Battery cell, secondary battery, and electrical apparatus

Abstract

Embodiments of the present application provide a battery cell, a secondary battery, and an electrical apparatus. The battery cell comprises a casing and a wound electrode assembly that is provided in the casing. The wound electrode assembly comprises a negative electrode sheet, a positive electrode sheet, and a separator. At a winding starting end of the wound electrode assembly, the negative electrode sheet is wound to form a central hole. The battery cell provided in the present application can achieve both high energy density and excellent cycle performance.

Description

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

[0001] This patent document claims priority to and the benefit of Chinese Patent Application No. 202411060916.6, filed August 5, 2024, entitled “Battery cell, secondary battery, and electric device.” The entire contents of the aforementioned patent application are incorporated by reference as part of the disclosure of this patent document. TECHNICAL FIELD

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

[0003] In recent years, secondary batteries mainly based on lithium ion batteries have been widely applied in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc., thereby achieving great development.

[0004] Improving the energy density of battery cells has always been the focus of research in the field of batteries. However, as the energy density of battery cells increases, the instantaneous heat released during thermal runaway also increases, and the safety performance requirements of battery cells also increase. Therefore, how to improve the safety performance of high-energy-density battery cells has become a technical problem to be solved. SUMMARY

[0005] The present application is made in view of the above technical problems, and aims to provide a battery cell, a secondary battery, and an electric device.

[0006] In a first aspect, a battery cell is provided, the battery cell comprising: a shell and a jelly-roll electrode assembly disposed in the shell, the jelly-roll electrode assembly comprising a negative electrode sheet, a positive electrode sheet, and a separator film; at a jelly-roll starting end of the jelly-roll electrode assembly, the negative electrode sheet is wound to form a central hole.

[0007] In an embodiment of the present application, the central hole of the jelly-roll electrode assembly is formed by winding the negative electrode sheet, in other words, the central hole is formed by winding the negative electrode sheet, compared to directly winding the electrode assembly to form the central hole, the negative electrode sheet can realize self-supporting of the central hole, preventing the electrode sheet at the central hole from expanding due to participating in the electrochemical reaction during the cycle process, and thus causing the central hole structure to collapse. Therefore, the scheme of the present application can improve the cycle performance of the battery cell without reducing the energy density of the battery cell.

[0008] In an implementation, the positive electrode tab includes a positive electrode active material including a lithium-containing transition metal oxide, the negative electrode tab includes a negative electrode active material including a silicon-containing material; and at the winding start end of the wound electrode assembly, a difference L1-L2 between a length L1 of the negative electrode tab and a length L2 of the positive electrode tab satisfies: 30 mm≤L1-L2≤60 mm.

[0009] In the embodiments of the present application, the active material in the battery cell is a high-capacity active material, which can further improve the energy density of the battery cell. At the same time, by controlling the difference between the lengths of the negative electrode tab and the positive electrode tab, the length of the negative electrode tab or the positive electrode tab forming the central hole can be controlled, the structural strength at the central hole is indirectly regulated, the collapse of the central hole caused by the expansion of the active material is improved, and the cycle performance of the high-energy-density battery cell is improved.

[0010] In an implementation, a diameter d of the central hole satisfies: nπd≥L1-L2, where π is a circular constant, n is an integer and n≥2.

[0011] In the embodiments of the present application, by controlling the central hole diameter to satisfy the above relationship, the negative electrode tab can be wound at least two turns to form a central hole, so that the central hole structure has self-supporting property, and the collapse of the central hole caused by the expansion of the active material is improved.

[0012] In an implementation, in the lithium-containing transition metal oxide, the molar percentage n% of Ni element in the transition metal element satisfies: 80%≤n%<100%; and the silicon-containing material includes at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, silicon-containing alloy or silicon-oxygen-carbon composite material.

[0013] In an implementation, the battery cell includes an end cover, the end cover includes a pressure relief mechanism, the shell is provided with an opening, and the end cover covers the opening.

[0014] In an implementation, the volume particle size distribution of the lithium-containing transition metal oxide includes two peaks, the two particle sizes corresponding to the two peaks are D1 and D2 respectively, 2 μm≤D1≤4 μm; 10 μm≤D2≤13.5 μm; and a limiting portion is protruded on a side of the shell close to the end cover, the limiting portion is used to limit the movement of the end cover towards the wound electrode assembly.

[0015] In the embodiments of the present application, the positive electrode active material is selected as a lithium-containing transition metal oxide with a bimodal distribution of volume particle size, which helps to improve the compaction density of the positive electrode sheet, thereby further improving the energy density of the battery cell. At the same time, based on the further improved energy density, more heat is released when the battery cell is in thermal runaway. Through the setting of the limiting part on the shell, the movement of the end cover towards the direction close to the wound electrode assembly is prevented, thereby reducing the probability of the wound electrode assembly blocking the pressure relief mechanism on the end cover when in thermal runaway, and improving the safety performance of the high-energy-density battery cell.

[0016] In an implementable manner, the D1 and D2 satisfy: 8 μm≤D2-D1≤11.5 μm.

[0017] In an implementable manner, the half-peak width W1 of the peak corresponding to D1 satisfies: 1.4 μm≤W1≤2.0 μm; and the half-peak width W2 of the peak corresponding to D2 satisfies: 8 μm≤W2≤12 μm.

[0018] In an implementable manner, the positive electrode active material satisfies at least one of the following conditions: (1) the Dv10 of the positive electrode active material satisfies: 1 μm≤Dv10≤3 μm; (2) the Dv50 of the positive electrode active material satisfies: 9 μm≤Dv50≤11 μm; and (3) the Dv90 of the positive electrode active material satisfies: 14 μm≤Dv90≤18 μm.

[0019] In an implementable manner, the positive electrode active material further comprises a doping element, and the doping element comprises at least one of Zr, Sr, Al, Co, B, W, Nb, Sb, P, and F.

[0020] In an implementable manner, the compaction density p of the positive electrode sheet satisfies: 3.55 g / cc≤p≤3.67 g / cc; and in the thickness direction of the end cover, the distance H between the wound electrode assembly and the pressure relief mechanism satisfies: H≥5 mm.

[0021] In an implementable manner, 5 mm≤H≤8 mm.

[0022] In the embodiments of the present application, the powder compaction density of the positive electrode sheet is controlled within a larger range, and the energy density of the battery cell is further improved. At the same time, the distance between the wound electrode assembly and the pressure relief mechanism is controlled within a larger range, which can further reduce the probability of the wound electrode assembly blocking the pressure relief mechanism when in thermal runaway, thereby improving the safety performance of the battery cell without reducing the energy density of the battery cell, so that the high-energy-density battery cell has good cycle performance and safety performance.

[0023] In an implementable manner, the ratio of the mass of the battery cell electrolyte to the nominal capacity of the battery cell satisfies: and the separator film comprises a base film and a ceramic coating layer arranged on at least one side of the base film.

[0024] In the embodiments of the present application, since the center hole is obtained from the negative electrode blank roll, it has self-supporting capability, thus, the PVDF coating layer arranged on the separator film for relieving the expansion of the wound electrode assembly can be omitted, that is, the separator film can only comprise a base film and a ceramic coating layer arranged on the base film; at the same time, the amount of electrolyte can be reduced, and the heat generated by the decomposition of electrolyte during thermal runaway of the battery cell can be reduced, thereby further improving the safety performance of the high-energy-density battery cell.

[0025] In an implementable manner, the end cover comprises an end cover body, and the pressure relief mechanism is arranged on a side of the end cover body facing the wound electrode assembly.

[0026] In an implementable manner, the end cover body is provided with a score groove, and an area defined by the score groove forms the pressure relief mechanism.

[0027] In an implementable manner, the battery cell further comprises a current collecting member accommodated in the shell; in the thickness direction of the end cover, the current collecting member is located between the wound electrode assembly and the end cover and abuts against a side of the limiting portion facing the wound electrode assembly, and the current collecting member is electrically connected to the tab of the wound electrode assembly and the shell.

[0028] In an implementable manner, the limiting portion is in the form of a protrusion or a roller groove.

[0029] In an implementable manner, the capacity C of the battery cell satisfies 30 Ah≤C≤40 Ah.

[0030] In an implementable manner, the area S of the region defined by the pressure relief mechanism satisfies 500 mm 2 ≤S≤800 mm 2 .

[0031] In a second aspect, a secondary battery is provided, which comprises the battery cell of any of the implementable manners of the first aspect.

