Battery, energy storage apparatus, and energy storage system

Abstract

Provided are a battery, an energy storage apparatus, and an energy storage system. The battery comprises: an electrode assembly, the electrode assembly comprising a positive electrode sheet, a separator, and a negative electrode sheet; an electrolyte, the electrolyte comprising an electrolyte salt and an organic solvent, the organic solvent comprising a cyclic carbonate and a chain carbonate, and a mass ratio of the cyclic carbonate to the chain carbonate being A; and a casing assembly, the casing assembly comprising a first end cover assembly, a casing body, and a second end cover assembly, the first end cover assembly comprising a first top cover and a first explosion-proof valve connected to each other, and the first top cover being electrically connected to the positive electrode sheet; the second end cover assembly comprises a second top cover, a negative terminal, and a second explosion-proof valve, the negative terminal being electrically connected to the negative electrode sheet; an area ratio of the first explosion-proof valve to the second explosion-proof valve is B; and the battery satisfies the relational expression: 2.23≤B / A≤17.65.

Description

Batteries, energy storage devices and energy storage systems

[0001] This application claims priority to Chinese Patent Application No. 202410924936.7, filed on July 11, 2024, entitled "Battery, Energy Storage Device and Energy Storage System", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of energy storage, specifically to a battery, an energy storage device, and an energy storage system. Background Technology

[0003] With the continuous development of lithium-ion battery technology, lithium-ion batteries have advantages over other types of batteries such as lead-acid and nickel-cadmium batteries, including higher specific capacity, no memory effect, higher operating voltage, faster charging speed, wider operating temperature range, longer cycle life, smaller size, and lighter weight. Currently, lithium-ion batteries are widely used in mobile phones, laptops, electric vehicles, energy storage cabinets, and other fields, and their application scope is becoming increasingly broad.

[0004] With the development of the energy storage industry, higher requirements are being placed on the dynamic performance of lithium-ion batteries. However, as the dynamic performance is improved, the amount of gas generated by the battery, especially cylindrical batteries, increases during the charging and discharging process, which will reduce the safety performance of the battery. Summary of the Invention

[0005] This application provides a battery with high dynamic performance and safety performance.

[0006] In a first aspect, embodiments of this application provide a battery comprising:

[0007] An electrode assembly, comprising a positive electrode, a separator, and a negative electrode;

[0008] An electrolyte comprising an electrolyte salt and an organic solvent, wherein the organic solvent comprises cyclic carbonates and chain carbonates, and the mass ratio of the cyclic carbonates to the chain carbonates is A; and

[0009] An outer casing assembly includes a first end cap assembly, a housing, and a second end cap assembly. The housing is a hollow structure. The first end cap assembly and the second end cap assembly are respectively disposed at opposite ends of the housing, forming a receiving cavity. The first end cap assembly includes a first top cover and a first explosion-proof valve connected together. The first top cover is disposed around the outer periphery of the first explosion-proof valve and is electrically connected to the positive electrode plate. The second end cap assembly includes a second top cover, a negative electrode post, and a second explosion-proof valve. The second top cover is disposed around the second explosion-proof valve. The negative electrode post passes through the second top cover and protrudes from the side of the second top cover opposite to the housing. The negative electrode post is electrically connected to the negative electrode plate. The area ratio of the first explosion-proof valve to the second explosion-proof valve is B.

[0010] The battery satisfies the following relationship: 2.23≤B / A≤17.65.

[0011] Secondly, embodiments of this application also provide a battery, which includes:

[0012] An electrode assembly, comprising a positive electrode, a separator, and a negative electrode;

[0013] An electrolyte comprising an electrolyte salt, wherein the electrolyte salt comprises lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, wherein the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is G; and

[0014] The housing assembly includes a first end cap assembly, a housing, and a second end cap assembly. The housing is a hollow structure. The first end cap assembly and the second end cap assembly are respectively disposed at opposite ends of the housing. The first end cap assembly, the housing, and the second end cap assembly form a receiving cavity for housing the electrode assembly and the electrolyte. The first end cap assembly includes a first top cover and a first explosion-proof valve. The first top cover is disposed around the outer periphery of the first explosion-proof valve and is electrically connected to the positive electrode plate. The second end cap assembly includes a second top cover, a negative electrode post, and a second explosion-proof valve. The second top cover is disposed around the outer periphery of the second explosion-proof valve. The negative electrode post passes through the second top cover and protrudes from the side of the second top cover opposite to the housing. The negative electrode post is electrically connected to the negative electrode plate. The area ratio of the first explosion-proof valve to the second explosion-proof valve is B.

[0015] The battery satisfies the following relationship: 0.03≤G / B≤9.87.

[0016] Thirdly, embodiments of this application also provide an energy storage device, which includes:

[0017] Box; and

[0018] Multiple batteries as described in the embodiments of this application are housed within the casing.

[0019] Fourthly, embodiments of this application also provide an energy storage system, which includes: an energy conversion device and an energy storage device as described in embodiments of this application, wherein the energy conversion device is electrically connected to the energy storage device, the energy conversion device is used to convert other forms of energy into electrical energy, and the energy storage device is used to store the electrical energy.

[0020] The battery in this embodiment is designed such that the ratio B of the area ratio of the first explosion-proof valve to the second explosion-proof valve and the mass ratio A of the cyclic carbonate to the chain carbonate are within the range of 2.23 ≤ B / A ≤ 17.65. This ensures that the ratio of cyclic carbonate to chain carbonate in the battery is within a suitable range, resulting in higher dissociation ability and better low-temperature performance of the electrolyte salt, as well as higher wettability of the electrode plates. Consequently, the battery exhibits better kinetic and cycle performance. Simultaneously, the increased gas production resulting from improved battery kinetics, combined with a reasonable configuration of the area ratio of the first and second explosion-proof valves, better reduces the risk of thermal runaway pressure relief. This allows the battery to have better pressure relief capability during overcharge explosion, thus achieving higher safety performance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 is a schematic diagram of the structure of a battery according to an embodiment of this application.

[0023] Figure 2 is a schematic diagram of the exploded structure of a battery according to an embodiment of this application.

[0024] Figure 3 is a structural schematic diagram of a battery according to an embodiment of this application from another perspective.

[0025] Figure 4 is a schematic diagram of the exploded structure of a battery according to an embodiment of this application from another perspective.

[0026] Figure 5 is a schematic diagram of the structure of an electrode assembly after winding according to an embodiment of this application.

[0027] Figure 6 is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application.

[0028] Figure 7 is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application.

[0029] Figure 8 is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0030] Figure 9 is a structural block diagram of an energy storage system according to an embodiment of this application.

[0031] Figure 10 is an application scenario diagram of an energy storage system according to an embodiment of this application.

[0032] Explanation of reference numerals in the attached drawings: 100-Battery, 10-Electrode assembly, 11-Positive electrode, 111-Positive current collector, 112-Positive active layer, 12-Separator, 13-Negative electrode, 131-Negative current collector, 132-Negative active layer, 20-Shell assembly, 21-First end cap assembly, 211-First top cover, 212-First explosion-proof valve, 22-Shell, 23-Second end cap assembly, 231-Second top cover, 232-Negative electrode post, 233-Second explosion-proof valve, 24-Receiving cavity, 200-Energy storage device, 210-Box, 300-Energy storage system, 310-Electrical energy conversion device. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0034] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0035] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0036] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0037] With the development of the energy storage industry, higher requirements are being placed on the dynamic performance of lithium-ion batteries. However, as the dynamic performance is improved, the amount of gas generated by the battery, especially cylindrical batteries, increases during the charging and discharging process, which will reduce the safety performance of the battery.

[0038] Cylindrical batteries have a high yield rate and low cost when assembled into energy storage modules with multiple batteries, making them a clear advantage in applications such as electric vehicles, home energy storage, and energy storage power stations.

[0039] However, due to differences in the core structure, cylindrical batteries are prone to drawbacks such as insufficient wetting, poor kinetics, easy gas generation in the cell, lithium plating, and rapid deterioration of cycle life. High kinetic electrolyte systems are needed to compensate for these drawbacks, but high kinetic electrolyte systems have a higher proportion of low-boiling-point solvents, and the solvents themselves are prone to vaporization and gas generation, which will deteriorate the safety performance under high temperature and overcharge conditions.

