Lithium ion battery and electric device

Abstract

The invention discloses a lithium ion battery and an electric device and belongs to the technical field of batteries. The lithium ion battery comprises a battery monomer, the battery monomer comprises an electrolyte and a positive pole piece, the positive pole piece comprises a positive active material, the electrolyte comprises LiFSI, based on the total mass of the electrolyte, the mass content A of the LiFSI meets the condition that 1 wt% < = A < = 20 wt%, and the positive active material comprises lithium-containing phosphate; the distance piece is arranged between the first walls of two adjacent battery monomers, the first walls are the walls with the largest surface areas of the battery monomers, and the thickness t of the distance piece is 0.2 mmlt; t < = 8mm. The lithium ion battery provided by the invention has the advantages of fast charging performance, long cycle life at high temperature and high reliability.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and more specifically, to a lithium-ion battery and an electrical device. Background Art

[0002] In the new energy industry, battery technology is an important factor related to its development.

[0003] The development of battery technology needs to consider various design factors, such as energy density, cycle life, capacity, fast charging performance, reliability, etc. How to provide a lithium-ion battery with fast charging performance, long cycle life at high temperatures, and high reliability is a technical problem to be solved urgently. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to provide a lithium-ion battery with fast charging performance, long cycle life at high temperatures, and high reliability.

[0005] To achieve the above object, the present application provides a lithium-ion battery and an electrical device.

[0006] In a first aspect, a lithium-ion battery is provided, including: a battery cell, the battery cell including an electrolyte and a positive electrode plate, the positive electrode plate including a positive electrode active material, the electrolyte including LiFSI, based on the total mass of the electrolyte, the mass content A of LiFSI satisfies: 1 wt% ≤ A ≤ 20 wt%, the positive electrode active material including a lithium-containing phosphate; a spacer, the spacer being disposed between the first walls of two adjacent battery cells, the first wall being the wall with the largest surface area of the battery cell, the thickness t of the spacer satisfying: 0.2 mm < t ≤ 8 mm.

[0007] In an embodiment of the present application, the electrolyte includes LiFSI, and based on the total mass of the electrolyte, the mass content A of LiFSI satisfies: 1 wt% ≤ A ≤ 20 wt%, so that the battery cell has good fast charging performance and long cycle life at high temperatures; the positive electrode active material includes a lithium-containing phosphate, and a spacer is disposed between the first walls with the largest surface area of adjacent battery cells, the thickness t of the spacer satisfying: 0.2 mm < t ≤ 8 mm, so that the spacer with the above thickness can inhibit heat transfer between adjacent battery cells, which is beneficial to reducing the risk of thermal diffusion inside the lithium-ion battery caused by thermal runaway of the battery cell.

[0008] In some embodiments, 0.5mm≤t≤5mm. When t≥0.5mm, the heat transfer between adjacent battery cells can be suppressed, reducing the risk of heat diffusion inside the lithium-ion battery during thermal runaway; when t≤5mm, the spacer occupies a suitable space, the lithium-ion battery has a suitable space utilization rate, and the lithium-ion battery cell has a higher energy density. Through the above arrangement, the lithium-ion battery has higher reliability and higher energy density.

[0009] In some embodiments, 1.5wt%≤A≤5wt%, 0.5mm≤t≤3mm. When the mass content A of LiFSI satisfies 1.5wt%≤A≤5wt%, the thickness t of the spacer is set to satisfy 0.5mm≤t≤3mm, and the lithium-ion battery can have fast charging performance, long cycle life at high temperature, high reliability and suitable energy density.

[0010] In some embodiments, 5wt%≤A≤16wt%, 1mm≤t≤5mm. When the mass content A of LiFSI satisfies 5wt%≤A≤16wt%, the thickness t of the spacer is set to satisfy 1mm≤t≤5mm, and the lithium-ion battery can have fast charging performance, long cycle life at high temperature, high reliability and suitable energy density.

[0011] In some embodiments, the capacity Q of the battery cell satisfies: 50Ah≤Q≤300Ah.

[0012] In some embodiments, 50Ah≤Q≤130Ah, 0.5mm≤t≤1mm. In this way, when the capacity Q of the battery cell and the thickness t of the spacer meet the above ranges, the risk of heat diffusion inside the lithium-ion battery during thermal runaway is low, and the lithium-ion battery has higher reliability and higher energy density.

[0013] In some embodiments, 130Ah≤Q≤300Ah, 1mm≤t≤5mm. In this way, when the capacity Q of the battery cell and the thickness t of the spacer meet the above ranges, the risk of heat diffusion inside the lithium-ion battery during thermal runaway is low, and the lithium-ion battery has higher reliability.

[0014] In some embodiments, 1.5wt%≤A≤5wt%, 130Ah≤Q≤300Ah, 1mm≤t≤3.5mm. In this way, the lithium-ion battery has higher capacity, better fast charging performance and cycle performance, higher reliability and higher energy density.

[0015] In some embodiments, 5wt%≤A≤16wt%, 130Ah≤Q≤300Ah, 1.5mm≤t≤5mm. In this way, the lithium-ion battery has higher capacity, better fast charging performance and cycle performance, and higher reliability.

[0016] In some embodiments, the electrolyte further comprises a carboxylate solvent, and based on the total mass of the electrolyte, the mass content W0 of the carboxylate solvent satisfies: 1wt%≤W0≤80wt%. In this way, the carboxylate solvent has higher ionic conductivity and lower viscosity, which is beneficial to the transmission and diffusion of lithium ions, and the battery monomer has higher fast charging performance.

[0017] In some embodiments, the carboxylic acid ester solvent includes ethyl acetate, and based on the total mass of the electrolyte, the mass content W1 of the ethyl acetate satisfies: 15wt%≤W1≤80wt%, and the thickness t of the spacer satisfies: 1mm≤t≤5mm. In this way, the battery cell has a more suitable fast charging performance, and when a battery cell has thermal runaway, the spacer can suppress the heat of the thermal runaway battery cell from diffusing to the adjacent battery cell, which is conducive to improving the reliability of the lithium-ion battery.

[0018] In some embodiments, 15wt%≤W1≤50wt%, 1mm≤t≤3mm. In this way, the battery cell has a more suitable fast charging performance, and the lithium-ion battery can have both higher reliability and higher energy density.

[0019] In some embodiments, the carboxylic acid ester solvent includes methyl acetate, and based on the total mass of the electrolyte, the mass content W2 of the methyl acetate satisfies: 7wt%≤W2≤60wt%, and the thickness t of the spacer satisfies: 1.5mm≤t≤5mm. In this way, the battery cell has a higher fast charging performance, and when a battery cell has thermal runaway, the spacer can suppress the heat of the thermal runaway battery cell from diffusing to the adjacent battery cell, which is beneficial to improving the reliability of the lithium-ion battery.

[0020] In some embodiments, 10wt%≤W2≤40wt%, 1.5mm≤t≤3mm. In this way, the battery cell has a more suitable fast charging performance, and the lithium-ion battery can have both higher reliability and higher energy density.

[0021] In some embodiments, the carboxylic acid ester solvent includes ethyl acetate and methyl acetate. Based on the total mass of the electrolyte, the mass content W1 of the ethyl acetate satisfies: 25wt%≤A≤50wt%, the mass content W2 of the methyl acetate satisfies: 15wt%≤W2≤30wt%, and the thickness t of the spacer satisfies: 1.8mm≤t≤3mm. In this way, the battery cell has a higher fast charging performance, and when a battery cell has thermal runaway, the spacer can suppress the heat of the thermal runaway battery cell from diffusing to the adjacent battery cell, which is beneficial to improve the reliability of the lithium-ion battery.

[0022] In some embodiments, the ionic conductivity of the carboxylate solvent is 9 mS / cm to 25 mS / cm, and / or the viscosity of the electrolyte is 1 mm 2 / s~3mm 2 / s. In this way, the electrolyte has higher ionic conductivity and lower viscosity, which is convenient for the transmission and diffusion of lithium ions, and the battery cell has more suitable fast charging performance.

[0023] In some embodiments, the electrolyte further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, propylene carbonate, or ethyl methyl carbonate. Carbonate solvents have lower viscosity, higher dielectric constant, and good electrochemical stability. Lower viscosity is conducive to the rapid migration of lithium ions in the electrolyte, improving the fast charging performance of lithium-ion battery cells; higher dielectric constant is conducive to increasing the solubility of lithium salts in the electrolyte, thereby helping to increase the concentration of lithium salts in the electrolyte; good electrochemical stability helps to increase the operating voltage range of lithium-ion battery cells, thereby increasing the capacity of lithium-ion battery cells. The combination of carbonate solvents and carboxylate solvents helps to improve the fast charging performance and cycle performance of lithium-ion battery cells.

[0024] In some embodiments, the electrolyte further comprises LiPF6.

[0025] In some embodiments, the time t for charging the battery cell from 10% SOC to 80% SOC satisfies: t≤30min. In this way, the charging time of the battery cell is shorter, and the battery cell has better fast charging performance; at the same time, through the setting of the spacer, the lithium-ion battery also has higher reliability.

[0026] In some embodiments, the time t for charging the battery cell from 10% SOC to 80% SOC satisfies: t≤17min. In this way, the battery cell has better fast charging performance, and the lithium-ion battery also has higher reliability through the provision of the spacer.

[0027] In some embodiments, the capacity Q of the battery cell satisfies: Q≥130 Ah. In this way, the battery cell has a large capacity and good fast charging performance. By using a spacer with a specific thickness, the defect of increased thermal diffusion risk caused by the large capacity and fast charging performance in the battery cell can be compensated, which is beneficial to reducing the risk of thermal diffusion inside the lithium-ion battery when the battery cell gets thermally out of control and improving the reliability of the lithium-ion battery.

[0028] In some embodiments, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, or lithium manganese iron phosphate. The above materials have high structural stability, and the battery cell including the above materials has high reliability.

