Battery cell, battery apparatus and electric device

Abstract

Disclosed in the present application are a battery cell, a battery apparatus and an electric device. The battery cell comprises: a casing, wherein the casing comprises a first wall, and the casing has an accommodating cavity; an electrode terminal arranged on the first wall, the minimum cross-sectional area of the electrode terminal being S; and an electrode assembly, wherein the electrode assembly is arranged within the accommodating cavity, and the electrode assembly comprises a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the positive electrode film layer comprising a lithium-containing phosphate. The ratio of the volumetric energy density (VED) of the battery cell to S ranges from 2Wh / L / mm2 to 10Wh / L / mm2. Thus, during fast charging, heat generation of the electrode terminal can be reduced, thereby obtaining a battery cell having excellent fast charging performance and prolonged cycle life.

Description

Battery cells, battery devices and electrical equipment Technical Field

[0001] This application relates to the field of batteries, specifically to battery cells, battery devices, and electrical equipment. Background Technology

[0002] Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. Charging batteries at high rates generates significant heat, which can negatively impact their long-term performance. Summary of the Invention

[0003] A first aspect of this application provides a battery cell, the battery cell comprising a housing, the housing including a first wall and having a receiving cavity; an electrode terminal disposed on the first wall, the electrode terminal having a minimum cross-sectional area of ​​S; and an electrode assembly disposed within the receiving cavity, the electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including lithium phosphate, wherein the ratio of the volumetric energy density VED of the battery cell to S is 2Wh / L / mm². 2 Up to 10Wh / L / mm 2 Therefore, by keeping the ratio of volumetric energy density (VED) to S of the battery cell within the above range, when charging the battery cell at a high rate, heat generation at the electrode terminals can be reduced, resulting in lithium phosphate battery cells with excellent fast-charging performance and cycle life.

[0004] According to some embodiments of this application, the ratio of the volumetric energy density VED of the battery cell to S is 2Wh / L / mm². 2 Up to 3.5Wh / L / mm 2 This further reduces heat generation at the electrode terminals, resulting in battery cells with excellent fast-charging performance and cycle life.

[0005] According to some embodiments of this application, the volumetric energy density (VED) of the battery cell satisfies: 350Wh / L ≤ VED ≤ 430Wh / L. This increases the capacity of the battery cell.

[0006] According to some embodiments of this application, the minimum cross-sectional area S of the electrode terminal satisfies: 40 mm. 2 ≤S≤800mm 2 This improves the current-carrying capacity of the electrode terminals, reduces resistance, and lowers the heat generated at the electrode terminals.

[0007] According to some embodiments of this application, the battery cell includes a cover plate assembly forming the first wall. The cover plate assembly includes a cover plate and the electrode terminals. A through hole is provided on the cover plate. The electrode terminals include a terminal body, a first limiting portion, and a second limiting portion. The terminal body passes through the through hole and connects the first limiting portion and the second limiting portion. The first limiting portion is located on the side of the cover plate facing the receiving cavity, and the second limiting portion is located on the side of the cover plate away from the receiving cavity. This reduces the risk of the electrode terminals detaching from the through hole, allowing the battery cell to normally input or output electrical energy, and improving the service life of the battery cell.

[0008] According to some embodiments of this application, the cross-sectional area of ​​the second limiting portion is 300 mm. 2 Up to 700mm 2 This improves the current-carrying capacity of the electrode terminals and reduces heat generation at the electrode terminals.

[0009] According to some embodiments of this application, the cross-sectional area of ​​the first limiting portion is 200 mm. 2 Up to 800mm 2 This improves the current-carrying capacity of the electrode terminals and reduces heat generation at the electrode terminals.

[0010] According to some embodiments of this application, the cross-section of the terminal body is a rounded rectangle. This improves the current-carrying capacity of the electrode terminals while maintaining a relatively small cover area.

[0011] According to some embodiments of this application, the cross-sectional area of ​​the terminal body is 40 mm². 2 Up to 240mm 2 This improves the current-carrying capacity of the electrode terminals and reduces heat generation at the electrode terminals.

[0012] According to some embodiments of this application, the cover plate assembly is disposed at both ends of the housing, and each cover plate assembly includes at least two electrode terminals. This reduces the resistance of the individual battery cells and increases their current-carrying capacity.

[0013] According to some embodiments of this application, the cover plate assembly is disposed at both ends of the housing, and each cover plate assembly includes at least two electrode terminals with opposite polarities. This shortens the current path and reduces the internal resistance of the battery cell.

[0014] According to some embodiments of this application, the cover plate assembly is disposed at both ends of the housing, and each cover plate assembly includes at least two electrode terminals with opposite polarities. Along the length of the battery cell, electrode terminals of the same polarity on the two cover plate assemblies are staggered. Optionally, electrode terminals of the same polarity are diagonally arranged along the length of the battery cell. This reduces wiring during battery assembly and lowers assembly difficulty.

[0015] According to some embodiments of this application, the electrode assembly further includes a negative electrode sheet, and the positive and negative electrode sheets are stacked, with a positive electrode tab on each layer of the positive electrode sheet and a negative electrode tab on each layer of the negative electrode sheet. This improves current transmission efficiency, reduces the resistance of individual battery cells, and enhances the rate performance of the battery.

[0016] According to some embodiments of this application, the positive electrode tab extends along the length direction or the width direction of the positive electrode sheet; and / or the negative electrode tab extends along the length direction or the width direction of the negative electrode sheet. This improves current transmission efficiency, reduces the resistance of individual battery cells, and enhances the rate performance of the battery.

[0017] According to some embodiments of this application, the coating length of the positive electrode film is 200mm-700mm along the length direction of the positive electrode sheet. This increases the energy density of the battery cell.

[0018] According to some embodiments of this application, the compaction density of the positive electrode film layer corresponding to the battery cell at 100% SOC is 2.5 g / cm³. 3 -2.8g / cm 3 This increases the energy density of individual battery cells.

[0019] According to some embodiments of this application, the single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 -340mg / 1540.25mm 2 The option is 240mg / 1540.25mm. 2 -300mg / 1540.25mm 2 This increases the energy density of individual battery cells.

[0020] According to some embodiments of this application, the lithium phosphate has a charging capacity of 150mAh / g-170mAh / g at a 0.1C rate. This improves the energy density of the battery cell.

[0021] According to some embodiments of this application, the lithium-containing phosphate includes compounds represented by Formula I: Li x1A y1 Me a M b P 1-c X c Y z Formula I, where 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, P, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or two of O and F. This improves the safety performance and cycle life of the battery cell.

[0022] According to some embodiments of this application, the lithium-containing phosphate includes lithium iron phosphate material. This improves the safety performance and cycle life of the battery cell.

[0023] According to some embodiments of this application, the lithium-containing phosphate is in particulate form, and the volume average particle size Dv50 of the lithium-containing phosphate is 1μm-2μm. This shortens the migration path of lithium ions in the solid phase, reduces the polarization of the battery cell, and decreases the heat generation of the battery cell.

[0024] According to some embodiments of this application, the volumetric particle size Dv10 of the lithium phosphate is 0.4 μm-0.7 μm. This shortens the migration path of lithium ions in the solid phase, reduces the polarization of the battery cell, and decreases the heat generation of the battery cell.

[0025] According to some embodiments of this application, the lithium-containing phosphate comprises secondary particles, wherein the average particle size of the primary particles in the secondary particles is 200 nm-500 nm. This shortens the migration path of lithium ions in the solid phase, reduces the polarization of the battery cell, and decreases the heat generation of the battery cell.

[0026] According to some embodiments of this application, the positive electrode film layer further includes a lithium replenishing agent, the mass percentage of which is 0.1%-5% based on the total mass of the positive electrode film layer. This compensates for lithium loss during the formation of the electrolyte interface film (SEI film) at the negative electrode, thereby improving the battery's initial efficiency.

[0027] According to some embodiments of this application, the lithium replenishing agent includes one or more of lithium nickel cobalt manganese oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium nickel oxide, and lithium ferrite. This compensates for lithium loss during SEI film formation at the negative electrode, improving the battery's initial efficiency.

[0028] According to some embodiments of this application, the positive electrode film layer further includes a conductive agent, and the mass percentage of the conductive agent is 0.1%-1% based on the total mass of the positive electrode film layer. This improves the electronic conductivity of the positive electrode film layer.

[0029] According to some embodiments of this application, the conductive agent comprises carbon nanotubes. This increases the contact area between the conductive agent and the positive electrode active material, thereby improving the electronic conductivity of the positive electrode film.

[0030] According to some embodiments of this application, the thickness of the positive electrode current collector is 10μm-16μm. This improves the current-carrying capacity of the positive electrode current collector and increases the energy density of the battery cell.

[0031] According to some embodiments of this application, the electrode assembly further includes a negative electrode sheet, the negative electrode sheet including a negative current collector, and a negative electrode film layer disposed on at least one side of the negative current collector. The compaction density of the negative electrode film layer corresponding to 100% SOC of the battery cell is 1.15 g / cm³. 3 -1.36g / cm 3 The option is 1.25g / cm³. 3 -1.36g / cm 3 This increases the energy density of individual battery cells.

[0032] According to some embodiments of this application, the electrode assembly further includes a negative electrode sheet, the negative electrode sheet including a negative current collector, and a negative electrode film layer disposed on at least one side of the negative current collector, the single-sided coating weight of the negative electrode film layer being 90 mg / 1540.25 mm. 2 -170mg / 1540.25mm 2 The option is 110mg / 1540.25mm. 2 -150mg / 1540.25mm 2 This increases the energy density of individual battery cells.

[0033] According to some embodiments of this application, the negative electrode film layer includes a negative electrode active material, and the specific capacity of the negative electrode active material at a 0.1C rate is 350mAh / g-480mAh / g. This improves the energy density of the battery cell.

[0034] According to some embodiments of this application, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode is disposed on at least one side of the negative electrode current collector, and the second negative electrode film layer is disposed on the side of the first negative electrode film layer opposite to the negative electrode current collector. The first negative electrode film layer includes first graphite particles, and the second negative electrode film layer includes second graphite particles. The volume average particle size of the first graphite particles is larger than that of the second graphite particles. Therefore, the smaller volume average particle size of the second graphite particles can shorten the solid-phase transport path of lithium ions and improve the fast-charging performance of the battery cell.

[0035] According to some embodiments of this application, the first graphite particles comprise natural graphite. This increases the compaction density of the negative electrode sheet.