[0040] Please refer to Figures 1 to 5. This application provides a battery 100, which includes an electrode assembly 10, an electrolyte, and a casing assembly 20. The electrode assembly 10 includes a positive electrode 11, a separator 12, and a negative electrode 13. The electrolyte includes an electrolyte salt and an organic solvent, the organic solvent including cyclic carbonates and chain carbonates, with a mass ratio of cyclic carbonates to chain carbonates of A. The casing assembly 20 includes a first end cap assembly 21, a housing 22, and a second end cap assembly 23. The housing 22 has a hollow structure. The first end cap assembly 21 and the second end cap assembly 23 are respectively disposed at opposite ends of the housing 22, forming a receiving cavity 24 for housing the electrode assembly 10 and the electrolyte. The first end cap assembly 21 includes a connected first top cover 211 and a first explosion-proof valve 212, the first top cover 211 surrounding the outer periphery of the first explosion-proof valve 212. The first top cover 211 is electrically connected to the positive electrode 11. The second end cover assembly 23 includes a second top cover 231, a negative electrode post 232, and a second explosion-proof valve 233. The second top cover 231 is arranged around the second explosion-proof valve 233. The negative electrode post 232 passes through the second top cover 231 and protrudes from the side of the second top cover 231 away from the housing 22. The negative electrode post 232 is electrically connected to the negative electrode 13. The area ratio of the first explosion-proof valve 212 to the second explosion-proof valve 233 is B. The battery 100 satisfies the relationship: 2.23≤B / A≤17.65.

[0041] The battery 100 in this application embodiment can be, but is not limited to, at least one of lithium-ion battery 100, sodium-ion battery 100, etc.

[0042] It should be noted that the first top cover 211, the housing 22 and the second top cover 231 are connected, the second top cover 231 is connected to the second explosion-proof valve 233, and the negative electrode post 232 is insulated from the second top cover 231 so that the positive electrode 11 is insulated from the negative electrode 13.

[0043] It should be noted that the positive electrode 11, the diaphragm 12 and the negative electrode 13 are stacked in sequence and then wound together to form a wound electrode assembly 10.

[0044] Optionally, the housing 22 and the first top cover 211 are an integral structure. In other words, the housing 22 and the first top cover 211 are two different parts of the same component.

[0045] Specifically, the ratio B of the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 to the mass ratio A of the cyclic carbonate to the chain carbonate can be, but is not limited to, 2.23, 2.5, 3.0, 3.5, 4.0, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 17.65.

[0046] In this embodiment, if B / A is too large, the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large, and the mass ratio A of the cyclic carbonate to the chain carbonate is too small. If the mass ratio A of the cyclic carbonate to the chain carbonate is too small, it will increase the amount of gas produced during the overcharging process of the battery 100, and the gas produced is mainly flammable gases such as CH4 and C2H6. The increase in the production of flammable gases requires the battery 100 to have a better pressure relief capacity and a higher pressure relief speed. If the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large, the pressure relief capacity of the second explosion-proof valve 233 will be too small, making it difficult to relieve pressure in time during an explosion, thus reducing the safety performance of the battery 100. When B / A is too small, the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too small, and the mass ratio A of the cyclic carbonate to the chain carbonate is too large. When the mass ratio A of the cyclic carbonate to the chain carbonate is too large, the gas production during the overcharge process of the battery 100 will decrease, and the pressure relief requirements of the first explosion-proof valve 212 and the second explosion-proof valve 233 will be relatively reduced. However, when B is too small, the area of ​​the second explosion-proof valve 233 is too large, which increases the design difficulty of the negative electrode post 232, the second top cover 231 and the second explosion-proof valve 233. In addition, the mass ratio A of the cyclic carbonate to the chain carbonate is too large, which increases the viscosity of the electrolyte and increases the low-temperature freezing point of the electrolyte, reducing the room temperature cycle performance of the battery 100. In summary, when the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 and the mass ratio A of the cyclic carbonate to the chain carbonate are within the range of 2.23 ≤ B / A ≤ 17.65, the ratio of cyclic carbonate to chain carbonate in the battery 100 is within a suitable range. This results in the electrolyte salt having a high dissociation capacity and good low-temperature performance, as well as high wettability to the electrode plates, thus giving the battery 100 good kinetic and cycle performance. Simultaneously, the increased gas production resulting from the improved kinetics of the battery 100, through a reasonable configuration of the area ratio of the first explosion-proof valve 212 and the second explosion-proof valve 233, can better reduce the risk of thermal runaway pressure relief, allowing the battery 100 to have good pressure relief capacity during overcharge explosion, thereby achieving high safety performance.

[0047] In some embodiments, the mass ratio A of the cyclic carbonate to the chain carbonate is in the range of 0.17 ≤ A ≤ 0.67.

[0048] Specifically, the mass ratio A of the cyclic carbonate to the chain carbonate can be, but is not limited to, 0.17, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, 0.5, 0.53, 0.55, 0.58, 0.6, 0.63, 0.65, 0.67, etc.

[0049] In this embodiment, cyclic carbonates have high dielectric constant and high ionic conductivity, enabling the formation of a stable SEI film on the surface of the negative electrode 13, but they also have a relatively high viscosity. Chain carbonates have lower viscosity and better electrochemical stability than cyclic carbonates, thus improving the low-temperature performance of the electrolyte. If the mass ratio A of the cyclic carbonate to the chain carbonate is too small, the electrolyte viscosity decreases, which is beneficial for improving the wettability of the electrolyte to the electrode assembly 10, thereby improving the cycle performance and kinetic performance of the battery 100. However, the reduction reaction of the chain carbonate is the main cause of gas production within the battery 100. If the mass ratio A of the cyclic carbonate to the chain carbonate is too small, it will increase the amount of gas produced during the overcharging process of the battery 100, and the produced gas is mainly flammable gases such as CH4 and C2H6. The increased production of flammable gases increases the probability of thermal runaway such as explosion and fire in the battery 100, reducing the safety performance of the battery 100. As the mass ratio A of the cyclic carbonate to the chain carbonate increases, i.e., the content of the cyclic carbonate increases and the content of the chain carbonate decreases, the total gas production in the battery 100 gradually decreases when the battery 100 is overcharged. In addition, the main types of gas produced are CO2, H2, CO, etc. The increase in the production of non-flammable gas CO2 reduces the risk of thermal runaway such as fire in the battery 100 and improves the safety performance of the battery 100. However, the increase in the content of cyclic carbonate increases the viscosity of the electrolyte and increases the low-temperature freezing point of the electrolyte, which reduces the room temperature cycling performance of the battery 100. When the mass ratio A of the cyclic carbonate to the chain carbonate is in the range of 0.17≤A≤0.67, the electrolyte can have a suitable viscosity, a low freezing point and high room temperature cycling performance. It can also reduce the amount of gas produced by the battery 100 during overcharging, and reduce the amount of combustible gas produced. Combined with the design of the explosion-proof valve, the battery 100 is less prone to thermal runaway and has high safety performance.

[0050] In some embodiments, the cyclic carbonate includes ethylene carbonate (EC), the chain carbonate includes ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), and the mass ratio A1 of ethyl methyl carbonate to dimethyl carbonate is in the range of 0.5 ≤ A1 ≤ 2.

[0051] Specifically, the mass ratio A1 of methyl ethyl carbonate to dimethyl carbonate can be, but is not limited to, 0.5, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, etc.

[0052] In this embodiment, the higher the mass ratio A1 of methyl ethyl carbonate to dimethyl carbonate in the electrolyte, the lower the low-temperature freezing point of the electrolyte. However, if the mass ratio A1 is too large, the high-temperature side reactions of the battery 100 will be aggravated, which is detrimental to the cycle performance of the battery 100. If the mass ratio A1 is too small, the low-temperature freezing point of the electrolyte will increase, which is also detrimental to the cycle performance of the battery 100 and reduces the overcharge resistance of the battery 100, increasing the risk of explosion when the battery 100 is overcharged. When the mass ratio A1 of methyl ethyl carbonate to dimethyl carbonate is in the range of 0.5 ≤ A1 ≤ 2, the battery 100 has better low-temperature and high-temperature cycle performance.

[0053] Alternatively, cyclic carbonates may also include propylene carbonate (PC).

[0054] Optionally, the organic solvent further includes at least one of ethyl acetate, propyl acetate, ethyl propionate, propyl propionate, γ-butyrolactone, 2,2-difluoroethyl acetate, methyl formate, and ethyl fluoroacetate.

[0055] In the organic solvent, the total mass of the cyclic carbonate and the chain carbonate accounts for 80% to 100% of the organic solvent. For example, it can be 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98%, 100%, etc.

[0056] In some embodiments, the electrolyte salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide, wherein the mass ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate is G; the battery 100 also satisfies the relationship: 0.03≤G / B≤9.87.

[0057] Specifically, the ratio G / B of the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 can be, but is not limited to, 0.03, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, 2, 3, 4, 5, 6, 7, 8, 9, 9.87, etc.

