A battery, a battery assembly and an electric device

Abstract

The application discloses a battery, which comprises a shell, an electrode assembly and an electrolyte, the shell has a containing cavity, the electrode assembly and the electrolyte are arranged in the containing cavity; the electrode assembly comprises a negative electrode sheet, the coating amount of the negative electrode sheet is W 负 , unit: g; the electrolyte comprises lithium hexafluorophosphate and lithium bisfluorosulfonylimide, the molar concentration of the lithium hexafluorophosphate in the electrolyte is M1, unit: mol / L, the molar concentration of the lithium bisfluorosulfonylimide in the electrolyte is M2, unit: mol / L, the volume of the shell is V, unit: cm 3 ; wherein: 0.7 <= (W 负 / V + 0.38) * (1.43M1 + 2.6M2) <= 1.65. The battery has good cycle performance, low risk of thermal runaway or thermal diffusion, high safety performance and long service life.

Description

Technical Field

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

[0002] Lithium-ion batteries are currently widely used in electric vehicles, energy storage systems, and mobile devices, especially in power batteries, where development has been rapid. While existing methods for improving lithium-ion battery performance can enhance it to some extent, they also introduce problems, such as failing to balance cycle life and safety performance, and potentially leading to thermal runaway. Therefore, lithium-ion battery technologies still require further improvement. Summary of the Invention

[0003] This application aims to address at least one of the technical problems existing in the prior art. Therefore, one object of the present invention is to provide a battery that has good cycle performance and a low risk of thermal runaway or thermal propagation, i.e., high battery safety and long service life.

[0004] According to a first aspect of this application, a battery is provided, comprising: a housing, an electrode assembly, and an electrolyte, wherein the housing has a receiving cavity, and the electrode assembly and the electrolyte are both disposed within the receiving cavity; the electrode assembly includes a negative electrode sheet, and the amount of coating on the negative electrode sheet is W. 负 The unit is g; the electrolyte comprises lithium hexafluorophosphate and lithium difluorosulfonyl imide, the molar concentration of lithium hexafluorophosphate in the electrolyte is M1, the unit is mol / L, the molar concentration of lithium difluorosulfonyl imide in the electrolyte is M2, the unit is mol / L, and the volume of the shell is V, the unit is cm. 3 Where: 0.7≤(W) 负 / V +0.38)×(1.43M1+2.6M2)≤1.65.

[0005] According to the battery embodiments of this application, the combined use of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate can improve battery life performance. Simultaneously, a reasonable combination design is implemented for the battery's heat generation / thermal conductivity factors: battery size, amount of negative electrode auxiliary materials, and concentration of lithium salt in the electrolyte. This controls the heat generation from the reaction between the negative electrode and the electrolyte per unit volume of the battery, reducing the probability of thermal runaway or thermal diffusion, and comprehensively controlling the heat generation to 0.7 ≤ (W). 负 The formula / V +0.38)×(1.43M1+2.6M2)≤1.65 enables the battery to have good cycle performance, low risk of thermal runaway or thermal diffusion, high battery safety performance, and long service life.

[0006] According to some embodiments of this application, the shell structure is rectangular.

[0007] According to some embodiments of this application, the length of the shell is L in cm, the width of the shell is H in cm, and the thickness of the shell is D in cm, wherein L > H and H > D.

[0008] According to some embodiments of this application, L / H = (2-20):1, H / D = (5-10):1.

[0009] According to some embodiments of this application, L = 40cm-250cm.

[0010] According to some embodiments of this application, 0.42 ≤ W 负 / V≤0.48.

[0011] According to some embodiments of this application, 0.6 ≤ M1 + M2 ≤ 1.4.

[0012] According to some embodiments of this application, 0 < M1 ≤ 1.4 mol / L.

[0013] According to some embodiments of this application, 0 < M2 ≤ 1.4 mol / L.

[0014] According to some embodiments of this application, the electrode assembly further includes a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material, the positive electrode active material comprising lithium iron phosphate and / or lithium manganese iron phosphate.

[0015] According to some embodiments of this application, the negative electrode sheet includes a negative electrode active material, which includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate.

[0016] According to some embodiments of this application, the negative electrode sheet includes a negative electrode active material, which includes graphite.

