A secondary battery and an electric device including the same

Abstract

This application provides a secondary battery and an electrical device including the secondary battery. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode material layer, which includes a silicon-containing material. The silicon-containing material particles include silicon elements, and the mass percentage B of the silicon elements is 5% to 85% based on the mass of the silicon-containing material. The electrolyte includes one or more fluorosulfonamide compounds represented by formula (I), and the mass percentage A of the fluorosulfonamides is 10% to 80% based on the mass of the electrolyte. The negative electrode and electrolyte in the secondary battery provided by this application meet the above characteristics and can significantly improve the cycle performance and high-temperature storage performance of the secondary battery.

Description

[0001] This invention is a divisional application of application number 202310326821.3, filed on March 30, 2023, entitled "A secondary battery and an electrical device including the secondary battery". Technical Field

[0002] This application relates to the field of electrochemical technology, and in particular to a secondary battery and an electrical device including the secondary battery. Background Technology

[0003] With the rapid development of electronic products, rechargeable batteries, due to their advantages such as high energy density, miniaturization, and lightweight design, are widely used in mobile phones, laptops, tablets, drones, electric vehicles, power tools, and power storage systems. Especially in the 3C product sector, consumers still have a significant demand for improved battery life, thus placing even higher requirements on the energy density of rechargeable batteries.

[0004] To further improve the energy density of secondary batteries, high-capacity electrode materials are required. Silicon-based materials, as a type of alloyed anode material, can provide an ultra-high specific capacity of up to 4200 mAh / g, making them a highly promising material for improving energy density. However, lithiation of silicon-based materials forms lithium-silicon alloys, which are highly reactive and readily attack solvent molecules in the electrolyte, leading to rapid electrolyte consumption and loss of active lithium. This results in poor cycle performance and poor high-temperature storage performance. Summary of the Invention

[0005] The purpose of this application is to provide a secondary battery and an electrical device including the secondary battery, so as to improve the cycle performance and high-temperature storage performance of the secondary battery. The specific technical solution is as follows:

[0006] This application provides a secondary battery, which includes a positive electrode, a negative electrode and an electrolyte. The negative electrode includes a negative electrode material layer, the negative electrode material layer includes a silicon-containing material, the particles of the silicon-containing material include silicon element, and the mass percentage B of the silicon element is 5% to 85% based on the mass of the silicon-containing material.

[0007] The electrolyte comprises one or more fluorosulfonamide compounds represented by formula (I):

[0008]

[0009] R1 is selected from C1 to C2 atoms that are fluorine-atom substituted with all or part of the fluorine. 10 Alkyl, wholly or partially fluorinated C6 to C 10 aryl, wholly or partially fluorinated C1 to C 10Oxyalkyl, wholly or partially fluorinated C6 to C 10 The oxygen-containing aryl group; the O atom in R1 is not directly bonded to the S atom; R2 and R3 are each independently selected from substituted or unsubstituted C1 to C5 alkyl groups, substituted or unsubstituted C6 to C5 alkyl groups. 10 The aryl group, wherein the substituent in the substituted C1 to C5 alkyl group is a fluorine atom, and the substituted C6 to C5 alkyl group... 10 The substituents in the aryl group are fluorine atoms;

[0010] Based on the mass of the electrolyte, the mass percentage A of the fluorosulfonamide is 10% to 80%.

[0011] The negative electrode and electrolyte in the secondary battery provided in this application meet the above-mentioned characteristics, which can significantly improve the cycle performance and high-temperature storage performance of the secondary battery.

[0012] In some embodiments of this application, the electrolyte further includes cyclic esters; based on the mass of the electrolyte, the mass percentage C of the cyclic esters is 10% to 50%, and the cyclic esters include at least one selected from ethylene carbonate, propylene carbonate, trimethylene carbonate, ethylene sulfate, propylene sulfate, or 1,3-propanediol cyclic sulfate; the mass percentage A of the fluorosulfonamides is 10% to 70%. The addition of the above-mentioned cyclic esters to the electrolyte of this application is beneficial for promoting the dissolution and dissociation of lithium salts.