[0029] In some embodiments, the water content of the positive electrode sheet is 50 ppm to 300 ppm. In this way, the water content in the positive electrode sheet is low, and there are fewer by-products HF generated by the reaction of water with lithium hexafluorophosphate, etc., which helps to reduce the damage to the SEI film and improve the cycle life of the battery cell.

[0030] In some embodiments, the battery cell further includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes one or more of a carbon material or a silicon-containing material.

[0031] In some embodiments, the negative electrode active material includes a carbon material and a silicon-containing material. Based on the total mass of the negative electrode active material, the mass content of the silicon-containing material is 0.5 wt% to 50 wt%; the thickness t of the spacer satisfies: 0.5 mm < t ≤ 5 mm.

[0032] In the above embodiments, the negative electrode active material includes a carbon material and a silicon-containing material, and the mass content of the silicon-containing material is 0.5 wt% to 50 wt%. The battery cell has a high energy density; the addition of the silicon-containing material causes the degree of thermal runaway of the battery cell to be more severe. By setting 0.5 mm < t ≤ 5 mm, the influence of the thermally runaway battery cell on the adjacent battery cells can be reduced, which helps to improve the reliability of the lithium-ion battery.

[0033] In some embodiments, based on the total mass of the negative electrode active material, the mass content of the silicon-containing material is 0.5 wt% to 10 wt%, and 0.5 mm < t ≤ 3 mm. In this way, the thickness of the spacer and the mass content of the silicon element are relatively matched, and the lithium-ion battery has high reliability and energy density.

[0034] In some embodiments, the first surface of the spacer is connected to the first wall, and the ratio of the area of the first surface to the area of the first wall is 60% - 80%. In this way, the spacer and the first wall have a relatively large contact area, which can effectively inhibit the heat diffusion between adjacent battery cells and is beneficial to improving the reliability of the lithium-ion battery.

[0035] In some embodiments, the thermal conductivity P of the spacer satisfies: 0 < P ≤ 0.05 W / (m·K). In this way, the thermal conductivity of the spacer is relatively small, which can effectively inhibit the heat diffusion between adjacent battery cells and is beneficial to improving the reliability of the lithium-ion battery.

[0036] In some embodiments, 0.005 W / (m·K) ≤ P ≤ 0.03 W / (m·K). In this way, the spacer has a relatively small thermal conductivity, which can effectively inhibit the heat diffusion between adjacent battery cells and is beneficial to improving the reliability of the lithium-ion battery.

[0037] In some embodiments, the spacer is a heat insulation board. In this way, it is convenient for the processing of the spacer and for the spacer to be arranged between adjacent battery cells.

[0038] In some embodiments, the material of the spacer includes at least one of the following: heat insulation cotton, plastic foam, glass wool, vacuum heat insulation board, and silica aerogel. The above materials have good heat insulation effects, can inhibit the heat diffusion between adjacent battery cells, and are beneficial to improving the reliability of the lithium-ion battery.

[0039] In some embodiments, the spacer includes a flow channel for accommodating a fluid to adjust the temperature of the battery cell. The flow channel can accommodate a fluid to adjust the temperature of the battery cell. For example, it can better cool the battery cell and further reduce the risk of heat diffusion.

[0040] In some embodiments, the spacer includes a first plate and a second plate opposite to each other in the thickness direction of the spacer, and the flow channel is arranged between the first plate and the second plate. The flow channel is formed between the first plate and the second plate, which is convenient for adjusting the temperature of the battery cell.

[0041] In some embodiments, the thickness of the spacer is 3 mm - 6 mm. In this way, the flow channel has a suitable size, can accommodate a relatively appropriate amount of fluid, and has a good effect on adjusting the temperature of the battery cell.

[0042] In some embodiments, the battery cell includes a housing for accommodating the electrolyte and the positive electrode plate, and the housing is provided with a pressure relief mechanism, and the actuation pressure P of the pressure relief mechanism satisfies: 0.5 MPa ≤ P ≤ 1.8 Mpa.

[0043] In the battery cell of the present application, since the battery cell has a higher capacity and a higher content of LiFSI, the gas production in the battery cell increases and the pressure in the battery cell increases; by setting the actuation pressure of the pressure relief mechanism to be greater than or equal to 0.5 MPa, it is helpful to reduce the risk of premature actuation of the pressure relief mechanism, thereby helping to improve the storage life of the battery cell; by setting the actuation pressure of the pressure relief mechanism to be less than or equal to 1.8 MPa, it is helpful to reduce the risk of positions outside the pressure relief mechanism, such as the battery cell shell, rupturing before the pressure relief mechanism when the battery cell thermally runs away, which is helpful to reduce the influence of the thermally runaway battery cell on the adjacent battery cell, thereby helping to improve the reliability of the lithium-ion battery.

[0044] In some embodiments, 0.7MPa≤P≤1.4MPa. By setting the actuation pressure of the pressure relief mechanism to meet the above range, it is helpful to further reduce the risk of the pressure relief mechanism actuating the valve to open during normal use of the lithium-ion battery cell, which is helpful to increase the storage time and storage life of the lithium-ion battery cell.

[0045] In some embodiments, the material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm.

[0046] In some embodiments, the thickness of the shell is 0.2 mm to 0.3 mm.

[0047] Steel has high strength. By setting the material of the shell to include steel, the pressure relief mechanism has a suitable actuation pressure, which is beneficial to improving the storage life of the lithium-ion battery cell.

[0048] In some embodiments, the material of the shell includes aluminum, and the thickness of the shell is 0.3 mm to 1.0 mm.

[0049] In some embodiments, the thickness of the shell is 0.5 mm to 0.6 mm.

[0050] Aluminum has high strength and relatively suitable processing performance. By setting the material of the shell to include aluminum, it is convenient to prepare the shell, and the pressure relief mechanism also has a suitable actuation pressure, which is beneficial to improving the storage life of the lithium-ion battery cell.

[0051] In a second aspect, an electrical device is provided, comprising the lithium-ion battery in the first aspect and any possible embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0053] Figure 1 A schematic diagram of a lithium-ion battery according to an embodiment of the present application;

[0054] Figure 2 A schematic diagram of a battery cell and a spacer according to an embodiment of the present application;

[0055] Figure 3 A schematic diagram of a battery cell and a spacer according to an embodiment of the present application;

[0056] Figure 4 A schematic diagram of a spacer according to an embodiment of the present application;

[0057] Figure 5 for Figure 4 An enlarged schematic diagram of region B in FIG.

[0058] Figure 6 A schematic diagram of a battery cell according to an embodiment of the present application;

[0059] Figure 7 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application.

[0060] The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0061] The embodiments of the lithium-ion battery and the electrical device of the present application are described in detail with appropriate reference to the drawings, but there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0062] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0063] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0064] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0065] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0066] The development of battery technology must consider many design factors at the same time, such as energy density, cycle life at high temperature, capacity, fast charging performance, reliability, etc. Lithium-containing phosphates are widely used in lithium-ion batteries due to their high structural stability. However, lithium-containing phosphates have strong water absorption and have bound water. In the process of drying the positive electrode sheet including lithium-containing phosphates, it is difficult to completely remove the water therein. The water in the lithium-containing phosphate reacts with the electrolyte salt lithium hexafluorophosphate in the electrolyte to produce by-products such as HF, which has the risk of destroying the SEI film and reducing the cycle life of the lithium-ion battery, especially the high-temperature cycle life. Adding LiFSI to the electrolyte is conducive to reducing the generation of by-products such as HF, which helps to improve the high-temperature cycle life of lithium-ion batteries; and LiFSI also has the characteristics of high ionic conductivity and good thermal stability. It is generally believed that the application of LiFSI in the electrolyte is conducive to improving the fast charging performance and reliability of lithium-ion batteries. However, the technical personnel of the present application have found through research that the addition of LiFSI will lead to more severe thermal runaway of the battery cells, and more heat will spread to adjacent battery cells, which is not conducive to improving the overall reliability of the lithium-ion battery.

[0067] In view of this, in the lithium-ion battery of the present application, the electrolyte includes LiFSI, and the mass content of LiFSI is 1wt% to 20wt% based on the total mass of the electrolyte. The positive electrode active material includes a lithium phosphate, and a spacer is arranged between the walls with the largest surface area of ​​adjacent battery cells, and the thickness of the spacer is reasonably set to further reduce the impact of thermal runaway battery cells on adjacent battery cells while improving the fast charging performance and high-temperature cycle life of the lithium-ion battery, thereby taking into account fast charging performance, high-temperature cycle life and high reliability.

[0068] During the charging process of the battery cell, lithium ions are released from the positive electrode active material, moved and embedded in the negative electrode; while during the discharge process, lithium ions are released from the negative electrode, moved and embedded in the positive electrode active material.

[0069] It should be understood that the "embedding" process described in this application refers to the process in which lithium ions are embedded in the positive electrode active material or the negative electrode due to an electrochemical reaction, and the "extraction" and "de-embedding" processes described in this application refer to the process in which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0070] A lithium-ion battery includes a plurality of battery cells, wherein the plurality of battery cells can first be combined into a battery module, and then the battery module can be combined into a lithium-ion battery; or the plurality of battery cells can directly be combined into a lithium-ion battery.

[0071] The battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. Next, the lithium-ion battery, the battery cell and each part of the battery cell provided in the present application are introduced.

[0072] [Lithium-ion battery]

[0073] Figure 1 is a schematic diagram of a lithium-ion battery according to an embodiment of the present application, Figure 2 is a schematic diagram of a battery cell and an isolating member according to an embodiment of the present application, Figure 3 It is a schematic diagram of a battery cell and an isolation member according to an embodiment of the present application.

[0074] The present application embodiment provides a lithium ion battery 10, for example, referring to Figures 1 to 3 As shown, the lithium-ion battery 10 includes a battery cell 20 and a separator 30 .

[0075] The battery cell 20 includes an electrolyte, the electrolyte includes LiFSI, and based on the total mass of the electrolyte, the mass content A of the LiFSI satisfies: 1 wt % ≤ A ≤ 20 wt %.

