Battery cell and battery

Abstract

A battery cell, characterized in that it comprises: a battery cell body and a foil envelope (10), wherein the foil envelope (10) is wrapped on the outside of the battery cell body, wherein the battery cell body comprises a negative electrode (20) comprising a first current collector (21) and a first coating (22) comprising graphite, wherein the foil envelope (10) has a plurality of corner portions (11) comprising a first edge corner portion (12), a second edge corner portion (13), and a third edge corner portion (14) that intersect each other; wherein the foil envelope (10) and the battery cell body satisfy the following condition: 750 ≤ (a × b × c) / (Wa × Wb × Wc) ≤ 90000; where Wa=Ka / H; Wb=Kb / H; Wc=Kc / H, where Ka is the inverse parameter of the first edge corner portion (12); Kb is the inverse parameter of the second edge corner portion (13); Kc is the inverse parameter of the third edge corner portion (14); H is the punching depth of the foil sleeve (10); a is the orientation index O1 value of the graphite in the first coating (22); b is the tensile strength of the first current collector (21); c is the thickness of the first current collector (21).

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery cell and a battery. BACKGROUND TECHNOLOGY

[0002] With the development of new energy technology, people hope that electronic products will become lighter and smaller, which puts higher requirements on the energy density of batteries, and there is an urgent demand for lithium-ion batteries with high energy and long cycle life.

[0003] In the pursuit of energy density, the means commonly used are increasing the specific capacity of the main material, reducing the thickness of the auxiliary material, compressing the volume of the foil wrap, and narrowing the gap between the wound core and the foil wrap. However, as the wound core and the volume of the foil wrap are reduced, the electrode expands at a certain rate, that is, the electrode size increases. The expansion of the electrode itself will interfere with the foil wrap surrounding the wound core, making it easy to cause the foil wrap to rupture during the battery's charge and discharge cycle, thereby affecting the battery's service life.

[0004] It is therefore urgently necessary to solve the technical problem that the foil cover is prone to tearing and damage, which affects the battery life. DISCLOSURE OF THE INVENTION

[0005] The present application relates to a battery cell and a battery to solve the technical problem that the foil envelope is prone to tearing and damage, thereby affecting the service life of the battery.

[0006] To achieve the above objective, the present application provides a battery cell comprising: a battery cell body and a foil wrapper, wherein the foil wrapper is wrapped on the outside of the battery cell body, wherein the battery cell body comprises a negative electrode including a first current collector and a first coating comprising graphite, wherein the foil wrapper has a plurality of corner portions including a first edge corner portion, a second edge corner portion, and a third edge corner portion that intersect each other; wherein the foil wrapper and the battery cell body satisfy the following condition: 750≤(a×b×c) / (Wa×Wb×Wc)≤90000; where Wa=Ka / H; Wb=Kb / H; Wc=Kc / H, where Ka is the inverse parameter of the first edge corner portion; Kb is the inverse parameter of the second edge corner portion; Kc is the inverse parameter of the third edge corner portion; H is the punching depth of the foil wrapper;a is the orientation index Oi value of the graphite in the first coating; b is the tensile strength of the first current collector; c is the thickness of the first current collector.;

[0007] In the battery cell provided by the present application, the extensibility of the negative electrode is taken into account in the design of the corner portion of the foil can, so that the corner portion is better adapted to the space occupied by the battery cell body. This improvement not only increases the volume of the foil can but also reduces the stress concentration at the corner portion. During the charge and discharge cycle of the battery cell, reducing the stress concentration at the corner portion reduces the risk of corner cracks at the corner portion, thereby improving the safety performance of the battery cell. Furthermore, increasing the volume of the foil can also improves the energy density of the battery.

[0008] In one possible embodiment, the Ol value a of the graphite in the first coating, the tensile strength b of the first current collector and the thickness c of the first current collector satisfy the following condition: 20≤a 2 ×b×c / 10000.

[0009] In one possible embodiment, the film sleeve comprises a top wall and a plurality of side walls connected to the edge of the top wall, wherein the plurality of side walls comprise adjacent first side walls and second side walls, wherein the junction between the top wall and the first side wall forms the first edge corner section, the junction between the top wall and the second side wall forms the second edge corner section, and the junction between the first side wall and the second side wall forms the third edge corner section; wherein the ratio of the inverse parameter of the first edge corner section to the punching depth of the film sleeve Wa, the ratio of the inverse parameter of the second edge corner section to the punching depth of the film sleeve Wb, and the ratio of the inverse parameter of the third edge corner section to the punching depth of the film sleeve Wc satisfy the following conditions: Wa≤Wc, Wb≤Wc, 1≤Wa≤8, 1≤Wb≤8, 1≤Wc≤8.

[0010] In one possible embodiment, the first coating further comprises a silicon-based material, wherein the ratio of the weight S1 of the silicon-based material to the total weight S2 of the first coating satisfies the following condition: 0≤S1 / S2≤20%.

[0011] In one possible embodiment, the Ol value a of the graphite in the first coating satisfies the following condition: 8≤a≤30.

[0012] In one possible embodiment, the tensile strength b of the first current collector satisfies the following condition: 300 MPa≤b≤700 MPa.

[0013] In one possible embodiment, the thickness c of the first current collector satisfies the following condition: 1µm≤c≤15µm.

[0014] In one possible embodiment, the thickness c of the first current collector satisfies the following condition: 3µm≤c≤7µm.

[0015] In one possible embodiment, the first coating further comprises a silicon-based material, wherein the silicon-based material comprises at least one silicon oxide material having the general chemical formula M y SiO x wherein 0≤y≤4, 0≤x≤4, and M comprises at least one of the following elements: Li, Mg, Ti and Al.

