Battery cell, battery, and electrical apparatus

Abstract

Provided are a battery cell (20), a battery (10), and an electrical apparatus. The battery cell (20) comprises: an electrode assembly (22); a casing (21); an end cover (23), the casing (21) and the end cover (23) forming a space for accommodating the electrode assembly (22), and the end cover (23) being provided with a pressure relief mechanism (26); and an electrolyte, the electrolyte comprising a solvent and an electrolyte salt, the solvent comprising dimethyl carbonate, and the electrolyte salt comprising lithium bis(fluorosulfonyl)imide. In the thickness direction of the end cover (23), a gap D between the electrode assembly (22) and an inner side of the pressure relief mechanism (26) satisfies: 4 mm≤D≤10 mm. The capacity Q of the battery cell (20) satisfies: 30 Ah≤Q≤40 Ah. The battery cell (20) has the capability for fast charging and has high energy density and high reliability.

Description

Battery cell, battery, and electric device Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411060661.3, filed on August 5, 2024, entitled “Battery cell, battery, and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, and more particularly, to a battery cell, a battery, and an electric device. BACKGROUND

[0003] New energy industry is attracting more and more attention. In the new energy industry, battery technology is an important factor for its development.

[0004] The development of battery technology needs to consider various design factors, such as energy density, cycle life, capacity, fast charging performance, reliability, etc. Therefore, how to provide a battery cell with fast charging capability, high reliability and high energy density is an urgent technical problem to be solved. SUMMARY

[0005] The present application is made in view of the above-mentioned problem, and aims to provide a battery cell with fast charging capability, high reliability and high energy density.

[0006] To achieve the above-mentioned purpose, the present application provides a battery cell, a battery, and an electric device.

[0007] In a first aspect, a battery cell is provided, comprising: an electrode assembly; a shell; an end cover, the shell and the end cover form a space containing the electrode assembly, the end cover is provided with a pressure relief mechanism; an electrolyte, the electrolyte comprises a solvent and an electrolyte salt, the solvent comprises dimethyl carbonate, and the electrolyte salt comprises a lithium bisfluorosulfonylimide salt; an electrode assembly contained in the shell; along the thickness direction of the end cover, the gap D between the electrode assembly and the inner side of the pressure relief mechanism satisfies: 4mm≤D≤10mm; the capacity Q of the battery cell satisfies: 30Ah≤Q≤40Ah.

[0008] In the embodiment of the present application, the capacity Q of the battery monomer satisfies: 30 Ah≤Q≤40 Ah; in the battery monomer, due to the fact that the electrolyte includes dimethyl carbonate and lithium bisfluorosulfonylimide salt, the battery monomer has fast charging capability, and in the case that the battery monomer has thermal runaway, more gas will be generated in the battery monomer; by setting the gap D between the electrode assembly and the inner side of the pressure relief mechanism of the end cover in the thickness direction of the end cover, D≥4 mm, there is enough space in the battery monomer to facilitate the opening of the valve of the pressure relief mechanism, which can reduce the risk of the electrode terminal of the battery monomer being separated from the shell and the shell being broken; by setting D≤10 mm, the waste of the space in the battery monomer can be reduced, which is conducive to improving the energy density of the battery monomer. Therefore, the battery monomer of the embodiment of the present application has fast charging capability, high energy density and high reliability.

[0009] In a possible implementation, 6 mm≤D≤8 mm. In the case of D≥6 mm, there is enough space in the battery monomer, on the one hand, enough space can be provided to accommodate the gas generated in the battery monomer, and on the other hand, there is enough space in the battery monomer to facilitate the opening of the valve of the pressure relief mechanism, thereby facilitating the discharge of the high-temperature and high-pressure substances inside the battery monomer when the battery monomer has thermal runaway, reducing the risk of the electrode terminal of the battery monomer being separated from the shell and the shell being broken; in the case of D≤8 mm, the waste of the space in the battery monomer can be reduced. Therefore, by setting 6 mm≤D≤8 mm, the volume energy density and reliability of the battery monomer can be considered.

[0010] In a possible implementation, the mass content A of the dimethyl carbonate satisfies: 20wt%≤A≤60wt%, based on the total mass of the electrolyte; and / or, the mass content B of the lithium bisfluorosulfonylimide salt satisfies: 2wt%≤B≤16wt%, based on the total mass of the electrolyte.

[0011] In the above technical solution, the mass content of the dimethyl carbonate and the mass content of the lithium bisfluorosulfonylimide salt satisfy the above range, which is conducive to improving the fast charging performance of the battery monomer.

[0012] In a possible implementation, 20wt%≤A≤45wt%; and / or, 2.5wt%≤B≤11wt%. In the above technical solution, the mass content of the lithium bisfluorosulfonylimide salt and the dimethyl carbonate satisfies the above range, which can further consider the fast charging performance and reliability of the battery monomer.

[0013] In a possible implementation, the mass content ratio A:B of the dimethyl carbonate and the lithium bisfluorosulfonylimide salt satisfies: 3≤A:B≤16.

[0014] In the technical solution, 3≤A:B≤16, so that the battery monomer has good fast charging performance and less gas production, and the fast charging performance and reliability of the battery monomer can be considered.

[0015] In a possible implementation, 3≤A:B≤10. In this way, the battery monomer has good fast charging performance and high reliability.

[0016] In a possible implementation, in the battery monomer, the ratio C of the mass of the electrolyte to the capacity of the battery monomer satisfies: C≤1.6 g / Ah. In this way, the mass of the electrolyte in the battery monomer is small, which is beneficial to reduce the gas production in the battery monomer when the battery monomer is in thermal runaway, reduce the severity when the battery monomer is in thermal runaway, and further improve the reliability of the battery monomer.

[0017] In a possible implementation, 1.2 g / Ah≤C≤1.4 g / Ah. In the case of C≤1.4 g / Ah, the mass of the electrolyte in the battery monomer is small, which is beneficial to further improve the reliability of the battery monomer; in the case of C≥1.2 g / Ah, the mass of the electrolyte can meet the normal work of the battery monomer, and the influence on the cycle performance and other electrical properties of the battery monomer can be reduced. Therefore, the technical solution is beneficial to consider the reliability and electrical properties of the battery monomer.

[0018] In a possible implementation, in the battery monomer, the ratio E of the mass of the remaining electrolyte to the capacity of the battery monomer satisfies: 0.7 g / Ah≤E≤1.1 g / Ah. In the technical solution, the ratio of the mass of the remaining electrolyte to the capacity of the battery monomer is in the range of 0.7 g / Ah to 1.1 g / Ah within 1000 cycles of the battery monomer.

[0019] In a possible implementation, along the thickness direction of the end cover, the size H of the battery monomer satisfies: 90 mm≤H≤120 mm. In this way, the battery monomer has a suitable capacity and height, and the battery monomer has a more suitable energy density.

[0020] In a possible implementation, in the battery monomer, the mass K of the electrolyte satisfies: 30 g≤K≤60 g. In this way, the battery monomer has good fast charging performance.

[0021] In a possible implementation, in the battery monomer, 35 g≤K≤50 g. In this way, the battery monomer has good fast charging performance and high reliability.

[0022] In a possible implementation, the mass P of the electrolyte remaining in the battery monomer within 1000 cycles of the battery monomer satisfies: 22g≤P≤36g. In this technical solution, the mass of the electrolyte remaining in the battery monomer within 1000 cycles of the battery monomer is within the range of 22g to 36g.

[0023] In a possible implementation, in the battery monomer, the mass K of the electrolyte and the size D of the gap satisfy: 4g / mm≤K / D≤11g / mm. In the case of K / D≥4g / mm, the battery monomer has a higher volumetric energy density; in the case of K / D≤11g / mm, the risk of shell rupture and electrode terminal separation from the shell of the battery monomer when the battery monomer is in thermal runaway can be reduced, and the battery monomer has higher reliability. Therefore, by setting 4g / mm≤K / D≤11g / mm, the volumetric energy density and reliability of the battery monomer can be considered.

[0024] In a possible implementation, 6g / mm≤K / D≤8.5g / mm. In this way, the volumetric energy density and reliability of the battery monomer can be further considered.

[0025] In a possible implementation, the electrode assembly includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet has a compaction density greater than or equal to 3.55g / cm 3 , and / or the negative electrode sheet has a compaction density greater than or equal to 1.5g / cm 3 .

[0026] In a possible implementation, the compaction density of the positive electrode sheet is 3.55g / cm 3 ~3.7g / cm 3 , and / or the compaction density of the negative electrode sheet is 1.5g / cm 3 ~1.7g / cm 3 .

[0027] In the above technical solution, the positive electrode sheet and / or the negative electrode sheet has a higher compaction density, which is conducive to improving the energy density of the battery monomer; in addition, when the compaction density of the positive electrode sheet and / or the negative electrode sheet is high, the demand for electrolyte of the battery monomer is reduced, which is conducive to reducing the electrolyte injection coefficient of the battery monomer, and further reducing the gas production amount of the battery monomer when the battery monomer is in thermal runaway, reducing the severity of the battery monomer when the battery monomer is in thermal runaway, and improving the reliability of the battery monomer.

[0028] In a possible implementation, within 1000 cycles of the battery monomer, the compaction density of the positive electrode sheet is 3.35g / cm 3 ~3.69g / cm 3, and / or the compaction density of the negative electrode sheet is 1.3 g / cm 3 ~1.65 g / cm 3 After a certain number of charge and discharge cycles, the positive electrode sheet and the negative electrode sheet swell, and the compaction densities of the positive electrode sheet and the negative electrode sheet change.

[0029] In a possible implementation, the porosity of the positive electrode sheet is 22%~26%, and / or the porosity of the negative electrode sheet is 23%~27%. In this way, the positive electrode sheet and / or the negative electrode sheet have a lower porosity, which is beneficial to reducing the amount of electrolyte required in the battery cell, thereby reducing the gas production amount and the severity of thermal runaway of the battery cell, and improving the reliability of the battery cell.

[0030] In a possible implementation, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the mass G0 of the positive electrode film layer and the gap D satisfy: 15 g / mm≤G0 / D≤42 g / mm.

[0031] In the case of G0 / D≥15 g / mm, the battery cell has a higher energy density; in the case of G0 / D≤42 g / mm, the battery cell has a higher reliability. By setting 15 g / mm≤G0 / D≤42 g / mm, the battery cell can balance the energy density and the reliability.

[0032] In a possible implementation, 18 g / mm≤G0 / D≤28 g / mm. In this way, the energy density and the reliability of the battery cell are more balanced, and the battery cell has a better comprehensive performance.

[0033] In a possible implementation, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes lithium nickel oxide or metal phosphate. In this way, the battery cell including lithium nickel oxide can have a higher energy density, and the battery cell including metal phosphate has a higher reliability.

[0034] In a possible implementation, the chemical formula of the lithium nickel oxide satisfies: Li 1+a [Ni x Co y Mn z M b ]O 2- cM includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.2 >= a >= -0.2, 1 > x > 0.7, 0.3 > y > 0, 0.3 > z > 0, 0.3 >= b >= 0, 0.5 >= c >= 0. The positive electrode active material has a high content of Ni, which is beneficial to improve the energy density of the battery cell.

[0035] In a possible implementation, in the battery cell, the gram weight per unit area of the positive electrode active material is 15 mg / cm 2 ~ 23 mg / cm 2 In the technical solution, the gram weight of the positive electrode active material is large, and the battery cell has a higher energy density.

[0036] In a possible implementation, the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes graphite and a silicon-containing material, the silicon-containing material includes at least one of elemental silicon, silicon-oxygen composite, silicon-carbon composite, silicon-nitrogen composite, silicon-containing alloy or silicon-oxygen-carbon composite material, and the graphite includes at least one of natural graphite or artificial graphite. The negative electrode active material is beneficial to improve the energy density of the battery cell.

[0037] In a possible implementation, the silicon-containing material includes silicon-carbon composite, and the mass content of silicon in the silicon-carbon composite is 40wt%~60wt% based on the total mass of the silicon-containing material. The mass content of silicon in the silicon-carbon composite is in the above range, the electrode assembly has a relatively appropriate expansion rate, and the normal use of the battery cell is facilitated.

[0038] In a possible implementation, the mass content of the silicon-containing material in the negative electrode active material is 1wt%~20wt% based on the total mass of the negative electrode active material. In this way, the silicon-containing material in the negative electrode active material has a suitable mass content, so that the electrode assembly has a relatively appropriate expansion rate, and the normal use of the battery cell is facilitated.

[0039] In a possible implementation, in the battery cell, the gram weight per unit area of the negative electrode active material is 8 mg / cm 2 ~ 13 mg / cm 2 In the technical solution, the gram weight of the negative electrode active material is large, and the battery cell has a higher energy density.

[0040] In a possible implementation, the electrode assembly further comprises a separator film, the separator film is arranged between the positive electrode tab and the negative electrode tab, and the separator film comprises a base film and a ceramic coating arranged on a side of the base film facing the positive electrode tab. In this way, the separator film has a small amount of electrolyte absorption, which is conducive to reducing the mass of electrolyte in the battery cell, thereby reducing the amount of gas generated and the degree of severity when the battery cell is in thermal runaway, and improving the reliability of the battery cell.

