) and residual content. Similarly, those skilled in the art can also determine the approximate content range of the corresponding non-freshly prepared (i.e., after reverse disassembly) electrolyte based on the content of the freshly prepared additives, the performance requirements for the battery cell, the storage environment, etc.

[0093] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the fresh electrolyte, or it can be the content of the residual additive detected by reverse detection based on the actual battery status.

[0094] According to some embodiments of the present application, the electrolyte further includes an electrolyte salt, which includes lithium fluorinated sulfonyl imide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the mass of the electrolyte salt accounts for 12%-18%.

[0095] By adding lithium hexafluorophosphate and lithium fluorinated sulfonyl imide to the electrolyte at the same time and controlling the content of the electrolyte salt, the ionic conductivity of the electrolyte can be improved while reducing the generation of HF during battery cycling and storage, reducing the consumption rate of the electrolyte solvent, and improving the life of the battery cell.

[0096] In this application, the test of the content of lithium fluorinated sulfonyl imide and lithium hexafluorophosphate can refer to the standard JY / T020-2002 "General Rules for Ion Chromatography Analysis Methods". For example, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the battery cell has a charge state of approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell is used as a sample for testing using the ion chromatography method. The inorganic ion chromatogram is tested, and the corresponding inorganic species are compared based on the chromatographic peak position. The corresponding inorganic ion content percentage is calculated based on the peak area, and then the mass proportion of the fluorinated sulfonyl imide and the mass proportion of the lithium hexafluorophosphate are calculated.

[0097] According to some embodiments of the present application, the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):1. By ensuring that the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is within this range, on the one hand, HF generation is reduced, corrosion of the SEI film is reduced, electrolyte consumption is reduced, and the cycle performance of the battery cell is improved; on the other hand, the viscosity of the electrolyte is reduced, the lithium ion transmission rate is increased, and the fast charging performance of the battery cell is improved.

[0098] In the present application, by adding fluorinated lithium sulfonyl imide to the electrolyte, the dissociation effect of lithium ions can be promoted, thereby increasing the dissociation rate of lithium ions and the lithium salt concentration inside the electrolyte, thereby promoting the transmission of lithium ions.

[0099] In some embodiments, the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):1. If the content of the fluorinated lithium sulfonyl imide is too high, the fluorinated lithium sulfonyl imide decomposes to produce fluoride ions, which combine with lithium ions to form lithium fluoride. Excessive lithium fluoride will increase the interface impedance and deteriorate the power and fast charging performance.

[0100] As an example, the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide can be 1.2:1, 1.5:1, 2:1, 2.5:1, 3:1, etc., or can be within a range consisting of any of the above values.

[0101] According to some embodiments of the present application, the mass percentage of the lithium hexafluorophosphate may be 4%-14% based on the total mass of the electrolyte, for example, 4%, 6%, 8%, 10%, 12%, 14%, or any range thereof.

[0102] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorinated sulfonyl imide lithium can be 4%-8%, for example, it can be 4%, 5%, 6%, 7%, 8%, etc., or it can be a range consisting of any of the above values.

[0103] As a result, the lithium ion migration rate is increased and the fast charging performance of the battery cell is improved.

[0104] In this application, when the content of the lithium salt compound is less than 4%, it can be considered as a lithium salt additive in the electrolyte; when the content of the lithium salt compound is greater than 4%, it can be considered as an electrolyte salt in the electrolyte.

[0105] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature is 10 mS / cm-13.5 mS / cm, thereby increasing the migration rate of lithium ions and improving the fast charging performance of the battery cell.

[0106] As an example, the conductivity of the electrolyte at room temperature can be 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 13.5 mS / cm, etc., or can be a range consisting of any of the above values.

[0107] In this application, after disassembling the battery cells to obtain the electrolyte, a conductivity meter is used. The conductivity of the electrolyte at room temperature can be tested with reference to HG-T 4067-2015.

[0108] According to some embodiments of the present application, the porosity of the positive electrode sheet can be 25%-30%. Therefore, by ensuring that the porosity of the positive electrode sheet is within the above range, the mass ratio of the positive electrode active material layer can be increased, and the lithium ion transmission rate can be increased, thereby improving the fast charging performance of the battery cell.

[0109] In this application, the porosity of the positive electrode plate can be tested by referring to the following method: place the sample cup containing the sample in a true density tester, close the test system, introduce helium according to the procedure, detect the pressure of the gas in the sample chamber and the expansion chamber, and then calculate the true volume according to Bohr's law (PV=nRT) to obtain the porosity of the sample to be tested.

[0110] According to some embodiments of the present application, the compaction density of the positive electrode active material layer can be 2.3 g / cm 3 -2.65g / cm 3 This increases the energy density of the battery cell.

