Lithium-ion battery, battery module, battery pack, and electric device

Abstract

The application provides a lithium ion battery, which comprises an electrode assembly and an electrolyte containing fluorosulfonate and / or difluorophosphate substances. The formation gas production area coefficient of the lithium ion battery is α, α=M×S / 200, M is the loading amount of the negative electrode material on the negative electrode current collector per unit area, M ranges from 5 mg / cm 2 ~100 mg / cm 2 , S is the specific surface area of the negative electrode material on the negative electrode current collector, S ranges from 0.1 m 2 / g to 10 m 2 / g; the exhaust path coefficient of the lithium ion battery is β, β=100 / L, L is the width of the coating area of the negative electrode material on the surface of the negative electrode current collector, L ranges from L≥50 mm; the mass percentage content w% of the fluorosulfonate and / or difluorophosphate substances in the electrolyte and α and β satisfy 0.01≤w×β / α≤20. The lithium ion battery provided by the application can balance high energy density and low formation gas production.

Description

[0001] This application is a divisional application of patent application 202110138000.8, filed on February 1, 2021, entitled "Lithium-ion battery, battery module, battery pack, and electrical device". Technical Field

[0002] This application relates to lithium-ion batteries, and more particularly to a high-energy-density, low-gas-production lithium-ion battery and its preparation method, battery module, battery pack, and power-consuming device. Background Technology

[0003] With the rapid development of the new energy field, lithium-ion batteries are widely used in various large-scale power devices, energy storage systems and various consumer products due to their excellent electrochemical performance, no memory effect and low environmental pollution, especially in the field of new energy vehicles such as pure electric vehicles and hybrid electric vehicles.

[0004] In the field of new energy vehicles, consumers have placed higher demands on the driving range of lithium-ion batteries. However, current lithium-ion batteries are insufficient to meet these increased demands, making the development of lithium-ion batteries with higher energy density one of the main directions of lithium-ion battery research and development.

[0005] However, during the formation process of high-energy-density batteries, while a stable SEI film forms on the negative electrode, the solvent and some additives in the electrolyte are reduced or decomposed, leading to severe internal gas generation. Moreover, this internal gas generation is more severe in high-energy-density batteries compared to low-energy-density batteries. If the gases generated during formation, such as methane, ethane, ethylene, and carbon monoxide, cannot be discharged in time, bubbles will form between the positive and negative electrodes, affecting the insertion and extraction of lithium ions. This results in increased internal resistance, black spots at the negative electrode interface, localized lithium plating at the negative electrode interface, and abnormal capacity performance, ultimately affecting the battery's electrical and safety performance.

[0006] Therefore, there is an urgent need to develop a lithium-ion battery with high energy density and low formation gas production. Summary of the Invention

[0007] This application addresses the aforementioned issues and aims to provide a lithium-ion battery with high energy density and low gas production, as well as a battery module, battery pack, and power-consuming device. The lithium-ion battery of this application not only improves the energy density of lithium-ion batteries but also significantly reduces formation gas production and black spot lithium deposition, thereby enhancing the electrochemical and safety performance of lithium-ion batteries.

[0008] One objective of this application is to provide a lithium-ion battery with high energy density.

[0009] One objective of this application is to provide a high-energy-density lithium-ion battery with low formation gas production.

[0010] One objective of this application is to provide a lithium-ion battery with significantly improved negative electrode black spots and lithium plating phenomenon.

[0011] One objective of this application is to provide a high-energy-density lithium-ion battery with low internal resistance.

[0012] One object of this application is to provide a high energy density lithium-ion battery with improved cycle performance.

[0013] The inventors have discovered that by adopting the technical solution of this application, one or more of the above-mentioned objectives can be achieved.

[0014] This application provides a lithium-ion battery, comprising:

[0015] An electrode assembly, the electrode assembly comprising a negative electrode current collector and a negative electrode material disposed on at least one surface of the negative electrode current collector; and

[0016] The electrolyte contains fluorosulfonates and / or difluorophosphates.

[0017] Let the formation gas production area factor of the lithium-ion battery be α, α=M×S / 200 Equation (I),

[0018] In equation (I), M represents the loading of negative electrode material on the negative electrode current collector per unit area, with units of mg / cm². 2 The range of M is 5 mg / cm³. 2 ~100mg / cm 2 ,

[0019] In the above formula (I), S is the specific surface area of ​​the negative electrode material on the negative electrode current collector, and its unit is m². 2 / g, where S ranges from 0.1m 2 / g~10m 2 / g,

[0020] Let the exhaust path coefficient of the lithium-ion battery be β, β = 100 / L (Equation II).

[0021] In formula (II), L is the width of the coating area of ​​the negative electrode material on the surface of the negative electrode current collector, and its unit is mm. The range of L is L≥50mm.

[0022] Wherein, the mass percentage w% of the fluorosulfonate and / or difluorophosphate substances in the electrolyte, the formation gas production area coefficient α of the lithium-ion battery and the exhaust coefficient β of the lithium-ion battery satisfy 0.01≤w×β / α≤20 Equation (III).

[0023] Through extensive research and experimentation, the inventors of this application have discovered that when the mass percentage of fluorosulfonates and / or difluorophosphates in the electrolyte, the formation gas production area coefficient, and the exhaust path coefficient, β, satisfy the relationship 0.01≤w×β / α≤20, the lithium-ion battery exhibits improved energy density and very low formation gas production. This effectively prevents black spots and lithium plating at the negative electrode during formation, thus improving the battery's internal resistance and electrical performance.

[0024] This application starts with the structure of the lithium-ion battery itself, and by jointly controlling various structural parameters of the battery as well as the types and contents of electrolyte additives, it integrates the synergistic effect of various internal structural parameters and electrolyte parameters to obtain a high-energy-density lithium-ion battery. At the same time, it solves the problems of severe gas generation and lithium deposition on the negative electrode during the formation process of high-energy-density lithium-ion batteries, and significantly improves the internal resistance and electrical performance of lithium-ion batteries.

[0025] Optionally, in any embodiment, the fluorosulfonate has the structural formula (FSO3). y M y+ M y+ Selected from Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3+ Fe 2+ Fe 3+ Ni 2+ and Ni 3+ One of them.