[0058] In this embodiment, if G / B is too small, the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is too small, and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large. If G is too small, the thermal stability of the electrolyte will decrease, and the heat generated by the decomposition of lithium hexafluorophosphate will increase when the battery 100 is overcharged. The heat and gas generated by the decomposition cause the gas pressure inside the battery 100 to increase sharply. If the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large at this time, that is, the pressure relief capacity of the first explosion-proof valve 212 and the second explosion-proof valve 233 is too different, then the second explosion-proof valve 233 with a smaller area has a too low pressure relief rate, which reduces the safety performance of the battery 100. The negative terminal post 232 of the battery 100 protrudes from the side of the second top cover 231 away from the housing 22. Therefore, during assembly and use, the second end cover assembly 23 with the negative terminal post 232 usually faces upward and the first end cover assembly 21 faces downward. With the increase of G, the degree of dissociation of the electrolyte salt (i.e., lithium salt) can be improved, thereby improving the dynamic performance of the battery 100. However, if G / B is too large, the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate will be too large, and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 will be too small. If G is too large, the content of lithium difluorosulfonylimide in the electrolyte will be too high, which will increase the total amount of gas produced when the battery 100 is overcharged. The heavier gas in the produced gas will accumulate towards the first explosion-proof valve 212, making the pressure on the first explosion-proof valve 212 greater. If B is too small at this time, the area of ​​the first explosion-proof valve 212 will be too small, which will reduce the pressure relief rate of the first explosion-proof valve 212 and increase the risk of battery 100 overcharging. In summary, when the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 are in the range of 0.03 ≤ G / B ≤ 9.87, the first explosion-proof valve 212 and the second explosion-proof valve 233 can have a suitable pressure relief rate when the battery 100 is overcharged, thus improving the safety performance of the battery 100. At the same time, the battery 100 can also have high kinetic performance and cycle performance.

[0059] In some embodiments, the mass ratio G of the lithium difluorosulfonyl imide to the lithium hexafluorophosphate ranges from 0.1 to G ≤ 14.8.

[0060] Specifically, the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate can be, but is not limited to, 0.1, 0.3, 0.5, 1, 2, 3, 5, 6, 8, 10, 11, 12, 13, 14, or 14.8.

[0061] When battery 100 is overcharged, the electrolyte is rapidly consumed and vaporized, allowing the gas generated inside battery 100 to escape through the first explosion-proof valve 212 and the second explosion-proof valve 233. In this embodiment, compared to using only lithium hexafluorophosphate as the electrolyte salt, the combination of lithium difluorosulfonylimide and lithium hexafluorophosphate can improve the degree of dissociation of the electrolyte salt (i.e., lithium salt) and enhance the kinetic performance of battery 100. When the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate is too small, the proportion of lithium hexafluorophosphate in the electrolyte salt is high, which reduces the thermal stability of the electrolyte, increases the risk of heat generation from the decomposition of lithium hexafluorophosphate, and reduces the safety performance of battery 100. When the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate is too high, the content of lithium difluorosulfonylimide in the electrolyte is too high, which increases the total gas production during overcharging of the battery 100, increasing the risk of overcharging. Simultaneously, the corrosion of the aluminum foil (i.e., the positive current collector of the positive electrode 11) at high temperatures reduces the adhesion between the positive current collector and the positive active layer of the positive electrode 11, potentially leading to detachment and significantly reducing the cycle life of the battery 100. When the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate is in the range of 0.1 ≤ G ≤ 14.8, the battery 100 can exhibit higher kinetic and cycle performance.

[0062] Optionally, the molar concentration M of the electrolyte salt in the electrolyte ranges from 0.8 mol / L to 1.2 mol / L. The electrolyte salinity M in the electrolyte can be, but is not limited to, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, etc. If the electrolyte salt concentration M is too small, the concentration of free ions in the electrolyte is too low, reducing the conductivity of the electrolyte and thus reducing the kinetic performance of the battery 100. If the electrolyte salt concentration is too large, some electrolyte salt may remain undissociated, increasing the viscosity of the electrolyte and further reducing its conductivity, also lowering the kinetic performance of the battery 100. When the electrolyte salt concentration M in the electrolyte ranges from 0.8 mol / L to 1.2 mol / L, the electrolyte can have a higher conductivity, resulting in better kinetic performance of the battery 100.

[0063] In some embodiments, the electrolyte further includes a sulfur-containing additive. The sulfur-containing additive can form lithium sulfate or alkyl lithium sulfate on the positive electrode 11, which can further stabilize the solid electrolyte interface (SEI) film of the positive electrode 11 and make the SEI film of the positive electrode 11 thinner, thereby better reducing the impedance of the positive electrode 11, reducing the high-temperature heat generation of the positive electrode 11, and improving the safety performance of the battery 100.

[0064] Optionally, the sulfur-containing additive can be, but is not limited to, a sulfur-containing additive for the positive electrode.

[0065] Optionally, in the electrolyte, the mass fraction w1 of the sulfur-containing additive ranges from 0.1 wt% to w1 ≤ 1 wt%. Specifically, in the electrolyte, the mass fraction w1 of the sulfur-containing additive can be, but is not limited to, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, etc. If the mass fraction w1 of the sulfur-containing additive in the electrolyte is too low, its stability on the interfacial film of the positive electrode 11 is limited, and it cannot effectively improve the safety performance of the battery 100. If the mass fraction w1 of the sulfur-containing additive in the electrolyte is too high, the sulfur-containing additive is prone to decomposition and acid production at high temperatures, which damages the interfacial film of the positive electrode 11. This causes the positive active layer of the positive electrode 11 to come into direct contact with the electrolyte, increasing side reactions between the positive active layer and the electrolyte, thereby increasing electrolyte consumption and reducing the cycle capacity retention rate of the battery 100. When the mass fraction of the sulfur-containing additive in the electrolyte is 0.1wt% ≤ w1 ≤ 1wt%, the safety performance of the battery 100 can be better improved while maintaining a high cycle capacity retention rate.

[0066] In some embodiments, the sulfur-containing additive includes at least one of bis(ethylene sulfonyl)methane, methylene disulfonate (MMDS), ethylene sulfate (DTD), propylene sulfonate lactone (PST), butyl sulfonate lactone (BS), and propylene sulfite (PS). In this embodiment, using these sulfur-containing additives can better stabilize the interfacial film of the positive electrode 11, reduce the impedance of the positive electrode 11, reduce the high-temperature heat generation of the positive electrode 11, and improve the safety performance of the battery 100. Furthermore, these substances are less prone to decomposition and acid production when the battery 100 is at high temperatures, which can better reduce the consumption of electrolyte at high temperatures, thereby enabling the battery 100 to maintain a high cycle capacity retention rate.

[0067] Optionally, the electrolyte further includes film-forming additives. When the electrolyte is applied to the lithium-ion battery 100, the film-forming additives can be used to promote the formation of an interface film of at least one of the positive electrode 11 and the negative electrode 13 and maintain the stability of the interface film.

[0068] Optionally, the film-forming additive includes at least one of fluoroethylene carbonate (FEC), ethylene sulfate (DTD), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), trithio(trimethylsilane) phosphate, tri(trimethylsilane) borate, adiponitrile, succinate, and 1,3,6-hexanetrionitrile.

[0069] Optionally, the mass fraction of the film-forming additive ranges from 1.5% to 3%. Specifically, the mass fraction of the film-forming additive can be, but is not limited to, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, etc.

[0070] In some embodiments, the area of ​​the first explosion-proof valve 212 is larger than the area of ​​the second explosion-proof valve 233, and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is in the range of 1.5≤B≤3.

[0071] Specifically, the area ratio B of the first explosion-proof valve 212 and the second explosion-proof valve 233 can be, but is not limited to, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.1, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, etc.