[0041] In a possible implementation, the porosity of the separator film is 30% to 45%. In this way, the separator film has a low porosity, and the separator film is not easily punctured, and the battery cell has high reliability. Meanwhile, the arrangement of the electrolyte is conducive to improving the ion transmission rate. In the case where the separator film cooperates with the electrolyte, the battery cell has good fast-charging performance and high reliability.

[0042] In a possible implementation, the end cover comprises an end cover body, and the pressure relief mechanism is arranged on the inner side or the outer side of the end cover body. By arranging the pressure relief mechanism on the inner side of the end cover body, the risk of rupture of the pressure relief mechanism during normal use of the battery cell can be reduced, which is conducive to improving the long-term reliability of the pressure relief mechanism. By arranging the pressure relief mechanism on the outer side of the end cover body, the preparation difficulty of the pressure relief mechanism can be reduced.

[0043] In a possible implementation, the end cover body is provided with a score groove, and the area defined by the score groove forms the pressure relief mechanism. In this way, the preparation of the pressure relief mechanism is facilitated, and the risk of interference between the pressure relief mechanism and the components in the battery cell can be reduced.

[0044] In a possible implementation, the area S defined by the pressure relief mechanism and the area S0 of the end cover satisfy: 25%≤S / S0≤50%. In the case where S / S0≥25%, the pressure relief mechanism is more likely to rupture when the battery cell is in thermal runaway, thereby facilitating the end cover to have a larger tearing opening, and facilitating the discharge of high-temperature and high-pressure substances in the battery cell. In the case where S / S0≤50%, the interference of the pressure relief mechanism on the connection between the end cover and the shell can be reduced, and the connection between the end cover and the shell is facilitated.

[0045] In a possible implementation, the area S of the pressure relief mechanism and the capacity Q of the battery cell satisfy: 12mm 2 / Ah≤S / Q≤20mm 2 / Ah. In this way, the battery cell with different capacities can be provided with the pressure relief mechanism with different area sizes, which is conducive to the discharge of high-temperature and high-pressure substances when the battery cell is in thermal runaway, and facilitates the connection between the shell and the end cover.

[0046] In a possible implementation, the area S of the pressure relief mechanism is greater than or equal to 500 mm 2 In this way, when the battery cell is in thermal runaway, the pressure relief mechanism is more likely to break, thereby facilitating the end cover to have a larger tearing opening and facilitating the discharge of high-temperature and high-pressure substances inside the battery cell.

[0047] In a possible implementation, the area S of the pressure relief mechanism satisfies: 600 mm 2 ≤ S ≤ 800 mm 2 When S ≥ 600 mm 2 , the pressure relief mechanism is more likely to break when the battery cell is in thermal runaway, thereby facilitating the end cover to have a larger tearing opening and facilitating the discharge of high-temperature and high-pressure substances inside the battery cell; and when S ≤ 800 mm 2 , the interference of the pressure relief mechanism on the connection between the end cover and the shell can be reduced, thereby facilitating the connection between the end cover and the shell.

[0048] In a possible implementation, the voltage platform of the battery cell is 3.5 V to 3.7 V. When the voltage window of the battery cell is in the above range, the battery cell has a higher energy density.

[0049] In a possible implementation, the solvent further includes methyl ethyl carbonate and ethylene carbonate, and the electrolyte salt further includes lithium hexafluorophosphate. In the above technical solution, the electrolyte has a lower viscosity and a higher ionic conductivity, thereby facilitating the improvement of the fast-charging performance of the battery cell.

[0050] In a possible implementation, the electrolyte further includes an additive, and the additive includes at least one of fluoroethylene carbonate or vinylene carbonate. The addition of the additive can reduce the decomposition of the electrolyte, thereby facilitating the improvement of the fast-charging performance of the battery cell.

[0051] In a possible implementation, the battery cell further includes a current collecting member, the current collecting member is accommodated in the shell, and the current collecting member is located between the electrode assembly and the end cover in the thickness direction of the end cover. The current collecting member is electrically connected to the tab of the electrode assembly and the shell. In this way, the current collecting member can achieve the electrical connection between the electrode assembly and the shell.

[0052] In a possible implementation, the inner side of the shell is provided with a limiting portion, which is located between the electrode assembly and the end cover along the thickness direction of the end cover, and the current collecting member abuts against one side of the limiting portion facing the electrode assembly. The limiting portion not only limits the movement of the end cover towards the electrode assembly, but also facilitates the realization of a proper gap size between the electrode assembly and the pressure relief mechanism of the end cover, thereby providing a space for the actuation of the pressure relief mechanism.

[0053] In a possible implementation, the battery monomer further comprises a sealing member arranged between the end cover and the shell. The arrangement of the sealing member facilitates the improvement of the sealing performance of the battery monomer, thereby facilitating the improvement of the reliability of the battery monomer.

[0054] In a second aspect, a battery is provided, which comprises the battery monomer in the first aspect and any possible implementation thereof.

[0055] In a third aspect, a power consuming device is provided, which comprises the battery in the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of the drawings.

[0057] FIG. 1 is a schematic view of a battery monomer according to an embodiment of the present application;

[0058] FIG. 2 is a schematic view of a cross section of the battery monomer in FIG. 1 along the direction of A-A;

[0059] FIG. 3 is a schematic view of an enlarged view of region C in FIG. 2;

[0060] FIG. 4 is an exploded structural schematic view of a battery monomer according to an embodiment of the present application;

[0061] FIG. 5 is a schematic view of the force on the pressure relief mechanism arranged inside the end cover body according to an embodiment of the present application;

[0062] FIG. 6 is a schematic view of the force on the pressure relief mechanism arranged outside the end cover body according to an embodiment of the present application;

[0063] FIG. 7 is a structural schematic view of an end cover according to an embodiment of the present application;

[0064] FIG. 8 is a structural schematic view of a current collecting member according to an embodiment of the present application;

[0065] FIG. 9 is a schematic view of a battery according to an embodiment of the present application;

[0066] FIG. 10 is a schematic view of a power consuming device according to an embodiment of the present application.

[0067] Reference signs: 1: vehicle; 10: battery; 30: controller; 40: motor; 3: case; 31: first case portion; 32: second case portion; 20: battery cell; 21: housing; 22: electrode assembly; 23: end cap; 24: current collecting member; 25: electrode terminal; 26: pressure relief mechanism; 261: score groove; 262: notch; 240: current collecting body; 241: elastic portion; 242: current collecting tab; 2411: first tab; 2412: second tab; 243: center portion; 2414: abutting portion; 231: end cap body; 232: protrusion; 211: stopper; 212: seal; 27: current collecting disk; 28: insulating member. DETAILED DESCRIPTION

[0068] The embodiments of the battery cell, battery, and power consuming device according to the present application are explained in detail, with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed explanation is omitted. For example, there will be cases where detailed explanation of matters known well, and repetitive explanation of substantially identical structures are omitted. This is in order to avoid the following explanation from becoming unnecessarily lengthy, and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following explanation are provided in order for those skilled in the art to fully understand the present application, and are not intended to define the subject matter recited in the claims.

[0069] The "ranges" disclosed herein are defined with their lower and upper limits, and a given range is defined with a lower limit and an upper limit. The lower and upper limits define the boundaries of a particular range. Ranges defined by these methods can be inclusive or exclusive of the end values, and are combinable to form additional ranges. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing each and every intervening real number between the upper and lower limits of that range. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand way of describing those numerical combinations. Also, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on.

[0070] If there is no special indication, all the embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0071] If there is no special indication, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0072] If there is no special indication, all the steps of the present application can be performed in sequence or randomly, and the preferred is performed in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0073] The battery monomer in the embodiment of the present application can refer to the smallest structural unit of the battery. A plurality of battery monomers can first form a battery module, and then form a battery from the battery module; or a plurality of battery monomers can directly form a battery.

[0074] The battery monomer in the embodiment of the present application refers to a battery monomer capable of reversible charging and discharging.

[0075] In the charging process of the battery monomer, lithium ions are released from the positive active material, move and embed into the negative electrode; and in the discharging process, lithium ions are released from the negative electrode, move and embed into the positive active material.

[0076] It should be understood that the "embedding" process described in the present application refers to the process of lithium ions embedding in the positive active material or the negative electrode due to electrochemical reaction, and the "release" and "de-embedding" process described in the present application refers to the process of lithium ions releasing from the positive active material or the negative electrode due to electrochemical reaction.

[0077] The development of battery technology needs to consider many design factors, such as energy density, cycle life, discharge capacity, charge-discharge rate, fast charging capability, reliability, first circle charging capacity, etc. With the wide use of batteries, the requirement for the fast charging performance of the battery is also gradually improved. In the related technology, by adding dimethyl carbonate and lithium bisfluorosulfonylimide salt in the electrolyte, the transmission and diffusion of lithium ions are promoted, and the fast charging performance of the battery monomer is improved. However, the applicant found in the process of researching the battery monomer comprising the above-mentioned electrolyte that in the case of thermal runaway of the battery monomer, the gas production of the battery monomer comprising the above-mentioned electrolyte is more, the degree of thermal runaway is more violent, the pressure relief mechanism is difficult to open in time, the phenomenon of electrode terminal separation from the shell and flying out, shell rupture occurs, which is not conducive to the improvement of the reliability of the battery monomer.

[0078] In the related art, in some processing manners, in order to improve the reliability of the battery monomer, a water cooling plate is arranged between the surfaces with the largest surface area of adjacent battery monomers to cool / insulate the battery monomers, so as to reduce the influence of the thermal runaway battery monomer on adjacent battery monomers, and improve the reliability of the battery including the battery monomers; in other processing manners, a fire-fighting pipeline is arranged in the battery, and when the battery monomer in the battery experiences thermal runaway, the fire-fighting medium in the fire-fighting pipeline flows out to cool the battery monomer experiencing thermal runaway, thereby reducing the influence of the thermal runaway battery monomer on adjacent battery monomers. In the related art, the design is mainly from the perspective of the battery to improve the reliability of the battery monomer, and there is less research on the design from the perspective of the battery monomer itself to improve the reliability of the battery monomer.

[0079] Therefore, the battery monomer not only has the fast charging performance, but also can timely open the valve of the pressure relief mechanism when the battery monomer experiences thermal runaway, thereby reducing the risk of shell rupture and electrode terminal separation from the shell, and has high reliability. In addition, the gap D is in the above range, the utilization rate of the internal space of the battery monomer is high, and the battery monomer also has high energy density.

[0080] [Battery monomer]

[0081] FIG. 1 is a schematic diagram of a battery monomer according to an embodiment of the present application, FIG. 2 is a schematic diagram of a cross section of the battery monomer in FIG. 1 along the A-A direction, FIG. 3 is an enlarged schematic diagram of the C region in FIG. 2, and FIG. 4 is an exploded structural schematic diagram of a battery monomer according to an embodiment of the present application.

[0082] In combination with FIGS. 1 to 4, the embodiment of the present application provides a battery monomer 20, which includes a shell 21, an end cover 23, an electrode assembly 22, and an electrolyte.

[0083] The shell 21 can be a hollow structure with an opening at one end, or a hollow structure with openings at both ends. As an example, in combination with FIG. 4, the shell 21 is a hollow structure with an opening at one end, and the end cover 23 is used to cover the opening of the shell 21.

[0084] The material of the shell 21 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. The shell 21 can be various shapes, such as a cylinder, a cuboid, etc. As an example, in the embodiment of the present application, the material of the shell 21 is steel, and the shell 21 is a cylinder.

[0085] The electrode assembly 22 is a component in which electrochemical reactions occur in the battery cell 20. The electrode assembly 22 can include a positive electrode tab, a negative electrode tab, and a separator film between the positive electrode tab and the negative electrode tab. The positive electrode tab includes a positive electrode current collector and a positive electrode film layer coated on a surface of the positive electrode current collector, and the current collector on which the positive electrode film layer is not coated protrudes from the current collector on which the positive electrode film layer is coated, and the current collector on which the positive electrode film layer is not coated serves as a positive electrode tab. The negative electrode tab includes a negative electrode current collector and a negative electrode film layer coated on a surface of the negative electrode current collector, and the current collector on which the negative electrode film layer is not coated protrudes from the current collector on which the negative electrode film layer is coated, and the current collector on which the negative electrode film layer is not coated serves as a negative electrode tab. The positive electrode tab, the separator film, and the negative electrode tab can form the electrode assembly 22 by being wound or stacked.

[0086] As an example, the positive electrode tab, the separator film, and the negative electrode tab are wound to form the electrode assembly 22, and a region in which the positive electrode film layer and / or the negative electrode film layer are provided in the electrode assembly 22 after being wound can be referred to as a main body portion of the electrode assembly 22, and a region in which the positive electrode film layer and the negative electrode film layer are not provided can be referred to as a tab of the electrode assembly 22. As an example, the positive electrode tab and the negative electrode tab are provided at both ends of the electrode assembly 22 in the thickness direction of the end cap 23.

[0087] The end cap 23 forms a space for accommodating the electrode assembly 22 together with the case 21. As an example, the case 21 has an opening, and the end cap 23 is coupled to the opening to insulate the inside of the battery cell 20 from the outside. The end cap 23 is coupled to the opening of the case 21, and the end cap 23 and the case 21 together define a space for accommodating the electrode assembly 22 and the electrolyte.