[0017] According to some embodiments of this application, the electrolyte further includes a solvent, which includes at least one of carbonate solvents, ether solvents, and carboxylic acid ester solvents; the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the ether solvent includes dimethyl glycol ether, diethyl glycol ether, 1,3-dioxolane, dimethoxymethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, isosorbide dimethyl ether, dipropylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, The solvent comprises at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,3,3-tetrafluoropropyl dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropylmethyl ether, and 2,2,2-trifluoroethyl ether; the carbonate solvent comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and ethyl acetate; the carboxylic acid ester solvent comprises at least one of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0018] According to some embodiments of this application, the electrolyte further includes additives, the additives including at least one of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, and methylene disulfonate.

[0019] The second aspect of this application provides a battery assembly that, by utilizing the battery described in the first aspect of this application, has a longer service life while significantly improving safety performance.

[0020] The third aspect of this application provides an electrical device that, by utilizing a battery assembly according to the second aspect of this application, has a longer service life and significantly improved safety performance. Detailed Implementation

[0021] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are exemplary and used to explain the invention, and should not be construed as limiting the invention.

[0022] This application is based on the inventor's discovery and understanding of the following facts and problems: Currently, the electrolyte of lithium-ion batteries mainly consists of lithium salts, solvents, and additives. Lithium hexafluorophosphate (LiPF6) has become the main conductive lithium salt in commercially available lithium-ion batteries due to its excellent overall performance. Lithium hexafluorophosphate has high conductivity, high oxidation potential, and can form an SEI film on the negative electrode surface. However, lithium hexafluorophosphate and its decomposition product PF5... - Lithium difluorosulfonylimide reacts with trace amounts of water in the electrolyte to generate hydrogen fluoride. This hydrogen fluoride corrodes the SEI film and reacts with lithium-intercalated graphite, causing the negative electrode active material structure to collapse, inducing lithium dendrite growth and capacity decay, thus accelerating battery life degradation. Lithium difluorosulfonylimide exhibits good thermal stability, and its decomposition products contain LiF and organic sulfur compounds (such as sulfonyl groups), which can form a denser and more ionicly conductive SEI film on the negative electrode surface. This reduces the decomposition of lithium hexafluorophosphate and the damage of hydrogen fluoride to lithium-intercalated graphite. Using lithium difluorosulfonylimide in combination with lithium hexafluorophosphate can significantly improve battery life performance.

[0023] Lithium difluorosulfonylimide (LiDIEM) contains numerous SF and SN bonds. The breaking of these bonds leads to a significant increase in heat generation. Furthermore, LiDIEM readily undergoes a reduction reaction with lithium-intercalated graphite at high temperatures (approximately 210°C), resulting in a substantial increase in battery heat generation and a rapid change in the battery's temperature rise rate. This can induce thermal runaway. In electrical equipment, thermal runaway in one battery often triggers thermal runaway in adjacent batteries, a phenomenon known as thermal diffusion, leading to the entire electrical equipment malfunctioning and potentially causing serious consequences such as fires and explosions. The safety issues arising from the combined use of LiDIEM and LiHexafluorophosphate are urgent problems that need to be addressed.

[0024] Further research revealed that the heat generated in the aforementioned battery system during operation primarily originates from the interaction between lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate in the negative electrode and electrolyte. Battery size also influences the internal heat transfer rate and heat output intensity. The inventors of this application have achieved a reasonable combination design of the aforementioned heat-generating / thermal-conducting factors: battery size, amount of negative electrode additives, and concentration of lithium salts in the electrolyte. This controls the heat generated by the reaction between the negative electrode and electrolyte per unit volume, reducing the probability of thermal runaway or thermal diffusion, resulting in a safer and longer-lasting battery.

[0025] A first aspect of this application provides a battery. According to an embodiment of this application, the battery includes: a housing, an electrode assembly, and an electrolyte. The housing has a receiving cavity, and both the electrode assembly and the electrolyte are disposed within the receiving cavity. The electrode assembly includes a negative electrode sheet, and the amount of material applied to the negative electrode sheet is W. 负The unit is g; the electrolyte comprises lithium hexafluorophosphate and lithium difluorosulfonyl imide, the molar concentration of lithium hexafluorophosphate in the electrolyte is M1, the unit is mol / L, the molar concentration of lithium difluorosulfonyl imide in the electrolyte is M2, the unit is mol / L, and the volume of the shell is V, the unit is cm. 3 Where: 0.7≤(W) 负 / V +0.38)×(1.43M1+2.6M2)≤1.65.