[0111] The present application provides a method for testing the compaction density of the positive electrode active material layer: place the battery cell at 25°C, let it stand for 2 hours, charge it to 3.65V at a constant current of 1 / 3C, charge it to 0.05C at a constant voltage of 3.65V, let it stand for 2 hours, and then discharge it to 2.0V at a rate of 0.33C. The battery cell is disassembled to remove the positive electrode sheet, for example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode active material layer on one side can be wiped off first), punched into small discs with an area of ​​S1, weighed, recorded as M1, and its thickness H1 is measured. Then wipe off the positive electrode active material layer of the weighed positive electrode sheet, weigh the weight of the positive electrode collector, record it as M0, and measure its thickness H0. The single-side coating weight of the positive electrode active material layer = (M1-M0) / S1, the thickness of the positive electrode active material layer = H1-H0, and the compaction density of the positive electrode active material layer = the single-side coating weight of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0112] As an example, the compaction density of the positive electrode active material layer can be 2.3 g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 , 2.65g / cm 3 etc., or can be within the range of any of the above numerical values.

[0113] According to some specific embodiments of the present application, the compaction density of the positive electrode active material layer can be 2.45 g / cm 3 -2.58g / cm 3 .

[0114] According to some embodiments of the present application, the coating weight of the positive electrode active material layer on one side may be 0.26 g / 1540.25 mm 2 -0.33g / 1540.25mm 2 This increases the energy density of the battery cell.

[0115] This application provides a method for testing the coating weight of the positive electrode active material layer: A battery cell is disassembled to remove the positive electrode sheet. For example, a single-sided coated positive electrode sheet (if a double-sided coated sheet is used, the positive electrode active material layer on one side can be wiped off first) is punched into small discs with an area of ​​S1. These discs are weighed and recorded as M1. The positive electrode active material layer of the weighed positive electrode sheet is then wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0. The single-sided coating weight of the positive electrode active material layer = (M1 - M0) / S1.

[0116] As an example, the coating weight of the positive electrode active material layer on one side may be 0.26 g / 1540.25 mm 2、0.28g / 1540.25mm 2 、0.3g / 1540.25mm 2 、0.31g / 1540.25mm 2 、0.33g / 1540.25mm 2 etc., or can be within the range of any of the above numerical values.

[0117] According to some embodiments of the present application, the coating weight of the positive electrode active material layer on one side may be 0.28 g / 1540.25 mm 2 -0.32g / 1540.25mm 2 .

[0118] According to some embodiments of the present application, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

[0119] According to some embodiments of the present application, the lithium-containing phosphate includes lithium iron phosphate, and the average particle size of the lithium iron phosphate primary particles is 300nm-800nm. As a result, the average particle size of the primary particles is relatively small, and the lithium ion deintercalation path in the positive electrode active material is shortened, which can increase the lithium ion deintercalation rate and improve the fast charging performance of the battery cell.

[0120] In this application, the test method for the average particle size of primary particles is to use plasma to cut the positive electrode sheet along its thickness direction to obtain a cross-section of the positive electrode sheet, observe it under an appropriate magnification using a scanning electron microscope (SEM), and randomly select at least 50 primary particles. The average particle size of a single primary particle = (the longest diameter of a single particle + the shortest diameter of a single particle) / 2, and the average value of the selected primary particles is the average particle size of the primary particles.

[0121] As an example, the average particle size of the lithium iron phosphate primary particles can be 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, etc., or can be within a range consisting of any of the above values.

[0122] According to some embodiments of the present application, the lithium iron phosphate includes a doping element, wherein the doping element includes one or more of V, Ti, Mg, and Nb. By doping the lithium iron phosphate with these elements, iron dissolution can be reduced, the rate of lithium ion insertion and extraction can be increased, the power performance of the battery can be improved, and the compaction density of the positive electrode active material layer can be improved.

[0123] According to some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass proportion of the V element is 0.02%-0.2%, the mass proportion of the Ti element is 0.03%-0.2%, the mass proportion of the Mg element is 0.02%-0.1%, and the mass proportion of the Nb element is 0.02%-0.2%.

[0124] As an example, the mass proportion of the V element is 0.02%, 0.05%, 0.1%, 0.15%, 0.2%, etc., or can be a range consisting of any of the above values.

[0125] As an example, the mass proportion of the Ti element is 0.03%, 0.05%, 0.1%, 0.15%, 0.2%, etc., or can be a range consisting of any of the above values.

[0126] As an example, the mass proportion of the Mg element is 0.02%, 0.05%, 0.1%, etc., or can be a range consisting of any of the above values.

[0127] As an example, the mass proportion of the Nb element is 0.02%, 0.05%, 0.1%, 0.15%, 0.2%, etc., or can be a range consisting of any of the above values.

[0128] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0129] In some embodiments, the positive electrode active material layer may further optionally include a binder. For example, the binder may 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.

[0130] In some embodiments, the positive electrode active material layer may further include a conductive agent. For 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.

[0131] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0132] According to some embodiments of the present application, the porosity of the negative electrode sheet may be 25%-30%, thereby increasing the content of the negative electrode active material, improving the energy density of the battery cell, and improving the transmission rate of lithium ions.

[0133] In this application, the porosity test method of the negative electrode sheet is as follows: a sample cup containing a sample is placed in a true density tester, a closed test system is used, helium is introduced according to the procedure, the pressure of the gas in the sample chamber and the expansion chamber is detected, and the true volume is calculated according to Bohr's law (PV=nRT), thereby obtaining the porosity of the negative electrode sheet.