[0036] According to some embodiments of this application, the volume average particle size Dv50 of the first graphite particle is 7 μm-18.5 μm; and / or the volume average particle size Dv50 of the second graphite particle is 7 μm-14.3 μm. Therefore, the smaller volume average particle size of the second graphite particle shortens the solid-phase transport path of lithium ions and improves the fast-charging performance of the battery cell.

[0037] According to some embodiments of this application, the first negative electrode film layer and / or the second negative electrode film layer comprise silicon-based materials, and the mass percentage of silicon element is 0.3%-10% based on the total mass of the negative electrode film layers. This increases the capacity of the negative electrode active material and improves the energy density of the battery cell.

[0038] According to some embodiments of this application, the thickness of the negative electrode current collector is 4μm-8.5μm. This improves the current-carrying capacity of the negative electrode current collector and increases the energy density of the battery cell.

[0039] According to some embodiments of this application, the battery cell further includes an electrolyte comprising a chain-like carboxylic acid ester. Based on the total mass of the electrolyte, the mass percentage of the chain-like carboxylic acid ester is 5%-60%, optionally 8%-30%. This reduces the viscosity of the electrolyte, lowers the internal resistance of the battery cell, and improves the fast-charging performance of the battery cell.

[0040] According to some embodiments of this application, the battery cell is configured to charge from 10% SOC to 80% SOC in 5-10.5 minutes, optionally 7-10 minutes. This improves the fast-charging performance of the battery cell.

[0041] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0042] A third aspect of this application provides an electrical device, including a battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application, wherein the battery cell or the battery device is used to provide electrical energy.

[0043] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0044] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0045] Figure 1 is a schematic diagram of the structure of the housing according to an embodiment of this application.

[0046] Figure 2 is a structural schematic diagram of a cover plate assembly according to an embodiment of this application.

[0047] Figure 3 is an exploded view of the cover plate assembly in Figure 2.

[0048] Figure 4 is a structural schematic diagram of the cover plate assembly in Figure 2 from another perspective.

[0049] Figure 5 is a cross-sectional schematic diagram of the cover plate assembly in Figure 4 along the AA' direction.

[0050] Figure 6 is a structural schematic diagram of another cover plate assembly of this application.

[0051] Figure 7 is an exploded view of the cover plate assembly in Figure 6.

[0052] Figure 8 is a structural schematic diagram of the cover plate assembly in Figure 6 from another perspective.

[0053] Figure 9 is a cross-sectional schematic diagram of the cover plate assembly in Figure 8 along the BB' direction.

[0054] Figure 10 is a schematic diagram of the structure of a battery cell according to one embodiment of this application.

[0055] Figure 11 is a schematic diagram of the structure of a cover plate assembly of a battery cell in Figure 10.

[0056] Figure 12 is an exploded view of the cover plate assembly in Figure 11.

[0057] Figure 13 is a structural schematic diagram of the cover plate assembly in Figure 11 from another perspective.

[0058] Figure 14 is a cross-sectional schematic diagram of the cover plate assembly in Figure 13 along the CC' direction.

[0059] Figure 15 is a structural schematic diagram of another cover plate assembly of the battery cell in Figure 10.

[0060] Figure 16 is an exploded view of the cover plate assembly in Figure 15.

[0061] Figure 17 is a structural schematic diagram of the cover plate assembly in Figure 15 from another perspective.

[0062] Figure 18 is a cross-sectional schematic diagram of the cover plate assembly in Figure 17 along the DD' direction.

[0063] Figure 19 is a schematic diagram of the structure of an electrode assembly according to an embodiment of this application.

[0064] Figure 20 is a schematic diagram of the structure of an electrode assembly according to another embodiment of this application.

[0065] Figure 21 is a schematic diagram of the structure of an electrode assembly according to an embodiment of this application.

[0066] Figure 22 is a schematic diagram of the structure of the positive electrode sheet according to an embodiment of this application.

[0067] Figure 23 is a schematic diagram of the structure of the positive electrode sheet according to another embodiment of this application.

[0068] Figure 24 is a schematic diagram of the structure of the positive electrode sheet according to another embodiment of this application.

[0069] Figure 25 is a schematic diagram of the structure of the positive electrode sheet according to another embodiment of this application.

[0070] Figure 26 is a schematic diagram of the negative electrode sheet according to an embodiment of this application.

[0071] Figure 27 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0072] Figure 28 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0073] Figure 29 is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0074] Figure 30 is a schematic diagram of the structure of the positive electrode sheet according to an embodiment of this application.

[0075] Figure 31 is a SEM image of the positive electrode active material according to an embodiment of this application.

[0076] Figure 32 is a SEM image of the positive electrode film layer according to an embodiment of this application.

[0077] Figure 33 is a schematic diagram of the negative electrode sheet according to an embodiment of this application.

[0078] Figure 34 is a schematic diagram of an electrical device according to this application.

[0079] Explanation of reference numerals in the attached drawings: 1. Battery cell; 11. Housing; 12. Cover assembly; 1213. First cover; 1214. Second cover; 1210. Through hole; 1211. Liquid filling hole; 1212. Pressure relief mechanism; 1221 Electrode terminal; 1222 First limiting part; 1223 Second limiting part; 1224 Terminal body; 1225 Riveting block; 123 First insulating component; 1230 Through hole; 124 Sealing component; 125 Positioning component; 126 Second insulating component; 10 Electrode assembly; 2 Positive electrode sheet; 21 Positive current collector; 22 Positive film layer; 221 Lithium phosphate; 222 Lithium replenishing agent; 23 Positive electrode tab; 231 First positive electrode tab; 232 Second positive electrode tab; 3 Negative electrode sheet; 30 Negative current collector; 31 Negative film layer; 311 First negative film layer; 312 Second negative film layer; 32 Negative electrode tab; 321 First negative electrode tab; 322 Second negative electrode tab; 4 Separator membrane. Detailed Implementation

[0080] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0081] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0082] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0083] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0084] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0085] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing. However, current battery cells cannot meet the demands for fast charging and long cycle life.

[0086] This application aims to develop lithium phosphate-based battery cells that combine high energy density, excellent fast-charging performance, and long cycle life. When charging a battery cell at the same charging rate, a higher volumetric energy density results in more heat generation. This heat must be dissipated through the electrode terminals on the cover assembly; that is, higher volumetric energy density places higher demands on the current-carrying capacity of the electrode terminals. The battery cell proposed in this application, when the positive electrode active material is a lithium phosphate-based material, achieves this by maintaining the ratio of the volumetric energy density (VED) to the minimum cross-sectional area (S) of the electrode terminals within a certain range within the capacity range of lithium phosphate-based materials. This allows the battery cell to achieve high energy density while reducing heat generation at the electrode terminals, lowering the internal resistance of the battery cell, and improving cycle performance when charged with a larger current. If the ratio of VED to S is too small, the current-carrying capacity of the electrode terminals is poor, resulting in more heat generation at the electrode terminals during high-rate charging, which reduces the cycle life of the battery cell. Conversely, if the ratio of VED to S is too large, the volumetric energy density of the battery cell is low, which reduces the capacity of the battery cell.

[0087] The battery cells proposed in this application can be used in electrical devices that use the battery cells as a power source or in various energy storage systems that use the battery cells as energy storage elements. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0088] This application provides a battery cell, the battery cell including a first wall, the housing having a receiving cavity; an electrode terminal disposed on the first wall, the minimum cross-sectional area of ​​the electrode terminal being S; and an electrode assembly disposed within the receiving cavity, the electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including lithium phosphate; wherein the ratio of the volumetric energy density VED of the battery cell to S is 2Wh / L / mm². 2 Up to 10Wh / L / mm2 .

[0089] In this application, the minimum cross-sectional area of ​​the electrode terminal refers to the minimum cross-sectional area of ​​the electrode terminal along the direction perpendicular to the current flow.

[0090] In this application, the test method for the volumetric energy density of a single battery cell is as follows: the battery cell is placed at room temperature and charged to 3.65V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 3.65V, and left to stand for 30 minutes; it is then discharged to 2.0V with a constant current of 0.33C, and the discharge capacity A0 at this time is recorded in Ah. The discharge plateau voltage is calculated in V. The volume of the battery cell refers to the external volume of the casing. The length, width, and thickness of the casing are measured using calipers (excluding the dimensions of the electrode terminals extending out of the casing), and the volume of the single battery cell V0 is calculated in L. The volumetric energy density of the battery cell VED = (A0 × discharge plateau voltage) / V0, in Wh / L.

[0091] In some implementations, the volumetric energy density of a single battery cell can be adjusted in the following optional ways:

[0092] From the perspective of active materials, high-specific-capacity positive and negative electrode active materials can be used. For example, for positive electrode active materials, lithium phosphate materials with higher specific capacity can be used, such as physically mixing positive electrode active materials with higher specific capacity, such as ternary materials, to improve energy density; for negative electrode active materials, graphite with higher specific capacity can be used, such as physically mixing negative electrode active materials with higher specific capacity, such as silicon-based materials, etc.

[0093] From the perspective of electrolytes, reducing the amount of electrolyte injected, or using electrolytes that support higher energy densities, etc.

[0094] From the perspective of electrode design, the compaction density and coating weight of the positive or negative electrode can be adjusted, or the thickness of the positive or negative current collector can be adjusted.

[0095] Regarding the separator membrane, its thickness can be adjusted, etc.

[0096] In terms of structural design, the first step is to reduce the proportion of inactive materials such as battery components. For example, making the battery casing thinner while ensuring its safety and mechanical performance allows more active materials to be accommodated in the same space, thus increasing energy density. This can be achieved by adjusting the space ratio of electrode components within the casing cavity.

[0097] It should be noted that the first wall may be part of the shell, or the first wall may be a separate structural component.

[0098] Referring to Figures 1-5, the battery cell 1 includes a housing 11 and a cover assembly 12. The cover assembly 12 forms the first wall and is disposed at at least one end of the housing 11. The housing 11 and the cover assembly 12 define a receiving cavity. The cover assembly 12 includes a cover plate and an electrode terminal 1221, wherein the minimum cross-sectional area of ​​the electrode terminal 1221 is S. An electrode assembly is disposed within the receiving cavity. The electrode assembly includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes lithium phosphate. The ratio of the volumetric energy density VED of the battery cell 1 to S is 2Wh / L / mm². 2 Up to 10Wh / L / mm 2 Therefore, by keeping the ratio of the volumetric energy density VED to S of the battery cell 1 within the above range, the heat generated at the electrode terminals 1221 is reduced during fast charging, thereby obtaining a battery cell 1 with good fast charging performance and cycle life.