[0016] In one possible embodiment, the punching depth H of the film sleeve during the punching forming process is 2 mm to 5.5 mm.

[0017] The present application also provides a battery comprising a housing and the battery cell described above, wherein the battery cell is arranged in the housing.

[0018] In the battery cell and battery provided by the present application, the silicon material content can be effectively controlled by controlling the value of S1 / S2. By controlling the silicon material content, excessive elongation of the negative electrode 20 due to excessive silicon material content can be avoided, and the extensibility of the negative electrode 20 can be kept within a reasonable range. This ensures the energy density of the battery and reduces the risk of breakage of the corner portion 11.

[0019] In addition to the technical problems solved by the embodiments of the present application, the technical features constituting the technical solutions, and the advantageous effects brought about by the technical features of the technical solutions described above, other technical problems that can be solved by a battery cell and a battery provided by the embodiments of the present application, other technical features included in the technical solutions, and the advantageous effects brought about by these technical features will be described in further detail in the specific embodiments. DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings required in the description of the embodiments or the prior art are briefly explained below. It is obvious that the drawings presented in the following description relate only to some embodiments of the present application. Those skilled in the art can derive further drawings from them without inventive step. Fig. 1 shows a schematic representation of the three-dimensional structure of a foil casing of a battery cell according to an embodiment of this application; Fig. 2 shows a front view of a foil cover of a battery cell according to an embodiment of this application; Fig.3 shows a schematic representation of the structure of a negative electrode of a battery cell according to an embodiment of this application. Description of reference symbols in the drawings: 10 foil sleeves; 11 corner section; 12 First edge corner section; 121 First transition rounding; 13 Second edge corner section; 131 Second transitional rounding; 14 Third edge corner section; 141 Third transitional rounding; 15 First side wall; 16 Second side wall; 17 ceiling wall; 20 negative electrode; 21 First current collector; 22 First coating. D Pull-out direction of the contact tab DETAILED DESIGNS

[0021] To more clearly illustrate the objectives, technical solutions, and advantages of this application, the technical solutions of this application are described below clearly and comprehensively with reference to the accompanying drawings. It is understood that the described embodiments represent only a portion of the embodiments of this application, and not all of them. Starting from the embodiments of this application, all other embodiments that a person skilled in the art can derive without inventive step fall within the scope of this application.

[0022] When reducing the winding core and the volume of the foil sheath, it was found that the electrode stretches in a certain ratio in the length, width, and thickness directions. This stretching of the electrode itself causes interference with the foil sheath, and the foil sheath is compressed during the cycle due to the breathing effect. According to the analysis of the principle of tensile stress and strain of metals, the aluminum-plastic foil will rupture when the tensile stress and strain of the aluminum-plastic foil passes through the plastic deformation stage and the tensile stress reaches the peak value of the tensile strength.

[0023] In this application, batteries with different expandability are combined with different corner space designs, so that the space at the rounded corner area of ​​the film wrapper better matches the space of the winding core. This improvement can not only effectively reduce the risk of damage at the corner section position to ensure safety performance, but can also increase the energy density of the battery.

[0024] This application provides a battery cell, wherein, as in Fig. 1 and Fig.3, the battery cell comprises a battery cell body and a foil envelope 10, wherein the foil envelope 10 is wrapped on the outside of the battery cell body, wherein the battery cell body comprises a negative electrode 20, the negative electrode 20 comprises a first current collector 21 and a first coating 22, and the first coating 22 comprises graphite, wherein the foil envelope 10 has a plurality of corner sections 11, and the corner sections 11 comprise a first edge corner section 12, a second first edge corner section 13 and a third first edge corner section 14 that intersect each other; wherein the foil envelope 10 and the battery cell body satisfy: 750≤(a×b×c) / (Wa×Wb×Wc)≤90000; where Wa=Ka / H; Wb=Kb / H; Wc=Kc / H, where Ka is the inverse parameter of the first edge corner portion 12; Kb is the inverse parameter of the second edge corner portion 13; Kc is the inverse parameter of the third edge corner portion 14; H is the punching depth of the foil sleeve 10; a is the orientation index O1 value of the graphite in the first coating 22; b is the tensile strength of the first current collector 21; c is the thickness of the first current collector 21.

[0025] Typically, the position of the corner portion of the foil wrapper is prone to damage. Therefore, this application provides a battery cell in which the extensibility of the negative electrode 20 is taken into account in the design of the corner portion 11 of the foil wrapper 10, so that the corner portion 11 is better adapted to the space occupied by the battery cell body. This improvement not only increases the volume of the foil wrapper 10 but also reduces the stress concentration at the position of the corner portion 11. During the charge and discharge cycle of the battery cell, reducing the stress concentration at the position of the corner portion 11 reduces the risk of corner cracks at the corner portion 11, thereby improving the safety performance of the battery cell. Furthermore, increasing the volume of the foil wrapper 10 also improves the energy density of the battery.

[0026] The changes in the tensile strength b of the first current collector 21, the thickness c of the first current collector 21, and the Oi value a of the graphite in the first coating 22 affect the expandability of the first coating 22, and the changes in Wa, Wb, and Wc affect the spatial volume of the foil shell 10 at the position of the corner portion 11. Controlling (a×b×c) / (Wa×Wb×Wc) within a certain range enables the expandability of the negative electrode 20 and the space of the foil shell 10 to better match, thus significantly reducing the risk of corner cracks at the corner portion 11 of the battery cell.

[0027] In one possible embodiment, which is a double-trough battery cell, the corner section 11 represents the corner section of the deep-trough side. Accordingly, the punching depth H refers to the punching depth of the deep-trough side.

[0028] In one possible embodiment, the contact tab protrudes in the Fig. 1 indicated direction D out of the cover wall 17.