[0032] In a third aspect, a power consumption device is provided, which comprises the battery cell of any of the implementable manners of the first aspect and / or the secondary battery of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0033] 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 for those skilled in the art, other drawings can be obtained on the basis of the drawings without creative labor.

[0034] FIG. 1 is a schematic diagram of a battery cell.

[0035] FIG. 2 is a schematic diagram of a positive electrode sheet and a negative electrode sheet.

[0036] FIG. 3 is a schematic diagram of another battery cell.

[0037] FIG. 4 is an enlarged schematic diagram of the dashed line part in FIG. 3.

[0038] FIG. 5 is a schematic diagram of a battery.

[0039] FIG. 6 is a schematic diagram of a volume particle size distribution of a positive electrode active material. DETAILED DESCRIPTION

[0040] Hereinafter, specific embodiments of the lithium ion battery and the electric device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0041] "RANGES" disclosed herein are defined, for each range by endpoints, the endpoints defining the bounds of the particular range. The ranges can be inclusive or exclusive of the endpoints, and, unless otherwise specifically stated herein, are combinable in any manner. For instance, if ranges of 60-120 and 80-110 are stated as pertaining to a particular parameter, it is to be understood that a range of 60-110 and 80-120 are also contemplated. Also, if a minimum of ranges 1 and 2 are stated, and a maximum of ranges 3, 4 and 5 are stated, then all of the following ranges are contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise stated, a range of "a-b" is a shorthand manner of describing each and every number that is contained between the number "a" and the number "b", wherein "a" and "b" are real numbers. For example, the phrase "a range of 0-5" is a shorthand manner of stating that all real numbers that are present between the number "0" and the number "5" are contemplated herein, and the phrase "0-5" is merely a shorthand manner of describing the range of values that are present between the number "0" and the number "5". Also, when a parameter is stated to be an integer > 2, it is equivalent to state that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] In the description of the present application, it is necessary to explain that, unless otherwise stated, the meaning of "a plurality" is more than two; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like is merely for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0043] Unless otherwise specified, in the present application, the phrase "A and / or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A and / or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or A and B are both true (or present).

[0044] If not otherwise specified, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0045] If not otherwise specified, all embodiments of the present application and optional embodiments can be combined to form new technical solutions.

[0046] If not otherwise specified, the following terms have the following meanings. Any undefined terms have their meanings as commonly understood in the art.

[0047] If mentioned, “battery” refers to a physical module comprising one or more battery cells to provide electrical energy. For example, the battery mentioned in the present application can comprise a battery module or a battery pack, etc.

[0048] If mentioned, “central hole” refers to a hole-like structure at the center of a jelly-roll electrode assembly. The electrode assembly is wound around a central axis (also called a central pin), and a central hole is usually left at the center of the cylindrical electrode assembly after the central pin is pulled out.

[0049] If mentioned, “bimodal particle size distribution” refers to a situation where there are two distinct peaks in the particle size distribution curve of a material. This indicates that there are two major particle sizes in the particle size distribution of the material.

[0050] If mentioned, “nominal capacity” refers to the capacity that a battery cell can release under certain conditions, which are specified by the battery cell manufacturer, such as discharge rate, discharge time, etc. The nominal capacity is the capacity marked on the battery cell by the battery cell manufacturer, which can be listed in the battery cell model, specification table, or in the application object of the battery cell, such as the nameplate of the vehicle.

[0051] Next, the embodiments of the present application are introduced.

[0052] In recent years, secondary batteries have been widely used in electric tools, electronic products, electric vehicles, aerospace and other fields due to their high energy density and long service life, and have developed rapidly. Generally, the battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charging and discharging process of the battery cell, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. Among them, the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet to prevent short circuiting of the positive and negative electrodes while allowing active ions to pass through, so that the electrochemical reaction in the battery cell can proceed normally.

[0053] Generally, during the processing of the wound electrode assembly, the electrode assembly is wound around the center pin. When the center pin is pulled out after winding, a center hole is left at the center of the columnar electrode assembly. During the cycle of the battery cell, the electrode assembly expands to a certain extent, which may cause the center hole to collapse, which is not conducive to the safety performance of the battery cell. The collapse of the center hole structure will cause the battery cell to cycle to dive, which will seriously affect the cycle performance of the battery cell. In order to improve this situation, a center pin or other substances are usually arranged in the center hole to form support for the center hole to improve the problem of center hole collapse. However, the center pin or the filler will occupy the volume inside the battery cell and increase the weight of the battery cell, which is not conducive to the energy density of the battery cell. Especially for battery cells that pursue high energy density, the existing design cannot meet the safety and cycle requirements of high energy density batteries.

[0054] Therefore, the present application provides a battery cell, a secondary battery and an electric device. The battery cell forms a center hole of a wound electrode assembly by an empty negative electrode sheet. This center hole has self-supporting property, which can improve the problem of center hole collapse without reducing the energy density of the battery cell, so that the battery cell has high energy density and safety performance.

[0055] Next, the battery cell provided by the present application is introduced.

[0056] [Battery cell]

[0057] Firstly, a battery cell is provided, and FIG. 1 is a schematic structural diagram of a battery cell according to the present application. As shown in FIG. 1, the battery cell 10 includes a shell 11 and a wound electrode assembly 12 arranged in the shell. The wound electrode assembly 12 includes a negative electrode sheet, a positive electrode sheet and a separator. At the winding starting end of the wound electrode assembly 12, the negative electrode sheet is wound to form a center hole 13.

[0058] Specifically, the jelly-roll type electrode assembly 12 is made by winding the continuous long sheet type positive electrode sheet and negative electrode sheet apart from each other by the separator film, and then winding around a center pin or a winding shaft to form a jelly-roll type electrode assembly 12 having a winding structure. When the center pin or the winding shaft is pulled out after winding is completed, a center hole 13 is left at the center of the columnar jelly-roll type electrode assembly 12. The stability of the structure of the center hole 13 is crucial to the cycle performance of the battery cell 10. However, since the jelly-roll type electrode assembly 12 will swell during the cycle of the battery cell 10, the structure of the center hole 13 is prone to collapse, thus intensifying the polarization reaction at the center hole 13, and easily leading to lithium precipitation and thus cycle diving, which is not conducive to the cycle performance and safety performance of the battery cell 10.

[0059] In the embodiment, the center hole 13 is formed by winding the negative electrode sheet, in other words, the center hole 13 is obtained by winding the negative electrode sheet alone. The winding alone negative electrode sheet as referred to in the present application means the case of winding the negative electrode sheet only. Compared with the scheme of directly winding all the electrode assemblies (positive electrode sheet, negative electrode sheet and separator film) to form the center hole 13, the negative electrode sheet alone does not participate in the electrochemical reaction of lithium ion deintercalation during the cycle of the battery cell 10, and thus the electrode sheet itself at the center hole 13 does not swell seriously, thereby forming a relatively stable center hole 13 structure, which can resist the extrusion of the center hole 13 structure caused by the swelling of the electrode assembly. On the other hand, the negative active material of the negative electrode sheet is an active material for lithium ion intercalation, and the positive active material of the positive electrode sheet is an active material for providing lithium ions, which usually includes a large amount of lithium source and a certain amount of lithium supplement. Compared with the selection of the positive electrode sheet for winding to form the center hole 13, the selection of the negative electrode sheet for winding alone to form the center hole 13 can avoid the dissolution of the lithium source or lithium supplement in the positive electrode sheet and thus the lithium precipitation at the negative electrode. Thus, the embodiment can improve the problem of easy collapse of the center hole 13 by winding the negative electrode sheet alone, and improve the cycle performance of the battery cell 10.

[0060] It should be understood that the jelly-roll type electrode assembly 12 can be a columnar electrode assembly as shown in FIG. 1, or an elliptical columnar electrode assembly, which is not limited in the embodiments of the present application.

[0061] FIG. 2 is a schematic structural diagram of a positive electrode sheet and a negative electrode sheet according to an embodiment of the present application.

[0062] In one embodiment, as shown in FIG. 2, the positive electrode sheet 122 includes a positive active material including a lithium-containing transition metal oxide, and the negative electrode sheet 121 includes a negative active material including a silicon-containing material; and at the winding starting end of the jelly-roll type electrode assembly 12, the difference L1-L2 between the length L1 of the negative electrode sheet 121 and the length L2 of the positive electrode sheet 122 satisfies: 30 mm≤L1-L2≤60 mm.

