Battery cell, battery device, and electric device

Abstract

The application provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly and a shell, the electrode assembly is arranged in an inner cavity of the shell, the volume energy density of the battery monomer is greater than or equal to 700 Wh / L, the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, the mass content of a sulfonimide lithium salt in the electrolyte is less than or equal to 20%, and the shell comprises a shell body, and the melting point of the shell body material is 800 DEG C-1800 DEG C. The battery monomer has high energy density and improved safety performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery device, and an electrical device. Background Technology

[0002] In recent years, with the increasingly wide range of applications, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant advancements in battery technology, higher requirements have been placed on the safety performance of high-energy-density batteries. Summary of the Invention

[0003] This application was made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery device, and an electrical device. The battery cell of this application improves safety performance while maintaining high energy density.

[0004] To achieve the above objectives, the first aspect of this application provides a battery cell, including an electrode assembly and a housing, wherein the electrode assembly is disposed in the inner cavity of the housing, the volumetric energy density of the battery cell is ≥700Wh / L, the electrode assembly includes a positive electrode, a negative electrode, and an electrolyte, and the electrolyte contains ≤20% by mass of sulfonylimide lithium salt; the housing includes a shell, and the shell material has a melting point of 800℃-1800℃.

[0005] Therefore, by limiting the content of sulfonylimide lithium salt in the electrolyte, this application can reduce the severity of the reaction during thermal runaway, reduce the rate of temperature rise and the amount of short-term heat release during thermal runaway, thereby reducing the impact of heat on the pressure relief mechanism and casing of the battery cell. At the same time, the high melting point casing material is less likely to break or crack during short-term high temperature rise and high heat release, maintaining the integrity of the battery cell casing, reducing heat spread in the battery module, and thus improving the safety performance of high energy density battery cells.

[0006] In any embodiment, the negative electrode sheet includes a negative current collector and a negative active layer located on at least one side of the negative current collector. The negative active layer includes a silicon-based material, and the silicon content in the negative active layer is 1%-65% by mass. Therefore, adding a silicon-based material to the negative active layer is beneficial for obtaining high-energy-density battery cells and for controlling the severity of the reaction during thermal runaway, thereby improving the safety performance of the battery cells.

[0007] In any embodiment, the negative electrode active layer includes a first negative electrode active layer and a second negative electrode active layer. The first negative electrode active layer is located on at least one side of the negative electrode current collector, and the second negative electrode active layer is located on the side of the first negative electrode active layer away from the negative electrode current collector. The second negative electrode active layer includes the silicon-based material. Therefore, by incorporating the silicon-based material into the second negative electrode active layer, the diffusion path during lithium-ion insertion is shortened, improving the kinetic performance of the battery cell.

[0008] In any embodiment, the silicon element has a mass content of 5%-65% in the second negative electrode active layer. Therefore, adding silicon-based materials with the aforementioned silicon content to the second negative electrode active layer is beneficial for improving both the dynamic performance and energy density of the battery cell.

[0009] In any embodiment, the first negative electrode active layer includes a first graphite, which includes at least one of artificial graphite and natural graphite; optionally, the first graphite includes artificial graphite and natural graphite; further optionally, the content of natural graphite is higher than that of artificial graphite.

[0010] In any embodiment, the second negative electrode active layer includes a second graphite, which includes at least one of artificial graphite and natural graphite; optionally, the degree of graphitization of the first graphite is lower than that of the second graphite.

[0011] In any embodiment, the thickness ratio of the first active layer to the second active layer is 1:9 to 9:1.

[0012] In any embodiment, the silicon-based material includes one or more of elemental silicon, silicon-oxygen composite material, and silicon-carbon composite material; optionally, the silicon-based material includes at least the silicon-carbon composite material.

[0013] In any embodiment, the silicon-carbon composite material satisfies one or more of the following characteristics:

[0014] 1) The silicon-carbon composite material includes porous carbon and silicon-containing material dispersed in the pores of the porous carbon, and optionally the porous carbon is hard carbon;

[0015] 2) The silicon content in the silicon-carbon composite material is 20%-70% or 30%-70% by mass;

[0016] 3) The average particle size of the silicon-carbon composite material is 2μm-15μm or 7μm-11μm;

[0017] 4) The powder resistivity of the silicon-carbon composite material at 8 MPa is 4 Ω·cm-17 Ω·cm;

[0018] 5) The BET specific surface area of ​​the silicon-carbon composite material is 1.0 m². 2 / g-6.7m 2 / g.

[0019] In any embodiment, the silicon-carbon composite material further includes a carbon-containing coating layer located on the surface of the porous carbon and / or the silicon-containing material.

[0020] In any embodiment, the mass content of the sulfonylimide lithium salt in the electrolyte is ≤10%. This helps to further reduce the severity of the reaction during thermal runaway of a single battery cell, decrease the rate of temperature rise during thermal runaway, and reduce the amount of short-term heat release during thermal runaway, thereby further improving the safety performance of high-energy-density battery cells.

[0021] In any embodiment, the mass content of the sulfonylimide lithium salt in the electrolyte is 0.5%-20%, 2.5%-20%, or 2.5%-10%. This, on the one hand, helps to suppress the severity of the reaction during thermal runaway of the battery cell, thereby improving the safety performance of the battery cell; on the other hand, it reduces the influence of the sulfonylimide lithium salt content on the thermal runaway boundary temperature of the battery cell.

[0022] In any embodiment, the electrolyte further contains lithium hexafluorophosphate, wherein the mass ratio of the sulfonylimide lithium salt to the lithium hexafluorophosphate is 1:50-5:1, 1:30-4:1, or 1:20-3:1.

[0023] In any embodiment, the melting point of the shell material is 900℃-1600℃ or 1200℃-1500℃; and / or,

[0024] The shell material has a tensile strength of 400MPa-1400MPa or 600MPa-1040MPa at room temperature; and / or,

[0025] The shell material has a tensile strength at 500℃ > 300 MPa and ≤ 1000 MPa, or is 450 MPa-900 MPa; and / or,

[0026] The shell material includes one or more of stainless steel, nickel-based alloys, titanium alloys, and titanium carbide alloys.

[0027] Therefore, in environments with rapid temperature rise and large instantaneous heat release, the aforementioned shell material is less prone to damage, melt-through, or weld cracking, which helps maintain the integrity of the shell and effectively controls heat spread in the battery module, thereby improving safety performance.

[0028] In any embodiment, the thickness of the casing is 0.1mm-1mm or 0.18mm-0.5mm. Thus, the aforementioned casing thickness range improves casing strength, thereby enhancing the safety performance of the battery cell, and also enables the battery cell to have a high energy density.

[0029] In any embodiment, the housing further includes a first end cap and a second end cap disposed at opposite ends of the housing.

[0030] In any embodiment, the battery cell further includes electrode terminals and a pressure relief mechanism, with the pressure relief mechanism disposed on the first end cover and the electrode terminals disposed on the second end cover. Therefore, placing the electrode terminals and the pressure relief mechanism at both ends of the casing facilitates thermoelectric separation, prevents the pressure relief mechanism from impacting the high-voltage wiring harness on the electrode terminal side during pressure relief, and improves the safety performance of the battery cell.

[0031] In any embodiment, the pressure relief mechanism includes a pressure relief port for opening when the internal pressure and / or temperature of the battery cell reaches a threshold to release the internal pressure and / or heat of the battery cell; the ratio of the area of ​​the pressure relief port to the discharge capacity of the battery cell is 2 mm². 2 / Ah–10mm 2 / Ah, 4.5mm 2 / Ah–9.0mm 2 / Ah or 4.65mm 2 / Ah–9.0mm 2 / Ah, where the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current. This facilitates timely pressure relief in the event of thermal runaway in the battery cell, reducing the airflow pressure within the cell and effectively maintaining the integrity of the battery cell casing while improving its safety performance.

[0032] In any embodiment, a first airflow channel is provided between the electrode assembly and the first end cap. This expands the space for airflow and material flow within the battery cell, reduces the pressure relief during thermal runaway, and thus improves the integrity of the battery cell casing during thermal runaway.

[0033] In any embodiment, the ratio of the minimum airflow area of ​​the first airflow channel to the discharge capacity of the battery cell is 0.05 mm². 2 / Ah-0.155mm 2 / Ah, wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current. This expands the flow space for airflow and materials within the battery cell, reducing the pressure relief during thermal runaway and improving the integrity of the casing; it also reduces the impact of the first airflow channel on the energy density of the battery cell.

[0034] In any embodiment, the battery cell further includes one or more fixing components, one end of which is connected to the electrode assembly and the other end of which is connected to the first end cap, for forming the first airflow channel between the electrode assembly and the first end cap.

