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 provided with an opening; a wound electrode assembly disposed in the casing; and an end cover covering the opening, the end cover comprising a pressure relief mechanism. A limiting portion protrudes from the side of the casing close to the end cover and is used for restricting the end cover from moving in a direction approaching the wound electrode assembly. 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. The electrode assembly comprises a positive electrode sheet. The positive electrode sheet comprises a positive electrode active material. The positive electrode active material comprises a lithium-containing transition metal oxide. In the lithium-containing transition metal oxide, the molar percentage n% of the element Ni in the transition metal elements satisfies: n%≥80%. The volume particle size distribution of the lithium-containing transition metal oxide comprises two peaks, the two peaks corresponding to two particle sizes D1 and D2, respectively, where 2 μm≤D1≤4 μm and 10 μm≤D2≤13.5 μm.

Description

Battery cell, secondary battery and electric device

[0001] Cross-reference to related applications

[0002] This patent document claims priority to and the benefit of Chinese Patent Application No. 202411060660.9, 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

[0003] The present application relates to the field of batteries, and more particularly, to a battery cell, a secondary battery and an electric device. BACKGROUND

[0004] 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.

[0005] 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

[0006] 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.

[0007] In a first aspect, a battery cell is provided, the battery cell comprising: a shell provided with an opening; a wound electrode assembly arranged in the shell; an end cover covering the opening, the end cover comprising a pressure relief mechanism; a limiting portion protruding from a side of the shell close to the end cover, the limiting portion being configured to limit movement of the end cover in a direction close to the wound electrode assembly, a distance H between the wound electrode assembly and the pressure relief mechanism in a thickness direction of the end cover satisfying: H≥5mm; the wound electrode assembly comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material; the positive electrode active material comprising a lithium-containing transition metal oxide, a molar percentage n% of Ni element in transition metal elements in the lithium-containing transition metal oxide satisfying: 80%≤n%<100%, a volume particle size distribution of the lithium-containing transition metal oxide comprising two peaks, two particle sizes corresponding to the two peaks being D1 and D2 respectively, 2μm≤D1≤4μm; 10μm≤D2≤13.5μm.

[0008] In the embodiments of the present application, by setting the limiting portion and controlling the distance H between the wound electrode assembly and the pressure relief mechanism, the problem of the electrode assembly blocking the pressure relief mechanism during thermal runaway can be effectively solved. At the same time, by selecting high-nickel material as the positive active material, high gram capacity can be provided for the battery monomer, so that the battery monomer has high volumetric energy density in the case of large H. Selecting lithium-containing transition metal oxide with bimodal distribution of volume particle size as the positive active material helps to improve the compaction density of the positive electrode sheet, thereby further improving the energy density of the battery monomer. Thus, the scheme of the present application can make the battery monomer have high volumetric energy density and excellent safety performance by the structural design of the battery monomer and the material design of the battery monomer.

[0009] In an implementable manner, 5mm≤H≤10mm.

[0010] In an implementable manner, the capacity C of the battery monomer satisfies: 30Ah≤C≤40Ah.

[0011] In the embodiments of the present application, by matching the distance H between the wound electrode assembly and the pressure relief mechanism and the capacity C of the battery monomer, the battery monomer can have high volumetric energy density and excellent safety performance.

[0012] In an implementable manner, the capacity C of the battery monomer and the distance H between the wound electrode assembly and the pressure relief mechanism satisfy: C / 8≤H≤C / 4.

[0013] In the embodiments of the present application, by controlling the distance H between the capacity C of the battery monomer and the end cover to satisfy the above relationship, the probability of the pressure relief mechanism opening smoothly under the thermal runaway state of the battery monomer can be further improved, thereby further improving the safety performance of the battery monomer.

[0014] In an implementable manner, the area S of the region defined by the pressure relief mechanism satisfies: 500mm 2 ≤S≤800mm 2 .

[0015] In the embodiments of the present application, by controlling the area of the region defined by the pressure relief mechanism within a suitable range, the pressure relief mechanism is more prone to rupture when the battery monomer undergoes thermal runaway, thereby facilitating the end cover to have a larger tearing opening and facilitating the discharge of high-temperature and high-pressure substances inside the battery monomer.

[0016] In an implementable manner, the capacity C of the battery monomer and the area S of the region defined by the pressure relief mechanism satisfy: 12mm 2 / Ah≤S / C≤20mm 2 / Ah.

[0017] In the embodiments of the present application, by making the area S of the pressure relief mechanism of the battery monomer and the capacity C of the battery monomer satisfy the above relationship, the probability of the pressure relief mechanism opening smoothly under the thermal runaway state of the battery monomer can be further improved, thereby further improving the safety performance of the battery monomer.

[0018] In an implementable manner, 5mm≤H≤8mm.

[0019] In an implementable manner, the wound electrode assembly further comprises a negative electrode tab and a separator film, and at the winding starting end of the wound electrode assembly, the negative electrode tab is wound to form a center hole.

[0020] In the embodiments of the present application, the center hole of the wound electrode assembly can be formed by winding the negative electrode tab, in other words, the center hole can be formed only by the empty winding of the negative electrode tab. Compared with directly winding the electrode assembly to form the center hole, the self-supporting of the center hole can be realized by the empty winding of the negative electrode tab, which reduces the lithium precipitation caused by the collapse of the center hole, and helps to improve the safety performance of the battery monomer.

[0021] In an implementable manner, the negative electrode tab comprises a negative electrode active material, the negative electrode active material comprises a silicon-containing material, 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; and at the winding starting end of the wound electrode assembly, the difference L1-L2 between the length L1 of the negative electrode tab and the length L2 of the positive electrode tab satisfies: 30mm≤L1-L2≤60mm.

[0022] In the embodiments of the present application, by matching the high-gram-capacity negative electrode active material and the length of the empty-wound negative electrode tab, the safety performance of the battery monomer can be improved while further improving the energy density of the battery monomer.

[0023] In an implementable manner, the diameter d of the center hole satisfies: nπd≥L1-L2, wherein π is a circular constant, n is an integer and n≥2.

[0024] In an implementable manner, 8μm≤D2-D1≤11.5μm.

[0025] In an implementable manner, 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.