[0063] The jelly-roll electrode assembly 12 includes a positive electrode tab 122, a negative electrode tab 121, and a separator (not shown in FIG. 2) disposed between the positive electrode tab 122 and the negative electrode tab 121. As shown in FIG. 2, the aforementioned components are wound along the x direction, i.e., the jelly-roll electrode assembly 12 is obtained. In order to enhance the mechanical strength of the central hole 13, the length L1 of the negative electrode tab 121 is longer than the length L2 of the positive electrode tab 122, so that the negative electrode tab 121 can be wound alone at the winding start during winding, forming the central hole 13.

[0064] It should be understood that the difference L1-L2 between the length L1 of the negative electrode tab 121 and the length L2 of the positive electrode tab 122 refers to the length by which the negative electrode tab 121 is longer than the positive electrode tab 122 at the winding start, and can also be understood as the length of the negative electrode tab 121 that is wound empty.

[0065] Specifically, L1-L2 can be 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm, 48 mm, 50 mm, 52 mm, 54 mm, 56 mm, 58 mm, 60 mm, or a value within the range obtained by any two of the aforementioned values.

[0066] In this embodiment, lithium transition metal oxide is selected as the positive electrode active material in the positive electrode tab 122 of the battery monomer 10, and silicon-containing material is selected as the negative electrode active material in the negative electrode tab 121. Both the lithium transition metal oxide-containing material and the silicon-containing material have high gram capacity, and the combination can obtain a battery monomer 10 with high energy density. Based on the combination of high-gram-capacity active materials, while controlling the value of L1-L2 to be within a suitable range, the larger L1-L2 is, the longer the length of the negative electrode tab 121 that is wound empty to form the central hole 13, and the better the structural stability of the central hole 13, which can provide good structural stability for the jelly-roll electrode assembly 12. At the same time, controlling L1-L2 to be no more than 60 mm reduces the waste of the negative electrode tab 121. Thus, by selecting high-gram-capacity active materials and controlling L1-L2 to be within a suitable range, the energy density of the battery monomer 10 can be improved while the structural stability of the jelly-roll electrode assembly 12 is improved, so that the battery monomer 10 has both high energy density and good cycle performance.

[0067] In one embodiment, the diameter d of the central hole 13 satisfies: nπd ≥ L1-L2, where π is the circular constant, and n is an integer and n ≥ 2.

[0068] Specifically, π d represents the circumference of the negative electrode tab 121 forming the innermost circle of the central hole 13. The length of the negative electrode tab 121 of the empty roll is usually not too long, so the diameters of several circumferences forming the central hole 13 can be approximately the same from the radial direction of the wound electrode assembly 12. (L1-L2) / π d can represent the number of winding turns of the negative electrode tab 121 wound into the central hole 13. n≥2 represents that the central hole 13 is obtained by at least winding two turns of the negative electrode tab 121.

[0069] In one embodiment, the molar percentage n% of Ni element in the transition metal element in the lithium-containing transition metal oxide satisfies: 80%≤n%<100%; the silicon-containing material includes at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, silicon-containing alloy, or silicon-oxygen-carbon composite material.

[0070] Specifically, a lithium-containing transition metal oxide with high nickel content can be used as the positive electrode active material, such as NCM, NCA, etc. Such high-nickel material has a relatively high gram capacity, which can be matched with a silicon-containing material with a similarly high gram capacity to improve the energy density of the battery monomer 10.

[0071] In one embodiment, the positive electrode active material further includes a doping element, and the doping element includes at least one of Zr, Sr, Al, Co, B, W, Nb, Sb, P, and F.

[0072] In this embodiment, by further introducing a doping element into the positive electrode active material, the gram capacity of the positive electrode active material is further improved, thereby further improving the energy density of the battery monomer 10.

[0073] Please continue to refer to FIG. 1. In one embodiment, the shell 11 is provided with an opening, and the battery monomer 10 includes an end cover 14, the end cover 14 includes a pressure relief mechanism 141, and the end cover 14 covers the opening.

[0074] Specifically, the end cover 14 is used to cover the opening of the shell 11 to isolate the internal environment of the battery monomer 10 from the external environment. The end cover 14 covers the opening of the shell 11, and the end cover 14 and the shell 11 together define a sealed space for accommodating the wound electrode assembly 12, the electrolyte, and other components.

[0075] The shape of the end cover 14 can be adapted to the shape of the shell 11. For example, the shell 11 is a cuboid structure, and the end cover 14 is a rectangular plate structure adapted to the shell 11. For another example, the shell 11 is a cylindrical structure as shown in FIG. 1, and the end cover 14 is a circular plate structure adapted to the shell 11. The material of the shell 11 of the embodiment of the present application can include one or more, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cover 14 can be various, and exemplarily, the end cover 14 can be a metal material, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cover 14 can be the same as or different from the material of the shell 11. As an example, the material of the end cover 14 is aluminum.

[0076] The pressure relief mechanism 141 is an element or component for being actuated to release the pressure or temperature inside the battery monomer 10 when the pressure or temperature inside the battery monomer 10 reaches a predetermined threshold. The predetermined threshold can be adjusted according to different design requirements. For example, the predetermined threshold depends on the material of one or more of the positive electrode sheet, the negative electrode sheet, the electrolyte, and the separator film in the battery monomer 10. “Actuated” means that the pressure relief mechanism 141 generates an action or is activated to a certain state, so that the pressure and temperature inside the battery monomer 10 are released. The action generated by the pressure relief mechanism 141 can include but is not limited to at least one of the following: rupture, fragmentation, tearing, or opening of the pressure relief mechanism 141, etc. When the pressure relief mechanism 141 is actuated, the high-temperature and high-pressure substances inside the battery monomer 10 as the discharge will be excluded outward from the actuated part. In this way, the battery monomer 10 can be relieved of pressure and temperature under controllable pressure or temperature, thereby reducing the risk of a more serious accident.

[0077] The discharge from the battery monomer 10 mentioned in the embodiment of the present application includes but is not limited to the electrolyte, the dissolved or split positive and negative electrode sheets, the fragments of the separator film, the high-temperature and high-pressure gas generated by the reaction, the flame, etc.

[0078] The pressure relief mechanism 141 can be in a separate structure from the end cap 14, and the pressure relief mechanism 141 is a separate component mounted on the end cap 14. For example, the pressure relief mechanism 141 can be a component such as a rupture disc, a gas valve, a pressure relief valve, or a safety valve mounted on the end cap 14, and can specifically adopt a pressure-sensitive or temperature-sensitive element or structure. The pressure relief mechanism 141 can also be in an integrated structure with the end cap 14. The pressure relief mechanism 141 is part of the end cap 14. For example, the pressure relief mechanism 141 can be formed by providing a notch on the end cap 14, and the thickness of the notch is significantly smaller than the thickness of other regions of the end cap 14. The notch is the weakest position of the pressure relief mechanism. When the gas generated by the battery cell 10 is too much to cause the internal pressure to rise and reach a threshold value, or the heat generated by the reaction inside the battery cell 10 causes the internal temperature of the battery cell 10 to rise and reach a threshold value, the pressure relief mechanism 141 can break at the notch to cause the inside and outside of the battery cell 10 to communicate, and the gas pressure and temperature are released outward through the cracking of the pressure relief mechanism 141, thereby avoiding explosion of the battery cell 10. As an example, the end cap 14 is provided with a notch groove, and the area defined by the notch groove forms the pressure relief mechanism 141. More specifically, the notch groove can be annular with a notch.

[0079] In the battery cell 10, there can be one or two end caps 14. If the shell 11 is a hollow structure with one open end, one end cap 14 is provided. If the shell 11 is a hollow structure with two open ends, two end caps 14 are provided, and the two end caps 14 cover the two open ends of the shell 11, respectively. In the embodiment of the battery cell 10 with two end caps 14, at least one of the two end caps 14 is provided with a pressure relief mechanism 141.

[0080] One of the positive and negative tabs of the wound electrode assembly 12 is electrically connected to one end cap 14, and the other is electrically connected to the shell 11. In the case of the shell 11 with one open end, the end of the shell 11 away from the end cap 14 can be provided with an electrode terminal, and the electrode terminal is insulatedly connected to the shell 11. One of the positive and negative tabs of the wound electrode assembly 12 is electrically connected to the shell 11, and the other is electrically connected to the electrode terminal.

[0081] FIG. 3 is a schematic structural diagram of another battery cell 10 of the present application. FIG. 4 is an enlarged schematic diagram of the dashed line area in FIG. 3. FIG. 6 is a schematic diagram of the volume particle size distribution of a positive active material.