[0035] In any embodiment, a second airflow channel is provided between the electrode assembly and the second end cap. This expands the space for airflow and material flow within the battery cell, reduces the pressure relief during thermal runaway, and thus improves the integrity of the battery cell casing during thermal runaway.

[0036] In any embodiment, the ratio of the minimum airflow area of ​​the second airflow channel to the discharge capacity of the battery cell is 0.02 mm. 2 / Ah-0.11mm 2 / Ah, wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current. This, on the one hand, helps to increase the flow space for airflow and materials within the battery cell, thereby reducing the pressure relief during thermal runaway and improving the integrity of the casing; on the other hand, it reduces the impact of the second airflow channel on the energy density of the battery cell.

[0037] In any embodiment, the inner wall of the second end cap is provided with an inwardly recessed groove to form the second airflow channel.

[0038] In any embodiment, the battery cell further includes one or more heat-resistant components, which are disposed along the length of the first end cap on the inner wall of the housing and close to the first end cap. Therefore, when the battery cell experiences thermal runaway and pressure relief, the temperature is high, and the portion of the housing near the first end cap is prone to large-area melting and penetration. Reinforcing the housing with heat-resistant components can improve the strength and integrity of the battery cell housing.

[0039] In any embodiment, the length of the heat-resistant component is equal to the length of the first end cap; and / or,

[0040] The dimension of the heat-resistant component along the direction perpendicular to the bottom surface of the first end cap is >0 and ≤4cm or >0 and ≤1cm; and / or,

[0041] The width of the heat-resistant component is greater than 0 and less than or equal to 1 mm, and the direction of the width is perpendicular to the direction of the length.

[0042] In any embodiment, the heat-resistant component is made of one or more of stainless steel, alumina, silicon nitride, and polyimide.

[0043] In any embodiment, the volumetric energy density of the battery cell is ≥720Wh / L, ≥740Wh / L, or 740-850Wh / L.

[0044] In any embodiment, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the positive current collector;

[0045] The positive electrode active layer comprises lithium nickel cobalt manganese oxide material; in the lithium nickel cobalt manganese oxide material, the molar ratio of Ni element in the total amount of Ni, Co, and Mn elements is 0.8:1-0.97:1 or 0.85:1-0.95:1. Therefore, setting a high-nickel content lithium nickel cobalt manganese oxide material in the positive electrode active layer is beneficial to improving the energy density of the battery cell.

[0046] In any embodiment, the lithium nickel cobalt manganese oxide material includes Li a Ni x Co y Mn 1-x-y-z M z O2, wherein 0.7≤a≤1.1, 0.8≤x≤0.97, 0<y<1, 0.001≤z≤0.01 and 0<1-xyz<1, and M includes one or more elements selected from Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, B, Mg, Zn, Ca, and Ce.

[0047] In any embodiment, the electrolyte further includes cyclic ester compounds. Therefore, the addition of cyclic ester compounds to the electrolyte helps reduce the intensity of the reaction during thermal runaway of a single battery cell, prolongs the thermal runaway reaction time to release heat slowly, reduces the rate of temperature rise, and thus improves the safety performance of the battery cell.

[0048] In any embodiment, the mass content of the cyclic ester compound in the electrolyte is 3%-35%, 3%-30%, or 5%-20%. This is beneficial for improving the kinetic performance of the battery cell and, on the other hand, reduces the adverse effects on the safety performance of the battery cell.

[0049] In any embodiment, the cyclic ester compound includes one or more of ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

[0050] A second aspect of this application provides a battery device including the battery cell of the first aspect of this application.

[0051] A third aspect of this application provides an electrical device, including a single battery cell according to the first aspect of this application or a battery device according to the second aspect of this application. Attached Figure Description

[0052] Figure 1A This is a front view of the internal structure of a battery cell according to one embodiment of this application.

[0053] Figure 1B This application Figure 1A A side view of the internal structure of a battery cell according to one embodiment is shown.

[0054] Figure 2A This is a front view of a battery cell according to another embodiment of this application.

[0055] Figure 2B This application Figure 2A The diagram shown is a side view of the internal structure of a battery cell according to another embodiment of this application.

[0056] Figure 3 This is a schematic diagram of a battery cell according to another embodiment of this application.

[0057] Figure 4 yes Figure 3 An exploded view of a battery cell according to another embodiment of this application is shown.

[0058] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application.

[0059] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0060] Figure 7 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown.

[0061] Figure 8 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0062] Explanation of reference numerals in the attached figures:

[0063] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly; 6 Electrode assembly; 7 First end cover; 8 First airflow channel; 9 Fixing component; 10 Second end cover; 11 Second airflow channel; 12 Plastic section; 13 Heat-resistant component; 14 Housing. Detailed Implementation

[0064] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0065] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0066] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0067] Unless otherwise specified, all steps of 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.

[0068] Unless otherwise specified, in this application, multiple airflow channel cross-sections can be obtained along the direction perpendicular to the gas flow direction, and the "minimum airflow area" in this application is the minimum value of the cross-sectional area of ​​these airflow channels.

[0069] [Battery cell]

[0070] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0071] The battery cell can be a lithium-ion battery, etc., but this application does not limit it.

[0072] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0073] High-energy-density battery cells typically employ highly electrochemically active cathode materials, anode materials, and electrolyte components. When a battery cell experiences thermal runaway, the reactions of these materials are intense, resulting in rapid temperature rise and the generation of a large amount of heat. This can easily lead to a sudden release of a large amount of energy during thermal runaway pressure relief, placing high demands on the pressure relief mechanism. Furthermore, conventional aluminum casings are generally unable to withstand the impact of such a large amount of energy, and their integrity is easily compromised, making the battery cell susceptible to safety issues. Therefore, there is an urgent need to improve the safety performance of high-energy-density battery cells.

[0074] To address the aforementioned technical problems, one embodiment of this application provides a battery cell, including an electrode assembly and a housing. The electrode assembly is disposed within the inner cavity of the housing. The volumetric energy density of the battery cell is ≥700Wh / L (optionally ≥720Wh / L, or ≥740Wh / L, more preferably 740-850Wh / L, such as 700Wh / L, 720Wh / L, 740Wh / L, 750Wh / L, 780Wh / L, 800Wh / L, 820Wh / L, 840Wh / L, 850Wh / L, 880Wh / L, 890Wh / L, 900Wh / L, or any range of the above values). The electrode assembly includes a positive electrode and a negative electrode. The electrode sheet and the electrolyte, wherein the mass content of the sulfonylimide lithium salt in the electrolyte is ≤20% (optionally 0.5%-20%, for example 0.5%, 1%, 2%, 2.5%, 3%, 4%, 5%, 6%, 8%, 10%, 12%, 14%, 15%, 17%, 18%, 20% or any range of the above values); the outer shell includes a shell material with a melting point of 800℃-1800℃ (for example 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, 1700℃, 1800℃ or any range of the above values).

[0075] The applicant unexpectedly discovered that, compared to lithium hexafluorophosphate, sulfonylimide lithium salts have higher conductivity, which can improve the kinetic performance of battery cells. Furthermore, the hydrofluoric acid produced when lithium hexafluorophosphate reacts with water corrodes the SEI film of both the positive and negative electrodes. Replacing lithium hexafluorophosphate at least partially with sulfonylimide lithium salts helps reduce the amount of hydrofluoric acid generated. However, sulfonylimide lithium salts have poor thermal stability and are prone to violent reactions during thermal runaway of battery cells, resulting in rapid temperature rise and instantaneous release of large amounts of heat, which can easily cause severe thermal shock to the casing. This application reduces the severity of the reaction during thermal runaway by limiting the content of sulfonylimide lithium salts in the electrolyte of high-energy-density battery cells, thereby reducing the rate of temperature rise during thermal runaway and the amount of short-term heat release. This reduces the impact of heat on the battery cell's pressure relief mechanism and casing. At the same time, the high-melting-point casing material is less likely to break or crack during short-term high temperature rise and high heat release, maintaining the integrity of the battery cell casing. This effectively controls the gas and / or heat generated by thermal runaway within the battery cell, reducing heat spread in the battery module and thus improving the safety performance of high-energy-density battery cells.

[0076] In this application, the volumetric energy density of the battery cell can be tested using conventional methods in the art. For example: the battery cell is placed at room temperature, charged with a constant current to the charging cutoff voltage, and then charged with a constant voltage to 0.05C; it is then discharged with a constant current to the discharge cutoff voltage, and the discharge capacity A0 and discharge plateau voltage V are recorded; the length, thickness, and height of the battery cell are measured using calipers (generally calculated based on the outer casing dimensions of the battery cell, excluding the height of the electrode terminals and the insulating film outside the casing), and the volume of the battery cell V0 is calculated; the volumetric energy density of the battery cell VED = (A0 × V) / V0, in Wh / L.