[0134] As an example, the porosity of the negative electrode sheet may be 25%, 26%, 27%, 28%, 29%, 30%, etc., or may be within a range consisting of any of the above values.

[0135] According to some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a carbon-based material.

[0136] According to some embodiments of the present application, the carbon-based material includes graphite, thereby improving the cycle performance of the battery cell.

[0137] According to some embodiments of the present application, the graphite includes secondary particles, and at least a portion of the surface of the secondary particles has amorphous carbon.

[0138] In the present application, secondary particles refer to particles formed by the aggregation of two or more primary particles.

[0139] In this article, amorphous carbon refers to a transitional carbon material with a very low degree of graphitization and crystallization, nearly amorphous (or lacking a fixed shape and periodic structural regularity). In this application, amorphous carbon refers to the product of carbonization of an organic carbon source, which has a large number of end faces and defects and a high number of lithium ion sites.

[0140] Secondary particles can increase the migration rate of lithium ions, improve the transmission performance of lithium ions, facilitate the embedding and extraction of lithium ions, and help improve the ion conductivity of the material. Amorphous carbon can also improve the conductivity of graphite secondary particles. The secondary particles in the inner core and the coating layer of amorphous carbon jointly improve the electronic and ion conductivity of the material, which helps to improve the fast charging performance of the battery cell.

[0141] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 7 μm-12 μm.

[0142] Therefore, the volume average particle size of graphite is smaller, which can shorten the solid phase migration path of lithium ions and improve the fast charging capability of the battery cell. At the same time, by making the volume average particle size within the above range, the side reaction between the graphite negative electrode and the electrolyte can also be reduced.

[0143] In this application, Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage reaching 50%, as measured, for example, using a laser particle size analyzer (Malvern Master Size 2000) in accordance with GB / T 19077-2016 / ISO 13320:2009. The specific testing process is as follows: the battery cell is discharged to 0% SOC, then the negative electrode is disassembled and removed. A certain amount of powder on the electrode is scraped with a blade, then rinsed with deionized water and repeatedly shaken for 5-10 times. After drying, the powder is sintered in a tube furnace at 400°C for 2 hours. After sintering, an appropriate amount of the sample to be tested (the sample concentration should be 8%-12% obscuration) is taken, deionized water is added, and ultrasonic dispersion is performed to ensure complete dispersion of the sample. The sample is then measured in accordance with GB / T 19077-2016 / ISO 13320:2009.

[0144] According to some embodiments of the present application, the graphite has a degree of graphitization of 90%-94%, thereby improving the ion conductivity and electron conductivity of the graphite and enhancing the rate performance of the battery.

[0145] In this application, the test method for the graphitization degree of graphite is to disassemble the battery cell to obtain the negative electrode sheet, scrape off the powder on the negative electrode sheet, and test it according to the following steps: Pretreatment: Weigh according to the ratio of carbon:silicon = 5:1, and then grind it in a clean mortar for 50 minutes to ensure uniform mixing; 2. Sample preparation: The powder obtained above is placed in a sample trough with a depth of 0.5mm and a diameter of 25mm, and prepared according to the flat sample preparation method; 3. Test: On the X-ray diffractometer, within the range of a starting angle of 52° and an ending angle of 58°, a scanning test is performed with a step length of 0.00836° and a step length of 0.3s per step; 4. Calculate the degree of graphitization based on the test 002 crystal plane interlayer spacing (d002).

[0146] According to some embodiments of the present application, the compaction density of the negative electrode active material layer can be 1.3 g / cm 3 -1.52g / cm 3 This increases the energy density of the battery cell.

[0147] The present application provides a method for testing the compaction density of the negative electrode active material layer: charge to 3.65V at a constant current of 1 / 3C, charge to 0.05C at a constant voltage of 3.65V, place the battery cell at 25°C, let it stand for 2h, and then discharge it to 2.0V at a rate of 0.33C. The battery cell is disassembled to remove the negative electrode pole piece, for example, a single-sided coated negative electrode pole piece (if it is a double-sided coated pole piece, the negative electrode active material layer on one side can be wiped off first), punched into small discs with an area of ​​S2, weighed, recorded as M3, and its thickness H3 is measured. Then wipe off the negative electrode active material layer of the weighed negative electrode pole piece, weigh the weight of the negative electrode current collector, record it as M2, and measure its thickness H2. The single-side coating weight of the negative electrode active material layer = (M3-M2) / S2, the thickness of the negative electrode active material layer = H3-H2, and the compaction density of the negative electrode active material layer = the single-side coating weight of the negative electrode active material layer / the thickness of the negative electrode active material layer.

[0148] As an example, the compaction density of the negative electrode active material layer may be 1.3 g / cm 3 , 1.35g / cm 3 , 1.4g / cm 3 , 1.45g / cm 3 , 1.52g / cm 3 etc., or can be within the range of any of the above numerical values.

[0149] According to some embodiments of the present application, the coating weight of the negative electrode active material layer on one side may be 0.12 g / 1540.25 mm 2 -0.15g / 1540.25mm 2 This increases the energy density of the battery cell.

