A battery cell, a battery device, and an electrical device

Abstract

Battery cell, including: negative electrode plates comprising a negative current collector and a negative film layer arranged on at least one side of the negative current collector, wherein the negative film layer comprises negative active material, the negative active material comprising carbon-based material; positive electrode plates comprising a positive current collector and a positive film layer arranged on at least one side of the positive current collector, the positive film layer comprising positive active material and positive additive, the positive active material comprising lithium phosphate and the positive additive comprising at least one of lithium-containing iron oxide and lithium-containing cobalt oxide; and an electrolyte solution comprising an organic solvent, wherein the organic solvent comprises a carboxylic acid ester solvent, the mass fraction of the carboxylic acid ester solvent in the electrolyte solution being 3% to 70%.

Description

TECHNICAL AREA

[0001] This application relates to a battery cell, a battery device and an electrical device. TECHNICAL BACKGROUND

[0002] Battery cells are characterized by high capacity and long lifespan and are therefore frequently used in electronic devices such as mobile phones, laptops, e-bikes, electric vehicles, electric aircraft, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools. Due to the enormous advances in battery technology, ever higher demands are being placed on battery performance. However, the high-temperature cycle performance of battery cells still needs to be improved. BRIEF DESCRIPTION OF THE INVENTION

[0003] The present application provides a battery cell, a battery device and an electrical device, wherein the high-temperature cycle performance of the battery cell of the present application can be further improved.

[0004] First, in the embodiments of the present application, a battery cell is provided, wherein the battery cell comprises negative electrode plates, positive electrode plates, and an electrolyte solution, wherein the negative electrode plate comprises a negative current collector and a negative film layer arranged on at least one side of the negative current collector, wherein the negative film layer comprises negative active material, the negative active material comprising carbon-based material, wherein the positive electrode plates comprise a positive current collector and a positive film layer arranged on at least one side of the positive current collector, the positive film layer comprising positive active material and a positive additive, the positive active material comprising lithium phosphate, and the positive additive comprising at least one of lithium-containing iron oxide and lithium-containing cobalt oxide.wherein the electrolyte solution comprises an organic solvent, wherein the organic solvent comprises a carboxylic acid ester solvent, the mass fraction of the carboxylic acid ester solvent in the electrolyte solution being 3% to 70%.

[0005] If the mass fraction of the carboxylic acid ester solvent in the electrolyte solution in the embodiment of the present application is within the aforementioned range, active ions, for example lithium ions, migrate in the electrolyte solution at a higher migration rate, which improves the fast-charging capability of the battery cell; By adding positive additives to the positive electrode plate, the oxygen released by the positive additives can participate in the formation of the negative film layer, thereby repairing the solid electrolyte membrane and improving high-temperature cycle performance; Preferably, the positive active material in the embodiment of the present application comprises lithium phosphate and the negative active material comprises carbon-based material, wherein the cycle stability of the positive and negative active materials is high, which contributes to a further improvement in high-temperature cycle performance;Therefore, the embodiment of the present application can effectively improve the high-temperature cycle performance of the battery cell.

[0006] In some embodiments, the lithium-containing iron oxide comprises lithium ferrite and / or the lithium-containing cobalt oxide comprises lithium cobaltate. The materials mentioned above can contribute to the formation of the negative film layer and improve the cycle performance of the battery cell.

[0007] In some embodiments, the lithium-containing iron oxide comprises Li e F e O f , where 0 < e ≤ 5 and 0 < f ≤ 4. The materials mentioned above can contribute to the formation of the negative film layer and improve the cycle performance of the battery cell.

[0008] In some embodiments, the lithium-containing iron oxide comprises at least one of Li5FeO4, Li3FeO4. 3.5, LiFeO2. The above-mentioned materials can be involved in the formation of the negative film layer and improve the cycle performance of the battery cell.

[0009] In some embodiments, the lithium-containing cobalt oxide comprises Li g CoO h , where 0 < g ≤ 6 and 0 < h ≤ 4. The materials mentioned above can contribute to the formation of the negative film layer and improve the cycle performance of the battery cell.

[0010] In some embodiments, the lithium-containing cobalt oxide comprises one or more of Li6CoO4, Li3CoO2, or LiCoO2. The aforementioned materials can contribute to the formation of the negative film layer and improve the cycle performance of the battery cell.

[0011] In some embodiments, the mass fraction of the positive additive, based on the mass of the positive film layer, is 0.5% to 3%. Using a positive additive in the aforementioned mass range can effectively improve the stability of the positive additive while simultaneously achieving a good oxygen release effect.

[0012] In some embodiments, the surface of the positive additive is additionally provided with a carbon coating. The structure of the positive additive coated with a carbon layer is more stable and can mitigate side reactions between the electrolyte solution and the positive additive, thereby further improving the cycle performance of the battery cell.

[0013] In some embodiments, the mass fraction of the carbon cover layer in the positive additive is 1% to 5%. If the mass fraction of the carbon cover layer is within the aforementioned range, the positive additive can be more effectively protected, which promotes the gradual release of oxygen.

[0014] In some embodiments, the positive additive is in particle form and is provided in a cross-section of the positive film layer along its thickness direction, with the ratio between the longest and shortest diameter of the positive additive in a particle being 1.2 to 2.5. Using the positive additive with the aforementioned particle size can effectively improve its stability while simultaneously achieving a good oxygen release effect.

[0015] In some embodiments, several positive additives are present in the cross-section of the positive film layer along its thickness direction, with the average longest diameter of the several positive additives being 9 µm to 13 µm; when using a positive additive with the above-mentioned particle size, in addition to an effective improvement in the stability of the positive additive, a good effect of oxygen release can also be achieved.

[0016] In some embodiments, several positive additives are present in the cross-section of the positive film layer along its thickness direction, with the average shortest diameter of the multiple positive additives being 5 µm to 9 µm. Using the positive additive with the aforementioned particle size can effectively improve its stability while simultaneously achieving a good oxygen release effect.

[0017] In some embodiments, both the lithium phosphate and the positive additive are present in the form of multiple particles, wherein the average longest diameter of the multiple lithium phosphates in a cross-section of the positive film layer along its thickness direction is smaller than the average shortest diameter of the multiple positive additives. Using the positive additive with the aforementioned particle size can effectively improve the stability of the positive additive while simultaneously achieving a good oxygen release effect. The migration path of the lithium ions in the lithium phosphate is shorter, which reduces heat generation, decreases heat accumulation in the system, lowers the risk of electrolyte solution decomposition, and further improves cycle performance.

[0018] In some embodiments, the lithium phosphate comprises several first phosphate particles and several second phosphate particles, wherein the longest diameter of the first phosphate particles is larger than the longest diameter of the second phosphate particles, the average longest diameter of the several first phosphate particles is 1 µm to 5 µm, and the average longest diameter of the several second phosphate particles is 0.1 µm to 0.5 µm. When the lithium phosphate meets the above conditions, its longest diameter is relatively small, the lithium debedding path within the lithium phosphate is short, and less heat is generated. Furthermore, the particle size of the aforementioned lithium phosphate is not too small, so that essentially no agglomeration occurs during processing and manufacturing, thus maintaining stable properties of the lithium phosphate.

[0019] In some embodiments, the mass fraction of the second phosphate particles in the lithium phosphate is 80% to 95%. The mass fraction of second phosphate particles is within a suitable range, for example between 80% and 95%, which further reduces heat generation, decreases the heat generation in the battery cell system, reduces the risk of decomposition of the electrolyte components due to heat accumulation, and improves the cycle performance of the battery cell.

[0020] In some embodiments, the lithium phosphate includes lithium iron phosphate, which results in excellent cycle stability of the lithium iron phosphate and can improve the cycle performance of the battery cell.

[0021] In some embodiments, the electrical conductivity of the electrolyte solution at room temperature ranges from 9 mS / cm to 18 mS / cm. The lithium ions migrate at a higher rate in the electrolyte solution, which further reduces the internal resistance of the battery cell, minimizes heat generation, and improves the fast-charging capability of the battery cell.

[0022] In some embodiments, the mass fraction of the carboxylic acid ester solvent in the electrolyte solution is 5% to 30%. When the mass fraction of the carboxylic acid ester solvent is within the aforementioned range, the conductivity of the electrolyte solution can be increased; furthermore, the electrolyte solution is compatible with the silicon-containing negative electrode, thereby effectively reducing gas evolution in the battery cell and improving the fast-charging capability of the battery cell.

[0023] In some embodiments, the carboxylic acid ester solvent comprises cyclic carboxylic acid esters, wherein the cyclic carboxylic acid ester comprises one or more of γ-butyrolactone, γ-pentyrolactone and δ-pentyrolactone.

[0024] In some embodiments, the carboxylic acid ester solvent comprises chain carboxylic acid esters, wherein the chain carboxylic acid ester comprises one or more of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propionyl propyl ester and propionyl butyl ester.

[0025] In some embodiments, the organic solvent further comprises carbonate solvents, wherein the carbonate solvent comprises one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate.

[0026] The combined use of carbonate solvents and carboxylic acid ester solvents can increase the stability of the electrolyte solution and reduce its high-temperature gas production.

[0027] In some embodiments, the electrolyte solution further comprises lithium salt, wherein the lithium salt comprises lithium bifluorosulfonamide and lithium hexafluorophosphate, wherein the ratio of the mass fraction of lithium bifluorosulfonamide to the mass fraction of lithium hexafluorophosphate, based on the mass of the electrolyte solution, is 0.3 to 1.2.

[0028] If the ratio between the mass fraction of lithium hexafluorophosphate and lithium bifluorosulfonamide in the embodiment of the present application is within the aforementioned range, the hydrofluoric acid content can be reduced, the side reaction at the interface of the negative electrode can be reduced, and gas evolution during storage at high temperatures can be reduced; on the other hand, gas evolution during storage at high temperatures can also be reduced by a suitable content of organic components in the interfacial film formed at the interface of the negative electrode.

[0029] In some embodiments, the mass fraction of lithium bifluorosulfonamide, based on the mass of the electrolyte solution, is 2% to 11%. If the mass fraction of lithium bifluorosulfonamide is within the aforementioned range, the hydrofluoric acid content can be reduced, the side reaction at the interface of the negative electrode can be reduced, and gas evolution during storage at high temperatures can be decreased, which contributes to improving the service life of the battery cell at high temperatures.

[0030] In some embodiments, the mass fraction of lithium hexafluorophosphate, based on the mass of the electrolyte solution, is 3% to 14%. When the mass fraction of lithium hexafluorophosphate is within the aforementioned range, the conductivity of the electrolyte solution is relatively high, which promotes the migration of lithium ions and improves the fast-charging capability of the battery cell.

[0031] In some embodiments, the electrolyte solution further comprises one or more fluorinated cyclic carbonates and vinylidene carbonate. Fluorinated cyclic carbonates can form a lithium fluoride (LiF)-enriched interfacial film on the surface of the negative electrode, which mitigates the volume expansion of silicon and improves the lifetime of silicon-containing systems. The combined use of fluorinated cyclic carbonates and vinylidene carbonate results in a denser interfacial film on the surface of the negative electrode, thereby more effectively protecting the silicon-containing negative electrode, reducing the extent of side reactions at the negative electrode interface, and improving cycle performance.

[0032] In some embodiments, the fluorinated cyclic carbonate comprises at least one of ethylene fluorocarbonate, ethylene difluorocarbonate and trifluoropropylene carbonate.

[0033] In some embodiments, the mass fraction of the fluorinated cyclic carbonate, based on the mass of the electrolyte solution, is 0.5% to 20%. When the mass fraction of the fluorinated cyclic carbonate is within the aforementioned range, an excellent interfacial film can be formed, which provides excellent protection for the negative electrode.

[0034] In some embodiments, the mass fraction of vinylidene carbonate, based on the mass of the electrolyte solution, is 0.1% to 3%. The vinylidene carbonate participates in the formation of the negative interfacial film and can form an excellent interfacial film, which provides excellent protection for the negative electrode.

[0035] In some embodiments, the mass fraction of the fluorinated cyclic carbonate, based on the mass of the electrolyte solution, is 0.5% to 10%; the mass fraction of the silicon element in the silicon-based material in the negative active material is 0.3% to 7.5%. If the mass fraction of the fluorinated cyclic carbonate and the mass fraction of the silicon element meet the above-mentioned conditions, the volume expansion of the silicon can be more effectively mitigated, which improves the lifetime of the silicon-containing system and the cycle performance.