[0077] In this application, the melting point of the shell material can be tested using conventional methods in the art. For example, the powder of the shell material is placed in a capillary tube that is closed at one end, and then placed in the heating device of a melting point apparatus for heating. The initial melting temperature is recorded when the sample begins to melt, and the final melting temperature is recorded when the sample is completely melted. The melting point of the shell material is obtained by averaging the initial melting temperature and the final melting temperature.

[0078] [Negative electrode plate]

[0079] In some embodiments, the negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector. The negative active layer comprises a silicon-based material, and the silicon content in the negative active layer is 1%-65% by mass, for example, 1%, 5%, 7%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or any range of the above values. Therefore, adding a silicon-based material to the negative active layer is beneficial for obtaining high-energy-density battery cells and for controlling the severity of the reaction during thermal runaway, thereby improving the safety performance of the battery cells.

[0080] In this application, the silicon content in the negative electrode active layer is tested using conventional methods in the art. For example, the negative electrode sheet of the battery cell can be disassembled, thoroughly cleaned with a solvent, dried, and the negative electrode active layer material scraped off. The negative electrode active layer material is dissolved in a mixed solution of concentrated nitric acid and hydrofluoric acid, and the silicon content is determined by inductively coupled plasma (ICP) testing.

[0081] In some embodiments, the negative electrode active layer includes a first negative electrode active layer and a second negative electrode active layer. The first negative electrode active layer is located on at least one side of the negative electrode current collector, and the second negative electrode active layer is located on the side of the first negative electrode active layer away from the negative electrode current collector. The second negative electrode active layer includes the silicon-based material. Therefore, by incorporating the silicon-based material into the second negative electrode active layer, the diffusion path during lithium-ion insertion is shortened, improving the kinetic performance of the battery cell.

[0082] In some embodiments, the silicon element in the second negative electrode active layer has a mass content of 5%-65%, for example, 5%, 7%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or any combination of the above values. Therefore, adding the silicon-carbon composite material with the above-mentioned content to the second negative electrode active layer is beneficial for improving the energy density of the battery cell while enhancing its kinetic performance.

[0083] In this application, the mass content of silicon in the second negative electrode active layer can be retrieved by referring to the above-mentioned test method for the mass content of silicon in the negative electrode active layer, and will not be described again here.

[0084] In some embodiments, the first negative electrode active layer includes a first graphite, which includes at least one of artificial graphite and natural graphite; optionally, the first graphite includes artificial graphite and natural graphite; further optionally, the content of natural graphite is higher than that of artificial graphite.

[0085] In some embodiments, the second negative electrode active layer includes a second graphite, which includes at least one of artificial graphite and natural graphite; optionally, the degree of graphitization of the first graphite is lower than that of the second graphite.

[0086] In this application, the degree of graphitization of the first graphite and / or the second graphite can be determined using instruments and methods known in the art. For example, Appendix E of the national standard GB / T24533-2019 "Graphite Anode Materials for Lithium-ion Batteries" can be referred to. Artificial graphite is also applicable to the Chinese machinery industry standard JB / T4220-2011 "Method for Determination of Lattice Parameters of Artificial Graphite".

[0087] Specific testing steps: The graphitization degree G of the negative electrode active material was determined by automatically recording the 002, 004, 110, and 112 diffraction lines of carbon using an XRD diffractometer, while simultaneously reading the diffraction angle (2θobs)c. The corrected diffraction angle (2θcor)c was obtained using the internal standard method and substituted into the interplanar spacing formula to calculate the graphite interlayer spacing d002. The d002 data value was then substituted into the Mering-Maire formula: g = [(3.440 - d002) / (3.440 - 3.354)] × 100% to obtain the graphitization degree value G.

[0088] In any embodiment, the thickness ratio of the first negative electrode active layer to the second negative electrode active layer is 1:9-9:1.

[0089] In this application, the thickness ratio of different negative electrode active layers can be tested using methods known in the art. For example, the negative electrode sheet in the battery cell can be removed, and the negative electrode sheet can be cut with an ion beam to obtain a cross-section in the thickness direction. The cross-section can be observed by SEM to measure the thickness of each negative electrode active layer and calculate the thickness ratio.

[0090] In any embodiment, the silicon-based material includes one or more of elemental silicon, silicon-oxygen composite material, and silicon-carbon composite material; optionally, the silicon-based material includes at least the silicon-carbon composite material.

[0091] In some embodiments, the aforementioned silicon-oxygen composite material includes at least one of the following: non-lithium silicon-oxygen composite material, pre-lithium silicon-oxygen composite material, non-magnesium silicon-oxygen composite material, and pre-magnesium silicon-oxygen composite material.

[0092] In any embodiment, the silicon-carbon composite material satisfies one or more of the following characteristics:

[0093] 1) The silicon-carbon composite material includes porous carbon and silicon-containing material dispersed in the pores of the porous carbon, and optionally the porous carbon is hard carbon;

[0094] 2) The silicon content in the silicon-carbon composite material is 20%-70% or 30%-70%, for example, 20%, 30%, 40%, 44%, 46%, 50%, 55%, 60%, 65%, 70% or any range of the above values;

[0095] 3) The average particle size of the silicon-carbon composite material is 2μm-15μm or 7μm-11μm;

[0096] 4) The powder resistivity of the silicon-carbon composite material at 8 MPa is 4 Ω·cm-17 Ω·cm;

[0097] 5) The BET specific surface area of ​​the silicon-carbon composite material is 1.0 m². 2 / g-6.7m 2 / g.

[0098] In any embodiment, the silicon-carbon composite material further includes a carbon-containing coating layer located on the surface of the porous carbon and / or the silicon-containing material.

[0099] The silicon-carbon composite material of this application can be prepared using conventional silicon-carbon composite materials or conventional preparation methods, such as depositing nano-silicon materials on porous carbon by chemical vapor deposition, and further carbon coating, such as using amorphous carbon coating.

[0100] In some embodiments, the silicon-carbon composite material includes a core comprising porous carbon and silicon-containing material dispersed in the pores of the porous carbon. The porous carbon, acting as a carrier for the silicon-containing material, provides support for the nanoscale silicon-containing material and, simultaneously, provides expansion space for the silicon-containing material particles, effectively mitigating stress compression caused by expansion during charging. Especially when the silicon-containing material particles are nanoscale in size, the specific capacity is higher and dispersion within the pores of the porous carbon is facilitated. Furthermore, the buffering effect of the porous carbon's pores on expansion can be more fully utilized. When this silicon-carbon composite material is applied in wound electrode assemblies, it can significantly alleviate the stretching of the outer negative electrode sheet caused by silicon expansion.

[0101] In some embodiments, the porous carbon may optionally be hard carbon. When the porous carbon is hard carbon, it has stronger support, a more stable pore structure, and is harder, thus providing better porosity for the negative electrode active layer, providing a smoother path for active ion transport, and improving the charging capability of the battery cell.

[0102] In some embodiments, the silicon-containing material includes at least one of elemental silicon, silicon oxides, silicon nitrides, and silicon alloys.

[0103] In some embodiments, the silicon-containing material includes crystalline silicon, thereby further improving the structural stability of the silicon-containing material and the energy density of the battery cell.

[0104] In some embodiments, the silicon-carbon composite material further includes a carbon-containing coating layer that coats the surface of the core. This can improve the conductivity of the silicon-carbon composite material and reduce the internal impedance of the battery cell. At the same time, it can effectively reduce the probability of direct contact between the silicon-containing material in the porous carbon channels and the external environment, thereby improving the chemical stability of the silicon-carbon composite material.

[0105] In some embodiments, the silicon content in the silicon-carbon composite material is 30%-70% by mass. This approach, while maximizing the specific capacity of the negative electrode active material by utilizing silicon, also facilitates the full dispersion of silicon in the porous carbon material and helps control the expansion of silicon during charging.

[0106] In this application, the method for testing the silicon content in silicon-carbon composite materials can be a method known in the art. As an example, the following method can be used for testing: a certain amount of silicon-carbon composite material is taken, and the mass of silicon element in the silicon-carbon composite material is obtained by inductively coupled plasma optical emission spectrometry (ICP-OES). The mass percentage of silicon element in the silicon-carbon composite material can be calculated.