[0013] In some embodiments of this application, the electrolyte further comprises a fluorinated solvent, wherein the mass percentage E of the fluorinated solvent is 5% to 35% based on the mass of the electrolyte, and the fluorinated solvent includes at least one selected from fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl ethylene carbonate, trifluoroethanol acetate, or difluoroethanol acetate; and the mass percentage A of the fluorosulfonamide is 10% to 65%. The addition of the above-mentioned fluorinated solvent to the electrolyte of this application is beneficial to improving the cycle performance of the secondary battery.

[0014] In some embodiments of this application, the mass percentage B of silicon element is 5% to 65% based on the mass of the silicon-containing material. By adjusting the mass percentage of silicon element within the above range, the energy density of the secondary battery can be further improved.

[0015] In some embodiments of this application, the silicon-containing material includes silicon-oxygen composite materials or silicon-carbon composite materials, and the surface of the silicon-oxygen composite material or silicon-carbon composite material particles includes at least one of LiF, AlF3, Li2CO3, amorphous carbon, or graphitized carbon. By selecting the above-mentioned silicon-containing materials, the secondary battery can achieve better overall performance.

[0016] In some embodiments of this application, P1 = A / B, and the value of P1 is from 0.1 to 2, preferably from 0.5 to 2. By adjusting the value of P1 within the above range, the cycle performance and high-temperature storage performance of the secondary battery can be improved.

[0017] In some embodiments of this application, P2 = A / C, and the value of P2 ranges from 1 to 7. By adjusting the value of P2 within the above range, the cycle performance and high-temperature storage performance of the secondary battery can be further improved.

[0018] In some embodiments of this application, A is 20% to 60%. By adjusting the value of A within the above range, the cycle performance and high-temperature storage performance of the secondary battery can be further improved.

[0019] This application includes an electrical device comprising a secondary battery as described in any of the foregoing embodiments. Therefore, the electrical device provided by this application has high energy density, good cycle life, and high-temperature storage performance.

[0020] The beneficial effects of this application are:

[0021] This application provides a secondary battery and an electrical device including the secondary battery. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a negative electrode material layer, which includes a silicon-containing material. The silicon-containing material particles include silicon elements, and the mass percentage B of the silicon elements is 5% to 85% based on the mass of the silicon-containing material. The electrolyte includes one or more fluorosulfonamide compounds represented by formula (I), and the mass percentage A of the fluorosulfonamides is 10% to 80% based on the mass of the electrolyte. The negative electrode and electrolyte in the secondary battery provided by this application meet the above characteristics and can significantly improve the cycle performance and high-temperature storage performance of the secondary battery.

[0022] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Detailed Implementation

[0023] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art are within the scope of protection of this application.

[0024] It should be noted that, in the following explanation, lithium-ion batteries are used as an example of secondary batteries to illustrate this application; however, the secondary batteries in this application are not limited to lithium-ion batteries. The specific technical solution is as follows:

[0025] The first aspect of this application provides a secondary battery, which includes a positive electrode, a negative electrode and an electrolyte. The negative electrode includes a negative electrode material layer, the negative electrode material layer includes a silicon-containing material, the particles of the silicon-containing material include silicon element, and the mass percentage B of silicon element is 5% to 85% based on the mass of the silicon-containing material.

[0026] The electrolyte includes one or more fluorosulfonamide compounds represented by formula (I):

[0027]

[0028] R1 is selected from C1 to C2 atoms that are fluorine-atom substituted with all or part of the fluorine. 10 Alkyl, wholly or partially fluorinated C6 to C 10 aryl, wholly or partially fluorinated C1 to C 10 Oxyalkyl, wholly or partially fluorinated C6 to C 10 The oxygen-containing aryl group; the O atom in R1 is not directly bonded to the S atom; R2 and R3 are each independently selected from substituted or unsubstituted C1 to C5 alkyl groups, substituted or unsubstituted C6 to C5 alkyl groups. 10 The aryl group, wherein the substituent in the substituted C1 to C5 alkyl group is a fluorine atom, and the substituted C6 to C5 alkyl group... 10 The substituents in the aryl group are fluorine atoms;

[0029] Based on the mass of the electrolyte, the mass percentage A of fluorosulfonamide is 10% to 80%.