[0026] This application improves battery life performance by using lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate in combination. Simultaneously, it rationally designs the heat generation / thermal conductivity factors of the battery—battery size, amount of negative electrode additives, and concentration of lithium salts in the electrolyte—to control the heat generation from the reaction between the negative electrode and the electrolyte per unit volume, reducing the probability of thermal runaway or thermal diffusion, and comprehensively controlling the heat generation to 0.7 ≤ (W). 负 The formula / V +0.38)×(1.43M1+2.6M2)≤1.6 enables the battery to have good cycle performance, low risk of thermal runaway or thermal diffusion, high battery safety performance, and long service life.

[0027] As an example, (W 负 The range of ( / V+0.38)×(1.43M1+2.6M2) can be 0.8-1.5, 0.9-1.4, 1.0-1.3. As an example, (W 负 The formula / V+0.38)×(1.43M1+2.6M2) can be 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, etc., which can further reduce the probability of battery thermal runaway or thermal diffusion, resulting in high safety and good cycle performance and long service life.

[0028] According to the embodiments of this application, the casing is rectangular. The casing only needs to be generally rectangular; it does not necessarily have to be strictly rectangular. Compared to cylindrical or irregularly shaped cells with more curved surfaces, rectangular batteries can be customized in size according to different product requirements. Especially in the field of new energy vehicles, the battery size can be adjusted according to the vehicle layout to achieve better space integration and performance matching. The regular shape of the rectangular battery can evenly distribute external pressure. Combined with aluminum / steel casing materials, it can effectively resist physical impacts such as compression and puncture. It also facilitates modular assembly, improving the space utilization of battery modules. It is suitable for large-scale integrated applications and can be directly integrated into the battery pack through a "module-less" design, reducing structural redundancy and improving volume utilization.

[0029] According to the embodiments of this application, the length of the casing is L (cm), the width of the casing is H (cm), and the thickness of the casing is D (cm), where L > H and H > D. Therefore, the elongated battery can directly serve as the battery pack frame, reducing redundant supports and improving overall compressive strength.

[0030] According to the implementation method of this application, L / H = (2-20):1, H / D = (5-10):1. The range of L / H can be 3-18, 5-15, 6-12, 7-11, 8-10 as examples; specifically, L / H can be 3, 5, 7, 9, 10, 12, 14, 16, 18, etc. The range of H / D can be 6-9, 7-8; specifically, H / D can be 5, 6, 7, 8, 9, 10, etc. Therefore, the overall battery size is reasonable, the battery has strong heat dissipation capacity, and when flat batteries directly form the battery module structure, the assembly process at the module level in traditional battery packs can be eliminated, making the battery itself the load-bearing and supporting unit of the battery module. Through close arrangement to form a structural skeleton, it is beneficial for overall arrangement within the battery module, improving the space utilization rate within the battery module, increasing the energy density within the battery module, and thus enhancing the range within the battery module.

[0031] According to the embodiments of this application, L = 40cm-150cm. The range of L can be 50cm-220cm, 60cm-200cm, 70cm-180cm, 80cm-160cm, 90cm-140cm, or 100cm-120cm. As an example, L can specifically be 50cm, 70cm, 90cm, 110cm, 130cm, or 150cm. Therefore, the battery length is reasonable and suitable for assembly into battery modules for use in vehicles or energy storage devices. The battery itself can serve as a load-bearing and support unit for the battery module. The self-supporting design reduces redundant components such as module brackets, simplifies the production process, improves overall compressive strength, and increases the space utilization rate of the battery module.

[0032] According to the embodiments of this application, 0.42 ≤ W 负 / V≤0.48. Where W 负 / V can range from 0.43 to 0.47, or from 0.44 to 0.46. As an example, W... 负 The specific values ​​for / V can be 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, etc. Specifically, by controlling the mass of the negative electrode coating layer per unit volume within the above range, lithium-ion batteries can achieve high energy density while significantly improving safety and effectively reducing the probability of thermal runaway and thermal diffusion.

[0033] According to embodiments of this application, the lithium salt in the electrolyte may include lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. Lithium hexafluorophosphate can provide lithium ions for the lithium-ion battery, support electrolyte stability and electrochemical reactions, help form a protective SEI film, improve conductivity, and enhance the safety of the lithium-ion battery. Lithium bis(fluorosulfonyl)imide, on the other hand, has high conductivity and excellent electrochemical stability. Using lithium bis(fluorosulfonyl)imide in combination with lithium hexafluorophosphate in the electrolyte can significantly improve electrolyte conductivity, reduce viscosity, reduce battery impedance, improve lithium-ion battery power performance, and extend battery life. Furthermore, lithium bis(fluorosulfonyl)imide can stabilize the decomposition product PF5 of lithium hexafluorophosphate, reduce the HF content and dissolved iron content in the lithium-ion battery system, and extend the life of the lithium-ion battery.