[0107] In addition to providing structural support and buffering for the expansion of silicon materials, the pores in the silicon-carbon composite material also form between the particles. To further improve the flow of lithium ions through the intraparticle and interparticle pores, in some embodiments, the average particle size of the silicon-carbon composite material is 2μm-15μm. Optionally, the average particle size of the silicon-carbon composite material is 7μm-11μm, or 5μm-10μm. This average particle size distribution between the silicon-carbon composite material and the first and / or second graphite materials facilitates the use of interparticle gaps to increase the compaction of the negative electrode active layer, thereby further improving the energy density of the battery cell.

[0108] The average particle size of the aforementioned silicon-carbon composite material can be tested using equipment and methods known in the art. For example, a scanning electron microscope (SEM) can be used (e.g., ZEISS Sigma 300), referring to JY / T010-1996, to obtain SEM images of the negative electrode sheet. As an example, the test can be performed as follows: Randomly select a test sample of length × width = 50 mm × 100 mm on the negative electrode sheet. Randomly select multiple test areas (e.g., 5) within the test sample, and at a certain magnification (e.g., 1000x when measuring silicon-carbon composites), read the particle size of each silicon-carbon composite particle in each test area (i.e., take the distance between the two farthest points on the silicon-carbon composite particle as the particle size). Count the number and particle size values ​​of silicon-carbon composite particles in each test area, and take the arithmetic mean of the silicon-carbon composite particles in each test area, which is the average particle size of the silicon-carbon composite particles in the test sample. To ensure the accuracy of the test results, multiple test samples (e.g., 10) can be taken and the above test can be repeated. The average value of each test sample can be taken as the final test result.

[0109] In some embodiments, the powder resistivity of the silicon-carbon composite material at 8 MPa is 4 Ω·cm-17 Ω·cm. This control of powder resistivity improves the conductivity of the silicon-carbon composite material, thereby increasing the charging rate of the battery cell.

[0110] In this application, the powder resistivity of silicon-carbon composite materials can be determined using methods known in the art. As an example, a four-probe method can be used, where two probes apply voltage and the other two probes measure current. At 8 MPa, the powder resistivity can be calculated by measuring the resistance value. Models of four-probe semiconductor powder resistivity testers include the ST-2722.

[0111] In some embodiments, the BET specific surface area of ​​the silicon-carbon composite material is 1.0 m². 2 / g-6.7m 2 / g.

[0112] In this application, the method for testing the BET specific surface area of ​​silicon-carbon composite materials can be a method known in the art. As an example, referring to GB / T 19587-2017, the nitrogen adsorption specific surface area analysis method can be used. The sample tube containing the silicon-carbon composite material sample is immersed in liquid nitrogen at -196℃, and the amount of nitrogen adsorbed on the surface of the solid sample at different pressures of 0.05 to 0.30 is measured. Based on the BET multilayer adsorption theory and calculation formula, the amount of monolayer adsorption of the sample is obtained, and thus the BET specific surface area is obtained. This test can be performed using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0113] The silicon-carbon composite material used in this application is derived from conventional silicon-carbon composite materials in the art, which, in addition to silicon and carbon, may also contain oxygen, nitrogen, and other elements. In some embodiments, the carbon content, by mass, is greater than 70% of the total amount of elements other than silicon in the negative electrode active layer of the silicon-carbon composite material. By controlling the carbon content in the total amount of elements other than silicon, the silicon-carbon composite material is made predominantly composed of silicon and carbon, thus better leveraging the structural and electrical performance advantages of these two elements.

[0114] As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0115] As an example, the negative electrode active material may further employ negative electrode active materials known in the art for use in battery cells. For example, the negative electrode active material may include at least one of the following materials: soft carbon, hard carbon, tin-based materials, and lithium titanate, etc. Tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0116] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0117] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0118] In some embodiments, the negative electrode active layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0119] In some embodiments, the negative electrode active layer may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0120] In some embodiments, the negative electrode active layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0121] 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.

[0122] Electrolytes

[0123] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel-like, or solid.

[0124] In some embodiments, the mass content of the sulfonylimide lithium salt in the electrolyte is ≤10%. This helps to further reduce the severity of the reaction during thermal runaway of a single battery cell, decrease the rate of temperature rise during thermal runaway, and reduce the amount of short-term heat release during thermal runaway, thereby further improving the safety performance of high-energy-density battery cells.

[0125] In some embodiments, the mass content of the sulfonylimide lithium salt in the electrolyte is 0.5%-20%, 2.5%-20%, or 2.5%-10%, for example, 0.5%, 1%, 2%, 2.5%, 3%, 5%, 7%, 8%, 10%, 11%, 13%, 15%, 16%, 18%, 20%, or any combination of the above values. This, on the one hand, helps to suppress the severity of the reaction during thermal runaway of the battery cell, thereby improving the safety performance of the battery cell; on the other hand, it reduces the influence of the sulfonylimide lithium salt content on the thermal runaway boundary temperature of the battery cell.

[0126] In some embodiments, the electrolyte further contains lithium hexafluorophosphate, wherein the mass ratio of the sulfonylimide lithium salt to the lithium hexafluorophosphate is 1:50-5:1, 1:30-4:1, or 1:20-3:1.

[0127] In some embodiments, the electrolyte further includes cyclic ester compounds. Therefore, the addition of cyclic ester compounds to the electrolyte helps reduce the intensity of the reaction during thermal runaway of a single battery cell, prolongs the thermal runaway reaction time to release heat slowly, reduces the rate of temperature rise, and thus improves the safety performance of the battery cell.

[0128] In some embodiments, the mass content of the cyclic ester compound in the electrolyte is 3%-35%, 3%-30%, or 5%-20%, for example, 3%, 5%, 7%, 9%, 10%, 13%, 15%, 17%, 20%, 22%, 24%, 25%, 27%, 29%, 30%, 31%, 33%, 35%, or any combination of the above values. Thus, on the one hand, the addition of the cyclic ester compound is beneficial to improving the kinetic performance of the battery cell; on the other hand, maintaining the content of the cyclic ester compound within an appropriate range reduces its adverse effects on battery safety performance.

[0129] In some embodiments, the cyclic ester compound includes one or more of ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

[0130] In some embodiments, the electrolyte contains ≤20% by mass of sulfonamide lithium salts and 3%-30% by mass of cyclic ester compounds.

[0131] In some embodiments, the electrolyte contains ≤10% by mass of sulfonamide lithium salts and 5%-20% by mass of cyclic ester compounds.

[0132] This helps to mitigate the intensity of thermal runaway in individual battery cells, allowing heat to be released slowly and thus improving the safety performance of individual battery cells.

[0133] In some embodiments, the liquid electrolyte also includes a solvent.

[0134] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0135] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0136] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0137] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0138] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0139] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0140] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0141]

shell

[0142] In some embodiments, the melting point of the shell material is 900°C-1600°C or 1200°C-1500°C; and / or,

[0143] The shell material has a tensile strength of 400MPa-1400MPa or 600MPa-1040MPa at room temperature, for example, 400MPa, 500MPa, 600MPa, 700MPa, 800MPa, 900MPa, 1000MPa, 1040MPa, 1100MPa, 1200MPa, 1300MPa, 1400MPa, or any range of the above values; and / or,

[0144] The shell material has a tensile strength at 500°C >300MPa and ≤1000MPa, or is between 450MPa and 900MPa, for example, 310MPa, 350MPa, 400MPa, 450MPa, 500MPa, 600MPa, 700MPa, 800MPa, 900MPa, 1000MPa, or any range of the above values; and / or,

[0145] The shell material includes one or more of stainless steel, nickel-based alloys, titanium alloys (e.g., titanium-aluminum alloys), and titanium carbide alloys.

[0146] Therefore, in environments with rapid temperature rise and large instantaneous heat release, the aforementioned shell material is less prone to damage, melt-through, or weld cracking, which helps maintain the integrity of the shell and effectively controls heat spread in the battery module, thereby improving safety performance.

[0147] In this application, the tensile strength of the shell material can be tested using conventional methods in the art. Specifically, the test can be performed with reference to the GB / T228.1-2010 standard. As an example, the following method can be used: measure the initial cross-sectional area of ​​the shell material specimen, install the specimen in the fixture of a tensile testing machine, and stretch it at a certain tensile speed (e.g., 3 mm / min) at a set temperature until the specimen breaks. The force applied at this point is recorded as the maximum tensile force. The tensile strength is obtained by dividing the maximum tensile force by the initial cross-sectional area of ​​the specimen.

[0148] In some embodiments, the thickness of the casing is 0.1mm-1mm or 0.18mm-0.5mm, for example, 0.1mm, 0.18mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, or any range of the above values. Thus, the aforementioned casing thickness range improves casing strength, thereby enhancing the safety performance of the battery cell, and also enables the battery cell to have a high energy density.