[0036] In some embodiments, the mass fraction of the fluorinated cyclic carbonate, based on the mass of the electrolyte solution, is greater than 10% and less than or equal to 20%; the mass fraction of the silicon element in the silicon-based material in the negative active material is greater than 7.5% and less than or equal to 15%. When the mass fraction of the fluorinated cyclic carbonate and the mass fraction of the silicon element meet the above conditions, the volumetric expansion of the silicon can be more effectively mitigated, which improves the lifetime of the silicon-containing system and enhances cycle performance.

[0037] In some embodiments, the carbon-based material comprises at least one synthetic graphite and one natural graphite. The aforementioned structure exhibits excellent cycle stability and can further improve the cycle performance of the battery cell.

[0038] Secondly, the present application also provides a battery device comprising a battery cell according to one of the embodiments of the first aspect of the present application.

[0039] Thirdly, the present application also provides an electrical device comprising a battery device according to one of the embodiments of the second or third aspect of the present application. FIGURES

[0040] In order to illustrate the technical solution in the embodiments of the application more clearly, a brief description of the figures that must be used in the embodiments of the application follows, whereby it is obvious that the figures in the following description are only some embodiments for the application and that other figures can be obtained on the basis of the figures without creative effort by general technical personnel. Fig. Figure 1 is a schematic representation of the structure of an electrical device in some embodiments of the present application; Fig. Figure 2 is a schematic representation of the structure of a battery pack in some embodiments of the present application; Fig. Figure 3 is a schematic representation of the structure of a battery module in some embodiments of the present application; Fig. Figure 4 is a schematic representation of the structure of a battery cell in some embodiments of the present application; Fig. Figure 5 is a schematic representation of the structure of an electrode assembly of a battery cell in some embodiments of the present application; Fig. Figure 6 is a schematic representation of the structure of the negative electrode plate of the battery cell in some embodiments of the present application.

[0041] The figures may not be to scale. SPECIFIC EXECUTION FORMS

[0042] The embodiments of the battery cell, battery device, and electrical apparatus of the present application are disclosed in detail below with appropriate reference to the figures. However, there may be cases where unnecessary detailed descriptions are omitted. For example, detailed descriptions of things that are already well known and repetitive descriptions of practically the same structure are omitted. This is to avoid making the following description unnecessarily long and to facilitate understanding by the person skilled in the art. Furthermore, the figures and the following description serve to enable the person skilled in the art to fully understand the present application and are not intended to limit the subject matter specified in the claims.

[0043] The “range” disclosed here is defined in terms of a lower bound and an upper bound, and a particular range is defined by selecting a lower bound and an upper bound that establish the limits of that range. Ranges defined in this way can include or exclude end values ​​and can be combined in any way; that is, any lower bound can be combined with any upper bound to form a range. For example, if a range of 60 to 120 and 80 to 110 is specified for a given parameter, a range of 60 to 110 and 80 to 120 is also expected. Furthermore, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4, and 5, then all of the following ranges are predictable: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5.In this application, unless otherwise specified, the range of values ​​“a to b” denotes a shorthand representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the range of values ​​“0 to 5” denotes all real numbers between 0 and 5 listed in this document, where 0 to 5 is merely a shorthand for these combinations of numbers. When a parameter is specified as an integer ≥ 2, this is equivalent to disclosing that parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise stated, all embodiments and optional embodiments of this application may be combined to form new technical solutions. Unless otherwise stated, all technical features and optional technical features of this application may be combined to form new technical solutions. Unless otherwise stated, all steps of this application may be carried out sequentially or randomly, with sequential execution being preferred. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially or steps (b) and (a) carried out sequentially.For example, if it is mentioned that the procedure may also include step (c), this means that step (c) can be included in the procedure in any order; for example, the procedure may include steps (a), (b) and (c), it may also include steps (a), (c) and (b), or it may include steps (c), (a) and (b), etc.

[0045] The term “several” in this application refers to two or more (including two).

[0046] With the rapid development in battery technology, the demands on the performance of battery cells are also increasing. For example, the increasing demands on fast charging capability can be met by increasing the conductivity of the electrolyte solution, but this can lead to decomposition of the electrolyte solution at high temperatures, which increases gas evolution in the battery cells at high temperatures and can impair the high-temperature cycle performance of the battery cells.

[0047] In light of the aforementioned problems, the embodiments of the present application improve the high-temperature cycle performance of the battery cell through coordinated regulation of the positive electrode plate and the electrolyte solution. In particular, the electrolyte solution of the battery cell comprises carboxylic acid ester solvents, which can improve the conductivity of the electrolyte solution, thereby enabling the rapid migration of active ions such as lithium ions and thus enhancing the fast-charging capability of the battery cell. However, an excessive concentration of carboxylic acid ester solvents can lead to side reactions at the interface on the surface of the negative electrode, producing acidic substances that can degrade the solid electrolyte interface film (SEI film) on the surface of the negative electrode and impair its high-temperature lifespan.In the embodiment of the present application, a positive additive is added to the positive electrode plate; the oxygen released by the positive additive can participate in the formation of the negative film layer, thereby repairing the SEI film and reducing the effects of carboxylic acid ester solvents on the cycle performance of the battery cell.

[0048] The battery cells of this application are suitable for various battery devices and electrical equipment that use battery cells.

[0049] For example, electrical devices can be mobile phones, portable devices, laptops, electric bicycles, electric toys, power tools, vehicles, ships, and spacecraft. Or, for example, electrical devices can be spacecraft, including airplanes, rockets, space shuttles, and spacecraft.

[0050] Fig. Figure 1 is a schematic representation of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the electrical device 1, battery packs or battery modules can be used.

[0051] The electrical device 1 has an internal battery device that can be located at the bottom, top, or rear of the electrical device 1. The battery device can be used to supply power to the electrical device 1, for example, as an operating power source for the electrical device 1 or as a propulsion power source for the electrical device 1, in order to provide propulsion power for the electrical device 1 instead of, or partially instead of, fuel or natural gas. The in Fig. 1. The battery device shown is a battery pack. 2.

[0052] The electrical device 1 can also include a controller 3 and a motor 4, wherein the controller 3 serves to control the power supply to the motor 4 by the battery device, for example for starting, navigation and operation of the electrical device 1 while driving.

[0053] A battery apparatus can comprise one or more battery cell assemblies to provide voltage and capacity. The battery cell assembly can include a plurality of battery cells, with the plurality of battery cells connected in series, parallel, or mixed configurations via a busbar.

[0054] In some embodiments, the battery cell assembly is typically formed by arranging a plurality of battery cells. For example, the battery cell assembly can be a battery module, wherein the battery module is formed from a plurality of battery cells arranged and secured to form a single module. The battery module can be formed, for example, by bonding the multiple battery cells together.

[0055] As in Fig. As shown in Figure 2, in some embodiments the battery device can be a battery pack 2, wherein the battery pack 2 comprises a box 5 and one or more battery cell assemblies, the battery cell assemblies being housed in the box 5.

[0056] For example, the battery cell assembly can also be housed in box 5 by attaching a large number of battery cells directly to box 5.

[0057] Box 5, for example, consists of a first box part 5a and a second box part 5b. Box 5 has a receiving compartment 5c, and the first box part 5a and the second box part 5b are snapped together to form a closed space inside box 5 for receiving the battery cell assembly. "Closed" here means covered or enclosed, which may or may not be sealed. The first box part 5a can be a top cover or a bottom plate.

[0058] For example, the box 5 can consist of a cover, a frame, and a base plate. The top cover and the base plate are each connected to the frame, creating an enclosed space inside the box 5 in which the battery cell assembly is housed.

[0059] In some embodiments, the box 5 can be part of a vehicle's chassis structure.

[0060] For example, part of box 5 can be at least part of the vehicle floor, or part of box 5 can be at least part of the vehicle's cross and longitudinal beams.

[0061] The battery cell assembly can, for example, be a battery module 6, and the battery cell assembly can be housed in the box 5 by attaching the battery module 6 in the box 5.

[0062] As in Fig. As shown in Figure 3, the battery module 6 comprises a multitude of battery cells 7.

[0063] As in Fig. 4 and Fig. As shown in Figure 5, in some embodiments the battery cell 7 comprises an electrode assembly 10 and a housing assembly 20.

[0064] The housing assembly 20 has a receiving cavity which serves to receive the electrode assembly 10 and the electrolyte solution.

[0065] In some embodiments, the housing assembly 20 comprises an outer housing and an electrode connection 23, wherein the electrode connection 23 is arranged on the outer housing.

[0066] The outer housing can be made of steel, aluminum, plastic (e.g., polypropylene), a metal composite material (e.g., a copper-aluminum composite housing), or an aluminum-plastic foil. In some embodiments, the outer housing can have a sealed or an unsealed structure. For example, if the outer housing has an unsealed structure, it serves to protect the electrode assembly 10, with a sealed pouch arranged between the outer housing and the electrode assembly 10, serving to enclose the electrode assembly 10 and the electrolytes. In particular, the sealed pouch can be a pouch-like insulating element or an aluminum-plastic foil. If the outer housing has a sealed structure, it serves to enclose the electrode assembly 10 and the electrolytes, as well as other components.

[0067] For example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a softpack battery cell or a battery cell of another shape, wherein the prismatic battery cell includes a square battery cell, a knife-shaped battery cell, a multiple prism battery, for example a hexagonal prism battery, etc., without any particular restrictions being given in the present application.

[0068] In some embodiments, the outer housing comprises an end cover 22 and a housing 21, wherein the housing 21 is provided with an opening and the end cover 22 covers the opening. The housing 21 may be provided with one or more openings. The end cover 22 may also have one or more openings.

[0069] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, a housing 21 with a cylindrical structure can be selected; if the electrode assembly 10 has a rectangular structure, a housing 21 with a rectangular structure can be selected. Preferably, both the electrode assembly 10 and the housing 21 can have a rectangular structure.

[0070] The electrode connection 23 can be located on the housing 21 or on the end cover 22. The electrode connection 23 is electrically connected to the electrode tab of the electrode plate. The electrode connection 23 can be directly connected to the electrode tab or indirectly connected to the electrode tab via a current collector.

[0071] The electrode assembly 10 can be a wound structure, a stacked structure or a mixed structure of wound and stacked structure.

[0072] In some embodiments, the electrode assembly 10 has a winding structure. The positive electrode plate 11 and the negative electrode plate 12 are wound into a winding structure.

[0073] In some embodiments, the electrode assembly 10 has a stacked structure.

[0074] For example, several positive electrode plates 11 and several negative electrode plates 12 can be provided, wherein several positive electrode plates 11 and several negative electrode plates 12 are arranged alternately on top of each other.

[0075] For example, several positive electrode plates 11 can be provided, wherein the negative electrode plate 12 is folded to form several stacked folded sections, between each of which a positive electrode plate 11 is held.

[0076] For example, both the positive electrode plate 11 and the negative electrode plate 12 can be folded to form several folded sections arranged on top of each other.

[0077] For example, several separating elements 13 can be provided, each arranged between any adjacent positive electrode plates 11 or negative electrode plates 12.

[0078] For example, the separating elements 13 can be arranged continuously and can be positioned by folding or winding between any adjacent positive electrode plates 11 or negative electrode plates 12.

[0079] In some embodiments, the shape of the electrode assembly 10 can be cylindrical, flat or prismatic.

[0080] In some embodiments, the electrode assembly 10 is provided with electrode tabs that can conduct current away from the electrode assembly 10. The electrode tab comprises a positive electrode tab and a negative electrode tab. The electrode assembly 10 can have a wound structure or a stacked structure, with the stacked structure being advantageous for increasing the energy density of the battery cell 7.

[0081] In some embodiments, the battery cell 7 comprises positive electrode plates 11 and an electrolyte solution, wherein the positive electrode plates 11 comprise a positive current collector and a positive film layer arranged on at least one side of the positive current collector, wherein the positive film layer comprises positive active material and positive additive, wherein the positive active material comprises lithium phosphate and the positive additive comprises at least one of lithium-containing iron oxide and lithium-containing cobalt oxide, wherein the electrolyte solution comprises an organic solvent, wherein the organic solvent comprises a carboxylic acid ester solvent, the mass fraction of the carboxylic acid ester solvent in the electrolyte solution being 3% to 70%.

[0082] The mass fraction of the carboxylic acid ester solvent in the electrolyte solution is greater than or equal to 3%, which results in a relatively high migration rate of active ions such as lithium ions in the electrolyte solution, thus improving the fast charging capability of battery cell 7.