[0026] In an implementation, 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; (3) the Dv90 of the positive electrode active material satisfies: 14 μm≤Dv90≤18 μm.

[0027] In an implementation, the compaction density p of the positive electrode tab satisfies: 3.55 g / cm 3 ≤p≤3.67 g / cm 3 .

[0028] In the embodiments of the present application, the powder compaction density of the positive electrode tab is controlled in a large range, which is helpful to further improve the volume energy density of the battery cell.

[0029] In an implementation, 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.

[0030] In an implementation, 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.

[0031] In an implementation, the end cover body is provided with a score groove, and an area defined by the score groove forms the pressure relief mechanism.

[0032] In an implementation, the battery cell further comprises a current collecting member accommodated in the shell, and the current collecting member is located between the wound electrode assembly and the end cover in the thickness direction of the end cover, and the current collecting member is electrically connected to the tab of the wound electrode assembly and the end cover.

[0033] In an implementation, the limiting portion is in a protrusion structure or a roller groove structure.

[0034] In a second aspect, a secondary battery is provided, which comprises the battery cell of any of the implementations of the first aspect.

[0035] In a third aspect, a power consumption device is provided, which comprises the battery cell of any of the implementations of the first aspect and / or the secondary battery of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from the drawings without any creative effort.

[0037] Fig. 1 is a schematic view of a battery cell.

[0038] Fig. 2 is an enlarged schematic view of the portion indicated by the dashed line in Fig. 1.

[0039] Fig. 3 is a particle size distribution diagram of a positive electrode active material.

[0040] Fig. 4 is an SEM diagram of a positive electrode active material.

[0041] Fig. 5 is a schematic view of a battery. DETAILED DESCRIPTION

[0042] Hereinafter, the embodiments of the lithium ion battery and the electric device of the present application are specifically disclosed with appropriate reference to the 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 and 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. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0043] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can include or exclude the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise stated, the numerical range "a-b" represents a shorthand notation for any real combination of integers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when a parameter is stated to be ≥2 integers, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is more than two; the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like only indicates or simplifies the description of the present application, 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 descriptive purposes and cannot be understood as indicating or implying relative importance.

[0045] 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 exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0046] Unless otherwise specified, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0048] Unless otherwise specified, the following terms have the following meanings. Any undefined term has its technically recognized meaning.

[0049] 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 include a battery module or a battery pack, etc.

[0050] If mentioned, "bimodal particle size distribution" refers to the case where there are two distinct peaks in the volume particle size distribution curve of the material. This indicates that there are two main particle sizes in the particle size distribution of the material.

[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, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charging and discharging process of the battery, 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, which prevents the positive and negative electrodes from short-circuiting while allowing active ions to pass through, so that the secondary battery can normally perform electrochemical reactions.

[0053] With the increasingly wide application of secondary batteries, there are further requirements for their energy density and capacity. On the other hand, high-energy-density battery cells release more heat when they are in thermal runaway, and the electrode assembly, resulting in safety problems of high-energy-density battery cells.

[0054] Therefore, the embodiments of the present application provide a battery cell, a secondary battery and an electric device, which can have high volumetric energy density and excellent 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 an embodiment of the present application. FIG. 2 is an enlarged schematic diagram of the portion in dashed line in FIG. 1. As shown in FIGS. 1-2, the battery cell 10 includes a shell 11, a wound electrode assembly 12 and an end cover 13, wherein the shell 11 is provided with an opening, the end cover 13 is used to cover the opening, the end cover 13 includes a pressure relief mechanism 14, the wound electrode assembly 12 is arranged in the shell 11, and a limiting portion 111 is protruded on one side of the shell 11 close to the end cover 13, the limiting portion 111 is used to limit the movement of the end cover 13 in the direction close to the wound electrode assembly 12, and in the thickness direction of the end cover 13, the distance H between the wound electrode assembly 12 and the pressure relief mechanism 14 satisfies: H≥5mm. The wound electrode assembly 12 includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium-containing transition metal oxide, wherein the molar percentage n% of Ni element in the transition metal elements in the lithium-containing transition metal oxide satisfies: 80%≤n%<100%.

[0058] Specifically, the end cover 13 is used to cover the opening of the shell 11 to isolate the internal environment of the battery cell 10 from the external environment. The end cover 13 covers the opening of the shell 11, and the end cover 13 and the shell 11 together define a sealed space for accommodating the wound electrode assembly 12, the electrolyte and other components.

[0059] The shape of the end cover 13 can be adapted to the shape of the housing 11. For example, the housing 11 is a cuboid structure, and the end cover 13 is a rectangular plate structure adapted to the housing 11. For another example, the housing 11 is a cylindrical structure as shown in FIGS. 1-2, and the end cover 13 is a circular plate structure adapted to the housing 11. The material of the end cover 13 can be various. For example, the end cover 13 can be a metal material, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cover 13 can be the same as or different from the material of the housing 11. For example, the material of the end cover 13 is aluminum.

[0060] The pressure relief mechanism 14 is an element or component for being actuated to release the pressure or temperature inside the battery cell 10 when the pressure or temperature inside the battery cell 10 reaches a predetermined threshold. The predetermined threshold can be adjusted according to design requirements. For example, the predetermined threshold depends on the material of one or more of the positive electrode plate, the negative electrode plate, the electrolyte, and the separator in the battery cell 10. "Actuated" means that the pressure relief mechanism 14 generates an action or is activated to a certain state, so that the pressure and temperature inside the battery cell 10 are released. The action generated by the pressure relief mechanism 14 can include but is not limited to at least one of the following: the pressure relief mechanism 14 is broken, cracked, torn or opened, etc. When the pressure relief mechanism 14 is actuated, the high-temperature and high-pressure substances inside the battery cell 10, as the discharge, are excluded from the actuated part. In this way, the battery cell 10 can be relieved of pressure and temperature under controllable pressure or temperature, thereby reducing the risk of more serious accidents.

[0061] The discharge from the battery cell 10 mentioned in the embodiments of the present application includes but is not limited to the electrolyte, the dissolved or split positive and negative electrode plates, the fragments of the separator, the high-temperature and high-pressure gas generated by the reaction, the flame, etc.