[0076] A can be 1wt%, 1.5wt%, 2wt%, 3wt%, 4wt%, 5wt%, 8wt%, 10wt%, 12wt%, 14.5wt%, 15wt%, 18wt%, 20wt% or any value within the above range.

[0077] The battery cell 20 includes a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

[0078] Lithium-containing phosphates refer to phosphates with an olivine structure, such as lithium iron phosphate, lithium manganese iron phosphate, and lithium manganese phosphate. Lithium-containing phosphates can also be modified by doping or surface coating to improve corresponding performance. For example, the surface of lithium-containing phosphates is coated with carbon materials to improve the conductivity of the positive electrode active material.

[0079] The spacer 30 is disposed between the first walls 201 of two adjacent battery cells 20. The first wall 201 is the wall with the largest surface area of ​​the battery cell 20. The thickness t of the spacer 30 satisfies: 0.2 mm <t≤8mm。

[0080] For example, combined with Figure 2 As shown, the thickness direction of the spacer 30 can be Figure 2 The X direction in .

[0081] The thickness t of the spacer 30 may be an average thickness of the spacer 30. For example, along the extension direction of the spacer 30, for example, Figure 2 In the Y direction, 5 positions are selected, and the thickness of the spacer 30 at the position is measured respectively. The average value of the 5 thickness values ​​is taken to obtain t.

[0082] The thickness t of the spacer 30 can be 0.25 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 6 mm, 7 mm, 8 mm, or any value within the above range.

[0083] The spacer 30 can have a plate-like structure. For example, the spacer 30 is a heat-insulating plate.

[0084] The spacer 30 can have a certain elasticity and can buffer the expansion between adjacent battery cells 20.

[0085] The spacer 30 can be a single-layer structure or a multi-layer structure. The spacer 30 can be an internally hollow structure or can be filled with heat-insulating materials inside.

[0086] Based on the total mass of the electrolyte, when the mass content of LiFSI reaches 1 wt% and above, the degree of thermal runaway of the battery cell 20 is more severe, the temperature of the battery cell 20 is higher, and more gas is generated. Therefore, the impact on adjacent battery cells is greater. By setting the positive electrode active material to include lithium-containing phosphate and arranging a spacer 30 between adjacent battery cells 20, and the thickness of the spacer 30 is greater than 0.2 mm, the thermal diffusion between adjacent battery cells 20 can be effectively inhibited, the heat diffusion when a certain battery cell 20 undergoes thermal runaway can be inhibited from spreading to adjacent battery cells 20, the impact on adjacent battery cells 20 can be reduced, and thus it is beneficial to improve the overall reliability of the lithium-ion battery 10.

[0087] In addition, when the thickness of the spacer 30 is less than or equal to 8 mm, while inhibiting the thermal diffusion between adjacent battery cells 20, the space occupied by the spacer 30 can be reduced, the space utilization rate inside the lithium-ion battery 10 can be improved, and the lithium-ion battery 10 has a more appropriate energy density.

[0088] In the embodiment of the present application, the electrolyte includes LiFSI, and based on the total mass of the electrolyte, the mass content A of LiFSI satisfies: 1 wt% ≤ A ≤ 20 wt%. In this way, the battery cell 20 has good fast charging performance and long cycle life at high temperatures; the positive electrode active material includes lithium-containing phosphate, and a spacer 30 is arranged between the first walls 201 with the largest surface area of adjacent battery cells 20, and the thickness t of the spacer 30 satisfies: 0.2 mm < t ≤ 8 mm. In this way, the spacer 30 with the above thickness can inhibit the heat transfer between adjacent battery cells 20, which is beneficial to reducing the risk of thermal diffusion inside the lithium-ion battery 10 during thermal runaway.

[0089] In some embodiments, 0.5 mm≤t≤5 mm.

[0090] When t≥0.5mm, the heat transfer between adjacent battery cells 20 can be further suppressed, reducing the risk of heat diffusion inside the lithium-ion battery 10 during thermal runaway; when t≤5mm, the spacer 30 occupies a suitable space, the lithium-ion battery has a suitable space utilization rate, and the battery cell 20 has a higher energy density. Through the above arrangement, the lithium-ion battery has higher reliability and higher energy density.

[0091] In some embodiments, 1.5 wt % ≤ A ≤ 5 wt %, 0.5 mm ≤ t ≤ 3 mm.

[0092] When the mass content A of LiFSI satisfies 1.5wt%≤A≤5wt%, the battery cell 20 has better fast charging performance and better high-temperature cycle life, but the degree of thermal runaway of the battery cell 20 is more severe, and the heat generated by the battery cell 20 in thermal runaway is also more. By setting t≥0.5mm, the heat of the runaway battery cell 20 can be suppressed from diffusing to the adjacent battery cell 20, thereby reducing the risk of causing thermal diffusion of the adjacent battery cell 20, and the lithium-ion battery 10 has higher reliability; by setting t≤3mm, the lithium-ion battery 10 has a suitable space utilization inside, and the lithium-ion battery 10 has a suitable energy density.

[0093] In the above embodiment, when the mass content A of LiFSI satisfies 1.5wt%≤A≤5wt%, the thickness t of the spacer 30 is set to satisfy 0.5mm≤t≤3mm, and the lithium-ion battery 10 can have fast charging performance, long cycle life at high temperature, high reliability and suitable energy density.

[0094] In some embodiments, 5 wt % ≤ A ≤ 16 wt %, 1 mm ≤ t ≤ 5 mm.

[0095] When the mass content A of LiFSI satisfies 5wt%≤A≤16wt%, the battery cell 20 has better fast charging performance and high temperature cycle life, but the degree of thermal runaway of the battery cell 20 is more severe, and the heat generated by the battery cell 20 in thermal runaway is also more. By setting t≥1mm, the heat of the runaway battery cell 20 can be suppressed from diffusing to the adjacent battery cell 20, thereby reducing the risk of causing thermal diffusion of the adjacent battery cell 20, and the lithium-ion battery 10 has higher reliability; by setting t≤5mm, the lithium-ion battery 10 has a suitable space utilization inside, and the lithium-ion battery 10 has a suitable energy density.

[0096] In the above embodiment, when the mass content A of LiFSI satisfies 5wt%≤A≤16wt%, the thickness t of the spacer 30 is set to satisfy 1mm≤t≤3.5mm, and the lithium-ion battery 10 can have fast charging performance, long cycle life at high temperature and high reliability.

[0097] In some embodiments, 5wt%≤A≤16wt%, 1mm≤t≤3.5mm. In this way, the space occupied by the spacer 30 is further reduced while reducing heat diffusion, thereby facilitating the improvement of the energy density of the lithium-ion battery.

[0098] In some embodiments, the capacity Q of the battery cell 20 satisfies: 50 Ah≤Q≤300 Ah.

[0099] Different battery cells 20 may have different capacities. The capacity Q of the battery cell 20 may be 50Ah, 60Ah, 70Ah, 80Ah, 90Ah, 100Ah, 110Ah, 120Ah, 125Ah, 135Ah, 150Ah, 160Ah, 180Ah, 200Ah, 210Ah, 220Ah, 230Ah, 250Ah, 260Ah, 280Ah, 300Ah, or any value within the above range.

[0100] The battery cells 20 of different capacities may be provided with the same mass content of LiFSI, or may be provided with different mass contents of LiFSI.

[0101] When the capacity of the battery cell 20 is large, for example, when the capacity Q of the battery cell 20 is greater than 100 Ah, more heat is accumulated at the tabs in the battery cell 20 , and there is a greater need to suppress heat diffusion of the battery cell 20 .

[0102] In some embodiments, 50Ah≤Q≤130Ah, 0.5mm≤t≤1mm.

[0103] When the capacity Q of the battery cell satisfies 50Ah≤Q≤130Ah, the thickness t of the spacer is set to satisfy 0.5mm≤t≤1mm, which can effectively suppress the heat diffusion between adjacent battery cells 20. On the premise that the battery cell 20 has a suitable capacity, the lithium-ion battery 10 has a higher reliability; and the thickness of the spacer 30 is relatively appropriate, and the lithium-ion battery 10 also has a higher energy density.

[0104] In the above embodiment, when the capacity Q of the battery cell 20 and the thickness t of the spacer 30 meet the above ranges, the risk of heat diffusion inside the lithium-ion battery during thermal runaway is low, and the lithium-ion battery has higher reliability and more suitable energy density.

[0105] In some embodiments, 130Ah≤Q≤300Ah, 1mm≤t≤5mm.

[0106] When the capacity Q of the battery cell satisfies 130Ah≤Q≤300Ah, the more heat is accumulated at the tabs in the battery cell 20, the higher the temperature of the battery cell 20 is. By setting the thickness t of the spacer 30 to satisfy 1mm≤t≤5mm, the risk of heat from a battery cell 20 that has thermal runaway diffusing to an adjacent battery cell 20 can be effectively suppressed, and the risk of causing thermal runaway of an adjacent battery cell 20 can be reduced, and the lithium-ion battery 10 has higher reliability. In addition, t≤5mm, the space utilization rate inside the lithium-ion battery 10 is higher, and the lithium-ion battery 10 has a higher energy density.

[0107] In the above embodiment, when the capacity Q of the battery cell 20 and the thickness t of the spacer 30 meet the above ranges, the risk of heat diffusion inside the lithium ion battery 10 during thermal runaway is low, and the lithium ion battery 10 has higher reliability and energy density.

[0108] In some embodiments, 1.5 wt % ≤ A ≤ 5 wt %, 130 Ah ≤ Q ≤ 300 Ah, and 1 mm ≤ t ≤ 3.5 mm.

[0109] In the case of 130Ah≤Q≤300Ah, 1.5wt%≤A≤5wt% is set, and the lithium-ion battery has a higher capacity and a more suitable fast-charging performance. Furthermore, 1mm≤t≤3.5mm is set, and the risk of heat diffusion inside the lithium-ion battery is lower and the space occupied by the spacer is more suitable. Therefore, the lithium-ion battery has a higher capacity, better fast-charging performance and cycle performance, higher reliability and higher energy density.

