A lithium-ion battery and an electrical device comprising the same.

Abstract

This application relates to a lithium-ion battery and an electrical device comprising the same, wherein the positive electrode of the lithium-ion battery comprises a positive electrode active material Li. n Ni x Co y M z O f A g The positive electrode active material has the following properties: 0.8 ≤ n ≤ 1.2, 0.5 ≤ x ≤ 0.98, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.5, 0 ≤ f ≤ 2; element M is selected from at least one of Mn, Al, Zr, Ti, V, Mg, Fe, B, and Mo; element A is selected from at least one of S, N, P, F, Cl, Br, and I; the specific surface area of ​​the positive electrode active material is 0.2–1.8 m². 2 / g; the electrolyte contains additives, including fluorosulfonate; the fluorosulfonate accounts for 0.005% to 0.1% of the mass percentage of the electrolyte. This lithium-ion battery uses a high-nickel positive electrode active material with high energy density, and also has the characteristics of good stability, low gas generation, and excellent power performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to a lithium-ion battery and an electrical device containing the same. Background Technology

[0002] Secondary batteries, represented by lithium-ion batteries, have been widely used. To further meet the ever-evolving application demands, lithium-ion batteries are required to have high energy density and better power performance.

[0003] Currently, there are two main approaches to improving the energy density of lithium-ion batteries: one is to use cathode materials with high nickel content; the other is to increase the operating voltage of lithium-ion batteries. However, both approaches have certain adverse effects on battery performance, such as reduced stability and increased susceptibility to gas generation. Summary of the Invention

[0004] The purpose of this application is to provide a lithium-ion battery and an electrical device containing the same, wherein the lithium-ion battery uses a high-nickel positive electrode active material with high energy density, and also has the characteristics of good stability, low gas production, and excellent power performance.

[0005] Therefore, the first aspect of this application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte;

[0006] The positive electrode includes a positive electrode active material, wherein the positive electrode active material is Li. n Ni x Co y M z O f A g Wherein 0.8≤n≤1.2, 0.5≤x≤0.98, 0≤y≤0.5, 0≤z≤0.5, 0≤f≤2, element M is selected from at least one of Mn, Al, Zr, Ti, V, Mg, Fe, B, and Mo, and element A is selected from at least one of S, N, P, F, Cl, Br, and I; the specific surface area of ​​the positive electrode active material is 0.2~1.8m². 2 / g;

[0007] The electrolyte contains additives, including fluorosulfonates; the fluorosulfonates account for 0.005% to 0.1% of the mass of the electrolyte.

[0008] By combining a positive electrode active material with the aforementioned specific surface area with a certain concentration of fluorosulfonate, not only can a high energy density be achieved, but the gas generation problem of the battery can also be significantly reduced, maintaining good power performance. The main principle is that a positive electrode active material with a high specific surface area can better leverage the advantages of high energy density and good power performance, but it is also more prone to gas generation problems. This application, by using a positive electrode active material with a high specific surface area and combining it with a certain concentration of fluorosulfonate as an electrolyte additive, can form LiF and LixSO4 on the positive electrode surface. y Solid electrolyte membranes (CEIs) with inorganic materials as the main component are relatively stable under high temperature and high pressure conditions and have low impedance. They can prevent the solvent from directly contacting the positive electrode surface and causing oxidation, thereby significantly reducing gas production and helping to maintain good power performance.

[0009] In any embodiment, the specific surface area of ​​the positive electrode active material is 0.4–1.3 m². 2 / g.

[0010] By using the above-mentioned positive electrode active material with a specific surface area, it is beneficial to further improve the gas generation and power of the battery.

[0011] In any embodiment, the fluorosulfonate accounts for 0.01% to 0.06% of the mass percentage of the electrolyte.

[0012] By ensuring that the proportion of fluorosulfonate is within the above range, the reaction can occur more effectively on the positive electrode surface, producing a suitable CEI film, which is beneficial for further improving the gas production and power of the battery.

[0013] In any embodiment, the negative electrode comprises a negative electrode active material, the specific surface area of ​​which is 0.7–2.5 m². 2 / g.