[0082] Referring to FIGS. 3-4 and 6, in one embodiment, the volume particle size distribution of the lithium-containing transition metal oxide includes two peaks corresponding to two particle sizes D1 and D2, wherein 2 μm≤D1≤4 μm; 10 μm≤D2≤13.5 μm; and the side of the shell 11 close to the end cap 14 is provided with a limiting portion 111 for limiting the movement of the end cap 14 towards the wound electrode assembly 12.

[0083] Specifically, the limiting portion 111 is a structure for limiting the movement of the end cover 14 towards the winding electrode assembly 12, and is arranged on the inner side of the shell 11 and protrudes from the inner side. The inner side of the shell 11 refers to the inner side surface of the side wall of the shell 11 extending along the thickness direction of the end cover 14, and can be understood as extending substantially along the thickness direction of the end cover 14. In the embodiment where the shell 11 is a cylinder, the inner side of the shell 11 is a cylindrical surface. In the embodiment where the shell 11 is a cuboid, the inner side of the shell 11 is composed of four side surfaces located at different positions and connected end to end.

[0084] The limiting portion 111 and the shell 11 can be an integrally formed structure, or can be a structure connected together after being formed separately, such as being welded together. The limiting portion 111 can be various structures, such as a boss protruding from the inner side of the shell 11, or a ring structure extending along the circumference of the shell 11.

[0085] The number of limiting portions 111 on the shell 11 can be related to the number of pressure relief mechanisms 141 on the end cover 14. In the case where the battery monomer 10 includes one end cover 14 with a pressure relief mechanism 141 arranged thereon, one corresponding limiting portion 111 is arranged on the shell 11 near one end of the end cover 14. In the case where the battery monomer 10 includes two end covers 14 with pressure relief mechanisms 141 arranged thereon respectively, two corresponding limiting portions 111 are arranged on the shell 11 near the two ends of the two end covers 14 respectively.

[0086] The number of limiting portions 111 on the shell 11 can also be related to the volumetric energy density of the battery monomer 10. For example, when the volumetric energy density of the battery monomer 10 is large, multiple limiting portions 111 can be arranged near one end of the end cover 14. When some of the limiting portions 111 deform and fail, the other limiting portions 111 can maintain a certain distance between the winding electrode assembly 12 and the end cover 14, limiting the end cover 14 from directly contacting the pressure relief mechanism 141 on the winding electrode assembly 12, thereby blocking the pressure relief mechanism 141.

[0087] The volume particle size distribution of the lithium-containing transition metal oxide includes two peaks, i.e., the lithium-containing transition metal oxide has a volume particle size bimodal distribution. D1 can be 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4.0 μm, or a value within a range obtained by combining any two of the above values. D2 can be 10 μm, 10.2 μm, 10.4 μm, 10.6 μm, 10.8 μm, 11 μm, 11.2 μm, 11.4 μm, 11.6 μm, 11.8 μm, 12 μm, 12.2 μm, 12.4 μm, 12.6 μm, 12.8 μm, 13 μm, 13.2 μm, 13.4 μm, 13.5 μm, or a value within a range obtained by combining any two of the above values.

[0088] It should be understood that FIG. 6 is a schematic diagram of the volume particle size distribution of the positive electrode active material. In the positive electrode active material shown in FIG. 6, D1 = 3 μm, D2 = 13 μm, D2-D1 = 10 μm, W1 = 1.67 μm, and W2 = 11.06 μm. The particles with a volume particle size of D1 are usually single-crystal small particles, and the particles with a volume particle size of D2 are usually polycrystal large particles. The lithium-containing transition metal oxide material having a volume particle size bimodal distribution itself can achieve a higher compaction density, which helps to further improve the energy density of the battery monomer 10.

[0089] Thus, in this embodiment, by selecting the lithium-containing transition metal oxide having a volume particle size bimodal distribution, the energy density of the battery monomer 10 is further improved. The energy density of the battery monomer 10 is further improved, and the heat released during thermal runaway is larger, and the risk of thermal runaway is greater. For the high-energy-density battery monomer 10, the embodiment is configured with the limiting portion 111 of the shell 11, which can reduce the probability that the wound electrode assembly 12 blocks the pressure relief mechanism 141 on the end cover 14 during thermal runaway of the battery monomer 10, thereby improving the cycle performance and safety performance of the high-energy-density battery monomer 10.

[0090] In one embodiment, D1 and D2 satisfy: 8 μm ≤ D2-D1 ≤ 11.5 μm.

[0091] Specifically, D2-D1 represents the difference between the abscissa (particle size) corresponding to the two peaks in the volume particle size bimodal distribution. D2-D1 can be 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, or a value within a range obtained by combining any two of the above values.

[0092] In one embodiment, the half-peak width W1 of the peak corresponding to D1 satisfies: 1.4 pm ≤ W1 ≤ 2.0 pm; the half-peak width W2 of the peak corresponding to D2 satisfies: 8 pm ≤ W2 ≤ 12 pm.

[0093] Specifically, the half-peak width refers to the width of a peak at half of the height of the peak in a spectrum. A straight line parallel to the bottom of the peak is drawn through the midpoint of the height of the peak, and the distance between the two points of intersection on both sides of the peak is the half-peak width. W1 is the half-peak width of the peak corresponding to the smaller particle size value of the two distinct peaks in the volume particle size bimodal distribution, and W2 is the half-peak width of the peak corresponding to the other distinct peak in the volume particle size bimodal distribution. W1 can be 1.4 pm, 1.5 pm, 1.6 pm, 1.7 pm, 1.8 pm, 1.9 pm, 2.0 pm, or a value within the range obtained by any two of the above-mentioned values. W2 can be 8 pm, 8.5 pm, 9 pm, 9.5 pm, 10 pm, 10.5 pm, 11 pm, 11.5 pm, 12 pm, or a value within the range obtained by any two of the above-mentioned values.

[0094] In one embodiment, the positive electrode active material satisfies at least one of the following conditions: (1) the Dv10 of the positive electrode active material satisfies: 1 pm ≤ Dv10 ≤ 3 pm; (2) the Dv50 of the positive electrode active material satisfies: 9 pm ≤ Dv50 ≤ 11 pm; (3) the Dv90 of the positive electrode active material satisfies: 14 pm ≤ Dv90 ≤ 18 pm.

[0095] Specifically, Dv10 can be 1 pm, 1.5 pm, 2 pm, 2.5 pm, 3 pm, or a value within the range obtained by any two of the above-mentioned values. Dv50 can be 9 pm, 9.5 pm, 10 pm, 10.5 pm, 11 pm, or a value within the range obtained by any two of the above-mentioned values. Dv90 can be 14 pm, 14.5 pm, 15 pm, 15.5 pm, 16 pm, 16.5 pm, 17 pm, 17.5 pm, 18 pm, or a value within the range obtained by any two of the above-mentioned values. For example, in the positive electrode active material shown in FIG. 6, Dv10 = 2.3 pm, Dv50 = 10.7 pm, and Dv90 = 17.4 pm.

[0096] In one embodiment, the positive electrode tab has a compacted density p that satisfies: 3.55 g / cc ≤ p ≤ 3.67 g / cc.

[0097] Specifically, p can be 3.55 g / cc, 3.56 g / cc, 3.57 g / cc, 3.58 g / cc, 3.59 g / cc, 3.6 g / cc, 3.61 g / cc, 3.62 g / cc, 3.63 g / cc, 3.64 g / cc, 3.65 g / cc, 3.66 g / cc, 3.67 g / cc, or a value within a range derived from any two of the above-mentioned values. Due to the bimodal distribution of the volume particle size of the positive active material, the pores between the particles with larger particle size can be filled by the particles with smaller particle size, thereby achieving high tap density. It should be understood that the tap density referred to in the present application is the tap density of the electrode sheet, which will change after the battery is formed or cycled, resulting in some error. The error range of the tap density of the positive electrode sheet 122 of the present application is less than or equal to ±0.1 g / cc.

[0098] Please continue to refer to FIGS. 3-4, when the wound electrode assembly 12 is arranged in the shell 11 provided with the limiting portion 111, the wound electrode assembly 12 can directly abut against the limiting portion 111 or abut against the limiting portion 111 through other components, thereby the wound electrode assembly 12 has a certain distance H from the pressure relief mechanism 141 on the end cover 14.

[0099] In one embodiment, in the thickness direction of the end cover 14, the distance H between the wound electrode assembly 12 and the pressure relief mechanism 141 satisfies: 5 mm≤H; optionally, 5 mm≤H≤8 mm.

[0100] Specifically, H can be 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, or a value within a range derived from any two of the above-mentioned values.