[0062] The pressure relief mechanism 14 can be a separate structure from the end cap 13. The pressure relief mechanism 14 is a separate component mounted on the end cap 13. For example, the pressure relief mechanism 14 can be a rupture disc, a gas valve, a pressure relief valve, or a safety valve mounted on the end cap 13, and can be a pressure-sensitive or temperature-sensitive component or structure. The pressure relief mechanism 14 can also be an integral structure with the end cap 13. The pressure relief mechanism 14 is a part of the end cap 13. For example, the pressure relief mechanism 14 can be formed by providing a notch on the end cap 13, where the thickness of the notch is significantly less than the thickness of other areas of the end cap 13. The notch is the weakest point of the pressure relief mechanism 14. When the gas generated by the battery cell 10 causes the internal pressure to rise to 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 to a threshold value, the pressure relief mechanism 14 can rupture at the notch to allow the inside of the battery cell 10 to communicate with the outside, and the gas pressure and temperature can be released outward through the rupture of the pressure relief mechanism 14, thereby preventing the battery cell 10 from exploding. As an example, the end cap 13 has a notch groove, and the area defined by the notch groove forms the pressure relief mechanism 14. More specifically, the notch groove can be annular with a gap.

[0063] In the battery cell 10, there can be one or two end caps 13. If the shell 11 is a hollow structure with one open end, there is one end cap 13. If the shell 11 is a hollow structure with two open ends, there are two end caps 13, each covering one of the two open ends of the shell 11. In embodiments where the battery cell 10 has two end caps 13, both end caps 13 are provided with a pressure relief mechanism 14. As shown in FIGS. 1-2, in cases where the battery cell 10 has two open ends but only one end cap 13 is provided with a pressure relief mechanism 14, the other structure without a pressure relief mechanism 14 is a top cap 15. In a more specific example, the pressure relief mechanism 14 is provided on the inner side of the end cap 13, i.e., the side of the end cap 13 facing the jelly-roll electrode assembly 12.

[0064] One of the positive and negative tabs of the jelly-roll electrode assembly 12 is electrically connected to one end cap 13, and the other is electrically connected to the shell. In cases where the shell 11 has one open end, the end of the shell 11 facing away from the end cap 13 can be provided with an electrode terminal, which is insulated from the shell 11. One of the positive and negative tabs of the jelly-roll electrode assembly 12 is electrically connected to the shell 11, and the other is electrically connected to the electrode terminal.

[0065] The limiting portion 111 is a structure for limiting the movement of the end cover 13 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 13, and can be understood as extending substantially along the thickness direction of the end cover 13. 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 arranged at different positions and connected end to end.

[0066] 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.

[0067] The number of limiting portions 111 on the shell 11 can be related to the number of pressure relief mechanisms 14 on the end cover 13. In the case where the battery monomer 10 includes one end cover 13, this means that at least one pressure relief mechanism 14 is arranged on the end cover 13, and one corresponding limiting portion 111 is arranged on the shell 11 near one end of the end cover 13. In the case where the battery monomer 10 includes two end covers 13, this means that at least one pressure relief mechanism 14 is arranged on each of the two end covers 13, and corresponding limiting portions 111 are arranged on the shell 11 near the two ends of the two end covers 13, respectively. In the case where the battery monomer 10 includes one end cover 13 and one top cover 15, this means that the battery monomer 10 can only be provided with one limiting portion 111 near the end cover 13.

[0068] The number of limiting portions 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 13, and when some of the limiting portions 111 are deformed and fail, the other limiting portions 111 can maintain a certain distance between the winding electrode assembly 12 and the end cover 13, limiting the winding electrode assembly 12 from directly contacting the pressure relief mechanism 14 on the end cover 13 and thereby blocking the pressure relief mechanism 14.

[0069] When the winding electrode assembly 12 is arranged in the shell 11 provided with the limiting portion 111, the winding electrode assembly 12 can directly abut against the limiting portion 111, or can abut against the limiting portion 111 through other components, such as the current collecting member.

[0070] In this embodiment, the housing 11 of the battery monomer 10 is provided with a limiting portion 111 near the end cover 13, which can keep a certain distance H between the wound electrode assembly 12 and the pressure relief mechanism 14, and control H in a larger range, which can effectively prevent the wound electrode assembly 12 from moving and blocking the pressure relief mechanism 14 on the end cover 13 when the battery monomer 10 is in thermal runaway. A larger H will occupy part of the space inside the battery monomer 10, affecting the volumetric energy density of the battery monomer. In this embodiment, by matching a lithium-containing transition metal oxide with a higher nickel content as the positive active material, such as NCM, NCA, etc., the material itself has a higher gram capacity, which can compensate for the loss of volumetric energy density due to a larger H, so that the battery monomer 10 has a high volumetric energy density. Therefore, by matching the structural design of the battery monomer 10 with the material design of the battery monomer 10, the battery monomer 10 can have high energy density and excellent safety performance.

[0071] The distance H between the wound electrode assembly 12 and the pressure relief mechanism 14 can be the minimum distance between the wound electrode assembly 12 and the pressure relief mechanism 14 along the thickness direction of the end cover 13.

[0072] In one embodiment, 5mm≤H≤10mm; optionally, 5mm≤H≤8mm.

[0073] Specifically, H can be 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, or a value within the range obtained by any two of the above combinations.

[0074] In this embodiment, by controlling H in a larger and appropriate range, the risk of the wound electrode assembly 12 blocking the pressure relief mechanism 14 when the battery monomer 10 is in thermal runaway can be reduced as much as possible, while the impact on the volumetric energy density of the battery monomer 10 is reduced.

[0075] In one embodiment, the capacity C of the battery monomer 10 satisfies: 30Ah≤C≤40Ah.

[0076] Specifically, C can be 30Ah, 32Ah, 34Ah, 36Ah, 38Ah, 40Ah, or a value within the range obtained by any two of the above combinations.

[0077] In one embodiment, the capacity C of the battery monomer 10 and the distance H between the wound electrode assembly 12 and the pressure relief mechanism 14 satisfy: C / 8≤H≤C / 4.