[0030] Specifically, the mass percentage B of silicon can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or a range of any two of the above values. Preferably, B is from 5% to 65%. Specifically, the mass percentage A of the fluorosulfonamide compound can be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or a range of any two of the above values. Preferably, A is from 20% to 60%.

[0031] When the mass percentage of silicon is too low, such as below 5%, the energy density of the secondary battery will be relatively low; when the mass percentage of silicon is too high, such as above 85%, the secondary battery will expand significantly and have poor cycle performance. Without being limited to any particular theory, by controlling the mass percentage of silicon (B) within the above range, the energy density of the secondary battery can be significantly improved. At the same time, the expansion and deformation of the negative electrode material layer caused by silicon lithiation can be controlled through electrode engineering, preventing structural failure of the secondary battery.

[0032] Without being limited to any particular theory, by selecting the fluorosulfonamide compound represented by formula (I) above, the attack of the active lithium-silicon alloy generated after lithium intercalation of silicon-based materials on the electrolyte solvent can be reduced, thus delaying electrolyte consumption and effectively improving the cycle life of the secondary battery. It can also slow down the accumulation of interfacial byproducts, effectively suppressing expansion during the secondary battery cycle. Furthermore, due to the enhanced electrolyte stability, the problem of high-temperature gas generation in the secondary battery can also be improved. When the mass percentage of the fluorosulfonamide compound is too low, for example below 10%, the cycle performance of the secondary battery is poor and high-temperature gas generation is severe. When the mass percentage of the fluorosulfonamide compound is too high, for example above 80%, its single-component effect reaches its limit, while adding cyclic esters and fluorinated solvents can achieve further improved performance. Without being limited to any particular theory, controlling the mass percentage A of the fluorosulfonamide compound within the above range is more conducive to improving the cycle performance of the secondary battery, while simultaneously achieving a balance between the lithium salt dissociation degree, viscosity, and conductivity of the electrolyte.

[0033] For example, the fluorosulfonamide compound represented by formula (I) is selected from at least one of the following formulas (I-1) to (I-32):

[0034]

[0035]

[0036]

[0037] The electrolyte also includes linear carbonates and / or linear carboxylic acid esters, wherein the mass percentage (D) of the linear carbonates and / or linear carboxylic acid esters is 4% to 75% based on the mass of the electrolyte. The linear carbonates may include, but are not limited to, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butyl carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, and 1,1,2-trifluoroethylene carbonate. The electrolyte contains at least one of the following: 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The linear carboxylic acid ester may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate, mevalonate lactone, or caprolactone. Without being limited to any particular theory, by selecting the above-mentioned linear carbonates and / or linear carboxylic acid esters, the viscosity of the electrolyte can be reduced, ensuring the ionic conductivity of the electrolyte.

[0038] The electrolyte also includes lithium salts, which constitute 10% to 20% of the electrolyte by mass. The lithium salts may be, but are not limited to, one or a combination of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate, lithium tetraborate, lithium perchlorate, lithium difluorophosphate, lithium difluorodioxalate phosphate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluoromethanesulfonyl)imide. By selecting the above lithium salts, a suitable ionic conductivity can be obtained in the electrolyte.

[0039] Therefore, the secondary battery provided in this application, by selecting the fluorosulfonamide compound represented by the above formula (I) and adjusting the mass percentage of the compound and the mass percentage of silicon element within the above range, can significantly improve the cycle performance and high-temperature storage performance of the secondary battery.