[0088] The shape of the end cap 23 can be adapted to the shape of the case 21, for example, the case 21 has a rectangular plate shape that is adapted to the shape of the case 21, and the case 21 has a cylindrical shape, and the end cap 23 has a circular plate shape that is adapted to the shape of the case 21. The material of the end cap 23 can be various, for example, the end cap 23 can be a metal material such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cap 23 can be the same as or different from the material of the case 21. As an example, the material of the end cap 23 is copper.

[0089] In the battery cell 20, the end cover 23 can be one or two. If the shell 21 is a hollow structure with an opening at one end, one end cover 23 is correspondingly arranged; if the shell 21 is a hollow structure with openings at both ends, two end covers 23 are correspondingly arranged, covering the two openings of the shell 21, one of the positive and negative electrode tabs of the electrode assembly 22 is electrically connected with one end cover 23, and the other is electrically connected with the shell 21. In the embodiment in which the shell 21 is a hollow structure with an opening at one end, the end of the shell 21 away from the end cover 23 can be provided with an electrode terminal 25, which is insulatedly connected with the shell 21, one of the positive and negative electrode tabs of the electrode assembly 22 is electrically connected with the shell 21, and the other is electrically connected with the electrode terminal 25.

[0090] The end cover 23 is provided with a pressure relief mechanism 26. The pressure relief mechanism 26 is an element or component for actuating when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold value to release the internal pressure or temperature of the battery cell 20. The predetermined threshold value can be adjusted according to different design requirements. For example, the predetermined threshold value can depend on the material of one or more of the positive and negative electrode tabs, the electrolyte and the separator in the battery cell.

[0091] "Actuating" means that the pressure relief mechanism 26 generates an action or is activated to a certain state, so that the internal pressure and temperature of the battery cell 20 can be released. The action generated by the pressure relief mechanism 26 can include but is not limited to: at least part of the pressure relief mechanism 26 is broken, broken, torn or opened, etc. When the pressure relief mechanism 26 is actuated, the high-temperature and high-pressure substances inside the battery cell 20 will be discharged outward from the actuated part as the discharge. In this way, the battery cell 20 can be relieved of pressure and temperature under controllable pressure or temperature, thereby reducing the risk of more serious accidents.

[0092] The discharge from the battery cell 20 mentioned in the embodiments of the present application includes but is not limited to: electrolyte, dissolved or split positive and negative electrode tabs, fragments of the separator, high-temperature and high-pressure gas generated by reaction, flame, etc.

[0093] The pressure relief mechanism 26 can be a separate structure from the end cover 23, for example, the pressure relief mechanism 26 is an independent component mounted on the end cover 23. The pressure relief mechanism 26 can be a component such as a rupture disc, a burst disc, a gas valve, a pressure relief valve or a safety valve mounted on the end cover 23, and can specifically adopt a pressure-sensitive or temperature-sensitive element or structure.

[0094] The pressure relief mechanism 26 can be integrated with the end cover 23, for example, the pressure relief mechanism 26 is part of the end cover 23. For example, the pressure relief mechanism can be formed by providing a notch on the end cover 23, the thickness of the notch is significantly smaller than the thickness of other areas of the end cover 23. The notch is the weakest position of the pressure relief mechanism. When the gas generated by the battery cell 20 is too much to cause the internal pressure to rise and reach a threshold value, or the heat generated by the internal reaction of the battery cell 20 causes the internal temperature of the battery cell 20 to rise and reach a threshold value, the pressure relief mechanism 26 can break at the notch to cause the inside and outside of the battery cell 20 to communicate, and the gas pressure and temperature are released outward through the cracking of the pressure relief mechanism 26, thereby avoiding the explosion of the battery cell 20. As an example, a notch groove is provided on the end cover 23, and the area defined by the notch groove forms the pressure relief mechanism 26.

[0095] The electrolyte includes a solvent and an electrolyte salt, the solvent includes dimethyl carbonate, and the electrolyte salt includes lithium bisfluorosulfonylimide.

[0096] The dimethyl carbonate DMC has a low viscosity, which is conducive to the transmission and diffusion of active ions (such as lithium ions); the lithium bisfluorosulfonylimide LiFSI has a high ionic conductivity, which is conducive to the transmission and diffusion of active ions (such as lithium ions). The inclusion of DMC and LiFSI in the electrolyte facilitates ion transmission, and the battery cell has good fast-charging performance.

[0097] In the charging and discharging cycle of the battery cell, the battery cell generates heat, and in the case of heat generation of the battery cell, the DMC undergoes decarboxylation to produce CO2; in addition, in the case of thermal runaway of the battery cell, the temperature inside the battery cell further increases (for example, the temperature inside the battery cell can reach 200°C and higher), and at high temperatures, the LiFSI will undergo a strong exothermic reaction with the lithium-embedded negative electrode (including the graphite negative electrode after lithium embedding becomes LiC6), and a large amount of SO2 and NO2 gas will be generated. Therefore, in the case of thermal runaway of the battery cell, a large amount of gas is generated inside the battery cell, and the degree of thermal runaway is more severe, the risk of shell rupture and electrode terminal separation from the shell flying out is higher; in addition, in the case of shell rupture and electrode terminal separation from the shell flying out, it will have an adverse effect on the adjacent battery cell.

[0098] In the thickness direction of the end cover 23, the gap D between the electrode assembly 22 and the inner side of the pressure relief mechanism 26 satisfies: 4mm≤D≤10mm.

[0099] The inner side of the pressure relief mechanism 26 can refer to, in the thickness direction of the end cover 23, the end of the pressure relief mechanism 26 close to the electrode assembly 22.

[0100] The gap D between the electrode assembly 22 and the inner side of the pressure relief mechanism 26 can be the distance between the electrode assembly 22 and the pressure relief mechanism 26 along the thickness direction of the end cover 23, for example, the z direction in FIG. 3.

[0101] As an example, the gap D can be determined as follows: in the region defined by the pressure relief mechanism 26, 5 points are taken on the side surface of the region defined by the pressure relief mechanism 26 close to the electrode assembly 22 along the direction z; 5 points are taken on the end of the electrode assembly 22 close to the end cover 23 along the direction z; the average value of the distances between the 5 points taken on the pressure relief mechanism 26 and the 5 points taken on the electrode assembly 22 is calculated, and the average value is taken as the value of the gap D.

[0102] D can be 4 mm, 5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 9 mm, 10 mm, or any value within the above range.

[0103] When D≥4 mm, there is more accommodation space between the electrode assembly 22 and the end cover 23. Due to the arrangement of the electrolyte described above, the battery monomer 20 generates more gas and the degree of thermal runaway is more severe when the battery monomer 20 is in thermal runaway. The space between the electrode assembly 22 and the end cover 23 can accommodate the gas generated inside the battery monomer 20, and the space can also provide space for the actuation of the pressure relief mechanism 26, so as to facilitate the opening of the pressure relief mechanism 26 and the discharge of the high-temperature and high-pressure discharge in the battery monomer 20 when the battery monomer is in thermal runaway, thereby reducing the risk of shell rupture and electrode terminal flying out of the shell.

[0104] When D≤10 mm, the waste of the space inside the battery monomer can be reduced, the utilization rate of the internal space of the battery monomer can be improved, and the energy density of the battery monomer can be improved.

[0105] The capacity Q of the battery monomer satisfies: 30 Ah≤Q≤40 Ah.

[0106] Q can be 30 Ah, 33 Ah, 35 Ah, 37 Ah, 40 Ah, or any value within the above range.

[0107] In the embodiment of the present application, the capacity Q of the battery monomer satisfies: 30 Ah≤Q≤40 Ah; in the battery monomer, due to the fact that the electrolyte includes dimethyl carbonate and lithium bisfluorosulfonylimide salt, the battery monomer has a fast charging capability; by setting the gap D≥4 mm between the electrode assembly 22 and the inner side of the pressure relief mechanism of the end cover 23 along the thickness direction of the end cover 23, there is sufficient space in the battery monomer to facilitate the opening of the valve of the pressure relief mechanism, which can reduce the risk of the electrode terminal of the battery monomer being separated from the shell 21 and the shell 21 being broken when the battery monomer is in thermal runaway; by setting D≤10 mm, the waste of the space in the battery monomer can be reduced, the space utilization rate in the battery monomer is improved, and thus the energy density of the battery monomer is improved. Therefore, the battery monomer of the embodiment of the present application has a fast charging capability, a high energy density, and high reliability.

[0108] In some embodiments, the size D of the gap satisfies: 6 mm≤D≤8 mm.

[0109] In the case of D≥6 mm, there is a large gap between the electrode assembly 22 and the inner side of the pressure relief mechanism 26, and there is a large space between the electrode assembly 22 and the end cover 23. On the one hand, there is sufficient space to accommodate the gas generated inside the battery monomer 20, and on the other hand, it is convenient for the valve of the pressure relief mechanism 26 to open, thereby facilitating the discharge of the high-temperature and high-pressure substances inside the battery monomer 20 when the battery monomer 20 is in thermal runaway, which can reduce the risk of the electrode terminal of the battery monomer 20 being separated from the shell 21 and the shell 21 being broken, and is conducive to improving the reliability of the battery monomer 20; in the case of D≤8 mm, the waste of the space inside the battery monomer 20 can be reduced, which is conducive to improving the volumetric energy density of the battery monomer. Therefore, in the case of 6 mm≤D≤8 mm, the volumetric energy density and the reliability of the battery monomer can be considered.

[0110] In some embodiments, the mass content A of dimethyl carbonate satisfies: 20wt%≤A≤60wt%, based on the total mass of the electrolyte; and / or, the mass content B of lithium bisfluorosulfonylimide salt satisfies: 2wt%≤B≤16wt%, based on the total mass of the electrolyte.

[0111] The mass content A of dimethyl carbonate can be 20wt%, 30wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, or any value within the above range, and the mass content B of lithium bisfluorosulfonylimide salt can be 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 16wt%, or any value within the above range.

[0112] The higher the mass content of dimethyl carbonate and the mass content of lithium bisfluorosulfonylimide are, the better the fast-charging performance of the battery cell is, but in the case of thermal runaway, the battery cell generates more gas and the thermal runaway of the battery cell is more severe, and the reliability of the battery cell is lower. By setting the mass content of dimethyl carbonate and the mass content of lithium bisfluorosulfonylimide to satisfy the above range, the fast-charging performance and the reliability of the battery cell can be considered.

[0113] In some embodiments, 20wt%≤A≤45wt%;and / or, 2.5wt%≤B≤11wt%.

[0114] In the case of 20wt%≤A≤45wt%, the battery cell generates less gas and has better fast-charging performance, and the risk of dimethyl carbonate precipitation at low temperature is lower; in the case of 2.5wt%≤B≤11wt%, the battery cell has a certain mass content of lithium bisfluorosulfonylimide, and has good fast-charging performance, and the mass content of lithium bisfluorosulfonylimide is not too large, so that the battery cell generates less gas when thermal runaway, and the severity of thermal runaway is smaller, and the battery cell has higher reliability.

[0115] In some embodiments, within 1000 cycles of the battery cell, the mass content of dimethyl carbonate is 10.0g-18.0g, and the mass content of lithium bisfluorosulfonylimide is 2.0g-4.0g.

[0116] In the process of cycling of the battery cell, both dimethyl carbonate and lithium bisfluorosulfonylimide are consumed. Within 1000 cycles of the battery cell, the mass content of dimethyl carbonate is 10.0g-18.0g, and the mass content of lithium bisfluorosulfonylimide is 2.0g-4.0g.

[0117] In the related art, in order to improve the fast-charging performance of the battery cell, more lithium bisfluorosulfonylimide is usually added. However, when lithium bisfluorosulfonylimide has a high mass content in the electrolyte, the battery cell generates more gas and the thermal runaway is more severe when thermal runaway occurs; in addition, lithium bisfluorosulfonylimide also reacts with aluminum in the positive electrode sheet, causing corrosion of the current collector and cracking of the positive electrode sheet, which is not conducive to improving the reliability of the battery cell.

[0118] In some embodiments, the mass content ratio of dimethyl carbonate and lithium bisfluorosulfonylimide A:B satisfies: 3≤A:B≤16.

[0119] In the case of A:B≥3, the severity of thermal runaway of the battery cell is smaller, and the risk of positive electrode sheet cracking is lower, and the battery cell has higher reliability; in the case of A:B≤16, it is beneficial to the transmission of lithium ions, and the battery cell has better fast charging performance. By setting 3≤A:B≤16, the battery cell has good fast charging performance and high reliability.

[0120] In some embodiments, 3≤A:B≤10. In this way, the fast charging performance and reliability of the battery cell are further considered.

[0121] In some embodiments, in the battery cell, the ratio C of the mass of the electrolyte to the capacity of the battery cell satisfies: C≤1.6 g / Ah.

[0122] C can be the ratio of the mass of the electrolyte to the capacity of the battery cell in a battery cell that has not been used (for example, a battery cell in a factory state).

[0123] C can be 1.6 g / Ah, 1.5 g / Ah, 1.4 g / Ah, 1.3 g / Ah, 1.2 g / Ah, or any value within the above range.

[0124] The value of C in the factory state is small, so that the mass of the electrolyte in the battery cell is small, the mass of DMC and LiFSI in the electrolyte is small, in the case of thermal runaway of the battery cell, the battery cell generates less gas, the severity of the battery cell when it is in thermal runaway is low, which is beneficial to improve the reliability of the battery cell.