[0014] The specific surface area of ​​the negative electrode active material also has a certain impact on the battery power performance. Generally speaking, the larger the specific surface area, the more likely it is to increase the battery power due to the increased electrolyte contact area, and the easier it is to generate gas. Based on improving the specific surface area of ​​the positive electrode active material and the electrolyte composition, this application optimizes the specific surface area of ​​the negative electrode active material to the above-mentioned range, which can balance low gas generation and high power performance of the negative electrode, which is conducive to further improvement of battery performance.

[0015] In any embodiment, the specific surface area of ​​the positive electrode active material is bm. 2 / g, the specific surface area of ​​the negative electrode active material is cm² 2 / g; the ratio of b to c is 0.14 to 1.81.

[0016] Gas generation in lithium-ion batteries is mainly caused by the oxidation or reduction of solvents in the electrolyte. Some solvents are reduced to form SEI on the negative electrode side, resulting in low gas generation. Other solvents are oxidized on the positive electrode side with almost no CEI formation, resulting in high gas generation. The b / c ratio reflects the gas generation on both the positive and negative electrode sides. When the b / c ratio is within the aforementioned range, the improvement effect of fluorosulfonate in the electrolyte additive on battery gas generation performance can be further enhanced.

[0017] In any embodiment, the ratio of b to c is 0.40 to 1.14.

[0018] When the ratio of b to c is within the above range, it is more conducive to improving the battery's gas production performance and high power performance.

[0019] In any embodiment, the fluorosulfonate accounts for a wt% of the electrolyte, and the specific surface area of ​​the positive electrode active material is bm. 2 / g, the specific surface area of ​​the negative electrode active material is cm² 2 / g; The relationship between a, b, and c satisfies 1.75≤100a / (b / c)≤17.5.

[0020] Gas generation in lithium-ion batteries is mainly caused by the oxidation or reduction of solvent in the electrolyte. Some solvent is reduced to form SEI on the negative electrode side, resulting in low gas generation. Other solvent is oxidized on the positive electrode side with almost no CEI formation, leading to high gas generation. The b / c ratio reflects the gas generation on both the positive and negative electrode sides. A larger b / c ratio indicates a larger specific surface area of ​​the positive electrode active material in the cell system, resulting in stronger positive electrode activity and greater gas generation from electrolyte oxidation on the positive electrode side. In this case, a larger amount of 'a' is needed to improve gas generation on the positive electrode side. Conversely, a smaller b / c ratio requires a relatively smaller amount of 'a'. Therefore, using the ratio of 'a' to (b / c) to reflect the relationship between fluorosulfonate concentration and the specific surface area of ​​the positive and negative electrode active materials is reasonable. When the relationship between 'a', 'b', and 'c' satisfies the above formula, it is beneficial to improve gas generation during battery use and storage.

[0021] In any embodiment, the fluorosulfonate includes at least one of lithium fluorosulfonate, sodium fluorosulfonate, and potassium fluorosulfonate.

[0022] The aforementioned fluorosulfonates are more suitable for the electrolyte system of the lithium-ion battery in this application, and are more beneficial to improving battery performance compared to other fluorosulfonates.

[0023] In any embodiment, the additive further includes difluorophosphate; the difluorophosphate accounts for 0.001% to 0.1% of the mass percentage of the electrolyte.

[0024] Difluorophosphate can form MF and M on the surface of the negative electrode active material. x PO y The primary component is a low-resistivity inorganic solid electrolyte layer (SEI). Furthermore, when the above-mentioned mass percentages are adopted, it is beneficial to improve the power performance of lithium-ion batteries without worsening cell gas generation.

[0025] In any embodiment, the difluorophosphate accounts for 0.001% to 0.08% of the mass percentage of the electrolyte.

[0026] When the proportion of the additive difluorophosphate in the electrolyte is within the above range, it is beneficial to further improve the power performance of the battery.

[0027] A second aspect of this application provides an electrical device comprising the lithium-ion secondary battery described in the first aspect of this application.