[0029] It is to be understood that the first edge corner portion 12 refers to the upper R corner or the lower R corner, the second edge corner portion 13 refers to the 4R corner, and the third edge corner portion 14 refers to the side R corner.

[0030] In this example, the foil envelope 10 may be an aluminum-plastic foil envelope, with the first current collector 21 being made of copper foil.

[0031] In one possible embodiment, the first coating 22 comprises at least one material from the group consisting of: artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, organic polymer compound carbon, lithium titanate, silicon oxide and silicon carbon, or a combination thereof.

[0032] In one possible embodiment, the Oi value a of the graphite in the first coating 22, the tensile strength b of the first current collector 21 and the thickness c of the first current collector 21 satisfy the following condition: 20≤a 2 ×b×c / 10000. This design allows the first current collector 21 to have a certain ability to achieve the effect of reducing the elongation of the first coating 22. This design effectively reduces the degree of elongation of the negative electrode 20 during charging and discharging, thereby reducing the risk of corner cracks at the corner portion 11 and thus improving the safety performance of the battery cell. Furthermore, this design can also improve the energy density of the battery.

[0033] For example, the value of a 2 ×b×c / 10000 can be 20, 25, 30, 42 or 50 etc.

[0034] In one possible embodiment, the film sleeve 10 comprises a top wall 17 and a plurality of side walls connected to the edge of the top wall 17, wherein the plurality of side walls comprise adjacent first side wall 15 and second side wall 16, wherein the connection point between the top wall 17 and the first side wall 15 forms the first edge corner section 12, the connection point between the top wall 17 and the second side wall 16 forms the second edge corner section 13, and the connection point between the first side wall 15 and the second side wall 16 forms the third edge corner section 14.

[0035] The ratio Wa of the inversion parameter of the first edge corner portion 12 to the punching depth of the film sleeve 10, the ratio Wb of the inversion parameter of the second edge corner portion 13 to the punching depth of the film sleeve 10, and the ratio Wc of the inversion parameter of the third edge corner portion 14 to the punching depth of the film sleeve 10 also satisfy the following conditions: Wa≤Wc, Wb≤Wc, 1≤Wa≤8, 1≤Wb≤8, 1≤Wc≤8.

[0036] In one possible embodiment, Wa can be 1, 2, 3, 4, 5, 5.5, 6, 7 or 8.

[0037] In one possible embodiment, Wb can be 1, 2, 3, 4, 5, 5.5, 6, 7 or 8.

[0038] In one possible embodiment, Wc can be 1, 2, 3, 4, 5, 5.5, 6, 7 or 8.

[0039] The inversion parameter is an input parameter used in the 3D drawing model software SolidWorks to generate the corner portion 11 of the film envelope 10, and the change of the inversion parameter directly affects the curved surface shape of the corner portion 11.

[0040] For a better understanding of the inverse parameter, reference is made to the Fig. 1 and Fig. 2 that the change in the inverse parameter Ka of the first edge corner portion 12 is reflected in the model as the change in the length of the first transition fillet 121 connected between the corner portion 11 and the first edge corner portion 12, and that the inverse parameter Ka of the first edge corner portion 12 is the distance from an end of the top wall 17 near the second edge corner portion 13 to an end of the first transition fillet 121 remote from the corner portion 11.

[0041] The change in the inverse parameter Kb of the second edge corner portion 13 is reflected in the model as the change in the length of the second transition fillet 131 connected between the corner portion 11 and the second edge corner portion 13, and the inverse parameter Kb of the second edge corner portion 13 is the distance from an end of the second side wall 16 near the third edge corner portion 14 to an end of the second transition fillet 131 remote from the corner portion 11.

[0042] The change in the inverse parameter Kc of the third edge corner portion 14 is reflected in the model as the change in the length of the third transition fillet 141 connected between the corner portion 11 and the third edge corner portion 14, and the inverse parameter Kc of the third edge corner portion 14 is the distance from an end of the first side wall 15 near the first edge corner portion 12 to an end of the third transition fillet 141 remote from the corner portion 11.

[0043] If the inversion parameter is too small, it will cause the corner portion 11 to form a sharp corner, resulting in stress concentration at the position of the corner portion 11 and thus easily causing the corner portion 11 to break; if the inversion parameter is too large, it will occupy the space of the corner regions, resulting in the space of the film shell 10 being reduced at the position of the corner portion 11 and thus not favorable for providing the energy density of the battery.

[0044] In this example, the film sleeve 10 has the shape of a cuboid, and the cover wall 17 has the shape of a rectangle, wherein the number of side walls is 4, the side walls each also have the shape of a rectangle, and the four side walls are each connected at the four side edges of the cover wall 17.

[0045] In this example, the first edge corner portion 12, the second edge corner portion 13, and the third edge corner portion 14 are all rounded edges.

[0046] In one possible embodiment, the first coating 22 further contains a silicon-based material, wherein the ratio of the weight S1 of the silicon-based material to the total weight S2 of the first coating 22 satisfies the following condition: 0 <S1 / S2<20%.

[0047] The first coating 22 is scraped off the first current collector 21 to obtain coating powder; the coating powder is tested by thermal gravimetric analysis (TGA) or inductively coupled plasma (ICP) to obtain the silicon content (i.e., the weight S1 of the silicon-based material), and thus the ratio of S1 and S2 is obtained.

[0048] In the negative electrode 20, the first coating 22 is adhered to the surface of the first current collector 21 via an adhesive layer. The first coating 22 comprises graphite and silicon materials. During charging and discharging, the phenomenon of silicon materials embedding in the graphite occurs, causing the first coating 22 to expand. However, the first current collector 21 also inhibits the expansion of the first coating 22 due to the adhesive force of the adhesive layer.