[0083] With increasing mass fraction of the carboxylic acid ester solvent, the migration rate of the active ions increases; however, the carboxylic acid ester solvent tends to cause side reactions at the interface of the negative electrode, producing acidic substances that destroy the SEI film on the surface of the negative electrode and reduce the service life of the battery cell 7 at high temperatures; The embodiment of the present application limits, on the one hand, the maximum addition of carboxylic acid ester solvents so that the mass fraction of the carboxylic acid ester solvent is less than or equal to 70%. On the other hand, a positive additive is added to the positive electrode plate, whereby the lithium ions of the positive additive migrate through the electrolyte solution to the negative electrode side during the charging process.The migration of lithium ions causes the positive additive to form negative electron groups, which are then released into the electrolyte solution by oxygen. This oxygen can contribute to the formation of the negative film layer, repair the SEI film, and reduce the effects of carboxylic acid ester solvents on the battery cell's lifespan at high temperatures.

[0084] Preferably, the positive active material of the present application comprises lithium phosphate, while the negative active material comprises a carbon-based material. The high cycle stability of the positive and negative active materials contributes to a further improvement in high-temperature cycle performance.

[0085] This allows the embodiment of the present application to effectively improve the high-temperature cycle performance of battery cell 7 under fast charging. Negative electrode plate

[0086] The negative electrode plate comprises a negative current collector and a negative film layer arranged on at least one side of the negative current collector and comprising negative active material. For example, the negative current collector has two surfaces opposite in its thickness direction, with the negative film layer arranged on one or both of the two opposite surfaces of the negative current collector.

[0087] The maximum charging voltage and the discharge cut-off voltage of the battery cell differ depending on the positive active material. For example, if the phosphate material contains lithium iron phosphate, the maximum charging voltage can be 3.65 V and the discharge cut-off voltage 2.0 V, or the maximum charging voltage can be 3.8 V and the discharge cut-off voltage 2.0 V. Another example: For phosphate materials such as lithium manganese iron phosphate, the maximum charging voltage can be 4.3 V and the discharge cut-off voltage 2.0 V. The following describes the state of the battery cell using the example of a maximum charging voltage of 3.8 V and a discharge cut-off voltage of 2.0 V: In the embodiment of the present application, the 100% state of charge (SOC) and the 0% state of charge (SOC) of the battery cell are defined as follows:

[0088] The battery cell is charged at a constant charging current of 0.33C up to the maximum charging voltage and then charged at a constant voltage of 0.05C, which corresponds to a state of 100% SOC (State of Charge) of the battery cell. The battery cell is then discharged at a constant discharge current of 0.33C down to the cutoff voltage, which corresponds to a state of 0% SOC of the battery cell.

[0089] In some embodiments, the density of the negative film layer in a battery cell at 0% SOC is 1.1 g / cm³. 3 up to 1.7 g / cm³ 3 For example, the density of the negative film layer in a battery cell at 0% charge is 1.10 g / cm³. 3 , 1.12 g / cm³ 3 , 1.14 g / cm³ 3 , 1.16 g / cm³ 3 , 1.18 g / cm³ 3 , 1.20 g / cm³ 3 , 1.22 g / cm³ 3 , 1.24 g / cm³ 3 , 1.26 g / cm³ 3 , 1.28 g / cm³ 3 , 1.3 g / cm³ 3 , 1.32 g / cm³ 3, 1.35 g / cm³ 3 , 1.40 g / cm³ 3 , 1.45 g / cm³ 3 , 1.50 g / cm² 3 , 1.55 g / cm³ 3 , 1.60 g / cm³ 3 , 1.65 g / cm³ 3 , 1.66 g / cm³ 3 , 1.68 g / cm³ 3 , 1.70 g / cm³ 3 or lies within any range of two of the values ​​mentioned above.

[0090] If the compaction density of the negative film layer is in the above range, the thickness of the negative film layer will not be too great, which promotes fast charging of the battery cell; in addition, the particles of the negative active material will not be packed too densely, which reduces the risk of particle fragmentation and improves the cycle performance of the battery cell.

[0091] In some embodiments, the one-sided coating weight of the negative film layer is 80 mg / 1540.25 mm². 2 up to 150 mg / 1540.25 mm 2For example, the one-sided coating weight of the negative film layer is 80 mg / 1540.25 mm². 2 , 85 mg / 1540.25 mm 2 , 90 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 145 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 , 175 mg / 1540.25 mm 2 , 180 mg / 1540.25 mm 2 or lies within any range of two of the values ​​mentioned above.

[0092] If the one-sided coating weight of the negative film layer meets the above-mentioned range, it contributes, in conjunction with a silicon element with a suitable mass fraction, to increasing the energy density of the battery cell, and the migration rate of the active ions in the negative film layer is relatively fast, which improves the fast-charging capability of the battery cell.

[0093] In the embodiment of the present application, the density of the negative film layer of the battery cell at 0% state of charge (SOC) is known in the art, i.e., disassembling the negative electrode plate of the battery cell at 0% SOC and determining the density of the negative film layer, e.g., by taking a negative electrode plate coated with a single-sided coating (in the case of an electrode plate coated with a double-sided coating, one of the negative film layers can be wiped off first), punching and cutting the negative electrode plate into small discs with an area of ​​S1, weighing them, noting them as M1, and measuring the thickness H1. Then, after weighing, wiping off the negative film layer of the negative electrode plate, weighing the negative current collector, noting it as M0, and measuring its thickness H0.The one-sided coating weight of the negative film layer = (weight of the negative electrode plate M1 - weight of the negative current collector M0) / S1, and thickness of the negative film layer = thickness of the negative electrode plate H1 - thickness of the negative current collector H0, and the compaction density of the negative film layer = one-sided coating weight of the negative film layer / thickness of the negative film layer.

[0094] In some embodiments, the negative active material comprises a silicon-based material, and preferably the silicon-based material can be at least one of silicon monomers, a silicon-carbon complex, and silicon oxide SiO₂. x (0 < x ≤ 2). The materials mentioned above can increase the capacity of the negative active material, which helps to reduce the coating thickness of the negative film layer and shorten the migration path of the lithium ions.

[0095] In some embodiments, the specific surface area of ​​the silicon-based material is 1 m². 2 / g up to 4 m 2 / g, for example 1 m 2 / g, 1.2 m 2 / g, 1.4 m 2 / g, 1.5 m 2 / g, 1.6 m 2 / g, 1.8 m 2 / g, 2 m 2 / g, 2.2 m 2 / g, 2.4 m 2 / g, 2.5 m 2 / g, 2.6 m 2 / g, 2.8 m 2 / g, 3 m 2 / g, 3.2 m 2 / g, 3.4 m 2 / g, 3.5 m 2 / g, 3.6 m 2 / g, 3.8 m 2 / g, 4 m 2 / g or lies within any range of two of the values ​​mentioned above.

[0096] If the specific surface area of ​​the silicon-based material is within the aforementioned range, side reactions between the silicon-based material and the electrolyte solution can be mitigated and cycle performance improved; in addition, suitable sites for embedding lithium ions can be provided and fast-charging capability improved.

[0097] In the embodiment of the present application, the specific surface area of ​​the material has a meaning generally known in this field and can be measured using equipment and methods generally known in this field. For example, the test according to test standard GB / T 19587-2017 can be carried out by removing the negative electrode plate from the battery cell to obtain the relevant material as a sample and measuring the specific surface area with the Tri-Star 3020 pore size analyzer from Micromeritics of the USA.

[0098] In some embodiments, the silicon-based material is in particle form and has an average particle size of 4 µm to 12 µm, for example 4 µm, 4.5 µm, 5 µm, 5.5 µm, 6 µm, 6.5 µm, 7 µm, 7.5 µm, 8 µm, 8.5 µm, 9 µm, 9.5 µm, 10 µm, 10.5 µm, 11 µm, 11.5 µm, 12 µm or lies in any range of two of the above values.

[0099] If the specific surface area of ​​the silicon-based material is within the aforementioned range, it can provide suitable sites for lithium ion embedding and improve fast-charging capability; under fast-charging conditions, it can also mitigate side reactions between the silicon-based material and the electrolyte solution, reduce gas evolution at high temperatures, and improve the cycle performance of the battery cell.

[0100] In some embodiments, the negative active material comprises a carbon-based material that exhibits high cycle stability and can improve the cycle performance of the battery cell.

[0101] Preferably, the carbon-based material comprises at least one of synthetic graphite and one of natural graphite.

[0102] In some embodiments, the negative active material may, in addition to the carbon-based material mentioned above and the optional silicon-based material, also comprise at least one tin-based material and lithium titanate. The tin-based material may comprise at least one tin monomer, tin oxide, and tin alloy material.

[0103] The qualitative and quantitative determination of the individual substances or elements in this application can be carried out using suitable equipment and procedures known to those skilled in the field. The relevant test methods may refer to domestic and foreign test standards, domestic and foreign company standards, etc., and those skilled in the field may also adjust certain test steps / equipment parameters, etc., for reasons of test accuracy in order to obtain more precise test results. The qualitative or quantitative determination may be carried out using a single test method or a combination of several test methods.

[0104] For example, in this application, in conjunction with the general method for X-ray diffraction analysis JIS / K0131-1996, an X-ray powder diffraction test and qualitative analysis of the negative electrode plate or the negative active material can be performed.

[0105] Artificial and natural graphite can be distinguished using SEM profile images acquired with a scanning electron microscope (SEM). The SEM profile of natural graphite shows gaps between the flake-like structures, while the SEM profile of artificial graphite is dense and shows no obvious gaps. A further distinction can be made using the XRD spectrum, obtained by X-ray diffraction. The XRD spectrum of natural graphite shows a distinct 2H and 3R phase, while the XRD spectrum of artificial graphite shows only the 2H phase.

[0106] As in Fig.As shown in Figure 6, the negative film layer 121 of the negative electrode plate 12 in the embodiment of the present application comprises at least one film layer, wherein either a single film layer or at least two film layers can be used. Preferably, the negative film layer 121 comprises at least two film layers.

[0107] When a single film layer is used in the negative film layer 121, the negative active material of the negative film layer 121 comprises a carbon-based material and preferably a silicon-based material.

[0108] If at least two film layers are used in the negative film layer 121, the negative active material of the negative film layer 121 comprises a carbon-based material and preferably a silicon-based material. The negative film layer 121 can comprise two film layers, three film layers, four film layers, or even more film layers.

[0109] In some embodiments, the negative film layer 121 comprises a first negative film layer 1211 and a second negative film layer 1212, wherein the first negative film layer 1211 is arranged on the surface of the negative current collector 122 and the negative active material of the first negative film layer 1211 comprises carbon-based material, wherein the second negative film layer 1212 is connected to a side of the first negative film layer 1211 facing away from the negative current collector 122, and the negative active material of the second negative film layer 1212 comprises carbon-based material. The interface between the first negative film layer 1211 and the second negative film layer 1212 can be regular or irregular, preferably with an irregular interface being provided; or there can be no distinct interface between the first negative film layer 1211 and the second negative film layer 1212.

[0110] The negative film layer 121 comprises at least two film layers, with one layering contributing to improving both the fast charging capability and the lifespan of the battery cell.

[0111] In some embodiments, at least one of the first negative film layer 1211 and the second negative film layer 1212 comprises a silicon-based material.

[0112] Preferably, the first negative film layer 1211 also comprises a silicon-based material.

[0113] Preferably, the second negative film layer 1212 also comprises a silicon-based material.

[0114] For example, the first negative film layer 1211 comprises a carbon-based material and a silicon-based material, while the second negative film layer 1212 comprises a carbon-based material and a silicon-based material. Alternatively, the first negative film layer 1211 comprises a carbon-based material and a silicon-based material, while the second negative film layer 1212 comprises a carbon-based material. Alternatively, the first negative film layer 1211 comprises a carbon-based material, while the second negative film layer 1212 comprises a carbon-based material and a silicon-based material.

[0115] If both the first negative film layer 1211 and the second negative film layer 1212 comprise a silicon-based material, this is more advantageous for improving the energy density of the battery cell. In the case where the first negative film layer 1211 comprises a silicon-based material and the second negative film layer 1212 does not, the second negative film layer 1212 can reduce the volume expansion of the first negative film layer 1211, reduce the side reaction between the negative film layer 1211 and the electrolyte solution, and improve cycle performance.