[0026] Optionally, in any embodiment, the difluorophosphate has the structural formula (F₂PO₂). y M y+ M y+ Selected from Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3+ Fe2+ Fe 3+ Ni 2+ and Ni 3+ One of them.

[0027] In any embodiment, optionally, the mass percentage (w%) of the fluorosulfonate and / or difluorophosphate in the electrolyte ranges from 0.01% to 11%, optionally from 0.5% to 10%, and further optionally from 0.5% to 5%.

[0028] In the design process of the high-energy-density lithium-ion battery of this application, adding an appropriate amount (0.01% to 11%) of fluorosulfonates and / or difluorophosphates to the electrolyte can significantly reduce the amount of gas generated during formation. By setting the amount of fluorosulfonates and / or difluorophosphates added within a suitable range, black spots on the negative electrode can be avoided, and the increase in electrolyte viscosity can be prevented from affecting the electrolyte conductivity and thus increasing the internal resistance of the battery.

[0029] Optionally, the mass percentage (w%) of the fluorosulfonate and / or difluorophosphate in the electrolyte can be 0.5% to 10%.

[0030] Optionally, the mass percentage (w%) of the fluorosulfonate and / or difluorophosphate in the electrolyte can be 0.5% to 5%.

[0031] Specifically, when the mass percentage (w%) of fluorosulfonates and / or difluorophosphates in the electrolyte is in the range of 0.5% to 10%, there is no black spot phenomenon at the negative end, and the lithium-ion battery has significantly improved formation gas production, and the battery volumetric energy density and battery internal resistance are also at a better level.

[0032] Furthermore, when the mass percentage (w%) of fluorosulfonates and / or difluorophosphates in the electrolyte is in the range of 0.5% to 5%, the corresponding lithium-ion battery also exhibits excellent high-temperature cycling characteristics and room-temperature cycling characteristics.

[0033] In any embodiment, optionally, the loading M of the negative electrode material on the negative electrode current collector per unit area ranges from 11 mg / cm². 2 ~80mg / cm 2 11 mg / cm³ is an option. 2 ~50mg / cm 2 .

[0034] When the loading M of the negative electrode material on the negative electrode current collector per unit area is relatively small (M is less than 11 mg / cm²), 2This negatively impacts the volumetric energy density of lithium-ion batteries. When the load is within a suitable range, it can prevent an increase in the contact area between the negative electrode material and the electrolyte, thereby preventing intensified gas formation and increased internal resistance of the battery.

[0035] In any embodiment, optionally, the specific surface area S of the negative electrode material on the negative electrode current collector is in the range of 0.5 m². 2 / g~5m 2 / g.

[0036] When the specific surface area S of the negative electrode material is within a suitable range, it can improve the reaction kinetics at the interface between the electrolyte and the negative electrode material, thereby reducing the interfacial reaction resistance and increasing the battery energy density.

[0037] On the other hand, it can reduce the amount of gas produced by chemical formation and avoid black spots from appearing at the negative extreme.

[0038] In any embodiment, optionally, the width L of the coating area of ​​the negative electrode material on the surface of the negative electrode current collector is in the range of 50mm≤L≤200mm, or optionally 50mm≤L≤100mm.

[0039] When the width L of the coating area of ​​the negative electrode material is within a suitable range, on the one hand, it can avoid the diffusion path of the gas generated by formation becoming longer, thus not affecting the gas discharge rate and avoiding the occurrence of black spots that would affect the internal resistance of the battery; on the other hand, it can reduce the impact on the energy density of the lithium-ion battery.

[0040] In any embodiment, optionally, the electrolyte contains fluoroethylene carbonate and / or 1,3-propanesulfonate lactone.

[0041] Extensive experiments and research have shown that adding additional fluoroethylene carbonate (FEC) and / or 1,3-propanesulfonate lactone (PS) to an electrolyte containing fluorosulfonate and / or difluorophosphate can significantly improve the high and low temperature cycling performance of lithium-ion batteries while ensuring high energy density and low formation gas production.

[0042] In any embodiment, the porosity of the negative electrode material is optionally 10% to 40%.

[0043] Research shows that the higher the porosity of the negative electrode material, the more numerous and unobstructed the diffusion paths of the gas generated during formation from the interior of the negative electrode material to the interface between the negative electrode and the separator. However, when the porosity of the negative electrode material exceeds 50%, the volumetric energy density of the lithium-ion battery decreases. When the porosity of the negative electrode material is below 10%, the resistance to lithium ion insertion / extraction is relatively large, thus affecting the internal resistance of the battery.

[0044] By limiting the porosity of the negative electrode material to 10% to 40%, the gas generated inside the negative electrode material can diffuse out quickly, while also ensuring that the battery has a high volumetric energy density and a low internal resistance.

[0045] A second aspect of this application provides a battery module, including the lithium-ion battery of the first aspect of this application.

[0046] A third aspect of this application provides a battery pack, including a lithium-ion battery of the first aspect of this application or a battery module of the second aspect of this application.

[0047] A fourth aspect of this application provides an electrical device, including a lithium-ion battery as described in the first aspect of this application.

[0048] At least one of the battery module of the second aspect of this application or the battery pack of the third aspect of this application. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of a lithium-ion battery according to one embodiment of this application.

[0050] Figure 2 yes Figure 1 An exploded view of a lithium-ion battery according to an embodiment of this application is shown.

[0051] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0052] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0053] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0054] Figure 6 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0055] Explanation of reference numerals in the attached figures:

[0056] 1 Battery Pack

[0057] 2 Upper box

[0058] 3 lower box

[0059] 4 Battery Modules

[0060] 5. Lithium-ion batteries

[0061] 51. Housing

[0062] 52 Electrode Assembly

[0063] 53 Top Cover Assembly Detailed Implementation

[0064] The high-energy-density, low-gas-production lithium-ion battery, battery module, battery pack, and power supply device of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0065] For the sake of brevity, this application specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0066] In conventional lithium-ion battery strategies to reduce formation gas generation, a common solution is to reduce the formation current to decrease the gas generation rate and to accelerate gas extraction by applying negative pressure to ensure timely removal of gas from the battery. However, through in-depth research by the inventors of this application, it has been found that with the increase in the energy density of the designed batteries, especially for wound batteries, this conventional method cannot remove formation gas in time, leading to degradation of the formation interface.