[0034] According to the embodiments of this application, the molar concentration M1 of lithium hexafluorophosphate in the electrolyte satisfies: 0 < M1 ≤ 1.4. The range of M1 can be 0.1-1.3, 0.2-1.1, 0.3-0.9, 0.4-0.8, 0.5-0.7. As an example, M1 can specifically be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, etc. A molar concentration of lithium hexafluorophosphate in the electrolyte within the above range can provide lithium ions for the lithium-ion battery, support the stability of the electrolyte and electrochemical reactions, help form a protective SEI film, improve conductivity, and enhance the safety of the lithium-ion battery. At the same time, by coordinating with the battery size, the amount of coating on the negative electrode, and the molar concentration of lithium bis(fluorosulfonyl)imide in the electrolyte, the energy density of lithium-ion batteries can be improved while enhancing their thermal stability and reducing the risk of thermal runaway.

[0035] According to the embodiments of this application, the molar concentration M2 of lithium bis(fluorosulfonyl)imide in the electrolyte satisfies: 0 < M2 ≤ 1.4. The range of M2 can be 0.1-1.3, 0.2-1.1, 0.3-0.9, 0.4-0.8, 0.5-0.7. As an example, M2 can specifically be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, etc. A molar concentration of lithium bis(fluorosulfonyl)imide in the electrolyte within the above range can effectively improve the conductivity of the electrolyte, reduce viscosity, thereby reducing battery impedance, improving the power performance of lithium-ion batteries, and extending battery life. At the same time, by coordinating with the battery size, the amount of coating on the negative electrode, and the molar concentration of lithium hexafluorophosphate in the electrolyte, the energy density of lithium-ion batteries can be improved while enhancing their thermal stability and reducing the risk of thermal runaway.

[0036] According to the embodiments of this application, M1 and M2 satisfy: 0.6 ≤ M1 + M2 ≤ 1.4. The range of M1 + M2 can be 0.7-1.4, 0.8-1.3, 0.9-1.2, 1.0-1.1. As an example, M1 + M2 can specifically be 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, etc. When the molar concentration of lithium salt in the electrolyte is within the above range, the electrolyte has high conductivity and low viscosity, which is beneficial for reducing the internal resistance of lithium-ion batteries and improving their power performance. Simultaneously, it can synergistically work with other aspects of lithium-ion batteries to reduce the risk of thermal runaway and improve their thermal stability and safety performance.

[0037] According to embodiments of this application, the electrode assembly further includes a positive electrode sheet, which comprises a positive electrode active material. The positive electrode active material may include at least one of the following: layered structure positive electrode active materials (e.g., nickel-cobalt-manganese ternary positive electrode materials, nickel-cobalt-aluminum ternary positive electrode materials, lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium-rich layered and rock salt phase layered materials), olivine-type phosphate active materials (e.g., lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, etc.), and spinel structure positive electrode active materials (e.g., spinel lithium manganese oxide, spinel lithium nickel manganese oxide, lithium-rich spinel lithium manganese oxide, and lithium nickel manganese oxide, etc.). It is understood that the aforementioned positive electrode active material may further include doping elements and a coating layer.

[0038] According to embodiments of this application, the positive electrode active material includes lithium iron phosphate and / or lithium manganese iron phosphate. Therefore, the lithium-ion battery exhibits better cycle stability and safety performance. Furthermore, lithium iron phosphate and / or lithium manganese iron phosphate positive electrode active materials are well-compatible with electrolytes containing lithium hexafluorophosphate and lithium difluorosulfonylimide, resulting in batteries with superior overall performance.

[0039] According to embodiments of this application, the positive electrode sheet may include a current collector and a positive electrode coating layer disposed on at least one side of the current collector. The positive electrode coating layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. Additives with specific functions and effects, such as positive electrode lithium supplements, film-forming additives, flame retardants, and high / low temperature stabilizers, may also be added as needed.

[0040] According to embodiments of this application, the positive current collector can be a metal current collector or a composite current collector. For example, metal current collectors include, but are not limited to, aluminum foil current collectors; composite current collectors may include a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.) and a metal layer (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) formed on at least one surface of the polymer material base film.

[0041] According to embodiments of this application, the positive electrode adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. This allows for better adhesion of the positive electrode active material to the positive electrode current collector, resulting in stronger adhesion and reducing the likelihood of problems such as positive electrode dressing detachment.