[0116] In the case where the negative film layer 121 uses at least two film layers, the cross-sectional morphology of the negative film layer 121 along the thickness direction X of the negative film layer 121 can be the same or similar, and of course it can be different.

[0117] Along the thickness direction X of the negative film layer 121, the negative film layer 121 is subdivided into three regions: a first region 121a, a third region 121c, and a second region 121b. The first region 121a is the region of the negative film layer 121 near the negative current collector 122 along the thickness direction X, and the thickness of the first region 121a is 1 / 3 of the thickness of the negative film layer 121. The second region 121b is a region where the negative film layer 121 is away from the negative current collector 122 along the thickness direction X, and the thickness of the second region 121b is 1 / 3 of the thickness of the negative film layer 121.

[0118] The cross-sectional morphology of the first region 121a and the second region 121b can be the same or similar, and of course they can also be different. The cross-sectional morphology of the first region 121a and the third region 121c can be the same or similar, and of course they can also be different. The cross-sectional morphology of the second region 121b and the third region 121c can be the same or similar, and of course they can also be different.

[0119] A distinct layer interface may or may not exist between the first region 121a, the second region 121b, and the third region 121c. For example, the first negative film layer 1211 includes the first region 121a, the second negative film layer 1212 includes the second region 121b, the third region 121c may be part of the first negative film layer 1211, or the third region 121c may be part of the second negative film layer 1212, or the third region 121c may be part of both the first negative film layer 1211 and the second negative film layer 1212.

[0120] In some embodiments, in a cross-section of the negative film layer 121 parallel to the thickness direction X, the proportion of the cavities of the individual carbon-based material in the first region 121a is greater than or equal to the proportion of the cavities of the individual carbon-based material in the second region 121b. Preferably, the proportion of the cavities of the individual carbon-based material in the first region 121a can be smaller than the proportion of the cavities of the individual carbon-based material in the second region 121b.

[0121] The carbon-based material is in particle form and contains cavities. Along the cross-section of the negative film layer 121 parallel to the thickness direction X, the area of ​​the cavities is a percentage of the total cross-sectional area of ​​the carbon-based material, corresponding to the proportion of cavities in the individual carbon-based material.

[0122] During the charging process of the battery cell, lithium ions diffuse from the second region 121b into the first region 121a. The proportion of cavities of the single carbon-based material in the first region 121a is less than or equal to the proportion of cavities of the single carbon-based material in the second region 121b, which promotes the diffusion of lithium ions in the first region 121a, increases the transfer rate, and thus facilitates the fast charging of the battery cell.

[0123] Preferably, the average particle size of the carbon-based material in the first region 121a can be greater than or equal to the average particle size of the carbon-based material in the second region 121b. Furthermore, preferably, the average particle size of the carbon-based material in the first region 121a can be larger than the average particle size of the carbon-based material in the second region 121b, which promotes the rapid migration of lithium ions from the second region 121b to the first region 121a and improves the fast-charging capability of the battery cell. Alternatively, the average particle size of the carbon-based material in the first region 121a can be smaller than the average particle size of the carbon-based material in the second region 121b.

[0124] Preferably, the average particle size of the carbon-based material of the first negative film layer 1211 can be greater than or equal to the average particle size of the carbon-based material of the second negative film layer 1212. More preferably, the average particle size of the carbon-based material of the first negative film layer 1211 can be larger than the average particle size of the carbon-based material of the second negative film layer 1212.

[0125] The difference in particle size between the first negative film layer 1211 and the second negative film layer 1212 can improve the fast-charging capability of the battery cell. In particular, during fast charging, the overpotential of the second negative film layer 1212 is typically higher, so the bottleneck during fast charging is mainly in the second negative film layer 1212. In the embodiment of the present application, the particle size of the second negative film layer 1212 is relatively small, which shortens the solid-phase transfer path of the lithium ions, improves the fast-charging capability, and eliminates the problem of lithium deposition on the surface of the negative electrode plate 12.

[0126] Preferably, the average particle size of the carbon-based material in the first range 121a is 12 µm to 21 µm, for example 12 µm, 12.5 µm, 13 µm, 13.5 µm, 14 µm, 14.5 µm, 15 µm, 15.5 µm, 16 µm, 16.5 µm, 17 µm, 17.5 µm, 18 µm, 18.5 µm, 19 µm, 19.5 µm, 20 µm, 20.5 µm, 21 µm or lies in any range of two of the above values. If the average particle size of the carbon-based material in the first area 121a is within the range mentioned above, the lifetime can be improved without negatively impacting the fast charging capability.

[0127] Preferably, the average particle size of the carbon-based material in the first negative film layer 1211 can be between 12 µm and 21 µm. If the average particle size of the carbon-based material in the first negative film layer 1211 is within the aforementioned range, the cycle life can be improved without negatively impacting the fast-charging capability.

[0128] Preferably, the average particle size of the carbon-based material in the second range 121b is 9 µm to 17 µm, for example 9 µm, 9.5 µm, 10 µm, 10.5 µm, 11 µm, 11.5 µm, 12 µm, 12.5 µm, 13 µm, 13.5 µm, 14 µm, 14.5 µm, 15 µm, 15.5 µm, 16 µm, 16.5 µm, 17 µm or lies in any range of two of the above values. If the average particle size of the carbon-based material in the second negative film layer 1212 is within the range above, this contributes to improving the fast-charging capability of the battery cell and increasing the stability of the material.

[0129] Preferably, the average particle size of the carbon-based material in the second negative film layer 1212 can be between 9 µm and 17 µm. If the average particle size of the carbon-based material in the second negative film layer 1212 is within the above range, the solid-phase transfer path of the lithium ions can be shortened, and the fast-charging capability and stability of the material can be improved.

[0130] For example, the carbon-based material in the first area 121a includes synthetic graphite and natural graphite, while the carbon-based material in the second area 121b includes synthetic graphite. Similarly, the negative active material in the first area 121a includes silicon-based material, synthetic graphite, and natural graphite, while the negative active material in the second area 121b includes silicon-based material and synthetic graphite.

[0131] For example, the carbon-based material of the first negative film layer 1211 comprises synthetic graphite and natural graphite, while the carbon-based material of the second negative film layer 1212 comprises synthetic graphite. For example, the negative active material of the first negative film layer 1211 comprises silicon-based material, synthetic graphite, and natural graphite, while the negative active material of the second negative film layer 1212 comprises silicon-based material and synthetic graphite.

[0132] In some other embodiments, in a cross-section of the negative film layer 121 parallel to the thickness direction X, the proportion of the cavities of the individual carbon-based material in the first region 121a is smaller than the proportion of the cavities of the individual carbon-based material in the second region 121b.

[0133] During the charging process of the battery cell, lithium ions diffuse via the second area 121b into the first area 121a, with the proportion of cavities of the single carbon-based material being larger in the second area 121b, which facilitates the rapid transport of lithium ions from the second area 121b to the first area 121a and thus promotes the rapid charging of the battery cell.

[0134] Preferably, the average particle size of the carbon-based material in the first region 121a can be smaller than the average particle size of the carbon-based material in the second region 121b. The average particle size of the carbon-based material in the second region 121b is relatively larger, resulting in higher compressive strength during the film layer manufacturing process, which contributes to improved particle density. The average particle size of the carbon-based material in the first region 121a is relatively smaller, which allows for rapid lithium ion migration and improves the fast-charging capability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 121a can be greater than or equal to the average particle size of the carbon-based material in the second region 121b.

[0135] Preferably, the average particle size of the carbon-based material in the first range 121a is 9 µm to 17 µm, for example 9 µm, 9.5 µm, 10 µm, 10.5 µm, 11 µm, 11.5 µm, 12 µm, 12.5 µm, 13 µm, 13.5 µm, 14 µm, 14.5 µm, 15 µm, 15.5 µm, 16 µm, 16.5 µm, 17 µm or lies in any range of two of the above values.

[0136] Preferably, the average particle size of the carbon-based material of the first negative film layer 1211 can be between 9 µm and 17 µm.

[0137] Preferably, the average particle size of the carbon-based material in the second range 121b is 12 µm to 21 µm, for example 12 µm, 12.5 µm, 13 µm, 13.5 µm, 14 µm, 14.5 µm, 15 µm, 15.5 µm, 16 µm, 16.5 µm, 17 µm, 17.5 µm, 18 µm, 18.5 µm, 19 µm, 19.5 µm, 20 µm, 20.5 µm, 21 µm or lies in any range of two of the above values.

[0138] Preferably, the average particle size of the carbon-based material in the second negative film layer 1212 can be between 12 µm and 21 µm.

[0139] For example, the carbon-based material in the second region 121b comprises synthetic graphite and natural graphite, while the carbon-based material in the first region 121a comprises synthetic graphite. Preferably, the negative active material also comprises silicon-based material. For example, the negative active material in the second region 121b comprises silicon-based material, synthetic graphite, and natural graphite, while the negative active material in the first region 121a comprises silicon-based material and synthetic graphite.

[0140] For example, the carbon-based material of the second negative film layer 1212 comprises synthetic graphite and natural graphite, while the carbon-based material of the first negative film layer 1211 comprises synthetic graphite. Preferably, the negative active material also comprises silicon-based material. For example, the negative active material of the second negative film layer 1212 comprises silicon-based material, synthetic graphite, and natural graphite, while the negative active material of the first negative film layer 1211 comprises silicon-based material and synthetic graphite.

[0141] In the embodiment of the present application, the average particle size of the active material in the first region 121a and the second region 121b can be measured using the following equipment and methods: The negative electrode plate 12 is used as a sample and photographed along the thickness direction X of the negative film layer 121 with a scanning electron microscope (SEM) to obtain an SEM profile, and the particle size of the active material in the SEM profile is statistically recorded, and the average particle size of the active material is calculated from the statistically recorded quantity.

[0142] In some embodiments, the negative film layer may preferably also comprise a negative conductive element. The embodiment of the present application does not impose any particular restrictions regarding the type of negative conductive element. For example, the negative conductive element comprises at least one of the following elements, such as superconducting carbon, conductive graphite, carbon black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofiber. In some embodiments, the mass fraction of the negative conductive element is ≤ 5% based on the total weight of the negative film layer.

[0143] In some embodiments, the negative film layer may preferably also comprise a negative electrode binder. In some embodiments, the mass fraction of the negative electrode binder is ≤ 5% based on the total weight of the negative film layer.

[0144] In some embodiments, the negative film layer may preferably also comprise other additives. These other additives may include, for example, thickening agents, dispersing agents, and the like, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the mass fraction of the other additives is ≤ 2% based on the total weight of the negative film layer.

[0145] In some embodiments, the negative current collector can be a metal foil or a composite current collector. For example, a metal foil can be made of at least one foil of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, or a silver alloy. The composite current collector can comprise a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The metal material in the metal layer can, for example, comprise at least one of the following materials: copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, or a silver alloy. The polymer base layer can, for example, comprise at least one of the following materials: polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0146] The negative film layer is typically formed by applying the negative electrode slurry to the negative current collector, drying, and cold pressing. The negative electrode slurry is generally formed by dispersing the negative active material of the negative electrode, an optional conductive agent, an optional binder, and other optional additives in a solvent and mixing thoroughly. The solvent may include, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0147] The negative electrode plate does not preclude additional functional layers besides the negative film layer. In some embodiments, the negative electrode plate of the present application, for example, further comprises a negative conductive layer located between the negative current collector and the negative film layer and provided on the surface of the negative current collector. In further embodiments, the negative electrode plate of the present application additionally comprises a protective layer covering the surface of the negative film layer. Positive electrode plate

[0148] In some embodiments, the battery cell additionally includes a positive electrode plate.

[0149] The positive electrode plate comprises a positive current collector and a positive film layer arranged on at least one side of the positive current collector and comprising positive active material. For example, the positive current collector has two surfaces opposite in its thickness direction, with the positive film layer arranged on one or both of the two opposite surfaces of the positive current collector.

[0150] In some embodiments, the dimension of the positive film layer along the longitudinal direction of the positive electrode plate is 200 mm to 600 mm, for example 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm or lies in any range of two of the above values.

[0151] In an electrode assembly with a stacked structure, the longitudinal direction of the positive electrode plate is parallel to the longitudinal direction of the battery cell, and the dimension of the positive film layer along the longitudinal direction can be understood as the length of the positive film layer. The lateral direction of the positive electrode plate is parallel to the lateral direction of the battery cell, and the dimension of the positive film layer in the lateral direction can be understood as the width of the positive film layer.