[0099] When the cover plate assembly forms the first wall, the minimum cross-sectional area of ​​the electrode terminal refers to the minimum cross-sectional area of ​​the electrode terminal along the direction perpendicular to the current flow direction, which is parallel to the thickness direction of the cover plate.

[0100] Specifically, the cover plate assembly 12 may be disposed at at least one end of the housing 11 along its length direction, or the cover plate assembly 12 may be disposed at at least one end of the housing 11 along its width direction.

[0101] As an example, referring to Figure 1, the cover assembly 12 can be disposed at both ends of the housing 11 along its length direction; or the cover assembly 12 can be disposed at both ends of the housing 11 along its width direction. Specifically, when the housing 11 has openings at both ends along its length direction, the cover assembly 12 can be disposed at both ends of the housing 11 along its length direction and adapted to cover the openings respectively; when the housing 11 has openings at both ends along its width direction, the cover assembly 12 can be disposed at both ends of the housing 11 along its width direction and adapted to cover the openings respectively, so as to isolate the internal environment of the battery cell from the external environment. The shape of the cover assembly 12 can be adapted to the shape of the housing 11 to fit the housing 11.

[0102] In some embodiments, the cover plate assembly 12 may be disposed at both ends of the housing 11 along its length, that is, the cover plate assembly 12 may be disposed on the smaller side of the housing 11, thereby saving space of the battery cell along the width direction, thereby accommodating wider electrode sheets and improving the energy density of the battery cell.

[0103] In some embodiments, the housing 11 is formed by bending and then welding, and the weld marks are integrated on the smaller side of the housing 11 extending along the length direction, which helps to reduce the problem of cracking in the weld area caused by the expansion of the battery cells along the thickness direction and improves the reliability of the housing 11.

[0104] Referring to Figures 2-5, the cover plate assembly 12 includes a first cover plate 1213 and an electrode terminal 1221.

[0105] In some embodiments, referring to the disassembled schematic diagram of the cover plate assembly 12 in FIG3, the cover plate assembly 12 includes a first cover plate 1213, an electrode terminal 1221, a first insulating member 123, a sealing member 124, a second insulating member 126, a riveting block 1225, and a positioning member 125, and is assembled into the cover plate assembly 12 shown in FIG2.

[0106] In some embodiments, Figure 5 is a cross-sectional schematic diagram of the cover plate assembly in Figure 4 along the AA' direction. Referring to Figures 5 and 3, the first cover plate 1213 has a through hole 1210, and the electrode terminal 1221 passes through the first cover plate 1213. A first insulating member 123 is provided between the first cover plate 1213 and the electrode terminal 1221. This assembly method serves to isolate the electrical connection components inside the housing 11 from the first cover plate 1213, and simultaneously ensures that the electrode terminal 1221 is insulated from the first cover plate 1213 to reduce the risk of short circuits. The first insulating member 123 has a through hole 1230, and the electrode terminal 1221 passes sequentially through the through hole 1230 and the through hole 1210. A sealing member 124 for insulation and sealing is provided between the through hole 1210 and the electrode terminal 1221. The sealing member 124 has an opening so that the electrode terminal 1221 can pass through. A second insulating member 126 and a riveting block 1225 are provided on the side of the first cover plate 1213 away from the electrode assembly. The second insulating member 126 and the riveting block 1225 also have openings. The electrode terminal 1221 passes through the openings of the second insulating member 126 and the riveting block 1225 in sequence. The second insulating member 126 is used to insulate the electrode terminal 1221 from the first cover plate 1213, and the riveting block 1225 is used to fix the electrode terminal 1221 to the first cover plate 1213.

[0107] In some embodiments, referring to FIG3, the cover plate assembly 12 further includes positioning elements 125, including at least two positioning elements 125, to prevent the electrode terminals 1221 from deflecting and to improve the stress strength of the electrode terminals 1221.

[0108] In some embodiments, referring to FIG4, the cover assembly includes an injection hole 1211 for injecting electrolyte into the receiving cavity of the housing 11.

[0109] Referring to Figures 6-9, the cover plate assembly 12 includes a second cover plate 1214 and an electrode terminal 1221.

[0110] In some embodiments, referring to the disassembled schematic diagram of the cover plate assembly 12 in FIG7, the cover plate assembly 12 includes a second cover plate 1214, an electrode terminal 1221, a first insulating member 123, a sealing member 124, a second insulating member 126, a riveting block 1225, and a positioning member 125, and is assembled into the cover plate assembly 12 shown in FIG6.

[0111] In some embodiments, Figure 9 is a cross-sectional schematic diagram of the cover plate assembly in Figure 8 along the BB' direction. Referring to Figures 7 and 9, the second cover plate 1214 has a through hole 1210, through which the electrode terminal 1221 passes. A first insulating member 123 is provided between the second cover plate 1214 and the electrode terminal 1221. This assembly method serves to isolate the electrical connection components within the housing 11 from the second cover plate 1214, and simultaneously ensures that the electrode terminal 1221 is insulated from the second cover plate 1214 to reduce the risk of short circuits. The first insulating member 123 has a through hole 1230, through which the electrode terminal 1221 sequentially passes. A sealing member 124 for insulation and sealing is provided between the through hole 1210 and the electrode terminal 1221. The sealing member 124 has an opening so that the electrode terminal 1221 can pass through. A second insulating member 126 and a riveting block 1225 are provided on the side of the second cover plate 1214 away from the electrode assembly. The second insulating member 126 and the riveting block 1225 also have openings. The electrode terminal 1221 passes through the openings of the second insulating member 126 and the riveting block 1225 in sequence. The second insulating member 126 is used to insulate the electrode terminal 1221 and the second cover plate 1214. The riveting block 1225 is used to fix the electrode terminal 1221 to the second cover plate 1214.

[0112] In some embodiments, referring to FIG7, the cover plate assembly 12 further includes positioning elements 125, including at least two positioning elements 125, to prevent the electrode terminals 1221 from deflecting and to improve the force strength of the electrode terminals 1221.

[0113] Referring to Figures 3 and 7, the electrode terminal 1221 includes a terminal body 1224, a first limiting portion 1222, and a second limiting portion 1223. The terminal body 1224 penetrates the through hole 1210 and connects the first limiting portion 1222 and the second limiting portion 1223. Since the first limiting portion 1222 and the second limiting portion 1223 serve a limiting function, their cross-sectional area is larger than that of the terminal body 1224. The cross-sectional area of ​​the terminal body 1224 is often small, thus becoming a bottleneck for overcurrent during charging and discharging. This application arrives at its technical solution by matching electrode terminals with appropriate overcurrent capabilities to battery cells of different energy densities.

[0114] In some embodiments, the cross-sectional area of ​​the first limiting portion 1222 is larger than the cross-sectional area of ​​the second limiting portion 1223, which can improve the current carrying capacity of the electrode terminal 1221 and improve the mechanical strength of the electrode terminal 1221.

[0115] As an example, the cover plate can be made of a material with a certain degree of hardness and strength (such as aluminum alloy), giving the cover plate higher strength and reducing deformation when the cover plate is compressed, thereby improving the safety performance of the battery cell. In some embodiments, a steel shell may be selected.

[0116] As an example, the cover assembly 12 and the housing 11 can be independent components.

[0117] As an example, the cover plate assembly 12 and the housing 11 can also be integrated. Specifically, at least one cover plate assembly 12 and housing 11 can form a common connection before the electrode assembly and other components are inserted into the housing. After the electrode assembly and other components are inserted into the housing 11, the cover plate assembly 12 can then cover the opening of the housing along its length direction (or width direction).

[0118] In this application, the first insulating element 123 and the second insulating element 126 may be made of plastic, rubber, etc., respectively.

[0119] As an example, referring to Figures 6 and 7, the cover assembly 12 also includes a pressure relief mechanism 1212. The pressure relief mechanism 1212 and the second cover 1214 are two separate components, which are molded separately and then assembled together. The pressure relief mechanism 1212 can be a component such as an explosion-proof plate, an explosion-proof valve, or a safety valve. The pressure relief mechanism 1212 can be installed on the second cover 1214 by means of bonding, welding, or other methods. When the internal pressure of the battery cell reaches a threshold, the pressure relief mechanism 1212 opens at least part of the pressure relief hole, and the internal pressure of the battery cell is released through the pressure relief hole to relieve the internal pressure of the battery cell.

[0120] As an example, the ratio of the volumetric energy density VED of the battery cell to S can be 2Wh / L / mm². 2 3Wh / L / mm 2 5Wh / L / mm 2 7Wh / L / mm 2 9Wh / L / mm 2 10Wh / L / mm 2 The values ​​can be any range of the aforementioned values. This further reduces heat generation at electrode terminals 1221, resulting in a battery cell with excellent fast-charging performance and cycle life. According to some specific embodiments of this application, the ratio of the volumetric energy density VED of the battery cell to S can be 2Wh / L / mm². 2 Up to 3.5Wh / L / mm 2 .

[0121] According to some embodiments of this application, the volumetric energy density (VED) of the battery cell satisfies: 350Wh / L ≤ VED ≤ 430Wh / L. For example, it can be 350Wh / L, 380Wh / L, 390Wh / L, 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, etc., or a range of any of the above values. This increases the capacity of the battery cell 1.

[0122] According to some embodiments of this application, the minimum cross-sectional area S of the electrode terminal satisfies: 40 mm. 2 ≤S≤800mm 2 For example, it can be 40mm 2 100mm 2 200mm 2 400mm 2 600mm 2 800mm 2 etc., or a range consisting of any of the above values.

[0123] According to some embodiments of this application, when the cross-sectional area of ​​the terminal body 1224 is smaller than the cross-sectional areas of the first limiting portion 1222 and the second limiting portion 1223, the minimum cross-sectional area S of the electrode terminal is equal to the cross-sectional area of ​​the terminal body 1224. This improves the overcurrent capacity of the electrode terminal 1221, reduces resistance, lowers the heat generation of the electrode terminal 1221, improves the fast-charging performance of the battery cell 1, and allows the electrode terminal to be more stably fixed to the cover plate via the first limiting portion 1222 and the second limiting portion 1223.

[0124] According to some embodiments of this application, referring to Figures 3 and 7, the electrode terminal 1221 includes a terminal body 1224, a first limiting portion 1222, and a second limiting portion 1223. The terminal body 1224 penetrates the through hole 1210 and connects the first limiting portion 1222 and the second limiting portion 1223. The first limiting portion 1222 is located on the side of the cover plate facing the receiving cavity, and the second limiting portion 1223 is located on the side of the cover plate away from the receiving cavity. Thus, the first limiting portion 1222 can restrict the electrode terminal 1221 from disengaging from the through hole 1210 in a direction away from the electrode assembly, and the second limiting portion 1223 can restrict the electrode terminal 1221 from disengaging from the through hole 1210 in a direction towards the electrode assembly, allowing the battery cell 1 to normally input or output electrical energy and extending the service life of the battery cell 1.