[0049] With the present application, the silicon material content can be effectively controlled by controlling the value of S1 / S2. By controlling the silicon material content, the degree of expansion of the negative electrode 20 can be avoided from being excessive due to excessive silicon material content, and thus the extensibility of the negative electrode 20 can be controlled within a reasonable range. In this way, the energy density of the battery is ensured and the risk of breakage of the corner portion 11 is reduced. The capacity of the battery can be increased by adding silicon material, which can significantly increase the energy density of the battery.

[0050] In one possible embodiment, the OI value a of the graphite in the first coating 22 satisfies the following condition: 8≤a≤30. For example, the OI value a of the graphite can be 8, 10, 15, 17.4, 20, 25, or 30, etc.

[0051] The Ol value a of graphite reflects the rate of embedding and de-embedding of lithium ions on the surface of the negative electrode 20. Specifically, the Ol value of graphite is the formation time of the oxide film on the surface of the negative electrode 20 during the charging and discharging process of lithium-ion batteries and is a parameter that indicates the degree of orderliness of the arrangement of the graphite layers in the graphite material.

[0052] It is easy to understand that the smaller the α value of the graphite in the first coating layer 22, the greater the elongation of the first coating layer 22 and the more likely it is to cause cracking problems in the corner portion 11. If the α value of the graphite is too large, this will result in excessive thickness swelling of the first coating layer 22. This is because the silicon material is mixed into the first coating layer 22, and the charging and discharging of the battery causes the silicon material to be embedded in the graphite, resulting in volume swelling of the graphite. The more silicon material is present, the greater the degree of elongation of the first current collector layer 21 and the more likely it is to cause corner cracking problems. Therefore, in the present application, by controlling α to satisfy 8≤a≤30, the degree of elongation of the negative electrode layer 20 can be controlled within a reasonable range.

[0053] In one possible embodiment, the tensile strength b of the first current collector 21 is designed to satisfy the following condition: 300 MPa≤b≤700MPa.

[0054] In the present application, the tensile strength b of the first current collector 21 is higher than the tensile strength of an existing current collector. It is easy to understand that increasing the tensile strength b of the first current collector 21 increases the inhibiting effect of the first current collector 21 on the expansion of the first coating 22, thus preventing a problem of the first coating 22 breaking and falling off due to excessive expansion of the first coating 22.

[0055] The tensile strength of the first current collector 21 can be achieved, for example, by changing the manufacturing process of the first current collector 21. In one possible embodiment, the tensile strength b of the first current collector 21 can be, for example, 300 MPa, 330 MPa, 380 MPa, 400 MPa, 510 MPa, 590 MPa, 600 MPa, 623 MPa, or 700 MPa, etc.

[0056] In this example, the first current collector 21 is a copper foil. Based on the tensile strength of lithium-ion battery copper foils, the copper foil is divided into the following categories: normal tensile strength (300-400 MPa), medium-high tensile strength (400-500 MPa), high tensile strength (500-600 MPa), and ultra-high tensile strength (>600 MPa).

[0057] The tensile strength of copper foil is affected by both thickness and grain size. When the thickness remains constant, the tensile strength increases with a decrease in grain size. When the grain sizes are comparable, the tensile strength is proportional to the thickness. Different rules apply to tensile strength at different thickness-to-grain ratios. When the thickness-to-grain ratio is small, such as less than 4, the tensile strength is proportional to the thickness. When the thickness-to-grain ratio is large, such as greater than 15, there is an inversely proportional relationship between tensile strength and thickness.

[0058] If the thickness of the copper foil remains constant, the tensile strength of the copper foil increases with the reduction of the grain size. This can be explained by the mechanism of fine-grain strengthening: In conventional polycrystalline materials, the free energy of the grain boundaries is very high, and compared to the grain interior, the grain boundary can be considered a barrier that hinders the movement of dislocations. Under the action of an external force, a sufficiently large shear stress must be generated at the grain boundary to cause shear deformation in neighboring grains.

[0059] Tensile strength is closely related to the transfer of slip from plastically deformed grains to neighboring grains. Whether this transfer can occur depends primarily on whether the stress concentration generated by the dislocation cluster near the grain boundary of the already slipped grain can activate the dislocation sources in the slip systems of the neighboring grain to set the neighboring grain in motion and cause coordinated multiple slip. Grain refinement can generate more grain boundaries, and if the grain boundary structure is not changed, a larger external force must be applied to generate the dislocation cluster, thereby strengthening the material.

[0060] Numerous studies and analyses have shown that a variety of additives can be added during the copper foil manufacturing process to optimize the microstructure of the copper foil, such as grain size, grain shape, orientation, internal stresses, etc., thus enabling the controlled production of copper foils with high mechanical properties. By refining the grains, selecting suitable crystal plane structures, increasing the purity of the solution, etc., the tensile strength and extensibility of high-tensile copper foils can be significantly improved.

[0061] Copper foils with high tensile strength and high extensibility can offer the following advantages: They can increase the efficiency of subsequent coating and rolling in battery factories and avoid strip breakage to increase production output; they can increase the charge amount of the active material of the first coating 22; they can increase the packing density of the electrodes and reduce the thickness of the electrodes to increase the energy density of lithium-ion batteries; and they can better inhibit the partial deformation caused by the expansion and contraction of the active material during electrochemical cycling to increase battery durability.

[0062] In one possible embodiment, the thickness c of the first current collector 21 is designed to satisfy the following condition: 1 µm≤c≤15 µm. For example, the thickness c of the first current collector 21 can be 1 µm, 10 µm, or 15 µm.