[0101] In the present embodiment, by controlling H in a relatively large and appropriate range, the battery monomer 10 can have both high energy density and high safety performance. The possible principle is that by selecting high-gravimetric-capacity active material, the energy density of the battery monomer 10 is greatly improved. On this basis, although increasing H will lose part of the internal space of the battery monomer 10, by controlling H in an appropriate range, this part of the loss will not affect the overall energy density of the battery monomer 10. Thus, by controlling H in a relatively large but appropriate range, the battery monomer 10 can have both high energy density and good safety performance.

[0102] In one embodiment, the ratio of the mass of the electrolyte of the battery monomer 10 to the nominal capacity of the battery monomer 10 satisfies: and the separator film comprises a base film and a ceramic coating layer arranged on at least one side of the base film.

[0103] ​Specifically, the separator film usually includes a base film, a ceramic coating arranged on at least one side of the base film, and a PVDF coating. Among them, the PVDF coating can increase the gap between the pole pieces of the jelly-roll electrode assembly 12, providing a certain expansion space for the expansion of the jelly-roll electrode assembly 12 during the circulation of the battery monomer 10, but the PVDF coating usually needs more electrolyte to be soaked, otherwise it is not conducive to ion transmission and affects the electrochemical reaction inside the battery monomer 10. In the embodiment, the separator film including the base film and the ceramic coating arranged on at least one side of the base film can be selected, in other words, the separator film can not be provided with a PVDF coating. Therefore, while selecting the aforementioned separator film, the amount of electrolyte of the battery monomer 10 can be reduced, that is, the value of the electrolyte mass per unit capacity of the battery monomer 10 can be reduced. The value of the electrolyte mass per unit capacity of the battery monomer 10 can be 0.7 g / Ah, 0.8 g / Ah, 0.9 g / Ah, 1.0 g / Ah, 1.1 g / Ah, 1.2 g / Ah, 1.3 g / Ah, 1.4 g / Ah, or a value within the range obtained by any two of the above combinations. The value of the electrolyte mass per unit capacity of the battery monomer 10 can be 0.7 g / Ah, 0.8 g / Ah, 0.9 g / Ah, 1.0 g / Ah, 1.1 g / Ah, 1.2 g / Ah, 1.3 g / Ah, 1.4 g / Ah, or a value within the range obtained by any two of the above combinations. The value of the electrolyte mass per unit capacity of the battery monomer 10 can be 0.7 g / Ah, 0.8 g / Ah, 0.9 g / Ah, 1.0 g / Ah, 1.1 g / Ah, 1.2 g / Ah, 1.3 g / Ah, 1.4 g / Ah, or a value within the range obtained by any two of the above combinations.

[0104] It should be understood that the electrolyte mass of the battery monomer 10 of the same model is different in different states, and the value of the electrolyte mass per unit capacity of the battery monomer 10 is also different. For example, the value of the electrolyte mass per unit capacity of the battery monomer 10 before circulation satisfies: For another example, after circulation, the electrolyte is partially consumed, and the value of the electrolyte mass per unit capacity of the battery monomer 10 can satisfy: For another example, after circulation, the electrolyte is partially consumed, and the value of the electrolyte mass per unit capacity of the battery monomer 10 can satisfy:

[0105] Please continue to refer to FIGS. 3-4, in an embodiment, the battery monomer 10 further includes: a current collecting member 15, the current collecting member 15 is accommodated in the shell 11; in the thickness direction of the end cover 14, the current collecting member 15 is located between the jelly-roll electrode assembly 12 and the end cover 14, and the current collecting member 15 is electrically connected to the pole lug of the jelly-roll electrode assembly 12 and the end cover 14.

[0106] Specifically, the current collecting member 15 can be a disc-shaped member arranged between the end cover 14 and the jelly-roll electrode assembly 12, for example, the shell 11 is a cylinder, and the current collecting member 15 is a disc structure. The current collecting member 15 can be a metal conductor, such as copper, iron, aluminum, steel, aluminum alloy, etc.

[0107] ​​It should be understood that other structures for connection or electrical connection can also be included in the battery cell 10, which will not be described herein. The electrical connection referred to herein can be direct electrical connection (such as welding, abutting) or indirect electrical connection through other current-conducting components.

[0108] In one embodiment, the capacity C of the battery cell 10 satisfies: 30 Ah ≤ C ≤ 40 Ah.

[0109] Specifically, C can be 30 Ah, 32 Ah, 34 Ah, 36 Ah, 38 Ah, 40 Ah, or a value within the range obtained by any two of the above combinations. Through the material and structure combination in the foregoing embodiments, the battery cell 10 of the present embodiment can achieve a high capacity of 30-40 Ah.

[0110] In one embodiment, the area S of the region defined by the pressure relief mechanism 141 satisfies: 500 mm 2 ≤ S ≤ 800 mm 2 .

[0111] Specifically, the area of the region defined by the pressure relief mechanism 141 refers to the vertical projection area of the region defined by the pressure relief mechanism 141 on the plane of the end cover 14. For example, the region defined by the score groove forms the pressure relief mechanism 141, and the area of the region defined by the pressure relief mechanism 141 is the area of the region defined by the score groove. S can be 500 mm 2 , 550 mm 2 , 600 mm 2 , 650 mm 2 , 700 mm 2 , 750 mm 2 , 800 mm 2 , or a value within the range obtained by any two of the above combinations.

[0112] In the present embodiment, the larger the area of the pressure relief mechanism 141, the easier it is to break when the battery cell 10 experiences thermal runaway, which is conducive to the discharge of high-temperature and high-pressure substances inside the battery cell 10. The larger the area of the pressure relief mechanism 141, the greater the risk of the pressure relief mechanism 141 breaking under normal circumstances, and the greater the impact on the connection (such as welding) between the end cover 14 and the shell 11. Therefore, by controlling the area of the pressure relief mechanism 141 within an appropriate range, the risk of the pressure relief mechanism 141 breaking during normal use of the battery cell 10 can be reduced, and the pressure relief mechanism 141 can be broken in time when the battery cell 10 experiences thermal runaway, thereby balancing the long-term use reliability and the reliability during thermal runaway of the battery cell 10.

[0113] Next, taking a lithium-ion battery as a specific example, the positive electrode, negative electrode, separator, and electrolyte in the battery cell 10 will be described in detail. It should be understood that the lithium-ion battery is only an example, and the solution provided in this application can also be applied to other types of secondary batteries, such as sodium-ion batteries, magnesium-ion batteries, and lithium-sulfur batteries.

[0114] [Negative electrode plate]

[0115] The negative electrode 121 typically includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material.

[0116] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0117] In one embodiment, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0118] In one embodiment, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0119] In one embodiment, the negative electrode film layer further includes an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0120] In one embodiment, the negative electrode film layer further comprises a conductive agent. The conductive agent can be selected from at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0121] In one embodiment, the negative electrode film layer further comprises other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0122] In one embodiment, the negative electrode sheet 121 can be prepared by forming a negative electrode slurry from the components described above for preparing the negative electrode sheet. For example, the negative electrode active material, the conductive agent, the binder, and any other components are dispersed in a solvent (e.g., N-methyl pyrrolidone) to form a negative electrode slurry. The negative electrode slurry is then coated on a negative electrode current collector, and after processes such as drying, cold pressing, and the like, the negative electrode sheet 121 is obtained.

[0123] [Positive electrode sheet]

[0124] The positive electrode sheet 122 comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a positive electrode active material.

[0125] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0126] In one embodiment, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite 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 (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0127] It has been introduced above that the positive electrode active material of the present application is a high-nickel material.

[0128] In another embodiment, the positive active material can also employ positive active materials for batteries known in the art. As an example, the positive active material can also include at least one of lithium-containing phosphates of olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive active materials for batteries can also be used. Among them, examples of lithium transition metal oxides can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), and modified compounds thereof, etc. Examples of lithium-containing phosphates of olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon. The battery will be accompanied by Li deintercalation and consumption during charging and discharging. The molar content of Li in the positive active material is different when the battery is discharged to different states. In the present application, the molar content of Li in the list of positive active materials is the initial state of the material, i.e., the state before feeding. When the positive active material is applied to the battery system, the molar content of Li will change after charging and discharging cycles. In the present application, the molar content of O in the list of positive active materials is only the ideal state value. The molar content of O will change due to lattice oxygen release, and the actual molar content of O will fluctuate.

[0129] In one embodiment, Li 1+a [Ni x Coy 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, x+y+z+b=1.

[0130] 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, c can be 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any value within the above range. As one example, b is 0, the positive electrode active material includes LiNi 0.8 Co 0.1 Mn 0.1 O2. As another example, b>0, the positive electrode active material includes LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2.