[0152] For example, the longitudinal dimension of the positive film layer is 200 mm to 600 mm; the electrolyte solution comprises the organic solvent, which includes a carboxylic acid ester solvent, and the electrolyte solution has a conductivity of 9 mS / cm to 18 mS / cm at room temperature. The length of the positive film layer is matched to the aforementioned conductivity of the electrolyte solution, which increases the liquid-phase transport rate of lithium ions, improves the kinetic properties, and enhances the fast-charging capability of the battery cell; since the carboxylic acid ester solvent has a low viscosity, it can uniformly saturate the positive film layer, thus ensuring that the positive film layer is charged uniformly throughout.The lithium ions emerging from the positive film layer are distributed evenly on the negative electrode side, thereby reducing the risk of local side reactions on the negative electrode side and improving high-temperature cycle performance during fast charging.

[0153] Preferably, the longitudinal dimension of the positive film layer is 200 mm to 600 mm. The electrolyte solution comprises an organic solvent, which includes carboxylic acid ester solvents, the mass fraction of which in the electrolyte solution is between 3% and 70%, preferably between 5% and 30%. The aforementioned carboxylic acid ester solvent with the aforementioned mass fraction ensures a relatively low viscosity of the electrolyte solution, which promotes rapid penetration of the positive film layer. This results in a uniform charging and discharging performance of the positive film layer, which reduces the risk of lithium precipitation on the negative electrode side and increases the service life of the battery cell.

[0154] In some embodiments, the density of the positive film layer in a battery cell at 0% SOC is 2.20 g / cm³. 3 up to 2.85 g / cm³ 3For example, the density of the positive film layer in a battery cell at 0% SOC is 2.20 g / cm³. 3 , 2.25 g / cm³ 3 , 2.30 g / cm³ 3 , 2.32 g / cm³ 3 , 2.35 g / cm³ 3 , 2.38 g / cm³ 3 , 2.40 g / cm³ 3 , 2.42 g / cm³ 3 , 2.45 g / cm³ 3 , 2.48 g / cm³ 3 , 2.50 g / cm³ 3 , 2.52 g / cm³ 3 , 2.55 g / cm³ 3 , 2.56 g / cm³ 3 , 2.57 g / cm³ 3 , 2.58 g / cm³ 3 , 2.60 g / cm³ 3 , 2.62 g / cm³ 3 , 2.65 g / cm³ 3 , 2.68 g / cm³ 3 , 2.70 g / cm³ 3 , 2.75 g / cm³ 3 , 2.80 g / cm³ 3 , 2.85 g / cm³ 3 or lies within any range of two of the values ​​mentioned above.

[0155] If the packing density of the positive film layer is within the aforementioned range, this contributes to increasing the energy density of the battery cell. Since the positive active material of the positive film layer is relatively densely packed, the contact resistance between the particles is low, which further reduces the resistance of the electrode plate. This reduces heat generation during fast charging, decreases gas evolution at high temperatures, and improves high-temperature cycle performance, particularly in fast-charging systems.

[0156] In some embodiments, the one-sided coating weight of the positive film layer is 250 mg / 1540.25 mm². 2 up to 300 mg / 1540.25 mm 2 For example, the one-sided coating weight of the positive film layer is 250 mg / 1540.25 mm². 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 or lies within any range of two of the values ​​mentioned above.

[0157] If the one-sided coating weight of the positive film layer is within the range mentioned above, the heat generation per unit area of ​​the positive electrode plate is not too high, and both the energy density and the charging speed of the battery cell can be improved without excessive heat accumulating in the battery cell system, thereby reducing the risk of electrolyte solution decomposition at high temperatures and improving the cycle performance of the battery cell.

[0158] In the embodiment of the present application, the density of the positive film layer of the battery cell at 0% state of charge (SOC) is known in the art, i.e., disassembling the positive electrode plate of the battery cell at 0% SOC and determining the density of the positive film layer, e.g., by taking a positive electrode plate coated with a single-sided coating (in the case of an electrode plate coated with a double-sided coating, one of the positive film layers can be wiped off first), punching and cutting the positive electrode plate into small discs with an area of ​​S1, weighing them, noting them as M1, and measuring the thickness H1. Then, after weighing, wiping off the positive film layer of the positive electrode plate, weighing the positive current collector, noting it as M0, and measuring its thickness H0.The one-sided coating weight of the positive film layer = (weight of the positive electrode plate M1 - weight of the positive current collector M0) / S1, and thickness of the positive film layer = thickness of the positive electrode plate H1 - thickness of the positive current collector H0, and the compaction density of the positive film layer = one-sided coating weight of the positive film layer / thickness of the positive film layer.

[0159] In some embodiments, the positive active material comprises one or more lithium-containing transition metal oxides, lithium phosphates, preferably lithium phosphate. Lithium phosphate can have an olivite structure that is structurally stable during charging and discharging and can improve the cycle life of the battery cell.

[0160] Examples of lithium-containing transition metal oxides include at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds.

[0161] In some embodiments, the positive film layer also includes a carbon-containing material, wherein the carbon-containing material is a carbon-containing conductive material that can improve the conductivity of the positive film layer, which contributes to improving the fast-charging capability of the battery cell.

[0162] Preferably, the mass fraction of the carbon element in the positive film layer is 0.8% to 3.5%, for example 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, or lies in any range between two of the values ​​mentioned above. Preferably, the mass fraction of the carbon element in the positive film layer is 1.3% to 3.0%.

[0163] For example, the carbon-containing material can include carbon nanotubes, which can serve as a conductive medium in the positive film layer and improve the conductivity of the positive film layer.

[0164] Another example is lithium phosphate with an olivite structure. This can be either unmodified lithium phosphate, such as lithium iron phosphate, or materials modified by coating. For instance, the surface of the lithium phosphate can be coated with a carbon-containing material. This coating improves the conductivity of the lithium phosphate, reduces the specific powder resistivity of the material, and promotes the migration rate of lithium ions, thereby improving the fast-charging capability of the battery cell and reducing heat generation.

[0165] In some embodiments, the lithium phosphate comprises a compound of the general formula Li x1 A y1 Me a M b P 1-c X c Y z, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3 and 0.9 ≤ x1+ y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5 and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5. A comprises one or more of Na, K, Mg, Me comprises one or more of Mn, Fe, Co, Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X comprises one or more of Cl, C, N, and Y comprises one or more of O, F. The lithium phosphate exhibits excellent cycle stability, which contributes to improving the cycle performance of the battery cell.

[0166] Lithium phosphate, for example, comprises one or more of the following materials: LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During charging and discharging, the battery cell undergoes the removal and consumption of active ions, such as lithium (Li), and the battery cell exhibits varying molar concentrations of Li as it discharges to different states. When listing the active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar concentration of Li represents the initial state of the material, i.e., the state before input. This molar concentration can change as the active material is introduced into the battery system after a charge and discharge cycle. The molar concentration of oxygen (O) in the active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., is also relevant., which are listed in the embodiment of the present application, is only the theoretical state value, and the release of oxygen from the crystal lattice leads to a change in the molar content of oxygen O, and in practice the molar content of oxygen O can fluctuate, and the above-mentioned situations fall within the scope of protection of the present application.

[0167] In the embodiment of the present application, the elemental content of the positive active material, as defined in the technical term, is known and can be measured using equipment and methods known in the art. For example, the measurement is carried out by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400) in accordance with EPA 6010D-2014. After discharging the battery cell to 0% state of charge (SOC) and disassembling the positive electrode plate, it was cleaned with dimethyl carbonate (DMC) and dried, and then calcined at high temperature to remove impurities. 0.4 g of the positive active material was weighed out, and 10 ml (50% concentration) of aqua regia was added. The mixture was then placed on the plate for 30 minutes at 180°C. After dissolution on the plate, the solution was fixed to a volume of 100 mL, and the quantitative test was performed using the standard curve method.

[0168] In some embodiments, the lithium phosphate is in particle form, comprising several first phosphate particles and several second phosphate particles, wherein the longest diameter of the first phosphate particles is greater than or equal to a preset longest diameter, for example 1 µm, while the longest diameter of the second phosphate particles is less than 1 µm. It can be assumed that all particles with a longest diameter greater than or equal to 1 µm belong to the first phosphate particles and all particles with a longest diameter less than 1 µm belong to the second phosphate particles.

[0169] The longest diameter of the first phosphate particle is larger than the longest diameter of the second phosphate particle; the average longest diameter of the first phosphate particle is 1 µm to 5 µm, and the average longest diameter of the second phosphate particle is 0.1 µm to 0.5 µm.

[0170] For example, the average longest diameter of the first phosphate particles is 1 µm to 5 µm, for example 1 µm, 1.5 µm, 2 µm, 2.5 µm, 3 µm, 3.5 µm, 4 µm, 4.5 µm, 5 µm, or lies in any range of two of the above values.

[0171] For example, the average longest diameter of the second phosphate particles is 0.1 µm to 0.5 µm, for example 0.1 µm, 0.15 µm, 0.2 µm, 0.25 µm, 0.3 µm, 0.35 µm, 0.4 µm, 0.45 µm, 0.5 µm or lies in any range of two of the above values.

[0172] If the lithium phosphate meets the above-mentioned conditions, its longest diameter is relatively small, the lithium debedding path in the lithium phosphate is short, and less heat is generated; furthermore, the particle size of the aforementioned lithium phosphate is not too small, so that agglomeration does not occur during processing and manufacturing, thus keeping the properties of the lithium phosphate stable; this contributes to improving the high-temperature cycle performance of the battery cell.

[0173] In some embodiments, the mass fraction of the second phosphate particles in the lithium phosphate is 80% to 95%, for example, 80%, 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, or 95%, or lies within any range between two of the aforementioned values. The mass fraction of second phosphate particles being within a suitable range, for example, between 80% and 95%, further reduces heat generation, decreases heat generation in the battery cell system, reduces the risk of electrolyte component degradation due to heat accumulation, and improves the battery cell's cycle performance.

[0174] In some embodiments, the positive film layer comprises a positive additive, wherein the positive additive includes at least one lithium-containing iron oxide and one lithium-containing cobalt oxide. During charging, the lithium ions of the positive additive migrate through the electrolyte solution to the negative electrode side. Through this migration, the positive additive forms negative electron groups that donate oxygen to the electrolyte solution. The oxygen can participate in the formation of the negative film layer, repair the SEI film, reduce the effects of carboxylic acid ester solvents on the battery cell's lifetime at high temperatures, and improve the battery cell's high-temperature cycle performance.

[0175] The positive additive includes lithium element, which releases lithium ions during the charging process of the battery cell, compensating for lithium loss and improving the capacity characteristics and cycle performance of the battery cell.

[0176] In some embodiments, the lithium-containing iron oxide comprises lithium ferrite. The lithium ferrite can, on the one hand, compensate for lithium loss in the system and, on the other hand, donate oxygen to the negative electrode, where it participates in the formation of the SEI foil and improves the cycle performance of the battery cell.

[0177] Preferably, the lithium-containing iron oxide Li e FeO f , where 0 < e ≤ 5 and 0 < f ≤ 4.

[0178] For example, the lithium-containing iron oxide comprises at least one of Li5FeO4, Li3FeO 3.5 , LiFeO2.

[0179] In some embodiments, the lithium-containing cobalt oxide comprises lithium cobaltate. The lithium cobaltate can, on the one hand, compensate for lithium loss in the system and, on the other hand, donate oxygen to the negative electrode, where it participates in the formation of the SEI foil and improves the cycle performance of the battery cell.

[0180] Preferably, the lithium-containing cobalt oxide comprises Li g CoO h , 0 < g ≤ 6, 0 < h ≤ 4.

[0181] For example, the lithium-containing cobalt oxide comprises one or more of Li6CoO4, Li3CoO2, LiCoO2.

[0182] In some embodiments, the surface of the positive additive is additionally provided with a carbon cover layer, such that the positive additive has a core-case structure, wherein the positive additive consists of a core and a carbon cover layer, the core comprising at least one of lithium ferrite particles and lithium cobaltate particles, and the carbon cover layer being applied to at least a portion of the core's surface. The positive additive includes a carbon cover layer that effectively protects the core.The positive additive coated with a carbon layer is structurally more stable and can mitigate side reactions between the electrolyte solution and the positive additive, further improving the cycle performance of the battery cell. Additionally, the carbon layer can delay oxygen release from the core, allowing oxygen to gradually be released into the electrolyte solution and progressively participate in the formation and repair of the SEI film. This promotes the formation of a high-performance SEI film and reduces its resistance. For example, the core comprises lithium ferrite particles, and the carbon layer covers the surface of these particles.