[0063] In one possible embodiment, the thickness c of the first current collector 21 is designed to satisfy the following condition: 3 µm≤c≤7 µm. For example, the thickness c of the first current collector 21 can be 3 µm, 6.6 µm, 4 µm, 4.7 µm, 5 µm, 5.5 µm, 6 µm, 6.3 µm, or 7 µm.

[0064] It is easy to understand that an excessively small thickness c of the first current collector 21 would impair the tensile strength of the first current collector 21 and thus the strain-resistance of the first coating 22. Conversely, an excessively large thickness c of the first current collector 21 would impair the energy density of the battery. Therefore, by designing the thickness c of the first current collector 21 to satisfy the following condition: 3 µm≤c≤7 µm, the present application makes it possible to achieve a certain strain-resistance effect of the first coating 22 and ensure the energy density of the battery.

[0065] The first current collector 21 is a copper foil, and the expandability of the first current collector 21 can then be analyzed in conjunction with the actual thickness of the first current collector 21, and the expandability of the first current collector 21 mentioned here is mainly aimed at standards of lithium battery factories in the aftermath.

[0066] For example, when the thickness c of the copper foil is 6 µm, the normal extensibility of the first current collector 21 is >4% and the high extensibility of the first current collector 21 is >6%; and when the thickness c of the copper foil is 8 µm, the normal extensibility of the first current collector 21 is >5% and the high extensibility of the first current collector 21 is >8%.

[0067] In one possible embodiment, the thickness of the first current collector 21 is 1 µm to 15 µm.

[0068] In one possible embodiment, the silicon-based material in the first coating 22 comprises at least one silicon oxide material, wherein the general chemical formula of the silicon oxide material M y SiO x where 0≤y≤4, 0≤x≤4, and M comprises at least one of the following elements: Li, Mg, Ti and Al.

[0069] That is, the silicon oxide material comprises magnesium silicon oxide compounds, wherein the magnesium silicon oxide compounds comprise MgSiO3 or the magnesium silicon oxide compounds comprise MgSiO3 and Mg2SiO4.

[0070] For the first coating22, the higher the content of silicon oxide material, the more advantageous it is to increase the capacity of the battery.

[0071] In one possible embodiment, the punching depth H of the film sleeve 10 during the punching forming process is 2 mm to 5.5 mm.

[0072] In one possible embodiment, the punching depth of the film sleeve 10 during the punching forming process can be 2, 2.8, 3, 3.4, 4, 4.2 or 5.

[0073] The present application provides a battery cell further comprising a positive electrode, wherein the positive electrode and the negative electrode 20 are arranged in layers and separated from each other by a separator.

[0074] The positive electrode comprises a second current collector and a second coating disposed on the surface of the second current collector, wherein the second coating comprises one or more of the following materials: lithium cobalt oxide, a ternary material, lithium iron phosphate, lithium manganese oxide, and lithium titanate.

[0075] The present application further provides a battery comprising a housing and the above-mentioned battery cell, wherein the battery cell is arranged in the housing.

[0076] In the battery according to the present application, the number of battery cells may be 1, 2, 3, or more. No specific limitation is imposed here.

[0077] To verify that improvements in the present application not only effectively reduce the risk of corner cracks at the corner section 11 to increase safety, but also increase the energy density of the battery cell, a verification experiment is conducted below. The test data for specific embodiments are listed below. Example 1

[0078] In this embodiment, the battery cell can be manufactured in the following manner.

[0079] Preparation of the negative electrode coating slurry: Artificial graphite and silicon carbon as the negative electrode active material, electrically conductive carbon black as the conductive agent, styrene-butadiene rubber as the binder, and sodium carboxymethylcellulose as the thickener are added to a stirred tank in a mass ratio of 96.9:1.5:1.3:13. Deionized water is then added as the solvent and thoroughly stirred according to the existing preparation process. The mixture is then filtered through a 150-mesh sieve to produce the negative electrode coating slurry, with a solid content of 40% to 45%.

[0080] Manufacturing of the negative electrode 20: Using an applicator, the above-mentioned negative electrode coating slurry is applied to the surface of the first current collector 21 to form the first coating 22. The first current collector 21 is a copper foil and is then dried at 100°C to obtain the original negative electrode. Subsequently, the original electrode is cut according to actual requirements to obtain the negative electrode. The total weight S2 of the weight S1 of the silicon-based material and the first coating 22 is 17.749 g, and the weight S1 of the silicon-based material is 1.7749 g.

[0081] Preparation of the positive electrode coating slurry: Lithium cobalt oxide is used as the positive electrode active material. It is added to a stirred tank along with conductive agents and polyvinylidene fluoride in a mass ratio of 97.2:1.5:1.3. NMP (N-methylpyrrolidone) is then added as a solvent and thoroughly stirred according to the existing preparation process. The mixture is then filtered through a 200-mesh sieve to produce the positive electrode coating slurry. The solid content of the positive electrode coating slurry is 70% to 75%.

[0082] Positive electrode preparation: Using the applicator, the above-mentioned positive electrode coating slurry is applied to the surface of the second current collector to form the second coating. The second current collector is an aluminum foil collector and is then dried at 120°C to obtain the original positive electrode. The original electrode is then cut to size according to actual requirements to obtain the positive electrode.

[0083] Battery cell assembly: The above-mentioned positive electrode, negative electrode, and separator are wound together to form a winding core. The winding core is then wrapped with an aluminum-plastic film, with the punching depth H of the aluminum-plastic film being 4.0 mm to 4.5 mm during the punching and forming process. After removing moisture by drying, electrolyte solution is poured into the winding core, and a thermal press forming process is performed to form the battery cell.