[0042] According to embodiments of this application, the positive electrode conductive agent may include at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers. This effectively improves conductivity, reduces internal resistance, and enhances the electrochemical performance of lithium-ion batteries.

[0043] According to the embodiments of this application, the specific type of positive electrode lithium replenishing agent is not particularly limited, as long as it can effectively perform the lithium replenishing function. In some embodiments, the positive electrode lithium replenishing agent includes at least one of Li5FeO4, Li2O, Li2CO3, and LiNO3. Therefore, it can fully exert the lithium replenishing function, improve the energy density and cycle life of the battery, and at the same time, it can work in conjunction with other factors to greatly reduce the risk of thermal runaway and thermal diffusion in lithium-ion batteries, thereby improving the safety performance of lithium-ion batteries.

[0044] According to an embodiment of this application, the negative electrode sheet includes a negative electrode active material, which includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, and lithium titanate.

[0045] According to the embodiments of this application, the negative electrode active material includes graphite. Graphite has a high level of industrial maturity, low cost, strong compatibility with the positive electrode, and is suitable for large-scale production.

[0046] According to the embodiments of this application, the negative electrode sheet may include a negative electrode current collector and a negative electrode dressing layer disposed on at least one side of the negative electrode current collector. The negative electrode dressing layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. Additives with specific functions and effects, such as thickeners, film-forming additives, flame retardants, high-temperature / low-temperature stabilizers, etc., may also be added as needed.

[0047] According to embodiments of this application, the negative electrode current collector can be a metal current collector or a composite current collector. For example, metal current collectors include, but are not limited to, copper foil current collectors; composite current collectors may include a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.) and a metal layer (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) formed on at least one surface of the polymer material base layer.

[0048] According to embodiments of this application, the negative electrode binder may include, but is not limited to, 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).

[0049] According to embodiments of this application, the negative electrode conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0050] According to embodiments of this application, the electrolyte further includes a solvent, which may include at least one of carbonate solvents, ether solvents, and carboxylic acid ester solvents. Specifically, the carbonate solvent may include at least one of ethylene carbonate, propylene carbonate, butenyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the ether solvent includes ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,3-dioxolane, dimethoxymethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, isosorbide dimethyl ether, dipropylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl. The solvent comprises at least one of the following: ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,3,3-tetrafluoropropyl dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropylmethyl ether, and 2,2,2-trifluoroethyl ether; the carbonate solvent comprises at least one of the following: ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and ethyl acetate; the carboxylic acid ester solvent comprises at least one of the following: methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0051] According to embodiments of this application, the electrolyte further includes additives, and the film additives may include at least one selected from vinylene carbonate, fluoroethylene carbonate, propylene sulfite, and methane disulfonate. This facilitates the formation of an SEI film on the negative electrode surface, reduces side reactions, and improves the electrochemical performance of the lithium-ion battery.

[0052] According to the embodiments of this application, the electrode assembly can be a wound electrode core (i.e., the positive electrode sheet, negative electrode sheet and separator are stacked and then wound to form the electrode core), or a stacked electrode core (i.e., the positive electrode sheet, negative electrode sheet and separator are stacked to form the electrode core).

[0053] The second aspect of this application provides a battery assembly that, by utilizing the battery according to the first aspect of this application, has a longer service life while significantly improving safety performance.

[0054] According to embodiments of this application, the specific type of battery assembly is not particularly limited; the battery assembly can be a battery module, a battery pack, etc. In some embodiments, the batteries can be assembled into a battery module, and the number of batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, the batteries 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 based on the application and capacity of the battery pack.

[0055] The third aspect of this application provides an electrical device that, by utilizing a battery assembly according to the second aspect of this application, has a longer service life and significantly improved safety performance.

[0056] According to the embodiments of this application, the specific type of electrical equipment is not particularly limited, and it can be any device that uses a lithium-ion battery as a power source or energy storage unit. As examples, electrical equipment includes, but is not limited to, 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.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, etc.

[0057] It is understandable that, in addition to the battery mentioned above, the electrical device also includes other necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0058] The embodiments of this application are described in detail below. The amount of coating on the negative electrode sheet and the molar concentrations of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI) in the electrolyte can be obtained by disassembling the battery.