[0125] In some embodiments, 1.2 g / Ah≤C≤1.4 g / Ah. In the case of C≤1.4 g / Ah, the mass of the electrolyte in the battery cell is small, which is beneficial to further improve the reliability of the battery cell; in the case of C≥1.2 g / Ah, the mass of the electrolyte can meet the normal work of the battery cell, which can reduce the influence on the cycle performance and other electrical properties of the battery cell. Therefore, the above technical solution is beneficial to consider the reliability and electrical performance of the battery cell.

[0126] In some embodiments, within 1000 cycles of the battery cell, the ratio E of the mass of the remaining electrolyte in the battery cell to the capacity of the battery cell satisfies: 0.7 g / Ah≤E≤1.1 g / Ah.

[0127] Within 1000 cycles, E can be 0.7 g / Ah, 0.8 g / Ah, 0.9 g / Ah, 1.0 g / Ah, 1.1 g / Ah, or any value within the above range.

[0128] During the cycle of the battery cell, the electrolyte will be consumed. As the number of charge and discharge cycles increases, the mass of the electrolyte remaining in the battery cell gradually decreases, and the ratio of the mass of the electrolyte to the capacity of the battery cell also changes. After the battery cell is cycled for a period of time, for example, within 1000 cycles, the ratio E of the mass of the electrolyte remaining in the battery cell to the capacity of the battery cell is approximately in the range of 0.7 g / Ah to 1.1 g / Ah.

[0129] In some embodiments, the size H of the battery cell 20 along the thickness direction of the end cover 23 satisfies: 90 mm≤H≤120 mm. In this way, the battery cell 20 has a suitable capacity and height, and thus the battery cell 20 has a relatively suitable energy density.

[0130] The size H of the battery cell 20 can be the distance between the electrode terminal 25 and the end cover 23 along the thickness direction (for example, the z direction in FIG. 2) of the end cover 23. H can be 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 120 mm, or any value in the above range.

[0131] In some embodiments, the mass K of the electrolyte in the battery cell satisfies: 30 g≤K≤60 g.

[0132] K can be the mass of the electrolyte in a battery cell that has not been used (for example, a battery cell in a factory state).

[0133] K can be 30 g, 35 g, 38 g, 40 g, 42 g, 50 g, 55 g, 59 g, 60 g, or any value in the above range.

[0134] When 30 g≤K≤60 g, the battery cell has good fast-charging performance.

[0135] In some embodiments, 35 g≤K≤50 g. When 35 g≤K≤50 g, the battery cell has a lower degree of severity when thermal runaway occurs, and the risk of the shell being broken and the electrode terminal flying out of the shell is lower, and the battery cell has higher reliability.

[0136] In some embodiments, within 1000 cycles of the battery cell, the mass P of the electrolyte remaining in the battery cell satisfies: 22 g≤P≤36 g.

[0137] Within 1000 cycles, the mass P of the electrolyte remaining can be 22 g, 25 g, 28 g, 30 g, 32 g, 34 g, 36 g, or any value in the above range.

[0138] During the charging and discharging cycle of the battery cell, the mass of the electrolyte in the battery cell gradually decreases with the increase of the number of charging and discharging cycles. After the battery cell is cycled for a period of time, for example, within 1000 cycles, the mass of the remaining electrolyte is approximately in the range of 22g-36g.

[0139] In some embodiments, the mass K of the electrolyte and the size of the gap D satisfy: 4g / mm≤K / D≤11g / mm.

[0140] K / D can be 4g / mm, 5g / mm, 6g / mm, 6.5g / mm, 7g / mm, 7.5g / mm, 8g / mm, 8.5g / mm, 9g / mm, or any value within the above range.

[0141] The mass K of the electrolyte can refer to the mass of the electrolyte in the battery cell 20.

[0142] The mass of the electrolyte in the battery cell is different, and the amount of gas generated inside the battery cell and the severity when thermal runaway occurs are also different. Therefore, setting the relationship between the mass of the electrolyte and the gap facilitates obtaining a battery cell with appropriate electrolyte mass and high reliability.

[0143] The larger K / D is, the larger the volumetric energy density of the battery cell is, but when the battery cell experiences thermal runaway, the space provided for the rupture of the pressure relief mechanism 26 is smaller, and the risk of normal valve opening and timely valve failure (for example, the shell 21 is ruptured, and the electrode terminal is separated from the shell 21) of the battery cell is higher; the smaller K / D is, the smaller the volumetric energy density of the battery cell is, but the risk of normal valve opening and timely valve failure of the battery cell is lower.

[0144] When K / D≥4g / mm, the battery cell has a higher volumetric energy density; when K / D≤11g / mm, the risk of shell rupture and electrode terminal separation from the shell when the battery cell experiences thermal runaway can be reduced, and the battery cell has higher reliability. Therefore, by setting 4g / mm≤K / D≤11g / mm, the volumetric energy density and reliability of the battery cell can be considered.

[0145] In some embodiments, 6g / mm≤K / D≤8.5g / mm. In this way, the volumetric energy density and reliability of the battery cell can be further considered, and the battery cell has better comprehensive performance.

[0146] The energy density of the battery cell is related to the compaction density of the positive electrode tab and the negative electrode tab. The greater the compaction density of the positive electrode tab and the negative electrode tab, the more conducive to improving the energy density of the battery cell. In the related art, in order to improve the fast charging performance of the battery cell, a positive electrode tab and / or a negative electrode tab with a smaller compaction density is usually selected. The reason is that, in the case of a larger compaction density of the positive electrode tab and the negative electrode tab, the transmission path of lithium ions is more tortuous, and under a large current, the capacity that the battery cell can develop is reduced, and the fast charging performance of the battery cell is reduced. In addition, in the related art, in order to improve the reliability of the battery cell, the compaction density of the positive electrode tab and the negative electrode tab is appropriately reduced to reduce the energy density of the battery cell. This is because the higher the energy density of the battery cell, the more severe the thermal runaway of the battery cell, which is also not conducive to improving the reliability of the battery cell. In some embodiments of the present application, since the mass content of DMC and LiFSI in the electrolyte and the space size of the gap D are reasonably regulated, the compaction density of the positive electrode tab and the negative electrode tab is set to a larger value, which has less effect on the fast charging performance of the battery cell, and there is sufficient space for the actuation of the pressure relief mechanism in the battery cell, which can reduce the risk that the pressure relief mechanism cannot be opened in time in the event of thermal runaway.

[0147] In some embodiments, the electrode assembly 22 includes a positive electrode tab and a negative electrode tab, the compaction density of the positive electrode tab is greater than or equal to 3.55 g / cm 3 , and / or the compaction density of the negative electrode tab is greater than or equal to 1.5 g / cm 3 .

[0148] The compaction density of the positive electrode tab can be 3.55 g / cm 3 , 3.6 g / cm 3 , 3.65 g / cm 3 , 3.7 g / cm 3 , or any value within the above range.

[0149] The compaction density of the negative electrode tab can be 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , 1.65 g / cm 3 , or any value within the above range.

[0150] The compaction density of the positive electrode tab and the negative electrode tab can be the compaction density after cold pressing. After the positive electrode tab and the negative electrode tab are prepared into a battery cell, the compaction density of the fresh battery cell in the full discharge state decreases by about 0.1 g / cm 3 after 1000 times or less of charge and discharge cycles, the compaction density decreases by about 0.05 g / cm 3 ~0.1 g / cm.3 .

[0151] As an example, the compacted density of the positive electrode sheet is greater than or equal to 3.55 g / cm 3 after cold pressing, and the compacted density of the negative electrode sheet is less than 1.5 g / cm 3 .

[0152] As an example, the compacted density of the positive electrode sheet is less than 3.55 g / cm 3 after cold pressing, and the compacted density of the negative electrode sheet is greater than or equal to 1.5 g / cm 3 .

[0153] As an example, the compacted density of the positive electrode sheet is greater than or equal to 3.55 g / cm 3 after cold pressing, and / or the compacted density of the negative electrode sheet is greater than or equal to 1.5 g / cm 3 .

[0154] In the case where the compacted density of the positive electrode sheet is greater than or equal to 3.55 g / cm 3 , and / or in the case where the compacted density of the negative electrode sheet is greater than or equal to 3.55 g / cm 3 , the battery cell has a higher energy density, while the battery cell also has better fast charging performance and higher reliability.

[0155] In some embodiments, the compacted density of the positive electrode sheet is 3.55 g / cm 3 ~ 3.7 g / cm 3 , and / or the compacted density of the negative electrode sheet is 1.5 g / cm 3 ~ 1.7 g / cm 3 .

[0156] In the above embodiments, the positive electrode sheet and / or the negative electrode sheet have a higher compacted density, and the battery cell can have a higher energy density with higher reliability and better fast charging performance.

[0157] In some embodiments, the compacted density of the positive electrode sheet is 3.35 g / cm 3 ~ 3.69 g / cm 3 , and / or the compacted density of the negative electrode sheet is 1.3 g / cm 3 ~ 1.65 g / cm 3 .

[0158] During the charge-discharge cycle of the battery cell, the positive electrode sheet and the negative electrode sheet expand, the thickness of the positive electrode sheet and the negative electrode sheet can change, and the compaction density of the positive electrode sheet and the negative electrode sheet also changes. Within 1000 cycles of the battery cell, the compaction density of the positive electrode sheet is about 3.35 g / cm 3 ~ 3.69 g / cm 3 , and the compaction density of the negative electrode sheet is about 1.3 g / cm 3 ~ 1.65 g / cm 3 .

[0159] The porosity of the electrode sheet is related to the compaction density of the electrode sheet. The greater the compaction density of the electrode sheet, the smaller the porosity of the electrode sheet. In some embodiments, the porosity of the positive electrode sheet is 22%~26%, and / or the porosity of the negative electrode sheet is 23%~27%. In this way, it is beneficial to improve the energy density of the battery cell while the battery cell has good reliability and fast charging performance.

[0160] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the mass G0 and the gap D of the positive electrode film layer satisfy: 15 g / mm≤G0 / D≤42 g / mm.

[0161] G0 / D can be 15 g / mm, 19 g / mm, 20 g / mm, 21 g / mm, 23 g / mm, 25 g / mm, 26 g / mm, 28 g / mm, 35 g / mm, 40 g / mm, 42 g / mm, or any value within the above range.

[0162] The mass of the positive electrode film layer and the positive electrode active material included in the positive electrode film layer satisfy a certain proportional relationship. For example, the positive electrode active material accounts for 97%~98% of the total mass of the positive electrode film layer.

[0163] The greater the mass of the positive electrode film layer and the mass of the positive electrode active material, the more severe the degree of thermal runaway of the battery cell, and the greater the capacity and volume energy density of the battery cell. By setting the relationship between the mass G of the positive electrode active material and the gap D, it is beneficial to balance the reliability and energy density of the battery cell.

[0164] In the case of G0 / D≥15 g / mm, the battery cell has a high energy density; in the case of G0 / D≤40 g / mm, the battery cell has high reliability. By setting 15 g / mm≤G0 / D≤40 g / mm, the battery cell can balance the energy density and reliability.

[0165] In some embodiments, 18 g / mm≤G0 / D≤28 g / mm. In this way, the energy density and reliability of the battery cell are more balanced, and the battery cell has a more optimal comprehensive performance.

[0166] In some embodiments, the cathode film layer includes a cathode active material, and the cathode active material includes lithium nickel oxide or metal phosphate.

[0167] The metal phosphate can include lithium iron phosphate, lithium manganese iron phosphate, etc.

[0168] Different cathode active materials included in the battery cell can have different performances. For example, the battery cell includes lithium nickel oxide, and the lithium nickel oxide has a high gravimetric capacity, which is beneficial to obtain a battery cell with high energy density; for another example, the battery cell includes metal phosphate, and the metal phosphate has high stability, which is beneficial to obtain a battery cell with high reliability.

[0169] In some embodiments, the chemical formula of the lithium nickel oxide satisfies: Li 1+a [Ni x Co y Mn z M b ]O 2-c , M includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta, or Sr, 0.2≥a≥-0.2, 1>x≥0.7, 0.3>y>0, 0.3>z>0, 0.3>b≥0, 0.5≥c≥0. As an example, x+y+z+b=1, the content of Ni in the above cathode active material is high, which is beneficial to improve the energy density of the battery cell.

[0170] a can be -0.2, -0.1, -0.04, 0, 0.04, 0.1, 0.2, or any value within the above range, x can be 0.7, 0.75, 0.8, 0.9, 0.95, 0.96, or any value within the above range, y can be 0.1, 0.2, or any value within the above range, z can be 0.1, 0.2, or any value within the above range, b can be 0, 0.1, 0.2, or any value within the above range, and c can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, or any value within the above range. As an example, b is 0, and the cathode active material includes LiNi 0.8 Co 0.1 Mn 0.1 O2. As another example, b>0, and the cathode active material includes LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2.

[0171] The positive electrode active material satisfying the above formula can be referred to as a high-nickel ternary material. Compared with a ternary material with a low nickel content or a material such as lithium iron phosphate, the high-nickel ternary material has a higher gram capacity, and thus, in the same mass, the use of the high-nickel ternary material is beneficial to improve the capacity and energy density of the battery monomer.