[0149] In this application, the thickness of the shell can be tested using conventional methods, such as measuring it with vernier calipers.

[0150] In any embodiment, the housing further includes a first end cap and a second end cap disposed at opposite ends of the housing.

[0151] As an example, the nickel-based alloy can be an alloy with metallic nickel as the main component and other metals such as copper, chromium, molybdenum, iron, cobalt, and titanium to improve its specific high-temperature strength. In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing serves to protect the electrode assembly, and a sealing bag is included between the housing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag can be a bag-shaped insulating component or an aluminum-plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0152] As an example, a battery cell can be a prismatic battery cell or a cylindrical battery cell, wherein a prismatic battery cell includes a prismatic battery cell, a blade-shaped battery cell, etc.

[0153] In some embodiments, the battery cell further includes electrode terminals and a pressure relief mechanism, with the pressure relief mechanism disposed on the first end cover and the electrode terminals disposed on the second end cover. Therefore, placing the electrode terminals and the pressure relief mechanism at both ends of the casing facilitates thermoelectric separation, prevents the pressure relief mechanism from impacting the high-voltage wiring harness on the electrode terminal side during pressure relief, and improves the safety performance of the battery cell.

[0154] In some implementations, the electrode terminals can be directly connected to the tabs, or indirectly connected to the tabs via current collectors.

[0155] In some embodiments, when a battery cell has two electrode terminals, the electrode terminals can be placed on the same side of the battery cell or respectively disposed on two opposite end faces of the battery cell.

[0156] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0157] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0158] In some embodiments, the pressure relief mechanism includes a pressure relief port for opening when the internal pressure and / or temperature of the battery cell reaches a threshold value to release the internal pressure and / or heat of the battery cell; the ratio of the area of ​​the pressure relief port to the discharge capacity of the battery cell is 2 mm². 2 / Ah–10mm 2 / Ah, 4.5mm 2 / Ah–9.0mm 2 / Ah or 4.65mm 2 / Ah–9.0mm 2 / Ah (e.g., 2mm) 2 / Ah, 2.5mm 2 / Ah, 3mm 2 / Ah, 3.5mm 2 / Ah, 4mm 2 / Ah, 4.5mm 2 / Ah, 4.65mm 2 / Ah, 5mm 2 / Ah, 5.5mm 2 / Ah, 7mm 2 / Ah, 8mm2 / Ah, 9mm 2 / Ah, 10mm 2 / Ah or any of the above values), wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C constant current at room temperature. This facilitates timely pressure relief in the event of thermal runaway in the battery cell, reducing the airflow pressure within the battery cell and effectively maintaining the integrity of the battery cell casing while improving the battery cell's safety performance.

[0159] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0160] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0161] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0162] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0163] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0164] In some implementations, such as Figures 1A-1B As shown, a first airflow channel 8 is provided between the electrode assembly 6 and the first end cap 7. This expands the space for airflow and material flow within the battery cell, reduces the pressure relief during thermal runaway, and thus improves the integrity of the battery cell casing during thermal runaway.

[0165] In some embodiments, the ratio of the minimum airflow area of ​​the first airflow channel 8 to the discharge capacity of the battery cell is 0.05 mm. 2 / Ah-0.155mm 2 / Ah (e.g., 0.05mm) 2 / Ah, 0.07mm 2 / Ah, 0.1mm 2 / Ah, 0.11mm2 / Ah, 0.13mm 2 / Ah, 0.14mm 2 / Ah, 0.15mm 2 / Ah, 0.155mm 2 / Ah or any of the above values), wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current. This expands the flow space for airflow and materials within the battery cell, reducing the pressure relief during thermal runaway and improving the integrity of the casing; it also reduces the impact of the first airflow channel 8 on the energy density of the battery cell.

[0166] In some implementations, such as Figures 1A-1B As shown, the battery cell also includes one or more fixing components 9. One end of the fixing component is connected to the electrode assembly 6, and the other end is connected to the first end cap 7, for forming the first airflow channel 8 between the electrode assembly 6 and the first end cap 7. There are no special requirements for the structure and shape of the fixing component 9, as long as it meets the above requirements.

[0167] In some embodiments, the fixing component 9 is made of high-melting-point metal materials (such as stainless steel (iron-based alloy), nickel-based alloy, cobalt-based alloy, tungsten-based alloy, etc.). To meet the requirements of electronic insulation and electrochemical stability, the fixing component may be coated with alumina ceramic or polyvinylidene fluoride polymers on its outer surface.

[0168] In some implementations, such as Figures 1A-1B As shown, a second airflow channel 11 is provided between the electrode assembly 6 and the second end cap 10. This expands the space for airflow and material flow within the battery cell, reduces the pressure relief during thermal runaway, and thus improves the integrity of the battery cell casing during thermal runaway.

[0169] In some embodiments, the ratio of the minimum airflow area of ​​the second airflow channel 11 to the discharge capacity of the battery cell is 0.02 mm. 2 / Ah-0.11mm 2 / Ah (e.g., 0.02mm) 2 / Ah, 0.03mm 2 / Ah, 0.05mm 2 / Ah, 0.06mm 2 / Ah, 0.07mm 2 / Ah, 0.08mm 2 / Ah, 0.09mm 2 / Ah, 0.10mm 2 / Ah, 0.11mm 2 / Ah or any of the above values), wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current. This, on the one hand, helps to increase the flow space for airflow and materials within the battery cell, thereby reducing the pressure relief during thermal runaway and improving the integrity of the casing; on the other hand, it reduces the impact of the second airflow channel 11 on the energy density of the battery cell.

[0170] In some implementations, such as Figures 1A-1B As shown, the inner wall of the second end cap 10 has an inwardly formed groove to form the second airflow channel.

[0171] In some implementations, such as Figures 1A-1B As shown, the second end cap 10 includes a plastic section 12 near the electrode assembly, and the groove is formed on the plastic section.

[0172] In this application, "room temperature" has the conventional definition in the art, also referred to as general temperature or room temperature. For example, room temperature can be in the range of 15°C to 25°C, such as 25°C.

[0173] In some embodiments, the minimum airflow area of ​​the first airflow channel 8 or the second airflow channel 11 can be tested using area measurement methods conventional in the art. For example, it can be tested using the following methods:

[0174] Disassemble the battery cell, measure the minimum distance between two adjacent fixed parts 9 and the minimum height of the fixed parts 9, and multiply the minimum distance by the minimum height of the fixed parts 9 to obtain the minimum airflow area of ​​the first airflow channel 8; measure the minimum depth and minimum width of the groove on the inner wall of the second end cover 10, and multiply them to obtain the minimum airflow area of ​​the second airflow channel 11.

[0175] In some implementations, such as Figures 2A to 2B As shown, the battery cell also includes one or more heat-resistant components 13, which are disposed along the length of the first end cap 7 on the inner wall of the housing 14 and close to the first end cap 7. Therefore, when the battery cell experiences thermal runaway and pressure relief, the temperature is high, and the portion of the housing close to the first end cap 7 is prone to large-area melting and penetration. Reinforcing the housing with heat-resistant components 13 can improve the strength and integrity of the battery cell housing.

[0176] In some embodiments, the length of the heat-resistant component 13 is equal to the length of the first end cap 7; and / or,

[0177] The dimension of the heat-resistant component 13 along the direction perpendicular to the bottom surface of the first end cap 7 is >0 and ≤4cm or >0 and ≤1cm, for example, 1mm, 3mm, 5mm, 1cm, 1.5cm, 2cm, 2.5cm, 3cm, 3.5cm, 4cm or any range of the above values; and / or,

[0178] The width of the heat-resistant component 13 is greater than 0 and less than or equal to 1 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm or any range of the above values, and the direction of the width is perpendicular to the direction of the length.

[0179] In some embodiments, the heat-resistant component 13 is made of one or more of stainless steel, alumina, silicon nitride, and polyimide.

[0180] In some embodiments, the volumetric energy density of the battery cell is ≥720Wh / L, ≥740Wh / L, or 740-850Wh / L.

[0181]

Positive Electrode

[0182] In some embodiments, the positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector; the positive active layer includes a lithium nickel cobalt manganese oxide material; in the lithium nickel cobalt manganese oxide material, the molar ratio of Ni element in the total amount of Ni, Co, and Mn is 0.8:1-0.97:1 or 0.85:1-0.95:1, for example, 0.8:1, 0.85:1, 0.87:1, 0.9:1, 0.93:1, 0.95:1, 0.97:1, or any range of the above values. Therefore, incorporating a high-nickel-content lithium nickel cobalt manganese oxide material into the positive active layer is beneficial for improving the energy density of the battery cell.