[0059] The following parameters are considered: Auxiliary material quantity for the negative electrode: Disassemble the battery, separate all negative electrode sheets, and measure their weight, length, and width. Cut 15mm diameter foil discs from the tab area using a foil cutter, and measure the weight of the cut foil discs. Based on the weight and area of ​​the cut foil discs, as well as the length and width of the negative electrode sheets, calculate the total weight of the foil material in the negative electrode sheet. Auxiliary material quantity for the negative electrode sheet = electrode sheet weight - total weight of electrode foil material. Molar concentrations of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI) in the electrolyte: Disassemble the battery and collect the free electrolyte. Quantitatively determine the PF6- and FSI- contents using ion chromatography (IC) with a standard curve. Based on the measured contents and the extracted electrolyte volume, the molar concentrations of LiFSI and LiPF6 in the electrolyte can be calculated. Example

[0060] Positive electrode preparation: Polyvinylidene fluoride (binder) is added to N-methylpyrrolidone (solvent) and stirred to dissolve. Then, conductive carbon black (conductive agent) and lithium iron phosphate (positive electrode active material) are added and kneaded thoroughly to obtain a positive electrode slurry (lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride in a weight ratio of 96.8:0.8:2.4). The above positive electrode slurry is uniformly coated on current collector aluminum foil, and after baking and rolling, a positive electrode sheet is obtained.

[0061] Negative electrode preparation: Graphite (negative electrode active material), conductive carbon black (conductive agent), SBR (binder), and CMC (thickener) are mixed in a mass ratio of 93:1:4:2, and deionized water is added as a solvent. The mixture is kneaded thoroughly to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on a current collector copper foil, and after baking and rolling, a negative electrode sheet is obtained. The amount of auxiliary materials for this negative electrode sheet is 364g.

[0062] Electrolyte: Ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. Lithium hexafluorophosphate and lithium difluorosulfonyl imide were added to the above mixed solvent (the molar concentration of lithium hexafluorophosphate was 0.77 mol / L, and the molar concentration of lithium difluorosulfonyl imide was 0.23 mol / L). Ethylene carbonate was added as an additive (ethylene carbonate accounted for 4% by mass) to obtain the electrolyte.

[0063] Separator: A commercially available PE copolymer microporous membrane with a thickness of 11μm is used.

[0064] Assembly: The positive electrode, separator, and negative electrode are stacked to form a battery assembly. The battery assembly is then placed into a rectangular casing with a length of 43.5 cm, a width of 10.5 cm, and a thickness of 1.81 cm. After drying, electrolyte is injected. The battery is obtained through processes such as encapsulation, settling, formation, aging, and secondary encapsulation.

[0065] The preparation of Examples 2-22 and Comparative Examples 1-9 was the same as that of Example 1, with the differences shown in Table 1.

[0066] Table 1

[0067] L / cm H / cm D / cm <![CDATA[V / cm 3 ]]> W negative / g <![CDATA[M1 / mol / L]]> <![CDATA[M2 / mol / L]]> p-value Example 1 43.5 10.5 1.81 826.7 364 0.77 0.23 1.39 Example 2 43.5 10.5 1.81 826.7 364 0.51 0.49 1.64 Example 3 43.5 10.5 1.81 826.7 364 1 0.13 1.45 Example 4 43.5 10.5 1.81 826.7 364 0.59 0.01 0.71 Example 5 43.5 10.5 1.81 826.7 364 0.6 0.05 0.81 Example 6 43.5 10.5 1.81 826.7 364 0.6 0.2 1.13 Example 7 96 9 1.35 1166.4 534 0.88 0.12 1.32 Example 8 96 9 1.35 1166.4 534 0.6 0.3 1.37 Example 9 96 9 1.35 1166.4 534 0.4 0.2 0.91 Example 10 96 9 1.35 1166.4 534 1 0.2 1.63 Example 11 96 9 1.35 1166.4 555 0.6 0.3 1.40 Example 12 96 9 1.35 1166.4 580 0.6 0.3 1.44 Example 13 96 9 1.35 1166.4 470 0.88 0.12 1.23 Example 14 96 9 1.35 1166.4 534 1.3 0.04 1.64 Example 15 96 9 1.35 1166.4 500 1.41 0.01 1.65 Example 16 96 9 1.35 1166.4 534 0.4 0.15 0.81 Example 17 50 18 2.1 1890.0 867 0.9 0.1 1.30 Example 18 50 18 2.1 1890.0 867 0.8 0.3 1.61 Example 19 50 18 2.1 1890.0 867 0.6 0.4 1.59 Example 20 50 18 2.1 1890.0 867 0.6 0.05 0.83 Example 21 150 12.5 2 3750.0 1716 0.8 0.2 1.39 Example 22 140 7.5 1.5 1575.0 673 0.9 0.1 1.25 Comparative Example 1 43.5 10.5 1.81 826.7 364 0.3 0 0.35 Comparative Example 2 43.5 10.5 1.81 826.7 364 1 0.5 2.24 Comparative Example 3 43.5 10.5 1.81 826.7 364 0.6 0.6 1.98 Comparative Example 4 96 9 1.35 1166.4 534 0.1 0.1 0.34 Comparative Example 5 96 9 1.35 1166.4 534 0.4 0.05 0.59 Comparative Example 6 96 9 1.35 1166.4 534 1.3 0.5 2.65 Comparative Example 7 96 9 1.35 1166.4 534 0.5 1 2.78 Comparative Example 8 50 18 2.1 1890.0 867 1 0.3 1.85 Comparative Example 9 50 18 2.1 1890.0 867 0.1 0.2 0.56