[0172] It should be noted that the battery monomer will be accompanied by Li deintercalation and consumption during the charging and discharging process, and the molar content of Li is different when the battery monomer is discharged to different states. In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of Li is the initial state of the material, and the positive electrode active material is applied to the battery system. After charging and discharging cycles, the molar content of Li will change. In the enumeration of the positive electrode active material in the embodiments of the present application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will appear to be floating.

[0173] In some embodiments, the positive electrode active material includes at least one of LiNi 0.90 Co 0.06 Mn 0.04 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2 or LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0174] In some embodiments, in the battery monomer, the gram weight per unit area of the positive electrode active material is 15 mg / cm 2 ~ 23 mg / cm 2 . For example, the gram weight per unit area of the positive electrode active material is 15 mg / cm 2 , 16 mg / cm 2 , 17 mg / cm 2 , 18 mg / cm 2 , 20 mg / cm 2 , 23 mg / cm 2 or any value within the above range. In the case where the gram weight per unit area of the positive electrode active material is 15 mg / cm 2 ~ 23 mg / cm 2 , the battery monomer has a high energy density.

[0175] In some embodiments, the negative electrode tab includes a negative electrode active material, the negative electrode active material includes graphite and a silicon-containing material, the silicon-containing material includes at least one of elemental silicon, a silicon-oxygen composite, a silicon-carbon composite, a silicon-nitrogen composite, a silicon-containing alloy, or a silicon-oxygen-carbon composite material, and the graphite includes at least one of natural graphite or artificial graphite. The negative electrode active material described above is beneficial to improve the energy density of the battery cell.

[0176] In some embodiments, the silicon-containing material includes a silicon-carbon composite, and a mass fraction of silicon in the silicon-carbon composite is 40wt% to 60wt% based on a total mass of the silicon-containing material. When the mass content of silicon in the silicon-carbon composite is within the range described above, the electrode assembly has a relatively appropriate expansion rate, which is beneficial to the normal use of the battery cell.

[0177] In some embodiments, a mass content B of the silicon-containing material satisfies: 1wt%≤B≤20wt% based on a total mass of the negative electrode active material.

[0178] B can be 1wt%, 5wt%, 8wt%, 15wt%, 20wt%, or any value within the range described above.

[0179] By setting the mass content of the silicon-containing material to satisfy the range described above, it is not only beneficial to obtain a negative electrode tab with a relatively high compaction density, but also beneficial to reduce the risk of excessive expansion of the battery cell due to the excessive mass content of the silicon-containing material. Therefore, the energy density of the battery cell can be improved while facilitating the normal use of the battery cell.

[0180] As an example, the negative electrode active material includes artificial graphite and a silicon-carbon composite, the mass content of the silicon-carbon composite is 6wt% based on a total mass of the negative electrode active material, and the mass content of silicon in the silicon-carbon composite is 50wt%.

[0181] In some embodiments, in the negative electrode tab, the negative electrode active material has a gram weight per unit area of 8mg / cm 2 to 13mg / cm 2 . The mass of the negative electrode active material can be 8mg / cm 2 , 10mg / cm 2 , 12mg / cm 2 , 13mg / cm 2 , or any value within the range described above. The negative electrode active material has a relatively high gram weight per unit area, and the battery cell has a relatively high energy density.

[0182] In the related art, the surface of the isolation film is coated with a polyvinylidene fluoride (PVDF) coating to better bond the isolation film to the positive electrode tab and the negative electrode tab. In some embodiments of the present application, the electrode assembly 22 further includes an isolation film disposed between the positive electrode tab and the negative electrode tab, and the isolation film includes a base film and a ceramic coating disposed on a side of the base film facing the positive electrode tab.

[0183] Along the thickness direction of the base film, a ceramic coating is disposed on the side of the base film facing the positive electrode tab. Compared to the related art in which a ceramic coating and a PVDF coating are sequentially disposed on both sides of the base film, disposing only a ceramic coating on the side of the base film facing the positive electrode tab can reduce the absorption of electrolyte by the isolation film, and the amount of electrolyte absorbed by the isolation film is less, which can reduce the amount of electrolyte injected into the battery cell, thereby reducing the amount of gas generated and the severity of thermal runaway of the battery cell, and improving the reliability of the battery cell.

[0184] In the related art, in order to improve the fast charging performance of the battery cell, an isolation film with a large porosity is usually selected. However, an isolation film with a large porosity is easily pierced by burrs (such as burrs of the positive electrode tab or burrs of the negative electrode tab), which is not conducive to improving the reliability of the battery cell. In some embodiments of the present application, an isolation film with a small porosity is selected to improve the reliability of the battery cell; and the mass content of DMC and LiFSI in the electrolyte is reasonably controlled, the ion transmission rate is fast, and the battery cell still has good fast charging performance under the condition that the porosity of the isolation film is small.

[0185] In some embodiments, the porosity of the isolation film is 30% to 45%. In this way, the isolation film has a low porosity, which is conducive to reducing the amount of electrolyte required in the battery cell, thereby reducing the amount of gas generated and the severity of thermal runaway of the battery cell, and improving the reliability of the battery cell.

[0186] In some embodiments, the end cover 23 includes an end cover body 231, and the pressure relief mechanism 26 is disposed on the inner side or the outer side of the end cover body 231.

[0187] As an example, the pressure relief mechanism 26 is disposed on the inner side of the end cover body 231, which means that, along the thickness direction of the end cover 23, the pressure relief mechanism 26 is disposed on the side of the end cover body 231 facing the electrode assembly.

[0188] As another example, the pressure relief mechanism 26 is disposed on the outer side of the end cover body 231, which means that, along the thickness direction of the end cover 23, the pressure relief mechanism 26 is disposed on the side of the end cover body 231 away from the electrode assembly.

[0189] FIG. 5 is a schematic diagram of the force on the pressure relief mechanism arranged on the inner side of the end cover body according to an embodiment of the present application, and FIG. 6 is a schematic diagram of the force on the pressure relief mechanism arranged on the outer side of the end cover body according to an embodiment of the present application. As shown in FIGS. 5 and 6, the pressure relief mechanism 26 is arranged on the side of the end cover body 231 away from the electrode assembly (the outer side of the end cover body 231). In the case of swelling of the battery cell, the end cover 23 protrudes away from the electrode assembly 22, and the pressure relief mechanism 26 is subjected to a force that pulls the pressure relief mechanism 26 outward, so the pressure relief mechanism 26 is more likely to tear.

[0190] By arranging the pressure relief mechanism 26 on the inner side of the end cover body 231, in the case of swelling of the battery cell and protrusion of the end cover 23 away from the electrode assembly 22, the pressure relief mechanism 26 is subjected to a force that pulls the pressure relief mechanism 26 inward, so the pressure relief mechanism 26 is less likely to tear, thereby facilitating improvement of the reliability of the pressure relief mechanism.

[0191] By arranging the pressure relief mechanism 26 on the outer side of the end cover body 231, it is convenient to reduce the complexity of preparation of the pressure relief mechanism 26.

[0192] FIG. 7 is a schematic diagram of the structure of the end cover according to an embodiment of the present application. In some embodiments, as shown in FIG. 7, the end cover body 231 is provided with a score groove 261, and the area defined by the score groove 261 forms the pressure relief mechanism 26.

[0193] As an example, the end cover 23 is a circular end cover, the shape of the end cover body 231 is circular, and the shape of the score groove 261 is circular or arc-shaped with a notch 262. The area of the pressure relief mechanism 26 is the area of the region defined by the score groove 261. For example, the score groove 261 is circular, so the area of the region defined by the score groove 261 can be obtained according to the diameter R of the circle.

[0194] By arranging the score groove 261 on the end cover body 231, it is convenient to prepare the pressure relief mechanism 26, and it is also convenient to reduce the risk of interference between the pressure relief mechanism 26 and the components in the battery cell.

[0195] In some embodiments, the area S of the region defined by the pressure relief mechanism 26 and the area S0 of the end cover satisfy: 25%≤S / S0≤50%.

[0196] S / S0 can be 25%, 30%, 35%, 40%, 50%, or any value in the above range.

[0197] In the case of S / S0≥25%, in the case of thermal runaway of the battery cell, the pressure relief mechanism 26 is more likely to break, thereby facilitating the end cover to have a larger tearing opening and facilitating the discharge of high-temperature and high-pressure substances inside the battery cell; in the case of S / S0≤50%, it is convenient to reduce the interference of the pressure relief mechanism 26 on the connection between the end cover and the shell and facilitate the connection between the end cover and the shell.

[0198] In some embodiments, the area S of the pressure relief mechanism 26 and the capacity Q of the battery cell satisfy: 12mm 2 / Ah≤S / Q≤20mm 2 / Ah.

[0199] S / Q can be 12mm 2 / Ah, 14mm 2 / Ah, 16mm 2 / Ah, 18mm 2 / Ah, 20mm 2 / Ah or any value within the above range.

[0200] The greater the capacity of the battery cell, the more violent the thermal runaway of the battery cell, and the larger the area of the pressure relief mechanism 26 facilitates actuation and rupture during thermal runaway to smoothly discharge the discharge material inside the battery cell.

[0201] In the case of S / Q≥12mm 2 / Ah, it is beneficial to make the end cover 23 have a larger tearing opening and tearing degree in the case of thermal runaway of the battery cell 20, and it is beneficial to the discharge of high-temperature and high-pressure materials inside the battery cell 20; in the case of S / Q≤20mm 2 / Ah, it can reduce the interference of the pressure relief mechanism 26 on the connection (such as welding) between the end cover 23 and the shell 21, and facilitate the connection (such as welding) between the end cover 23 and the shell 21.

[0202] In the above embodiments, battery cells of different capacities can be provided with pressure relief mechanisms 26 of different area sizes, which are beneficial to both the discharge of high-temperature and high-pressure materials during thermal runaway of the battery cell and the connection between the shell and the end cover.

[0203] In some embodiments, the area S of the pressure relief mechanism 26 is greater than or equal to 500mm 2 .

[0204] S can be 500mm 2 , 550mm 2 , 600mm 2 , 700mm 2 , 800mm 2 , 900mm 2 , 1000mm 2 or any value within the above range.

[0205] The greater the area S of the pressure relief mechanism 26, the easier it is to tear the pressure relief mechanism 26 when the battery cell undergoes thermal runaway, the greater the opening and degree of tearing of the end cover 23, and the more beneficial it is to the discharge of high-temperature and high-pressure materials inside the battery cell 20.

[0206] By setting S greater than or equal to 500mm 2 , it is beneficial to make the end cover 23 have a larger tearing opening and tearing degree in the case of thermal runaway of the battery monomer 20, and beneficial to the discharge of high-temperature and high-pressure substances inside the battery monomer 20.

[0207] In some embodiments, the area S of the pressure relief mechanism 26 satisfies: 600mm 2 ≤S≤800mm 2 .

[0208] The area S of the pressure relief mechanism 26 can be 500mm 2 , 550mm 2 , 600mm 2 , 700mm 2 , 800mm 2 or any value within the above range.

[0209] In the case of S greater than or equal to 600mm 2 , it is beneficial to make the end cover 23 have a larger tearing opening and tearing degree in the case of thermal runaway of the battery monomer 20, and beneficial to the discharge of high-temperature and high-pressure substances inside the battery monomer 20; in the case of S less than or equal to 800mm 2 , the interference of the pressure relief mechanism 26 on the connection (such as welding) between the end cover 23 and the shell 21 can be reduced, and the connection (such as welding) between the end cover 23 and the shell 21 is facilitated.

[0210] In the above technical solution, by setting the area of the pressure relief mechanism 26 to satisfy the above range, both the risk of cracking of the pressure relief mechanism 26 during normal use of the battery monomer can be reduced, and the pressure relief mechanism 26 can be broken in time when the battery monomer is in thermal runaway, so as to balance the long-term use reliability of the battery monomer and the reliability in thermal runaway.

[0211] In some embodiments, the voltage platform of the battery monomer is 3.5V-3.7V. In the case of the above range of the voltage window of the battery monomer, the battery monomer has a higher energy density.

[0212] In some embodiments, the solvent further includes methyl ethyl carbonate and ethylene carbonate, and the electrolyte salt further includes lithium hexafluorophosphate.

[0213] In the above embodiments, the solvent of the electrolyte includes dimethyl carbonate, methyl ethyl carbonate and ethylene carbonate, and the electrolyte salt of the electrolyte includes lithium hexafluorophosphate and lithium bisfluorosulfonylimide salt. The electrolyte has a lower viscosity and a higher ionic conductivity, which is beneficial to the improvement of the fast charging performance of the battery monomer.

[0214] In some embodiments, the electrolyte further comprises an additive, and the additive comprises at least one of fluoroethylene carbonate or vinylene carbonate. The addition of the additive can reduce decomposition of the electrolyte and facilitate improvement of fast-charging performance of the battery cell.

[0215] In some embodiments, the battery cell 20 further comprises a current collecting member 24 accommodated in the housing 21, disposed between the electrode assembly 22 and the end cover 23 along the thickness direction of the end cover 23 (for example, the z direction in FIG. 3), and electrically connected to the tab of the electrode assembly 22 and the housing 21. By the provision of the current collecting member 24, electrical connection between the electrode assembly 22 and the housing 21 is facilitated.