[0028] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more obvious and understandable, the specific implementation methods of this application are listed below. Attached Figure Description

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. In the drawings:

[0030] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0031] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0032] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0033] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0034] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0035] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application;

[0036] Explanation of reference numerals in the attached figures:

[0037] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Lithium-ion battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0038] Exemplary embodiments of this disclosure will now be described in more detail. It should be understood that this disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0039] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0042] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0044] Rechargeable batteries, represented by lithium-ion batteries, have been widely used. To further meet the evolving application demands, lithium-ion batteries require high energy density and better power performance. Currently, there are two main approaches to improving the energy density of lithium-ion batteries: one is to use cathode materials with high nickel content; the other is to increase the operating voltage of the lithium-ion battery. However, both approaches have certain adverse effects on battery performance, such as reduced stability and increased susceptibility to gas generation.

[0045] Analysis revealed that the main reasons for the adverse effects include: excessive nickel content reduces the stability of the positive electrode material, and the unstable trivalent nickel ions easily cause oxidative decomposition of the electrolyte at the positive electrode; on the other hand, increasing the battery charging voltage raises the positive electrode potential, which also makes the electrolyte more prone to oxidative decomposition. These two situations can lead to a series of problems such as battery gas generation and increased interfacial impedance, thus deteriorating power performance. Furthermore, the solid electrolyte interphase (SEI) film formed on the negative electrode surface by electrolyte reduction also partially decomposes, generating gas.

[0046] Therefore, this application mainly improves the specific surface area of ​​the positive electrode active material and the electrolyte composition simultaneously to reduce battery gas production and improve battery stability and power performance.

[0047] The solutions described in the embodiments of this application are applicable to lithium-ion secondary batteries, battery modules using the secondary battery, battery packs using the secondary battery or battery module, and electrical devices using at least one of secondary batteries, battery modules, and battery packs.

[0048] Lithium-ion secondary batteries

[0049] In some embodiments, a lithium-ion secondary battery is provided, which includes a positive electrode, a negative electrode, a separator, and an electrolyte;

[0050] The positive electrode includes a positive electrode active material, wherein the positive electrode active material is Li. n Ni x Co y M z O f A g Wherein 0.8≤n≤1.2, 0.5≤x≤0.98, 0≤y≤0.5, 0≤z≤0.5, 0≤f≤2, element M is selected from at least one of Mn, Al, Zr, Ti, V, Mg, Fe, B, and Mo, and element A is selected from at least one of S, N, P, F, Cl, Br, and I; the specific surface area of ​​the positive electrode active material is 0.2~1.8m². 2 / g;

[0051] The electrolyte contains additives, including fluorosulfonates; the fluorosulfonates account for 0.005% to 0.1% of the mass of the electrolyte.

[0052] When using a specific surface area within the aforementioned range, high-nickel cathode active materials can better leverage their advantages of high energy density and good power performance. However, due to their higher activity, they are also more prone to gas generation. Therefore, this application, when using a high-nickel cathode active material with the aforementioned specific surface area, also incorporates an electrolyte containing a certain concentration of fluorosulfonate. By using fluorosulfonate in the electrolyte, LiF and LixSO₄ can be formed on the cathode surface. y Solid electrolyte membranes (CEIs) with fluorosulfonate as the main component are relatively stable under high temperature and high pressure conditions and have low impedance. They can prevent the solvent from directly contacting the positive electrode surface and causing oxidation, thereby significantly reducing gas production. Furthermore, controlling the fluorosulfonate content in the electrolyte to 0.005%–0.1 wt% is more conducive to sufficient film formation, significantly suppressing gas production, and maintaining battery power.

[0053] In this article, specific surface area, also known as BET (Brunauer, Emmett, and Teller) specific surface area, refers to the total area per unit mass of material, usually measured in m². 2 / g. Specific surface area can be determined by the following method: nitrogen adsorption method for specific surface area determination, using a Microt TriStar II 3020 / 3030 instrument (USA), and the testing standard can refer to GB / T19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method". The specific surface area of ​​the positive electrode active material can be controlled by the following processes: the specific surface area of ​​the positive electrode active material is related to the particle size distribution and single crystal size of the material. The particle size distribution can be obtained by adjusting the following parameters: controlling the particle size distribution of the precursor and the process parameters of the pulverization and classification of the ternary material. The single crystal size can be obtained by adjusting the following parameters: precursor size / specific surface area, sintering temperature, and process parameters of the pulverization and classification of the finished product. The high-nickel ternary materials with different BET specific surface areas involved in the embodiments of this application can all be obtained through commercial channels.