[0067] Another way to reduce gas production is to use a low-current, segmented pressurization formation method. However, this method is complicated and time-consuming, has poor operational stability, and is not conducive to large-scale industrial applications.

[0068] Therefore, it is evident that simply adjusting certain processes or steps in the formation of lithium-ion batteries is insufficient to address the gas generation problem during lithium-ion battery formation. Thus, the most feasible approach to finding a long-term and effective solution to this problem lies in addressing the structure of the lithium-ion battery itself. This involves jointly controlling various structural parameters of the battery, as well as the type and content of electrolyte additives, to develop and design lithium-ion batteries with low formation gas generation.

[0069] Through extensive research and experimentation, the inventors developed and designed a high-energy-density lithium-ion battery with low formation gas production, starting from the perspective of developing and designing a high-energy-density lithium-ion battery with low formation gas production. This was achieved by comprehensively controlling the structural parameters of the electrode components and the type and content of the electrolyte. Specifically, this involved jointly controlling the loading amount of active material on the current collector per unit area, the specific surface area of ​​the active material loaded on the current collector, the coating area length of the active material, and adding fluorosulfonate and / or difluorophosphate to the electrolyte. By comprehensively utilizing the synergistic effects of various parameters, the inventors developed and designed a high-energy-density lithium-ion battery with low formation gas production, starting from the structure of the lithium-ion battery itself.

[0070] Furthermore, through extensive research and experimentation by the inventors, when the content of fluorosulfonate and / or difluorophosphates satisfies a certain relationship with the loading of active material on the current collector per unit area, the specific surface area of ​​the active material loaded on the current collector, and the length of the coating area of ​​the active material, a lithium-ion battery that satisfies this relationship has both significantly improved high energy density and reduced formation gas production.

[0071] The theoretical formula proposed in this application is not limited to one type of battery structure. It is also applicable when the shape of the battery, the winding method of the bare cells, or the stacking method of the bare cells are changed due to other requirements.

[0072] [Lithium-ion battery]

[0073] Typically, a lithium-ion battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0074] This application provides a lithium-ion battery, comprising:

[0075] An electrode assembly, the electrode assembly comprising a negative electrode current collector and a negative electrode material disposed on at least one surface of the negative electrode current collector; and

[0076] The electrolyte contains fluorosulfonates and / or difluorophosphates.

[0077] Let the formation gas production area factor of the lithium-ion battery be α, α=M×S / 200 Equation (I),

[0078] In equation (I), M represents the loading of negative electrode material on the negative electrode current collector per unit area, with units of mg / cm². 2 The range of M is 5 mg / cm³. 2 ~100mg / cm 2,

[0079] In the above formula (I), S is the specific surface area of ​​the negative electrode material on the negative electrode current collector, and its unit is m². 2 / g, where S ranges from 0.1m 2 / g~10m 2 / g,

[0080] Let the exhaust path coefficient of the lithium-ion battery be β, β = 100 / L (Equation II).

[0081] In formula (II), L is the width of the coating area of ​​the negative electrode material on the surface of the negative electrode current collector, and its unit is mm. The range of L is L≥50mm.

[0082] Wherein, the mass percentage w% of the fluorosulfonate and / or difluorophosphate substances in the electrolyte, the formation gas production area coefficient α of the lithium-ion battery and the exhaust coefficient β of the lithium-ion battery satisfy 0.01≤w×β / α≤20 Equation (III).

[0083] Through extensive research and experimentation, the inventors have found that designing and developing a lithium-ion battery with high energy density and low formation gas production requires comprehensive control of various parameters related to improving battery energy density, reducing formation gas production, and both, rather than controlling only one parameter.

[0084] Specifically, gas generation during formation mainly occurs when organic components in the electrolyte, such as organic solvents or organic additives, are reduced and decomposed on the surface of the negative electrode material during the formation process, forming an interfacial protective film. Increasing the loading M of the negative electrode material on the current collector per unit area can significantly improve the volumetric energy density of the battery, but it will also correspondingly increase the contact area between the negative electrode material and the electrolyte, leading to more electrolyte reduction and decomposition and the generation of more gas.

[0085] Similarly, selecting a negative electrode material with a larger specific surface area S can increase the contact area between the negative electrode material and the electrolyte, reduce the transport resistance of lithium ions at the phase interface, and thus improve the energy density of the battery. However, the increased contact area between the negative electrode material and the electrolyte will also cause more electrolyte to be reduced and decomposed, thereby generating more gas.

[0086] Therefore, under the premise of ensuring that the designed lithium-ion battery has a high energy density (M ranges from 5 mg / cm³), 2 ~100mg / cm 2 The range of S is 0.1m. 2 / g~10m 2From the perspective of gas generation during the formation process, the specific surface area S of the negative electrode material and the loading M of the negative electrode material on the current collector per unit area both affect the formation gas production by influencing the contact area between the electrolyte and the negative electrode material. Therefore, this application defines a formation gas production area coefficient α related to M and S. The formation gas production area coefficient α can characterize the relationship between the contact area between the electrolyte and the negative electrode material and the formation gas production as a whole. Through extensive research and experiments by the inventors, M, S, and α satisfy the relationship α=M×S / 200.

[0087] On the other hand, considering the exhaust of gases from inside the battery, when developing and designing the lithium-ion battery of this application, a larger width L of the coating area of ​​the negative electrode material on the surface of the negative electrode current collector is beneficial to improving the volumetric energy density of the battery. However, it also increases the length of the exhaust path for gases inside the battery. In the actual design of bare cells, in order to further increase the volumetric energy density, L needs to be designed to be as long as possible, but an excessively long L is not conducive to the rapid exhaust of formation-generated gases.