[0040] In some embodiments of this application, the electrolyte further includes cyclic esters; based on the mass of the electrolyte, the mass percentage C of the cyclic esters is 10% to 50%, and the cyclic esters include at least one selected from ethylene carbonate, propylene carbonate, trimethylene carbonate, ethylene sulfate, propylene sulfate, or 1,3-propanediol cyclic sulfate; the mass percentage A of the fluorosulfonamides is 10% to 70%. Specifically, the mass percentage C of the cyclic esters can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, or a range consisting of any two of the above values. Specifically, the mass percentage A of the fluorosulfonamide can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range of any two of the above values. Without being limited to any theory, the above-mentioned cyclic esters have high solubility for cations and Lewis bases (DN value) and dielectric constant. Controlling the percentage content of the cyclic ester within the above range helps to promote the dissolution and dissociation of the lithium salt. The electrolyte also includes linear carbonates and / or linear carboxylic acid esters, with a mass percentage D of 4% to 70% based on the mass of the electrolyte; the electrolyte also includes lithium salts, with a mass percentage of 10% to 20% based on the mass of the electrolyte.

[0041] In some embodiments of this application, the electrolyte further comprises a fluorinated solvent, wherein the mass percentage E of the fluorinated solvent, based on the mass of the electrolyte, is 5% to 35%, and the fluorinated solvent includes at least one selected from fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl ethylene carbonate, trifluoroethanol acetate, or difluoroethanol acetate; and the mass percentage A of the fluorosulfonamide is 10% to 65%. Specifically, the mass percentage E of the fluorinated solvent can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, or a range consisting of any two of the above values. Specifically, the mass percentage A of the fluorosulfonamide can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or a range consisting of any two of the above values. Without being limited to any particular theory, by controlling the percentage content of the fluorinated solvent within the aforementioned range, the reduction reaction potential of the fluorinated solvent is greater than 0.5V, and it readily generates lithium fluoride products, which assist in the interfacial passivation effect. This further suppresses the reaction between the lithium-silicon alloy and the electrolyte, resulting in a superior cycle life for the secondary battery. The electrolyte also includes cyclic esters, with the mass percentage C of the cyclic esters ranging from 10% to 50% based on the mass of the electrolyte; the electrolyte also includes linear carbonates and / or linear carboxylic acid esters, with the mass percentage D of the linear carbonates and / or linear carboxylic acid esters ranging from 4% to 65% based on the mass of the electrolyte; and the electrolyte also includes lithium salts, with the mass percentage of lithium salts ranging from 10% to 20% based on the mass of the electrolyte.

[0042] In this application, silicon-containing materials refer to materials of any composition containing silicon element that are electrochemically active and can contribute reversible capacity through lithium insertion and extraction. This application does not impose any particular limitation on the silicon-containing material; for example, it can be silicon nanoparticles, silicon nanowires, micron-sized silicon, or silicon-oxygen composites (SiO₂). x The silicon-containing material is selected from at least one of the following: silicon-carbon composite material (SiC) or silicon-containing alloy (silicon-tin alloy, silicon-magnesium alloy, or silicon-aluminum alloy), where x is 0 to 2. The silicon-containing material may have at least one of LiF, AlF3, Li2CO3, amorphous carbon, or graphitized carbon on its surface. In some embodiments of this application, the silicon-containing material includes silicon-oxygen composite material or silicon-carbon composite material, and the surface of the silicon-oxygen composite material or silicon-carbon composite material particles includes at least one of LiF, AlF3, Li2CO3, amorphous carbon, or graphitized carbon. Without being limited to any particular theory, by selecting the above-mentioned silicon-containing material, the processing of the negative electrode slurry and electrode sheet can be simplified, and the secondary battery can achieve better overall performance.

[0043] In some embodiments of this application, P1 = A / B, and the value of P1 is from 0.1 to 2. For example, P1 can be 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, or a range of any two of the above values. Preferably, the value of P1 is from 0.5 to 2. Without being limited to any theory, by controlling the value of P1 within the above range, the possibility of the lithium-silicon alloy formed after lithium intercalation of silicon material attacking the electrolyte solvent can be reduced to a large extent, while balancing the viscosity and conductivity of the electrolyte.

[0044] In some embodiments of this application, P2 = A / C, and the value of P2 ranges from 1 to 7. For example, P2 can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, or a range of any two of the above values. Without being limited to any theory, by controlling the value of P2 within the above range, the reductive decomposition of the aforementioned cyclic esters into films facilitates the formation of an organic solid electrolyte interfacial (SEI) film, further suppressing solvent decomposition reactions and resulting in better interfacial stability of the electrolyte.