[0068] Note: P-value = (W 负 / V+0.38)×(1.43M1+2.6M2).

[0069] Performance testing:

[0070] Needle penetration test: The test was conducted in accordance with the method of "GB / T 31485-2015 Safety Requirements and Test Methods for Power Batteries for Electric Vehicles". The specific needle penetration procedure is as follows: ① Charging: At room temperature, the batteries prepared in each example and comparative example were first discharged to 2.0V at 1C, rested for 5 minutes, then discharged to 2.0V at 0.2C, rested for 30 minutes, then charged to 3.65V at 1C, rested for 5 minutes, and then charged to 3.65V at 0.2C; ② Needle penetration: A high-temperature resistant steel needle with a diameter taper of 45° was used to penetrate the lithium-ion battery plate at a speed of (25±5) mm / s. The penetration position should be close to the geometric center of the pierced surface. The steel needle was left in the lithium-ion battery for observation for 1 hour.

[0071] High-temperature cycling test: ① Place the battery in a 60±3℃ oven for 4 hours. ② Charge the battery to 3.65V at 1C at 60±3℃, let it rest for 5 minutes, and then charge it to 3.65V at 0.2C. ③ Let the battery rest for 30 minutes at 60±3℃. ④ Discharge the battery to 2.0V at 1C at 60±3℃, let it rest for 5 minutes, and then discharge it to 2.0V at 0.2C. ⑤ Let the battery rest for 30 minutes at 60±3℃. ⑥ Cycle steps ② to ⑤ 1000 times and record the capacity retention rate of the lithium-ion battery.

[0072] DC internal resistance test: ① Adjust SOC (State of Charge): At room temperature, charge the battery to 3.65V at 1C, let it rest for 5 minutes, then charge it to 3.65V at 0.2C, let it rest for 30 minutes; then discharge it at 0.5C for 90 minutes; ② Let it rest for 2 hours; ③ Impedance test: Discharge the battery at 1.5C for 10 seconds; ④ Record the last voltage data of ② and ③ as V1 and V2 respectively, and calculate the DCIR value according to the following formula: DCIR discharge = (V1-V2) / 1.5C capacity × 1000 (unit: mΩ).

[0073] The performance test results of each embodiment and comparative example are shown in Table 2:

[0074] Table 2

[0075] Capacity retention rate after 1000 cycles at 60℃ Discharge DCIR / mΩ Needle prick test results Example 1 84.8% 0.77 Okay, it won't catch fire or explode. Example 2 88.0% 0.74 Okay, it won't catch fire or explode. Example 3 84.5% 0.78 Okay, it won't catch fire or explode. Example 4 83.5% 0.85 Okay, it won't catch fire or explode. Example 5 84.2% 0.83 Okay, it won't catch fire or explode. Example 6 84.7% 0.79 Okay, it won't catch fire or explode. Example 7 85.4% 1.15 Okay, it won't catch fire or explode. Example 8 86.1% 1.11 Okay, it won't catch fire or explode. Example 9 85.3% 1.21 Okay, it won't catch fire or explode. Example 10 85.8% 1.14 Okay, it won't catch fire or explode. Example 11 84.0% 1.06 Okay, it won't catch fire or explode. Example 12 82.3% 1.01 Okay, it won't catch fire or explode. Example 13 83.7% 1.25 Okay, it won't catch fire or explode. Example 14 85.0% 1.20 Okay, it won't catch fire or explode. Example 15 83.3% 1.24 Okay, it won't catch fire or explode. Example 16 82.9% 1.31 Okay, it won't catch fire or explode. Example 17 85.2% 0.54 Okay, it won't catch fire or explode. Example 18 85.9% 0.52 Okay, it won't catch fire or explode. Example 19 86.2% 0.51 Okay, it won't catch fire or explode. Example 20 84.0% 0.57 Okay, it won't catch fire or explode. Example 21 84.3% 0.39 Okay, it won't catch fire or explode. Example 22 83.8% 1.04 Okay, it won't catch fire or explode. Comparative Example 1 77.0% 0.94 Okay, it won't catch fire or explode. Comparative Example 2 85.0% 0.86 NG, explosion-proof valve opened, battery out of control Comparative Example 3 88.0% 0.74 NG, explosion-proof valve opened, battery out of control Comparative Example 4 75.0% 1.70 Okay, it won't catch fire or explode. Comparative Example 5 79.6% 1.35 Okay, it won't catch fire or explode. Comparative Example 6 79.0% 1.39 NG, explosion-proof valve opened, battery out of control Comparative Example 7 88.0% 1.07 NG, explosion-proof valve opened, battery out of control Comparative Example 8 86.0% 0.54 NG, explosion-proof valve opened, battery out of control Comparative Example 9 76.8% 0.65 Okay, it won't catch fire or explode.