[0150] This application provides a method for testing the coating weight of the negative electrode active material layer: Disassemble the battery cell to remove the negative electrode sheet. For example, take a negative electrode sheet coated on one side (if it is coated on both sides, wipe off the negative electrode active material layer on one side first). Punch it into small discs with an area of ​​S2, weigh them, and record them as M3. Then wipe off the negative electrode active material layer of the weighed negative electrode sheet, weigh the negative electrode current collector, and record them as M2. The single-sided coating weight of the negative electrode active material layer = (M3 - M2) / S2.

[0151] As an example, the coating weight of the negative electrode active material layer on one side may be 0.12 g / 1540.25 mm 2 、0.13g / 1540.25mm 2 、0.14g / 1540.25mm 2 、0.15g / 1540.25mm 2 etc., or can be within the range of any of the above numerical values.

[0152] According to some specific embodiments of the present application, the coating weight of the negative electrode active material layer on one side can be 0.125g / 1540.25mm 2 -0.14g / 1540.25mm 2 .

[0153] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer 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) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0154] In some embodiments, the negative electrode active material 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).

[0155] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0156] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0157] In some embodiments, the negative electrode sheet can be prepared by the following method: 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 current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0158] According to some specific embodiments of the present application, each layer of the positive electrode sheets is provided with a positive electrode tab, and each layer of the negative electrode sheets is provided with a negative electrode tab, thereby improving current transmission efficiency, reducing the resistance of the battery cells, and improving the rate performance of the battery.

[0159] According to some embodiments of the present application, reference Figure 1Along the width direction of the battery cell 1, the size of the battery cell 1 is 120mm-350mm, along the height direction of the battery cell 1, the size of the battery cell 1 is 80mm-120mm, and along the thickness direction of the battery cell 1, the size of the battery cell 1 is 25mm-80mm.

[0160] As an example, along the width direction of the battery cell, the size of the battery cell may be 120 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, etc., or may be a range consisting of any of the above values.

[0161] As an example, along the height direction of the battery cell, the size of the battery cell may be 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, etc., or may be within a range consisting of any of the above values.

[0162] As an example, along the thickness direction of the battery cell, the size of the battery cell may be 25 mm, 45 mm, 65 mm, 75 mm, 80 mm, etc., or may be within a range consisting of any of the above values.

[0163] 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.

[0164] The third aspect of the present application provides an electrical device, comprising 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 provides electrical energy for the electrical device.

[0165] The power-consuming device includes at least one of the battery cells, battery modules, or battery packs provided herein. The battery cells, battery modules, or battery packs can serve as either a power source or an energy storage unit for the power-consuming device. The power-consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0166] As the electrical equipment, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0167] Figure 2This is an example of an electric device. This electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device, a battery pack or battery module can be used.

[0168] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0169] 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 drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0170] Example 1

[0171] 1. Preparation of positive electrode sheet

[0172] The positive electrode sheet includes a positive electrode collector, a positive electrode active material layer and a positive electrode conductive layer. The positive electrode active material layer is arranged on both sides of the positive electrode collector. The positive electrode conductive layer is located between the positive electrode collector and the positive electrode active material layer. The positive electrode collector is aluminum foil.

[0173] The positive electrode conductive layer on the positive electrode current collector is a film layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride PVDF and the solvent N-methylpyrrolidone (NMP), and then coating it on the surface of the positive electrode current collector and drying it. The thickness is 1 μm, and the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 50%, and the mass content of the positive electrode binder is 50%.

[0174] The positive electrode active material layer includes a film layer formed by uniformly coating the positive electrode slurry (solvent is NMP) on the surface of the positive electrode conductive layer, drying, and cold pressing. The positive electrode active material layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black in a mass ratio of 97:1.5:1.5.

[0175] The positive electrode active material includes lithium iron phosphate particles, which are doped with the elements V, Ti, Mg, and Nb. Based on the total mass of the positive electrode active material layer, V accounts for 0.09% by weight, Ti accounts for 0.04% by weight, Nb accounts for 0.02% by weight, and Mg accounts for 0.04% by weight. The average particle size of the primary particles of the lithium iron phosphate material is 400nm.

[0176] The single-side coating weight of the positive electrode active material layer is 0.3g / 1540.25mm 2 .

[0177] The compacted density of the positive electrode active material layer is 2.54 g / cm 3 .

[0178] The size of the positive electrode active material layer along the height direction of the battery cell is 89 mm, and the size of the positive electrode active material layer along the width direction of the battery cell is 200.5 mm.

[0179] 2. Preparation of negative electrode sheet

[0180] The negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer and a negative electrode conductive layer. The negative electrode active material layer is arranged on both sides of the negative electrode current collector. The negative electrode conductive layer is located between the negative electrode current collector and the negative electrode active material layer. The negative electrode current collector is copper foil.

[0181] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by evenly mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na) and the solvent water, and then coating it on the surface of the negative electrode current collector and drying it. The thickness is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 40%, the mass content of the negative electrode binder in the negative electrode conductive layer is 55%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0182] The negative electrode active material layer includes a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, drying, and cold pressing.

[0183] The negative electrode active material layer includes a negative electrode active material with a mass ratio of 96.5:0.7:1.8:1, a conductive agent acetylene black, a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose. The graphite particles include artificial graphite particles. The surface of the artificial graphite has amorphous carbon, the mass proportion of carbon element is 3.5%, and the Dv50 of the graphite particles is 10.2 μm.