[0045] In this application, the electrolyte also includes additives. There are no particular limitations on the types of additives used; additives known in the art can be employed. For example, additives may include, but are not limited to, one or more of 1,3-propanesulfonate lactone, glutaronitrile, methylglutaronitrile, adiponitrile, heptanonitrile, octanoic acid nitrile, 1,3,5-pentanetrionitrile, 1,3,6-hexanetrionitrile, or 1,2,3-tris(2-cyanoxy)propane. Without being limited to any particular theory, by selecting the above-mentioned additives, side reactions between the positive electrode and the electrolyte under high voltage can be suppressed, further optimizing the overall performance of the secondary battery.

[0046] In this application, the electrolyte also includes other non-aqueous solvents. This application does not impose any particular limitation on other non-aqueous solvents, as long as they can achieve the purpose of this application. For example, other non-aqueous solvents may include, but are not limited to, at least one of the following: dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters.

[0047] This application does not particularly limit the preparation method of silicon-containing materials. Exemplarily, the preparation method of silicon-containing materials may include, but is not limited to, the following steps: dissolving silicon material and lithium nitrate in a solvent, mixing them evenly, drying to obtain a powder material, and then heat-treating the powder material in a carbon-containing gas to obtain the silicon-containing material. Specifically, the drying temperature is 80°C to 120°C; the heat treatment temperature is 300°C to 800°C, the heating rate is 1°C / min to 10°C / min, and the holding time is 0.5h to 6h; the mass ratio of silicon material to lithium nitrate can be (10 to 200):1; the silicon material can be silicon-carbon material, silicon-oxygen material, or pre-lithiated silicon-oxygen material; the solvent can be, but is not limited to, at least one of ethanol, water, or acetone; the carbon-containing gas includes at least one of acetylene, methane, or propylene; and the mass ratio of powder material to carbon-containing gas can be (20 to 100):1. In this application, the mass percentage of silicon element in the silicon-containing material can be controlled by adjusting the mass ratio of silicon material to lithium nitrate.

[0048] In this application, the secondary battery further includes a positive electrode sheet, which includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the positive current collector or only a portion of it; this application does not have any particular limitation, as long as the purpose of this application is achieved.

[0049] This application does not impose any particular restrictions on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collector (such as aluminum-carbon composite current collector).

[0050] The positive electrode material layer includes a positive electrode active material. This application does not impose any particular limitation on the positive electrode active material, as long as it achieves the purpose of this application. For example, the positive electrode active material may include, but is not limited to, at least one of lithium nickel cobalt manganese oxide (e.g., common NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate. In this application, the positive electrode active material may also contain non-metallic elements, such as at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur. These elements can further improve the stability of the positive electrode active material.

[0051] The positive electrode material layer also includes a conductive agent and a binder. This application does not particularly limit the types of conductive agents and binders, as long as they can achieve the purpose of this application. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, graphene, metallic materials, or conductive polymers. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride. This application does not impose any particular restrictions on the mass ratio of positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0052] This application does not impose any particular limitation on the thickness of the positive current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm, and the thickness of the positive electrode material layer is 30 μm to 120 μm. This application does not impose any particular limitation on the thickness of the positive electrode sheet, as long as the purpose of this application can be achieved, for example, the thickness of the positive electrode sheet is 40 μm to 150 μm. Optionally, the positive electrode sheet may also include an undercoating layer, which is located between the positive current collector and the positive electrode material layer. The composition of the undercoating layer is not particularly limited and can be a commonly used undercoating layer in the art.

[0053] In this application, the secondary battery further includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "the negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the negative electrode current collector, or only a portion thereof; this application does not have any particular limitation, as long as the purpose of this application is achieved.

[0054] This application does not impose any particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collectors (such as carbon copper composite current collectors, nickel copper composite current collectors, titanium copper composite current collectors, etc.).