[0084] In the embodiment 1, the first current collector 21 is a copper foil, the Oi value a of the graphite in the first coating 22 is 15, the tensile strength b of the first current collector 21 is 300 MPa, and the thickness c of the first current collector 21 is 4 µm. Furthermore, Wa is 1, Wb is 3, and Wc is 6. By calculation, it is found that (a×b×c) / (Wa×Wb×Wc) = 1000 and a 2 ×b×c / 10000 = 27.

[0085] The battery cell is tested 1,000 times in a charge and discharge cycle at an ambient temperature of 45°C, according to the charge and discharge method specified in the battery specification. The battery cell is charged and discharged 1,000 times. The damage level of the battery cell is then statistically evaluated. Example 2

[0086] The difference between this Embodiment 2 and Embodiment 1 is that Wa is 2 and Wb is 1, and the rest is the same as in Embodiment 1.

[0087] By calculation it turns out that (a×b×c) / (Wa×Wb×Wc) = 1500 and a 2 ×b×c / 10000 = 27. Example 3

[0088] The difference between this embodiment 3 and embodiment 1 is that Wa is 2 and Wc is 3 and the rest is the same as in embodiment 1. By calculation, it is found that (a×b×c) / (Wa×Wb×Wc)=1000 and a2×b×c / 10000=27. Example 4

[0089] The difference between this embodiment 4 and embodiment 1 is that the Ol value a of the graphite in the first coating 22 is 28, Wa is 2, and the rest is the same as in embodiment 1. By calculation, it is found that (a×b×c) / (Wa×Wb×Wc)=933.33 and a2×b×c / 10000=94.08. Example 5

[0090] The difference between this Embodiment 5 and Embodiment 1 is that the tensile strength b of the first current collector 21 is 450 MPa, Wa is 2, and the rest is the same as in Embodiment 1. By calculation, it is found that (a×b×c) / (Wa×Wb×Wc)=750 and a2×b×c / 10000=40.50. Example 6

[0091] The difference between this embodiment 6 and embodiment 1 is that the thickness c of the first current collector 21 is 7 µm, Wa is 2, and the rest is the same as in embodiment 1. By calculation, it is found that (a×b×c) / (Wa×Wb×Wc) = 875 and a 2 ×b×c / 10000 = 47.25. Example 7

[0092] The difference between this Embodiment 7 and Embodiment 1 is that the Ol value a of the graphite in the first coating 22 is 30, the tensile strength b of the first current collector 21 is 700 MPa, the thickness c of the first current collector 21 is 6 µm, Wa is 1, Wb is 1, and Wc is 1.5, and the rest is the same as in Embodiment 1. By calculation, it is found that (a×b×c) / (Wa×Wb×Wc) = 84000 and a 2 ×b×c / 10000 = 378. Comparison example 1

[0093] Comparative Example 1 differs from Embodiment 1 in that the Ol value a of the graphite in the first coating 22 is 15, the tensile strength b of the first current collector 21 is 300 MPa, the thickness c of the first current collector 21 is 4 µm, Wa is 2, Wb is 3, and Wc is 6. By calculation, it is found that (a×b×c) / (Wa×Wb×Wc) = 500 and a 2 ×b×c / 10000 = 27.

[0094] In Comparative Example 1, the degree of elongation of the negative electrode 20 is large, which may cause compression of the foil shell 10, so that the problem of breakage in the corner portion 11 may easily occur. Test procedures

[0095] Test method for graphite Ol value a: The Ol value of the negative electrode active material powder and the Ol value of the graphite in the first coating layer 22 (i.e., the Ol value of the negative electrode film layer) can be determined using an X-ray powder diffractometer (X'pertPRO). Based on the general rule of X-ray diffraction analysis and the graphite lattice parameter measurement method (JIS K0131 - 1996, JB / T4220 - 2011), the X-ray diffraction pattern is obtained, and then the Ol value = I(004) / I(110), where I(004) is the peak area of ​​the 004 characteristic diffraction peak and I(110) is the peak area of ​​the 110 characteristic diffraction peak.

[0096] Specifically, the test method for the powder OI value of the negative electrode active material: A certain mass of powder of the negative electrode active material is placed in the X-ray powder diffractometer. Through X-ray diffraction analysis, the peak areas of the diffraction peak of the 004 crystal surface and the diffraction peak of the 110 crystal surface are obtained, and then the powder OI value of the negative electrode active material particles are determined. Specifically, the test method for the OI value of the graphite in the first coating layer 22 (i.e., the OI value of the negative electrode film layer): The fabricated negative electrode is directly placed in the X-ray powder diffractometer. Through X-ray diffraction analysis, the peak areas of the diffraction peak of the 004 crystal surface and the diffraction peak of the 110 crystal surface are obtained, and then the OI value of the negative electrode film layer is determined.

[0097] Test method for the tensile strength of copper foil: A tensile tester with a measuring range of 0 N to 1000 N and an error of ±1%, as well as a dial caliper with a measuring range of 0 mm to 300 mm and a minimum pitch of 0.02 mm, or measuring instruments with equivalent accuracy are used. Samples to be tested are cut from the object to be tested, measuring 200 ± 0.5 mm long and 15 ± 0.25 mm wide. Sampling is carried out in the width direction of the object to be tested, with two samples each being taken in the longitudinal and transverse directions. The samples to be tested are then placed in the tensile tester, with the clamping distance of the collets being 125 ± 0.1 mm, the tensile speed of the collets being 50 mm / min, and the test temperature being 20 ± 10 °C. The specimens to be tested are continuously loaded in the longitudinal direction until they break.The maximum load F is read from the force plate or the tensile curve, and the absolute tensile strength is calculated: σ = F / L, where L is the width of the specimen under test. The arithmetic mean of the test results from 3-5 specimens is taken to obtain the absolute tensile strength of the specimen under test.