[0131] The positive electrode active material of the above formula can be referred to as a high-nickel ternary material, which is matched with the silicon-containing negative electrode active material, and is beneficial to improve the energy density of the battery monomer 10. In addition, compared with ternary materials with low nickel content or materials such as lithium iron phosphate, the high-nickel ternary material has a higher gram capacity, so that under the same capacity, the use of the high-nickel ternary material is beneficial to reduce the total mass of the positive electrode active material, thereby further improving the energy density of the battery monomer 10.

[0132] In one embodiment, the positive electrode active material includes: 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.

[0133] In one embodiment, the positive electrode film layer further includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene-fluorotetrafluoroethylene-propylene terpolymer, a vinylidene-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0134] In one embodiment, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0135] In one embodiment, the positive electrode tab 122 can be prepared by forming the above-mentioned components for preparing the positive electrode tab into a positive electrode slurry, respectively. For example, the first positive electrode active material and / or the second positive electrode active material, the conductive agent, the binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated on a positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab 122 is obtained.

[0136] [Electrolyte]

[0137] The electrolyte functions to conduct ions between the positive electrode tab 122 and the negative electrode tab 121. The type of the electrolyte is not particularly limited in the present application, and can be selected as needed. For example, the electrolyte can be in a liquid state, a gel state, or a full solid state.

[0138] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0139] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium di-oxalate borate, lithium difluoro di-oxalate phosphate, and lithium tetrafluoro oxalate phosphate.

[0140] In some embodiments, the solvent can be selected from at least one 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0141] In some embodiments, the electrolyte can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, etc.

[0142] [Separator]

[0143] The type of the separator is not particularly limited in the present application, and for example, any known porous structure separator having good chemical stability and mechanical stability can be used.

[0144] In one embodiment, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited. When the separator is a multi-layer composite film, the separator of the present application can not contain a PVDF coating.

[0145] In one embodiment, the negative electrode tab 121, the positive electrode tab 122, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0146] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape.

[0147] [Battery]

[0148] The battery provided in an embodiment of the present application includes the battery cell in the above embodiment. The battery can be a single physical module including 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 connection through a busbar.

[0149] In some embodiments, the battery can be a battery pack, and the battery includes a box body and a battery cell or a battery module contained in the box body.

[0150] In some embodiments, the box body can be part of the chassis structure of a vehicle. For example, part of the box body can be at least part of the floor of the vehicle, or part of the box body can be at least part of the cross beam and the longitudinal beam of the vehicle.

[0151] In some embodiments, the battery can be located in an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0152] FIG. 5 is a schematic diagram of a battery according to an embodiment of the present application. As shown in FIG. 5, the battery 20 can include multiple battery cells 10 to meet different power requirements.

[0153] The battery 20 can also include a box 3, which has a hollow structure inside, and the plurality of battery cells 10 are accommodated in the box 3. For example, the plurality of battery cells 10 are placed in the box 3 in parallel, series or mixed combination with each other. The box 3 can include a first box part 31 and a second box part 32, which are overlapped 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 inside, for example, according to the shape of the combination of the plurality of battery cells 10, 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. 5, 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-shaped to cover the opening. Taking the second box part 32 as a hollow cuboid with an opening and the first box part 31 as a plate-shaped as an example, the first box part 31 is overlapped at the opening of the second box part 32 to form a box 3 with a closed cavity, which can be used to accommodate the plurality of battery cells 10.

[0154] In addition, the application also provides a power utilization device, which includes the secondary battery in the foregoing embodiments.

[0155] For another example, unlike that shown in FIG. 5, the first box part 31 and the second box part 32 can both be hollow cuboids, each having one face as an opening face, the openings of the first box part 31 and the second box part 32 are oppositely arranged, and the first box part 31 and the second box part 32 are overlapped to form a box 3 with a closed cavity, which can be used to accommodate the plurality of battery cells 10. The plurality of battery cells 10 are placed in the box 3 formed by the overlapping of the first box part 31 and the second box part 32 in parallel, series or mixed combination with each other.

[0156] In some embodiments, the battery 20 can also include other components. For example, the battery 20 can also include a busbar component, which can be used to realize the electrical connection between the plurality of battery cells 10, for example, in parallel, series or mixed combination. Specifically, the busbar component can realize the electrical connection between the battery cells 10 by connecting the electrode terminals of the battery cells 10; or the busbar component can also realize the electrical connection between the battery cells 10 by connecting other components of the battery cells 10. The busbar component can be fixed to the corresponding components of the battery cells 10 by welding, for example, can be fixed to the electrode terminals, the sealing structure or the shell, etc., and the embodiments of the application are not limited thereto.

[0157] The battery cells 10 can directly constitute the battery 20, or can first constitute a battery module, and then constitute the battery 20 by a plurality of battery modules.

[0158] [Power utilization device]

[0159] The embodiment of the present application provides a power utilization device, which comprises the battery described in the above embodiment.

[0160] The power utilization 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, for example, a game machine, 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, for example, an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc. The embodiment of the present application does not specially limit the power utilization device.

[0161] The present application provides a power utilization device, which is a vehicle.

[0162] 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 vehicle can be provided with a motor, a controller and a battery 20, and the controller is used to control the battery 20 to supply power to the motor. For example, the battery 20 can be arranged at the bottom, the front or the rear of the vehicle. The battery 20 can be used for power supply of the vehicle, for example, the battery 20 can be used as an operating power source of the vehicle, and is used for circuit systems of the vehicle, for example, for power demand of starting, navigation and operation of the vehicle. In another embodiment of the present application, the battery 20 can not only be used as an operating power source of the vehicle, but also be used as a driving power source of the vehicle, to replace or partially replace fuel or natural gas to provide driving power for the vehicle.

[0163] Hereinafter, the embodiment of the present application is described. The embodiment described below is exemplary and is only used for explaining the present application, and cannot be understood as a limitation of the present application. If a specific technology or condition is not mentioned in the embodiment, the technology or condition is performed according to the technology or condition described in the literature in the field or according to the product instruction. If the reagent or instrument is not mentioned by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0164] [Examples and Comparative Examples]

[0165] Example 1

[0166] (1) Preparation of the negative electrode sheet

[0167] The negative active material graphite, sodium carboxymethyl cellulose, butadiene rubber and acetylene black are mixed in a mass ratio of 96:1:1:2, deionized water is added, and the slurry is stirred uniformly in a blender, then the slurry is coated on a copper foil with a thickness of 8 microns, dried in an oven at 120°C, cold-pressed, and cut to obtain a negative electrode sheet.

[0168] (2) Preparation of the positive electrode sheet

[0169] (2-1) Preparation of the first positive electrode material

[0170] Nickel sulfate, cobalt sulfate and manganese sulfate are configured into a sulfate solution in a molar ratio of 0.90:0.06:0.04, the solution pH is adjusted to 10-11 by sodium hydroxide, a certain amount of ammonia water is added, and the reaction is carried out at 60°C for 10h to prepare a precursor Ni 0.90 Co 0.06 Mn 0.04 (OH)2. The precursor Ni 0.90 Co 0.06 Mn 0.04 (OH)2: LiOH·H2O is mixed in a molar ratio of 100:105, then reacted with the material at 800°C and pure oxygen for 15h, and the first positive electrode material with a Dv50 of 2.5μm is prepared after airflow crushing.

[0171] (2-2) Preparation of the second positive electrode material

[0172] Nickel sulfate, cobalt sulfate and manganese sulfate are configured into a sulfate solution in a molar ratio of 0.92:0.06:0.02, the solution pH is adjusted to 10-11 by sodium hydroxide, a certain amount of ammonia water is added, and the reaction is carried out at 60°C for 10h to prepare a precursor Ni 0.92 Co 0.06 Mn 0.02 (OH)2. The precursor Ni 0.92 Co 0.06 Mn 0.02 (OH)2: LiOH·H2O is mixed in a molar ratio of 100:105, then reacted with the material at 750°C and pure oxygen for 15h, and the second positive electrode material with a Dv50 of 11.2μm is prepared after mechanical crushing.

[0173] (2-3) Preparation of the positive electrode active material

[0174] The first positive electrode material and the second positive electrode material are mixed in a mass ratio of 8:2 to obtain a positive electrode active material.