[0184] The single-side coating weight of the negative electrode active material layer is 0.137 g / 1540.25 mm 2 .

[0185] The compaction density of the negative electrode active material layer is 1.43 g / cm 3 .

[0186] 3. Isolation film

[0187] The isolation film includes a base film and coatings provided on both sides of the base film, wherein the base film includes a 7 μm polyethylene film layer with a porosity of 42%;

[0188] The side of the base film facing the positive electrode has a first coating layer and a second coating layer, and the side of the base film facing the negative electrode has a second coating layer, and the thickness of the second coating layer on both sides of the base film is the same;

[0189] The first coating layer includes polyacrylate and aluminum oxide particles dispersed on the polyacrylate. The first coating layer is a film layer formed by applying the first slurry to one side of the base film. The thickness of the first coating layer is 2 μm, and the average particle size of the aluminum oxide particles is 0.8 μm. The first coating layer includes aluminum oxide particles and a binder polyacrylate.

[0190] The second coating layer is a composite particle formed by polyacrylate and polyvinylidene fluoride (PVDF) particles dispersed on the polyacrylate. The second coating layer is a film layer formed by applying the second slurry on the base film (or the first coating layer). The average particle size of the PVDF particles is 200nm. The second slurry includes polyacrylate and PVDF particles. The total thickness of the two second coating layers is 1μm.

[0191] OH1 is 2mm and OH2 is 2.5mm.

[0192] 4. Preparation of Electrolyte

[0193] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), a chain carboxylate solvent ethyl acetate, a linear carbonate solvent (including dimethyl carbonate (DMC), ethyl methyl carbonate (EMC)), and a cyclic carbonate solvent ethylene carbonate (EC) are mixed to obtain an organic solvent, and the electrolyte salt and additives are dissolved in the above solvent and mixed evenly to obtain an electrolyte.

[0194] Based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 16%, the mass proportion of linear carbonate solvents is 36.6% (wherein the mass ratio of DMC and EMC is 35:10), and the mass proportion of cyclic carbonate solvents is 28.4%.

[0195] The additives include vinylene carbonate (VC), (tris(trimethylsilyl) phosphate) (TMSP), lithium tetrafluoroborate (LiBF4), lithium fluorosulfonate, and lithium difluorooxalatoborate (LiDFOB). Based on the total mass of the electrolyte, the mass proportion of VC is 2%, the mass proportion of TMSP is 0.5%, the mass proportion of LiBF4 is 0.5%, the mass proportion of lithium fluorosulfonate is 0.5%, and the mass proportion of LiDFOB is 0.5%.

[0196] The electrolyte salts include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6). Based on the total mass of the electrolyte, LiFSI accounts for 10% by weight and LiPF6 accounts for 5% by weight. The electrolyte conductivity at room temperature is 13mS / cm.

[0197] 5. Preparation of battery cells

[0198] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets to provide insulation. This produces a laminated electrode assembly. The electrode assembly is then placed in a housing, on which positive and negative terminals are provided. After baking, the electrolyte is injected. The battery cell is vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell. The cell measures 105.5 mm in height, 208.5 mm in width, and 50 mm in thickness.

[0199] Performance Testing

[0200] 1. Cycle performance under fast charging conditions

[0201] Charge from 0% SOC to 10% SOC at 0.5C constant current;

[0202] Afterwards, illustratively, the step of charging the battery device or any battery cell constituting the battery device from 10% SOC to 80% SOC may be performed as follows:

[0203] Charge from 10% SOC to 15% SOC at 5.0C constant current;

[0204] Charge from 15% SOC to 20% SOC at 4.6C constant current;

[0205] Charge from 20% SOC to 35% SOC at 4.2C constant current;

[0206] Charge from 35% SOC to 45% SOC at 3.8C constant current;

[0207] Charge from 45% SOC to 50% SOC at 3.6C constant current;

[0208] Charge from 50% SOC to 60% SOC at 3.4C constant current;

[0209] Charge from 60% SOC to 70% SOC at 3.0C constant current;

[0210] Charge from 70% SOC to 75% SOC at 2.8C constant current;

[0211] Charge from 75% SOC to 80% SOC at 2.4C constant current;

[0212] Then charge from 80% SOC to 100% SOC at 0.5C constant current;

[0213] After fully charged, discharge at 1C to 2.5V.

[0214] Repeat the above steps until the capacity decays to 80% SOH of the initial capacity, and count the number of cycles.

[0215] It should be noted that even if the initial addition amounts of various substances in the battery electrolytes of different embodiments are the same, considering the differences in storage and usage environment, the contents of various substances after disassembly of the batteries of different embodiments may be the same or different, and not necessarily exactly the same.

[0216] Example 2

[0217] The preparation method of the battery monomer is the same as that of Example 1, except that the mass proportion of ethyl acetate is 20%, and the mass proportion of the linear carbonate solvent is 32.6%.

[0218] Example 3

[0219] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 25%, and the mass proportion of the linear carbonate solvent is 27.6%.

[0220] Example 4

[0221] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 10%, and the mass proportion of the linear carbonate solvent is 42.6%.