[0110] In some embodiments, 5wt%≤A≤16wt%, 130Ah≤Q≤300Ah, and 1.5mm≤t≤5mm.

[0111] In the case of 130Ah≤Q≤300Ah, setting 5wt%≤A≤16wt%, the lithium-ion battery has a higher capacity and more suitable fast charging performance, but with the increase in the mass content of LiFSI, the severity of thermal runaway of the battery cell increases, and the thermal runaway battery cell has a greater impact on the adjacent battery cell. By setting 1.5mm≤t≤5mm, the risk of thermal diffusion in the lithium-ion battery is reduced. Therefore, the lithium-ion battery has a higher capacity, better fast charging performance and cycle performance, and higher reliability.

[0112] In some embodiments, the electrolyte further includes a carboxylic acid ester solvent. Based on the total mass of the electrolyte, the mass content W0 of the carboxylic acid ester solvent satisfies: 5 wt% ≤ W0 ≤ 80 wt%.

[0113] W0 can be 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt% or any value within the above range.

[0114] After formation, the mass of the carboxylic acid ester solvent is approximately consumed by 1% - 15%. It should be noted that here it refers to the consumption of the carboxylic acid ester solvent in the fresh lithium-ion battery compared to the unformed lithium-ion battery. A fresh lithium-ion battery can refer to a lithium-ion battery that has just been assembled onto a vehicle, at this time, the vehicle has not yet traveled or has traveled a small mileage. The less the vehicle has traveled, the fresher the lithium-ion battery is.

[0115] For example, the mass content of the carboxylic acid ester solvent after formation is approximately in the range of 1 wt% - 78 wt%.

[0116] In addition, it should be noted that during the process of disassembling the lithium-ion battery to obtain the electrolyte, the solvent in the electrolyte may volatilize. For example, based on the total mass of the electrolyte, the mass of the volatilized carboxylic acid ester solvent is approximately 1% - 10%.

[0117] When, based on the total mass of the electrolyte, the mass content W0 of the carboxylic acid ester solvent is 5 wt% - 80 wt%, the ionic conductivity of the electrolyte is 9 mS / cm - 20 mS / cm, and the charging rate of the battery cell is 2.5C - 8C.

[0118] The electrolyte includes a carboxylic acid ester solvent. In this way, the electrolyte has higher ionic conductivity and lower viscosity, which is beneficial to further improving the fast charging performance of the battery cell. With the improvement of the fast charging performance of the battery cell, the charging current during fast charging of the battery cell is larger, more heat is generated inside the battery cell, and thus the severity during thermal runaway of the battery cell is also greater, increasing the risk of thermal diffusion. By setting 5 wt% ≤ W0 ≤ 80 wt% and setting the thickness t of the spacer to satisfy 0.2 mm < t ≤ 5 mm, the risk of thermal diffusion can be reduced while improving the fast charging performance.

[0119] In some embodiments, the carboxylic acid ester solvent includes ethyl acetate. Based on the total mass of the electrolyte, the mass content W1 of ethyl acetate satisfies: 15 wt% ≤ W1 ≤ 80 wt%, and the thickness t of the spacer 30 satisfies: 1 mm ≤ t ≤ 5 mm.

[0120] After the battery cell is formed, W1 can be 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 48wt%, 50wt%, 60wt%, 70wt%, 80wt% or any value within the above range.

[0121] Ethyl acetate has a more suitable ionic conductivity, and the gas produced by the side reaction of ethyl acetate is also less. By setting the mass content of ethyl acetate to 25wt% to 50wt%, the battery cell can have better fast charging performance and cycle performance, as well as less gas production.

[0122] After adding ethyl acetate, the side reaction of ethyl acetate in the battery cell will also cause the temperature inside the battery cell to rise. By setting the thickness t of the spacer 30 to be greater than or equal to 1 mm, the heat transfer between adjacent battery cells can be reduced, and the risk of heat diffusion inside the lithium-ion battery 10 can be reduced. In addition, setting the thickness t of the spacer 30 to be less than or equal to 5 mm is also beneficial to improving the energy density of the lithium-ion battery 10.

[0123] In the above embodiment, the battery cell 20 has a high fast charging performance, and when a battery cell 20 has thermal runaway, the spacer 30 can suppress the heat of the battery cell 20 in thermal runaway from diffusing to the adjacent battery cell 20, which is beneficial to improving the reliability of the lithium-ion battery 10 and the lithium-ion battery 10 has a higher energy density.

[0124] In some embodiments, 15wt%≤W1≤50wt%, 1mm≤t≤3mm. In this way, ethyl acetate has a more suitable mass content, the battery cell has a more suitable fast charging performance, and the spacer 30 can also suppress the heat of the battery cell 20 in thermal runaway from diffusing to the adjacent battery cell 20 while reducing the space occupied by itself, so that the lithium-ion battery can take into account both reliability and higher energy density.

[0125] In some embodiments, the carboxylate solvent includes methyl acetate. Based on the total mass of the electrolyte, the mass content W2 of methyl acetate satisfies: 7wt%≤W2≤60wt%, and the thickness t of the spacer 30 satisfies: 1.5mm≤t≤5mm.

[0126] After chemical formation, W2 can be 7wt%, 10wt%, 15wt%, 20wt%, 30wt%, 35wt%, 40wt%, 50wt%, 60wt% or any value within the above range.

[0127] When the mass content W2 of methyl acetate is 7wt% to 60wt% based on the total mass of the electrolyte, the ionic conductivity of the electrolyte is 12mS / cm to 18mS / cm, and the charging rate of the battery cell is 2.5C to 6C.

[0128] Compared with ethyl acetate, methyl acetate has higher ionic conductivity, and the battery cell has better fast charging performance, with a larger charging current during fast charging, more heat in the battery cell, and greater severity during thermal runaway. By setting the thickness t of the spacer 30 to be greater than or equal to 1.5 mm, the heat transfer between adjacent battery cells can be reduced, and the risk of heat diffusion inside the lithium-ion battery 10 can be reduced; in addition, setting the thickness t of the spacer 30 to be less than or equal to 5 mm is also conducive to improving the energy density of the lithium-ion battery 10.

[0129] In the above embodiment, the battery cell 20 has a high fast charging performance, and when a battery cell 20 has thermal runaway, the spacer 30 can suppress the heat of the battery cell 20 with thermal runaway from diffusing to the adjacent battery cell 20, which is beneficial to improving the reliability of the lithium-ion battery.

[0130] In some embodiments, 10wt%≤W2≤40wt%, 1.5mm≤t≤3mm. In this way, methyl acetate has a more suitable mass content, the battery cell has a more suitable fast charging performance, and the spacer 30 can also suppress the heat of the battery cell 20 in thermal runaway from diffusing to the adjacent battery cell 20 while reducing the space occupied by itself, so that the lithium-ion battery 10 can take into account both reliability and higher energy density.

[0131] In some embodiments, the carboxylate solvent includes ethyl acetate and methyl acetate. Based on the total mass of the electrolyte, the mass content W1 of ethyl acetate satisfies: 25wt%≤A≤50wt%, the mass content W2 of methyl acetate satisfies: 15wt%≤W2≤30wt%, and the thickness t of the spacer 30 satisfies: 1.8mm≤t≤3mm.

[0132] By combining the above-mentioned mass contents of ethyl acetate and methyl acetate, the battery cell can further take into account both fast charging performance and the severity of thermal runaway; by setting the thickness t of the spacer 30 to satisfy 1.8mm≤t≤3mm, the risk of thermal diffusion can be further reduced, while the energy density of the lithium-ion battery 10 can be improved.

[0133] In some embodiments, the ionic conductivity of the electrolyte is 9 mS / cm to 25 mS / cm, and / or the viscosity of the electrolyte is 1 mm 2 / s~3mm 2 / s.

[0134] The ion conductivity of the electrolyte may be 9 mS / cm, 11 mS / cm, 15 mS / cm, 16 mS / cm, 18 mS / cm, 20 mS / cm, 22 mS / cm, 25 mS / cm, or any value within the above range.

[0135] The electrolyte has a high ionic conductivity, which is conducive to the diffusion and transmission of lithium ions, and the lithium-ion battery cells have excellent fast charging performance.

[0136] The viscosity of the electrolyte can be 1mm 2 / s、1.5mm 2 / s, 2mm 2 / s, 2.5mm 2 / s、3mm 2 / s or any value within the above range.

[0137] The viscosity of the electrolyte is 1 mm 2 / s~3mm 2 / s, which is conducive to the diffusion and transmission of lithium ions, and the lithium-ion battery monomer has better fast charging performance.

[0138] In some embodiments, the electrolyte further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, propylene carbonate, or ethyl methyl carbonate.

[0139] As an example, carbonate solvents include ethylene carbonate and dimethyl carbonate. Dimethyl carbonate can improve the conductivity of the electrolyte, thereby improving the fast charging performance of lithium-ion battery cells. Ethylene carbonate can form a film on the surface of the negative electrode, reducing the side reaction between the carboxylate and the negative electrode, which is beneficial to improving the cycle life of lithium-ion battery cells.

[0140] Carbonate solvents have low viscosity, high dielectric constant and good electrochemical stability. Low viscosity is conducive to the rapid migration of lithium ions in the electrolyte, improving the fast charging performance of lithium-ion battery cells; high dielectric constant is conducive to improving the solubility of lithium salts in the electrolyte, thereby helping to increase the concentration of lithium salts in the electrolyte; good electrochemical stability helps to increase the operating voltage range of lithium-ion battery cells, thereby increasing the capacity of lithium-ion battery cells. The combination of carbonate solvents and carboxylate solvents helps to improve the fast charging performance and cycle performance of lithium-ion battery cells.