[0078] The heat released by the wound electrode assembly 12 when thermal runaway occurs is positively correlated with its capacity; by controlling the position of the limiting portion 111 on the shell 11, the distance H between the wound electrode assembly 12 and the end cover 13 can be adjusted. In the embodiments of the present application, by matching the range of C and the range of H, the relationship between C and H is controlled to satisfy the above relationship, which can make the pressure relief mechanism 14 rupture smoothly when the battery monomer 10 is in thermal runaway, while reducing the influence of H on the volume energy density of the battery monomer 10, so that the battery monomer 10 has high volume energy density and excellent safety performance, and meets the application requirements of long-term safe and sustainable use of the battery monomer 10.

[0079] In one embodiment, the area S of the region defined by the pressure relief mechanism 14 satisfies: 500mm 2 ≤S≤800mm 2 .

[0080] Specifically, the area of the region defined by the pressure relief mechanism 14 refers to the vertical projection area of the region defined by the pressure relief mechanism 14 on the plane of the end cover. For example, the area of the region defined by the pressure relief mechanism 14 is the area of the region defined by the notch groove. S can be 500mm 2 , 550mm 2 , 600mm 2 , 650mm 2 , 700mm 2 , 750mm 2 , 800mm 2 , or a value within the range obtained by any two of the above combinations.

[0081] In the embodiments, the larger the area of the pressure relief mechanism 14, the easier the pressure relief mechanism 14 ruptures when the battery monomer 10 is in thermal runaway, which is beneficial to the discharge of high-temperature and high-pressure substances inside the battery monomer 10. The larger the area of the pressure relief mechanism 14, the greater the risk of the pressure relief mechanism 14 rupturing under normal circumstances, and the greater the influence on the connection (such as welding) between the end cover 13 and the shell 11. Therefore, by controlling the area of the pressure relief mechanism 14 within a suitable range, the risk of the pressure relief mechanism 14 rupturing during normal use of the battery monomer 10 can be reduced, and the pressure relief mechanism 14 can be ruptured in time when the battery monomer 10 is in thermal runaway, thereby balancing the long-term use reliability and the reliability in thermal runaway of the battery monomer 10.

[0082] In one embodiment, the capacity C of the battery monomer 10 and the area S of the region defined by the pressure relief mechanism 14 satisfy: 12mm 2 / Ah≤S / C≤20mm 2 / Ah.

[0083] Specifically, S / C can be 12mm2 Ah, 13mm 2 Ah, 14mm 2 Ah, 15mm 2 Ah, 16mm 2 Ah, 17mm 2 Ah, 18mm 2 Ah, 19mm 2 Ah, 20mm 2 Ah, or a value within a range obtained by any two of the above value combinations. The greater the capacity of the battery cell 10, the greater the severity of thermal runaway of the battery cell 10, and the larger the area of the pressure relief mechanism 14 is conducive to actuation and rupture to smoothly discharge the emissions within the battery cell 10 in the event of thermal runaway.

[0084] In this embodiment, in the case of S / Q≥12mm 2 Ah, it is conducive to making the end cover 13 have a larger tearing opening and tearing degree in the event of thermal runaway of the battery cell 10, and facilitating the discharge of high-temperature and high-pressure substances inside the battery cell 10; in the case of S / Q≤20mm 2 Ah, the influence of the pressure relief mechanism 14 on the connection (such as welding) between the end cover 13 and the shell 11 can be reduced, and the connection (such as welding) between the end cover 13 and the shell 11 is facilitated. By controlling S and C to satisfy the above relationship, both the discharge of high-temperature and high-pressure substances in the event of thermal runaway of the battery cell 10 and the connection between the shell 11 and the end cover 13 are facilitated, and the reliability of the structure of the battery cell 10 is improved.

[0085] In one embodiment, the jelly-roll electrode assembly 12 further includes a negative electrode tab and a separator film, and at the winding start end of the jelly-roll electrode assembly 12, the negative electrode tab is wound to form a central hole.

[0086] 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 winding shaft is pulled out after winding is completed, a center hole is left at the center of the columnar jelly-roll type electrode assembly 12. The stability of the center hole structure is crucial to the cycle performance of the battery cell 10. However, the jelly-roll type electrode assembly 12 will swell during the cycle of the battery cell 10, and the center hole structure is prone to collapse, thus exacerbating the polarization reaction at the center hole, and is prone to cause lithium precipitation, which is not conducive to the safety performance of the battery cell 10. In the present embodiment, the center hole is formed by winding the negative electrode sheet, in other words, the center hole is obtained by winding the negative electrode sheet alone. The winding of the negative electrode sheet alone refers to the case where only the negative electrode sheet is wound. Compared with the scheme of directly winding all electrode assemblies (positive electrode sheet, negative electrode sheet and separator film) to form a center hole, the negative electrode sheet alone does not participate in the electrochemical reaction of lithium ion deintercalation during the cycle of the battery cell 10, so the electrode sheet itself at the center hole will not swell seriously, thus forming a relatively stable center hole structure, which can resist the extrusion of the center hole structure caused by the swelling of the electrode assembly. On the other hand, the negative electrode active material of the negative electrode sheet is an active material for lithium ion intercalation, and the positive electrode 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 a center hole, the selection of the negative electrode sheet for winding alone to form a center hole can avoid the dissolution of the lithium source or lithium supplement in the positive electrode sheet and thus cause negative electrode lithium precipitation. Thus, the present embodiment can improve the problem of easy collapse of the center hole by winding the negative electrode sheet alone, and improve the cycle performance of the battery cell 10.

[0087] In one embodiment, the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a silicon-containing material, the silicon-containing material includes 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; and at a winding start end of the jelly-roll type electrode assembly 12, a difference L1-L2 between a length L1 of the negative electrode sheet and a length L2 of the positive electrode sheet satisfies: 30 mm≤L1-L2≤60 mm.

[0088] It should be understood that the difference L1-L2 between the length L1 of the negative electrode sheet and the length L2 of the positive electrode sheet refers to the length of the negative electrode sheet which is longer than the positive electrode sheet at the winding start end, and can also be understood as the length of the negative electrode sheet which is wound alone.