[0125] According to some embodiments of this application, the cross-sectional area of ​​the second limiting portion 1223 is 300 mm. 2 Up to 700mm 2 For example, it can be 300mm 2 400mm 2 500mm 2 600mm 2 700mm 2 The values ​​can be any range of the values ​​mentioned above. This increases the current-carrying capacity of electrode terminal 1221 and reduces the heat generated at electrode terminal 1221.

[0126] In this application, the cross-sectional area of ​​the second limiting part refers to the cross-sectional area of ​​the second limiting part along the direction perpendicular to the current flow direction, and the current flow direction is parallel to the thickness direction of the cover plate.

[0127] According to some embodiments of this application, the cross-sectional area of ​​the first limiting portion 1222 is 200 mm. 2 Up to 800mm 2 For example, it can be 200mm 2 400mm 2 500mm 2 600mm 2 700mm 2 800mm 2 The values ​​can be any range of the values ​​mentioned above. This increases the current-carrying capacity of electrode terminal 1221 and reduces the heat generated at electrode terminal 1221.

[0128] In this application, the cross-sectional area of ​​the first limiting part refers to the cross-sectional area of ​​the first limiting part along the direction perpendicular to the current flow direction, and the current flow direction is parallel to the thickness direction of the cover plate.

[0129] According to some embodiments of this application, referring to Figures 3 and 7, the cross-section of the terminal body 1224 is a rounded rectangle along the direction perpendicular to the current flow. This improves the current-carrying capacity of the electrode terminals while maintaining a relatively small cover area.

[0130] According to some embodiments of this application, the cross-sectional area of ​​the terminal body 1224 is 40 mm² along the direction perpendicular to the current flow. 2 Up to 240mm 2 For example, it can be 40mm 2 70mm 2 100mm 2 120mm 2 140mm 2 160mm 2 180mm 2 200mm 2 220mm 2 240mm 2 The values ​​can be any range of the values ​​mentioned above. This increases the current-carrying capacity of electrode terminal 1221 and reduces the heat generated at electrode terminal 1221.

[0131] In this application, when testing the cross-sectional area of ​​the terminal body 1224, it can be the area of ​​the cross-section at any position between the first limiting part 1222 and the second limiting part 1223 in a direction perpendicular to the current flow direction.

[0132] Specifically, when the cross-section of the terminal body is a rounded rectangle, the length and width of the cross-section and the radius of the four top feet 1 / 4 circle can be measured with a ruler. The area of ​​the cross-section is the sum of the area of ​​the rectangle and the area of ​​the circle, and is calculated using a general mathematical formula.

[0133] According to some embodiments of this application, the cover plate assembly 12 is disposed at both ends of the housing 11, and each cover plate assembly 12 includes at least two electrode terminals 1221. Specifically, the cover plate assembly 12 may be disposed at both ends in the length direction or at both ends in the width direction of the housing 11, and each cover plate assembly 12 includes two electrode terminals 1221 with the same polarity or opposite polarity. This reduces the resistance of the battery cell 1 and increases the current carrying capacity of the battery cell 1.

[0134] According to some embodiments of this application, the cover plate assembly is disposed at both ends of the housing, each cover plate assembly includes at least two electrode terminals with opposite polarities, and electrode terminals of the same polarity on the two cover plate assemblies are staggered along the length direction of the battery cell.

[0135] According to some embodiments of this application, the electrode terminals of the same polarity are arranged diagonally along the length of the battery cell.

[0136] Therefore, the temperature rise of individual battery cells can be reduced during charging, thereby reducing the impedance of individual battery cells.

[0137] As an example, referring to Figures 1 and 10, the cover plate assembly 12 is disposed at both ends of the housing 11 along its length, and each cover plate assembly 12 includes two electrode terminals 1221 with opposite polarities.

[0138] Referring to Figures 11-14, the cover plate assembly 12 includes a first cover plate 1213 and two electrode terminals 1221 with opposite polarities.

[0139] In some embodiments, referring to the disassembled schematic diagram of the cover plate assembly 12 in FIG12, the cover plate assembly includes a first cover plate 1213, two electrode terminals 1221, a first insulating member 123, two sealing members 124, two second insulating members 126, two riveting blocks 1225, and four positioning members 125, and is assembled into the cover plate assembly 12 shown in FIG11.

[0140] In some embodiments, Figure 14 is a cross-sectional view of Figure 13 along the CC' direction. Referring to Figures 12 and 14, it can be seen that the first cover plate 1213 has two through holes 1210, and both electrode terminals 1221 penetrate the first cover plate 1213. A first insulating member 123 is provided between the first cover plate 1213 and the two electrode terminals 1221. This assembly method serves to isolate the electrical connection components inside the housing 11 from the first cover plate 1213, and simultaneously ensures that the electrode terminals 1221 are insulated from the first cover plate 1213, reducing the risk of short circuits. The first insulating member 123 has two through holes 1230, and the two electrode terminals 1221 are respectively sequentially inserted through the through holes 1230 and the through holes 1210. 10. A sealing element 124 for insulation and sealing is provided between the through hole 1210 and the two electrode terminals 1221. The sealing element 124 has an opening so that the electrode terminals 1221 can pass through. Two second insulating elements 126 and two riveting blocks 1225 are provided on the side of the first cover plate 1213 away from the electrode assembly. The second insulating elements 126 and riveting blocks 1225 also have openings. The electrode terminals 1221 pass through the openings of the second insulating elements 126 and riveting blocks 1225 in sequence. The second insulating elements 126 are used to insulate the electrode terminals 1221 from the first cover plate 1213. The two riveting blocks 1225 fix the two electrode terminals 1221 to the first cover plate 1213 respectively. The first cover plate 1213 is provided with an injection hole 1211 for injecting electrolyte into the housing.

[0141] Referring to Figures 15-18, the cover plate assembly 12 includes a second cover plate 1214 and two electrode terminals 1221.

[0142] In some embodiments, referring to the disassembled schematic diagram of the cover plate assembly 12 in FIG16, the cover plate assembly 12 includes a second cover plate 1214, two electrode terminals 1221, a first insulating member 123, two sealing members 124, two second insulating members 126, two riveting blocks 1225, and four positioning members 125, and is assembled into the cover plate assembly 12 shown in FIG15.

[0143] In some embodiments, Figure 18 is a cross-sectional view of Figure 17 along the DD' direction. Referring to Figures 16 and 18, it can be seen that the second cover plate has two through holes 1210. The two electrode terminals 1221 respectively penetrate the second cover plate 1214. A first insulating member 123 is provided between the second cover plate 1214 and the electrode terminals 1221. This assembly method serves to isolate the electrical connection components within the housing 11 and the second cover plate 1214, while simultaneously insulating the electrode terminals 1221 from the second cover plate to reduce the risk of short circuits. The first insulating member 123 has two through holes 1230, and the two electrode terminals 1221 respectively pass through the corresponding through holes 1230 and the through holes. 1210, A sealing element 124 for insulation and sealing is provided between the through hole 1210 and the electrode terminal 1221. The sealing element 124 has an opening so that the electrode terminal 1221 can pass through. Two second insulating elements 126 and two riveting blocks 1225 are provided on the side of the second cover plate 1214 away from the electrode assembly. The second insulating element 126 also has an opening. The electrode terminal 1221 passes through the openings on the second insulating element 126 and the riveting blocks 1225 in sequence. The second insulating element 126 is used to insulate the electrode terminal 1221 from the second cover plate 1214, and the two riveting blocks 1225 are used to fix the two electrode terminals 1221 to the second cover plate 1214. A pressure relief mechanism 1212 is provided on the second cover plate 1214. When the internal pressure of the housing exceeds a threshold, the pressure relief mechanism 1212 can release the internal pressure of the housing.

[0144] Referring to Figure 19, the electrode assembly 10 includes four tabs. Two tabs extend from one end of the electrode assembly 10 along its length, namely a first positive tab 231 and a first negative tab 321. Two tabs extend from the other end of the electrode assembly 10 along its length, namely a second positive tab 232 and a second negative tab 322. The first positive tab 231 is electrically connected to the positive terminal on the first cover plate, the first negative tab 321 is electrically connected to the negative terminal on the first cover plate, the second positive tab 232 is electrically connected to the positive terminal on the second cover plate, and the second negative tab 322 is electrically connected to the negative terminal on the second cover plate. Thus, the electrode terminals with different polarities are diagonally arranged along the length of the battery cell, which can reduce the temperature rise of the battery cell during charging, thereby reducing the impedance of the battery cell.

[0145] Referring to Figure 20, the electrode assembly 10 includes four tabs. Two tabs extend from one end of the electrode assembly 10 along its length, namely a first positive tab 231 and a first negative tab 321. Two tabs extend from the other end of the electrode assembly 10 along its length, namely a second positive tab 232 and a second negative tab 322. The first positive tab 231 is electrically connected to the positive terminal on the first cover plate, the first negative tab 321 is electrically connected to the negative terminal on the first cover plate, the second positive tab 232 is electrically connected to the positive terminal on the second cover plate, and the second negative tab 322 is electrically connected to the negative terminal on the second cover plate. That is, the electrode terminals on each cover plate are electrode terminals of different polarities. There are a total of four electrode terminals on the battery cell. Therefore, while improving the current carrying capacity of the battery cell, it can reduce problems such as unreasonable wiring and excessively long wire harnesses caused by electrical connections between battery cells when assembling multiple battery cells into a battery pack, making assembly easier.

[0146] According to some embodiments of this application, referring to FIG21, the electrode assembly 10 further includes a negative electrode 3, the positive electrode 2 and the negative electrode 3 are stacked, a separator 4 is disposed between the positive electrode 2 and the negative electrode 3, a positive electrode tab is disposed on each layer of the positive electrode, and a negative electrode tab is disposed on each layer of the negative electrode. This improves current transmission efficiency, reduces the resistance of the battery cell 1, and improves the rate performance of the battery.

[0147] According to some embodiments of this application, the positive electrode tab extends along the length direction of the positive electrode sheet or along its width direction.

[0148] Referring to Figure 22, only one tab extends along the length of the positive electrode plate 2. Referring to Figure 23, positive electrode tabs extend from both ends along the length of the positive electrode plate 2.