[0055] In this application, the negative electrode material layer may also include other negative electrode active materials. This application does not impose any particular limitation on the types of other negative electrode active materials, as long as they can achieve the purpose of this application. For example, other negative electrode active materials may include, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, and spinel-structured lithium titanate Li4Ti5O. 12 At least one of Li-Al alloy or metallic lithium.

[0056] The negative electrode material layer also includes a conductive agent and a binder. This application does not particularly limit the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, it can be at least one of the aforementioned conductive agents and binders. This application does not particularly limit the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. The negative electrode material layer may also include a thickener. This application does not particularly limit the content and type of thickener; conventional types and contents known in the art can be used, as long as the purpose of this application is achieved.

[0057] This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode material layer can be from 30 μm to 120 μm. This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector can be from 5 μm to 16 μm. This application does not impose any particular limitation on the thickness of the negative electrode sheet, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode sheet can be from 50 μm to 160 μm.

[0058] Optionally, the negative electrode sheet may further include a base coating layer, which may be disposed on one surface or two surfaces in the thickness direction of the negative electrode current collector. Further, the base coating layer may be disposed between the negative electrode current collector and the negative electrode material layer. It should be noted that the term "surface" here can refer to the entire area of ​​the negative electrode current collector or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the composition of the base coating layer, which can be a commonly used base coating layer in the art. For example, the base coating layer includes a conductive agent and a binder. The conductive agent includes at least one of carbon fiber, Ketjen black, acetylene black, carbon nanotubes, or graphene; the binder includes at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene, styrene-butadiene rubber, acrylate, or epoxy resin. This application does not impose any particular limitation on the thickness of the primer layer; for example, the thickness of the primer layer may be from 0.1 μm to 5 μm.

[0059] In this application, the secondary battery also includes a separator membrane to separate the positive and negative electrode plates, prevent internal short circuits, allow electrolyte ions to pass freely, and not affect the electrochemical charging and discharging process. This application does not impose any particular limitations on the separator membrane, as long as it achieves the purpose of this application. For example, the material of the separator membrane may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the type of separator membrane may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0060] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. For example, the inorganic layer includes inorganic particles and a binder. The inorganic particles are not particularly limited and may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder is not particularly limited and may be at least one of the binders described above. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0061] In this application, the secondary battery may include, but is not limited to, lithium-ion secondary batteries or sodium-ion secondary batteries.

[0062] The preparation process of the secondary battery described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, overcurrent protection components, conductive plates, etc., may be placed in the packaging bag as needed to prevent the internal pressure of the secondary battery from rising and overcharging / discharging. The packaging bag is any packaging bag known in the art, and this application does not limit its use.

[0063] This application includes an electrical device comprising a secondary battery as described in any of the foregoing embodiments. Therefore, the electrical device provided by this application has high energy density, good cycle life, and high-temperature storage performance. This application does not particularly limit the type of electrical device; it can be any electrical device known in the prior art. In some embodiments, the electrical device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0064] Example

[0065] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0066] Test methods and equipment:

[0067] Cyclic performance testing:

[0068] The lithium-ion battery was placed in a 45°C constant temperature test chamber and left to stand for 30 minutes to reach a constant temperature of 45°C. It was then charged at a constant current of 0.5C to 4.5V, followed by constant voltage charging to a current of 0.025C. After standing for 5 minutes, it was discharged at a constant current of 0.5C to 3.0V. The initial discharge capacity was recorded as C0, and the thickness of the lithium-ion battery in the discharged state was recorded as the initial thickness T0. This process was repeated 100 times, and the discharge capacity C1 and the thickness T1 of the lithium-ion battery in the discharged state were recorded after 100 cycles.

[0069] Cyclic capacity retention rate = C1 / C0 × 100%

[0070] Cyclic thickness expansion rate = (T1-T0) / T0×100%.