[0183] In some embodiments, the lithium nickel cobalt manganese oxide material includes Li a Ni x Co y Mn 1-x-y-z M zO2, wherein 0.7≤a≤1.1 (e.g., 0.7, 0.8, 0.9, 1.0, 1.1 or any range of the above values), 0.8≤x≤0.97 (e.g., 0.8, 0.82, 0.85, 0.87, 0.9, 0.93, 0.95, 0.97 or any range of the above values), 0<y<1, 0.001≤z≤0.01 (e.g., 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01 or any range of the above values) and 0<1-xyz<1, M includes one or more elements selected from Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, B, Mg, Zn, Ca, Ce.

[0184] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0185] As an example, the positive electrode active material may also include at least one of the following materials: lithium phosphate, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0186] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0187] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0188] In some embodiments, the positive electrode active layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0189] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0190] 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.

[0191]

Isolation Components

[0192] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0193] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0194] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. 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. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0195] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0196] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0197] [Structure of the Electrode Assembly]

[0198] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0199] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0200] In some implementations, the electrode assembly is a stacked structure.

[0201] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0202] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0203] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0204] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0205] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0206] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0207] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0208] [Battery Device]

[0209] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0210] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0211] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0212] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0213] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0214] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0215] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0216] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0217] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0218] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0219] For example, Figure 3 The example shown is a square-structured battery cell 5.

[0220] In some implementations, refer to Figure 4The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0221] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0222] Figure 5 This is battery module 4 as an example. (See reference...) Figure 5 In the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0223] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0224] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0225] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0226] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0227] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0228] Figure 8 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0229] [Example]

[0230] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0231] Example 1

[0232] (1) Preparation of the positive electrode: positive active material LiNi 0.9 Co 0.05 Mn 0.05 O2, conductive agent acetylene black, and binder polyvinylidene fluoride were added to the solvent N-methyl-2-pyrrolidone (NMP) at a mass ratio of 97:2:1, and stirred evenly to prepare a positive electrode slurry. The slurry was then uniformly coated onto an aluminum foil with a thickness of 13 μm, resulting in an areal density of 300 mg / 1540.25 mm². 2 After drying, the material is cold-pressed, then die-cut and slit to form positive electrode sheets.

[0233] (2) Preparation of the negative electrode: A silicon-carbon composite material (nano-silicon deposited within porous carbon pores, silicon content 45%, average particle size 10 μm, powder resistivity 12 Ω·cm at 8 MPa, specific surface area 2.5 m²) was prepared. 2A negative electrode slurry is prepared by mixing a mixture of graphite (artificial graphite and natural graphite in a 4:1 mass ratio), conductive carbon, sodium carboxymethyl cellulose (CMC) as a thickener, and styrene-butadiene rubber (SBR) as a binder in a mass ratio of 44:52:2:1:1 with a certain amount of water and stirring evenly. The negative electrode slurry is then uniformly coated onto a 6μm thick copper foil with an areal density of 120mg / 1540.25mm². 2 After being dried in an oven and cold-pressed, the material is die-cut and slit to form negative electrode sheets. The negative electrode active layer of the negative electrode sheet contains 20% silicon and 52% graphite.

[0234] (3) Separation membrane: Polyethylene is used as the base membrane, and a 3μm thick aluminum oxide coating is coated on the base membrane to obtain the separation membrane.

[0235] (4) Preparation of electrolyte: Lithium hexafluorophosphate was dissolved in a solvent of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylene carbonate (EC) (volume ratio 1:1:1) to obtain the electrolyte. Lithium bis(fluorosulfonyl)imide (LiFSI) additive was added to the electrolyte, with a LiFSI mass fraction of 20% and a lithium hexafluorophosphate concentration of 1 mol / L.

[0236] (5) Assembly: The positive electrode sheet, negative electrode sheet, and separator are wound together, and then processed through encapsulation, electrolyte injection, formation, and venting to obtain a battery cell. The battery cell casing includes a housing and a first end cap and a second end cap located at opposite ends of the housing. The housing is made of stainless steel with a melting point of 1500℃, a tensile strength of 648MPa at 25℃, and a tensile strength of 474MPa at 500℃. The housing thickness is 0.18mm. The ratio A between the pressure relief port area and the discharge capacity is 10mm². 2 / Ah. The discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current.

[0237] Battery cell testing:

[0238] (1) Method for testing the volumetric energy density of a single battery cell:

[0239] Place the battery cell at 25°C and charge it to 4.25V with a constant current of 1 / 3C, then charge it to 0.05C with a constant voltage. Discharge it to 2.5V with a constant current of 1 / 3C and record the discharge capacity A0 and discharge plateau voltage V. Use calipers to measure the length, thickness, and height of the battery cell (generally calculated based on the outer casing dimensions, excluding the height of the electrode terminals and the insulating film outside the casing), and calculate the volume V0 of the battery cell. The volumetric energy density of the battery cell is VED = (A0 × V) / V0, in Wh / L.

[0240] (2) Thermal box safety test method for individual battery cells:

[0241] The test follows the "Heating" section of the safety test in GB 38031-2020. The specific test method is as follows: The battery cell is charged to 4.25V at a constant current of 1 / 3C at 25℃. After standing for 30 minutes, it is placed in a heating test chamber and heated to 60℃ at a rate of 5℃ / min and held for 5 hours. Then, the temperature is increased by 5℃ / min and held for 30 minutes at each additional 5℃ increase until the battery cell experiences thermal runaway (thermal runaway is defined as a 50% voltage drop within 1 minute or an internal temperature exceeding 200℃) or the cumulative time for holding at each 5℃ increase for 30 minutes reaches 24 hours. The test ends at this point. Record the temperature of the battery cell at the end of the test and the holding time at that temperature.

[0242] (3) Test method for charging time of individual battery cells from 10% SOC to 80% SOC:

[0243] At 25°C, the battery cell was charged to 4.25V at a constant current of 0.33C, then charged to 0.05C at a constant voltage. After standing for 5 minutes, it was discharged to 2.5V at a constant current of 0.33C, and its actual capacity was recorded as C0.

[0244] The battery cells were sequentially charged at constant currents of 0.33C0, 0.5C0, 1.0C0, 1.5C0, 2.0C0, 2.5C0, and 3.0C0 to a negative electrode cutoff potential of 4.25V or 0V (whichever comes first). After each charge, the cells were discharged to 2.5V at 1C0. The negative electrode potentials corresponding to the states of charge (SOC) of 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% were recorded at different charging rates. Charging rate-negative electrode potential curves were plotted for different SOC states. Linear fitting was performed to obtain the charging rate corresponding to a negative electrode potential of 0V for each SOC state. This charging rate represents the charging window for that SOC state, denoted as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, and C80%SOC. The charging time T (assuming no lithium plating in the battery cell) from 10% SOC to 80% SOC was calculated using the following formula, in minutes.

[0245] T=(0.1 / C10%SOC+0.1 / C20%SOC+0.1 / C30%SOC+0.1 / C40%SOC+0.1 / C50%SOC+0.1 / C60%SOC+0.1 / C70%SOC+0.1 / C80%SOC)×60

[0246] (4) Thermal runaway pressure relief test of individual battery cells:

[0247] A 300W heating film is placed at the geometric center of the battery cell, and multiple temperature monitoring points are set on the battery cell (such as the various surfaces of the outer casing, pressure relief port, positive and negative terminals, electrode assembly surfaces, etc.), with a multi-channel acquisition frequency of 0.01s.

[0248] The battery cells were fully charged to 100% SOC at 22±5℃, and their initial weight was measured. The battery cells were heated using a heating film. Depressurization began when a high-temperature, high-pressure gas stream (or flame) was ejected from the pressure relief port. The ejection pressure then decreased to a normal combustion state. After cooling for 1 hour, the remaining weight of the battery cells was measured. The thermal runaway weight loss rate was calculated using the following formula.

[0249] Thermal runaway weight loss rate = 100% × (initial weight of battery cell - remaining weight of battery cell) / initial weight of battery cell.

[0250] Examples 2 to 6 and Comparative Examples 1 to 4 were based on Example 1, with adjustments made to the mass content of lithium sulfonamide salt, and / or the use of different shells, and / or the A value, while remaining the same as Example 1. The test results are recorded in Table 1.

[0251] Table 1

[0252]

[0253] It can be seen from the above table:

[0254] Compared with the excessively high LiFSI content in the electrolyte in Comparative Examples 1-2, the thermal runaway reaction intensity of the battery cells in Examples 1-6 of this application is significantly reduced, the degree of shell breakage is significantly reduced, the safety performance is significantly improved, and the kinetic performance is better.