[0088] Therefore, under the premise of ensuring high energy density of the designed lithium-ion battery (L ≥ 50 mm), from the perspective of timely gas discharge during the formation process, the width L of the coating area of ​​the negative electrode material affects the gas production during formation by influencing the length of the gas diffusion path. Therefore, this application defines a gas discharge path coefficient β related to L, the magnitude of which indicates the ease or difficulty of discharging the gas generated during formation. Through extensive research and experimentation, the inventors have determined that L and β satisfy the relationship β = 100 / L.

[0089] On the other hand, from the perspective of reducing the amount of gas generated during the formation process, improving the electrolyte formulation is a more effective way to improve gas production during formation. Common electrolytes for lithium-ion batteries often include organic solvents and organic additives. During formation, these organic components preferentially reduce on the negative electrode surface to form a protective film at the negative electrode interface, while simultaneously generating gaseous products. Based on this, this application improves the electrolyte formulation by replacing some conventional organic additives with inorganic additives such as fluorosulfonates or difluorophosphates. These inorganic additives can preferentially reduce on the negative electrode surface compared to organic solvents, directly reducing to form an inorganic coating layer on the surface of graphite and other negative electrode active materials. Therefore, no gaseous products are formed, and the problem of gas generation from additive decomposition is eliminated.

[0090] Furthermore, since an inorganic coating layer has been preferentially formed on the surface of the negative electrode active material, the reduction and decomposition of the electrolyte solvent on the negative electrode surface can be effectively suppressed, thereby further reducing the amount of gas generated by the reduction and decomposition of the electrolyte solvent.

[0091] Therefore, under the premise of ensuring that the designed lithium-ion battery has a high energy density (M ranges from 5 mg / cm³),2 ~100mg / cm 2 The range of S is 0.1m. 2 / g~10m 2 / g, L range is L≥50mm). From the perspective of gas generation during the formation process, improving the electrolyte formulation is the fundamental way to reduce gas generation during the entire battery design and development process.

[0092] However, after extensive research and experimentation by the inventors, it was found that adding too many inorganic salt additives to the electrolyte increases the viscosity of the electrolyte, worsens the electrolyte conductivity, and to some extent hinders the migration rate of lithium ions in the electrolyte, thereby increasing the internal resistance of the battery.

[0093] As can be seen from the above three aspects, the development and design of lithium-ion batteries with high energy density and low formation gas production is the result of the synergistic effect of various parameters. When the value of one related parameter changes, the values ​​of other related parameters need to be changed accordingly in order to ensure that the battery volumetric energy density and formation gas production are maintained within their respective optimal ranges.

[0094] Taking into account various parameters related to improving battery energy density, reducing formation gas production, and both, the inventors of this application, through extensive research and experimentation, discovered that when the mass percentage of fluorosulfonates and / or difluorophosphates in the electrolyte, the formation gas production area coefficient, and the exhaust path coefficient, β, satisfy the relationship 0.01≤w×β / α≤20, the resulting lithium-ion battery exhibits significantly improved energy density and very low formation gas production. This effectively prevents black spots and lithium plating at the negative electrode during formation, thus improving battery internal resistance and electrical performance.

[0095] Optionally, the value of w×β / α can be 19.14, 3.83, 0.64, 0.38, 0.19, 1.74, 0.96, 0.24, 0.83, 1.10, 1.65, 3.31, 0.02, 0.87, 1.74, 3.48, 8.70, 17.40, 19.14, or its value can be within the range obtained by combining any two of the above values.

[0096] This application starts with the structure of the lithium-ion battery itself, and by jointly controlling various structural parameters of the electrode components and the types and contents of electrolyte additives, it integrates the synergistic effect of various internal structural parameters and electrolyte parameters to develop and design a high-energy-density lithium-ion battery. At the same time, it solves the problems of severe gas generation and lithium plating on the negative electrode during the formation process of high-energy-density lithium-ion batteries, and significantly improves the internal resistance and electrical performance of lithium-ion batteries.

[0097] Electrolyte

[0098] The electrolyte acts as a conductor of ions between the positive and negative electrodes. The electrolyte described in this application contains fluorosulfonates and / or difluorophosphates.

[0099] In some embodiments, the fluorosulfonate may optionally have the structural formula (FSO3). y M y+ M y+ Selected from Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3+ Fe 2+ Fe 3+ Ni 2+ and Ni 3+ One of them.

[0100] In some embodiments, the difluorophosphate may optionally have the structural formula (F₂PO₂). y M y+ M y+ Selected from Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3+ Fe 2+ Fe 3+ Ni 2+ and Ni 3+ One of them.

[0101] In some embodiments, optionally, the mass percentage (w%) of the fluorosulfonate and / or difluorophosphate in the electrolyte ranges from 0.01% to 11%, optionally from 0.5% to 10%, and further optionally from 0.5% to 5%.

[0102] In the design process of the high-energy-density lithium-ion battery of this application, adding an appropriate amount (0.01% to 11%) of fluorosulfonates and / or difluorophosphates to the electrolyte can significantly reduce the amount of gas generated during formation. By ensuring that the amount of fluorosulfonates and / or difluorophosphates added is within a suitable range, black spots and lithium plating at the negative electrode can be avoided. On the other hand, it can also prevent the electrolyte viscosity from increasing and thus deteriorating the electrolyte conductivity, and to a certain extent, prevent the internal resistance of the battery from increasing due to the decrease in the migration rate of lithium ions in the electrolyte.

[0103] Optionally, the mass percentage (w%) of the fluorosulfonate and / or difluorophosphate in the electrolyte can be 0.5% to 10%.

[0104] Optionally, the mass percentage (w%) of the fluorosulfonate and / or difluorophosphate in the electrolyte can be 0.5% to 5%.

[0105] Specifically, when the mass percentage (w%) of fluorosulfonates and / or difluorophosphates in the electrolyte is in the range of 0.5% to 10%, there is no black spot phenomenon at the negative end, and the lithium-ion battery has significantly improved formation gas production, and the battery volumetric energy density and battery internal resistance are also at a better level.

[0106] Furthermore, when the mass percentage (w%) of fluorosulfonates and / or difluorophosphates in the electrolyte is in the range of 0.5% to 5%, the corresponding lithium-ion battery also exhibits excellent high and low temperature cycling performance.