[0141] In some embodiments, the carboxylate solvent includes a compound of the structure shown in Formula I,

[0142]

[0143] Wherein, R1 and R2 each independently include at least one of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

[0144] In some embodiments, the carboxylate solvent includes: one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl acrylate or ethyl acrylate. By selecting the above carboxylate solvent, the electrolyte has a lower viscosity and a higher ionic conductivity, which is beneficial to improving the fast charging performance of the lithium-ion battery monomer.

[0145] In some embodiments, the carboxylic acid ester solvent includes at least one of methyl acetate and ethyl acetate. The molecules of methyl acetate and ethyl acetate have suitable chain lengths, have low viscosity and are suitable for gas production, and have a suitable effect on the severity of thermal runaway of the battery cell, so that the battery cell can have better fast charging performance and higher reliability.

[0146] In some embodiments, the electrolyte further includes LiPF6. In this embodiment, the electrolyte salt in the electrolyte includes LiPF6 and LiFSI. Compared with LiFSI, LiPF6 has less effect on the severity of thermal runaway. By setting the electrolyte to include LiPF6 and LiFSI, the battery cell has a suitable severity of thermal runaway, the risk of thermal diffusion in the lithium-ion battery is low, and the lithium-ion battery has higher reliability.

[0147] In some embodiments, the time t for charging the battery cell 20 from 10% SOC to 80% SOC satisfies: t≤30 min. In this way, the charging time of the battery cell 20 is shorter, and the battery cell 20 has better fast charging performance.

[0148] The time t can be 17 min, 16.8 min, 16.5 min, 16 min, 15 min, 14.5 min, 14 min, 13 min, 12 min, 11 min, 10 min, 9 min, 8 min, 7.5 min, 7 min or any value within the above range.

[0149] The above charging time is the charging time of the battery cell at 25°C to 35°C, and the charging time reflects the fast charging capability of the battery cell. During the fast charging process of the battery cell, the current density (or rate) is usually not constant, but variable.

[0150] In some embodiments, the time t for charging the battery cell 20 from 10% SOC to 80% SOC satisfies: t≤17 min.

[0151] In some embodiments, the charging time of a lithium-ion battery from 10% SOC to 80% SOC is less than or equal to 17 minutes when the charging rate is greater than or equal to 2.5C. This rate is the equivalent charging rate of the battery cell during the process of charging from 10% SOC to 80% SOC. In other words, in the process of charging from 10% SOC to 80% SOC, the charging rate may gradually decrease from greater than 2.5C to less than 2.5C. In this process, the battery cell may undergo a transition from constant current charging to constant voltage charging, so the current is not constant. For example: start charging the battery cell at a normal temperature of 25°C, charging from 10% SOC to 80% SOC, and the charging time is 10 minutes (equivalent charging rate ≥ 4C). The charging process is: initially at 5C from 10% SOC to 45% SOC, then at 4.6C from 45% SOC to 50% SOC, 4.3C from 50% SOC to 55% SOC, 3.9C from 55% SOC to 60% SOC, 3.6C from 60% SOC to 65% SOC, 3.3C from 65% SOC to 70% SOC, 3.1C from 70% SOC to 75% SOC, 2.9C from 75% SOC to 80% SOC, and the charging is completed. The charging time for the battery cell to charge from 0% SOC to 100% SOC at 1C is 60min. Therefore, when it is measured that the charging time of the battery cell from 10% SOC to 80% SOC is 10 minutes, the equivalent charging rate of the process can be calculated as: [(80% SOC-10% SOC) / (100% SOC-0% SOC)]×[(1C×60min) / 10min]=4.2C.

[0152] If the battery cell is placed on a charging station for charging, the time it takes to charge from 10% SOC to 80% SOC can also be directly recorded.

[0153] When the vehicle is charging at a charging pile, the charging curve will be displayed on the charging pile system (the charging curve may be seen on the charging pile display screen, on the mobile phone charging control APP, in the battery monitoring background, etc.). For example, the horizontal axis is the charging time, and the vertical axis is the charging power and charging SOC. The charging power and SOC of the vehicle's battery at different times can be seen from the charging curve, and the charging time of 20% SOC-80% SOC or 10% SOC-80% SOC can also be read from the charging curve.

[0154] In some embodiments, the capacity Q of the battery cell satisfies: Q ≥ 130Ah. In this way, the battery cell has a large capacity and good fast charging performance. By using it with a spacer with a specific thickness, it can make up for the defect of increased heat diffusion risk caused by large capacity and fast charging performance in the battery cell, which is conducive to reducing the risk of heat diffusion inside the lithium-ion battery caused by thermal runaway of the battery cell and improving the reliability of the lithium-ion battery.

[0155] In some embodiments, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, or lithium manganese iron phosphate. The above materials have high structural stability, and the battery cell 20 including the above materials has high reliability.

[0156] In some embodiments, the water content of the lithium-containing phosphate is 0 ppm to 1000 ppm.

[0157] The water content of the lithium-containing phosphate may be 1 ppm, 10 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm or any value within the above range.

[0158] In this way, the water content in the lithium-containing phosphate is lower, and the byproduct HF produced by the reaction of water with lithium hexafluorophosphate is less, which helps to reduce damage to the SEI film and improve the cycle life of the battery cell.

[0159] In some embodiments, the water content of the positive electrode sheet is 50 ppm to 300 ppm.

[0160] The water content of the positive electrode sheet can be 50ppm, 60ppm, 80ppm, 100ppm, 120ppm, 150ppm, 180ppm, 200ppm, 220ppm, 250ppm, 280ppm, 300ppm or any value within the above range.

[0161] In this way, the water content in the positive electrode is lower, and the byproduct HF produced by the reaction of water with lithium hexafluorophosphate is less, which helps to reduce damage to the SEI film and improve the cycle life of the battery cell.

[0162] In some embodiments, the battery cell further includes a negative electrode plate, the negative electrode plate includes a negative electrode active material, and the negative electrode active material includes one or more of a carbon material or a silicon-containing material.

[0163] As an example, the negative electrode active material includes a carbon material or a silicon-containing material.

[0164] As an example, the negative electrode active material includes a silicon-containing material and a carbon material.

[0165] In some embodiments, the negative electrode active material includes a carbon material and a silicon-containing material. Based on the total mass of the negative electrode active material, the mass content of the silicon-containing material is 0.5 wt% to 50 wt%; the thickness t of the spacer satisfies: 0.5 mm < t ≤ 5 mm.

[0166] Based on the total mass of the negative electrode active material, the mass content of the silicon-containing material can be 0.5 wt%, 1 wt%, 1.5 wt%, 5 wt%, 8 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt% or any value within the above range.

[0167] In the above embodiments, the negative electrode active material includes a carbon material and a silicon-containing material, and the mass content of the silicon-containing material is 0.5 wt% to 50 wt%. The battery cell has a relatively high energy density; the addition of the silicon-containing material results in a more severe degree of thermal runaway of the battery cell. By setting 0.5 mm < t ≤ 5 mm, the influence of the battery cell with thermal runaway on adjacent battery cells can be reduced, and the risk of thermal diffusion occurring in the lithium-ion battery can be reduced, which helps to improve the reliability of the lithium-ion battery.

[0168] In some embodiments, based on the total mass of the negative electrode active material, the mass content of the silicon-containing material is 0.5 wt% to 10 wt%, and 0.5 mm < t ≤ 3 mm. In this way, the thickness of the spacer and the mass content of the silicon element are relatively matched, and the lithium-ion battery has relatively high reliability and energy density.

[0169] In some embodiments, the first surface 301 of the spacer 30 is connected to the first wall 201, and the ratio of the area of the first surface 301 to the area of the first wall 201 is 60% to 80%.

[0170] The ratio of the area of the first surface 301 to the area of the first wall 201 can be 60%, 65%, 70%, 75%, 80% or any value within the above range.

[0171] The spacer 30 has two surfaces opposite to each other along its own thickness direction, and the first surface 301 of the spacer 30 is one of the two surfaces opposite to each other in the thickness direction of the spacer 30.

[0172] In the above embodiments, the spacer 30 has a relatively large contact area with the first wall, which can effectively inhibit the thermal diffusion between adjacent battery cells 20 and is beneficial to improving the reliability of the lithium-ion battery.

[0173] In some embodiments, the thermal conductivity P of the spacer 30 satisfies: 0 < P ≤ 0.05 W / (m·K).

[0174] P can be 0.001 W / (m·K), 0.002 W / (m·K), 0.005 W / (m·K), 0.01 W / (m·K), 0.02 W / (m·K), 0.03 W / (m·K), 0.04 W / (m·K), 0.05 W / (m·K) or any value within the above range.

[0175] In the above embodiment, the thermal conductivity of the spacer 30 is relatively small, which can effectively suppress the heat diffusion between adjacent battery cells 20 , and is beneficial to improving the reliability of the lithium-ion battery.

[0176] In some embodiments, 0.005 W / (m·K)≤P≤0.03 W / (m·K). In this way, the spacer 30 has a relatively small thermal conductivity, which can effectively suppress the heat diffusion between adjacent battery cells 20, and is beneficial to improving the reliability of the lithium-ion battery.

[0177] In some embodiments, the spacer 30 is a heat insulating plate, which facilitates the processing of the spacer 30 and the placement of the spacer 30 between adjacent battery cells 20 .

[0178] In some embodiments, the material of the spacer 30 includes at least one of thermal insulation wool, plastic foam, glass wool, vacuum insulation board, and silica aerogel. The above materials have good thermal insulation effect, can inhibit heat diffusion between adjacent battery cells 20, and are conducive to improving the reliability of lithium-ion batteries.

[0179] In some embodiments, the spacer 30 is a continuous plate-shaped structure. One spacer 30 is connected to the first walls 201 of the plurality of battery cells 20 .

[0180] As an example, the lithium-ion battery 10 includes: a plurality of columns of battery cells 20 arranged along a first direction, each column of battery cells 20 includes a plurality of battery cells 20 arranged along a second direction, the first direction being perpendicular to the second direction; a plurality of spacers 30 arranged along the first direction, each spacer 30 extending continuously along the second direction and alternately arranged with each column of battery cells 20.