[0255] Compared with the low-melting-point shell material used in Comparative Examples 3-4, the degree of shell breakage during thermal runaway of the battery cells in Examples 1-6 of this application is significantly reduced, and the safety performance is significantly improved.

[0256] As shown in the table above, compared with the lower LiFSI content in Example 6, the battery cells in Examples 1-5 have higher thermal runaway boundary temperatures and better kinetic performance.

[0257] Example 7

[0258] Based on Example 5, a silicon-carbon composite material with a silicon element content of 68% by mass was used to replace the silicon-carbon composite material and graphite in Example 5 to prepare the negative electrode sheet. The rest is the same as in Example 5.

[0259] The test results are recorded in Table 2.

[0260] Table 2

[0261]

[0262]

[0263] As can be seen from the table above, compared with the higher silicon content of the negative electrode active layer in Example 7, the thermal runaway reaction intensity of the battery cell in Example 5 of this application is reduced, the degree of shell damage is reduced, the safety performance is improved, and the kinetic performance of the battery cell is improved.

[0264] Example 8

[0265] The first slurry is prepared by adding a certain amount of water to graphite, conductive carbon, thickener sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a mass ratio of 96:2:1:1 and stirring evenly.

[0266] A second slurry was prepared by adding a certain amount of water to a silicon-carbon composite material (formed by nano-silicon deposition in porous carbon pores, with a silicon content of 42%), conductive carbon, sodium hydroxymethyl cellulose (CMC) thickener, and styrene-butadiene rubber (SBR) binder in a mass ratio of 96:2:1:1 and stirring evenly.

[0267] First, a first slurry is uniformly coated onto a 6μm thick copper foil used as a negative electrode current collector, and then dried in an oven at 85℃ to form a first negative electrode active layer loaded on the current collector. Next, a second slurry is coated onto the dried first negative electrode active layer, dried at 85℃, and then cold-pressed to form the negative electrode sheet. The thickness ratio of the first to the second negative electrode active layer is 1:1. The areal density of the negative electrode active layer is 120mg / 1540.25mm². 2 .

[0268] The rest is the same as in Example 1.

[0269] Example 9

[0270] The first slurry is prepared by adding a certain amount of water to graphite, conductive carbon, thickener sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a mass ratio of 96:2:1:1 and stirring evenly.

[0271] A second slurry was prepared by adding a certain amount of water to a silicon-carbon composite material (formed by nano-silicon deposition in porous carbon pores, with a silicon content of 26%), conductive carbon, thickener sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a mass ratio of 96:2:1:1 and stirring evenly.

[0272] First, a first slurry is uniformly coated onto a 6μm thick copper foil used as a negative electrode current collector, and then dried in an oven at 85℃ to form a first negative electrode active layer loaded on the current collector. Next, a second slurry is coated onto the dried first negative electrode active layer, dried at 85℃, and then cold-pressed to form the negative electrode sheet. The thickness ratio of the first to the second negative electrode active layer is 1:9. The areal density of the negative electrode active layer is 120mg / 1540.25mm². 2 .

[0273] The rest is the same as in Example 1.

[0274] Example 10

[0275] The first slurry is prepared by adding a certain amount of water to graphite, conductive carbon, thickener sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a mass ratio of 96:2:1:1 and stirring evenly.

[0276] A second slurry was prepared by adding a certain amount of water to a silicon-carbon composite material (formed by nano-silicon deposition in porous carbon pores, with a silicon content of 31%), conductive carbon, thickener sodium hydroxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a mass ratio of 96:2:1:1 and stirring evenly.

[0277] First, a first slurry is uniformly coated onto a 6μm thick copper foil used as a negative electrode current collector, and then dried in an oven at 85℃ to form a first negative electrode active layer loaded on the current collector. Next, a second slurry is coated onto the dried first negative electrode active layer, dried at 85℃, and then cold-pressed to form the negative electrode sheet. The thickness ratio of the first to the second negative electrode active layer is 1:9. The areal density of the negative electrode active layer is 120mg / 1540.25mm². 2 .

[0278] The rest is the same as in Example 1.

[0279] Partial data and test results from Examples 8 to 10 are recorded in Table 3.

[0280] The thickness ratio in Table 3 is the thickness ratio of the first negative electrode active layer to the second negative electrode active layer.

[0281] The silicon element mass content S is the silicon element mass content in the second negative electrode active layer.

[0282] Table 3

[0283]

[0284] As shown in the table above, compared with Example 1, the use of silicon-carbon composite material in the second negative electrode active layer in Examples 8-10 can improve the kinetic performance of the battery cell. Specifically, as the total mass content of silicon in the negative electrode active layer (including the first and second negative electrode active layers) gradually increases in Examples 8-10, the kinetic performance of the battery cell gradually improves.

[0285] Examples 11 to 13 are based on Example 1, with the shell thickness and / or the ratio of pressure relief port area to discharge capacity A adjusted, and the rest are the same as Example 1. The test results are recorded in Table 4.

[0286] Table 4

[0287]

[0288] It can be seen from the above table:

[0289] Compared to the thinner casing of Example 1, the casing of Example 11 of this application is less damaged and safer during thermal runaway of a single battery cell. However, the heat dissipation of the casing of Example 11 is worse than that of Example 1, which leads to a shorter time to reach the boundary temperature during thermal runaway.

[0290] Compared with the smaller ratio of pressure relief port area to discharge capacity in Example 14, the battery cells in Examples 1 and 12-13 of this application suffer less casing damage and have better safety during thermal runaway.

[0291] Example 15

[0292] Based on Embodiment 12, the battery cell includes four fixing components 9 located at the four corners of the top of the first end cover 7. One end of each fixing component 9 is connected to the electrode assembly 6, and the other end is connected to the first end cover 7. A first airflow channel 8 is formed between the electrode assembly 6 and the first end cover 7. The ratio of the minimum airflow area to the discharge capacity of the first airflow channel 8 is 0.1 mm². 2 / Ah.

[0293] Example 16

[0294] like Figures 1A-1B As shown, based on Embodiment 15, the second end cap 10 of the battery cell includes a plastic section 12 near the electrode assembly 6. A groove is further formed inward on the plastic section 12 of the second end cap 10 to form a second airflow channel 11. The ratio of the minimum airflow area to the discharge capacity of the second airflow channel 11 is 0.07 mm². 2 / Ah.

[0295] Example 17

[0296] like Figures 2A-2BAs shown, based on Embodiment 16, the battery cell further includes two heat-resistant components 13. These two heat-resistant components 13 are disposed along the length of the first end cap 7 on opposite inner walls of the housing 14 and close to the first end cap 7. The heat-resistant components 13 are made of stainless steel. The length of the heat-resistant component 13 is equal to the length of the first end cap 7. The dimension (height) of the heat-resistant component 13 perpendicular to the bottom surface of the first end cap 7 is 3 mm. The width of the heat-resistant component 13 is 0.15 mm. The orientation of the length, width, and height is as follows: Figures 2A-2B The text is marked as such.

[0297] The specific key parameters and test results are recorded in Table 5.

[0298] Table 5

[0299]

[0300] It can be seen from the above table:

[0301] Based on Example 12, Example 15 of this application adds a first airflow channel inside the battery cell, which reduces the pressure relief during thermal runaway, thereby reducing the degree of casing damage during thermal runaway and improving safety performance.

[0302] Based on Example 15, Example 16 of this application adds a second airflow channel inside the battery cell, which further reduces the pressure relief during thermal runaway, thereby reducing the degree of casing damage during thermal runaway and improving safety performance.

[0303] Based on Example 16, Example 17 of this application adds a heat-resistant component to the casing of the battery cell, which further improves the strength and integrity of the battery casing and enhances the safety performance of the battery cell.

[0304] Examples 18 to 20 are based on Example 1, with adjustments made to the composition of the electrolyte. The specific changes are recorded in Table 6. The rest are the same as in Example 1. The test results are recorded in Table 6.

[0305] Table 6

[0306]

[0307] It can be seen from the above table:

[0308] Based on Example 1, the addition of ethylene carbonate to the electrolyte in Example 18 is beneficial to improving the kinetic performance of the battery cell.

[0309] Compared to the higher ethylene carbonate content in the electrolyte of Example 19, the thermal runaway reaction of the battery cell in Example 18 of this application is less severe, causes less damage to the casing, and is safer.

[0310] Example 21

[0311] Based on Example 7, a silicon-oxygen composite material with a silicon element mass content of 21% was used to replace the silicon-carbon composite material in Example 7 to prepare the negative electrode sheet, and the rest were the same as in Example 7.