[0089] In this embodiment, a silicon-containing material is selected as the negative active material in the negative electrode sheet, which has a high gram capacity. The battery monomer 10 can obtain a high energy density by matching the high nickel positive active material. Based on the matching of the high gram capacity active material, while controlling the values of L1-L2 within a suitable range, the larger L1-L2, the longer the length of the negative electrode sheet used to form the center hole, the better the structural stability of the center hole, which can provide good structural stability for the wound electrode assembly 12. At the same time, controlling L1-L2 not to exceed 60 mm reduces the waste of the negative electrode sheet. Therefore, by selecting high gram capacity active materials and controlling L1-L2 within a suitable range, the energy density of the battery monomer 10 can be improved while improving the structural stability of the wound electrode assembly 12, so that the battery monomer 10 has high energy density and good safety performance.

[0090] In one embodiment, the diameter d of the center hole satisfies: nπd≥L1-L2, where π is a circular constant, n is an integer and n≥2.

[0091] Specifically, πd represents the circumference of the innermost circle of the negative electrode sheet forming the center hole. The length of the negative electrode sheet of the empty roll is usually not too long, so the diameters of the several circumferences forming the center hole can be approximately the same from the radial direction of the wound electrode assembly 12. (L1-L2) / πd can represent the number of winding turns of the negative electrode sheet wound into the center hole. n≥2 represents that the center hole is obtained by at least winding the negative electrode sheet two turns.

[0092] The volume particle size distribution of the lithium-containing transition metal oxide of the embodiments of the present application includes two peaks, and the two particle sizes corresponding to the two peaks are D1 and D2, 2 μm≤D1≤4 μm; 10 μm≤D2≤13.5 μm.

[0093] Specifically, 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. The "particle size bimodal distribution" refers to the case where there are two obvious peaks in the particle size distribution curve of the material. This indicates that there are two main particle sizes in the particle size distribution of the material. 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 the range obtained by any two of the above value combinations. 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 the range obtained by any two of the above value combinations.

[0094] Exemplarily, the particles with the volume particle size D1 are usually small single-crystal particles, and the particles with the volume particle size D2 are usually large multi-crystal particles. The lithium-containing transition metal oxide material with the volume particle size bimodal distribution can itself achieve a higher tap density, which is helpful to further improve the energy density of the battery monomer 10. Thus, in the embodiment, by selecting the lithium-containing transition metal oxide with the volume particle size bimodal distribution, the energy density of the battery monomer 10 is further improved.

[0095] In one embodiment, 8 μm≤D2-D1≤11.5 μm.

[0096] Specifically, D2-D1 represents the difference between the horizontal coordinates (particle sizes) corresponding to the two peaks in the volume particle size bimodal distribution graph. 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 the range obtained by any two of the above combinations. The value of D2-D1 also has a certain influence on the tap density of the positive electrode tab. Within a certain range, the greater D2-D1 is, the greater the tap density of the positive electrode tab is. The possible reason is that the voids between large particles can be filled with small particles, thereby improving the tap density of the positive electrode tab. On the other hand, a large D2-D1 means that the particle size of the small particles is smaller compared to the large particles. If D2-D1 is too large, the number of small particles in the voids between large particles can be too large, and the voids between small particles become more, which is not conducive to the increase of the tap density. Thus, by controlling D2-D1 within a suitable range, the tap density of the positive electrode tab can be further improved, and the volumetric energy density of the battery monomer 10 is further improved.

[0097] FIG. 3 shows a volume particle size distribution graph of a positive electrode active material according to the present application.

[0098] As shown in FIG. 3, in one embodiment, 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.

[0099] Specifically, the half peak width refers to the peak width at half the height of the peak in the spectrum. A straight line parallel to the bottom of the peak is drawn through the midpoint of the peak height, 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 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 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, or a value within the range obtained by any two of the above value combinations. W2 can be 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a value within the range obtained by any two of the above value combinations.

[0100] 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 μm≤Dv10≤3 μm; (2) the Dv50 of the positive electrode active material satisfies: 9 μm≤Dv50≤11 μm; (3) the Dv90 of the positive electrode active material satisfies: 14 μm≤Dv90≤18 μm.

[0101] Specifically, the Dv10 can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or a value within the range obtained by any two of the above value combinations. The Dv50 can be 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, or a value within the range obtained by any two of the above value combinations. The Dv90 can be 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, or a value within the range obtained by any two of the above value combinations.

[0102] In one embodiment, the positive electrode tab has a compacted density p that satisfies: 3.55 g / cm 3 ≤p≤3.67 g / cm 3 .

[0103] Specifically, p can be 3.55 g / cm 3 , 3.56 g / cm 3 , 3.57 g / cm 3 , 3.58 g / cm 3 , 3.59 g / cm 3 , 3.6 g / cm 3 , 3.61 g / cm 3 , 3.62 g / cm 3 , 3.63 g / cm 3 , 3.64 g / cm 33.65 g / cm3 3 3.66 g / cm3 3 3.67 g / cm3 3 or a value within a range obtained by combining any two of the above-mentioned numerical values. Due to the bimodal distribution of the 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, so as to achieve high tap density. It should be understood that the tap density mentioned in the present application is the tap density of the electrode sheet, which will change after the battery is formed or cycled, resulting in a certain error. The error range of the tap density of the positive electrode sheet of the present application is less than or equal to ±0.1 g / cm3 3 .

[0104] In one embodiment, the positive active material further comprises a doping element, the doping element comprising at least one of Zr, Sr, Al, Co, B, W, Nb, Sb, P, F.

[0105] In the present embodiment, by further introducing a doping element into the positive active material, the specific capacity of the positive active material is further improved, so as to further improve the energy density of the battery cell 10.

[0106] In one embodiment, the battery cell 10 further comprises: a current collecting member accommodated in the shell 11; in the thickness direction of the end cover 13, the current collecting member is located between the wound electrode assembly 12 and the end cover 13, and the current collecting member is electrically connected to the tab of the wound electrode assembly 12 and the end cover 13.

[0107] Specifically, the current collecting member can be a disc-shaped member arranged between the end cover 13 and the wound electrode assembly 12, for example, the shell 11 is a cylinder, and the current collecting member is a disc structure. The current collecting member can be a metal conductor, such as copper, iron, aluminum, steel, aluminum alloy, etc.

[0108] 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 mentioned in the present application can be direct electrical connection (such as welding, abutting), or indirect electrical connection through other current conducting components.