[0181] In some embodiments, the lithium-ion battery 10 includes: a plurality of battery cells 20 arranged along the second direction; a plurality of spacers 30 arranged along the second direction, and the spacers 30 and the battery cells 20 are alternately arranged along the second direction.

[0182] Figure 4 is a schematic diagram of a spacer according to an embodiment of the present application, Figure 5 for Figure 4 In some embodiments, for example, Figure 4 and Figure 5As shown, the spacer 30 includes a flow channel 300 for containing a fluid to adjust the temperature of the battery cell. The flow channel can contain a fluid to adjust the temperature of the battery cell, for example, the battery cell can be better cooled to further reduce the risk of heat diffusion.

[0183] The fluid can be circulated to achieve a better temperature regulation effect. Optionally, the fluid can be water, a mixture of water and ethanol, a refrigerant or air.

[0184] In some embodiments, the spacer 30 includes a first plate 310 and a second plate 320 opposite to each other in the thickness direction of the spacer 30, and a flow channel 300 is provided between the first plate 310 and the second plate 320. The flow channel 300 is formed between the first plate 310 and the second plate 320 to facilitate temperature adjustment for the battery cells.

[0185] In some embodiments, the spacer 30 further includes a reinforcing rib 330, and the reinforcing rib 330 is connected to at least one of the first plate 310 and the second plate 320. For example, the reinforcing rib 330 is connected to the first plate 310 and the second plate 320; for another example, the reinforcing rib 330 is only connected to the first plate 310 or the second plate 320. The angle between the reinforcing rib 330 and the first plate 310 or the second plate 320 can be an acute angle, a right angle, or an obtuse angle.

[0186] In some embodiments, the thickness t of the spacer 30 is 3 mm to 6 mm.

[0187] In the case where the spacer 30 includes the flow channel 300 , the thickness t of the spacer 30 may be 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, or any value within the above range.

[0188] When the thickness t of the spacer 30 is greater than or equal to 3 mm, the flow channel has a suitable size and can accommodate a relatively appropriate amount of fluid, which has a better effect on regulating the temperature of the battery cell; when the thickness t of the spacer 30 is less than or equal to 6 mm, it is possible to reduce the space occupied by the spacer 30 while having a better temperature regulation effect, thereby improving the energy density of the lithium-ion battery.

[0189] In some embodiments, the battery cell 20 includes a housing 60 for containing electrolyte and positive electrode plates. The housing 60 is provided with a pressure relief mechanism 61 , and an actuation pressure P of the pressure relief mechanism 61 satisfies: 0.5 MPa≤P≤1.8 MPa.

[0190] The pressure relief mechanism 61 can be disposed on any wall of the housing 60. The housing 60 includes a housing 31 and an end cover 32. The housing 31 has an opening, and the end cover 32 covers the opening to form a space for accommodating electrolyte. As an example, the pressure relief mechanism 61 is disposed on the end cover 32; as another example, the pressure relief mechanism 61 is disposed on any wall of the housing 31.

[0191] The pressure relief mechanism 61 is used to discharge substances in the battery cell 20, such as byproducts generated by reactions in the battery cell (such as gases or solids generated by reactions), fragments of positive electrode sheets, fragments of separators, fragments of negative electrode sheets, etc.

[0192] As an example, when the internal pressure of the battery cell 20 reaches a predetermined threshold, it is actuated to release the internal pressure or temperature. When the internal pressure of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism 61 performs an action or a weak structure provided in the pressure relief mechanism 61 is destroyed, thereby forming an opening or channel for internal pressure relief. The threshold design varies according to different design requirements. The threshold may depend on one or more materials of the positive electrode sheet, the negative electrode sheet, the electrolyte and the separator in the lithium-ion battery cell.

[0193] As an example, the pressure relief mechanism 61 may be integrally formed with the housing 60 .

[0194] As an example, the pressure relief mechanism 61 may also be separately provided and connected to the housing 60 .

[0195] The actuation pressure of the pressure relief mechanism 61 is the internal pressure of the battery cell 20 when the pressure relief mechanism 61 is actuated.

[0196] The actuation pressure of the pressure relief mechanism 61 can be adjusted by changing the material of the housing and the thickness of the housing where the pressure relief mechanism 61 is provided.

[0197] The actuating pressure P of the pressure relief mechanism 61 may be 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa or any value within the above range.

[0198] In the battery cell of the present application, since the battery cell has a higher capacity and a higher content of LiFSI, the gas production in the battery cell increases and the pressure in the battery cell increases; by setting the actuation pressure of the pressure relief mechanism 61 to be greater than or equal to 0.5 MPa, it is helpful to reduce the risk of premature actuation of the pressure relief mechanism 61, thereby helping to improve the storage life of the battery cell; by setting the actuation pressure of the pressure relief mechanism 61 to be less than or equal to 1.8 MPa, it is helpful to reduce the risk of the position outside the pressure relief mechanism 61, such as the shell of the battery cell, rupturing before the pressure relief mechanism 61 when the battery cell is thermally runaway, which is helpful to reduce the influence of the thermally runaway battery cell on the adjacent battery cell, thereby helping to improve the reliability of the lithium-ion battery; in addition, the actuation pressure of the pressure relief mechanism 61 is less than or equal to 1.8 MPa, which is helpful to reduce the accumulated heat in the battery cell, the release of the heat in the battery cell, reduce the influence on the adjacent battery cell, and reduce the risk of heat diffusion in the battery.

[0199] In some embodiments, 0.7MPa≤P≤1.4MPa. By setting the actuation pressure of the pressure relief mechanism 61 to meet the above range, it is helpful to further reduce the risk of the pressure relief mechanism 61 actuating the valve to open during normal use of the lithium-ion battery cell, which is helpful to increase the storage time and storage life of the lithium-ion battery cell.

[0200] In some embodiments, the material of the housing 60 includes steel, and the thickness of the housing 60 is 0.1 mm to 0.5 mm.

[0201] In the case where the material of the housing 60 includes steel, the thickness of the housing 60 may be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, or any value within the above range.

[0202] As an example, the housing 60 includes a shell 31 and an end cover 32 , and the thickness of the shell 31 and the end cover 32 both meet the above range.

[0203] In some embodiments, the thickness of the housing 60 is 0.2 mm to 0.3 mm.

[0204] Steel has high strength. By setting the material of the housing 60 to include steel, the pressure relief mechanism 61 has a suitable actuation pressure, which is beneficial to improving the storage life of the battery cell.

[0205] In some embodiments, the material of the housing 60 includes aluminum, and the thickness of the housing 60 is 0.3 mm to 1.0 mm.

[0206] In the case where the material of the housing 60 includes aluminum, the thickness of the housing 60 may be 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, or any value within the above range.

[0207] Aluminum has high strength and relatively suitable processing performance. By setting the material of the shell 60 to include aluminum, it is easy to prepare the shell 60, and the shell 60 also has relatively suitable strength. By setting the thickness of the shell 60 to 0.3mm-1.0mm, during the normal use of the battery cell, the shell 60 is not easy to break, the risk of the pressure relief mechanism 61 actuating the valve in advance is low, and the battery cell has high reliability and long storage time.

[0208] In some embodiments, the thickness of the housing 60 is 0.5 mm to 0.6 mm.

[0209] Aluminum has high strength and relatively suitable processing performance. By setting the material of the shell 60 to include aluminum, it is convenient to prepare the shell 60, and the pressure relief mechanism 61 also has a suitable actuation pressure, which is beneficial to improving the storage life of the lithium-ion battery cell.

[0210] In some embodiments, the lithium-ion battery 10 may further include a housing 11 . The interior of the housing 11 is a hollow structure, and a plurality of battery cells 20 are accommodated in the housing 11 . Figure 1 A possible implementation of the box 11 of the embodiment of the present application is shown, such as Figure 1 As shown, the box body 11 may include two parts, which are respectively referred to as a first box body part 111 and a second box body part 112, and the first box body part 111 and the second box body part 112 are buckled together. The shapes of the first box body part 111 and the second box body part 112 may be determined according to the shapes of the combination of multiple battery cells 20, and at least one of the first box body part 111 and the second box body part 112 has an opening. For example, Figure 1 As shown, the first box body part 111 and the second box body part 112 can both be hollow rectangular parallelepipeds and each has only one open face, the opening of the first box body part 111 and the opening of the second box body part 112 are arranged opposite to each other, and the first box body part 111 and the second box body part 112 are interlocked to form a box body 11 with a closed chamber.

[0211] For example, unlike Figure 1 As shown, only one of the first box body 111 and the second box body 112 may be a hollow cuboid with an opening, while the other may be a plate-shaped body to cover the opening. For example, here, the second box body 112 is a hollow cuboid with only one face as an opening face, and the first box body 111 is a plate-shaped body. Then, the first box body 111 covers the opening of the second box body 112 to form a box body 11 with a closed chamber, which can be used to accommodate multiple battery cells 20. Multiple battery cells 20 are connected in parallel, in series, or in a mixed combination and placed in the box body 11 formed by the first box body 111 and the second box body 112 being buckled together.

[0212] In some embodiments, the lithium-ion battery 10 may also include other structures, which are not described one by one here. For example, the lithium-ion battery 10 may also include a busbar component, which is used to realize electrical connection between multiple battery cells 20, such as parallel connection, series connection, or mixed connection. Specifically, the busbar component can realize electrical connection between the battery cells 20 by connecting the electrode terminals of the battery cells 20. Further, the busbar component can be fixed to the electrode terminals of the battery cells 20 by welding. The electrical energy of multiple battery cells 20 can be further led out through the box 11 through a conductive mechanism.

[0213] [Battery Cell]

[0214] The embodiment of the present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.

[0215] Figure 6 Schematic diagram of a battery cell according to an embodiment of the present application. Figure 6 As shown, the battery cell 20 is a square lithium-ion battery cell. The battery cell 20 includes a housing 31 , an end cover 32 and an electrode assembly 33 disposed in the housing 31 .