[0312] The test results are shown in Table 7.

[0313] Table 7

[0314]

[0315] As shown in the table above, compared with the silicon-oxygen composite material used in Example 21, the silicon-carbon composite material used in Example 7 of this application results in a smaller reaction intensity during thermal runaway, less shell damage, a higher thermal runaway boundary temperature, higher safety performance, and better kinetic performance.

[0316] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, comprising an electrode assembly and a housing, wherein the electrode assembly is disposed in the inner cavity of the housing, the battery cell having a volumetric energy density ≥700Wh / L, the electrode assembly comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte contains ≤20% by mass of a sulfonylimide lithium salt; the housing comprises a shell, the shell material having a melting point of 800℃-1800℃.

2. The battery cell according to claim 1, wherein, The negative electrode includes a negative current collector and a negative active layer located on at least one side of the negative current collector. The negative active layer includes a silicon-based material, and the mass content of silicon in the negative active layer is 1%-65%.

3. The battery cell according to claim 2, wherein, The negative electrode active layer includes a first negative electrode active layer and a second negative electrode active layer. The first negative electrode active layer is located on at least one side of the negative electrode current collector, and the second negative electrode active layer is located on the side of the first negative electrode active layer away from the negative electrode current collector. The second negative electrode active layer includes the silicon-based material.

4. The battery cell according to claim 3, wherein, The battery cell includes one or more of the following characteristics: a) The silicon element has a mass content of 5%-65% in the second negative electrode active layer; b) The first negative electrode active layer includes a first graphite, which includes at least one of artificial graphite and natural graphite; optionally, the first graphite includes artificial graphite and natural graphite; further optionally, the content of natural graphite is higher than that of artificial graphite. c) The second negative electrode active layer includes a second graphite, which includes at least one of artificial graphite and natural graphite; optionally, the graphitization degree of the first graphite is lower than that of the second graphite.

5. The battery cell according to claim 3 or 4, wherein, The thickness ratio of the first active layer to the second active layer is 1:9-9:

1.

6. The battery cell according to any one of claims 2 to 5, wherein, The silicon-based material includes one or more of elemental silicon, silicon-oxygen composite materials, and silicon-carbon composite materials; Optionally, the silicon-based material includes at least the silicon-carbon composite material; More preferably, the silicon-carbon composite material satisfies one or more of the following characteristics: 1) The silicon-carbon composite material includes porous carbon and silicon-containing material dispersed in the pores of the porous carbon, and optionally the porous carbon is hard carbon; 2) The silicon content in the silicon-carbon composite material is 20%-70% or 30%-70% by mass; 3) The average particle size of the silicon-carbon composite material is 2μm-15μm or 7μm-11μm; 4) The powder resistivity of the silicon-carbon composite material at 8 MPa is 4 Ω·cm-17 Ω·cm; 5) The BET specific surface area of ​​the silicon-carbon composite material is 1.0 m². 2 / g-6.7m 2 / g.

7. The battery cell according to claim 6, wherein, In item 1), the silicon-carbon composite material further includes a carbon-containing coating layer, which is located on the surface of the porous carbon and / or the silicon-containing material.

8. The battery cell according to any one of claims 1 to 7, wherein, The mass content of the sulfonylimide lithium salt in the electrolyte is ≤10%; and / or, The electrolyte contains 0.5%-20% or 2.5%-20% or 2.5%-10% by mass; and / or, The electrolyte also contains lithium hexafluorophosphate, and the mass ratio of the sulfonamide lithium salt to the lithium hexafluorophosphate is 1:50-5:1, 1:30-4:1, or 1:20-3:

1.

9. The battery cell according to any one of claims 1 to 8, wherein, The melting point of the shell material is 900℃-1600℃ or 1200℃-1500℃; and / or, The shell material has a tensile strength of 400MPa-1400MPa or 600MPa-1040MPa at room temperature; and / or, The shell material has a tensile strength at 500℃ >300MPa and ≤1000MPa, or is 450MPa-900MPa; and / or, The shell material includes one or more of stainless steel, nickel-based alloys, titanium alloys, and titanium carbide alloys.

10. The battery cell according to any one of claims 1 to 9, wherein, The thickness of the shell is 0.1mm-1mm or 0.18mm-0.5mm.

11. The battery cell according to any one of claims 1 to 10, wherein, The housing also includes a first end cap and a second end cap disposed at opposite ends of the housing.

12. The battery cell according to claim 11, wherein, The battery cell also includes electrode terminals and a pressure relief mechanism. The pressure relief mechanism is disposed on the first end cover, and the electrode terminals are disposed on the second end cover.

13. The battery cell according to claim 12, wherein, The pressure relief mechanism includes a pressure relief port, which is used to open when the internal pressure and / or temperature of the battery cell reaches a threshold to release the internal pressure and / or heat of the battery cell; the ratio of the area of ​​the pressure relief port to the discharge capacity of the battery cell is 2 mm². 2 / Ah–10mm 2 / Ah, 4.5mm 2 / Ah–9.0mm 2 / Ah or 4.65mm 2 / Ah–9.0mm 2 / Ah, wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current.

14. The battery cell according to any one of claims 11 to 13, wherein, The electrode assembly has a first airflow channel between itself and the first end cap.

15. The battery cell according to claim 14, wherein, The ratio of the minimum airflow area of ​​the first airflow channel to the discharge capacity of the battery cell is 0.05 mm². 2 / Ah-0.155mm 2 / Ah, wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current.

16. The battery cell according to claim 14 or 15, wherein, The battery cell also includes one or more fixing components, one end of which is connected to the electrode assembly and the other end of which is connected to the first end cap, for forming the first airflow channel between the electrode assembly and the first end cap.

17. The battery cell according to any one of claims 11 to 13, wherein, The electrode assembly has a second airflow channel between it and the second end cap.

18. The battery cell according to claim 17, wherein, The ratio of the minimum airflow area of ​​the second airflow channel to the discharge capacity of the battery cell is 0.02 mm. 2 / Ah-0.11mm 2 / Ah, wherein the discharge capacity is obtained by discharging the battery cell from 4.25V to 2.5V at 1 / 3C at room temperature using a constant current.

19. The battery cell according to claim 17 or 18, wherein, The inner wall of the second end cap has an inwardly oriented groove to form the second airflow channel.

20. The battery cell according to any one of claims 11 to 19, wherein, The battery cell also includes one or more heat-resistant components, which are disposed on the inner wall of the housing and close to the first end cap along the length direction of the first end cap.

21. The battery cell according to claim 20, wherein, The length of the heat-resistant component is equal to the length of the first end cap; and / or, The dimension of the heat-resistant component along the direction perpendicular to the bottom surface of the first end cap is >0 and ≤4cm or >0 and ≤1cm; and / or, The width of the heat-resistant component is greater than 0 and less than or equal to 1 mm, and the direction of the width is perpendicular to the direction of the length.

22. The battery cell according to claim 20 or 21, wherein, The heat-resistant components are made of one or more of the following materials: stainless steel, alumina, silicon nitride, and polyimide.

23. The battery cell according to any one of claims 1 to 22, wherein, The volumetric energy density of the battery cell is ≥720Wh / L, ≥740Wh / L, or 740–850Wh / L.

24. The battery cell according to any one of claims 1 to 23, wherein, The positive electrode includes a positive current collector and a positive active layer located on at least one side of the positive current collector; The positive electrode active layer includes lithium nickel cobalt manganese oxide material; in the lithium nickel cobalt manganese oxide material, the molar ratio of Ni element in the total of Ni, Co and Mn elements is 0.8:1-0.97:1 or 0.85:1-0.95:

1.

25. The battery cell according to claim 24, wherein, The lithium nickel cobalt manganese oxide material includes Li a Ni x Co y Mn 1-x-y- z M z O2, wherein 0.7≤a≤1.1, 0.8≤x≤0.97, 0<y<1, 0.001≤z≤0.01 and 0<1-xyz<1, and M includes one or more elements selected from Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, B, Mg, Zn, Ca, and Ce.

26. The battery cell according to any one of claims 1 to 25, wherein, The electrolyte also includes cyclic ester compounds.

27. The battery cell according to claim 26, wherein, The mass content of the cyclic ester compound in the electrolyte is 3%-35%, 3%-30%, or 5%-20%.

28. The battery cell according to claim 26 or 27, wherein, The cyclic ester compounds include one or more of ethylene carbonate, fluoroethylene carbonate, and vinylene carbonate.

29. A battery device comprising a battery cell according to any one of claims 1 to 28.

30. An electrical device comprising a battery cell as described in any one of claims 1 to 28 or a battery device as described in claim 29.

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