[0054] [Positive electrode plate]

[0055] The positive electrode includes a positive current collector and a positive active material disposed on at least one surface of the positive current collector. As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and a layer of positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0056] In some embodiments, the specific surface area of ​​the positive electrode active material is 0.4–1.3 m². 2 / g; for example, it can be about 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g etc.

[0057] By using the above-mentioned positive electrode active material with a specific surface area, it is beneficial to further improve the gas generation and power of the battery.

[0058] In some embodiments, the positive electrode active material may be selected from any lithium transition metal oxide known in the art for use in lithium-ion batteries that conforms to the following formula.

[0059] Li n Ni x Co y M z O f A gWhere 0.8≤n≤1.2, 0.5≤x≤0.98, 0≤y≤0.5, 0≤z≤0.5,

[0060] 0 ≤ f ≤ 2, element M is selected from at least one of Mn, Al, Zr, Ti, V, Mg, Fe, B, and Mo, and element A is selected from at least one of S, N, P, F, Cl, Br, and I. For example, lithium nickel cobalt manganese oxide (such as LiNi) can be used. 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.7 Co 0.2 Mn 0.1 O2 (also known as NCM) 721 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. These positive electrode active materials may be used alone or in combination of two or more.

[0061] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0062] In some embodiments, the positive electrode material may optionally include a binder. For example, the binder may include one or more combinations selected from the group consisting of: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0063] In some embodiments, the cathode material may optionally include a conductive agent. For example, the conductive agent may include one or more combinations selected from the group consisting of: Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0064] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned positive electrode material, such as positive electrode active material, conductive agent, binder and any other components in a solvent (e.g. N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0065] Electrolyte

[0066] The electrolyte acts as a conductor of ions between the positive and negative electrodes. The electrolyte comprises a solvent, an electrolyte salt, and additives, and contains 0.005% to 0.1% by mass of a fluorosulfonate.

[0067] In some embodiments, the fluorosulfonate accounts for 0.01% to 0.06% of the electrolyte by mass percentage (wt%); for example, it can be about 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, etc.

[0068] By ensuring that the proportion of fluorosulfonate is within the above range, it is beneficial to further improve the gas production and power of the battery.

[0069] In some embodiments, the fluorosulfonate includes one or more of lithium fluorosulfonate, sodium fluorosulfonate, and potassium fluorosulfonate.

[0070] The aforementioned fluorosulfonates exhibit good compatibility with battery systems and readily form LiF and LixSO4 on the cathode surface. y These substances form a highly stable solid electrolyte membrane (CEI), effectively reducing gas production.

[0071] In some embodiments, the additive further includes difluorophosphate; the difluorophosphate accounts for 0.001% to 0.1% of the electrolyte by mass percentage (wt%); for example, it can be about 0.001%, 0.002%, 0.005%, 0.007%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc. As an example, the difluorophosphate can be one or a combination of two or more of lithium difluorophosphate, sodium difluorophosphate, and potassium difluorophosphate.

[0072] Difluorophosphate can form MF and M on the surface of the negative electrode active material. x PO y A low-resistivity inorganic solid electrolyte layer (SEI) is beneficial for improving the power performance of lithium-ion batteries without worsening cell gas generation. Furthermore, if the amount added is too small (e.g., less than 0.01%), insufficient film formation on the negative electrode surface will result in minimal power improvement; conversely, if the amount added is too large (e.g., greater than 0.1%), it will lead to higher electrolyte viscosity, thus deteriorating power performance.

[0073] In some embodiments, the difluorophosphate constitutes 0.001% to 0.08% of the electrolyte by mass percentage (wt%).

[0074] When the proportion of the additive difluorophosphate in the electrolyte is within the above range, it is beneficial to further improve the power performance of the battery.

[0075] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0076] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0077] [Negative electrode plate]

[0078] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. As an example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative active material layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0079] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.7–2.5 m². 2 / g; for example, it can be about 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g、2m 2 / g、2.1m 2 / g, 2.2m 2 / g, 2.3m 2 / g, 2.4m 2 / g, 2.5m 2 / g etc.