[0072] For the cylindrical battery 100, the surface of its first end cap assembly 21 (i.e., the end cap electrically connected to the positive electrode 11) facing away from the housing 22 is flat, and the negative electrode post 232 protrudes from the side of the second end cap assembly 23 (i.e., the end cap electrically connected to the negative electrode 13) facing away from the housing 22. Therefore, in use, the first end cap assembly 21 of the battery 100 faces downward and the second end cap assembly 23 of the battery 100 faces upward. When the battery 100 is overcharged, most of the electrolyte in the housing assembly 20 is consumed. In the gas generated in the battery 100, the heavier gas will sink and accumulate at the position of the first end cap assembly 21 (i.e., the first explosion-proof valve 212), while the lighter gas will rise and accumulate at the position of the second end cap assembly 23 (i.e., the second explosion-proof valve 233). This makes the gas pressure on the second explosion-proof valve 233 greater than the gas pressure on the first explosion-proof valve 212. In this embodiment, by making the area of ​​the first explosion-proof valve 212 larger than the area of ​​the second explosion-proof valve 233, the first explosion-proof valve 212 has a better pressure relief capacity than the second explosion-proof valve 233. When the battery 100 is overcharged and the first explosion-proof valve 212 and the second explosion-proof valve 233 explode, the first explosion-proof valve 212 can release the gas pressure faster than the second explosion-proof valve 233, thereby improving the safety performance of the battery 100 when overcharged. However, when the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too small, the second explosion-proof valve 233 becomes too large, increasing the difficulty of designing the second top cover 231 and the negative terminal post 232. If the area of ​​the first explosion-proof valve 212 is too small (explosion-proof valve on the positive side), the first explosion-proof valve 212 side cannot release pressure in time when the battery 100 is overcharged. In addition, it is difficult to match application scenarios with large gas production when the ratio of cyclic carbonate to chain carbonate and the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate are low. Furthermore, when the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large, the first explosion-proof valve 212 is too large, and the space reserved in the first top cover 211 is too small, causing the first explosion-proof valve 212 and the first top cover 211 to fail to meet the design requirements. In addition, the pressure resistance of the first explosion-proof valve 212 is reduced, which may cause the first explosion-proof valve 212 to explode prematurely, affecting the normal use of the battery 100. The second explosion-proof valve 233 is too small, and when the second explosion-proof valve 233 explodes, the pressure release rate is slow. The gas release rate at the first explosion-proof valve 212 of the battery 100 is too slow, and the pressure cannot be released in time, increasing the risk of the battery 100 exploding. It is difficult to match the application scenarios with a large gas production when the ratio of cyclic carbonate to chain carbonate and the mass ratio G of lithium difluorosulfonyl imide to lithium hexafluorophosphate are low.When the area ratio B of the first explosion-proof valve 212 and the second explosion-proof valve 233 is in the range of 1.5≤B≤3, it can ensure that when the first explosion-proof valve 212 and the second explosion-proof valve 233 explode, the gas release rate at the first explosion-proof valve 212 of the battery 100 is relatively fast, and the pressure resistance of the first explosion-proof valve 212 and the second explosion-proof valve 233 will not differ too much, so the battery 100 will not explode prematurely and affect normal use.

[0073] In some embodiments, the area b1 of the first explosion-proof valve 212 is 120 mm. 2 ≤b1≤240mm 2 The area b2 of the second explosion-proof valve 233 is 90mm². 2 ≤b2≤160mm 2 .

[0074] Specifically, the area b1 of the first explosion-proof valve 212 can be, but is not limited to, 120 mm². 2 140mm 2 150mm 2 160mm 2 180mm 2 200mm 2 220mm 2 240mm 2 If the area b1 of the first explosion-proof valve 212 is too small, the pressure relief capacity of the first explosion-proof valve 212 will be reduced, thus reducing the safety performance of the battery 100 when overcharged. If the area b1 of the first explosion-proof valve 212 is too large, the area of ​​the first top cover 211 needs to be increased, which makes the battery 100 thicker and the electrode assembly 10 wound with more turns. During the charge and discharge cycle, the part of the electrode assembly 10 near the inner side of the wound electrode assembly 10 will be subjected to excessive compressive stress during the lithium intercalation expansion. The electrolyte in this part of the electrode assembly 10 is easily squeezed out, which makes the part of the electrode assembly 10 near the winding center in a liquid-deficient state. This increases the gas production of the battery 100, thereby reducing the safety performance of the battery 100 and making lithium plating more likely, which deteriorates the cycle performance of the battery 100.

[0075] Specifically, the area b2 of the second explosion-proof valve 233 can be, but is not limited to, 90 mm². 2 100mm 2 110mm 2 120mm 2 140mm 2 150mm 2 160mm 2If the area b1 of the second explosion-proof valve 233 is too small, it reduces the pressure relief capacity of the second explosion-proof valve 233 and reduces the safety performance of the battery 100 when overcharged. If the area b1 of the second explosion-proof valve 233 is too large, the area of ​​the second top cover 231 needs to be increased, which makes the battery 100 thicker and the electrode assembly 10 wound with more turns. During the charge and discharge cycle, the part of the electrode assembly 10 near the inner side of the wound electrode assembly 10 is subjected to excessive compressive stress during lithium intercalation expansion. The electrolyte in this part of the electrode assembly 10 is easily squeezed out, which makes the part of the electrode assembly 10 near the winding center in a liquid-deficient state. This increases the gas production of the battery 100, thereby reducing the safety performance of the battery 100 and making lithium plating more likely, which deteriorates the cycle performance of the battery 100. In addition, it increases the design difficulty of the negative electrode post 232 and the second explosion-proof valve 233.

[0076] Referring again to Figure 2, in some embodiments, the battery 100 is cylindrical (i.e., a cylindrical battery 100), and the ratio L / D of the length L of the battery 100 to its diameter D is in the range of 2.43 ≤ L / D ≤ ​​5.98. In other words, the length-to-diameter ratio L / D of the battery 100 is in the range of 2.43 ≤ L / D ≤ ​​5.98.

[0077] Understandably, the outer casing assembly 20 is cylindrical, the housing 22 is cylindrical, and the first end cap assembly 21 and the second end cap assembly 23 are circular.

[0078] Specifically, the ratio L / D of the length L of the battery 100 to the diameter D of the battery 100 can be, but is not limited to, 2.43, 2.6, 2.8, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 5.98, etc.

[0079] In this embodiment, the ratio L / D of the length L of the battery 100 to the diameter D of the battery 100 is too small. As a result, the electrode assembly 10 of the battery 100 has a large number of turns and is relatively thick. During the charge and discharge cycle, the part of the area near the inner side of the wound electrode assembly 10 experiences excessive compressive stress during lithium intercalation expansion. The electrolyte in this part of the electrode assembly 10 is easily squeezed out, resulting in a lack of electrolyte in the part of the electrode assembly 10 near the winding center. This increases the gas production of the battery 100, thereby reducing the safety performance of the battery 100 and making it prone to lithium plating, which deteriorates the cycle performance of the battery 100. Cylindrical batteries 100 are typically filled with electrolyte from one cylindrical end. After filling, the electrolyte first enters the gap between the outer casing assembly 20 and the wound electrode assembly 10, and then gradually permeates the entire electrode assembly 10 from its outer ring and both ends (the end near the first end cap assembly 21 and the end near the second end cap assembly 23). When the ratio L / D of the length L of the battery 100 to its diameter D is too large, the electrode assembly 10 is designed to be too long, and the path of the electrolyte from both ends of the electrode assembly 10 to the middle is too long, resulting in excessively long electrolyte flow along the battery 100. In the length direction of the battery 100, insufficient or inadequate wetting of the electrode assembly 10 near the middle position can easily form an unwetted zone in the middle of the length direction. This makes lithium plating more likely in this part, reducing the cycle performance of the battery 100 and causing premature cycle failure. Furthermore, it increases the side reactions between this unwetted zone and the solvent in the electrolyte, resulting in increased gas production, a longer venting path, and a slower pressure release rate within the battery 100, increasing the internal pressure and thus the risk of battery explosion. When the ratio of the length L to the diameter D of the battery 100, L / D, is in the range of 2.43 ≤ L / D ≤ ​​5.98, the entire electrolyte can have better wettability of the electrode assembly 10, making gas production less likely, thus giving the battery 100 better safety and cycle performance.

[0080] Referring to Figure 6, optionally, the positive electrode 11 includes a positive current collector 111 and a positive active layer 112, wherein the positive active layer 112 is disposed on the surface of the positive current collector 111. It can be understood that the positive active layer 112 may cover one surface or both opposite surfaces of the positive current collector 111.

[0081] Optionally, the positive current collector 111 can be, but is not limited to, an aluminum sheet.

[0082] Optionally, the positive electrode active layer 112 includes a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a positive electrode thickener.

[0083] Optionally, the positive electrode active material can be, but is not limited to, lithium iron phosphate.

[0084] Optionally, the diaphragm 12 can be, but is not limited to, at least one of polypropylene membrane (PP membrane), polyethylene membrane (PE membrane), ceramic diaphragm 12, etc.

[0085] Optionally, the thickness of the diaphragm 12 is 14 μm to 18 μm. Specifically, the thickness of the diaphragm 12 can be, but is not limited to, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm and 18 μm.

[0086] Referring to Figure 7, optionally, the negative electrode 13 includes a negative electrode current collector 131 and a negative electrode active layer 132, the negative electrode active layer 132 being disposed on the surface of the negative electrode current collector 131. It can be understood that the negative electrode active layer 132 may cover one surface or both opposite surfaces of the negative electrode current collector 131.

[0087] Optionally, the negative electrode current collector 131 can be, but is not limited to, a copper sheet.

[0088] Optionally, the negative electrode active layer 132 includes a negative electrode active material, a second conductive agent, a second binder, and a second thickener.