[0107] Optionally, the value of w% can be 0.01%, 0.1%, 0.5%, 1%, 2%, 5%, 10%, 11%, or its value can be within the range obtained by combining any two of the above values.

[0108] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), ethylene acetate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0109] In some embodiments, the electrolyte containing fluorosulfonate and / or difluorophosphate may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, battery high-temperature performance, and battery low-temperature performance. Examples of such additives include fluoroethylene carbonate (FEC) and 1,3-propanesulfonyl lactone (PS).

[0110] Extensive experiments and research have shown that adding additional fluoroethylene carbonate (FEC) and / or 1,3-propanesulfonate lactone (PS) to an electrolyte containing fluorosulfonate and / or difluorophosphate can significantly improve the high and low temperature cycling performance of lithium-ion batteries while ensuring high energy density and low formation gas production.

[0111] In some embodiments, the electrolyte may optionally include a lithium salt, which may be selected from LiN(C) x F 2x+ 1SO2)(C y F 2y+1 One or more of the following: SO2), LiPF6, LiBF4, LiBOB, LiAsF6, Li(FSO2)2N, LiCF3SO3, and LiClO4, where x and y are natural numbers.

[0112] [Negative electrode plate]

[0113] The negative electrode sheet may include a negative current collector and a negative electrode material disposed on at least one surface of the negative current collector. The negative electrode material includes a negative electrode active material, and examples of negative electrode active materials include artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

[0114] In some embodiments, optionally, the loading M of the negative electrode material on the negative electrode current collector per unit area ranges from 11 mg / cm². 2 ~80mg / cm 2 11 mg / cm³ is an option. 2 ~50mg / cm 2 .

[0115] This application modifies the loading M of the negative electrode material on the negative electrode current collector per unit area in a manner known to those skilled in the art, for example by changing the number of coatings in the slurry coating process.

[0116] When the loading M of the negative electrode material on the negative electrode current collector per unit area is relatively small (M is less than 11 mg / cm²), 2 The volumetric energy density of lithium-ion batteries is negatively affected when the load increases from 50 mg / cm³. 2 Continuing to increase the load will not significantly improve the volumetric energy density of the battery. On the other hand, excessive load will also increase the contact area between the negative electrode material and the electrolyte, thereby aggravating the formation of gas and increasing the internal resistance of the battery.

[0117] In some embodiments, optionally, the specific surface area S of the negative electrode material on the negative electrode current collector per unit area ranges from 0.5 m². 2 / g~5m 2 / g.

[0118] This application modifies the specific surface area S in a manner known to those skilled in the art, for example, by adding different amounts of artificial graphite with different specific surface areas S to the slurry.

[0119] When the specific surface area S of the negative electrode material is within a suitable range, it can improve the reaction kinetics at the interface between the electrolyte and the negative electrode material, thereby reducing the internal resistance of the battery. On the other hand, it can reduce the amount of gas generated during formation and avoid black spots on the negative electrode.

[0120] Optionally, the value of S can be 0.1, 0.5, 1.1, 3, 5, 10, or its value can be within the range obtained by combining any two of the above values.

[0121] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0122] In some embodiments, the width L of the coating area of ​​the negative electrode material on the surface of the negative electrode current collector is in the range of 50mm≤L≤200mm, and can be optionally 50mm≤L≤100mm.

[0123] This application modifies the width L of the coating area of ​​the negative electrode material in a manner known to those skilled in the art, for example, by changing the slitting process.

[0124] When the width L of the coating area of ​​the negative electrode material is within a suitable range, on the one hand, it can avoid the diffusion path of the gas generated during formation becoming longer, thereby preventing the gas discharge rate from being affected, avoiding the occurrence of black spots and affecting the internal resistance of the battery; on the other hand, it can reduce the impact on the energy density of the lithium-ion battery.

[0125] Optionally, the value of L can be 200, 150, 100, 95, 50, or its value can be within the range obtained by combining any two of the above values.

[0126] In some embodiments, the porosity of the negative electrode material is optionally 10% to 40%.

[0127] Research shows that the higher the porosity of the negative electrode material, the more numerous and unobstructed the diffusion paths of the gas generated during formation from the interior of the negative electrode material to the interface between the negative electrode and the separator. However, when the porosity of the negative electrode material exceeds 50%, the volumetric energy density of the lithium-ion battery tends to decrease. When the porosity of the negative electrode material is below 10%, the resistance to lithium ion insertion / extraction is relatively large, thus increasing the internal resistance of the battery. By limiting the porosity of the negative electrode material to 10%–40%, the gas generated inside the negative electrode material can diffuse out rapidly, while simultaneously ensuring a high volumetric energy density and low internal resistance of the battery.

[0128] Optionally, the porosity of the negative electrode material can be 10%, 15%, 35%, or its value can be within the range obtained by combining any two of the above values.

[0129] In the lithium-ion battery of this application, the negative electrode current collector can be a metal foil or a composite current collector.

[0130] For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), 1,3-propanesulfonate lactone (PS), polyethylene (PE), etc.).

[0131] In the lithium-ion battery of this application, the negative electrode material typically comprises a negative electrode active material and optional binders, optional conductive agents, and other optional additives, and is usually formed by coating and drying a negative electrode slurry. The negative electrode slurry coating is typically formed by dispersing the negative electrode active material, optional conductive agents, and binders in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0132] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] As an example, the adhesive may be selected from one or more 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).

[0134] Other optional additives include thickeners such as sodium carboxymethyl cellulose (CMC-Na).

[0135] [Positive electrode plate]

[0136] The positive electrode includes a positive current collector and a positive electrode material disposed on at least one surface of the positive current collector.

[0137] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0138] In the lithium-ion battery of this application, the positive electrode current collector can be a metal foil or a composite current collector.

[0139] For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), 1,3-propanesulfonate lactone (PS), polyethylene (PE), etc.), but this application is not limited to these materials.

[0140] The cathode material includes a cathode active material, which is selected from materials capable of extracting and inserting lithium ions. Specifically, the cathode active material may be selected from one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and compounds obtained by adding other transition metals or non-transition metals to the above compounds, but this application is not limited to these materials.