[0149] Referring to Figure 24, the positive electrode tab 23 extends from one end along the width direction of the positive electrode plate 2. At this time, the dimension of the positive electrode tab 23 along the length direction of the positive electrode plate 2 can occupy 70%-90% of the total length of the positive electrode plate 2, thereby improving the current carrying capacity of the battery cell.

[0150] In some implementations, an electrical connection can be achieved between the positive electrode tab 23 and the electrode terminals on two cover plate assemblies arranged along the length of the battery cell by welding an L-shaped adapter piece to the positive electrode tab 23.

[0151] Referring to Figure 25, the positive electrode plate 2 has a first positive electrode tab 231 and a second positive electrode tab 232 respectively on both sides along its width direction.

[0152] According to some embodiments of this application, the negative electrode tab may extend from the negative electrode sheet along its length or its width. This improves current transmission efficiency, reduces the resistance of the battery cell 1, and enhances the rate performance of the battery cell.

[0153] Referring to Figure 26, the negative electrode tab 32 extends along the length of the negative electrode plate 3; referring to Figure 27, the negative electrode tabs extend along the length of the negative electrode plate 3 to form the first negative electrode tab 321 and the second negative electrode tab 322 respectively.

[0154] Referring to Figure 28, the negative electrode tab 32 extends along the width direction of the negative electrode sheet 3. At this time, the dimension of the negative electrode tab 23 along the length direction of the negative electrode sheet 3 can occupy 70%-90% of the total length of the negative electrode sheet 3, thereby improving the current carrying capacity of the battery cell.

[0155] Referring to Figure 29, the negative electrode sheet has a first negative electrode tab 321 and a second negative electrode tab 322 respectively on both sides along its width direction.

[0156] In some implementations, an electrical connection can be achieved between the electrode terminals on two cover plate assemblies arranged along the length of the battery cell by welding an L-shaped adapter piece onto the negative electrode tab 32.

[0157] In some embodiments, the battery cell of this application is a stacked battery, wherein the positive electrode and the negative electrode are stacked, and each layer of the positive electrode is provided with a positive electrode tab and each layer of the negative electrode is provided with a negative electrode tab.

[0158] According to some embodiments of this application, referring to FIG30, the positive electrode 2 includes a positive current collector 21, and a positive electrode film layer 22 is disposed on at least one side of the positive current collector. Along the length direction of the positive electrode 2, the coating length L of the positive electrode film layer is 200mm-700mm, for example, it can be 200mm, 300mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, etc., or can be any range of the above values. This improves the energy density of the battery cell 1.

[0159] In this application, the coating length of the positive electrode film can be measured using a ruler or meter stick, etc.

[0160] According to some embodiments of this application, the compaction density of the positive electrode film layer corresponding to the battery cell 1 at 100% SOC is 2.5 g / cm³. 3 -2.8g / cm 3 For example, it could be 2.5 g / cm³. 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 2.7g / cm 3 2.75g / cm 3 2.8g / cm 3 The values ​​can be any range of the above values. Therefore, when the compaction density of the positive electrode film is within the above range, the positive electrode sheet is more densely packed, which is beneficial to improving the energy density of the battery cell 1. Moreover, the contact resistance between particles is small, which can further reduce the internal resistance of the battery cell 1, reduce the heat generation of the battery cell 1, and improve the high-temperature performance of the battery cell 1.

[0161] This application provides a method for testing the compaction density of the positive electrode film: The battery cell 1 is disassembled to remove the positive electrode sheet, for example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), and cut into small circular pieces with an area of ​​S1. The weight of these pieces is recorded as M1, and their thickness H1 is measured. Then, the positive electrode film layer of the weighed positive electrode sheet is wiped off, the weight of the positive current collector is recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film = (M1-M0) / S1, the thickness of the positive electrode film = H1-H0, and the compaction density of the positive electrode film = single-sided coating weight of the positive electrode film / thickness of the positive electrode film.

[0162] According to some embodiments of this application, the single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2-340mg / 1540.25mm 2 For example, it could be 200mg / 1540.25mm 2 230mg / 1540.25mm 2 260mg / 1540.25mm 2 290mg / 1540.25mm 2 320mg / 1540.25mm 2 340mg / 1540.25mm 2 The values ​​can be any range of the aforementioned values. Therefore, by making the size of the positive electrode film layer 300mm-600mm, and simultaneously keeping the coating weight of the positive electrode film layer within the aforementioned range, the energy density of the battery cell 1 can be increased. According to some specific embodiments of this application, the single-sided coating weight of the positive electrode film layer can be 240mg / 1540.25mm. 2 -300mg / 1540.25mm 2 .

[0163] This application provides a method for testing the weight of the positive electrode film coating: The positive electrode sheet is disassembled from the battery cell 1. For example, a single-sided coated positive electrode sheet is taken (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), and it is cut into small circular pieces with an area of ​​S1. The weight of these pieces is recorded as M1. Then, the positive electrode film layer of the weighed positive electrode sheet is wiped off, and the weight of the positive current collector is measured and recorded as M0. The single-sided coating weight of the positive electrode film = (M1 - M0) / S1.

[0164] According to some embodiments of this application, the lithium phosphate has a charging capacity of 150 mAh / g-170 mAh / g at a 0.1C rate. This improves the energy density of the battery cell 1.

[0165] According to some embodiments of this application, the lithium-containing phosphate includes compounds represented by Formula I: Li x1 A y1 Me a M b P 1-c X c Y zFormula I, where 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, P, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or two of O and F. This improves the safety performance and cycle life of battery cell 1.

[0166] As an example, x1 can be 0.5, 0.7, 0.9, 1.1, 1.3, etc., or a range of any of the above values.

[0167] As an example, y1 can be 0, 0.3, 0.6, 0.9, 1.1, 1.3, etc., or it can be a range of any of the above values.

[0168] As an example, 'a' can be 0.9, 1.1, 1.3, 1.5, etc., or a range of any of the above values.

[0169] As an example, b can be 0, 0.2, 0.4, 0.5, etc., or a range of any of the above values.

[0170] As an example, c can be 0, 0.2, 0.4, 0.5, etc., or a range of any of the above values.

[0171] As an example, z can be 3, 3.5, 4, 4.5, 5, etc., or a range of any of the above values.

[0172] According to some embodiments of this application, the lithium-containing phosphate includes lithium iron phosphate material. This improves the safety and cycle performance of the battery cell 1.

[0173] According to some embodiments of this application, the lithium-containing phosphate is in particulate form, and the volume average particle size Dv50 of the lithium-containing phosphate is 1μm-2μm, for example, it can be 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, etc., or can be any range of the above values. Therefore, the olivine-structured lithium-containing phosphate has a smaller volume average particle size, which can shorten the migration path of lithium ions in the solid phase, reduce the polarization of battery cell 1, reduce heat generation, and improve the high-temperature performance of battery cell 1.

[0174] In this application, Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, for example, measured using a laser particle size analyzer (Malvern Master Size 2000) according to standard GB / T19077-2016 / ISO 13320:2009. The specific testing procedure is as follows: scrape off the positive electrode film powder, calcine it at high temperature in air, grind it into powder, sieve it, take an appropriate amount of the sample to be tested (ensuring a light-blocking degree of 8%-12% for the sample concentration), add deionized water, and simultaneously ultrasonically disperse it to ensure complete dispersion. Then, measure the sample according to the standard GB / T19077-2016 / ISO 13320:2009.

[0175] According to some embodiments of this application, the volumetric particle size Dv10 of the lithium phosphate is 0.4 μm-0.7 μm, for example, it can be 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, etc., or it can be any range of the above values. Therefore, the olivine-structured lithium phosphate has a smaller volumetric particle size Dv10, which can shorten the migration path of lithium ions in the solid phase, reduce the polarization of the battery cell 1, reduce heat generation, and improve the high-temperature performance of the battery cell 1.

[0176] In this application, Dv10 refers to the particle size corresponding to a cumulative volume distribution percentage of 10%, for example, measured using a laser particle size analyzer (Malvern Master Size 2000) according to standard GB / T19077-2016 / ISO 13320:2009. The specific testing procedure is as follows: scrape off the positive electrode film powder, calcine it at high temperature in air, grind it into powder, sieve it, take an appropriate amount of the sample to be tested (ensuring a light-blocking degree of 8%-12% for the sample concentration), add deionized water, and simultaneously ultrasonically disperse it to ensure complete dispersion. Then, measure the sample according to the standard GB / T19077-2016 / ISO 13320:2009.

[0177] According to some embodiments of this application, referring to FIG31, the lithium phosphate includes secondary particles, wherein the average particle size of the primary particles in the secondary particles is 200nm-500nm, for example, it can be 200nm, 300nm, 400nm, 500nm, etc., or can be any range of the above values. Therefore, the migration path of lithium ions in the solid phase can be shortened, the polarization of the battery cell can be reduced, heat generation can be reduced, and the high-temperature performance of battery cell 1 can be improved.

[0178] In this application, the method for testing the average particle size of primary particles is to use plasma to cut the positive electrode sheet along its thickness direction to obtain the cross-section of the positive electrode sheet, observe it under an appropriate magnification using a scanning electron microscope (SEM), randomly select at least 50 primary particles, and the average particle size of a single primary particle is calculated as (the longest diameter of a single particle + the shortest diameter of a single particle) / 2. The average value of the selected primary particles is then taken as the average particle size of the primary particles.

[0179] According to some embodiments of this application, referring to FIG32, the positive electrode film layer may include lithium phosphate 221 and lithium replenishing agent 222. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium replenishing agent 222 may be 0.1%-5%, for example, it may be 0.1%, 1%, 2%, 3%, 4%, 5%, etc., or it may be any range of the above values. Therefore, lithium ions can be replenished to the positive electrode film layer, compensating for the lithium ion loss caused by the formation of the SEI film, increasing the capacity of the battery cell 1, and increasing the energy density of the battery cell 1.

[0180] According to some embodiments of this application, the lithium replenishing agent may include one or more of lithium nickel cobalt manganese oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, lithium trilithium citrate, lithium nickel oxide, and lithium ferrite. This compensates for lithium loss during SEI film formation at the negative electrode, improving the battery's initial efficiency and energy density.

[0181] According to some embodiments of this application, the positive electrode film layer further includes a conductive agent. Based on the total mass of the positive electrode film layer, the mass percentage of the conductive agent can be 0.1%-1%, for example, it can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, etc., or it can be any range of the above values. This improves the electronic conductivity of the positive electrode film layer.

[0182] According to some embodiments of this application, the conductive agent includes carbon nanotubes. This increases the contact area between the conductive agent and the positive electrode active material, improves the electronic conductivity of the positive electrode film, reduces the impedance of the electrode, reduces heat generation, and thereby improves the high-temperature performance of the battery cell 1.