[0089] Optionally, the negative electrode active material can be, but is not limited to, graphite.

[0090] Please refer again to Figures 1 to 5. This application embodiment also provides a battery 100, which includes an electrode assembly 10, an electrolyte, and a casing assembly 20. The electrode assembly 10 includes a positive electrode 11, a separator 12, and a negative electrode 13; the electrolyte includes an electrolyte salt, which includes lithium difluorosulfonylimide and lithium hexafluorophosphate, with a mass ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate of G; the casing assembly 20 includes a first end cap assembly 21, a housing 22, and a second end cap assembly 23. The housing 22 has a hollow structure. The first end cap assembly 21 and the second end cap assembly 23 are respectively disposed at opposite ends of the housing 22, forming a receiving cavity 24 for housing the electrode assembly 10 and the electrolyte; the first end cap assembly 21 includes a first top... The battery 100 comprises a cover 211 and a first explosion-proof valve 212. The first cover 211 is arranged around the outer periphery of the first explosion-proof valve 212 and is electrically connected to the positive electrode 11. The second end cover assembly 23 includes a second cover 231, a negative electrode post 232 and a second explosion-proof valve 233. The second cover 231 is arranged around the outer periphery of the second explosion-proof valve 233. The negative electrode post 232 passes through the second cover 231 and protrudes from the side of the second cover 231 away from the housing 22. The negative electrode post 232 is electrically connected to the negative electrode 13. The area ratio of the first explosion-proof valve 212 to the second explosion-proof valve 233 is B. The battery 100 satisfies the relationship: 0.03≤G / B≤9.87.

[0091] The battery 100 in this application embodiment can be, but is not limited to, at least one of lithium-ion battery 100, sodium-ion battery 100, etc.

[0092] For detailed descriptions of other aspects of the housing assembly 20, electrode assembly 10, positive electrode 11, diaphragm 12, negative electrode 13, etc., please refer to the descriptions of the corresponding parts of the above embodiments, which will not be repeated here.

[0093] Specifically, the ratio G / B of the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 can be, but is not limited to, 0.03, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, 2, 3, 4, 5, 6, 7, 8, 9, 9.87, etc.

[0094] In this embodiment, if G / B is too small, the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is too small, and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large. If G is too small, the thermal stability of the electrolyte will decrease, and the heat generated by the decomposition of lithium hexafluorophosphate will increase when the battery 100 is overcharged. The heat and gas generated by the decomposition cause the gas pressure inside the battery 100 to increase sharply. If the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large at this time, that is, the pressure relief capacity of the first explosion-proof valve 212 and the second explosion-proof valve 233 is too different, then the second explosion-proof valve 233 with a smaller area has a too low pressure relief rate, which reduces the safety performance of the battery 100. The negative terminal post 232 of the battery 100 protrudes from the side of the second top cover 231 away from the housing 22. Therefore, during assembly and use, the second end cover assembly 23 with the negative terminal post 232 usually faces upward and the first end cover assembly 21 faces downward. With the increase of G, the degree of dissociation of the electrolyte salt (i.e., lithium salt) can be improved, thereby improving the dynamic performance of the battery 100. However, if G / B is too large, the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate will be too large, and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 will be too small. If G is too large, the content of lithium difluorosulfonylimide in the electrolyte will be too high, which will increase the total amount of gas produced when the battery 100 is overcharged. The heavier gas in the produced gas will accumulate towards the first explosion-proof valve 212, making the pressure on the first explosion-proof valve 212 greater. If B is too small at this time, the area of ​​the first explosion-proof valve 212 will be too small, which will reduce the pressure relief rate of the first explosion-proof valve 212 and increase the risk of battery 100 overcharging. In summary, when the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate and the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 are in the range of 0.03 ≤ G / B ≤ 9.87, the first explosion-proof valve 212 and the second explosion-proof valve 233 can have a suitable pressure relief rate when the battery 100 is overcharged, thus improving the safety performance of the battery 100. At the same time, the battery 100 can also have high kinetic performance and cycle performance.

[0095] In some embodiments, the mass ratio G of the lithium difluorosulfonyl imide to the lithium hexafluorophosphate ranges from 0.1 to G ≤ 14.8.

[0096] Specifically, the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate can be, but is not limited to, 0.1, 0.3, 0.5, 1, 2, 3, 5, 6, 8, 10, 11, 12, 13, 14, or 14.8.

[0097] When battery 100 is overcharged, the electrolyte is rapidly consumed and vaporized, allowing the gas generated inside battery 100 to escape through the first explosion-proof valve 212 and the second explosion-proof valve 233. In this embodiment, compared to using only lithium hexafluorophosphate as the electrolyte salt, the combination of lithium difluorosulfonylimide and lithium hexafluorophosphate can improve the degree of dissociation of the electrolyte salt (i.e., lithium salt) and enhance the kinetic performance of battery 100. When the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate is too small, the proportion of lithium hexafluorophosphate in the electrolyte salt is high, which reduces the thermal stability of the electrolyte, increases the risk of heat generation from the decomposition of lithium hexafluorophosphate, and reduces the safety performance of battery 100. When the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate is too high, the content of lithium difluorosulfonylimide in the electrolyte is too high, which increases the total gas production during overcharging of the battery 100, increasing the risk of overcharging. Simultaneously, the corrosion of the aluminum foil (i.e., the positive current collector 111 of the positive electrode 11) at high temperatures reduces the adhesion between the positive current collector 111 and the positive active layer 112, potentially leading to detachment and significantly reducing the cycle life of the battery 100. When the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate is in the range of 0.1 ≤ G ≤ 14.8, the battery 100 can exhibit higher kinetic and cycle performance.

[0098] In some embodiments, the area ratio B of the first explosion-proof valve 212 and the second explosion-proof valve 233 is in the range of 1.5≤B≤3.

[0099] Specifically, the area ratio B of the first explosion-proof valve 212 and the second explosion-proof valve 233 can be, but is not limited to, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.1, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, etc.

[0100] For the cylindrical battery 100, the surface of its first end cap assembly 21 (i.e., the end cap electrically connected to the positive electrode 11) facing away from the housing 22 is flat, and the negative electrode post 232 protrudes from the side of the second end cap assembly 23 (i.e., the end cap electrically connected to the negative electrode 13) facing away from the housing 22. Therefore, in use, the first end cap assembly 21 of the battery 100 faces downward and the second end cap assembly 23 of the battery 100 faces upward. When the battery 100 is overcharged, most of the electrolyte in the housing assembly 20 is consumed. In the gas generated in the battery 100, the heavier gas will sink and accumulate at the position of the first end cap assembly 21 (i.e., the first explosion-proof valve 212), while the lighter gas will rise and accumulate at the position of the second end cap assembly 23 (i.e., the second explosion-proof valve 233). This makes the gas pressure on the second explosion-proof valve 233 greater than the gas pressure on the first explosion-proof valve 212. In this embodiment, by making the area of ​​the first explosion-proof valve 212 larger than the area of ​​the second explosion-proof valve 233, the first explosion-proof valve 212 has a better pressure relief capacity than the second explosion-proof valve 233. This allows the first explosion-proof valve 212 to release gas pressure more quickly when the battery 100 is overcharged and both the first and second explosion-proof valves 212 and 233 explode, thus improving the safety performance of the battery 100 during overcharge. However, if the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too small, the second explosion-proof valve 233 becomes too large, increasing the design difficulty of the second top cover 231 and the negative terminal post 232. If the area of ​​the first explosion-proof valve 212 is too small (positive terminal side explosion-proof valve), the first explosion-proof valve 212 cannot release pressure in time when the battery 100 is overcharged. Furthermore, it is difficult to match applications with a low mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate, where the gas production is large. Furthermore, when the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large, the first explosion-proof valve 212 is too large, and the space reserved in the first top cover 211 is too small, causing the first explosion-proof valve 212 and the first top cover 211 to fail to meet the design requirements. In addition, the pressure resistance of the first explosion-proof valve 212 is reduced, which may cause the first explosion-proof valve 212 to explode prematurely, affecting the normal use of the battery 100. The second explosion-proof valve 233 is too small, and when the second explosion-proof valve 233 explodes, the pressure release rate is slow. The gas release rate at the first explosion-proof valve 212 of the battery 100 is too slow, and the pressure cannot be released in time, increasing the risk of the battery 100 exploding. This makes it difficult to match the application scenarios with a large gas production when the mass ratio G of the lithium difluorosulfonylimide to the lithium hexafluorophosphate is low.When the area ratio B of the first explosion-proof valve 212 and the second explosion-proof valve 233 is in the range of 1.5≤B≤3, it can ensure that when the first explosion-proof valve 212 and the second explosion-proof valve 233 explode, the gas release rate at the first explosion-proof valve 212 of the battery 100 is relatively fast, and the pressure resistance of the first explosion-proof valve 212 and the second explosion-proof valve 233 will not differ too much, so the battery 100 will not explode prematurely and affect normal use.