[0141] The cathode material may optionally include a conductive agent. However, there is no specific limitation on the type of conductive agent, and those skilled in the art can select it according to actual needs. As an example, the conductive agent used in the cathode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0142] In this application, the positive electrode sheet can be prepared according to methods known in the art. As an example, the positive electrode material, conductive agent and binder of this application can be dispersed in a solvent (e.g., N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet is obtained.

[0143] [Isolation membrane]

[0144] Lithium-ion batteries using electrolytes, and some lithium-ion batteries using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, serving a separating function. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. In some embodiments, the separator material can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0145] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0146] In some embodiments, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0147] In some implementations, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of a lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0148] This application does not impose any particular limitation on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured lithium-ion battery 5.

[0149] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and a separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The lithium-ion battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0150] In addition, the lithium-ion battery, battery module, battery pack and device of this application will be described below with appropriate reference to the accompanying drawings.

[0151] [Battery Module]

[0152] In some implementations, lithium-ion batteries can be assembled into battery modules, and the number of lithium-ion batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0153] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple lithium-ion batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple lithium-ion batteries 5 can be fixed in place using fasteners.

[0154] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium-ion batteries 5 are housed.

[0155] [Battery Pack]

[0156] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0157] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0158] [Electrical appliances]

[0159] In addition, this application also provides an electrical device, which includes one or more of the lithium-ion battery, battery module, or battery pack provided in this application. The lithium-ion battery, battery module, or battery pack can be used as a power source for the device or as an energy storage unit for the device. The device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0160] As the electrical device, a lithium-ion battery, battery module, or battery pack can be selected according to its usage requirements.

[0161] Figure 6This is an example device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density lithium-ion batteries, a battery pack or battery module can be used.

[0162] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium-ion batteries as their power source.

[0163] Example

[0164] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially. Unless otherwise specified, the content of each component in the embodiments of this application is by mass.

[0165] Example 1

[0166] [Preparation of Lithium-ion Batteries]

[0167] 1) Preparation of positive electrode sheet

[0168] LiNi, the positive electrode active material 0.8 Mn 0.1 Co 0.1 O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 94:3:3. After thorough mixing, a positive electrode slurry is obtained. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode sheet.

[0169] 2) Preparation of negative electrode sheet

[0170] Artificial graphite (active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were dissolved in deionized water at a weight ratio of 95:2:2:1 and mixed thoroughly to prepare a negative electrode slurry. The negative electrode slurry was then uniformly coated onto a copper foil current collector (negative electrode current collector) one or more times. After drying, cold pressing, and slitting, a negative electrode material with a specific surface area S of 0.1 m² was obtained. 2 / g, the loading M of the negative electrode material is 11mg / cm³ 2 A negative electrode sheet with a coating area L of 95mm.

[0171] 3) Preparation of electrolyte

[0172] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvent EC / EMC was mixed evenly at a volume ratio of 3 / 7. 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent. Then, lithium fluorosulfonate, accounting for 1% of the total mass of the electrolyte, was added and stirred evenly to obtain the electrolyte of Example 1.

[0173] 4) Separating membrane

[0174] Polypropylene film is used as the separator.

[0175] 5) Preparation of lithium-ion batteries

[0176] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting bare cell is then wound, tabs are welded onto it, and the cell is placed in an aluminum casing. It is then baked at 80°C to remove moisture, followed by the injection of electrolyte and sealing to obtain a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product of Example 1.

[0177] Examples 2-24, Examples 27-37

[0178] For Examples 2-24 and Examples 27-37, the specific surface area S of the negative electrode material, the loading M of the negative electrode material on the negative electrode current collector, the width L of the coating area of ​​the negative electrode material, and the content w% of fluorosulfonate / difluorophosphate in the electrolyte are shown in Table 1. Other process conditions are the same as in Example 1. Finally, lithium-ion battery products of Examples 2-24 and Examples 27-37 were obtained respectively.

[0179] Example 25

[0180] Except for the addition of 1% fluoroethylene carbonate (FEC) by mass of the electrolyte to the electrolyte, the other parameters and processes are the same as in Example 20, and the lithium-ion battery product of Example 25 is obtained.

[0181] Example 26

[0182] Except for the addition of 1,3-propanesulfonate (PS) at 1% of the electrolyte mass, the other parameters and processes were the same as in Example 20, and the lithium-ion battery product of Example 26 was obtained.

[0183] Comparative Examples 1-7

[0184] For Comparative Examples 1-7, the specific surface area S of the corresponding negative electrode material, the loading M of the negative electrode material on the negative electrode current collector, the width L of the coating area of ​​the negative electrode material, and the content w% of fluorosulfonate / difluorophosphate in the electrolyte are shown in Table 1. Other process conditions are the same as in Example 1. Finally, lithium-ion battery products of Comparative Examples 1-7 were obtained.

[0185] [Testing of relevant parameters for negative electrode plates]

[0186] 1) Testing of the specific surface area S of the negative electrode material

[0187] The negative electrode material on all the negative electrode sheets of the embodiments and comparative examples was scraped off with a blade, and then tested according to standard GB / T 21650.2-2008. Specific values ​​are shown in Table 1.

[0188] 2) Testing the width L of the coating area of ​​the negative electrode material

[0189] The length L of the negative electrode material coating area on the negative electrode sheet of all embodiments and comparative examples was measured using vernier calipers. Specific values ​​are shown in Table 1.

[0190] 3) Testing the porosity of the negative electrode sheet

[0191] The negative electrode sheet is punched into small circular pieces with a diameter of 10 cm. The thickness is measured using a micrometer, and the apparent volume V1 is calculated. Then, referring to standard GB / T 24586-2009, the true volume V2 is measured using the gas displacement method. The porosity is then calculated as (V1-V2) / V1×100%. Specific values ​​are shown in Table 4.