[0216] The current collecting member 24 is disposed between the electrode assembly 22 and the end cover 23, which can mean that the current collecting member 24 is disposed on the side of the electrode assembly 22 facing the end cover 23. As an example, part of the current collecting member 24 is welded to the tab of the electrode assembly 22, and the other part is in abutment or welded to the end cover 23.

[0217] In some embodiments, the inner side surface of the housing 21 is provided with a limiting portion 211, and the limiting portion 211 is located between the electrode assembly 22 and the end cover 23 along the thickness direction of the end cover 23, and the current collecting member 24 is in abutment with the side of the limiting portion 211 facing the electrode assembly 22.

[0218] The inner side surface of the housing 21 refers to the inner side surface of the side wall of the housing 21 extending along the thickness direction of the end cover 23. Understandably, the inner side surface extends substantially along the thickness direction of the end cover 23. In the embodiment in which the housing 21 is a cylinder, the inner side surface of the housing 21 is a cylindrical surface. In the embodiment in which the housing 21 is a cuboid, the inner side surface of the housing 21 comprises four side surfaces located at different orientations and connected in sequence.

[0219] The inner side surface of the housing 21 is provided with the limiting portion 211. Understandably, the limiting portion 211 protrudes from the inner side surface. The limiting portion 211 is a structure of the housing 21 limiting movement of the end cover 23 towards the electrode assembly 22.

[0220] The limiting portion 211 and the housing 21 can be an integrally formed structure, or can be a structure connected together after being formed separately, for example, the limiting portion 211 and the housing 21 are welded. The limiting portion 211 can be various structures, for example, the limiting portion 211 is a boss protruding from the inner side surface of the housing 21, or for example, the limiting portion 211 is an annular structure extending along the circumference of the housing 21.

[0221] In the above embodiment, the inner side of the shell 21 is provided with a limiting portion 211, which not only limits the movement of the end cover 23 in the direction facing the electrode assembly 22, but also facilitates the realization of the gap between the electrode assembly 22 and the end cover 23, thereby providing space for the expansion of the electrode assembly 22 and the rupture of the end cover.

[0222] In some embodiments, the battery monomer further comprises a sealing member 212 arranged between the end cover 23 and the shell 21. The arrangement of the sealing member 212 is conducive to improving the sealing performance of the battery monomer, thereby improving the reliability of the battery monomer.

[0223] As an example, the sealing member 212 is an insulating member that can electrically isolate the end cover 23 and the shell 21. The shape of the sealing member 212 can be adapted to the shape of the limiting portion 211, for example, S-shaped, and the embodiments of the present application include but are not limited to this.

[0224] Figure 8 is a structural schematic diagram of the current collecting member according to an embodiment of the present application. In some embodiments, as shown in Figures 3-4 and 8, the current collecting member 24 comprises a current collecting body 240, an elastic portion 241, a current collecting sheet 242 and a center portion 243. The current collecting sheet 242 and the elastic portion 241 are both connected to the circular ring-shaped current collecting body 240, the elastic portion 241 is located between the current collecting body 240 and the center portion 243, and the elastic portion 241 and the current collecting sheet 242 are arranged separately.

[0225] In the thickness direction of the end cover 23, the elastic portion 241 protrudes relative to the current collecting body 240 in the direction away from the electrode assembly 22 and abuts against the end cover 23, thereby realizing the connection between the current collecting member 24 and the end cover 23 through the elastic portion 241. As an example, the end cover body 231 is provided with a protrusion 232, and the elastic portion 241 abuts against the protrusion 232.

[0226] As an example, the elastic portion 241 comprises a first sheet 2411 and a second sheet 2412, the first sheet 2411 is connected to the inner side of the current collecting body 240 and extends obliquely towards the end cover 23, the second sheet 2412 is connected to the outer side of the center portion 243 and extends obliquely towards the end cover 23, the first sheet 2411 and the second sheet 2412 are connected at an included angle greater than 0° and less than 180° and form an abutment area 2414, and the abutment area 2414 abuts against the end cover 23.

[0227] As an example, the current collecting member 24 comprises three current collecting sheets 242, which are arranged separately along the circumference of the current collecting body 240, and the current collecting sheets 242 are welded with the tabs of the electrode assembly 22 to realize the electrical connection between the current collecting member 24 and the electrode assembly 22.

[0228] In some embodiments, the material of the shell 21 comprises carbon steel or stainless steel.

[0229] In some embodiments, the battery cell 20 is a cylindrical battery cell 20.

[0230] In some embodiments, the shell 21 comprises a barrel and a cover connected to the barrel, the cover and the barrel are integrally formed or separately formed, the barrel is arranged around the outer periphery of the electrode assembly 22, and the cover is provided with an electrode lead-out hole; the battery cell 20 further comprises an electrode terminal 25, and the electrode terminal 25 is arranged in the electrode lead-out hole in an insulated manner.

[0231] As an example, the cover and the barrel are integrally formed.

[0232] As another example, the cover and the barrel are separately formed. The cover can be disc-shaped, and the barrel can be cylindrical.

[0233] In this embodiment, one of the shell 21 and the electrode terminal 25 is a positive output pole of the battery cell 20, and the other is a negative output pole of the battery cell 20. At least part of the shell 21 itself can serve as one output pole of the battery cell 20, so that one electrode terminal can be omitted, which is conducive to simplifying the structure of the battery cell 20.

[0234] In some embodiments, the battery cell 20 further comprises a current collecting disc 27. The current collecting disc 27 can have a different structure from the current collecting member 24, and the current collecting disc 27 can be disc-shaped. The current collecting disc 27 and the current collecting member 24 are respectively located at two ends of the shell 21 and connected to electrodes with opposite polarities. As an example, the current collecting disc 27 is connected to a positive tab, and the current collecting member 24 is connected to a negative tab.

[0235] In some embodiments, the battery cell 20 further comprises an insulating piece 28 for isolating the electrode terminal 25 and the shell 21.

[0236] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0237] [Battery]

[0238] The embodiments of the present application provide a battery comprising the battery cell in the above embodiments. The battery can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in a mixed manner through a current collecting component.

[0239] In some embodiments, the battery can be a battery pack, and the battery comprises a box body and a battery cell, and the battery cell or the battery module is contained in the box body.

[0240] In some embodiments, the box can be part of a chassis structure of a vehicle. For example, the box can be at least part of a floor of the vehicle, or the box can be at least part of a cross beam and a longitudinal beam of the vehicle.

[0241] In some embodiments, the battery can be located in an energy storage device. The energy storage device can include an energy storage container, an energy storage cabinet, etc.

[0242] FIG. 9 is a schematic view of a battery according to an embodiment of the present application. As shown in FIG. 9, the battery 10 can include a plurality of battery cells 20 to meet different power requirements.

[0243] The battery 10 can further include a box 3, which is hollow inside and in which the plurality of battery cells 20 are accommodated. For example, the plurality of battery cells 20 are arranged in parallel or in series or in a hybrid combination in the box 3. The box 3 can include a first box part 31 and a second box part 32, which are coupled to each other to form the box 3. The shapes of the first box part 31 and the second box part 32 can be determined according to the shapes of the components accommodated therein, for example, according to the shape of the combination of the plurality of battery cells 20, and at least one of the first box part 31 and the second box part 32 has an opening. For example, as shown in FIG. 9, the first box part 31 and the second box part 32 can each be a hollow cuboid with one face as an opening face. The opening of the first box part 31 and the opening of the second box part 32 are arranged opposite to each other, and the first box part 31 and the second box part 32 are coupled to each other to form the box 3 having a closed cavity, which can be used to accommodate the plurality of battery cells 20. The plurality of battery cells 20 are arranged in parallel or in series or in a hybrid combination in the box 3 formed by the coupling of the first box part 31 and the second box part 32.

[0244] For another example, unlike that shown in FIG. 9, only one of the first box part 31 and the second box part 32 can be a hollow cuboid with an opening, and the other can be a plate to cover the opening. For example, the second box part 32 is a hollow cuboid with an opening, and the first box part 31 is a plate. In this case, the first box part 31 is coupled to the opening of the second box part 32 to form the box 3 having a closed cavity, which can be used to accommodate the plurality of battery cells 20.

[0245] In some embodiments, the battery 10 can further include other components. For example, the battery 10 can further include a busbar component, which can be used to achieve electrical connection between a plurality of battery monomers 20, such as parallel connection or series connection or mixed connection. Specifically, the busbar component can achieve electrical connection between the battery monomers 20 by connecting the electrode terminals of the battery monomers 20; or the busbar component can also achieve electrical connection between the battery monomers 20 by connecting other components of the battery monomers 20. The busbar component can be fixed to the corresponding component of the battery monomer 20 by welding, for example, can be fixed to the electrode terminal, the sealing structure or the shell by welding, and the embodiments of the present application are not limited thereto.

[0246] The battery monomers 20 can directly constitute the battery 10, or can first constitute a battery module, and then constitute the battery 10 by a plurality of battery modules.

[0247] [Electric device]

[0248] The embodiments of the present application provide an electric device, which includes the battery described in the above embodiments.

[0249] The electric device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not specially limit the above electric device.

[0250] FIG. 10 is a schematic diagram of an electric device according to an embodiment of the present application. As shown in FIG. 10, the present application provides an electric device, which is a vehicle.

[0251] The vehicle 1 can be a fuel automobile, a gas automobile, or a new energy automobile. The new energy automobile can be a pure electric automobile, a hybrid automobile, or a range extended automobile, etc. The vehicle 1 can be provided with a motor 40, a controller 30, and a battery 10. The controller 30 is configured to control the battery 10 to supply power to the motor 40. For example, the battery 10 can be arranged at the bottom, the front, or the rear of the vehicle 1. The battery 10 can be configured to supply power to the vehicle 1. For example, the battery 10 can be configured as a power supply for the vehicle 1, and can be configured to supply power to the circuit system of the vehicle 1, such as the power required for starting, navigation, and operation of the vehicle 1. In another embodiment of the present application, the battery 10 can be configured as a power supply for the vehicle 1, and can be configured to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1.

[0252] [Positive electrode sheet]

[0253] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on the positive electrode current collector.

[0254] The positive electrode current collector can be a metal foil or a composite positive electrode current collector. For example, the positive electrode current collector can be an aluminum foil.

[0255] The composite positive electrode current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite positive electrode current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0256] The positive electrode film layer can optionally include a binder. As an example, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0257] The positive electrode film layer can optionally include a conductive agent. The conductive agent can be selected from one or more of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0258] [Negative electrode sheet]

[0259] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector.

[0260] The negative current collector can be a metal foil or a composite negative current collector. The negative current collector can be a copper foil. The composite negative current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, 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.).

[0261] The negative electrode film layer includes a negative active material. The negative active material can be any of the negative active materials known in the art for use in batteries. As an example, the negative active material can include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from one or more of elemental silicon, silicon-oxygen composite, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from one or more of elemental tin, tin-oxygen compound, and tin alloy. However, the application is not limited to these materials, and other conventional materials that can be used as negative active materials for batteries can also be used. The negative active material can be used alone or in combination with two or more.

[0262] The negative electrode film layer can also optionally include a binder. As an example, the binder can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic ester resin.

[0263] The negative electrode film layer can also optionally include a conductive agent. The conductive agent can be selected from one or more of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0264] [Electrolyte]

[0265] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The electrolyte includes an electrolyte salt and a solvent.

[0266] The electrolyte salt can include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bistrifluoromethylsulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoroboric oxalate, lithium bioricoboric oxalate, lithium difluoroboric dioxalate phosphate, and lithium tetrafluoroboric oxalate phosphate.

[0267] The solvent can include one or more of ethylene carbonate, propylene carbonate, methyl ethyl 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, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0268] The electrolyte can also optionally include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include performance additives that can improve certain properties of the battery, such as performance additives that improve overcharge performance of the battery, performance additives that improve high or low temperature performance of the battery, and the like.

[0269] [Separator]

[0270] The separator is used to separate the positive electrode sheet and the negative electrode sheet. The type of the separator is not particularly limited in the embodiments of the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0271] The separator can include a base film. The material of the base film can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film can be a single layer film or a multi-layer composite film, and is not particularly limited. When the base film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0272] The separator can also include a coating layer provided on the surface of the base film. The coating layer can be a ceramic coating layer, and the ceramic coating layer can include materials such as alumina and boehmite.

[0273] The positive electrode sheet, the negative electrode sheet, and the separator can be used to make an electrode assembly by a winding process or a stacking process.

[0274] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are for the purpose of explanation of the present application only, and should not be understood as a limitation of the present application. In the embodiments, the specific techniques or conditions not mentioned are performed according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained commercially.

[0275] [Embodiments]

[0276] Example 1

[0277] In embodiment 1, referring to FIGS. 1-4, the battery cell includes an end cover 23, a current collecting member 24, and a shell 21, an electrode assembly 22 and an electrolyte are accommodated in the shell 21, a limiting portion 211 is protruded on an inner side of the shell 21, the current collecting member 24 is located between the electrode assembly 22 and the end cover 23 and abuts against the limiting portion 211, a tab of the electrode assembly 22 is electrically connected with the shell 21 through the current collecting member 24, the electrode assembly 22 includes a positive electrode sheet, a negative electrode sheet, and a separator film located between the positive electrode sheet and the negative electrode sheet, and the battery cell is a cylindrical battery cell. For specific parameters of the battery cell in embodiment 1 and the serial numbers of the test methods of the parameters, refer to Table 1.