[0101] In some embodiments, the area b1 of the first explosion-proof valve 212 is 120 mm. 2 ≤b1≤240mm 2 The area of ​​the second explosion-proof valve 233, b2, is 90 mm². 2 ≤b2≤160mm 2 .

[0102] Specifically, the area b1 of the first explosion-proof valve 212 can be, but is not limited to, 120 mm². 2 140mm 2 150mm 2 160mm 2 180mm 2 200mm 2 220mm 2 240mm 2 If the area b1 of the first explosion-proof valve 212 is too small, the pressure relief capacity of the first explosion-proof valve 212 will be reduced, thus reducing the safety performance of the battery 100 when overcharged. If the area b1 of the first explosion-proof valve 212 is too large, the area of ​​the first top cover 211 needs to be increased, which makes the battery 100 thicker and the electrode assembly 10 wound with more turns. During the charge and discharge cycle, the part of the electrode assembly 10 near the inner side of the wound electrode assembly 10 will be subjected to excessive compressive stress during the lithium intercalation expansion. The electrolyte in this part of the electrode assembly 10 is easily squeezed out, which makes the part of the electrode assembly 10 near the winding center in a liquid-deficient state. This increases the gas production of the battery 100, thereby reducing the safety performance of the battery 100 and making lithium plating more likely, which deteriorates the cycle performance of the battery 100.

[0103] Specifically, the area b2 of the second explosion-proof valve 233 can be, but is not limited to, 90 mm². 2 100mm 2 110mm 2 120mm 2 140mm 2 150mm 2 160mm 2If the area b1 of the second explosion-proof valve 233 is too small, it reduces the pressure relief capacity of the second explosion-proof valve 233 and reduces the safety performance of the battery 100 when overcharged. If the area b1 of the second explosion-proof valve 233 is too large, the area of ​​the second top cover 231 needs to be increased, which makes the battery 100 thicker and the electrode assembly 10 wound with more turns. During the charge and discharge cycle, the part of the electrode assembly 10 near the inner side of the wound electrode assembly 10 is subjected to excessive compressive stress during lithium intercalation expansion. The electrolyte in this part of the electrode assembly 10 is easily squeezed out, which makes the part of the electrode assembly 10 near the winding center in a liquid-deficient state. This increases the gas production of the battery 100, thereby reducing the safety performance of the battery 100 and making lithium plating more likely, which deteriorates the cycle performance of the battery 100. In addition, it increases the design difficulty of the negative electrode post 232 and the second explosion-proof valve 233.

[0104] Please refer to Figure 2 again. In some embodiments, the outer shell assembly 20 is cylindrical, and the central axis of the outer shell assembly 20 extends along the arrangement direction of the first end cap assembly 21, the housing 22 and the second end cap assembly 23. The length L of the outer shell assembly 20 and the diameter D of the outer shell assembly 20 satisfy the relationship: 2.43≤L / D≤5.98.

[0105] Understandably, the outer casing assembly 20 is cylindrical, the housing 22 is cylindrical, and the first end cap assembly 21 and the second end cap assembly 23 are circular.

[0106] Specifically, the ratio L / D of the length L of the battery 100 to the diameter D of the battery 100 can be, but is not limited to, 2.43, 2.6, 2.8, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 5.98, etc.

[0107] In this embodiment, the ratio L / D of the length L of the battery 100 to the diameter D of the battery 100 is too small. As a result, the electrode assembly 10 of the battery 100 has a large number of turns and is relatively thick. During the charge and discharge cycle, the part of the area near the inner side of the wound electrode assembly 10 experiences excessive compressive stress during lithium intercalation expansion. The electrolyte in this part of the electrode assembly 10 is easily squeezed out, resulting in a lack of electrolyte in the part of the electrode assembly 10 near the winding center. This increases the gas production of the battery 100, thereby reducing the safety performance of the battery 100 and making it prone to lithium plating, which deteriorates the cycle performance of the battery 100. Cylindrical batteries 100 are typically filled with electrolyte from one cylindrical end. After filling, the electrolyte first enters the gap between the outer casing assembly 20 and the wound electrode assembly 10, and then gradually permeates the entire electrode assembly 10 from its outer ring and both ends (the end near the first end cap assembly 21 and the end near the second end cap assembly 23). When the ratio L / D of the length L of the battery 100 to its diameter D is too large, the electrode assembly 10 is designed to be too long, and the path of the electrolyte from both ends of the electrode assembly 10 to the middle is too long, resulting in excessively long electrolyte flow along the battery 100. In the length direction of the battery 100, insufficient or inadequate wetting of the electrode assembly 10 near the middle position can easily form an unwetted zone in the middle of the length direction. This makes lithium plating more likely in this part, reducing the cycle performance of the battery 100 and causing premature cycle failure. Furthermore, it increases the side reactions between this unwetted zone and the solvent in the electrolyte, resulting in increased gas production, a longer venting path, and a slower pressure release rate within the battery 100, increasing the internal pressure and thus the risk of battery explosion. When the ratio of the length L to the diameter D of the battery 100, L / D, is in the range of 2.43 ≤ L / D ≤ ​​5.98, the entire electrolyte can have better wettability of the electrode assembly 10, making gas production less likely, thus giving the battery 100 better safety and cycle performance.

[0108] Optionally, the electrolyte further includes an organic solvent, which includes cyclic carbonates and chain carbonates.

[0109] For descriptions of other aspects such as electrolytes and organic solvents, please refer to the descriptions in the corresponding sections of the above embodiments, which will not be repeated here.

[0110] The battery 100 of this application will be further described below through specific embodiments.

[0111] Examples 1 to 32, Comparative Examples 1 to 6

[0112] The batteries 100 of each embodiment and comparative example are prepared by the following steps:

[0113] (1) Preparation of electrolyte: In an argon atmosphere glove box with a moisture content ≤1ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a preset ratio, sealed to prevent water from entering, and placed in a 0℃ freezer for 2 hours. The mixture was then quickly transferred to a glove box, and lithium hexafluorophosphate and lithium difluorosulfonyl imide were added. The mixture was stirred until completely dissolved and homogeneous. After the temperature stabilized, film-forming additives fluoroethylene carbonate (FEC, 1.5wt%), ethylene sulfate (DTD), and vinylene carbonate (VC, 3wt%) were added and mixed evenly to obtain the electrolyte.

[0114] The ratios of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in the electrolytes of each embodiment and comparative example are shown in Table 1 below.

[0115] The mass ratios of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate in the electrolytes of each embodiment and comparative example are shown in Table 1 below. The total molar concentration of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate in the electrolyte is 1 mol / L.

[0116] (2) Preparation of positive electrode 11: Lithium iron phosphate (LiFePO4), conductive carbon black (Super-P), and binder (polyvinylidene fluoride, PVDF) are mixed in a mass ratio of 94:3:3; then N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode slurry with a solid content of 60wt%, and stirred evenly. The positive electrode slurry is then uniformly coated on one surface of an aluminum foil (positive electrode current collector 111) with a thickness of 10μm. After drying, cold pressing, slitting, and die cutting, the positive electrode 11 to be wound is obtained. The single-sided thickness of the positive electrode active layer 112 is 100μm.

[0117] (3) Preparation of negative electrode sheet 13: The negative electrode active material artificial graphite, the thickener sodium carboxymethyl cellulose (CMC), the conductive carbon black (Super-P), and the binder styrene-butadiene rubber emulsion (SBR) are mixed in a mass ratio of 96:2:1:1. Deionized water is added to prepare a negative electrode slurry with a solid content of 50wt%, and the mixture is stirred evenly. The negative electrode slurry is uniformly coated on one surface of a copper foil (negative electrode current collector 131) with a thickness of 6μm. After drying, cold pressing, slitting, and die-cutting, the negative electrode sheet to be wound is obtained. The single-sided thickness of the negative electrode active layer 132 is 70μm.

[0118] (4) Preparation of diaphragm 12: 16 μm polyethylene film (PE) is used as diaphragm 12.

[0119] (5) Assembly of battery 100: The positive electrode 11, separator 12, and negative electrode 13 are stacked in sequence, with the separator 12 acting as a separator between the positive electrode 11 and the negative electrode 13. Then, they are wound into a cylindrical electrode assembly 10. After welding the tabs, the electrode assembly 10 with the tabs is placed in the outer casing assembly 20. After drying, the electrolyte is injected. The battery 100 is then prepared by processes such as standing at room temperature, formation, secondary injection, aging, welding, helium testing, capacity testing, and OCV testing. The area of ​​the second explosion-proof valve 233 in the outer casing assembly 20 is 110 mm². 2 The areas of the first explosion-proof valve 212 and the second explosion-proof valve 233 of the housing assembly 20 are shown in Table 1 below.