[0183] Preferably, the mass fraction of the carbon cover layer in the positive additive is 1% to 5%, for example 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, or lies in any range of two of the above values.

[0184] If the mass fraction of the carbon cover layer is within the range mentioned above, the core can be protected more effectively, which promotes the gradual release of oxygen.

[0185] In some embodiments, both the lithium phosphate and the positive additive consist of multiple particles, and the average longest diameter of the multiple lithium phosphates is smaller than the average shortest diameter of the multiple positive additives. Using the positive additive with the aforementioned particle size can effectively improve its stability while simultaneously achieving a good oxygen release effect.

[0186] In some embodiments, the ratio between the longest and shortest diameters of the positive additive within the same particle is 1.2 to 2.5, for example, 1.2, 1.4, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.5, or lies within any range of two of the aforementioned values. Using the positive additive with the particle size specified above can effectively improve its stability while simultaneously achieving a good oxygen release effect.

[0187] In some embodiments, the average longest diameter of several positive additives is 9 µm to 13 µm, for example, 9 µm, 9.5 µm, 10 µm, 10.5 µm, 11 µm, 11.5 µm, 12 µm, 12.5 µm, 13 µm, or lies within any range of two of the above values. Using the positive additive with the particle size mentioned above can effectively improve the stability of the positive additive while simultaneously achieving a good oxygen release effect.

[0188] In some embodiments, the average shortest diameter of several positive additives is 5 µm to 9 µm, for example 5 µm, 5.5 µm, 6 µm, 6.5 µm, 7 µm, 7.5 µm, 8 µm, 8.5 µm, 9 µm, or lies within any range of two of the above values. Using the positive additive with the particle size mentioned above can effectively improve the stability of the positive additive while simultaneously achieving a good oxygen release effect.

[0189] In the present embodiment, the positive electrode plate is cut along its thickness direction to expose the cut surface of the positive film layer, which can also be understood as the cross-section of the positive film layer along its thickness direction. By examining the cut surface of the positive film layer with a scanning electron microscope (SEM), the longest and shortest diameters of the positive additive particles, as well as the longest diameter of the lithium phosphate, are determined. For example, the "longest diameter" of a particle is defined as the longest straight line passing through the center of the particle and extending to its outer edge. The "shortest diameter" of a particle is the shortest straight line passing through the center of the particle and extending to its outer edge.

[0190] In the cross-section of the positive film layer along its thickness direction, the longest diameters of, for example, 10 positive additives are counted and their average value is calculated as the average longest diameter; the shortest diameters of, for example, 10 positive additives are counted and their average value is calculated as the average shortest diameter.

[0191] In a cross-section of the positive film layer along its thickness direction, the longest diameters of, for example, 50 lithium phosphate particles are counted. Particles with a longest diameter greater than or equal to 1 µm are classified as first phosphate particles. Particles with a longest diameter less than 1 µm are classified as second phosphate particles. The average of the longest diameters of all first phosphate particles is the average longest diameter of the first phosphate particles, and the average of the longest diameters of all second phosphate particles is the average longest diameter of the second phosphate particles.

[0192] In some embodiments, the mass fraction of the positive additive, based on the total mass of the positive film layer, is 0.5% to 3%, for example, 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.5%, 3.0%, or lies in any range between two of the values ​​mentioned above. Using a positive additive in the mass range mentioned above can effectively improve the stability of the positive additive while simultaneously achieving a good oxygen release effect.

[0193] In some embodiments, the positive film layer may preferably also comprise a positive conductive element. For example, the positive conductive element comprises at least one of the following: superconducting carbon, conductive graphite, acetylene carbon black, carbon black, Kochin carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofiber. In some embodiments, the mass fraction of the positive conductive element is ≤ 5% based on the mass of the positive film layer.

[0194] Preferably, the positive conductive agent comprises carbon nanotubes, wherein the mass fraction of the carbon nanotubes in the positive film layer is 0.1% to 2%, for example 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, or 2%, or lies in any range between two of the above values. Preferably, the mass fraction of the carbon nanotubes in the positive film layer is 0.15% to 1.2%.

[0195] A mass fraction of the carbon nanotube within the above-mentioned range contributes to improving the conductivity of the positive film layer and improving the fast-charging capability of the battery cell.

[0196] Preferably, the specific surface area of ​​the carbon nanotubes is 500 m². 2 / g up to 2500 m 2 / g, for example 500 m 2 / g, 700 m 2 / g, 900 m 2 / g, 1100 m 2 / g, 1300 m 2 / g, 1500 m 2 / g, 1700 m 2 / g, 1900 m 2 / g, 2100 m 2 / g, 2300 m 2 / g, 2500 m 2 / g or lies within any range of two of the values ​​mentioned above.

[0197] If the specific surface area of ​​the carbon nanotubes is within the range mentioned above, the electronic conductivity is improved; furthermore, by adding a suitable amount of carbon nanotubes, the extent of side reactions can be reduced and the cycle performance improved.

[0198] Preferably, the diameter of the carbon nanotube is 0.5 nm to 20 nm, e.g., 0.5 nm, 1.5 nm, 2.5 nm, 3.5 nm, 4.5 nm, 5.5 nm, 6.5 nm, 7.5 nm, 8.5 nm, 9.5 nm, 10.5 nm, 11.5 nm, 12.5 nm, 13.5 nm, 14.5 nm, 15.5 nm, 16.5 nm, 17.5 nm, 18.5 nm, 19.5 nm, 20 nm, or lies within any range of two of the above values. Preferably, the diameter of the carbon nanotube is 0.5 nm to 7.5 nm.

[0199] If the diameter of the carbon nanotube is within the range mentioned above, its structure is relatively stable and exhibits relatively good electronic conductivity.

[0200] Carbon nanotubes can generally be viewed as two-dimensional carbon material that coils up into a roll. If a single layer coils up, it is a single-walled carbon nanotube; if multiple layers coil up, it is a multi-walled carbon nanotube. The diameter of a carbon nanotube is the outer diameter of the carbon nanotube, measured at a cross-section perpendicular to its own central axis.

[0201] In some embodiments, the positive film layer may preferably also comprise a positive binder. The embodiment of the present application does not contain any specific restrictions regarding the type of positive binder. For example, the positive binder may comprise at least one of the following: polyvinylidene fluoride, polytetrafluoroethylene, a terpolymer of vinylidene fluoride, tetrafluoroethylene and propylene, a terpolymer of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, a copolymer of tetrafluoroethylene and hexafluoropropylene, polyacrylic acid, and a fluorinated acrylic ester resin. In some embodiments, the mass fraction of the positive binder is ≤ 5% based on the mass of the positive film layer.

[0202] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, a metal foil can be made of at least one aluminum, aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, or a silver alloy. The composite current collector can comprise a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The metal material in the metal layer can, for example, comprise at least one of the following materials: aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy. The polymer base layer can, for example, comprise at least one of the following materials: polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0203] The positive electrode layer is typically formed by applying the positive electrode slurry to the positive current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing the positive active material, an optional conductive agent, an optional binder, and all other components in a solvent and mixing thoroughly. The solvent may include, but is not limited to, N-methylpyrrolidone (NMP).

[0204] The positive electrode plate does not preclude additional functional layers besides the positive film layer. In some embodiments, the positive electrode plate of the present application, for example, further comprises a positive conductive layer located between the positive current collector and the positive film layer and provided on the surface of the positive current collector. In further embodiments, the positive electrode plate of the present application additionally comprises a protective layer covering the surface of the positive film layer. electrolyte solution

[0205] During the charging and discharging of the battery cell, active ions, such as lithium ions, are embedded between and released from the positive and negative electrode plates, and the electrolyte solution acts as a conductor for these active ions. The electrolyte solution comprises organic solvents and electrolyte salts.

[0206] In some embodiments, the electrolyte solution has a conductivity at room temperature of 9 mS / cm to 18 mS / cm. For example, the conductivity of the electrolyte solution at room temperature is 9 mS / cm, 9.5 mS / cm, 10 mS / cm, 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, or lies in any range between two of the above values.

[0207] If the conductivity of the electrolyte solution at room temperature, e.g., 25 °C, is within the range mentioned above, the lithium ions migrate at a higher rate within the electrolyte solution, which can further reduce the internal resistance of the battery cell. This leads to a reduction in heat generation and the high gas production caused by heat accumulation at high temperatures, thereby improving the high-temperature cycle performance of the battery cell during fast charging.

[0208] In the embodiments of the present application, the conductivity of the electrolyte solution at room temperature, e.g. 25 °C, is the ionic conductivity, which can be tested using equipment and methods known in the art, e.g. with reference to the industry standard HG-T 4067-2015.

[0209] In some embodiments, the organic solvent comprises carboxylic acid ester solvents.

[0210] Preferably, the mass fraction of the carboxylic acid ester solvent in the electrolyte solution is 3% to 70%. For example, the mass fraction of the carboxylic acid ester solvent is 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, or lies in any range between two of the above values. Preferably, the mass fraction of the carboxylic acid ester solvent in the electrolyte solution is 5% to 30%.

[0211] If the mass fraction of the carboxylic acid ester solvent is within the range mentioned above, the conductivity of the electrolyte solution can be increased; furthermore, the electrolyte solution is compatible with the silicon-containing negative electrode, which effectively mitigates side reactions on the negative electrode, reduces gas evolution from the battery cell, and improves the fast-charging capability of the battery cell.

[0212] For example, the carboxylic acid ester solvent comprises cyclic carboxylic acid esters, wherein the cyclic carboxylic acid ester includes one or more of γ-butyrolactone, γ-pentyrolactone, and δ-pentyrolactone. The aforementioned material exhibits high conductivity and can improve the conductivity of the electrolyte solution.

[0213] For example, the carboxylic acid ester solvent comprises chain carboxylic acid esters, where the chain carboxylic acid ester includes one or more of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propionyl propyl ester, and propionyl butyl ester. The aforementioned material exhibits high conductivity and can improve the conductivity of the electrolyte solution.

[0214] In some embodiments, the organic solvent comprises carbonate solvents.

[0215] The combined use of carbonate solvents and carboxylic acid ester solvents can increase the stability of the electrolyte solution and reduce its high-temperature gas production, which contributes to improving the lifespan of the battery cell at high temperatures.

[0216] For example, the carbonate solvent comprises one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methylethyl carbonate. Preferably, the carbonate solvent comprises one or more of vinyl carbonate, dimethyl carbonate, and methylethyl carbonate.

[0217] In some embodiments, the electrolyte salt comprises a lithium salt, wherein the lithium salt comprises one or more of lithium bifluorosulfonamide and lithium hexafluorophosphate. Preferably, the lithium salt comprises lithium bifluorosulfonamide and lithium hexafluorophosphate.

[0218] Lithium hexafluorophosphate can decompose and form hydrofluoric acid (HF). The side reaction between hydrofluoric acid and the negative electrode, especially a silicon-containing negative electrode, can lead to increased gas evolution during storage at high temperatures. The combined use of lithium hexafluorophosphate and lithium bifluorosulfonamide can reduce the hydrofluoric acid content, slow down side reactions at the negative electrode interface, reduce gas evolution during storage at high temperatures, and thus improve the battery cell's lifetime at high temperatures.

[0219] In some embodiments, the ratio between the mass fraction of lithium bifluorosulfonamide and the mass fraction of lithium hexafluorophosphate, based on the mass of the electrolyte solution, is 0.3 to 1.2, for example 0.3, 0.5, 0.7, 0.9, 1.1, 1.2 or lies in any range of two of the above values.

[0220] If the ratio between the mass fraction of lithium hexafluorophosphate and lithium bifluorosulfonamide is within the aforementioned range, the hydrofluoric acid content can be reduced, the side reaction at the interface of the negative electrode can be reduced, and gas evolution during storage at high temperatures can be reduced; on the other hand, a suitable content of organic components in the SEI film formed at the interface of the negative electrode can also reduce gas evolution during storage at high temperatures, which contributes to extending the service life of the battery cell at high temperatures.

[0221] For example, the mass fraction of lithium bifluorosulfonamide, based on the mass of the electrolyte solution, is 2% to 11%, e.g., 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, or lies within any range of two of the above values. If the mass fraction of lithium bifluorosulfonamide is within the above range, the hydrofluoric acid content can be reduced, the side reaction at the negative electrode interface can be decreased, and gas evolution during storage at high temperatures can be reduced, thus contributing to an improved high-temperature lifespan of the battery cell.