[0222] Example 5

[0223] The preparation method of the battery monomer is the same as that of Example 1, except that the carboxylate solvent is propyl acetate.

[0224] Comparative Example 1

[0225] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 35%, and the mass proportion of the linear carbonate solvent is 17.6%.

[0226] Comparative Example 2

[0227] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 2%, and the mass proportion of the linear carbonate solvent is 50.6%.

[0228] The detailed differences and test results of the battery cells in Examples 1 to 5, Comparative Example 1, and Comparative Example 2 are shown in Table 1.

[0229] Table 1

[0230]

[0231] As shown in Table 1, when the additive content in the electrolyte is constant, if the carboxylate ester solvent content is too low or too high, the cycle life of the battery cell under fast-charging conditions will be reduced. If the carboxylate ester solvent content is too low, the electrolyte viscosity is high, slowing the lithium ion transfer rate; if the carboxylate ester solvent content is too high, the electrolyte gassing during the cycle is high, reducing the cycle life of the battery cell. By ensuring that the carboxylate ester solvent content is within the range specified in this application, a battery cell with a longer cycle life under fast-charging conditions can be obtained.

[0232] As can be seen from Examples 1 and 5, when the carboxylate solvent content is within the range specified in this application, different types of carboxylate additives can improve the cycle life of battery cells under fast charging conditions. However, due to its lower conductivity than ethyl acetate, propyl acetate does not improve the cycle life of battery cells to the same extent as ethyl acetate.

[0233] It can also be seen from Table 1 that when the content of carboxylic acid ester solvents is different, the ionic conductivity of the electrolyte can be improved by combining different contents of linear carbonate solvents, thereby increasing the transmission rate of lithium ions and improving the fast charging performance of the battery cell.

[0234] Example 6

[0235] The preparation method of the battery monomer is the same as that of Example 1, except that the linear carbonate solvent is diethyl carbonate.

[0236] The detailed differences and test results of the battery cells in Example 1 and Example 6 are shown in Table 2.

[0237] Table 2

[0238]

[0239] As can be seen from Table 2, the cycle life of battery cells under fast charging conditions can be improved by selecting different types of linear carbonate solvents and controlling the content of carboxylic acid ester solvents and additives within the range specified in this application.

[0240] The prepared fresh battery cells are subjected to a formation process, and the specific formation process is as follows:

[0241] 1. Let it stand for 30 seconds; 2. Charge at 0.05C for 14 minutes; 3. Let it stand for 10 seconds; 4. Charge at 0.05C for 58 minutes; 5. Let it stand for 10 seconds; 6. Charge at 0.1C for 24 minutes; 7. Let it stand for 10 seconds; 8. Charge at 0.28C for 43 minutes; 9. Let it stand for 5 minutes.

[0242] After formation, the battery cells were stored at 25°C for 180 days and discharged at 0.33C to 2.5V. The cells were then disassembled and the electrolyte was separated, and the relevant components in the electrolyte were tested.

[0243] Example 1

[0244] Based on the total mass of the electrolyte obtained after disassembling the above-mentioned battery cells, the mass proportion of VC is 0.16%, the mass proportion of TMSP is 0.13%, and the sum of the mass proportions of VC and TMSP is 0.29%.

[0245] Example 7

[0246] The preparation method of the battery cell is the same as that of Example 1, except that, in the electrolyte preparation stage, based on the total mass of the electrolyte, the mass proportion of VC is 1%, the mass proportion of TMSP is 0.2%, the sum of the mass proportions of VC and TMSP is 1.2%, and the mass proportion of the linear carbonate solvent is 37.9%.

[0247] Based on the total mass of the electrolyte obtained after disassembling the above-mentioned battery cells, the mass proportion of VC is 0.07%, the mass proportion of TMSP is 0.03%, and the sum of the mass proportions of VC and TMSP is 0.1%.

[0248] Example 8

[0249] The preparation method of the battery cell is the same as that of Example 1, except that, in the electrolyte preparation stage, based on the total mass of the electrolyte, the mass proportion of VC is 3%, the mass proportion of TMSP is 2%, the sum of the mass proportions of VC and TMSP is 5%, and the mass proportion of the linear carbonate solvent is 34.1%.

[0250] Based on the total mass of the electrolyte obtained after disassembling the above-mentioned battery cells, the mass proportion of VC is 0.26%, the mass proportion of TMSP is 0.24%, and the sum of the mass proportions of VC and TMSP is 0.5%.

[0251] Comparative Example 3

[0252] The preparation method of the battery cell is the same as that of Example 1, except that, in the electrolyte preparation stage, based on the total mass of the electrolyte, the mass proportion of VC is 0.5%, the mass proportion of TMSP is 0.1%, the sum of the mass proportions of VC and TMSP is 0.6%, and the mass proportion of the linear carbonate solvent is 38.5%.

[0253] Based on the total mass of the electrolyte obtained after disassembling the above-mentioned battery cells, the mass proportion of VC is 0.03%, the mass proportion of TMSP is 0.01%, and the sum of the mass proportions of VC and TMSP is 0.04%.