[0192] [Battery Performance Test]

[0193] 1) After formation and full charging, lithium plating with black spots at the negative electrode interface

[0194] After formation, all batteries from the examples and comparative examples were first placed at 45°C for 120 minutes, then evacuated to -80 kPa, followed by constant current charging at 0.02C to 3.4V; after standing for 5 minutes, they were charged again at 0.1C to 3.75V, and the negative pressure was removed to restore normal pressure. Finally, they were charged at 0.5C to 4.2V, reaching full charge. The fully charged batteries were then disassembled to observe whether there were black spots or lithium plating at the negative electrode interface.

[0195] 2) Volumetric energy density test

[0196] At 25°C, a lithium-ion battery is charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current is less than 0.05C, and then discharged at 0.33C to 2.8V, yielding the discharge energy Q. The battery's length, width, and height are measured using calipers, and the volume V is calculated. Therefore, the volumetric energy density = Q / V.

[0197] 3) Cell internal resistance test

[0198] At 25°C, the lithium-ion battery was charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current was less than 0.05C, and then discharged at 0.5C for 60 minutes, thus adjusting the cell's charge to 50% SOC. Then, an AC internal resistance tester was connected to the positive and negative terminals of the cell to test the battery's internal resistance, with a perturbation of 5mV and a frequency of 1000 Hz.

[0199] 4) Lithium-ion battery cycle performance test at 25°C

[0200] At 25°C, the lithium-ion battery is charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current is less than 0.05C, and then discharged at a constant current of 1C to 2.8V. This constitutes one charge-discharge cycle. This charging and discharging process is repeated, and the capacity retention rate of the lithium-ion battery after 1000 cycles is calculated.

[0201] The capacity retention rate (%) of a lithium-ion battery after 1000 cycles at 25°C = (discharge capacity of the 1000th cycle / discharge capacity of the first cycle) × 100%.

[0202] 5) Lithium-ion battery 45℃ cycle performance test

[0203] At 45°C, the lithium-ion battery is charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current is less than 0.05C, and then discharged at a constant current of 1C to 2.8V. This constitutes one charge-discharge cycle. This charging and discharging process is repeated, and the capacity retention rate of the lithium-ion battery after 800 cycles is calculated.

[0204] The capacity retention rate (%) of a lithium-ion battery after 1000 cycles at 25°C = (discharge capacity of the 800th cycle / discharge capacity of the first cycle) × 100%.

[0205] The relevant parameters and battery performance test parameters of the lithium-ion batteries of all the above embodiments and comparative examples are listed in Tables 1 to 4.

[0206] Table 1: Relevant parameters of lithium-ion batteries in the examples and comparative examples

[0207]

[0208]

[0209] Table 2: Relevant parameters and performance test results of lithium-ion batteries in the examples and comparative examples

[0210]

[0211]

[0212]

[0213] Table 3: Relevant parameters and performance test results of lithium-ion batteries in the examples and comparative examples

[0214]

[0215]

[0216] Table 4: Relevant parameters and performance test results of lithium-ion batteries in the examples and comparative examples

[0217]

[0218] The impact of various design parameters on the energy density, formation gas production, and internal resistance of lithium-ion batteries

[0219] According to Tables 1 and 2, for the lithium-ion batteries of Examples 1 to 37, under the synergistic effect of various design parameters, the designed and developed lithium-ion batteries satisfy the relationship 0.01≤w×β / α≤20. Correspondingly, lithium-ion batteries possess the following advantages: maintaining high energy density (the volumetric energy density of the lithium-ion batteries of Examples 1 to 37 is all above 550Wh / L). -1 The above results show that the formation gas generation problem has been significantly improved (no large number of black spots and lithium plating were observed in the lithium-ion batteries of Examples 1 to 37), and the internal resistance of the lithium-ion batteries is lower (the internal resistance of the lithium-ion batteries of Examples 1 to 37 is all below 0.46mΩ, and most are between 0.30 and 0.37mΩ).

[0220] However, compared to Examples 1-37, the various design parameters of the lithium-ion batteries in Comparative Examples 1-7 do not satisfy the relationship 0.01≤w×β / α≤20, thus the lithium-ion batteries in Comparative Examples 1-7 have poor performance. Specifically, Comparative Example 1 has a very low volumetric energy density (only 510Wh / L). -1 The presence of numerous black spots indicates a large amount of gas production during formation, suggesting that the formation gas production problem in lithium-ion batteries has not been improved. Comparative Example 2, despite having a moderate volumetric energy density, exhibited numerous black spots and lithium plating, indicating that the formation gas production problem in lithium-ion batteries has not been improved. Comparative Example 3, while not showing black spots, had a very low volumetric energy density (only 530 Wh / L). -1 Comparative Example 4's lithium-ion battery exhibited numerous black spots and a high internal resistance (0.553 mΩ). Comparative Example 5's lithium-ion battery, while not exhibiting black spots, still had a high internal resistance (0.658 mΩ). Comparative Examples 6 and 7, while also not exhibiting black spots, had very low volumetric energy densities (only 500 Wh / L each).-1 and 350WhL -1 ).

[0221] The impact of fluorosulfonate and / or difluorophosphate content (w%) on lithium-ion batteries.

[0222] As can be seen from Tables 1, 2, and 3, in Examples 17-24, when w% was in the range of 0.01% to 11%, no large number of black spots appeared, and the battery energy density and internal resistance remained at a relatively good level. However, compared to Examples 17-24, the lithium-ion battery in Comparative Example 2, due to the absence of fluorosulfonates and / or difluorophosphates, exhibited a large number of black spots and lithium plating, indicating severe gas generation during battery formation. In Comparative Example 5, when the w% value was relatively high (15%), although it had little effect on the battery energy density, the battery internal resistance was relatively high.

[0223] As shown in Table 3, in Examples 19-23, when w% is in the range of 0.5% to 10%, the lithium-ion batteries exhibit high energy density, no black spots, significantly improved formation gas production, and low internal resistance. Furthermore, in Examples 19-22, when w% is in the range of 0.5% to 5%, the corresponding lithium-ion batteries also possess excellent high-temperature and low-temperature cycling performance.

[0224] The effect of the loading M of negative electrode material on the negative electrode current collector per unit area on lithium-ion batteries.