[0222] For example, the mass fraction of lithium hexafluorophosphate, based on the mass of the electrolyte solution, is 3% to 14%, such as 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, or lies within any range of two of the above values. When the mass fraction of lithium hexafluorophosphate is within the above range, the conductivity of the electrolyte solution is relatively high, which promotes the migration of lithium ions and improves the fast-charging capability of the battery cell.

[0223] In some embodiments, the electrolyte solution also includes additives, which may include additives for forming a negative film layer, additives for forming a positive film layer, or additives for improving certain properties of the battery, for example, additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature performance of the battery, etc.

[0224] In some embodiments, the additives comprise cyclic carbonate ester additives, for example one or more of fluorinated cyclic carbonates and vinylidene carbonates; preferably, the additives comprise fluorinated cyclic carbonates and vinylidene carbonate.

[0225] Fluorinated cyclic carbonates can form a lithium fluoride (LiF)-enriched SEI film on the surface of the negative electrode, which mitigates the volume expansion of silicon, improves the lifetime of silicon-containing systems, and enhances cycle performance.

[0226] The combined use of fluorinated cyclic carbonates and vinylidene carbonate results in a denser SEI film on the surface of the negative electrode, thereby protecting the silicon-containing negative electrode more effectively, reducing side reactions at the interface of the negative electrode, and improving cycle performance.

[0227] Preferably, the fluorinated cyclic carbonate comprises at least one of ethylene fluorocarbonate, ethylene difluorocarbonate and trifluoropropylene carbonate.

[0228] Preferably, the mass fraction of the fluorinated cyclic carbonate, based on the mass of the electrolyte solution, is 0.5% to 20%, for example 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or lies in any range of two of the above values. If the mass fraction of the fluorinated cyclic carbonate is within the range mentioned above, this improves cycle performance.

[0229] For example, the mass fraction of the fluorinated cyclic carbonate, based on the mass of the electrolyte solution, is 0.5% to 10%; the mass fraction of the silicon element of the silicon-based material in the negative active material is 0.3% to 7.5%.

[0230] The mass fraction of the silicon element is relatively high, and its volume expansion is relatively large. If the mass fraction of the fluorinated cyclic carbonate and the mass fraction of the silicon element meet the conditions mentioned above, the volume expansion of the silicon can be mitigated more effectively, thus improving the lifetime of the silicon-containing system and enhancing its cycle performance.

[0231] As another example, the mass fraction of the fluorinated cyclic carbonate, based on the mass of the electrolyte solution, is more than 10% and less than or equal to 20%. The mass fraction of the silicon element of the silicon-based material in the negative active material is more than 7.5% and less than or equal to 15%.

[0232] If the mass fraction of the fluorinated cyclic carbonate and the mass fraction of the silicon element meet the above conditions, the volume expansion of the silicon can be more effectively mitigated, which improves the lifetime of the silicon-containing system and enhances cycle performance.

[0233] Preferably, the mass fraction of vinylidene carbonate, based on the mass of the electrolyte solution, is 0.1% to 3%, for example, 0.1%, 0.5%, 0.6%, 1.0%, 1.1%, 1.5%, 1.6%, 2.0%, 2.1%, 2.5%, 2.6%, 3%, or lies in any range between two of the above values. The aforementioned mass fraction of vinylidene carbonate results in a denser SEI film on the surface of the negative electrode, thereby more effectively protecting the silicon-containing negative electrode, reducing side reactions at the negative electrode interface, and improving cycle performance.

[0234] The combined use of the above-mentioned mass fraction of vinylidene carbonate and fluorinated cyclic carbonate further optimizes the properties of the SEI film on the surface of the negative electrode, ensures excellent density and low resistance, protects the silicon-containing negative electrode more effectively, reduces the extent of side reactions at the interface of the negative electrode and improves cycle performance.

[0235] In the embodiment of the present application, the types and concentrations of the inorganic components / lithium salts in the electrolyte solution have a meaning generally known in this field and can be measured using equipment and methods generally known in this field; for example, with reference to the standard JY / T020-1996 "General rules for ion chromatography analysis", a qualitative or quantitative analysis of the inorganic components / lithium salts in the electrolyte solution can be carried out by means of ion chromatography analysis.In the embodiment of the present application, newly produced electrolyte solution can be taken as a sample, free electrolyte solution can be taken from a new battery as a sample, or a completely discharged battery (which has been discharged to the lower limit voltage, so that the state of charge of the battery is approximately 0% SOC) can be reverse disassembled to take free electrolyte solution from the battery as a sample, which is analyzed by ion chromatography.

[0236] In the embodiment of the present application, the types and concentrations of the organic components in the electrolyte solution have a meaning generally known in this field and can be measured using equipment and methods generally known in this field; for example, with reference to GB / T9722-2006 “Chemical reagents - General rules for gas chromatography”, a qualitative and quantitative analysis of the organic components in the electrolyte solution can be carried out by means of gas chromatography.

[0237] In the embodiment of the present application, the individual components in the electrolyte solution are quantitatively and qualitatively examined and subsequently classified, wherein carboxylic acid ester solvents and carbonate solvents are classified as components of organic solvents and the mass fraction of the individual components is calculated as 100% based on the mass of the electrolyte solution.

[0238] The fluorinated cyclic carbonate and vinylidene carbonate are used as additives to the electrolyte solution, with the mass fraction of each component calculated as 100% relative to the mass of the electrolyte solution. Separating element

[0239] In some embodiments, the electrode assembly also includes a separating element that is arranged between the positive electrode plate and the negative electrode plate.

[0240] In some embodiments, the separating element is a separating film. The present application contains no specific restrictions regarding the type of separating film; any known porous separating film with good chemical and mechanical stability can be used.

[0241] For example, the main material of the separating film can be selected from at least one of the following materials: fiberglass, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separating film can be a single-layer film or a multi-layer composite film, without any particular restrictions. If the separating film is a multi-layer composite film, the materials of the individual layers can be the same or different, without any particular restrictions. The separating element can be a single component located between the positive and negative electrodes, or it can be attached to the surface of the positive and negative electrodes. A coating of inorganic particles, organic particles, or an organic-inorganic composite coating can also be applied to the surface of the separating film.

[0242] In some embodiments, the separating element is a solid electrolyte. The solid electrolyte is located between the positive and negative electrodes and serves simultaneously to transfer ions and to separate the positive and negative electrodes. Example of implementation

[0243] The following embodiments describe in more detail what is disclosed by the embodiments of the present application, and these embodiments serve only for illustration, since various modifications and variations within the scope of disclosure of the embodiments of the present application are obvious to the person skilled in the art. Unless otherwise stated, all parts, percentages, and ratios given in the following embodiments are based on mass counts, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the equipment used in the embodiments is commercially available. Example 11. Production of a positive electrode plate

[0244] The positive electrode plate comprises a positive current collector and a positive film layer provided on both sides of the positive current collector, wherein the positive current collector is an aluminum foil.

[0245] The positive film layer contains lithium phosphate, positive additive, binder polyvinylidene fluoride (PVDF) and conductive agent acetylene carbon black in a mass ratio of 96:1.5:1.5:1, and the positive film layer is a film layer formed by uniformly coating both sides of the positive current collector with a positive electrode slurry (whose solvent is N-methylpyrrolidone NMP) and subsequent drying and cold pressing.

[0246] The lithium phosphate comprises several first phosphate particles and several second phosphate particles, with the mass fraction of the second phosphate particles in the lithium phosphate being 90%;

[0247] In cross-section along the thickness direction of the positive film layer, the average longest diameter of the first phosphate particles is 2 µm and the average longest diameter of the second phosphate particles is 0.3 µm, with the mass fraction of the second phosphate particles in the lithium phosphate being 90%.

[0248] The positive additive consists of several particles, each comprising a core and a carbon cover layer arranged on the surface of the core. The core is made of lithium ferrite, and the carbon cover layer constitutes 2% of the mass fraction of the positive additive. In cross-section along the thickness direction of the positive film layer, the average longest diameter of the several positive additives is 11 µm, and the average shortest diameter of the several positive additives is 7 µm.

[0249] The one-sided coating weight of the positive film layer is 280 mg / 1540.25 mm². 2 .

[0250] The lithium iron phosphate comes from XIAMEN TUNGSTEN CO., LTD. 2. Production of the negative electrode plate

[0251] The negative electrode plate comprises a negative current collector and a negative film layer provided on both sides of the negative current collector, and the negative current collector is a copper foil.

[0252] The negative film layer consists of a carbon-based material such as synthetic graphite, the conductive agent acetylene carbon black, the binder for the negative electrode made of styrene-butadiene rubber, and the thickening agent sodium carboxymethylcellulose in a mass ratio of 96.5:1:1.5:1. The negative film layer is formed by uniformly applying the negative electrode slurry (the solvent is deionized water) to the surface of the negative current collector, drying, and cold pressing.

[0253] The one-sided coating weight of the negative film layer is 135 mg / 1540.25 mm². 2 .

[0254] The synthetic graphite comes from BTR New Material Group Co., Ltd. 3. Separating film

[0255] The separating film consists of a base film, a 7 µm thick polyethylene membrane layer with a porosity of 35%.

[0256] The separating film is from Shenzhen Senior Technology Material Co., Ltd. 4. Preparation of the electrolyte solution

[0257] The electrolyte solution consists of organic solvents, lithium salts and additives.

[0258] After the individual components of the organic solvent have been mixed uniformly, lithium salts and additives are added to produce the electrolyte solution.

[0259] The organic solvents comprise 25% chain carboxylic acid ester solvent (ethyl acetate EA) and 57% carbonate solvent (27% vinyl carbonate EC, 30% dimethyl carbonate DMC). The mass fraction of the individual components in the organic solvents is calculated based on the mass of the electrolyte solution.

[0260] The lithium salt comprises 8% lithium hexafluorophosphate LiPF6 and 6% lithium bifluorosulfonamide.

[0261] The additives include 2% fluorinated cyclic carbonate, ethylene fluorocarbonate (FEC), and 2% vinylidene carbonate (VC);

[0262] The conductivity of the electrolyte solution is 14.2 mS / cm. 5. Manufacturing the battery cell

[0263] The positive electrode plate, separating film, and negative electrode plate mentioned above are stacked sequentially so that the separating film lies between the positive and negative electrode plates, providing separation. This creates the electrode assembly, which is then placed in the housing. After drying, the electrolyte solution is added. Following vacuum packaging, decommissioning, molding, and shaping, the battery cell is produced. The density of the positive film layer of the battery cell is 2.65 g / cm³ at 0% SOC. 3 The compaction density of the negative film layer is 1.56 g / cm³ at 0% SOC. 3 . Comparison example 1-1

[0264] The battery cell was manufactured using a similar process to that in embodiment 1, however, unlike embodiment 1, no positive additive was added to the positive film layer. Example 2

[0265] The battery cell was manufactured using a similar method to that in embodiment 1, however, in contrast to embodiment 1, the type of positive additive was adapted. Exemplary embodiment 3-1 and Exemplary embodiment 3-2

[0266] The battery cell was manufactured using a similar process to that in embodiment 1, however, in contrast to embodiment 1, the mass fraction of the carbon cover layer in the positive additive was adjusted. Exemplary embodiment 4-1 and Exemplary embodiment 4-2

[0267] The battery cell was manufactured using a similar method to that in embodiment 1, however, in contrast to embodiment 1, the mass fraction of the positive additive was adjusted. Exemplary embodiments 5-1 to 5-3

[0268] The battery cell was manufactured using a similar process to that in embodiment 1, however, in contrast to embodiment 1, the particle size of the positive additive was adjusted. Exemplary embodiments 6-1 to 6-3

[0269] The battery cell was manufactured using a similar method to that in embodiment 1, however, in contrast to embodiment 1, the particle size of the positive active material was adjusted. Exemplary embodiment 7-1 and exemplary embodiment 7-2

[0270] The battery cell was manufactured using a similar method to that in embodiment 1, however, in contrast to embodiment 1, the mass fraction of the second phosphate particles of the positive active material was adjusted. Performance test 1. High-temperature cycle performance test of the battery cell

[0271] At an ambient temperature of 45 ± 5 °C, the battery cell is charged to 3.65 V with a constant current of 2C, then charged to a cutoff current of 0.05C with a constant voltage, and subsequently discharged to 2.5 V with a constant current of 2C. This constitutes one charge and discharge cycle. The discharge capacity is recorded as the discharge capacity C1 of the first cycle of the battery cell.