[0183] According to some embodiments of this application, the thickness of the positive current collector is 10μm-16μm, for example, it can be 10μm, 12μm, 14μm, 16μm, etc., or it can be any range of the above values. Therefore, the current-carrying capacity of the positive current collector is improved while reducing the space occupied inside the housing 11.

[0184] In this application, the thickness of the positive current collector can be detected using equipment and methods known in the art, such as measuring the thickness of aluminum foil using a micrometer.

[0185] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0186] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0187] According to some embodiments of this application, the electrode assembly further includes a negative electrode sheet, the negative electrode sheet includes a negative current collector, and a negative electrode film layer is disposed on at least one side of the negative current collector. The compaction density of the negative electrode film layer corresponding to 100% SOC of the battery cell can be 1.15 g / cm³. 3 -1.36g / cm 3 For example, it could be 1.15 g / cm³. 3 1.2g / cm 3 1.25g / cm 3 1.3g / cm 3 1.36 g / cm 3 etc., or a range of any of the above values. According to some specific embodiments of this application, the compaction density of the negative electrode film layer corresponding to the battery cell at 100% SOC can be 1.25 g / cm³. 3 -1.36g / cm 3 This increases the energy density of individual battery cells.

[0188] This application provides a method for testing the compaction density of a negative electrode film: The battery cell 1 is charged at a constant current of 1 / 3C to 3.8V, and then charged at a constant voltage of 3.8V to 0.05C. The negative electrode sheet is disassembled, for example, a single-sided coated negative electrode sheet (if it is a double-sided coated sheet, the negative electrode film layer on one side can be wiped off first), and cut into small circular pieces with an area of ​​S2. The weight of these pieces is recorded as M3, and their thickness H3 is measured. Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, the weight of the negative current collector is recorded as M2, and its thickness H2 is measured. The single-sided coating weight of the negative electrode film = (M3 - M2) / S2, the thickness of the negative electrode film = H3 - H2, and the compaction density of the negative electrode film = single-sided coating weight of the negative electrode film / thickness of the negative electrode film.

[0189] According to some embodiments of this application, the single-sided coating weight of the negative electrode film can be 90 mg / 1540.25 mm. 2 -170mg / 1540.25mm 2 For example, it could be 90mg / 1540.25mm 2 110mg / 1540.25mm 2 130mg / 1540.25mm 2 150mg / 1540.25mm 2 170mg / 1540.25mm 2 etc., or can be any range of the above values. According to some specific embodiments of this application, the single-sided coating weight of the negative electrode film layer can be 110mg / 1540.25mm. 2 -150mg / 1540.25mm 2 This increases the energy density of individual battery cells.

[0190] This application provides a method for testing the weight of the negative electrode film coating: The negative electrode sheet is disassembled from the battery cell, for example, a single-sided coated negative electrode sheet (if it is a double-sided coated sheet, the negative electrode film layer on one side can be wiped off first), and cut into small circular pieces with an area of ​​S2. The weight of these pieces is recorded as M3. Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, and the weight of the negative electrode current collector is measured and recorded as M2. The single-sided coating weight of the negative electrode film = (M3 - M2) / S2.

[0191] According to some embodiments of this application, the negative electrode film layer includes a negative electrode active material, and the specific capacity of the negative electrode active material at a 0.1C rate is 350mAh / g-480mAh / g, for example, it can be 350mAh / g, 370mAh / g, 390mAh / g, 410mAh / g, 430mAh / g, 450mAh / g, 480mAh / g, etc., or any range of the above values. This improves the energy density of the battery cell.

[0192] According to some embodiments of this application, referring to FIG33, the negative electrode film layer 31 includes a first negative electrode film layer 311 and a second negative electrode film layer 312. The first negative electrode film layer 311 is disposed on at least one side of the negative electrode current collector 30, and the second negative electrode film layer 312 is disposed on the side of the first negative electrode film layer 311 opposite to the negative electrode current collector 30. The first negative electrode film layer 311 includes first graphite particles, and the second negative electrode film layer 312 includes second graphite particles. The volume average particle size of the first graphite particles is larger than that of the second graphite particles. During fast charging, the overpotential of the second negative electrode film layer 312 is usually higher. By making the volume average particle size of the second graphite particles smaller, the solid-phase transport path of lithium ions can be shortened, the diffusion rate of lithium ions can be increased, the fast charging performance can be improved, and the lithium plating problem on the negative electrode surface can be mitigated.

[0193] According to some embodiments of this application, the first graphite particles comprise natural graphite. This increases the compaction density of the negative electrode sheet.

[0194] According to some embodiments of this application, the volume average particle size Dv50 of the first graphite particle is 7μm-18.5μm, for example, it can be 7μm, 11μm, 13μm, 15μm, 17μm, 18.5μm, etc., or it can be any range of the above values.

[0195] According to some embodiments of this application, the volume average particle size Dv50 of the second graphite particle is 7μm-14.3μm, for example, it can be 7μm, 9μm, 11μm, 13μm, 14.3μm, etc., or it can be any range of the above values. Therefore, the volume average particle size of the second graphite particle is relatively small, which can shorten the solid-phase transport path of lithium ions and improve the fast-charging performance of the battery cell 1.

[0196] According to some embodiments of this application, the first negative electrode film layer and the second negative electrode film layer each independently comprise silicon-based materials. Based on the total mass of the negative electrode film layers, the mass percentage of silicon can be 0.3%-10%, for example, 0.3%, 1%, 3%, 5%, 7%, 9%, 10%, etc., or any range of the above values. This increases the capacity of the negative electrode active material and improves the energy density of the battery cell 1.

[0197] In this application, the silicon content can be tested by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0198] According to some embodiments of this application, the thickness of the negative electrode current collector is 4μm-8.5μm, for example, it can be 4μm, 5μm, 6μm, 7μm, 8μm, 8.5μm, etc., or it can be any range of the above values. Therefore, the flow capacity of the negative electrode current collector is improved while reducing the space occupied inside the housing 11.

[0199] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0200] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0201] According to some embodiments of this application, the battery cell further includes an electrolyte comprising chain-like carboxylic acid esters. Based on the total mass of the electrolyte, the mass percentage of the chain-like carboxylic acid esters can be 5%-60%, for example, 5%, 10%, 20%, 30%, 40%, 50%, 60%, etc., or any range of the above values. By keeping the content of the chain-like carboxylic acid esters within the above range, on the one hand, the viscosity of the electrolyte can be reduced, the internal resistance of the battery cell can be reduced, the migration rate of lithium ions can be increased, and the fast-charging performance of the battery cell can be improved; on the other hand, the risk of gas generation of the electrolyte under high-temperature conditions can be reduced, and the high-temperature cycle life of the battery cell can be improved, thereby obtaining a battery cell with both high energy density, excellent fast-charging performance, and high-temperature cycle life. According to some specific embodiments of this application, the mass percentage of the chain-like carboxylic acid esters can be 8%-30%.

[0202] In this application, the method for testing the content of chain carboxylic acid esters is quantitative analysis of organic components by gas chromatography.

[0203] According to some embodiments of this application, the chain carboxylic acid ester may include compounds represented by Formula I:

[0204] Wherein, R1 includes one or more of hydrogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, and R2 includes one or more of C1-C5 alkyl groups and C1-C5 haloalkyl groups.

[0205] Therefore, when the mass percentage of the chain carboxylic acid esters shown in Formula I is 5%-60%, on the one hand, using the above-mentioned content of chain carboxylic acid esters can improve the wetting ability of the electrolyte in the electrode film layer, especially in longer battery cells, improve the wetting uniformity of the electrolyte along the length of the electrode, improve the electron transport capability of the active material, and also improve the lithium ion migration rate in the electrolyte, thereby improving the fast charging performance of the battery cell; on the other hand, excessively high content of carboxylic acid ester solvents can also increase gas generation inside the battery cell, which is not conducive to battery cycling at high temperatures. Therefore, an appropriate amount of carboxylic acid ester solvents can also reduce the risk of electrolyte gas generation under high temperature conditions and improve the high temperature cycle life of the battery.

[0206] According to some embodiments of this application, R1 includes one or more of hydrogen atoms, C1-C3 alkyl groups, and C1-C3 haloalkyl groups. For example, R1 may include one or more of hydrogen atoms, methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl groups.

[0207] According to some embodiments of this application, R2 includes one or more of C1-C3 alkyl and C1-C3 haloalkyl groups. For example, R2 can be one or more of methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl groups.

[0208] According to some embodiments of this application, the chain carboxylic acid ester may include One or more of them.

[0209] According to some embodiments of this application, the battery cell is configured to charge from 10% SOC to 80% SOC in a time of 5 min to 10.5 min, for example, 5 min, 7 min, 9 min, 10.5 min, or any range of the above values. This improves the fast-charging performance of the battery cell. According to some specific embodiments of this application, the battery cell is configured to charge from 10% SOC to 80% SOC in a time of 7 min to 10 min.

[0210] In some embodiments, the battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0211] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0212] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0213] A third aspect of this application provides an electrical device, including a battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application, wherein the battery cell or the battery device is used to provide electrical energy.

[0214] The electrical equipment may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0215] As for the electrical equipment, the battery device can be selected according to its usage requirements.

[0216] Figure 34 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0217] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0218] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0219] Example 1

[0220] 1. Positive electrode sheet

[0221] The positive electrode includes a positive current collector aluminum foil, with a positive electrode film layer on both surfaces. The coating length of the positive electrode film layer is 585 mm, and the coating weight of the positive electrode film layer on one side is 290 mg / 1540.25 mm. 2 At 100% SOC, the compacted density is 2.65 g / cm³. 3 Based on the total mass of the single-sided positive electrode film, the positive electrode film comprises 95% lithium iron phosphate material, 1.7% lithium iron phosphate supplementer, 1.1% carbon black conductive agent, and 2.2% polyvinylidene fluoride (PVDF) binder. The volumetric particle size Dv10 of the lithium iron phosphate material is 0.35 μm, the volume average particle size Dv50 is 1.2 μm, and the average particle size of the primary particles is 325 nm. The lithium iron phosphate surface has a carbon coating layer, and based on the total mass of the lithium iron phosphate positive electrode active material, the carbon coating layer accounts for 1.18% of the mass.