[0278] Embodiment 2-3

[0279] The difference between embodiment 2-3 and embodiment 1 is that the gap D between the electrode assembly and the inner side of the pressure relief mechanism is different.

[0280] Embodiments 4-7

[0281] The difference between embodiments 4-7 and embodiment 1 is that the ratio A:B of the mass content A of dimethyl carbonate DMC to the mass content B of lithium bisfluorosulfonylimide salt LiFSI based on the total mass of the electrolyte is different. Wherein, the value of A:B can be adjusted by adjusting the values of A and / or B.

[0282] Embodiments 8-10

[0283] The difference between embodiments 8-10 and embodiment 1 is that the mass K of the electrolyte is different.

[0284] Embodiment 11

[0285] The difference between embodiment 11 and embodiment 1 is that the capacity of the battery cell is different, wherein the mass of the electrolyte and the mass of the positive active material in the battery cell with different capacity also change; in addition, different gaps D are designed for battery cells with different capacities.

[0286] Embodiments 12-13

[0287] The difference between embodiments 12-13 and embodiment 1 is that the gap D between the electrode assembly and the inner side of the pressure relief mechanism is different, and the mass of the positive active material is different.

[0288] Wherein, the size of the battery cell with different capacity can be adaptively adjusted according to the mass of the positive active material and the gap D.

[0289] Embodiment 14

[0290] Example 14 differs from Example 1 in that the porosity of the separator film is different, and the porosity of the separator film is 48%; in addition, due to the change in the porosity of the separator film, the mass of the electrolyte added in the battery cell and the injection coefficient also change. In Example 14, the injection coefficient is 1.4 g / Ah.

[0291] Comparative Example 1

[0292] Comparative Example 1 differs from Example 1 in that the gap D is 3 mm.

[0293] The specific parameters of Examples 1-14 and Comparative Example 1 are shown in Table 2, and the test results are shown in Table 3. Among them, 10 battery cells are used for testing for each example and comparative example, and Table 3 shows the number of battery cells passing the needle penetration test. In Table 2, K is the mass of the electrolyte in the battery cell, A is the mass content of DMC in the electrolyte based on the total mass of the electrolyte, B is the mass content of LiFSI in the electrolyte based on the total mass of the electrolyte, A:B is the mass content ratio of DMC and LiFSI, G is the mass of the positive active material, G0 is the mass of the positive electrode film layer, D is the gap between the electrode assembly and the inner side of the pressure relief mechanism along the thickness direction of the end cover, Q is the capacity of the battery cell, and C is the ratio of the mass of the electrolyte to the capacity of the battery cell. Table 2 Specific parameters of Examples 1-14 and Comparative Example 1 Table 3 Test results of Examples 1-14 and Comparative Example 1

[0294] Example 15

[0295] Example 15 differs from Example 1 in that the compaction density of the positive electrode sheet is different, and the porosity of the positive electrode sheet is different; in addition, due to the change in the compaction density of the positive electrode sheet, the mass of the electrolyte added in the battery cell also changes.

[0296] Example 16

[0297] Example 16 differs from Example 1 in that the compaction density of the negative electrode sheet is different, and the porosity of the negative electrode sheet is different; in addition, due to the change in the compaction density of the negative electrode sheet, the mass of the electrolyte added in the battery cell also changes.

[0298] In the case of the change in the mass of the positive active material, the mass of the negative active material needs to be adjusted adaptively. In Example 15, the compaction density of the positive electrode sheet and the mass of the positive active material are small, and correspondingly, the mass of the negative active material is small, the thickness of the negative film layer in the negative electrode sheet is adjusted adaptively, and the negative electrode sheet can maintain a high compaction density. In Example 16, the compaction density of the negative electrode sheet and the mass of the negative active material are small, and correspondingly, the mass of the positive active material is small, the thickness of the positive film layer in the positive electrode sheet is adjusted adaptively, and the positive electrode sheet can maintain a high compaction density.

[0299] Example 17

[0300] Example 17 is different from Example 1 in that the compaction densities of the positive electrode sheet and the negative electrode sheet are different, and the porosities of the positive electrode sheet and the negative electrode sheet are different; in addition, due to the change in the compaction densities of the positive electrode sheet and the negative electrode sheet, the mass of the electrolyte added in the battery cell also changes.

[0301] The specific parameters of Examples 15-17 are shown in Table 4, and the test results are shown in Table 5. Among them, 10 battery cells are tested for each example and the comparative example, and Table 5 shows the number of battery cells passing the needle test. In Table 4, G is the mass of the positive active material, G1 is the mass of the negative active material, D is the gap between the electrode assembly and the inside of the pressure relief mechanism along the thickness direction of the end cover, Q is the capacity of the battery cell, and C is the ratio of the mass of the electrolyte to the capacity of the battery cell. Table 4 Specific parameters of Examples 15-17 Table 5 Test results of Examples 15-17

[0302] [Preparation of battery cell]

[0303] Preparation of positive electrode sheet: mix the positive active material LiNi0.9Co0.06Mn0.04O2, the binder polyvinylidene fluoride (PVDF), the conductive agent (carbon black), and the conductive agent carbon nanotube (CNT) in a mass content ratio of 97.5:1.0:1.0:0.5 uniformly, dissolve in the solvent N-methyl pyrrolidone (NMP), and after sufficient stirring and mixing, prepare a positive electrode slurry; uniformly coat the positive electrode slurry on the opposite two surfaces of the positive current collector aluminum foil, and then perform drying, cold pressing, and slitting to obtain a positive electrode sheet.

[0304] Preparation of the negative electrode sheet: the negative electrode active material graphite and the silicon-carbon composite material were mixed according to a mass content ratio of 95:5, and the mixed negative electrode active material, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickening agent sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water according to a mass content ratio of 96.5:0.9:1.5:1.1, and then the mixture was fully stirred and uniformly mixed to prepare a negative electrode slurry; the negative electrode slurry was coated on the negative electrode current collector copper foil, and then the coated copper foil was subjected to drying, cold pressing, and slitting to obtain the negative electrode sheet.

[0305] Separator film: a polyethylene film with a thickness of 9 μm was used as the base film, and a 3 μm ceramic coating layer was provided on the side of the base film facing the positive electrode sheet.

[0306] Preparation of the electrolyte: ethylene carbonate (EC), methyl ethyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed according to the requirements in Table 2, and then LiPF6 and LiFSI were mixed according to a mass content ratio of 1:1 and uniformly dissolved in the above solution to obtain the electrolyte; in addition, 2% of FEC additive based on the total mass of the electrolyte was added to the electrolyte.

[0307] Preparation of the battery monomer: the above positive electrode sheet, the separator film, and the negative electrode sheet were stacked and wound in sequence to obtain an electrode assembly; the electrode assembly was placed in a shell, and the above prepared electrolyte was added, and then the battery monomer was obtained after packaging, standing, formation, aging, and other processes.

[0308] [Parameter testing method of the battery monomer]

[0309] The tested battery monomer can be a battery monomer that has just been assembled and has not been formed, or a battery monomer that has been removed from a power device (such as a vehicle).

[0310] (1) Test of the capacity of the battery monomer

[0311] The capacity of the battery monomer can be tested by a charge-discharge machine. Specifically, the battery monomer was tested by charging and discharging at a current density of 0.33 C in a voltage range of 2.5 V-4.25 V, and the discharge capacity of the third cycle was recorded as the actual capacity of the battery monomer after 3 cycles.

[0312] The capacity of the battery monomer obtained by the test has a certain deviation, which is about 5% within a floating range.

[0313] (2) Test of the fast charging performance of the battery monomer

[0314] The battery monomer is made into a three-electrode battery monomer for fast charging performance test. Specifically, the electrode assembly is prepared by winding in the order of positive electrode sheet, separator, third electrode (the third electrode is selected from copper wire), separator, and negative electrode sheet. Then, the electrode assembly is placed in an outer package, and the above prepared electrolyte is added. After packaging, standing, formation, aging and other processes, the battery monomer is obtained. The remaining preparation steps can be referred to the description above, and will not be repeated here.

[0315] The battery is charged at different states of charge (SOC). The maximum charging current corresponding to each different SOC is measured and recorded at 10% SOC, 20% SOC, 30% SOC, 40% SOC, 50% SOC, 60% SOC, 70% SOC, and 80% SOC. The time from 10% SOC to 80% SOC at the maximum charging current is recorded, which measures the fast charging performance of the battery monomer.

[0316] The maximum charging current corresponding to different SOC can be obtained by selecting different current densities to charge the battery monomer. The SOC when the anode potential is charged to 0mV at this current is recorded, and the current corresponds to the maximum charging current of the SOC.

[0317] (3) Test of the volume energy density of the battery monomer

[0318] The height of the battery monomer and the diameter of the end cap are tested. The area of the end cap is calculated according to the diameter of the end cap, and the volume of the battery monomer is the area of the end cap x the height of the battery monomer.

[0319] The volume energy density of the battery monomer = the energy of the battery monomer / the volume of the battery monomer.

[0320] The energy of the battery monomer is measured by charging and discharging test of the battery monomer at a current density of 0.33C in the voltage range of 2.5V-4.25V. After 3 cycles, the discharge energy of the third cycle is recorded as the energy of the battery monomer. The unit of the energy of the battery monomer is Wh, and the unit of the capacity of the battery monomer is Ah.

[0321] (4) Test of the needle puncture test of the battery monomer

[0322] The reliability of the battery monomer can be tested by the needle puncture test, and the specific method is as follows:

[0323] A steel needle with a diameter of 3 mm is inserted into the largest surface of the battery cell at a speed of 0.1 mm / s until thermal runaway occurs. It is observed whether the pressure relief mechanism breaks and whether the electrode terminal flies out or the shell breaks. A group of battery cells, including 10 battery cells, can be used for testing, and the probability of the above-mentioned conditions occurring in the battery cells is observed.

[0324] (5) Test of the diameter of the end cap, the area defined by the pressure relief mechanism, the height of the battery cell, and the gap D in the battery cell

[0325] The battery cell is subjected to CT scanning, and the scanned image is tested.

[0326] According to the scanned image, the diameter of the end cap, the height of the battery cell, and the diameter R of the circular area defined by the pressure relief mechanism can be measured. The area defined by the pressure relief mechanism can be calculated by the formula S = π × (R / 2)2.

[0327] According to the scanned image, the gap D is tested along the thickness direction of the end cap. Specifically, in the area defined by the pressure relief mechanism, 5 points are selected along the thickness direction of the end cap on the side of the pressure relief mechanism close to the electrode assembly. 5 points are selected along the thickness direction of the end cap on the end of the negative electrode tab in the electrode assembly close to the end cap, which correspond to the 5 points selected on the pressure relief mechanism along the thickness direction of the end cap. The average distance between the 5 points selected on the pressure relief mechanism and the 5 points selected on the electrode assembly is calculated, and this average value is taken as the value of the gap D.

[0328] (6) Test of the injection coefficient, the mass of the electrolyte, the mass content of DMC, and the mass content of LiFSI

[0329] i) The mass of the electrolyte before formation is the mass of the electrolyte injected into the battery cell during the preparation of the battery cell.

[0330] The injection coefficient of the electrolyte before formation is the ratio of the mass of the electrolyte before formation to the nominal capacity of the battery cell.

[0331] The mass content of DMC and the mass content of LiFSI can be calculated according to the mass of DMC and the mass of LiFSI added during the preparation of the electrolyte.

[0332] ii) After the battery cell has undergone a certain number of charge and discharge cycles, the injection coefficient, the mass of the electrolyte, the mass content of DMC, and the mass content of LiFSI can be obtained as follows.

[0333] The battery cell is disassembled, the electrode assembly is taken out and dried, and the mass of the electrolyte in the battery cell after cycling is calculated according to the total mass of the battery cell before disassembly minus the total mass of the electrode assembly after disassembly.

[0334] After cycling, the injection coefficient is the mass of the electrolyte after cycling divided by the nominal capacity of the battery cell.

[0335] The battery cell is disassembled, the electrolyte in the battery cell is taken out, and the organic components in the electrolyte are quantitatively analyzed by gas chromatography according to standard GB / T9722-2006, and the inorganic components / lithium salt concentration in the electrolyte is quantitatively analyzed by ion chromatography according to standard JY / T020-1996.

[0336] (7) Test of voltage platform

[0337] Voltage platform = discharge energy of battery cell / discharge capacity of battery cell. The test of discharge energy and discharge capacity is shown in test methods (3) and (1).

[0338] (8) Test of positive active material, negative active material, and separator material

[0339] The positive active material, negative active material, and separator material can be determined according to the materials selected in the process of preparing the battery cell.

[0340] After the battery cell has been cycled for a certain number of times, the battery cell can be disassembled, the electrode assembly is taken out, and the positive electrode sheet, negative electrode sheet, and separator are obtained. The sample (such as the positive electrode sheet, negative electrode sheet, or separator) is placed on a sample stage, and the types of elements and the proportion of elements in the sample can be determined by using a scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS), and the material composition in the sample can be determined according to the types of elements and the proportion of elements.