[0109] Next, taking a lithium ion battery as a specific example, the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte in the secondary battery are introduced in detail. It should be understood that the lithium ion battery is only an example, and the scheme provided by the present application can also be applied to other types of secondary batteries, such as sodium ion batteries, magnesium ion batteries, lithium-sulfur batteries, etc.

[0110] [Negative electrode sheet]

[0111] The negative electrode sheet generally includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material.

[0112] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two surfaces of the negative electrode current collector.

[0113] In one embodiment, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0114] In one embodiment, the negative electrode active material can employ a negative electrode active material for a battery known in the art. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0115] In one embodiment, the negative electrode active material is a silicon-containing material. 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. By selecting the silicon-containing material as the negative electrode active material, it is possible to further improve the volumetric energy density of the battery cell 10, and in combination with the structural design of the battery cell 10 in the foregoing embodiment, it is possible to achieve both high energy density and excellent safety performance.

[0116] In one embodiment, the negative electrode film layer further includes a binder. The binder can 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).

[0117] 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.

[0118] 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.

[0119] In one embodiment, the negative electrode sheet 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, a negative electrode sheet is obtained.

[0120] [Positive electrode sheet]

[0121] The positive electrode sheet 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.

[0122] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction of the positive electrode current collector itself, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0123] In one embodiment, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a 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.).

[0124] It has been introduced above that the positive electrode active material of the present application is a high-nickel material.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] In one embodiment, the cathode 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.

[0131] In one embodiment, the cathode 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.

[0132] In one embodiment, the cathode electrode sheet can be prepared by forming the above-mentioned components for preparing the cathode electrode sheet into a cathode slurry, respectively. For example, the first cathode active material and / or the second cathode active material, the conductive agent, the binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a cathode slurry. The cathode slurry is then coated on a cathode current collector, and after processes such as drying, cold pressing, etc., a cathode electrode sheet is obtained.

[0133] [Electrolyte]

[0134] The electrolyte functions to conduct ions between the cathode electrode sheet and the anode electrode sheet. 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.

[0135] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0136] 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.

[0137] 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, butanedisulfone, methyl ethyl sulfone, and diethyl sulfone.

[0138] 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.

[0139] [Separator]

[0140] 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.

[0141] 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 does not contain a PVDF coating.

[0142] In one embodiment, the negative electrode tab, the positive electrode tab, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0143] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape.

[0144] [Battery]

[0145] 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.

[0146] 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 housed in the box body.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] The battery 20 can further 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 structure to cover the opening. For example, the second box part 32 is a hollow cuboid with an opening, and the first box part 31 is a plate-shaped structure. Then, the first box part 31 is overlapped at the opening of the second box part 32 to form the box 3 with a closed cavity, which can be used to accommodate the plurality of battery cells 10.

[0151] In addition, the application also provides a power utilization device, which includes the secondary battery in the foregoing embodiments.

[0152] For another example, different from 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 the 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.

[0153] In some embodiments, the battery 20 can further include other components. For example, the battery 20 can further include a current collecting 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 current collecting component can realize the electrical connection between the battery cells 10 by connecting the electrode terminals of the battery cells 10; or the current collecting component can also realize the electrical connection between the battery cells 10 by connecting other components of the battery cells 10. The current collecting 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.

[0154] The battery cells 10 can directly constitute the battery 20, or can first constitute a battery module, and then the plurality of battery modules constitute the battery 20.

[0155] [Power utilization device]

[0156] The embodiment of the present application provides a power utilization device, which comprises the battery described in the above embodiment.

[0157] 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.

[0158] The present application provides a power utilization device, which is a vehicle.

[0159] 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 can 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.

[0160] 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 indicated 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 indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0161] [Embodiments and comparative examples]

[0162] Embodiment 1

[0163] (1) Preparation of the negative electrode sheet

[0164] 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.

[0165] (2) Preparation of the positive electrode sheet

[0166] (2-1) Preparation of the first positive electrode material

[0167] 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)2with a Dv50 of 3.4μm. The precursor Ni 0.90 Co 0.06 Mn 0.04 (OH)2: LiOH·H2O are mixed in a molar ratio of 100:105, then reacted with the material at 800°C and pure oxygen for 15h, and then subjected to airflow crushing to prepare a first positive electrode material with a Dv50 of 3μm.

[0168] (2-2) Preparation of the second positive electrode material

[0169] 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)2with a Dv50 of 13.5μm. The precursor Ni 0.92 Co 0.06 Mn 0.02 (OH)2: LiOH·H2O are mixed in a molar ratio of 100:105, then reacted at 750°C and pure oxygen for 15h, and then subjected to mechanical crushing to prepare a second positive electrode material with a Dv50 of 13μm.

[0170] (2-3) Preparation of the positive electrode active material

[0171] The first positive electrode material and the second positive electrode material were mixed uniformly at a mass ratio of 8:2 to obtain a positive electrode active material. FIG. 3 is a volume particle size distribution diagram of the positive electrode active material. FIG. 4 is a scanning electron microscope diagram of the positive electrode active material. In the positive electrode active material, D2 = 13 μm, D1 = 3 μm, Dv10 = 2.3 μm, Dv50 = 10.7 μm, Dv90 = 17.4 μm, W1 = 1.67 μm, and W2 = 11.6 μm.

[0172] (2-4) Preparation of the positive electrode tab

[0173] The positive electrode active material, polyvinylidene fluoride, and conductive carbon black were mixed at a mass ratio of 90:5:5, and then N-methyl pyrrolidone (NMP) was added. After stirring for 2 h, the mixture was stirred in a homogenizer at 1200 r / min until it was uniformly mixed. Then, the mixture was uniformly coated on a 13 μm thick aluminum foil. After coating, the mixture was dried in a drying oven at 120 °C, cold-pressed, and cut to obtain a positive electrode tab.

[0174] (3) Preparation of the battery monomer

[0175] The positive electrode tab, the separator, and the negative electrode tab were sequentially stacked and wound to obtain an electrode assembly. The electrode assembly was placed in a shell, electrolyte was injected, and then the shell was packaged to obtain a battery monomer. The electrolyte was an electrolyte with a lithium salt concentration of 1 M and with ethylene carbonate (EC) and diethyl carbonate (DEC) as solvents (volume ratio 1:2).