[0225] Based on Tables 1 and 2, and through a comprehensive comparison of Examples 6-11, for Examples 7-10, M is at 11 mg / cm³. 2 ~80mg / cm 2 Within this range, the battery energy density is at a relatively high level (570–579 Wh / L), and the internal resistance of the battery is also below 0.4 mΩ. However, for Example 6, the amount of M is relatively low (5 mg / cm³). 2 Lithium-ion batteries have a relatively low energy density (550Wh / L). -1 For Example 11, the amount of M was relatively high (100 mg / cm³). 2 Lithium-ion batteries have a relatively low energy density (550Wh / L). -1 The internal resistance of lithium-ion batteries is also correspondingly high (0.411 mΩ). Furthermore, when the value of M is 11 mg / cm²... 2 ~50mg / cm 2 Within the specified range, lithium-ion batteries exhibit no black spot phenomenon, significantly improving the formation gas generation problem, while maintaining a high level of battery energy density and low battery internal resistance.

[0226] The Influence of Specific Surface Area S of Anode Materials on Lithium-ion Batteries

[0227] Based on Tables 1 and 2, and through a comprehensive comparison of Examples 1-5 and Examples 2-4, the S value at 0.5m... 2 / g~5m 2 Within the range of / g, the lithium-ion battery exhibits high energy density, no black spots appear at the negative electrode, and the formation gas generation problem is significantly improved. However, for Example 1, the value of S is relatively small (0.1m). 2 / g), resulting in a large internal resistance of the battery; for Example 5, the value of S (10m) 2 The larger / g) increases the contact area between the negative electrode material and the electrolyte, resulting in black spots appearing on the negative electrode.

[0228] The effect of the coating width L of the negative electrode material on lithium ions.

[0229] Based on Tables 1 and 2, by comprehensively comparing Examples 12-16 and Comparative Example 6, compared to Comparative Example 6, the L value in Examples 12-16 is within the range of 50mm ≤ L ≤ 200mm. In this case, the lithium-ion battery exhibits a higher energy density and lower internal resistance. For Examples 14-16, L is within the range of 50mm ≤ L ≤ 100mm. In this case, the lithium-ion battery not only has a higher energy density and lower internal resistance, but also exhibits no black spots at the negative electrode, significantly improving the formation gas generation problem.

[0230] The Influence of Fluorinated Ethylene Carbonate and 1,3-Propane Sulfonate Additives on the Cycle Performance of Lithium-ion Batteries

[0231] According to Table 3, by comparing Examples 25, 26, and 20, the addition of fluoroethylene carbonate or 1,3-propanesulfonate additives to electrolytes containing fluorosulfonates and / or difluorophosphates can effectively improve the high and low temperature cycle performance of lithium-ion batteries.

[0232] The impact of anode material porosity on lithium-ion batteries

[0233] According to Table 4, through a comprehensive comparison of Examples 33-37, the porosity of Examples 33, 35, and 36 is in the range of 10% to 40%, therefore, the corresponding lithium-ion batteries have higher internal resistance (below 0.41 mΩ) and higher volumetric energy density (~570 Wh / L). -1 The porosity of the negative electrode material in Example 34 was low, resulting in a higher internal resistance of the battery. In Example 37, the porosity of the negative electrode material was high, resulting in a lower volumetric energy density of the lithium-ion battery.

[0234] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely illustrative, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium-ion battery, characterized in that, include: An electrode assembly, comprising a negative electrode current collector and a negative electrode material disposed on at least one surface of the negative electrode current collector, the negative electrode material having a porosity of 25%-50%; and The electrolyte contains fluorosulfonates and / or difluorophosphates. Let the formation gas production area coefficient of the lithium-ion battery be α, α=M×S / 200 Equation (I). In equation (I), M is the loading of negative electrode material on the negative electrode current collector per unit area, and its unit is mg / cm². 2 The range of M is 11 mg / cm³. 2 ~50mg / cm 2 , In the above formula (I), S is the specific surface area of ​​the negative electrode material on the negative electrode current collector, and its unit is m². 2 / g, where the range of S is 0.5m 2 / g~5m 2 / g, Let the exhaust path coefficient of the lithium-ion battery be β, β = 100 / L Equation (II). In equation (II), L is the width of the negative electrode current collector, and its unit is mm. The range of L is 50 mm ≤ L ≤ 100 mm. Wherein, the mass percentage w% of the fluorosulfonate and / or difluorophosphate substances in the electrolyte, the formation gas production area coefficient α of the lithium-ion battery and the exhaust coefficient β of the lithium-ion battery satisfy 0.64≤w×β / α≤0.87 Equation (III), or 1.65≤w×β / α≤1.74, or 3.31≤w×β / α≤3.83, or 17.4≤w×β / α≤19.14; The mass percentage (w%) of the fluorosulfonate and / or difluorophosphate substances in the electrolyte ranges from 0.5% to 5%.

2. The lithium-ion battery according to claim 1, characterized in that, The structural formula of the fluorosulfonate is (FSO3). y M y+ M y+ Selected from Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3+ Fe 2+ Fe 3+ Ni 2+ and Ni 3+ One of them.

3. The lithium-ion battery according to claim 1, characterized in that, The structural formula of the difluorophosphate is (F₂PO₂). y M y+ M y+ Selected from Li + Na + K + 、Rb + Cs + Mg 2+ Ca 2+ Ba 2+ Al 3 + Fe 2+ Fe 3+ Ni 2+ and Ni 3+ One of them.

4. The lithium-ion battery according to any one of claims 1 to 3, characterized in that, The electrolyte contains fluoroethylene carbonate and / or 1,3-propanesulfonate lactone.

5. The lithium-ion battery according to any one of claims 1 to 3, characterized in that, The porosity of the negative electrode material is 25%~40%.

6. A battery module, characterized in that, The lithium-ion battery includes any one of claims 1 to 5.

7. A battery pack, characterized in that, Includes the lithium-ion battery according to any one of claims 1 to 5 or the battery module according to claim 6.

8. An electrical device, characterized in that, It includes at least one of the lithium-ion battery according to any one of claims 1 to 5, the battery module according to claim 6, or the battery pack according to claim 7.

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