[0341] (9) Mass per unit area of positive active material / negative active material

[0342] The mass per unit area of the positive active material is the ratio of the mass of the positive active material added in the process of preparing the battery cell to the area of the coating area of the positive electrode sheet; and the mass per unit area of the negative active material is the ratio of the mass of the negative active material added in the process of preparing the battery cell to the area of the coating area of the negative electrode sheet.

[0343] (10) Test of compaction density

[0344] Take the pole piece with an area of s1, measure its thickness h1, and weight m1; take the same area of aluminum foil, whose thickness is h2, and weight is m2; the compaction density of the pole piece = (m1-m2) / [s1x(h1-h2)], unit g / cm 3 .

[0345] The measurement deviation of compaction density is within ±0.05 g / cm 3 .

[0346] (11) Test of porosity

[0347] Cut the sample into a size of 3mmx3mm, measure the apparent volume V0 of the sample (the apparent volume of the sample is the thickness of the sample x the area of the sample); then use the true density instrument to test the true volume of the sample, specifically, put the sample into the sample test cavity, and introduce nitrogen into the sample test cavity, and connect the sample test cavity with the reference cavity and record the stable pressure, according to the pressure before the reference cavity and the sample cavity are connected and the pressure after the reference cavity and the sample cavity are connected stably and the Boyle's law PV=nRT to calculate the volume of the pore. The porosity of the sample = pore volume / apparent volume.

[0348] The fast charging performance of the battery cell in the present application can be embodied by the charging time required from 10% SOC to 80% SOC, the shorter the charging time, the better the fast charging performance of the battery cell; the reliability of the battery cell can be embodied by the number of battery cells passing the needle test, the more the number of battery cells passing the needle test, the higher the reliability of the battery cell.

[0349] As shown in Examples 1-14 and Comparative Example 1, in the case of setting a gap D between the electrode assembly and the inside of the pressure relief mechanism in the thickness direction of the end cover to be greater than or equal to 4 mm, the battery cell requires a shorter time from charging from 10% SOC to 80% SOC, the battery cell has better fast charging performance, and at the same time, in the case of the needle test of the battery cell, the pressure relief mechanism can be actuated and ruptured in time, the risk of the electrode terminal being separated from the shell and the shell being broken is lower, and the battery cell has higher reliability; in addition, by setting the gap D to be less than or equal to 10 mm, the battery cell can also improve the fast charging performance and reliability of the battery cell while reducing the waste of space inside the battery cell, and the battery cell has higher volumetric energy density.

[0350] As shown in Examples 15-17, the compaction density of the positive electrode pole piece is greater than or equal to 3.55 g / cm 3 , and / or, the compaction density of the negative electrode pole piece is greater than or equal to 1.5 g / cm 3 , which helps to further improve the energy density of the battery cell while maintaining good fast charging performance and reliability.

[0351] In combination with the embodiments 1-3, when the gap D is 6mm-10mm, the battery cell has a higher energy density and fast charging performance, and when the battery cell is in thermal runaway, the risk of electrode terminal disengaging from the shell and the shell breaking is lower, and the battery cell has higher reliability. In combination with the embodiments 12-13, when the gap D is 4mm-5mm, by reducing the mass of the positive active material or the mass of the electrolyte in the battery cell, the risk of electrode terminal disengaging from the shell and the shell breaking is lower, and the battery cell has higher reliability.

[0352] In combination with the embodiments 1 and 4-7, when the ratio A:B of the mass content A of DMC and the mass content B of LiFSI based on the total mass of the electrolyte is 3-16, the battery cell has better fast charging performance and higher reliability; in combination with the embodiments 1, 4, 5 and 6-7, when A:B is 3-10, the battery cell has higher reliability on the premise that the battery cell has better fast charging performance.

[0353] In combination with the embodiments 1 and 8-10, when the mass of the electrolyte is 30g-60g, the battery cell has better fast charging performance and reliability; in combination with the embodiments 1, 8-9, when the mass of the electrolyte is 35g-50g, the battery cell has higher reliability on the premise that the battery cell has better fast charging performance.

[0354] In combination with the embodiments 8-10, when the ratio C of the mass of the electrolyte to the capacity of the battery cell is ≤1.6g / Ah, the battery cell has higher fast charging performance and higher reliability; when C is greater than 1.6g / Ah, the reliability of the battery cell can be improved by increasing the gap D; when 1.2g / Ah≤C≤1.4g / Ah, the battery cell has higher reliability and better fast charging performance.

[0355] In combination with the embodiments 11-13, different capacities of the battery cell can be designed with different masses of the electrolyte, different masses of the positive active material, and different gaps D to improve the reliability of the battery cell.

[0356] In combination with the embodiments 1-13, when 4g / mm≤K / D≤11g / mm, the battery cell has better fast charging performance and higher reliability; in combination with the embodiments 1-2 and 4-9, when 6g / mm≤K / D≤8.5g / mm, the battery cell also has higher energy density.

[0357] In combination with the examples 1-13, the battery cell has a higher energy density and a higher reliability when 15 g / mm≤G0 / D≤42 g / mm; in combination with the examples 1-2 and 4-10, the battery cell has a higher energy density and a higher reliability when 20 g / mm≤G0 / D≤27 g / mm.

[0358] In combination with the examples 1 and 14, the battery cell can have a better fast-charging performance and a higher reliability when the separator film has a porosity less than or equal to 45%.

[0359] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. Furthermore, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art, other modes constructed by combining part of the configuration elements of the embodiments are also included in the scope of the present application.

Claims

A battery cell characterized by The battery cell comprises: an electrode assembly; a housing; an end cover, the housing and the end cover forming a space accommodating the electrode assembly, the end cover being provided with a pressure relief mechanism; an electrolyte, the electrolyte comprising a solvent and an electrolyte salt, the solvent comprising dimethyl carbonate, the electrolyte salt comprising a lithium bisfluorosulfonylimide salt; a gap D between the electrode assembly and an inner side of the pressure relief mechanism in a thickness direction of the end cover satisfying 4 mm≤D≤10 mm; a capacity Q of the battery cell satisfying 30 Ah≤Q≤40 Ah. The battery cell of claim 1, wherein 6 mm≤D≤8 mm. The battery cell according to claim 1 or 2, characterized in that, A mass content A of the dimethyl carbonate satisfies 20 wt%≤A≤60 wt% based on a total mass of the electrolyte; and / or, a mass content B of the lithium bisfluorosulfonylimide salt satisfies 2 wt%≤B≤16 wt% based on the total mass of the electrolyte. The battery cell according to claim 3, characterized in that 20 wt%≤A≤45 wt%; and / or, 2.5 wt%≤B≤11 wt%. The battery cell according to claim 3 or 4, characterized in that A mass content ratio A:B of the dimethyl carbonate and the lithium bisfluorosulfonylimide satisfies 3≤A:B≤16. The battery cell according to claim 5, wherein 3≤A:B≤10. The battery cell of any one of claims 1-6, wherein In the battery cell, a ratio C of a mass of the electrolyte to a capacity of the battery cell satisfies C≤1.6 g / Ah. The battery cell according to claim 7, characterized in that 1.2 g / Ah≤C≤1.4 g / Ah. The battery cell of any one of claims 1-8, wherein, A ratio E of a mass of the electrolyte remaining in the battery cell to the capacity of the battery cell after the battery cell is cycled for 1000 times satisfies 0.7 g / Ah≤E≤1.1 g / Ah. The battery cell of any one of claims 1-9, wherein, A size H of the battery cell in the thickness direction of the end cover satisfies 90 mm≤H≤120 mm. The battery cell of any one of claims 1-10, wherein In the battery cell, a mass K of the electrolyte satisfies 30 g≤K≤60 g. The battery cell of claim 11, wherein 35 g≤K≤50 g. The battery cell of any one of claims 1-12, wherein A mass P of the electrolyte remaining in the battery cell after the battery cell is cycled for 1000 times satisfies 22 g≤P≤36 g. The battery cell of any one of claims 1-13, wherein, In the battery cell, the mass K of the electrolyte and the gap D satisfy 4 g / mm≤K / D≤11 g / mm. The battery cell of claim 14, wherein 6 g / mm≤K / D≤8.5 g / mm. The battery cell of any one of claims 1-15, wherein, The electrode assembly includes a positive electrode tab and a negative electrode tab, the positive electrode tab having a compacted density greater than or equal to 3.55 g / cm 3 , and / or the negative electrode tab having a compacted density greater than or equal to 1.5 g / cm 3 . The battery cell of claim 16, wherein The positive electrode sheet has a compacted density of 3.55 g / cm 3 ~ 3.7 g / cm 3 , and / or the negative electrode sheet has a compacted density of 1.5 g / cm 3 ~ 1.7 g / cm 3 . The battery cell of claim 16, wherein The positive electrode sheet has a compaction density of 3.35 g / cm 3 ~ 3.69 g / cm 3 and / or the negative electrode sheet has a compaction density of 1.3 g / cm 3 ~ 1.65 g / cm 3 . The battery cell of any one of claims 16-18, wherein A porosity of the positive electrode sheet is 22% to 26%, and / or, a porosity of the negative electrode sheet is 23% to 27%. The battery cell according to any one of claims 16-19, characterized in that The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, a mass G0 of the positive electrode film layer and the gap D satisfy 15 g / mm≤G0 / D≤42 g / mm. The battery cell of claim 20, wherein 18 g / mm≤G0 / D≤28 g / mm. The battery cell according to claim 20 or 21, characterized in that The positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprising a lithium nickel oxide or a metal phosphate. The battery cell of claim 22, wherein The chemical formula of the lithium nickel oxide satisfies: Li 1+a [Ni x Co y Mn z M b ]O 2-c , M includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.2≥a≥-0.2, 1>x≥0.7, 0.3>y>0, 0.3>z>0, 0.3>b≥0, 0.5≥c≥0. The battery cell according to claim 22 or 23, characterized in that In the battery cell, the gram weight per unit area of the positive electrode active material is 15 mg / cm 2 ~ 23 mg / cm 2 . The battery cell of any one of claims 16-24, wherein The negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprising graphite and a silicon-containing material, the silicon-containing material comprising at least one of elemental silicon, a silicon-oxygen composite, a silicon-carbon composite, a silicon-nitrogen composite, a silicon-containing alloy or a silicon-oxygen-carbon composite material, the graphite comprising at least one of natural graphite or artificial graphite. The battery cell of claim 25, wherein A mass content of the silicon-containing material is 1 wt% to 20 wt% based on a total mass of the negative electrode active material. The battery cell according to claim 25 or 26, characterized in that The silicon-containing material includes a silicon-carbon composite, and a mass percentage of silicon in the silicon-carbon composite is 40wt%-60wt% based on a total mass of the silicon-containing material. The battery cell of any one of claims 25-27, wherein In the battery cell, the gram weight per unit area of the negative electrode active material is 8 mg / cm 2 ~ 13 mg / cm 2 . The battery cell of any one of claims 16-28, wherein The electrode assembly further includes a separator film disposed between the positive electrode tab and the negative electrode tab, and the separator film includes a base film and a ceramic coating disposed on a side of the base film facing the positive electrode tab. The battery cell of claim 29, wherein The porosity of the separator film is 30%-45%. The battery cell of any one of claims 1-30, wherein The end cover includes an end cover body, and the pressure relief mechanism is disposed on an inner side or an outer side of the end cover body. The battery cell of claim 31, wherein The end cover body is provided with a score groove, and an area defined by the score groove forms the pressure relief mechanism. The battery cell of any one of claims 1-32, wherein An area S defined by the pressure relief mechanism and an area S0 of the end cover satisfy 25%≤S / S0≤50%. The battery cell of any one of claims 1-33, wherein, The area S of the region defined by the pressure relief mechanism and the capacity Q of the battery cell satisfy: 12 mm 2 / Ah≤ S / Q≤ 20 mm 2 / Ah. The battery cell of any one of claims 1-34, wherein, The pressure relief mechanism defines an area S greater than or equal to 500 mm 2 . The battery cell of claim 35, wherein 600 mm 2 ≤ S ≤ 800 mm 2 . The battery cell of any one of claims 1-36, wherein The voltage plateau of the battery cell is 3.5V-3.7V. The battery cell of any one of claims 1-37, wherein, The solvent further includes methyl ethyl carbonate and ethylene carbonate, and the electrolyte salt further includes lithium hexafluorophosphate. The battery cell of any one of claims 1-38, wherein The electrolyte further includes an additive, and the additive includes at least one of fluoroethylene carbonate or vinylene carbonate. The battery cell of any one of claims 1-39, wherein, The battery cell further includes a current collecting member accommodated in the housing, located between the electrode assembly and the end cover in a thickness direction of the end cover, and electrically connected to the tab of the electrode assembly and the housing. The battery cell of claim 40, wherein An inner side of the housing is provided with a limiting portion located between the electrode assembly and the end cover in the thickness direction of the end cover, and the current collecting member abuts against a side of the limiting portion facing the electrode assembly. The battery cell according to claim 40 or 41, characterized in that The battery cell further includes a sealing member disposed between the end cover and the housing. The battery cell of any one of claims 1-42, wherein, The battery cell is a cylindrical battery cell. A battery characterized by Comprising: The battery cell according to any one of claims 1-43. An electric power utilization device characterized by comprising: Comprising: The battery according to claim 44.

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