[0080] The specific surface area of ​​the negative electrode active material also has a certain impact on the battery power performance. Generally speaking, the larger the specific surface area, the more likely it is to increase the battery power due to the increased electrolyte contact area, and the easier it is to generate gas. In the technical solution provided in this application, based on improving the specific surface area of ​​the positive electrode active material and the electrolyte composition, the specific surface area of ​​the negative electrode active material is optimized to the above-mentioned range, which can balance the low gas generation and high power performance of the negative electrode, which is conducive to further improvement of battery performance.

[0081] In some embodiments, the specific surface area of ​​the positive electrode active material is bm. 2 / g, the specific surface area of ​​the negative electrode active material is cm² 2 / g; the ratio of b to c is 0.14 to 1.81.

[0082] Gas generation in lithium-ion batteries is mainly caused by the oxidation or reduction of solvents in the electrolyte. Some solvents are reduced to form SEI on the negative electrode side, resulting in low gas generation. Other solvents are oxidized on the positive electrode side with almost no CEI formation, resulting in high gas generation. The b / c ratio reflects the gas generation on both the positive and negative electrode sides. When the b / c ratio is within the aforementioned range, the improvement effect of fluorosulfonate in the electrolyte additive on battery gas generation performance can be further enhanced.

[0083] In some implementations, the ratio of b to c is 0.40 to 1.14.

[0084] When the ratio of b to c is within the above range, it is more conducive to improving the battery's gas production performance and high power performance.

[0085] In some embodiments, the fluorosulfonate accounts for a wt% of the electrolyte, and the specific surface area of ​​the positive electrode active material is bm. 2 / g, the specific surface area of ​​the negative electrode active material is cm² 2 / g; The relationship between a, b, and c satisfies 1.75≤100a / (b / c)≤17.5.

[0086] During the charging, discharging, and storage of lithium-ion batteries, gas generation is mainly caused by the oxidation or reduction of solvents in the electrolyte. Some solvents are reduced to form SEI on the negative electrode side, resulting in low gas generation; others are oxidized on the positive electrode side with almost no CEI formation, leading to high gas generation. The b / c ratio reflects the gas generation on both the positive and negative electrode sides. A larger b / c ratio indicates a larger specific surface area of ​​the positive electrode active material in the cell system, resulting in stronger positive electrode activity and greater gas generation from electrolyte oxidation on the positive electrode side. In this case, a larger amount of a is needed to improve gas generation on the positive electrode side. Conversely, a smaller b / c ratio requires a relatively smaller amount of a. Therefore, using the ratio of a to (b / c) to reflect the relationship between fluorosulfonate concentration and the specific surface area of ​​the positive and negative electrode active materials is reasonable. When the relationship between a, b, and c satisfies the above formula, it is beneficial to improve the gas generation problem during battery use and storage.

[0087] In some implementations, the relationship between a, b, and c satisfies 1.75 ≤ 100a / (b / c) ≤ 17.5; for example, the value of 100a / (b / c) can be approximately 1.75, 2.5, 3, 3.25, 3.5, 3.89, 4, 4.38, 4.75, 5, 5.38, 5.75, 6, 6.36, 6.75, 7, 7.5, 8, 8.25, 8.75, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.63, 16, 16.5, 17, 17.5, etc.

[0088] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0089] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which may be a negative electrode active material known in the art for use in batteries. For example, the negative electrode active material includes one or more combinations selected from the group consisting of: natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, TiO2-Li4Ti5O 12 Li-Al alloys are used. However, this application is not limited to these materials; other conventional materials that can be used as negative electrode active materials for lithium-ion batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0090] In some embodiments, the negative electrode active material layer may optionally include a binder. For example, the binder may include one or more combinations selected from the group consisting 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).

[0091] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. For example, the conductive agent may include one or more combinations selected from the group consisting of: Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0092] In some embodiments, the negative electrode active material layer may also optionally include other additives. For example, other additives may be thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0093] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode active material layer, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0094] [Septum]

[0095] The separator is positioned between the positive and negative electrode plates to provide isolation. This application does not impose any particular restriction on the type of separator; any known porous separator with good chemical and mechanical stability can be selected. The separator material can be selected from one or more combinations of the following: 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 restriction. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular restriction.

[0096] [Battery manufacturing]

[0097] A lithium-ion battery can be prepared by winding or stacking positive electrode sheets, negative electrode sheets, and separators to form an electrode assembly, which is then packaged and injected with electrolyte.