[0120] Various performance tests were conducted on the above embodiments and comparative examples.

[0121] (1) Method for determining the low-temperature freezing point of electrolyte: Take 30g of electrolyte from each example and comparative example and place it in a 50ml transparent glass bottle. Place it in a high and low temperature cabinet with a test range of -60℃ to 100℃. Start from -10℃ and gradually decrease the temperature in a 2℃ gradient. After each temperature decrease, record the phenomenon after stabilizing for 1 hour until the electrolyte solidifies. Record the freezing point of the electrolyte (i.e., the freezing temperature of the electrolyte).

[0122] (2) Charge-discharge cycle test: The batteries 100 of each embodiment and comparative example were subjected to constant current charge-discharge cycle test on a charge-discharge instrument. The test temperature was 25°C, the charge-discharge rate was 1C, and the charge-discharge voltage window was 2.5V to 3.65V. The capacity retention rate after 300 cycles was calculated.

[0123] The calculation formula is: Capacity retention rate after the nth cycle = (Discharge capacity after the nth cycle / Discharge capacity of the first cycle) × 100%. Here, one complete charge-discharge cycle is usually called a charge-discharge cycle. That is, battery 100 first charges from 2.5V to 3.65V, then discharges from 3.65V back to 2.5V, thus forming one charge-discharge cycle. N cycles mean repeating the above process N times.

[0124] (3) Thermal runaway test: 1) Charge the battery 100 to be tested to 100% State of Charge (SOC) and place the initialized battery 100 in the thermal runaway test device; 2) Select heating components and temperature sensors and set them on the surface of the battery 100 to be tested. Set the temperature sampling period to 1 second and verify that three consecutive temperature rise rate values ​​> 3℃ / s, or fire or explosion are used as the judgment conditions for thermal runaway; 3) Connect the battery 100 to be tested to the charging and discharging device and its voltage data sampling line; 4) Charge with constant current I = P / U, start heating, and record the status and rupture mode of the first explosion-proof valve 212 and the second explosion-proof valve 233; 5) When the judgment conditions for thermal runaway are triggered, or the temperature reaches 300℃ or the test time reaches 4 hours, stop charging and heating, observe for 1 hour, and record the status and rupture mode of the first explosion-proof valve 212 and the second explosion-proof valve 233.

[0125] The performance test results of each embodiment and comparative example are shown in Table 2 below.

[0126] Table 1. Parameter design of battery 100 in each embodiment and comparative example.

[0127] Table 2 Performance parameters of battery 100 in each embodiment and comparative example

[0128] As shown in Table 1, the test results of Examples 1 to 5 indicate that, under otherwise unchanged conditions, when the mass ratio A of cyclic carbonate to chain carbonate is low and B / A is too high, the battery 100 has a low low-temperature freezing point, but its 300-cycle capacity retention rate is low. As the mass ratio A of cyclic carbonate to chain carbonate increases, the low-temperature freezing point of the electrolyte gradually increases, and the battery 100 has a high cycle capacity retention rate after 300 cycles at room temperature (all of Examples 2 to 4 are greater than or equal to 88.1%). The cycle capacity retention of the battery 100 first gradually increases and then gradually decreases. Moreover, during the thermal runaway test, at least one of the first explosion-proof valve 212 and the second explosion-proof valve 233 of the battery 100 can be depressurized to prevent the battery 100 from exploding. When the mass ratio A of cyclic carbonate to chain carbonate is too high (as in Example 5), the low-temperature freezing point of battery 100 increases significantly, the capacity retention rate after 300 cycles decreases significantly, and when battery 100 undergoes thermal runaway, valves burst on both sides. This indicates that when battery 100 is overcharged, more gas is produced and the gas pressure inside battery 100 is high.

[0129] The test results from Examples 3, 6 to 9 show that, under otherwise unchanged conditions, if the ratio of the first explosion-proof valve 212 to the second explosion-proof valve 233 is too large or too small, it will not meet the design requirements of the battery 100. When the area ratio B of the first explosion-proof valve 212 to the second explosion-proof valve 233 is between 1.5 and 3, at least one of the first explosion-proof valve 212 and the second explosion-proof valve 233 can burst during the overcharge thermal runaway test of the battery 100, thereby relieving pressure on the battery 100 and preventing the battery 100 from exploding.

[0130] The test results from Examples 3, 18 to 22 show that, under otherwise unchanged conditions, when the aspect ratio of battery 100 is 2.43 ≤ L / D ≤ ​​5.98, at least one of the first explosion-proof valve 212 and the second explosion-proof valve 233 can depressurize the battery 100 during the thermal runaway test, thus preventing the battery 100 from exploding. When the aspect ratio of battery 100 is too large, the battery 100 is prone to explosion during overcharging. When the aspect ratio of battery 100 is 2.43 ≤ L / D ≤ ​​5.98, as the aspect ratio increases, the room temperature cycle capacity of battery 100 after 300 cycles gradually increases first, then gradually decreases, but remains greater than or equal to 88.23%.

[0131] The test results from Examples 3, 23, and 24 show that when the mass ratio A1 of methyl ethyl carbonate to dimethyl carbonate is 0.5 ≤ A1 ≤ 2, the low-temperature freezing point of the electrolyte decreases and the cycle capacity retention rate of battery 100 slightly increases as the mass ratio A1 of methyl ethyl carbonate to dimethyl carbonate in the electrolyte increases. When the mass ratio A1 of methyl ethyl carbonate to dimethyl carbonate is 0.5 ≤ A1 ≤ 2, the low-temperature freezing point range of the electrolyte can cover -30℃ to -64℃.

[0132] The test results from Examples 3, 10 to 17, 23, and 25 to 32 show that, under otherwise unchanged conditions, when the mass ratio G of lithium difluorosulfonyl imide to lithium hexafluorophosphate is small (as in Example 10), the electrolyte has a lower freezing point, but the capacity retention of battery 100 after 300 cycles at room temperature is low. As the mass ratio G of lithium difluorosulfonyl imide to lithium hexafluorophosphate increases (as in Examples 11 to 16), the freezing point of the electrolyte gradually increases. As the capacity of battery 100 increases gradually, it first gradually increases and then gradually decreases after 300 cycles at room temperature. In the event of thermal runaway, at least one of the first explosion-proof valve 212 and the second explosion-proof valve 233 of battery 100 can be depressurized to prevent battery 100 from exploding. When the mass ratio G of lithium difluorosulfonylimide to lithium hexafluorophosphate is too large (as in Example 17), the low-temperature freezing point of the electrolyte is too high. During the thermal runaway test, the entire battery 100 explodes, and the safety performance deteriorates.

[0133] The test results from Examples 10 to 17 show that when the mass ratio of methyl ethyl carbonate to dimethyl carbonate in the electrolyte is high, the battery 100 has a lower freezing point. At this time, the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate in the electrolyte also has a significant impact on the freezing point of the electrolyte. As the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate increases, the freezing point of the electrolyte increases rapidly.

[0134] The test results from Examples 23, 25 to 32 show that when the mass ratio of ethyl methyl carbonate to dimethyl carbonate in the electrolyte is low, the battery 100 has a higher low-temperature freezing point. At this time, the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate in the electrolyte has a relatively small effect on the low-temperature freezing point of the electrolyte. As the mass ratio G of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate increases, the low-temperature freezing point of the electrolyte gradually increases, but the increase is relatively slow.

[0135] The test results from Examples 1 to 9 and Comparative Examples 1 to 4 show that when 0.17≤A≤0.67, 1.5≤B≤3, and 2.23≤B / A≤17.65 are satisfied simultaneously, the battery 100 has a high cycle capacity retention rate (the capacity retention rate after 300 cycles is ≥87.32%, with a maximum of 94.21%), and also has high safety performance. In case of overcharging, at least one of the first explosion-proof valve 212 and the second explosion-proof valve 233 can be used to release pressure on the battery 100 and avoid the risk of the battery 100 exploding.

[0136] As can be seen from the test results of Comparative Example 1, when B > 3, B / A > 17.65, and L / D > 5.98 for the first explosion-proof valve 212 and the second explosion-proof valve 233, the entire battery 100 explodes during the thermal runaway test.

[0137] The test results of Comparative Example 2 show that when B of the first explosion-proof valve 212 and the second explosion-proof valve 233 is less than 1.5 and B / A < 2.43, the design requirements of battery 100 are not met.

[0138] The test results of Comparative Example 3 show that when A < 0.17, B > 3, and B / A > 17.65, the electrolyte has a low freezing point, but battery 100 does not meet the design requirements.