[0254] Comparative Example 4

[0255] The preparation method of the battery cell is the same as that of Example 1, except that, in the electrolyte preparation stage, based on the total mass of the electrolyte, the mass proportion of VC is 4%, the mass proportion of TMSP is 2%, the sum of the mass proportions of VC and TMSP is 6%, and the mass proportion of the linear carbonate solvent is 33.1%.

[0256] Based on the total mass of the electrolyte obtained after disassembling the above-mentioned battery cells, the mass proportion of VC is 0.6%, the mass proportion of TMSP is 0.25%, and the total mass proportion of VC and TMSP is 0.85%.

[0257] The detailed differences and test results of the battery cells in Example 1, Example 7, Example 8, Comparative Example 3, and Comparative Example 4 are shown in Table 3.

[0258] Table 3

[0259] As can be seen from Table 3, when carboxylate solvents and linear carbonate solvents are within the scope of protection of this application, adjusting the content of additives in the electrolyte can further improve the cycle life of the battery cell under fast charging conditions. If the additive content is too low, the improvement in the battery cell's cycle performance will not be significant; if the additive content is too high, the film formation impedance will increase, which will also reduce the battery cell's cycle performance.

[0260] Example 9

[0261] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 46.6%, the mass proportion of EC is 18.4%, and the conductivity of the electrolyte at room temperature is 13.5 mS / cm.

[0262] Example 10

[0263] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 45%, the mass proportion of EC is 20%, and the conductivity of the electrolyte at room temperature is 12.9 mS / cm.

[0264] Example 11

[0265] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 25%, the mass proportion of EC is 40%, and the conductivity of the electrolyte at room temperature is 12.7 mS / cm.

[0266] Example 12

[0267] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 21.6%, the mass proportion of EC is 43.4%, and the conductivity of the electrolyte at room temperature is 12.6 mS / cm.

[0268] The detailed differences between the battery cells in Examples 9 to 12 and the test results are shown in Table 4.

[0269] Table 4

[0270]

[0271] It can be seen from Table 4 that when the content of carboxylic acid ester solvents, linear carbonate solvents, and additives is controlled within the protection scope of this application, the content of cyclic carbonate solvents in the electrolyte can also be adjusted. By making the mass proportion of cyclic carbonate solvents within the protection scope of this application, the cycle performance of the battery cell under fast charging conditions can be further improved.

[0272] Example 13

[0273] The preparation method of the battery monomer is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 37.6%, the mass proportion of LiPF6 is 7%, the mass proportion of LiFSI is 7%, the mass ratio of LiPF6 to LiFSI is 1:1, and the conductivity of the electrolyte at room temperature is 13.2 mS / cm.

[0274] Example 14

[0275] The preparation method of the battery monomer is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 38.8%, the mass proportion of LiPF6 is 7%, the mass proportion of LiFSI is 5.83%, the mass ratio of LiPF6 to LiFSI is 1.2:1, and the conductivity of the electrolyte at room temperature is 12.8 mS / cm.

[0276] Example 15

[0277] The preparation method of the battery monomer is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 35.6%, the mass proportion of LiPF6 is 12%, the mass proportion of LiFSI is 4%, the mass ratio of LiPF6 to LiFSI is 3:1, and the conductivity of the electrolyte at room temperature is 13.1 mS / cm.

[0278] Example 16

[0279] The preparation method of the battery monomer is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of the linear carbonate solvent is 35.9%, the mass proportion of LiPF6 is 12%, the mass proportion of LiFSI is 3.75%, the mass ratio of LiPF6 to LiFSI is 3.2:1, and the conductivity of the electrolyte at room temperature is 12.8 mS / cm.

[0280] The detailed differences between the battery cells in Examples 1 and 13 to 16 and the test results are shown in Table 5.

[0281] Table 5

[0282]

[0283] It can be seen from Table 5 that when the contents of carboxylic acid ester solvents, linear carbonate solvents and additives in the electrolyte are within the protection range defined in this application, by making the mass ratio of LiPF6 to LiFSI within the protection range defined in this application, the ionic conductivity of the electrolyte can be improved while reducing the generation of HF during the cycle and storage of the battery, reducing the consumption rate of the electrolyte solvent, and improving the cycle life of the battery cell under fast charging conditions.

[0284] 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 make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions 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: The invention comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector, and the positive electrode active material layer comprises a lithium-containing phosphate; The electrolyte includes a carboxylate solvent and a linear carbonate solvent, and the carboxylate solvent includes a compound represented by Formula I: Formula I, Wherein, R1 includes any one of a C1-C5 alkyl group and a C1-C5 haloalkyl group, and R2 includes any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group and a C1-C5 haloalkyl group; The linear carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; Based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent is 10%-25%, and the mass proportion of the linear carbonate solvent is 20%-49%; The electrolyte further includes a non-lithium salt additive, wherein the non-lithium salt additive includes a phosphate additive, and the non-lithium salt additive further includes at least one of a carbonate additive, a sulfate additive, a borate additive, a silane additive, and a sultone additive. Based on the total mass of the electrolyte, the total mass of the non-lithium salt additive accounts for 0.1% to 5%; The electrolyte further includes an electrolyte salt, which includes fluorinated lithium sulfonyl imide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the mass of the electrolyte salt accounts for 12%-18%.