[0175] (2-4) Preparation of the positive electrode sheet

[0176] The positive electrode active material, polyvinylidene fluoride and conductive carbon black were mixed in a mass ratio of 90:5:5, then N-methyl pyrrolidone (NMP) was added, stirred for 2 h, then it was stirred in a homogenizer at 1200 r / min until mixed uniformly, then uniformly coated on a 13 μm thick aluminum foil, after coating was completed, it was dried in a drying oven at 120°C, cold pressed, and cut to obtain a positive electrode sheet.

[0177] (3) Preparation of the battery cell

[0178] The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, and after winding, an electrode assembly was obtained. The electrode assembly was placed in a shell, electrolyte was injected, then packaged to obtain a battery cell. The electrolyte was an electrolyte with ethylene carbonate (EC) and diethyl carbonate (DEC) as the solvent (volume ratio 1:2), and a lithium salt concentration of 1M.

[0179] In the battery cell of Example 1, a negative electrode sheet empty roll was used to form a center hole 13, |L1-L2| = 40 mm, D1 = 2.5 μm, D2 = 11.2 μm, D1-D2 = 8.7 μm, ρ = 3.65 g / cc, H = 6 mm.

[0180] Examples 2-5

[0181] Compared with Example 1, the difference lies in the value of |L1-L2| which is different from Example 1.

[0182] Examples 6-7

[0183] Compared with Example 1, the difference lies in the values of D1, D1-D2 and ρ which are different from Example 1.

[0184] Examples 8-9

[0185] Compared with Example 1, the difference lies in the values of D2, D1-D2 and ρ which are different from Example 1.

[0186] Examples 10-13

[0187] Compared with Example 1, the difference lies in the values of D1, D2, D1-D2 and ρ which are all different from Example 1.

[0188] Examples 14-17

[0189] Compared with Example 1, the difference lies in the value of H which is different from Example 1.

[0190] Example 18

[0191] Comparative Example 1

[0192] Compared with Example 1, the center hole in Comparative Example 1 was obtained by winding the positive electrode sheet, the negative electrode sheet and the separator together.

[0193] Product and performance parameters of Examples 1-17 and Comparative Example 1.

[0194] Table 1: Product and performance parameters of Examples 1-17 and Comparative Example 1

[0195] In Table 1, “L1-L2” represents the difference between the length L1 of the negative electrode sheet and the length L2 of the positive electrode sheet at the winding start end of the wound electrode assembly 12; “D1” represents the particle size corresponding to the smaller main peak in the bimodal distribution of the volume particle size of the positive electrode active material; “D2” represents the particle size corresponding to the other main peak in the bimodal distribution of the volume particle size of the positive electrode active material; “D2-D1” represents the difference between the particle sizes corresponding to the two main peaks in the particle size distribution of the positive electrode active material; “p” represents the compacted density of the positive electrode sheet 122; “H” represents the distance between the wound electrode assembly 12 and the pressure relief mechanism 141; “VED” represents the volumetric energy density of the battery monomer 10; “cycle number” represents the cycle number of the battery monomer 10 to 80% SOH; “puncture test” represents the performance of the battery monomer 10 in the puncture test. For specific test methods and processes, please refer to the Test section below.

[0196] The above examples and comparative examples all obtained high energy density for the battery monomer 10 through the matching of positive and negative electrode active materials.

[0197] According to the comparative analysis of the examples and comparative examples, the cycle performance of the examples is better than that of the comparative examples. This proves that the center hole 13 structure formed by the negative electrode sheet empty winding can provide more excellent cycle performance for the battery monomer 10 than the center hole 13 structure obtained by winding the whole electrode assembly. The possible reason is that the single negative electrode sheet 121 does not participate in the electrochemical reaction of lithium ion deintercalation during the cycle of the battery monomer 10, so the electrode sheet itself at the center hole 13 does not swell seriously, thereby forming a relatively stable center hole 13 structure, which can resist the extrusion of the center hole 13 by the swelling of the electrode sheet at the outer circle, thereby improving the problem of easy collapse of the center hole 13 and improving the cycle performance of the high energy density battery monomer 10.

[0198] From the comparative analysis of Examples 1-5, it can be seen that in the range of 30-60 mm, the cycle performance of the battery monomer 10 gradually improves, indicating that as L1-L2 increases, the length of the negative electrode sheet 121 used to form the center hole 13 of the empty roll is longer, the structural stability of the center hole 13 is better, and the wound electrode assembly 12 can provide good structural stability, thereby helping to improve the cycle performance of the battery monomer 10. In Example 4, L1-L2 is too small, the structural stability of the center hole 13 is not enough, and the cycle performance of the battery monomer 10 is not as good as Examples 1-3. In Example 5, L1-L2 is too large, and the cycle performance of the battery monomer 10 has not improved significantly compared to Example 4, but has reduced the energy density of the battery monomer 10. Therefore, by controlling L1-L2 in the range of 30-60 mm, the battery monomer can have high energy density and good cycle performance.

[0199] Examples 6-9 show the case of matching positive active materials with different volume particle size bimodal distribution. It can be seen that the battery monomer 10 in Examples 6-9 can have high energy density and good cycle performance and safety performance.

[0200] From the comparative analysis of Examples 10-13, it can be seen that in the range of 8-12 μm, the larger D1-D2 of the positive active material, the higher the compaction density of the positive electrode sheet 122, and the higher the volume energy density of the battery monomer 10. In Example 12, D1-D2 is too small, resulting in a decrease in the volume energy density of the battery monomer 10. In Example 13, D1-D2 is too large, and the compaction density of the positive electrode sheet 122 is actually reduced, which may be because when the particle size difference between large particles and small particles is too large, the pores between small particles are also more after small particles are filled into the gaps between large particles, which is not conducive to the increase of compaction density. Therefore, by selecting a positive active material with D1-D2 in the appropriate range, the volume energy density of the battery monomer 10 can be further improved, and in combination with the structural design of the battery monomer 10 in the present application, the high-energy-density battery monomer 10 has good safety performance and cycle performance.

[0201] From the comparative analysis of Examples 14-17, it can be seen that in the range of 5-8 mm, as H increases, the volume energy of the battery monomer 10 changes little, still remaining in a high range. In Example 16, H is too small, although space is saved, high volume energy density and good cycle performance are exhibited, but only 1 pass in the needle test, the safety performance is obviously not as good as other examples. Therefore, by controlling H in the range of 5-8 mm, the high-energy-density battery monomer 10 can have good safety performance and cycle performance.

[0202] The test methods of the physicochemical parameters and performance parameters involved in the embodiments of the present application are briefly introduced below. It should be understood that the following test methods are only examples, and other test methods known in the art can also be used for testing.

[0203] 1. Test method of particle size distribution of material

[0204] Unless otherwise specified, the particle size distribution parameters of the positive electrode active material determined by the particle size distribution measurement value in the present application, such as Dv10, Dv50 or Dv90, are determined by the particle size analyzer-laser diffraction method. Specifically, it can be referred to the standard GB / T19077-2016, and the laser diffraction scattering particle size analyzer is used to measure according to the manufacturer's instructions.

[0205] Test equipment: particle size testing instrument.

[0206] Pre-treatment: take a clean beaker, add an appropriate amount of sample to be tested, add dispersant after adding surfactant, and ultrasonic 120W / 5min to ensure that the sample is completely dispersed in the dispersant.

[0207] Test: after the sample is poured into the sample tower, it is circulated to the test optical path system with the solution. Under the irradiation of the laser beam, the particle size distribution characteristics of the particles can be obtained by receiving and measuring the energy distribution of the scattered light (light shielding degree: 8-12%).

[0208] 2. Test method of element molar fraction

[0209] Test equipment: inductively coupled plasma emission spectrometer (ICP).

[0210] Test method: digestion: 1+1 aqua regia, digestion method: flat plate / acid chasing digestion / microwave digestion (high temperature and high pressure ~200℃). The element mass fraction of nickel, cobalt, manganese and doped elements is tested, the molar mass of each element is calculated, and finally the molar ratio of nickel, cobalt and manganese is calculated.

[0211] 3. Test method of Dv10, Dv50 and Dv90

[0212] Test equipment: particle size testing instrument.

[0213] Pre-treatment: take a clean beaker, add an appropriate amount of sample to be tested, add dispersant after adding surfactant, and ultrasonic 120W / 5min to ensure that the sample is completely dispersed in the dispersant.

[0214] Test: after the sample is poured into the sample tower, it is circulated to the test optical path system with the solution. Under the irradiation of the laser beam, the particle size distribution characteristics of the particles can be obtained by receiving and measuring the energy distribution of the scattered light (light shielding degree: 8-12%).