[0272] The cycle is repeated for the same battery cell until the battery cell's cycle capacity retention rate = Cn / C1*100% = 80%. The number of cycles n is recorded. For accuracy, the average value of 5 parallel samples is used as the test result.

[0273] The test results are listed in Table 1.

[0274] The organic components of the electrolyte solution can cause side reactions at the negative electrode and impair the high-temperature cycle. In comparative example 1-1, no positive additives were added, resulting in relatively poor high-temperature cycle performance.

[0275] In the embodiment of the present application, however, positive additives are added to the positive film layer, wherein the positive additives release the oxygen involved in the formation of the negative film layer, repair the SEI film on the negative electrode, reduce side reactions on the negative electrode and improve the high-temperature cycle performance.

[0276] Positive additives made from various materials, such as lithium ferrite, lithium cobaltate, etc., can release oxygen during the charging process of the battery cell, repair the negative interfacial film, and improve high-temperature cycle performance.

[0277] The surface of lithium ferrite can be coated with a carbon layer, the mass fraction of which in the positive additive is 1% to 5%. The carbon layer effectively protects the lithium ferrite, mitigates side reactions between the lithium ferrite and the electrolyte solution, enables stable oxygen release from the lithium ferrite, gradually repairs the SEI film, and improves the high-temperature cycle performance of the battery cell.

[0278] The longest and shortest diameters of the positive additive within the same particle must be in a suitable ratio. For example, if the ratio between the longest and shortest diameters is between 1.2 and 2.5, the stability of the positive additive is effectively improved while simultaneously achieving good oxygen release.

[0279] The average longest diameter of the lithium phosphate is smaller than the average shortest diameter of the positive additive. Using the positive additive with the particle size mentioned above results in good oxygen release and improves the high-temperature cycle performance of the battery cell.

[0280] The lithium phosphate comprises multiple first phosphate particles and multiple second phosphate particles. The longest diameter of the first phosphate particles is relatively long, while the longest diameter of the second phosphate particles is relatively short. However, the average longest diameter of the first phosphate particles is still shorter than the average shortest diameter of the positive additives, resulting in a shorter lithium debedding path in the lithium phosphate and less heat generation. This reduces heat generation in the battery cell system, decreases the risk of electrolyte component degradation due to heat accumulation, and improves the battery cell's cycle performance.

[0281] The mass fraction of second phosphate particles is in a suitable range, for example between 80% and 95%, which further reduces heat generation, decreases the heat generation in the battery cell system, reduces the risk of decomposition of the electrolyte components due to heat accumulation, and improves the cycle performance of the battery cell. Comparative example 2-1 and 2-2

[0282] The battery cell was manufactured using a similar method to that in embodiment 1, however, in contrast to embodiment 1, the composition and content of the electrolyte solution were adjusted. Exemplary embodiments 8-1 to 8-7

[0283] The battery cell was manufactured using a similar method to that in embodiment 1, however, in contrast to embodiment 1, the composition and content of the electrolyte solution were adjusted.

[0284] The test results are listed in Table 2.

[0285] In Table 2, EA stands for ethyl acetate; MA stands for methyl acetate; EC stands for vinyl carbonate; DMC stands for dimethyl carbonate; EMC stands for methyl ethyl carbonate; FEC stands for ethylene fluorocarbonate; EA: 25 means that the mass fraction of EA is 25%; EC: 27 means that the mass fraction of EC is 27%.

[0286] The mass ratio of lithium bifluorosulfonamide / lithium hexafluorophosphate refers to the ratio between the mass fraction of lithium bifluorosulfonamide and the mass fraction of lithium hexafluorophosphate.

[0287] The meaning of the other examples corresponds to the explanation above and will not be explained again here.

[0288] The conductivity of the electrolyte solution in embodiment 8-1 is 9 mS / cm, the conductivity of the electrolyte solution in embodiment 8-2 is 18 mS / cm.

[0289] In comparative example 2-1, the mass fraction of the carboxylic acid ester solvent is too low, resulting in too low conductivity of the electrolyte solution, high internal resistance of the battery cell, resulting in significant energy loss and reduced cycle life.

[0290] In comparative example 2-2, the mass fraction of the carboxylic acid ester solvent is too high, which leads to increased gas production of the carboxylic acid ester solvent at high temperatures on the negative electrode and degrades the high-temperature cycle performance.

[0291] In the embodiment of the present application, the mass fraction of the carboxylic acid ester solvent is adjusted to 3% to 70%, preferably to 5% to 30%, by regulating the individual components of the electrolyte solution, thereby increasing the conductivity of the electrolyte solution and simultaneously reducing gas production at high temperatures on the negative electrode, which leads to an improvement in cycle performance and fast charging capability.

[0292] In the embodiment of the present application, a mixture of lithium hexafluorophosphate and lithium bifluorosulfonamide is used, wherein, for example, the ratio of the mass fraction of lithium bifluorosulfonamide to lithium hexafluorophosphate is 0.3 to 1.2, thereby reducing the hydrofluoric acid content, reducing side reactions at the interface of the negative electrode, and reducing gas evolution during storage at high temperatures, which contributes to improving the lifetime of the battery cell at high temperatures.

[0293] The mass fraction of the fluorinated cyclic carbonate ranges from 0.5% to 20%. Fluorinated cyclic carbonates can form a lithium fluoride (LiF)-enriched SEI film on the surface of the negative electrode, which mitigates the volume expansion of silicon, improves the lifetime of silicon-containing systems, and enhances cycle performance.

[0294] Although illustrative embodiments have been shown and described, it should be clear to a person skilled in the art that the above-mentioned embodiments are not to be understood as limiting the embodiments of this application and that the embodiments can be changed, replaced and modified without departing from the spirit, principles and scope of the embodiments of this application. REFERENCE MARK LIST X Thickness direction 1 Electrical appliance 2 battery packs 3 Control 4 engine 5 boxes 5a First box section 5b Second part of the box 5c Recording Room 6 battery module 7 battery cells 10 Electrode assembly 11 Positive electrode plate 12 Negative electrode plate 121 Negative film layer 122 Negative current collector 1211 First negative film layer 1212 Second negative film layer 121a First area 121b Second Section 121c Third Area 13 Separating element 20 Housing assembly 21 cases 22 End cover 23 Electrode connection QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] JIS / K0131-1996

[0104] Standard JY / T020-1996 “General rules for ion chromatography analysis

[0235]

Claims

[1] Battery cell, comprising: negative electrode plates comprising a negative current collector and a negative film layer arranged on at least one side of the negative current collector, wherein the negative film layer comprises negative active material, the negative active material comprising carbon-based material; positive electrode plates comprising a positive current collector and a positive film layer arranged on at least one side of the positive current collector, the positive film layer comprising positive active material and positive additive, the positive active material comprising lithium phosphate and the positive additive comprising at least one of lithium-containing iron oxide and lithium-containing cobalt oxide; and an electrolyte solution comprising an organic solvent, wherein the organic solvent comprises a carboxylic acid ester solvent, the mass fraction of the carboxylic acid ester solvent in the electrolyte solution being 3% to 70%. [2] Battery cell according to claim 1, characterized by , that the lithium-containing iron oxide comprises lithium ferrite; and / or that the lithium-containing cobalt oxide comprises lithium cobaltate. [3] Battery cell according to claim 1 or 2, characterized by that the lithium-containing iron oxide Li e FeO f includes, where 0 < e ≤ 5 and 0 < f ≤ 4. [4] Battery cell according to claim 3, characterized by that the lithium-containing iron oxide contains at least one of Li5FeO4, Li3FeO 3.5 , LiFeO2 includes. [5] Battery cell according to any one of claims 1 to 4, characterized by that the lithium-containing cobalt oxide Li g CoO h includes, where 0 < g ≤ 6 and 0 < h ≤ 4. [6] Battery cell according to claim 5, characterized by that the lithium-containing cobalt oxide comprises one or more of Li6CoO4, Li3CoO2, LiCoO2. [7] Battery cell according to any one of claims 1 to 6, characterized by , that the mass fraction of the positive additive, relative to the mass of the positive film layer, is 0.5% to 3%. [8] Battery cell according to any one of claims 1 to 7, characterized by that the surface of the positive additive is additionally provided with a carbon top layer. [9] Battery cell according to claim 8, characterized by that the mass fraction of the carbon cover layer in the positive additive is 1% to 5%. [10] Battery cell according to any one of claims 1 to 9, characterized by, that the positive additive is in particle form and is provided in a cross-section of the positive film layer along its thickness direction, wherein the ratio between the longest and the shortest diameter of the positive additive in a particle is 1.2 to 2.

5. [11] Battery cell according to any one of claims 1 to 10, characterized by , that Several positive additives are present in the cross-section of the positive film layer along its thickness direction, with the average longest diameter of the several positive additives being 9 µm to 13 µm; and / or Several positive additives are present in the cross-section of the positive film layer along its thickness direction, with the average shortest diameter of the several positive additives being 5 µm to 9 µm. [12] Battery cell according to any one of claims 1 to 11, characterized by, that both the lithium phosphate and the positive additive are present in the form of multiple particles, wherein the average longest diameter of the multiple lithium phosphates in a cross-section of the positive film layer along its thickness direction is smaller than the average shortest diameter of the multiple positive additives. [13] Battery cell according to any one of claims 1 to 12, characterized by , that the lithium phosphate comprises several first phosphate particles and several second phosphate particles, wherein the longest diameter of the first phosphate particles is larger than the longest diameter of the second phosphate particles, the average longest diameter of the several first phosphate particles is 1 µm to 5 µm, and the average longest diameter of the several second phosphate particles is 0.1 µm to 0.5 µm. [14] Battery cell according to claim 13, characterized bythat the mass fraction of the second phosphate particles in the lithium phosphate is 80% to 95%. [15] Battery cell according to any one of claims 1 to 14, characterized by , that lithium phosphate includes lithium iron phosphate. [16] Battery cell according to any one of claims 1 to 15, characterized by , that the electrical conductivity of the electrolyte solution at room temperature is 9 mS / cm to 18 mS / cm. [17] Battery cell according to any one of claims 1 to 16, characterized by that the mass fraction of the carboxylic acid ester solvent in the electrolyte solution is 5% to 30%. [18] Battery cell according to claim 17, characterized by, that the carboxylic acid ester solvent comprises cyclic carboxylic acid esters, wherein the cyclic carboxylic acid ester comprises one or more of γ-butyrolactone, γ-pentyrolactone and δ-pentyrolactone; and / or the carboxylic acid ester solvent comprises chain carboxylic acid esters, wherein the chain carboxylic acid ester comprises one or more of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propionyl propyl ester and propionyl butyl ester. [19] Battery cell according to any one of claims 1 to 18, characterized by , that the organic solvent further comprises carbonate solvents, wherein the carbonate solvent comprises one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate. [20] Battery cell according to any one of claims 1 to 19, characterized by, that the electrolyte solution further comprises lithium salt, wherein the lithium salt comprises lithium bifluorosulfonamide and lithium hexafluorophosphate, wherein the ratio of the mass fraction of lithium bifluorosulfonamide to the mass fraction of lithium hexafluorophosphate, based on the mass of the electrolyte solution, is 0.3 to 1.

2. [21] Battery cell according to claim 20, characterized by , that the mass fraction of lithium bifluorosulfonamide, based on the mass of the electrolyte solution, is 2% to 11%; and / or the mass fraction of lithium hexafluorophosphate, based on the mass of the electrolyte solution, is 3% to 14%. [22] Battery cell according to any one of claims 1 to 21, characterized by that the electrolyte solution further comprises one or more of fluorinated cyclic carbonates and vinylidene carbonate. [23] Battery cell according to claim 22, characterized bythat the fluorinated carbonate comprises at least one of ethylene fluorocarbonate, ethylene difluorocarbonate and trifluoropropylene carbonate. [24] Battery cell according to claim 22 or 23, characterized by , that the mass fraction of the fluorinated cyclic carbonate, based on the mass of the electrolyte solution, is 0.5% to 20%; and / or The mass fraction of vinylidene carbonate, based on the mass of the electrolyte solution, is 0.1% to 3%. [25] Battery cell according to any one of claims 1 to 24, characterized by that the carbon-based material includes at least one made of synthetic graphite and one made of natural graphite. [26] Battery device, characterized by that it comprises a battery cell according to any one of claims 1 to 25. [27] Electrical appliance, characterized by that it comprises a battery device according to claim 26.

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