[0216] The electrode assembly 33 may be made of a positive electrode sheet, a negative electrode sheet and a separator by a winding process or a lamination process. The electrode assembly 33 may include an electrode assembly body and a tab 331 extending from the electrode assembly body.

[0217] The end cap 32 includes an electrode terminal 322, such as Figure 6 As shown, the end cap 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0218] The battery cell 20 further includes a connecting member 34 for connecting the tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, one connecting member 34 is used to connect the positive tab and the positive electrode terminal, and another connecting member 34 is used to connect the negative tab and the negative electrode terminal.

[0219] [Positive electrode]

[0220] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0221] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0222] The positive electrode current collector may be a metal foil or a composite positive electrode current collector. For example, the positive electrode current collector may be an aluminum foil.

[0223] The composite positive electrode current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite positive electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0224] The positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0225] The positive electrode film layer may also optionally include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0226] [Negative electrode]

[0227] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector.

[0228] The negative electrode current collector may be a metal foil or a composite negative electrode current collector. The negative electrode current collector may be a copper foil. The composite negative electrode current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0229] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0230] The negative electrode film layer may also optionally include a binder. As an example, the binder may include one or more of styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0231] The negative electrode film layer may further optionally include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0232] [Electrolytes]

[0233] The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The present application embodiment has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0234] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0235] The electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobisoxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0236] The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0237] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and may also include performance additives that can improve certain battery properties, such as improving battery overcharge performance, improving battery high temperature or low temperature performance, etc.

[0238] [Isolation film]

[0239] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The embodiment of the present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0240] The material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0241] The positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly through a winding process or a lamination process.

[0242] [Electrical devices]

[0243] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0244] Figure 7 FIG. 1 is a schematic diagram of an electrical device according to an embodiment of the present application. Figure 7 As shown, the present application provides an electrical device 6, including the battery in the above embodiment.

[0245] Optionally, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc. The embodiments of the present application include but are not limited to these.

[0246] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0247] [Example]

[0248] Example 1

[0249] In Example 1, the lithium-ion battery includes a plurality of battery cells and a spacer disposed between the first walls of two adjacent battery cells, the material of the spacer is thermal insulation cotton, and the thermal conductivity of the spacer is 0.03W / (m·K). The first wall of the battery cell is the wall with the largest surface area of ​​the battery cell, the first surface of the spacer is connected to the first wall, the ratio of the area of ​​the first surface to the first wall is 75%, and the thickness t of the spacer is 0.5mm.

[0250] The battery cell includes an electrolyte, wherein the electrolyte salt in the electrolyte includes LiFSI and LiPF6, the concentration of the electrolyte salt is 1 mol / L, the solvent includes ethylene carbonate EC, ethyl methyl carbonate EMC and dimethyl carbonate DMC in a mass ratio of 3:2:5, and the electrolyte also includes an additive vinylene carbonate, and the mass content of the vinylene carbonate is 2wt% based on the total mass of the electrolyte. Based on the total mass of the electrolyte, the mass content A of LiFSI is 4.5wt%.

[0251] In Example 1, the capacity Q of the battery cell is 80 Ah.

[0252] Example 2-3

[0253] The difference between Example 2-3 and Example 1 is that the capacity Q of the battery cell is different and the thickness t of the spacer is different.

[0254] Example 4

[0255] The difference between Example 4 and Example 1 is that the mass content A of LiFSI is different, the capacity Q of the battery cell is different, and the thickness t of the separator is different. The electrolyte salt includes LiFSI but does not include LiPF6. Based on the total mass of the electrolyte, the mass content A of LiFSI is 15.4wt%.

[0256] Example 5

[0257] The difference between Example 5 and Example 1 is that the solvent in the electrolyte is different and the thickness t of the spacer is different. In Example 5, the solvent is ethyl acetate EA, ethylene carbonate EC and dimethyl carbonate DMC in a mass ratio of 2:3:5, and the mass content of EA is 16.9wt% based on the total mass of the electrolyte.

[0258] Example 6

[0259] The difference between Example 6 and Example 4 is that the mass content A of LiFSI is different, the capacity Q of the battery cell is different, and the thickness t of the spacer is different.

[0260] Example 7

[0261] The difference between Example 7 and Example 5 is that the capacity Q of the battery cell is different and the thickness t of the spacer is different.

[0262] Example 8

[0263] The difference between Example 8 and Example 7 is that the structure of the spacer is different. In Example 8, the spacer includes a first plate and a second plate opposite to each other along the thickness direction of the spacer, a flow channel is provided between the first plate and the second plate, and the thickness of the spacer is 3 mm.

[0264] Example 9

[0265] The difference between Example 9 and Example 7 is that the negative electrode active material includes artificial graphite and silicon-carbon composite material, and the mass ratio of artificial graphite to silicon-carbon composite material is 90:6.

[0266] Comparative Example 1

[0267] The difference between Comparative Example 1 and Example 1 is that the thickness t of the spacer is 0.2 mm.

[0268] [Lithium-ion battery preparation]

[0269] (1) Preparation of positive electrode sheets: The positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride (PVDF), and the conductive agent (acetylene black) are mixed evenly in a mass ratio of 97.5:1.5:1, dissolved in a solvent N-methylpyrrolidone (NMP), and stirred thoroughly to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode collector aluminum foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0270] (2) Preparation of negative electrode sheet:

[0271] In the case where the negative electrode active material includes artificial graphite, the negative electrode sheet is prepared by the following method: the negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a mass ratio of 96:1.5:1.5:1.0, and the mixture is stirred and mixed to prepare a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet;

[0272] In the case where the negative electrode active material includes artificial graphite and silicon-carbon composite materials, the negative electrode pole piece is prepared by the following method: the negative electrode active materials artificial graphite and silicon-carbon composite materials, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a mass ratio of 90:6:1.5:1.5:1.0, and the negative electrode slurry is prepared after being fully stirred and mixed; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain the negative electrode pole piece.

[0273] (3) Isolation film: A polyethylene film with a thickness of 12 μm is used.

[0274] (4) Preparation of electrolyte: The specific formula of the electrolyte is shown in each embodiment.

[0275] (5) Preparation of lithium-ion batteries: The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in a shell, and the prepared electrolyte is added. After packaging, standing, forming, aging, and other processes, a lithium-ion battery cell is obtained.

[0276] (6) Assemble the lithium-ion battery cells, separators, etc. to obtain a lithium-ion battery.

[0277] The battery cells in the embodiment and comparative example 1 were prepared into lithium ion batteries and tested. The specific parameters and test results of the embodiment and comparative example are shown in Table 1.

[0278] Table 1 Specific parameters and test results of the embodiments and comparative examples

[0279]

[0280] As shown in Example 1 and Comparative Example 1, when the electrolyte includes LiFSI, setting the thickness t of the spacer to be greater than 0.2 mm can reduce the risk of heat diffusion inside the lithium-ion battery.

[0281] As shown in Examples 1-7, when the LiFSI mass content A is 1 wt% to 20 wt% based on the total mass of the electrolyte and the thickness t of the spacer is greater than 0.2 mm, the risk of thermal diffusion inside the lithium-ion battery is low.

[0282] As shown in Example 1, when the capacity of the battery cell is 80 Ah, based on the total mass of the electrolyte, the LiFSI mass content A is 4.5 wt %, and the thickness t of the spacer is 0.5 mm, the risk of thermal diffusion of the lithium ion battery is low.

[0283] In combination with Examples 1-3, when the capacity of the battery cell is 120Ah, the thickness t of the spacer is set to 1mm, and the risk of thermal diffusion of the lithium-ion battery is low; when the capacity of the battery cell is 180Ah, the thickness t of the spacer is set to 3mm, and the risk of thermal diffusion of the lithium-ion battery is low; in combination with Example 6, when the capacity of the battery cell is 300Ah, the thickness t of the spacer is set to 2mm, and the risk of thermal diffusion of the lithium-ion battery is low.

[0284] As shown in Examples 4 and 7, when the LiFSI mass content A is 15.4 wt % based on the total mass of the electrolyte, the capacity of the battery cell is 180 Ah and 300 Ah, and the thickness t of the spacer is 5 mm, the risk of thermal diffusion in the lithium-ion battery is low.

[0285] As shown in Examples 1-4, by setting the thickness t of the spacer to 5mm, the risk of thermal diffusion of the lithium-ion battery can be effectively reduced; by setting 1.5wt%≤A≤5wt%, 0.5mm≤t≤3mm, the lithium-ion battery can have higher fast charging performance, low thermal diffusion risk and higher energy density; by setting 5wt%≤A≤16wt%, 1mm≤t≤3.5mm, the lithium-ion battery can have higher fast charging performance, low thermal diffusion risk and higher energy density; by setting 50Ah≤Q≤120Ah, 0.5mm≤t≤1mm, the battery cell has a suitable capacity, and the lithium-ion battery has a low thermal diffusion risk, high fast charging performance and high energy density; by setting 120Ah≤Q≤200Ah, 1mm≤t≤5mm, the battery cell has a suitable capacity, and the lithium-ion battery has a low thermal diffusion risk, high fast charging performance and high energy density.

[0286] As shown in Examples 7-8, by providing a spacer including a flow channel, the fluid in the flow channel can better regulate the temperature of the battery cell, thereby further helping to reduce the risk of heat diffusion.

[0287] As shown in Examples 1, 5, 7 and 9, when the electrolyte includes a carboxylic acid ester solvent or the negative electrode active material includes silicon, appropriately increasing the thickness of the spacer is beneficial to reducing the risk of thermal diffusion of the lithium ion battery.

[0288] The following is a brief introduction to the test methods of the physical and chemical parameters and performance parameters involved in the embodiments of the present application. It should be understood that the following test methods are only examples, and other test methods known in the art may also be used for testing.