[0076] As can be seen from the test data in Table 2, the embodiment satisfies: (W 负 Batteries with a value of (V +0.38)×(1.43M1+2.6M2) in the range of 0.7-1.65 exhibit good cycle performance and a low risk of thermal runaway or thermal propagation, meaning they have high safety performance and a long service life. Batteries that do not meet these ranges cannot simultaneously achieve high-temperature cycling and safety.

[0077] In the description of this specification, the references to terms such as "implementation," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0078] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A battery, characterized by, include: The device comprises a housing, an electrode assembly, and an electrolyte, wherein the housing has a receiving cavity, and the electrode assembly and the electrolyte are both disposed within the receiving cavity; The electrode assembly includes a negative electrode sheet, the application amount of which is W 负 , unit g; The electrolyte comprises lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the molar concentration of lithium hexafluorophosphate in the electrolyte is M1 (mol / L) and the molar concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is M2 (mol / L). The volume of the housing is V, in cm 3 ; wherein: 0.7 < (W 负 V + 0.38) x (1.43M1+ 2.6M2) < 1.

65.

2. The battery of claim 1, wherein, The shell structure is rectangular.

3. The battery of claim 1, wherein, The length of the shell is L, the width of the shell is H, and the thickness of the shell is D, where L > H and H > D.

4. The battery of claim 3, wherein, L / H= (2-20): 1, H / D= (5-10):

1.

5. The battery of claim 3, wherein, L = 40cm - 150cm.

6. The battery of any one of claims 1-4, wherein, 0.42 < W 负 V < 0.

48.

7. The battery of any one of claims 1-4, wherein, 0.6≤M1+M2≤1.

4.

8. The battery of any one of claims 1-4, wherein, 0 < M1 ≤ 1.4 mol / L.

9. The battery of any one of claims 1-4, wherein, 0 < M2 ≤ 1.4 mol / L.

10. The battery of any one of claims 1-4, wherein, The electrode assembly further includes a positive electrode sheet, which includes a positive electrode active material, including lithium iron phosphate and / or lithium manganese iron phosphate.

11. The battery of any one of claims 1-4, wherein, The negative electrode sheet includes a negative electrode active material, which includes at least one of graphite, soft carbon, hard carbon, carbon fiber, silicon-based materials, tin-based materials, and lithium titanate.

12. The battery of any one of claims 1-4, wherein, The electrolyte also includes a solvent, which includes at least one of carbonate solvents, ether solvents, and carboxylic acid ester solvents; The carbonate solvents include at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate. The ether solvents include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,3-dioxolane, dimethoxymethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, isosorbide dimethyl ether, dipropylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, and 1,1,2,2-tetrafluoroethyl ether. At least one of ethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,3,3-tetrafluoropropyl dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropylmethyl ether, and 2,2,2-trifluoroethyl ether; the carbonate solvent includes at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and ethyl acetate. The carboxylic acid ester solvents include at least one of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

13. The battery of any one of claims 1-4, wherein, The electrolyte also includes additives, which include at least one of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, and methylene disulfonate.

14. The battery of claim 8, wherein, 0.4 mol / L ≤ M1 ≤ 1.4 mol / L.

15. The battery of claim 9, wherein, 0.01 mol / L≤ M2≤0.5 mol / L.

16. A battery assembly characterized by, The battery includes any one of claims 1-15.

17. An electrical device, characterized by The battery assembly of claim 16.