[0098] The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0099] 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.

[0100] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. 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.

[0101] Battery modules, battery packs

[0102] 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.

[0103] Figure 3This 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.

[0104] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium-ion batteries 5 are housed.

[0105] In some implementations, lithium-ion batteries can also be assembled into battery packs.

[0106] In some embodiments, the battery module 4 can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0107] 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.

[0108] Electrical appliances

[0109] This application also provides an electrical device, which includes the lithium-ion battery provided in this application. In some embodiments, the electrical device includes at least one of the battery modules or battery packs provided in this application. The lithium-ion battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include 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., but is not limited thereto.

[0110] As the electrical device, a lithium-ion battery, battery module, or battery pack can be selected according to its usage requirements.

[0111] Figure 6This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of lithium-ion batteries for this device, a battery pack or battery module can be used.

[0112] 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.

[0113] Example 1

[0114] Based on the parameters in Table 1, prepare a lithium-ion battery according to the following steps.

[0115] 1) Preparation of positive electrode sheet

[0116] LiNi will be used as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (its specific surface area is bm) 2 The conductive carbon black SP (as shown in Table 1) and the polyvinylidene fluoride (PVDF) as a binder are dispersed in N-methylpyrrolidone (NMP) as a solvent at a mass ratio of 97:2:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and after drying, cold pressing, slitting and cutting, a positive electrode sheet is obtained.

[0117] 2) Preparation of negative electrode sheet

[0118] Graphite (with a specific surface area of ​​cm²) will be used as the negative electrode active material. 2 (as shown in Table 1), conductive carbon black SP as a conductive agent and SBR as a binder are dispersed in deionized water as a solvent at a mass ratio of 97:2:1 and mixed evenly to obtain a negative electrode slurry; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil; after drying, cold pressing, slitting and cutting, a negative electrode sheet is obtained.

[0119] 3) Diaphragm

[0120] Polyethylene film is used as the diaphragm.

[0121] 4) Preparation of electrolyte

[0122] In an argon-atmospheric glove box (H2O content < 10 ppm, O2 content < 1 ppm), ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a mass ratio of 25:70, and 1 mol / L LiPF6 lithium salt was dissolved. Then, additives were added, and the mixture was stirred until homogeneous to prepare the electrolyte. The additive in this electrolyte was lithium fluorosulfonate, which accounted for an awt% of the electrolyte mass, as shown in Table 1.

[0123] 5) Preparation of lithium-ion batteries

[0124] The above-mentioned positive electrode, separator, and negative electrode are assembled and then injected with electrolyte to prepare a soft-pack lithium-ion battery.

[0125] The following performance characteristics of the lithium-ion battery were tested.

[0126] (1) Gas production test at 60℃

[0127] The following steps were used to repeatedly test the gas volume of the lithium-ion battery and calculate the gas production per unit volume of the lithium-ion battery.

[0128] The oven temperature was adjusted to 25℃. The prepared lithium-ion battery was placed in the oven and left to stand for 60 minutes. It was then charged at a constant current of 0.5C to 4.2V, followed by constant voltage charging at 4.2V with a cutoff current of 0.05C (this is considered a full charge, 100% SOC). After standing for 10 minutes, it was discharged at 0.2C to 2.8V. The discharge capacity at this step was recorded as C0. After standing for 10 minutes, the cell was fully charged (100% SOC) using the same steps. After standing for 10 minutes, the cell was removed from the test channel and its volume was measured using the water displacement method, recorded as V0. The oven temperature was adjusted to 60℃. The cell with the measured volume was placed in the oven for high-temperature storage. After 3 days, the cell was removed, cooled to room temperature, and its volume was measured using the water displacement method, recorded as V. n Gas production per unit volume of the battery cell = (V n -V0) / C0. Repeat the above test steps and record the gas production of the cell at 60℃ until the cell volume expands to 50% of its original size.

[0129] (2) Initial DCR performance test at 25℃

[0130] The following steps are used to perform an initial DCR test on a lithium-ion battery.