[0176] In the battery monomer of Example 1, H = 5 mm and S = 615 mm. 2 D2-D1 = 10 μm.

[0177] Examples 2-5

[0178] Compared with Example 1, the difference lies in the value of D1-D2, which is different from that of Example 1.

[0179] Examples 6-8

[0180] Compared with Example 1, the difference lies in the value of H, which is different from that of Example 1.

[0181] Examples 9-11

[0182] Compared with Example 1, the difference lies in the value of S, which is different from that of Example 1.

[0183] Comparative Examples 1-2

[0184] Compared with Example 1, the positive electrode active material used in Comparative Example 1 is NCM333. Compared with Example 1, in the battery monomer 10 of Comparative Example 2, H = 3 mm.

[0185] Product and performance parameters of examples 1-11 and comparative examples 1-2.

[0186] Table 1: Product and performance parameters of examples 1-11 and comparative examples 1-2

[0187] In Table 1, “D1” represents the particle size corresponding to the smaller main peak in the volume particle size distribution of the positive electrode active material; “D2” represents the particle size corresponding to the other main peak in the volume particle size distribution 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; “C” represents the cell capacity of the battery cell 10; “H” represents the distance between the wound electrode assembly 12 and the pressure relief mechanism 14, and “S” represents the area of the region defined by the pressure relief mechanism 14; “VED” represents the volumetric energy density of the battery cell 10; and “puncture test” represents the performance of the battery cell 10 in the puncture test. For specific test methods and processes, please refer to the test section below.

[0188] According to the comparative analysis of the examples and comparative examples, the battery cells 10 of the examples all exhibit high volumetric energy density and excellent safety. The volumetric energy density of comparative example 1 is not as high as that of the examples, and the safety of comparative example 2 is not as good as that of the examples. This shows that by setting the limiting portion and controlling the distance H between the wound electrode assembly 12 and the pressure relief mechanism 14 to be relatively large, and by using high-nickel material as the positive electrode active material, the battery cell 10 can have both high volumetric energy density and excellent safety.

[0189] According to the comparative analysis of examples 1-5, it can be seen that within the range of 8-11.5 pm, the larger the D1-D2 of the positive electrode active material, the greater the compacted density of the positive electrode sheet, and the higher the volumetric energy density of the battery cell 10. In example 4, the D1-D2 is too small, resulting in a significant reduction in the volumetric energy density of the battery cell 10. In example 5, the D1-D2 is too large, and the compacted density of the positive electrode sheet is actually reduced, which may be because when the difference between the large particle size and the small particle size is too large, there are more pores between the small particles after the small particles fill the gaps between the large particles, which is not conducive to the increase of the compacted density. Therefore, by selecting a positive electrode active material with a D1-D2 within an appropriate range, the volumetric energy density of the battery cell 10 can be further improved, and the battery cell 10 with high safety can have high volumetric energy density.

[0190] From the comparative analysis of Examples 1, 6-8, it can be seen that in the range of 5-10 mm, the battery monomer 10 exhibits excellent safety performance. In Example 8, although the safety performance is excellent, the volumetric energy density of the battery monomer 10 is greatly reduced. In Comparative Example 2, H is too small, although space is saved, the volumetric energy density is higher than that of the example, but only 1 pass in the needle test, the safety performance is obviously inferior to the example, and cannot meet the application requirements. Therefore, by controlling H in the range of 5-10 mm, the battery monomer 10 can have good safety performance and high volumetric energy density.

[0191] From the comparative analysis of Examples 1, 9-11, it can be seen that in the range of 500-800 mm 2 , the safety performance of the battery monomer 10 is improved, and in Example 11, S is too small, only 6 passes in the needle test, obviously inferior to other examples. Therefore, by controlling S in the range of 500-800 mm 2 , the battery monomer 10 can have good safety performance and high volumetric energy density.

[0192] The test methods of the physical and chemical parameters and performance parameters involved in the examples 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.

[0193] 1. Test method of material particle size distribution graph

[0194] Unless otherwise specified, the positive electrode active material particle size distribution parameters determined by the particle size distribution measurement value in the present application, such as Dv10, Dv50 or Dv90, are determined by 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.

[0195] Test equipment: particle size testing instrument.

[0196] 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.

[0197] Test: After the sample is poured into the sample tower, it is circulated to the test light 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%).

[0198] 2. Test method of element molar ratio

[0199] Test equipment: inductively coupled plasma emission spectrometer (ICP).

[0200] Test method: digestion: 1+1 aqua regia, digestion method: flat plate / acid chasing digestion / microwave digestion (high temperature and high pressure ~ 200℃). The elemental mass fraction of nickel, cobalt, manganese and doping elements is tested, and the molar mass is calculated by combining the molar mass of each element, and finally the molar ratio of nickel, cobalt and manganese is calculated.

[0201] 3. Test method of Dv10, Dv50, Dv90

[0202] Test equipment: particle size testing instrument.

[0203] 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.

[0204] Test: After the sample is poured into the sample tower, it is circulated to the test light path system with the solution. The particle size distribution characteristics of the particles can be obtained by receiving and measuring the energy distribution of the scattered light under the irradiation of the laser beam (light shielding degree: 8-12%).

[0205] Calculation: Calculate the particle size at the 10%, 50%, and 90% positions in the volume distribution curve from small to large, which is Dv10, Dv50, and Dv90.

[0206] 4. Test method of battery volume energy density

[0207] Charge and discharge 3 times in the range of 2.5-4.25V with a current density of 0.33C on the charge and discharge equipment, take the discharge energy Q of the 3rd cycle; measure the diameter d and height h of the battery 10, calculate the volume V of the wound electrode assembly 12 = π × (d / 2)2×h, and the energy density is Q / V (unit Wh / L).

[0208] 5. Test method of needle puncture test

[0209] A steel needle with a diameter of 3mm is used to pierce the largest surface of the battery to be tested 10 at a speed of 0.1mm / s until thermal runaway occurs. Observe whether the pressure relief mechanism is broken and whether the electrode terminal is ejected, and whether the shell is broken. Among them, a group of batteries can be tested, and a group includes 10 batteries 10, and the probability of the above-mentioned conditions occurring in the battery is observed. "1 / 10 pass" means that among the 10 batteries 10 to be tested, 1 does not have the conditions of pressure relief mechanism rupture, electrode terminal ejection, and shell rupture, that is, 1 battery 10 passes the test.