[0222] 2. Negative electrode plate

[0223] The negative electrode sheet includes a copper foil as a negative current collector. Negative electrode films are formed on both surfaces of the copper foil. These films consist of a first negative electrode film and a second negative electrode film. In the first negative electrode film, the mass ratio of artificial graphite conductive agent (carbon black), binder (styrene-butadiene rubber (SBR), and thickener (sodium carboxymethyl cellulose (CMC-Na)) is 96%:1.1%:1.4%:1.5%. The volume average particle size (Dv50) of the artificial graphite active material in the first negative electrode film is 15 μm. In the second negative electrode film, the mass ratio of artificial graphite, carbon black, SBR, and CMC-Na is 96%:1.1%:1.4%:1.5%. The volume average particle size (Dv50) of the artificial graphite active material in the second negative electrode film is 11 μm. The compaction density of the negative electrode film is 1.56 g / cm³. 3 The coating weight of the negative electrode film is 138 mg / 1540.25 mm. 2 .

[0224] 3. Electrolyte

[0225] The electrolyte comprises solvents, electrolyte salts, and additives. The solvents include ethyl acetate (EA), ethylene carbonate (EC), and dimethyl carbonate (DMC). The electrolyte salts include lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide (LiFSI). The additives include vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), and lithium difluorooxalate borate (LiDFOB). Based on the total mass of the electrolyte, EA accounts for 39%, EC 27.3%, DMC 11.7%, VC 5%, FEC 1%, ES 0.5%, LiDFOB 0.5%, lithium hexafluorophosphate 10.5%, and LiFSI 4.5%.

[0226] 4. Separating membrane

[0227] Polypropylene film, 12μm thick.

[0228] 5. Battery cell

[0229] The battery cell includes a casing, a cover plate assembly, an electrode assembly, and an electrolyte. The cover plate assemblies are located at both ends of the casing along its length. The structure of one cover plate assembly is shown in Figure 2, and the structure of the other cover plate assembly is shown in Figure 6. That is, one cover plate assembly includes a positive terminal and the other cover plate assembly includes a negative terminal. The electrode assembly and the electrolyte are disposed in the cavity formed by the casing and the cover plate assembly. The electrode assembly is a stacked electrode assembly, which is made by stacking the aforementioned positive electrode sheet, separator, and negative electrode sheet. Along the length of the electrode assembly, a positive electrode tab extends from one end and a negative electrode tab extends from the other end. The positive electrode tab is electrically connected to the positive terminal, and the negative electrode tab is electrically connected to the negative terminal.

[0230] The battery cell casing is 630mm long, 99.6mm wide, and 15.7mm thick, with a cross-sectional area of ​​400mm² for the first limiting portion. 2 The cross-sectional area of ​​the terminal body is 90mm². 2 The cross-sectional area of ​​the second limiting part is 172.86 mm. 2 .

[0231] Performance testing

[0232] 1. DCR

[0233] At 25℃, the battery cell is charged at a constant current of 0.33C to 3.8V, then charged at a constant voltage of 0.05C, rested for 30 minutes, and then discharged at a constant current of 0.33C to 2.0V. The discharge capacity at this point is A0 (Ah). After resting for 30 minutes, it is charged at a constant current of 0.33C to 3.8V, then charged at a constant voltage of 0.05C, and then discharged at a constant current of 0.33C to 0.5A0. The cell SOC is adjusted, and the cell is rested for 120 minutes. The voltage in the last second is recorded as V0 (V), and the current magnitude is 4A0 (A). The constant current discharge lasts for 30 seconds, and the discharge end voltage is V1 (V). The discharge rate (DCR) for 30 seconds is (V0-V1) / 4A0×1000 (mΩ).

[0234] 2. High-temperature cycle life

[0235] At an ambient temperature of 45℃, the battery cell is charged to 3.8V using Stepcharge, then charged at a constant voltage to 0.05C, left to rest for 30 minutes, and then discharged at a constant current of 0.5C to 2.5V, left to rest for 30 minutes. This constitutes one charge-discharge cycle. The above charge-discharge cycle is repeated until the capacity of the battery cell is 80% of its initial capacity. The number of charge-discharge cycles is the high-temperature cycle life of the battery cell.

[0236] The Stepcharge charging steps are as follows:

[0237] Charge from 0% SOC to 10% SOC at a constant current of 1C.

[0238] Charge from 10% SOC to 30% SOC at a constant current of 7.0C;

[0239] Charge from 30% SOC to 35% SOC at a constant current of 6.2C;

[0240] Charge from 35% SOC to 40% SOC at a constant current of 5.7C;

[0241] Charge from 40% SOC to 45% SOC at a constant current of 5.2C;

[0242] Charge from 45% SOC to 50% SOC at a constant current of 4.8C;

[0243] Charge from 50% SOC to 55% SOC at a constant current of 4.6C;

[0244] Charge from 55% SOC to 60% SOC at a constant current of 4.4C;

[0245] Charge from 60% SOC to 65% SOC at a constant current of 4.2C;

[0246] Charge from 65% SOC to 70% SOC at a constant current of 3.9C;

[0247] Charge from 70% SOC to 75% SOC at a constant current of 3.5C;

[0248] Charge from 75% SOC to 80% SOC at a constant current of 3.0C;

[0249] Charge from 80% SOC to 100% SOC at a constant current of 0.33C.

[0250] 3. Volumetric energy density

[0251] The volumetric energy density (VED) test procedure for a single battery cell is as follows:

[0252] The battery cells of the examples and comparative examples were placed at 25°C and charged to 3.65V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 3.65V, and left to stand for 30 minutes; they were then discharged to 2.0V with a constant current of 0.33C, and the discharge capacity A0 was recorded at this time (Ah). The discharge plateau voltage was calculated (V). The length, width, and thickness of the battery cells were measured with calipers, and the volume of the battery cell V0 was calculated (L). The volumetric energy density of the battery cell VED = (A0 × discharge plateau voltage (3.2V)) ÷ V0 ÷ 1000 (Wh / L).

[0253] In this application, the length of the battery cell is equal to the coating length of the positive electrode film plus 45 mm.

[0254] Example 2

[0255] The preparation method and structure of the battery cell are the same as in Example 1, except that the cross-sectional area S of the terminal body (i.e., the cross-sectional area of ​​the terminal body perpendicular to the direction of current flow) is 100 mm. 2 .

[0256] Example 3

[0257] The preparation method and structure of the battery cell are the same as in Example 1, except that the cross-sectional area S of the terminal body is 130 mm². 2 .

[0258] Example 4

[0259] The preparation method and structure of the battery cell are the same as in Example 1, except that the cross-sectional area S of the terminal body is 140 mm². 2 .

[0260] Example 5

[0261] The preparation method and structure of the battery cell are the same as in Example 1, except that the cross-sectional area S of the terminal body is 169 mm². 2 .

[0262] Example 6

[0263] The preparation method and structure of the battery cell are the same as in Example 1, except that the cross-sectional area S of the terminal body is 40 mm². 2 .

[0264] Comparative Example 1

[0265] The preparation method and structure of the battery cell are the same as in Example 1, except that the cross-sectional area S of the terminal body is 38 mm². 2 The coating length of the positive electrode film is 710 mm, and the shell length is 755 mm.

[0266] The detailed differences between the individual battery cells in Examples 1-6 and Comparative Example 1, as well as the test results, are shown in Table 1.

[0267] Table 1

[0268] Example 7

[0269] The preparation method and structure of the battery cell are the same as in Example 3, except that the coating length of the positive electrode film is 185 mm and the length of the shell is 230 mm.

[0270] Example 8

[0271] The preparation method and structure of the battery cell are the same as in Example 3, except that the coating length of the positive electrode film is 285 mm and the length of the casing is 330 mm.

[0272] Example 9

[0273] The preparation method and structure of the battery cell are the same as in Example 3, except that the coating length of the positive electrode film is 300 mm and the length of the shell is 345 mm.

[0274] Example 10

[0275] The preparation method and structure of the battery cell are the same as in Example 3, except that the coating length of the positive electrode film is 470 mm and the length of the shell is 515 mm.

[0276] Example 11

[0277] The preparation method and structure of the battery cell are the same as in Example 3, except that the coating length of the positive electrode film is 600 mm and the length of the shell is 645 mm.

[0278] Example 12

[0279] The preparation method and structure of the battery cell are the same as in Example 3, except that the coating length of the positive electrode film is 620 mm and the length of the shell is 665 mm.

[0280] Comparative Example 2

[0281] The preparation method and structure of the battery cell are the same as in Example 3, except that the coating length of the positive electrode film is 15 mm, the length of the casing is 60 mm, and the cross-sectional area of ​​the terminal body is 169 mm². 2 .

[0282] The detailed differences between the individual battery cells in Examples 7-12 and Comparative Example 2, as well as the test results, are shown in Table 2.

[0283] Table 2

[0284] Comparing Examples 1-12 with Comparative Examples 1 and 2, it can be seen that when the ratio of the volumetric energy density VED of the battery cell to the minimum cross-sectional area S of the electrode terminal is 2Wh / L / mm², 2 Up to 10Wh / L / mm 2 When the ratio of volumetric energy density (VED) to S is controlled, a lithium phosphate battery cell can be obtained that combines high energy density, excellent fast charging performance, and long cycle life.

[0285] As can be seen from Examples 1-6, when the cross-sectional area of ​​the terminal body is smaller than the cross-sectional areas of both the first limiting part and the second limiting part, the cross-sectional area of ​​the terminal body can affect the overcurrent capacity of the electrode terminal. By adjusting the cross-sectional area of ​​the terminal body, the ratio of the volumetric energy density VED to S of the battery cell can be controlled, thereby reducing the DCR of the battery cell and improving the cycle life of the battery cell, thus obtaining a battery cell with both high energy density, excellent fast charging performance and long cycle life.

[0286] As can be seen from Comparative Example 2, although it has a low DCR and excellent cycle performance, its energy density is too low due to the short coating length of the positive electrode film.

[0287] As can be seen from the comparison of Examples 3, 7-12 and Comparative Example 2, the volumetric energy density of the battery cell is different when the coating length of the positive electrode film is different. By matching the electrode terminals with a suitable minimum cross-sectional area S, the DCR of the battery cell can be reduced and the cycle life of the battery cell can be improved, thereby obtaining a battery cell with high energy density, excellent fast charging performance and long cycle life.

[0288] Example 13

[0289] The preparation method and structure of the battery cell are the same as in Example 3, except that the cross-sectional area of ​​the first limiting part is 300 mm². 2 .

[0290] Example 14

[0291] The preparation method and structure of the battery cell are the same as in Example 3, except that the cross-sectional area of ​​the first limiting part is 500 mm². 2 .

[0292] Table 3 shows the detailed differences and test results of the battery cells in Examples 3, 13, and 14.