2. The battery cell according to claim 1, wherein: The non-lithium salt additives include carbonate additives and phosphate additives. Based on the total mass of the electrolyte, the total mass proportion of the carbonate additives and the phosphate additives is 1.2%-5%.

3. The battery cell according to claim 1, wherein: The non-lithium salt additives include carbonate additives and phosphate additives. Based on the total mass of the electrolyte, the total mass proportion of the carbonate additives and the phosphate additives is 0.1%-0.5%.

4. The battery cell according to claim 3, characterized in that The carbonate additive includes vinylene carbonate, and the phosphate additive includes tris(trimethylsilyl)phosphate. Based on the total mass of the electrolyte, the sum of the mass proportions of vinylene carbonate and tris(trimethylsilyl)phosphate is 0.1%-0.5%.

5. The battery cell according to claim 1, characterized in that The carboxylate solvent includes one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate.

6. The battery cell according to claim 1, characterized in that The electrolyte further includes a cyclic carbonate solvent, and the cyclic carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, and butylene carbonate.

7. The battery cell according to claim 6, characterized in that Based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate solvent is 20%-40%.

8. The battery cell according to claim 1, wherein: The electrolyte further includes a lithium salt additive, and the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium fluorosulfonate.

9. The battery cell according to claim 8, characterized in that The lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate. Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.1%-4%.

10. The battery cell according to claim 8, characterized in that The lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate. Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.1%-0.5%.

11. The battery cell according to claim 1, characterized in that The mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):

1.

12. The battery cell according to claim 1, wherein Based on the total mass of the electrolyte, the mass of the lithium hexafluorophosphate accounts for 4%-14%.

13. The battery cell according to claim 1, characterized in that Based on the total mass of the electrolyte, the mass proportion of the fluorinated lithium sulfonyl imide is 4%-8%.

14. The battery cell according to claim 1, characterized in that The conductivity of the electrolyte at room temperature is 10 mS / cm-13.5 mS / cm.

15. The battery cell according to claim 1, characterized in that The porosity of the positive electrode sheet is 25%-30%.

16. The battery cell according to claim 1, characterized in that The compaction density of the positive electrode active material layer is 2.3 g / cm 3 -2.6g / cm 3 .

17. The battery cell according to claim 1, characterized in that The compaction density of the positive electrode active material layer is 2.45 g / cm 3 -2.58g / cm 3 .

18. The battery cell according to claim 1, characterized in that The coating weight of the positive electrode active material layer on one side is 0.27 g / 1540.25 mm 2 -0.33g / 1540.25mm 2 .

19. The battery cell according to claim 1, characterized in that The coating weight of the positive electrode active material layer on one side is 0.28 g / 1540.25 mm 2 -0.32g / 1540.25mm 2 .

20. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

21. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes lithium iron phosphate, and the average particle size of the lithium iron phosphate primary particles is 300nm-800nm.

22. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes a doping element, and the doping element includes one or more of V, Ti, Mg, and Nb.

23. The battery cell according to claim 22, characterized in that Based on the total mass of the positive electrode active material layer, the mass proportion of the V element is 0.02%-0.2%, the mass proportion of the Ti element is 0.03%-0.2%, the mass proportion of the Nb element is 0.02%-0.2%, and the mass proportion of the Mg element is 0.02%-0.1%.

24. The battery cell according to claim 1, characterized in that The electrode assembly further includes a negative electrode sheet, and the porosity of the negative electrode sheet is 25%-30%.

25. The battery cell according to claim 24, characterized in that The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes a carbon-based material.

26. The battery cell according to claim 25, characterized in that The carbon-based material includes graphite.

27. The battery cell according to claim 26, characterized in that The graphite includes secondary particles, and at least a portion of the surface of the secondary particles has amorphous carbon.

28. The battery cell according to claim 26, characterized in that The volume average particle size Dv50 of the graphite is 7 μm-12 μm.

29. The battery cell according to claim 26, characterized in that The graphitization degree of the graphite is 90%-94%.

30. The battery cell according to claim 25, characterized in that The compaction density of the negative electrode active material layer is 1.3 g / cm 3 -1.52g / cm 3 .

31. The battery cell according to claim 25, characterized in that The coating weight of the negative electrode active material layer on one side is 0.12 g / 1540.25 mm 2 -0.15g / 1540.25mm 2 .

32. The battery cell according to claim 25, characterized in that The coating weight of the negative electrode active material layer on one side is 0.125 g / 1540.25 mm 2 -0.14g / 1540.25mm 2 .

33. The battery cell according to claim 24, characterized in that Each layer of the positive electrode sheet is provided with a positive electrode tab, and each layer of the negative electrode sheet is provided with a negative electrode tab.

34. The battery cell according to claim 1, characterized in that The size of the battery cell is 120 mm to 350 mm along the width direction of the battery cell, 80 mm to 120 mm along the height direction of the battery cell, and 25 mm to 80 mm along the thickness direction of the battery cell.

35. A battery device, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 34, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

36. An electrical device, characterized in that: The battery cell according to any one of claims 1 to 34 or the battery device according to claim 35 is used to provide electrical energy.

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