[0289] 1. LiFSI testing

[0290] The battery cells were disassembled, all the electrolyte was extracted, and the mass content of the electrolyte salt LiFSI in the electrolyte was tested.

[0291] Specifically, the electrolyte salt can be quantitatively analyzed by ion chromatography (IC) according to the standard JY / T020-1996 for the concentration of inorganic components / lithium salt in the electrolyte.

[0292] 2. Test method for thermal diffusion of lithium-ion batteries

[0293] In accordance with GB38031, the battery pack is tested for thermal diffusion at 50°C. If the battery cells adjacent to the battery cells in thermal runaway do not experience thermal runaway (i.e., the pressure relief mechanism is actuated and the valve is opened), the thermal diffusion test is considered to have passed.

[0294] 3. Test of the thickness of the spacer

[0295] The battery cell is disassembled, the spacer is taken out, the thickness of the spacer is measured at multiple positions (for example, 5 positions) along the length direction of the spacer, and the average value of the multiple thicknesses is taken as the thickness t of the spacer.

[0296] 4. Test of thermal conductivity of spacers

[0297] Referring to GBT10294-2008, at a temperature of 25°C, a spacer is placed between two plates at a constant temperature, and the heat flux flowing through the spacer, the thickness of the spacer, and the temperature difference between the plates on both sides are tested. Thermal conductivity = (thickness of spacer × heat flux) / (area of ​​spacer × temperature difference).

[0298] 5. Test of battery cell capacity

[0299] The nominal capacity marked on the battery cell is used as the capacity of the battery cell.

[0300] 6. Testing of water content in lithium phosphate and positive electrode

[0301] The water content of lithium-containing phosphate can be tested according to GB / T 6283-2008.

[0302] The moisture content of the positive electrode can be tested by the following method. Specifically, the fully discharged (0% SOC) battery cell is subjected to the following operations in an environment with a humidity of less than 2: the battery cell is disassembled, the positive electrode is taken out, and it is fully soaked in DMC for more than 2 hours; the DMC is poured out, and the positive electrode is naturally air-dried; several positive electrode pieces are taken, and the mass of the piece m1 is recorded, and the test is performed by the following instrument: fully automatic moisture content tester (model: Swiss Metrohm 874+831), m1 is input into the instrument, and the instrument automatically outputs the moisture content of the positive electrode.

[0303] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A lithium ion battery, characterized in that: include: A battery cell, wherein the battery cell comprises an electrolyte and a positive electrode plate, the positive electrode plate comprises a positive electrode active material, the electrolyte comprises LiFSI, based on the total mass of the electrolyte, the mass content A of the LiFSI satisfies: 1wt%≤A≤20wt%, and the positive electrode active material comprises a lithium-containing phosphate; A spacer, the spacer is arranged between the first walls of two adjacent battery cells, the first wall is the wall with the largest surface area of ​​the battery cell, and the thickness t of the spacer satisfies: 0.2 mm <t≤8mm。 2. The lithium-ion battery according to claim 1, characterized in that 0.5mm≤t≤5mm.

3. The lithium-ion battery according to claim 2, characterized in that: 1.5wt%≤A≤5wt%, 0.5mm≤t≤3mm.

4. The lithium-ion battery according to claim 2, characterized in that: 5wt%≤A≤16wt%, 1mm≤t≤5mm.

5. The lithium ion battery according to any one of claims 1 to 4, characterized in that: The capacity Q of the battery cell satisfies: 50Ah≤Q≤300Ah.

6. The lithium-ion battery according to claim 5, characterized in that: 50Ah≤Q≤130Ah, 0.5mm≤t≤1mm.

7. The lithium-ion battery according to claim 5, characterized in that 130Ah≤Q≤300Ah, 1mm≤t≤5mm.

8. The lithium-ion battery according to claim 7, characterized in that: 1.5wt%≤A≤5wt%, 130Ah≤Q≤300Ah, 1mm≤t≤3.5mm.

9. The lithium-ion battery according to claim 7, characterized in that: 5wt%≤A≤16wt%, 130Ah≤Q≤300Ah, 1.5mm≤t≤5mm.

10. The lithium ion battery according to any one of claims 1 to 9, characterized in that: The electrolyte further includes a carboxylate solvent. Based on the total mass of the electrolyte, the mass content W0 of the carboxylate solvent satisfies: 1wt%≤W0≤80wt%.

11. The lithium ion battery according to claim 10, characterized in that: The carboxylate solvent includes ethyl acetate. Based on the total mass of the electrolyte, the mass content W1 of the ethyl acetate satisfies: 15wt%≤W1≤80wt%, and the thickness t of the spacer satisfies: 1mm≤t≤5mm.

12. The lithium ion battery according to claim 11, characterized in that: 15wt%≤W1≤50wt%, 1mm≤t≤3mm.

13. The lithium ion battery according to claim 10, characterized in that: The carboxylate solvent includes methyl acetate. Based on the total mass of the electrolyte, the mass content W2 of the methyl acetate satisfies: 7wt%≤W2≤60wt%, and the thickness t of the spacer satisfies: 1.5mm≤t≤5mm.

14. The lithium ion battery according to claim 13, characterized in that: 10wt%≤W2≤40wt%, 1.5mm≤t≤3mm.

15. The lithium ion battery according to claim 10, characterized in that: The carboxylic acid ester solvent includes ethyl acetate and methyl acetate. Based on the total mass of the electrolyte, the mass content W1 of the ethyl acetate satisfies: 25wt%≤A≤50wt%, the mass content W2 of the methyl acetate satisfies: 15wt%≤W2≤30wt%, and the thickness t of the spacer satisfies: 1.8mm≤t≤3mm.

16. The lithium ion battery according to any one of claims 10 to 15, characterized in that: The ionic conductivity of the carboxylate solvent is 9 mS / cm to 25 mS / cm, and / or the viscosity of the electrolyte is 1 mm 2 / s~3mm 2 / s.

17. The lithium ion battery according to any one of claims 1 to 16, characterized in that: The electrolyte includes a carbonate solvent, and the carbonate solvent includes at least one of ethylene carbonate, dimethyl carbonate, propylene carbonate or ethyl methyl carbonate.

18. The lithium ion battery according to any one of claims 1 to 17, characterized in that: The electrolyte also includes LiPF6.

19. The lithium ion battery according to any one of claims 1 to 18, characterized in that: The time t for charging the battery cell from 10% SOC to 80% SOC satisfies: t≤30 min.

20. The lithium ion battery according to claim 19, characterized in that The time t for charging the battery cell from 10% SOC to 80% SOC satisfies: t≤17 min.

21. The lithium ion battery according to claim 20, characterized in that The capacity Q of the battery cell satisfies: Q≥130Ah.

22. The lithium ion battery according to any one of claims 1 to 21, characterized in that: The lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate or lithium manganese iron phosphate.

23. The lithium ion battery according to any one of claims 1 to 22, characterized in that: The water content of the positive electrode plate is 50ppm to 300ppm.

24. The lithium ion battery according to any one of claims 1 to 23, characterized in that: The battery cell further includes a negative electrode plate, wherein the negative electrode plate includes a negative electrode active material, and the negative electrode active material includes one or more of a carbon material or a silicon-containing material.

25. The lithium ion battery according to claim 24, characterized in that The negative electrode active material comprises a carbon material and a silicon-containing material, and the mass content of the silicon-containing material is 0.5wt% to 50wt% based on the total mass of the negative electrode active material; The thickness t of the spacer satisfies: 0.5 mm <t≤5mm。 26. The lithium ion battery according to claim 25, characterized in that Based on the total mass of the negative electrode active material, the mass content of the silicon-containing material is 0.5wt% to 10wt%, 0.5mm <t≤3mm。 27. The lithium ion battery according to any one of claims 1 to 26, characterized in that: The first surface of the spacer is connected to the first wall, and the ratio of the area of ​​the first surface to the area of ​​the first wall is 60% to 80%.

28. The lithium ion battery according to any one of claims 1 to 27, characterized in that: The thermal conductivity P of the spacer satisfies: <P≤0.05W / (m·K)。 29. The lithium ion battery according to claim 28, characterized in that 0.005W / (m·K)≤P≤0.03W / (m·K).

30. The lithium ion battery according to any one of claims 1 to 29, characterized in that: The spacer is a heat insulation board.

31. The lithium ion battery according to any one of claims 1 to 30, characterized in that The material of the spacer includes: at least one of thermal insulation wool, plastic foam, glass wool, vacuum insulation board, and silica aerogel.

32. The lithium ion battery according to any one of claims 1 to 29, characterized in that: The spacer includes a flow channel for receiving a fluid to regulate the temperature of the battery cell.

33. The lithium ion battery according to claim 32, characterized in that The spacer includes a first plate and a second plate that are opposite to each other in a thickness direction of the spacer, and the flow channel is disposed between the first plate and the second plate.

34. The lithium ion battery according to claim 33, characterized in that The thickness of the spacer is 3 mm to 6 mm.

35. The lithium ion battery according to any one of claims 1 to 34, characterized in that The battery cell comprises a shell, the shell is used to contain the electrolyte and the positive electrode plate, the shell is provided with a pressure relief mechanism, and the actuation pressure P of the pressure relief mechanism satisfies: 0.5MPa≤P≤1.8Mpa.

36. The lithium ion battery according to claim 35, characterized in that 0.7MPa≤P≤1.4Mpa.

37. The lithium ion battery according to claim 35 or 36, characterized in that: The material of the shell includes steel, and the thickness of the shell is 0.1 mm to 0.5 mm.

38. The lithium ion battery according to claim 37, characterized in that The thickness of the shell is 0.2 mm to 0.3 mm.

39. The lithium ion battery according to claim 35 or 36, characterized in that: The material of the shell includes aluminum, and the thickness of the shell is 0.3 mm to 1.0 mm.

40. The lithium ion battery according to claim 39, characterized in that The thickness of the shell is 0.5 mm to 0.6 mm.

41. An electrical device, characterized in that: Comprising a lithium ion battery according to any one of claims 1-40.

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