[0131] The oven temperature was adjusted to 25℃. The prepared lithium-ion battery was placed in the oven and left to stand for 60 minutes. It was then charged at a constant current of 0.5C to 4.2V, followed by constant voltage charging at 4.2V with a cutoff current of 0.05C (this is considered a full charge, 100% SOC). After standing for 10 minutes, it was discharged at 0.2C to 2.8V. The discharge capacity of this step was recorded as C0. After standing for 10 minutes, the battery was placed in the 25℃ oven and left to stand for 60 minutes. The lithium-ion battery was then charged at a constant current of 0.5C to 4.2V, followed by constant voltage charging at 4.2V with a cutoff current of 0.05C (100% SOC). After standing for 10 minutes, it was discharged at 0.5C for 60 minutes, followed by standing for 60 minutes. Finally, it was discharged at 4C for 60 seconds (with a step interval of 0.1 seconds). The voltage and current of the cell before and after the 4C discharge were extracted and recorded as V. t0 Vt1 I t0 I t1 DCR = (V t1 -V t0 ) / (I t0 -I t1 ).

[0132] The test results are shown in Table 1.

[0133] Examples 2-6

[0134] As shown in Table 1, except for the different mass percentage (a wt%) of fluorosulfonate in the electrolyte, the preparation and testing were the same as in Example 1.

[0135] Examples 7-11

[0136] As shown in Table 1, except for the specific surface area (bm²) of the positive electrode active material 2 Except for the difference in g), it was prepared and tested in the same manner as in Example 1.

[0137] Examples 12-14

[0138] As shown in Table 1, except for the specific surface area (cm²) of the negative electrode active material 2 Except for the difference in g), it was prepared and tested in the same manner as in Example 1.

[0139] Example 15

[0140] Except for replacing lithium fluorosulfonate with sodium fluorosulfonate, the preparation and testing were the same as in Example 1, and the results are shown in Table 1.

[0141] Example 16

[0142] Except for replacing lithium fluorosulfonate with potassium fluorosulfonate, the preparation and testing were the same as in Example 1, and the results are shown in Table 1.

[0143] Examples 17-21

[0144] As shown in Table 1, except that the electrolyte additives also include lithium difluorophosphate and the mass percentage (d wt%) of lithium difluorophosphate in the electrolyte is different, the preparation and testing are the same as in Example 1.

[0145] Example 22

[0146] In addition to using LiNi as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 replaced with LiNi 0.6 Co 0.2 Mn 0.2 Except for O2, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0147] Example 23

[0148] In addition to using LiNi as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 replaced with LiNi 0.7 Co 0.2 Mn 0.1 Except for O2, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0149] Examples 24-25

[0150] Except for the parameters shown in Table 1, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0151] Comparative Examples 1-2

[0152] As shown in Table 1, except for the specific surface area (bm²) of the positive electrode active material 2 Except for the difference in g), it was prepared and tested in the same manner as in Example 1.

[0153] Comparative Example 3

[0154] Except that the electrolyte does not contain any additives, it was prepared and tested in the same manner as in Example 1, and the results are shown in Table 1.

[0155] Comparative Examples 4-5

[0156] As shown in Table 1, except for the different mass percentage (a wt%) of fluorosulfonate in the electrolyte, the preparation and testing were the same as in Example 1.

[0157] Comparative Example 6

[0158] Except that the additive was replaced with lithium fluoride instead of lithium fluorosulfonate, the preparation and testing were the same as in Example 1, and the results are shown in Table 1.

[0159] Comparative Example 7

[0160] In addition to using LiNi as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 replaced with LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Except for O2, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0161] Table 1

[0162]

[0163]

[0164] According to Table 1, by comparing the embodiments of this application with the comparative examples, it can be seen that the technical solutions of the embodiments of this application effectively improve the gas production and power performance of the battery.

[0165] Referring to Example 1 and Comparative Examples 1-2, when the specific surface area of ​​the positive electrode active material in the battery system is too small (less than 0.2 m²), 2 / g) or too large (greater than 1.8m) 2 When the concentration of fluorosulfonate in the electrolyte additive is / g), the effect of fluorosulfonate on improving battery gas production and power performance is significantly insufficient.

[0166] Referring to Example 1 and Comparative Example 3, when the electrolyte does not contain fluorosulfonate, it has almost no effect on improving the gas generation and power performance of the battery.