[0293] Table 3

[0294] As can be seen from Table 3, by adjusting the cross-sectional area of ​​the first limiting part, the overcurrent capacity of the battery cell can be further improved, the DCR of the battery cell can be reduced, and thus a battery cell with excellent fast charging performance can be obtained.

[0295] Example 15

[0296] The preparation method and structure of the battery cell are the same as in Example 3, except that the average particle size of the primary particles of the positive electrode active material (lithium iron phosphate material) is 200 nm, Dv10 is 0.33 μm, and Dv50 is 1.1 μm.

[0297] Example 16

[0298] The preparation method and structure of the battery cell are the same as in Example 3, except that the average particle size of the primary particles of the positive electrode active material (lithium iron phosphate material) is 380 nm, Dv10 is 0.38 μm, and Dv50 is 1.3 μm.

[0299] The detailed differences between the individual battery cells in Examples 3, 15, and 16, as well as the test results, are shown in Table 4.

[0300] Table 4

[0301] As can be seen from Examples 3, 15 and 16, by controlling the particle size of lithium iron phosphate material, the migration path of lithium ions in the solid phase can be shortened, the resistance of the battery cell can be reduced, and the high-temperature cycle life of the battery cell can be improved.

[0302] Example 17

[0303] The preparation method and structure of the battery cell are the same as in Example 3, except that the volume average particle size Dv50 of the first graphite particle is 18.5 μm, and the compaction density of the negative electrode film is 1.57 g / cm³. 3 .

[0304] Example 18

[0305] The preparation method and structure of the battery cell are the same as in Example 3, except that the volume average particle size Dv50 of the first graphite particle is 13 μm, and the compaction density of the negative electrode film is 1.54 g / cm³. 3 .

[0306] Example 19

[0307] The preparation method and structure of the battery cell are the same as in Example 3, except that the volume average particle size Dv50 of the second graphite particle is 10 μm.

[0308] Example 20

[0309] The preparation method and structure of the battery cell are the same as in Example 3, except that the volume average particle size Dv50 of the second graphite particle is 12.3 μm.

[0310] Table 5 shows the detailed differences between the individual battery cells in Examples 3, 17-20 and the test results.

[0311] Table 5

[0312] As can be seen from Examples 3 and 17-20, by adjusting the particle size of graphite particles in the first negative electrode film layer, the energy density of the battery cell can be improved by improving the compaction of the negative electrode film layer. By adjusting the particle size of graphite particles in the second negative electrode film layer, the DCR of the battery cell can be reduced and the fast charging performance of the battery cell can be improved.

[0313] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This 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 single battery cell, comprising: A housing, including a first wall, the housing having a receiving cavity; An electrode terminal is disposed on the first wall, and the minimum cross-sectional area of ​​the electrode terminal is S; An electrode assembly is disposed within the receiving cavity. The electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including lithium phosphate. The ratio of the volumetric energy density VED of the battery cell to S is 2Wh / L / mm². 2 Up to 10Wh / L / mm 2 .

2. The battery cell according to claim 1, wherein, The ratio of the volumetric energy density (VED) of the battery cell to that of S is 2 Wh / L / mm². 2 Up to 3.5Wh / L / mm 2 .

3. The battery cell according to claim 1 or 2, wherein, The volumetric energy density (VED) of the battery cell satisfies: 350Wh / L≤VED≤430Wh / L.

4. The battery cell according to any one of claims 1-3, wherein, The minimum cross-sectional area S of the electrode terminal satisfies: 40mm. 2 ≤S≤800mm 2 .

5. The battery cell according to any one of claims 1-4, wherein, The battery cell includes a cover plate assembly forming the first wall. The cover plate assembly includes a cover plate and the electrode terminal. The cover plate has a through hole. The electrode terminal includes a terminal body, a first limiting part, and a second limiting part. The terminal body passes through the through hole and connects the first limiting part and the second limiting part. The first limiting part is located on the side of the cover plate facing the receiving cavity, and the second limiting part is located on the side of the cover plate away from the receiving cavity.

6. The battery cell according to claim 5, wherein, The cross-sectional area of ​​the second limiting part is 300mm. 2 Up to 700mm 2 .

7. The battery cell according to claim 5 or 6, wherein, The cross-sectional area of ​​the first limiting part is 200mm. 2 Up to 800mm 2 .

8. The battery cell according to any one of claims 5-7, wherein, The cross-section of the terminal body is a rounded rectangle.

9. The battery cell according to claim 8, wherein, The cross-sectional area of ​​the terminal body is 40mm. 2 Up to 240mm 2 .

10. The battery cell according to any one of claims 1-9, wherein, Along the length of the positive electrode sheet, the coating length of the positive electrode film is 200mm-700mm.

11. The battery cell according to any one of claims 1-10, wherein, The single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 -340mg / 1540.25mm 2 The option is 240mg / 1540.25mm. 2 -300mg / 1540.25mm 2 .

12. The battery cell according to any one of claims 1-11, wherein, The compaction density of the positive electrode film layer corresponding to the single battery cell at 100% SOC is 2.5 g / cm³. 3 -2.8g / cm 3 .

13. The battery cell according to claim 5, wherein, The cover plate assemblies are disposed at both ends of the housing, and each cover plate assembly includes at least two electrode terminals.

14. The battery cell according to claim 5, wherein, The cover plate assembly is disposed at both ends of the housing, and each cover plate assembly includes at least two electrode terminals with opposite polarities.

15. The battery cell according to claim 5, wherein, The cover plate assembly is disposed at both ends of the housing, and each cover plate assembly includes at least two electrode terminals with opposite polarities. Along the length direction of the battery cell, the electrode terminals of the same polarity on the two cover plate assemblies are staggered. Optionally, the electrode terminals of the same polarity are diagonally arranged along the length direction of the battery cell.

16. The battery cell according to any one of claims 1-15, wherein, The electrode assembly further includes a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet are stacked. Each layer of the positive electrode sheet is provided with a positive electrode tab, and each layer of the negative electrode sheet is provided with a negative electrode tab.

17. The battery cell according to claim 16, wherein, The positive electrode tab extends along the length of the positive electrode sheet or along its width; and / or The negative electrode tab extends along the length of the negative electrode sheet or along its width.

18. The battery cell according to any one of claims 1-17, wherein, The lithium phosphate has a charging capacity of 150mAh / g-170mAh / g at a 0.1C rate.

19. The battery cell according to any one of claims 1-18, wherein, The lithium-containing phosphate includes compounds represented by Formula I: Li x1 A y1 Me a M b P 1-c X c Y z Formula I, Wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, P, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or two of O and F.

20. The battery cell according to any one of claims 1-19, wherein, The lithium-containing phosphate includes lithium iron phosphate materials.

21. The battery cell according to any one of claims 1-20, wherein, The lithium phosphate is in granular form, and the volume average particle size Dv50 of the lithium phosphate is 1μm-2μm.

22. The battery cell according to any one of claims 1-21, wherein, The volumetric particle size Dv10 of the lithium phosphate is 0.4 μm-0.7 μm.

23. The battery cell according to any one of claims 1-22, wherein, The lithium phosphate includes secondary particles, wherein the average particle size of the primary particles in the secondary particles is 200nm-500nm.

24. The battery cell according to any one of claims 1-23, wherein, The positive electrode film also includes a lithium replenishing agent, and the mass percentage of the lithium replenishing agent is 0.1%-5% based on the total mass of the positive electrode film.

25. The battery cell according to claim 24, wherein, The lithium supplement includes one or more of lithium nickel cobalt manganese oxide, lithium phosphate, dilithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickel oxide, and lithium ferrite.

26. The battery cell according to any one of claims 1-25, wherein, The positive electrode film layer also includes a conductive agent, and the mass percentage of the conductive agent is 0.1%-1% based on the total mass of the positive electrode film layer.

27. The battery cell according to claim 26, wherein, The conductive agent includes carbon nanotubes.

28. The battery cell according to any one of claims 1-27, wherein, The thickness of the positive electrode current collector is 10μm-16μm.

29. The battery cell according to any one of claims 1-28, wherein, The electrode assembly further includes a negative electrode sheet, which includes a negative current collector. At least one side of the negative current collector is provided with a negative electrode film layer, and the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm². 2 -170mg / 1540.25mm 2 The option is 110mg / 1540.25mm. 2 -150mg / 1540.25mm 2 .

30. The battery cell according to claim 29, wherein, The compaction density of the negative electrode film at 100% SOC of the battery cell is 1.15 g / cm³. 3 -1.36g / cm 3 The option is 1.25g / cm³. 3 -1.36g / cm 3 .

31. The battery cell according to claim 29 or 30, wherein, The negative electrode film layer includes a negative electrode active material, and the charging capacity of the negative electrode active material at a 0.1C rate is 350mAh / g-480mAh / g.

32. The battery cell according to any one of claims 29-31, wherein, The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode is disposed on at least one side of the negative electrode current collector, and the second negative electrode film layer is disposed on the side of the first negative electrode film layer away from the negative electrode current collector. The first negative electrode film layer includes a first graphite particle, and the second negative electrode film layer includes a second graphite particle. The volume average particle size of the first graphite particle is larger than the volume average particle size of the second graphite particle.

33. The battery cell according to claim 32, wherein, The first graphite particle comprises natural graphite.

34. The battery cell according to claim 32 or 33, wherein, The volume average particle size Dv50 of the first graphite particle is 7 μm-18.5 μm; and / or The volume average particle size Dv50 of the second graphite particle is 7μm-14.3μm.

35. The battery cell according to any one of claims 32-34, wherein, The first negative electrode film layer and / or the second negative electrode film layer comprise silicon-based materials, and the mass percentage of silicon element is 0.3%-10% based on the total mass of the negative electrode film layer.

36. The battery cell according to any one of claims 29-35, wherein, The thickness of the negative electrode current collector is 4μm-8.5μm.

37. The battery cell according to any one of claims 1-36, wherein, It also includes an electrolyte comprising chain carboxylic esters, wherein the chain carboxylic esters account for 5%-60% of the total mass of the electrolyte, and optionally 8%-30%.

38. The battery cell according to any one of claims 1-37, wherein, The battery cell is configured to charge from 10% SOC to 80% SOC in 5-10.5 minutes, optionally 7-10 minutes.

39. A battery device, wherein, The battery device includes any one of the battery cells according to claims 1-38, and the battery device is at least one of a battery module, a battery pack, and an energy storage device.

40. An electrical appliance, wherein, Includes a battery cell according to any one of claims 1-38 or a battery device according to claim 39, wherein the battery cell or the battery device is used to provide electrical energy.

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