[0098] Test method for the thickness c of the first current collector 21: A digital tenth micrometer with a resolution of 0.1 µm or a high-precision micrometer is used. First, the first current collector 21 is removed from the battery cell, and it is ensured that no coating remains on its surface. Then, the measuring device is calibrated, and 3-5 points on the surface of the current collector are selected. The measuring head is lightly touched with a standard pressure, and the measurement result is recorded. The arithmetic mean of the measurement results of the 3-5 points is used as the thickness c.

[0099] Inspection method for the inverse parameter Ka of the first edge corner section 12: A 3D profilometer (e.g., white light interferometer or laser scanner) is used to perform 3D imaging of the corner section 11 and obtain the 3D topography of the corner section 11. Then, the vertex of the corner section 11 and the circular arc intersection point of the first edge corner section 12 (i.e., the upper or lower R corner) are marked in the software. Using geometric analysis tools, the linear distance between the vertex of the corner section 11 and the circular arc intersection point of the first edge corner section 12 is measured. The measurement is repeated three times, and the arithmetic mean of the three measurement results is used as the inverse parameter Ka.

[0100] Inspection method for the inverse parameter Kb of the second edge corner section 13: A 3D profilometer (e.g., white light interferometer or laser scanner) is used to perform 3D imaging of the corner section 11 and obtain the 3D topography of the corner section 11. Then, the vertex of the corner section 11 and the circular arc intersection point of the second edge corner section 13 (i.e., the 4R corner) are marked in the software. Using geometric analysis tools, the linear distance between the vertex of the corner section 11 and the circular arc intersection point of the second edge corner section 13 is measured. The measurement is repeated three times, and the arithmetic mean of the three measurement results is used as the inverse parameter Kb.

[0101] Inspection method for the inverse parameter Kc of the third edge corner section 14: A 3D profilometer (e.g., white light interferometer or laser scanner) is used to perform 3D imaging of the corner section 11 and obtain the 3D topography of the corner section 11. Then, the vertex of the corner section 11 and the circular arc intersection point of the third edge corner section 14 (i.e., the lateral R corner) are marked in the software. Using geometric analysis tools, the linear distance between the vertex of the corner section 11 and the circular arc intersection point of the third edge corner section 14 is measured. The measurement is repeated three times, and the arithmetic mean of the three measurement results is used as the inverse parameter Kc.

[0102] Test method for the punching depth H of the film sleeve 10: A high-precision laser thickness gauge or a tactile sample profilometer is used. After the gauge is calibrated, 3-5 measurement points are selected along the centerline of the punching cavity (e.g., the center point and symmetrical points on both sides). The perpendicular distance between the bottom surface of the cavity and the original, non-punched surface is scanned vertically using a non-contact laser or a micro-probe head (pressure ≤ 0.1 N). The arithmetic mean of the measurement results of the 3-5 points is used as the punching depth H. This yields the ratio of Ka to H (dh, Wa), the ratio of Kb to H (dh, Wb), and the ratio of Kc to H (dh, Wc).

[0103] Five battery cells from Working Example 1 to Working Example 7, as well as five battery cells from Comparative Example 1 and Comparative Example 2, were taken. At an ambient temperature of 45°C, the battery cells were tested 1,000 times in charge and discharge cycles, according to the charge and discharge method in the battery specification, i.e., the battery cells were charged and discharged 1,000 times. The damage status of the battery cells was then statistically evaluated. The experimental results are shown in Table 1. Table 1 Example Ol value of graphite a Tensile strength of copper foil b (MPa) Thickness of copper foil (µm) What Wb WC (a×b×c) / (Wa×Wb×Wc) a 2 ×b×c / 1000 Damage level after 1000 shock loads Comparison example 1 15 300 4 2 3 6 500 27 3 / 5 Example 1 15 300 4 1 3 6 1000 27 0 / 5 Example 2 15 300 4 2 1 6 1500 27 0 / 5 Example 3 15 300 4 2 3 3 1000 27 0 / 5 Example 4 28 300 4 2 3 6 933.33 94.08 0 / 5 Example 5 15 450 4 2 3 6 750 40.5 0 / 5 Example 6 15 300 7 2 3 6 875 47.25 0 / 5 Example 7 30 700 6 1 1 1.5 84000 378 0 / 5

[0104] A comparison between Embodiment 1 and Comparative Example 1 shows that reducing the value of Wa can increase the space of the corner regions to provide room for elongation and thus effectively prevent breakage.

[0105] A comparison between Embodiment 2 and Comparative Example 1 shows that reducing the value of Wb can increase the space of the corner regions to provide room for elongation and thus effectively prevent breakage.

[0106] A comparison between Embodiment 3 and Comparative Example 1 shows that reducing the value of Wc can increase the space of the corner regions to provide room for elongation and thus effectively prevent breakage.

[0107] A comparison between Working Example 4 and Comparative Example 1 shows that increasing the OI value of graphite can effectively prevent fracture and thus effectively control elongation.

[0108] A comparison between Embodiment 5 and Comparative Example 1 shows that increasing the tensile strength of the copper foil can effectively prevent breakage and thus effectively control elongation.

[0109] A comparison between Embodiment 6 and Comparative Example 1 shows that increasing the thickness of the copper foil can effectively control the elongation.

[0110] It should be noted that the numerical values ​​and numerical ranges mentioned in this application are approximate. Due to the effects of the manufacturing process, some margin of error may occur, and this margin of error may be considered negligible by those skilled in the art.

[0111] In describing this application, it should be understood that the terms used, such as "center," "length," "width," "thickness," "top," "bottom," "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "inner," "outer," "axial," "circumferential, etc., refer to directions or positions that are related to the directions or positions shown in the drawings. They are used solely to describe this application and simplify the description and are not intended to suggest or imply that the designated position or element must have a particular direction or be constructed in a particular design and operation. Therefore, this should not be construed as a limitation of this application.