[0167] Referring to Example 1 and Comparative Examples 4-5, the content of fluorosulfonate in the electrolyte has a significant impact on whether it can effectively improve battery performance. When its content is too low (below 0.005 wt%), the reaction between it and the positive electrode surface is too weak to improve gas production. When its content is too high (above 0.1 wt%), the reaction between it and the positive electrode is strong, which has a certain negative impact on battery performance, resulting in poor gas production and power performance.

[0168] Referring to Example 1 and Comparative Example 6, the use of other additives, such as lithium fluoride, in the electrolyte did not improve the gas generation performance of the battery. This is mainly because lithium fluoride is relatively stable and cannot perform the same function as fluorosulfonates in forming the CEI film, thus failing to improve gas generation and power performance.

[0169] Referring to Example 1 and Comparative Example 7, when a low-nickel cathode active material is used, its gas generation problem is not as serious as that of a high-nickel cathode active material because the activity of the low-nickel cathode active material is relatively weak, and the improvement effect of fluorosulfonate on its gas generation is also weak.

[0170] The test results of each embodiment show that when the ratio of the specific surface area of ​​the positive electrode active material to that of the negative electrode active material (b / c) is between 0.14 and 1.81, both can improve the gas generation and power performance of the battery. Furthermore, referring to embodiments 7-14 and 24-25, it is evident that a b / c value of 0.40-1.14 is beneficial for further improving both gas generation and power performance simultaneously.

[0171] The test results from each embodiment show that, regarding the relationship between a, b, and c, a / (b / c) can vary within a wide range, all of which have a certain effect on improving battery performance. In particular, the improvement effect is more significant when 1.75≤100a / (b / c)≤17.5 is satisfied.

[0172] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A lithium-ion secondary battery, characterized in that, Includes positive electrode, negative electrode, membrane, and electrolyte; The positive electrode includes a positive electrode active material, which is Li. n Ni x Co y M z O f A g Wherein, 0.8≤n≤1.2, 0.5≤x≤0.98, 0≤y≤0.5, 0≤z≤0.5, f=2, g=0, element M is selected from at least one of Mn, Al, Zr, Ti, V, Mg, Fe, B, Mo, and element A is selected from at least one of S, N, P, F, Cl, Br, I; the specific surface area of ​​the positive electrode active material is greater than 0.4 m². 2 / g and less than 1.8 m 2 / g; the negative electrode includes a negative electrode active material, the specific surface area of ​​which is greater than or equal to 0.7 m². 2 / g and less than 2.5 m 2 / g; The electrolyte contains additives, including fluorosulfonates; the fluorosulfonates account for 0.02% to 0.1% of the mass of the electrolyte; the fluorosulfonates include at least one of lithium fluorosulfonate, sodium fluorosulfonate, and potassium fluorosulfonate. The fluorosulfonate accounts for a wt% of the electrolyte, and the specific surface area of ​​the positive electrode active material is bm. 2 / g, the specific surface area of ​​the negative electrode active material is cm² 2 / g; The relationship between a, b, and c satisfies 1.75≤100a / (b / c)≤17.

5.

2. The lithium-ion secondary battery as described in claim 1, characterized in that, The specific surface area of ​​the positive electrode active material is greater than 0.4 m². 2 / g and less than or equal to 1.3 m 2 / g.

3. The lithium-ion secondary battery as described in claim 1, characterized in that, The fluorosulfonate accounts for 0.02% to 0.06% of the mass of the electrolyte.

4. The lithium-ion secondary battery as described in claim 1, characterized in that, The specific surface area of ​​the positive electrode active material is bm 2 / g, the specific surface area of ​​the negative electrode active material is cm² 2 / g; the ratio of b to c is 0.14~1.

81.

5. The lithium-ion secondary battery as described in claim 4, characterized in that, The ratio of b to c is 0.40 to 1.

14.

6. The lithium-ion secondary battery as described in claim 1, characterized in that, The additive also includes difluorophosphate; the difluorophosphate accounts for 0.001% to 0.1% of the mass of the electrolyte.

7. The lithium-ion secondary battery as described in claim 6, characterized in that, The difluorophosphate accounts for 0.001% to 0.08% of the mass of the electrolyte.

8. An electrical device, characterized in that, The electrical device includes the lithium-ion secondary battery as described in any one of claims 1 to 7.

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