[0210] 6. Test method of capacity of battery

[0211] The capacity of the battery cell can be obtained by the charge-discharge machine test. Specifically, the battery cell is tested by charge-discharge at a current density of 0.33C in a voltage range of 2.5V-4.25V, and the discharge capacity of the third cycle is recorded as the actual capacity of the battery cell after 3 cycles.

[0212] The capacity of the battery cell obtained by the test has a certain deviation, which is about 5% floating.

[0213] 7. Test method of the area S defined by the pressure relief mechanism, the height h of the battery cell, and the distance H between the electrode assembly and the pressure relief mechanism

[0214] The battery cell is subjected to CT scanning, 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 × (R / 2) 2 . If the area defined by the pressure relief mechanism is irregular, the area can be calculated by fitting the irregular shape into a regular shape on the computer and then calculating the area of the regular shape.

[0215] 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 electrode assembly close to the pressure relief mechanism; 5 points are selected along the thickness direction of the end cover on the end of the negative electrode tab close to the end cover in the electrode assembly, which correspond to the 5 points selected on the pressure relief mechanism along the thickness direction of the end cover; the average distance between the 5 points selected on the pressure relief mechanism and the 5 points selected on the electrode assembly is calculated, and the average value is taken as the value of the gap H.

[0216] 8. Test method of the compaction density of the electrode tab

[0217] Take the electrode tab with an area of s1, measure its thickness h1 and weight m1; take an aluminum foil with the same area, whose thickness is h2 and weight is m2; the compaction density of the electrode tab = (m1-m2) / [s1×(h1-h2)], unit: g / cm 3 . The measurement deviation of the compaction density is within ±0.05 g / cm 3 .

[0218] Although the present application has been described with reference to preferred embodiments, various modifications can be made to the application without departing from the scope of the application. In particular, the technical features mentioned in the various embodiments can be combined in any way, provided that 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 provided with an opening; a wound electrode assembly arranged in the shell; an end cover covering the opening, the end cover comprising a pressure relief mechanism; a limiting portion is protruded from 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, the distance H between the wound electrode assembly and the pressure relief mechanism in the thickness direction of the end cover satisfies: H≥5mm; the wound electrode assembly comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material, the positive electrode active material comprises a lithium-containing transition metal oxide, in the lithium-containing transition metal oxide, the molar percentage n% of Ni element in transition metal elements satisfies: 80%≤n%<100%; the volume particle size distribution of the lithium-containing transition metal oxide comprises two peaks, the two particle sizes corresponding to the two peaks are D1 and D2 respectively, 2μm≤D1≤4μm; 10μm≤D2≤13.5μm.

2. The battery cell of claim 1, wherein, 5mm≤H≤10mm.

3. The battery cell according to claim 1 or 2, characterized in that, The capacity C of the battery cell satisfies: 30Ah≤C≤40Ah.

4. The battery cell of any one of claims 1-3, wherein, The capacity C of the battery cell and the distance H between the wound electrode assembly and the pressure relief mechanism satisfy: C / 6≤H≤C / 4.

5. The battery cell of any one of claims 1-4, wherein, The area S of the region defined by the pressure relief mechanism satisfies: 500mm 2 ≤ S ≤ 800mm 2 .

6. The battery cell of any one of claims 1-5, wherein, The capacity C of the battery cell and the area S of the region defined by the pressure relief mechanism satisfy: 12 mm 2 / Ah≤ S / C≤ 20 mm 2 / Ah.

7. The battery cell of any one of claims 1-6, wherein, 5mm≤H≤8mm.

8. The battery cell of any one of claims 1-7, wherein, The wound electrode assembly further comprises a negative electrode sheet and a separator, at the winding starting end of the wound electrode assembly, the negative electrode sheet is wound to form a center hole.

9. The battery cell of claim 8, wherein, The negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprises a silicon-containing material, the silicon-containing material comprises at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, silicon-containing alloy or silicon-oxygen-carbon composite material; and At the winding starting end of the wound electrode assembly, the difference L1-L2 between the length L1 of the negative electrode sheet and the length L2 of the positive electrode sheet satisfies: 30mm≤L1-L2≤60mm.

10. The battery cell according to claim 8 or 9, characterized in that The diameter d of the center hole satisfies: nπd≥L1-L2, wherein π is a circular constant, n is an integer and n≥2.

11. The battery cell of any one of claims 1-10, wherein, The D1 and D2 satisfy: 8μm≤D2-D1≤11.5μm.

12. The battery cell of any one of claims 1-11, wherein, The half-peak width W1 of the peak corresponding to D1 satisfies: 1.4μm≤W1≤2.0μm; the half-peak width W2 of the peak corresponding to D2 satisfies: 8μm≤W2≤12μm.

13. The battery cell of any one of claims 1-12, 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.

14. The battery cell of any one of claims 1-13, wherein, The compacted density p of the positive electrode sheet satisfies: 3.55 g / cm 3 ≤ p ≤ 3.67 g / cm 3 .

15. The battery cell of any one of claims 1-14, wherein, The positive electrode active material further comprises a doping element, the doping element comprises at least one of Zr, Sr, Al, Co, B, W, Nb, Sb, P and F.

16. The battery cell of any one of claims 1-15, wherein, The end cover comprises an end cover body, the pressure relief mechanism is arranged on the side of the end cover body facing the wound electrode assembly.

17. The battery cell of claim 16, wherein, The end cover body is provided with a score groove, the area defined by the score groove forms the pressure relief mechanism.

18. The battery cell of any one of claims 1-17, wherein, The battery cell further includes a current collecting member accommodated in the case; In a thickness direction of the end cap, the current collecting member is located between the wound electrode assembly and the end cap, and is electrically connected to the tab of the wound electrode assembly and the end cap.

19. The battery cell of any one of claims 1-18, wherein, The limiting portion is a protrusion structure or a roller groove structure.

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

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

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