[0139] The test results of Comparative Example 4 show that when A > 0.67, B < 1.5, and B / A < 2.23, the low-temperature freezing point of the electrolyte is relatively high, and the capacity retention rate of Battery 100 after 300 cycles is greatly reduced.

[0140] The test results of Comparative Example 5 show that when B > 3, G < 0.1, B / A > 17.65, and G / B < 0.03, the electrolyte has a low freezing point, but battery 100 does not meet the design requirements.

[0141] The test results of Comparative Example 6 show that when B < 1.5, G > 14.8, and G / B > 13.33, the low-temperature freezing point of the electrolyte increases, but remains relatively low. The capacity retention rate of battery 100 after 300 cycles is also relatively high. When battery 100 undergoes thermal runaway testing, double-sided explosion valves occur, indicating that when battery 100 is overcharged, more gas is produced and the gas pressure inside battery 100 is relatively high.

[0142] Please refer to Figure 8. This application embodiment also provides an energy storage device 200, which includes a housing 210 and a plurality of batteries 100 as described in this application embodiment. The plurality of batteries 100 are stacked and housed in the housing 210.

[0143] The term "multiple" refers to two or more.

[0144] Understandably, the multiple batteries 100 of the energy storage device 200 can be connected in parallel, or in series, or partially in parallel and partially in series (in other words, mixed connection). This application does not make specific limitations on the connection method of the multiple batteries 100 of the same energy storage device 200.

[0145] Optionally, the energy storage device can be at least one of small energy storage boxes, large energy storage cabinets, energy storage modules, etc. This application does not specifically limit the form of the energy storage device. The form of the energy storage device in this application is only one of many forms and should not be construed as a limitation on the energy storage device in this application.

[0146] Understandably, the housing 210 has accommodating cavities in which multiple batteries 100 are housed. In some embodiments, each accommodating cavity houses one battery 100. In other embodiments, each accommodating cavity houses multiple batteries 100.

[0147] Please refer to Figures 9 and 10. This application embodiment also provides an energy storage system 300, which includes: an energy conversion device 310 and an energy storage device 200 as described in this application embodiment. The energy conversion device 310 is electrically connected to the energy storage device 200. The energy conversion device 310 is used to convert other forms of energy into electrical energy, and the energy storage device 200 is used to store the electrical energy.

[0148] Optionally, the power conversion device 310 can convert at least one other form of energy, such as solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy, into electrical energy.

[0149] Optionally, the number of power conversion devices 310 can be one or more. When there are multiple power conversion devices 310, the multiple power conversion devices 310 can be connected in series or in parallel. This application does not make specific limitations.

[0150] Optionally, the power conversion device 310 may be, but is not limited to, at least one of photovoltaic panels, wind power generation devices, hydropower generation devices, etc.

[0151] Optionally, the number of energy storage devices 200 can be one or more. When there are multiple energy storage devices 200, the multiple energy storage devices 200 can be connected in series or in parallel. This application does not make specific limitations.

[0152] During operation, the power conversion device 310 converts other forms of energy into electrical energy and stores it in the energy storage device 200. The electrical energy stored in the energy storage device 200 can be used to supply electrical loads such as streetlights and household appliances during peak electricity prices, or to supply power when the power grid experiences a power outage. The electrical energy generated by the power conversion device 310 can also be supplied to the power grid through high-voltage cables to alleviate the power supply pressure on the power grid during peak periods.

[0153] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various places in the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A battery, wherein, include: An electrode assembly, comprising a positive electrode, a separator, and a negative electrode; An electrolyte comprising an electrolyte salt and an organic solvent, wherein the organic solvent comprises cyclic carbonates and chain carbonates, and the mass ratio of the cyclic carbonates to the chain carbonates is A; as well as An outer casing assembly includes a first end cap assembly, a housing, and a second end cap assembly. The housing is a hollow structure. The first end cap assembly and the second end cap assembly are respectively disposed at opposite ends of the housing, forming a receiving cavity. The first end cap assembly includes a first top cover and a first explosion-proof valve connected together. The first top cover is disposed around the outer periphery of the first explosion-proof valve and is electrically connected to the positive electrode plate. The second end cap assembly includes a second top cover, a negative electrode post, and a second explosion-proof valve. The second top cover is disposed around the second explosion-proof valve. The negative electrode post passes through the second top cover and protrudes from the side of the second top cover opposite to the housing. The negative electrode post is electrically connected to the negative electrode plate. The area ratio of the first explosion-proof valve to the second explosion-proof valve is B. The battery satisfies the following relationship: 2.23≤B / A≤17.

65.

2. The battery according to claim 1, wherein, The mass ratio A of the cyclic carbonate to the chain carbonate is in the range of 0.17 ≤ A ≤ 0.

67.

3. The battery according to claim 1, wherein, The cyclic carbonate includes ethylene carbonate, and the chain carbonate includes methyl ethyl carbonate and dimethyl carbonate, wherein the mass ratio A1 of methyl ethyl carbonate to dimethyl carbonate is in the range of 0.5 ≤ A1 ≤ 2.

4. The battery according to claim 1, wherein, The area ratio B between the first explosion-proof valve and the second explosion-proof valve is in the range of 1.5 ≤ B ≤ 3.

5. The battery according to claim 1, wherein, The area b1 of the first explosion-proof valve is 120 mm. 2 ≤b1≤240mm 2 The area b2 of the second explosion-proof valve is 90mm². 2 ≤b2≤160mm 2 .

6. The battery according to any one of claims 1-5, wherein, The electrolyte salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide, and the mass ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate is G; the battery also satisfies the relationship: 0.03≤G / B≤9.

87.

7. The battery according to claim 6, wherein, The mass ratio G of the lithium difluorosulfonylimide to the lithium hexafluorophosphate is in the range of 0.1 ≤ G ≤ 14.

8.

8. The battery according to any one of claims 1-5, 7, wherein, The battery is cylindrical, and the ratio of the battery's length L to its diameter D, L / D, is in the range of 2.43 ≤ L / D ≤ ​​5.

98.

9. A battery, wherein, include: An electrode assembly, comprising a positive electrode, a separator, and a negative electrode; An electrolyte comprising an electrolyte salt, wherein the electrolyte salt comprises lithium difluorosulfonyl imide and lithium hexafluorophosphate, wherein the mass ratio of lithium difluorosulfonyl imide to lithium hexafluorophosphate is G; as well as The housing assembly includes a first end cap assembly, a housing, and a second end cap assembly. The housing is a hollow structure. The first end cap assembly and the second end cap assembly are respectively disposed at opposite ends of the housing. The first end cap assembly, the housing, and the second end cap assembly form a receiving cavity for housing the electrode assembly and the electrolyte. The first end cap assembly includes a first top cover and a first explosion-proof valve. The first top cover is disposed around the outer periphery of the first explosion-proof valve and is electrically connected to the positive electrode plate. The second end cap assembly includes a second top cover, a negative electrode post, and a second explosion-proof valve. The second top cover is disposed around the outer periphery of the second explosion-proof valve. The negative electrode post passes through the second top cover and protrudes from the side of the second top cover opposite to the housing. The negative electrode post is electrically connected to the negative electrode plate. The area ratio of the first explosion-proof valve to the second explosion-proof valve is B. The battery satisfies the following relationship: 0.03≤G / B≤9.

87.

10. The battery according to claim 9, wherein, The mass ratio G of the lithium difluorosulfonylimide to the lithium hexafluorophosphate is in the range of 0.1 ≤ G ≤ 14.

8.

11. The battery according to claim 9, wherein, The area ratio B between the first explosion-proof valve and the second explosion-proof valve is in the range of 1.5 ≤ B ≤ 3.

12. The battery according to claim 9, wherein, The area of ​​the first explosion-proof valve, b1, is 120 mm. 2 ≤b1≤240mm 2 The area of ​​the second explosion-proof valve, b2, is 90 mm². 2 ≤b2≤160mm 2 .

13. The battery according to any one of claims 9-12, wherein, The outer shell assembly is cylindrical, and the central axis of the outer shell assembly extends along the arrangement direction of the first end cap assembly, the housing and the second end cap assembly. The length L of the outer shell assembly and the diameter D of the outer shell assembly satisfy the relationship: 2.43≤L / D≤5.

98.

14. An energy storage device, wherein, include: Box; as well as The battery according to any one of claims 1-13, wherein the plurality of batteries are housed in the housing.

15. An energy storage system, wherein, include: The power conversion device and the energy storage device according to claim 14, wherein the power conversion device is electrically connected to the energy storage device, the power conversion device is used to convert other forms of energy into electrical energy, and the energy storage device is used to store the electrical energy.

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