[0215] Calculation: The particle sizes at the 10%, 50%, and 90% positions of the volume distribution are calculated on the volume particle size distribution curve from small to large, i.e., Dv10, Dv50, and Dv90.

[0216] 4. Test method for battery cell volume energy density

[0217] Charging and discharging is performed on a charging and discharging device at a current density of 0.33 C in the range of 2.5-4.25 V for 3 cycles, and the discharge energy Q of the 3rd cycle is taken. The diameter d and height h of the battery cell 10 are measured, and the volume V of the wound electrode assembly 12 is calculated as π x (d / 2)2x h. The energy density is Q / V (unit: Wh / L).

[0218] 5. Test method for cycle performance

[0219] The battery cell 10 to be tested is charged to 4.25 V at a charging current of 0.5 C, and CV is performed to 0.02 C. Then, the battery cell 10 is discharged to 2.5 V at a discharging current of 1 C. The cycle is continued until the capacity of the battery cell 10 is 80% of the initial capacity. The charging and discharging is stopped at this time, and the cycle number of the battery cell 10 at this time is the cycle number of the battery cell 10 to 80% SOH.

[0220] 6. Test method for needle puncture test

[0221] A steel needle with a diameter of 3 mm is used to puncture the largest surface of the battery cell 10 to be tested at a speed of 0.1 mm / s until thermal runaway occurs. It is observed whether the pressure relief mechanism is broken and whether the electrode terminal is ejected and the shell is broken in the case of thermal runaway. A group of battery cells can be used for testing, and each group includes 10 battery cells 10. The probability of the above-mentioned conditions occurring in the battery cells is observed. "1 / 10 passed" means that in a group of 10 battery cells 10 to be tested, 1 battery cell 10 does not have the conditions of the pressure relief mechanism being broken, the electrode terminal being ejected, and the shell being broken, i.e., 1 battery cell 10 passes the test.

[0222] 7. Test of capacity of battery cell

[0223] The capacity of the battery cell can be obtained by a charging and discharging machine test. Specifically, a battery cell with a nominal capacity of 32.5 Ah is tested by charging and discharging at a current density of 0.33 C in the voltage range of 2.5-4.25 V. After 3 cycles, the discharge capacity of the 3rd cycle is recorded as the actual capacity of the battery cell.

[0224] The capacity of the battery cell obtained by the test has a certain deviation, which is about 5% within a certain range.

[0225] 8. Test method for area S defined by pressure relief mechanism, height h of battery cell, and distance H between electrode assembly and pressure relief mechanism

[0226] CT scanning is performed on the battery cell, and the scanned image is tested. According to the scanned image, the height of the battery cell and the diameter R of the circular area defined by the pressure relief mechanism can be measured, wherein the area defined by the pressure relief mechanism can be calculated by the formula S = π x (R / 2) 2 . If the area defined by the pressure relief mechanism is irregularly shaped, the area can be calculated by fitting the irregular shape into a regular shape on a computer and then calculating the area of the regular shape.

[0227] According to the scanned image, H is tested along the thickness direction of the end cover. Specifically, in the area defined by the pressure relief mechanism, 5 points are selected along the thickness direction of the end cover on the side of the pressure relief mechanism close to the electrode assembly; 5 points are selected along the thickness direction of the end cover on the end of the negative electrode tab in the electrode assembly close to the end cover, which correspond to the 5 points selected on the pressure relief mechanism along the thickness direction of the end cover; the average value of the distances between the 5 points selected on the pressure relief mechanism and the 5 points selected on the electrode assembly is calculated, which is taken as the value of the gap H.

[0228] 9. Test method of the compaction density of the electrode tab

[0229] An electrode tab with an area of s1 is taken, and its thickness is measured as h1 and its weight is measured as m1; an aluminum foil with the same area is taken, and its thickness is measured as h2 and its weight is measured as m2; the compaction density of the electrode tab = (m1-m2) / [s1 x (h1-h2)], unit: g / cm 3 . The measurement deviation of the compaction density is within ±0.05 g / cm 3 .

[0230] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the application, and equivalent components can be substituted therefor. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized by, The battery cell comprises: a shell and a wound electrode assembly arranged in the shell, the wound electrode assembly comprising a negative electrode tab, a positive electrode tab and a separator film; at a winding start end of the wound electrode assembly, the negative electrode tab is wound to form a center hole.

2. The battery cell according to claim 1, wherein the positive electrode tab comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing transition metal oxide, the negative electrode tab comprises a negative electrode active material, the negative electrode active material comprises a silicon-containing material; and at the winding start end of the wound electrode assembly, a difference L1-L2 between a length L1 of the negative electrode tab and a length L2 of the positive electrode tab satisfies: 30mm≤L1-L2≤60mm.

3. The battery cell of claim 2, wherein, a diameter d of the center hole satisfies: nπd≥L1-L2, wherein π is a circular constant, n is an integer and n≥2.

4. The battery cell according to claim 2 or 3, characterized in that, in the lithium-containing transition metal oxide, a molar percentage n% of Ni element in transition metal elements satisfies: 80%≤n%<100%; the silicon-containing material comprises at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, a silicon-containing alloy or a silicon-oxygen-carbon composite material.

5. The battery cell of any one of claims 1-4, wherein, The battery cell comprises an end cover, the end cover comprises a pressure relief mechanism, the shell is provided with an opening, and the end cover covers the opening.

6. The battery cell of any one of claims 2-5, wherein, The volume particle size distribution of the lithium-containing transition metal oxide comprises two peaks, and the two particle sizes corresponding to the two peaks are D1 and D2, respectively, 2μm≤D1≤4μm; 10μm≤D2≤13.5μm; and The shell is provided with a limiting portion near the side of the end cover, and the limiting portion is used to limit the movement of the end cover towards the wound electrode assembly.

7. The battery cell of claim 6, wherein, The D1 and D2 satisfy: 8μm≤D2-D1≤11.5μm.

8. The battery cell according to claim 6 or 7, characterized in that The half-peak width W1 of the peak corresponding to D1 satisfies: 1.4μm≤W1≤2.0μm; and the half-peak width W2 of the peak corresponding to D2 satisfies: 8μm≤W2≤12μm.

9. The battery cell of any one of claims 2-8, wherein, The positive electrode active material satisfies at least one of the following conditions: (1) the Dv10 of the positive electrode active material satisfies: 1μm≤Dv10≤3μm; (2) the Dv50 of the positive electrode active material satisfies: 9μm≤Dv50≤11μm; (3) the Dv90 of the positive electrode active material satisfies: 14μm≤Dv90≤18μm.

10. The battery cell of any one of claims 2-9, wherein, The positive electrode active material further comprises a doping element, and the doping element comprises at least one of Zr, Sr, Al, Co, B, W, Nb, Sb, P and F.

11. The battery cell of any one of claims 2-10, wherein, The compaction density ρ of the positive electrode tab satisfies: 3.55g / cc≤ρ≤3.67g / cc; and In the thickness direction of the end cover, the distance H between the wound electrode assembly and the pressure relief mechanism satisfies: H≥5mm.

12. The battery cell of claim 11, wherein, 5mm≤H≤8mm.

13. The battery cell of any one of claims 1-12, wherein, The ratio of the mass of the battery cell electrolyte to the nominal capacity of the battery cell satisfies: and The separator film comprises a base film and a ceramic coating arranged on at least one side of the base film.

14. The battery cell of any one of claims 5-13, wherein, The end cover comprises an end cover body, and the pressure relief mechanism is arranged on the side of the end cover body facing the wound electrode assembly.

15. The battery cell of claim 14, wherein, The end cover body is provided with a score groove, and the area defined by the score groove forms the pressure relief mechanism.

16. The battery cell of any one of claims 5-15, wherein, The battery cell further includes a current collecting member housed in the case; In a thickness direction of the end cap, the current collecting member is located between the jelly-roll electrode assembly and the end cap, and is electrically connected to the tab of the jelly-roll electrode assembly and the end cap.

17. The battery cell of any one of claims 6-16, wherein, The limiting portion is a protrusion structure or a roller groove structure.

18. The battery cell of any one of claims 1-17, wherein, The capacity C of the battery cell satisfies 30 Ah ≤ C ≤ 40 Ah.

19. The battery cell of any one of claims 5-18, wherein, The area S of the region defined by the pressure relief mechanism satisfies: 500mm 2 ≤ S ≤ 800mm 2 .

20. A secondary battery characterized by comprising: The secondary battery includes the battery cell according to any one of claims 1 to 19.

21. An electrical device, comprising: The electric device includes the battery cell according to any one of claims 1 to 19, and / or the secondary battery according to claim 20.

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