[0112] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying the relative importance or the number of technical features referred to. Consequently, a feature referred to as "first" or "second" may explicitly or implicitly encompass one or more such features. In the description of this application, "several" means at least two, e.g., two, three, etc., unless explicitly and specifically limited otherwise.

[0113] In this application, unless otherwise expressly stated and defined, the terms "installation," "connecting," "attaching," "fixing," and similar terms should be understood in their broadest sense, e.g., they may be a fixed connection, a detachable connection, or a unitary connection; they may be a mechanical connection, an electrical connection, or a communication connection; they may be directly connected or indirectly connected via an intermediate medium; they may be an internal connection between two components, or an interaction relationship between two components. It is possible for a person skilled in the art to understand the specific meaning of these terms in this application based on the specific circumstances.

[0114] In the present application, unless otherwise expressly stated and defined, stating that a first feature is "above" or "below" a second feature can include both the first and second features touching directly and the first and second features touching not directly but via another feature between them. Furthermore, stating that a first feature is "above", "on top", or "on" a second feature means either that the first feature is directly or diagonally above the second feature, or simply that the horizontal height of the first feature is higher than that of the second feature. stating that a first feature is "below", "below", or "below" a second feature includes either that the first feature is directly or diagonally below the second feature, or simply that the horizontal height of the first feature is lower than that of the second feature.

[0115] Finally, it should be noted that the above embodiments merely serve to illustrate the technical solution of the present application and are not to be understood as limiting. Despite the detailed description of the present application based on the above embodiments, those skilled in the art should understand that they may further modify the technical solution described in the above embodiments or replace some or all of the technical features with equivalent features. These modifications or replacements do not cause the nature of the corresponding technical solution to deviate from the scope of the technical solution of the present application. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] JIS K0131 - 1996, JB / T4220 - 2011

[0095]

Claims

[1] Battery cell, characterized by that it comprises: a battery cell body and a foil envelope (10), wherein the foil envelope (10) is wrapped on the outside of the battery cell body, wherein the battery cell body comprises a negative electrode (20) comprising (20) a first current collector (21) and a first coating (22) comprising (22) graphite, wherein the foil envelope (10) has a plurality of corner sections (11) comprising (11) a first edge corner section (12), a second edge corner section (13) and a third edge corner section (14) that intersect each other; wherein the foil envelope (10) and the battery cell body satisfy the following condition: 750≤(a×b×c) / (Wa×Wb×Wc)≤90000; where Wa=Ka / H; Wb=Kb / H; Wc=Kc / H, where Ka is the inverse parameter of the first edge corner portion (12); Kb is the inverse parameter of the second edge corner portion (13); Kc is the inverse parameter of the third edge corner portion (14); H is the punching depth of the foil sleeve (10); a is the orientation index O1 value of the graphite in the first coating (22); b is the tensile strength of the first current collector (21); c is the thickness of the first current collector (21). [2] Battery cell according to claim 1, characterized by that the Ol value a of the graphite in the first coating (22), the tensile strength b of the first current collector (21) and the thickness c of the first current collector (21) satisfy the following condition: 20≤a2×b×c / 10000. [3] Battery cell according to claim 1 or 2, characterized bythat the film sleeve (10) comprises a top wall (17) and a plurality of side walls which are connected to the edge of the top wall (17), wherein the plurality of side walls comprise adjacent first side walls (15) and second side walls (16), wherein the connection point between the top wall (17) and the first side wall (15) forms the first edge corner section (12), the connection point between the top wall (17) and the second side wall (16) forms the second edge corner section (13), and the connection point between the first side wall (15) and the second side wall (16) forms the third edge corner section (14);wherein the ratio of the inversion parameter of the first edge corner portion (12) to the punching depth of the film sleeve (10) Wa, the ratio of the inversion parameter of the second edge corner portion (13) to the punching depth of the film sleeve (10) Wb and the ratio of the inversion parameter of the third edge corner portion (14) to the punching depth of the film sleeve (10) Wc satisfy the following conditions:; Wa≤Wc, Wb≤Wc, 1≤Wa≤8, 1≤Wb≤8, 1≤Wc≤8. [4] Battery cell according to any one of claims 1 to 3, characterized by that the first coating (22) further comprises a silicon-based material, wherein the ratio of the weight S1 of the silicon-based material to the total weight S2 of the first coating (22) satisfies the following condition: 0≤S1 / S2≤20%. [5] Battery cell according to any one of claims 1 to 4, characterized by that the Ol value a of the graphite in the first coating (22) satisfies the following condition: 8≤a≤30. [6] Battery cell according to any one of claims 1 to 5, characterized by that the tensile strength b of the first current collector (21) satisfies the following condition: 300 MPa≤b≤700 MPa. [7] Battery cell according to any one of claims 1 to 6, characterized by that the thickness c of the first current collector (21) satisfies the following condition: 1µm≤c≤15µm. [8] Battery cell according to claim 7, characterized by that the thickness c of the first current collector (21) satisfies the following condition 3µm≤c≤7µm. [9] Battery cell according to any one of claims 1 to 8, characterized by that the first coating (22) further comprises a silicon-based material, wherein the silicon-based material comprises at least one silicon oxide material having the chemical general formula M y SiO x wherein 0≤y≤4, 0≤x≤4, and M comprises at least one of the following elements: Li, Mg, Ti and Al. [10] Battery cell according to any one of claims 1 to 9, characterized by that the punching depth H of the film sleeve (10) during the punching forming process is 2 mm to 5.5 mm. [11] Battery, characterized by : a housing and a battery cell according to any one of claims 1 to 10, wherein the battery cell is arranged in the housing.

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