[0071] High-temperature storage performance testing:

[0072] The lithium-ion battery was placed in a constant temperature environment of 25℃ and left to stand for 30 minutes to reach the constant temperature state. It was then charged at a constant current of 0.7C to 4.5V, followed by constant voltage charging to a current of 0.025C. The thickness of the lithium-ion battery was recorded as the initial thickness H0. The lithium-ion battery was then transferred to a constant temperature chamber at 60℃ and stored for 30 days. During this period, the thickness of the lithium-ion battery was measured and recorded every 6 days. The measured thickness recorded after 30 days was the storage thickness H1.

[0073] High-temperature storage thickness expansion rate = (H1-H0) / H0×100%.

[0074] Test for silicon elemental mass percentage:

[0075] Apply conductive adhesive to the sample stage, take the powdered sample of silicon-containing material from each embodiment and spread it evenly on the conductive adhesive, blow away the unadheded powder with a syringe, spray gold, and use the X-ray energy dispersive spectroscopy (EDS) instrument equipped with a Philips XL-30 field emission scanning electron microscope at an accelerating voltage of 10 kV and an emission current of 10 mA to perform an X-ray scanning test to determine the mass percentage of silicon.

[0076] Example 1-1

[0077] <Preparation of Silicon-Containing Substances>

[0078] SiO2 and lithium nitrate were dispersed in ethanol, mixed evenly, and dried to obtain a powder. The powder was then heat-treated in methane to obtain a silicon-containing material with amorphous carbon on its surface. The drying temperature was 100℃; the heat treatment temperature was 450℃, the heating rate was 5℃ / min, and the holding time was 3.2 h; the mass ratio of SiO2 to lithium nitrate was 36:1; and the mass ratio of powder to methane was 30:1. The silicon content of the silicon-containing material was 65% by mass.

[0079] <Preparation of Negative Electrode Sheets>

[0080] The aforementioned silicon-containing material, CNT, Super P, and lithium polyacrylate (PAA-Li) were mixed in a mass ratio of 90:1.5:0.5:8, and then deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 54%. The mixture was stirred under vacuum until it became a homogeneous negative electrode slurry. The conductive agent Super P and binder SBR were mixed in a mass ratio of 9:1, and then deionized water was added as a solvent to prepare a base coating slurry with a solid content of 10%. The base coating slurry and the negative electrode slurry were sequentially and uniformly coated onto one surface of an 8μm thick copper foil for the negative electrode current collector, and dried at 85°C to obtain a single-sided coated negative electrode sheet with a base coating thickness of 2μm and a negative electrode material layer thickness of 100μm. The above steps were then repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After coating, the negative electrode sheet was cold-pressed and cut into 76mm × 851mm dimensions for later use.

[0081] <Preparation of the positive electrode>

[0082] Lithium cobalt oxide (LiCoO2), a conductive agent (Super P), and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 97:1.4:1.6. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75%. The mixture was stirred under vacuum until a homogeneous positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil current collector and dried at 85°C to obtain a single-sided positive electrode sheet with a positive electrode material layer thickness of 110 μm. The above steps were then repeated on the other surface of the positive electrode sheet to obtain a double-sided positive electrode sheet. After coating, the positive electrode sheet was cold-pressed and cut into 74 mm × 867 mm dimensions for later use.

[0083] <Preparation of Electrolyte>

[0084] In an argon atmosphere glove box with a water content of less than 10 ppm, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 1:1. Then, compound formula (I-1) representing formula (I) with a mass percentage of A is added to the base solvent, followed by the addition of compound formula (I-1) with a mass percentage of W. V Lithium bis(fluorosulfonyl)imide was dissolved and mixed evenly, and stirred until homogeneous to obtain an electrolyte. The mass percentage (W) of lithium bis(fluorosulfonyl)imide was determined based on the mass of the electrolyte. V The mass percentage of the compound represented by formula (I) is 15.4%, A is 80%, and W is the mass percentage of the base solvent. J It is 4.6%.

[0085] <Isolation membrane>

[0086] A 5μm thick polyethylene (PE) porous membrane (supplied by Celgard) was used.

[0087] <Preparation of Lithium-ion Batteries>

[0088] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging shell and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation (0.02C constant current charging to 3.5V, then 0.1C constant current charging to 3.9V), shaping, and capacity testing.

[0089] Examples 1-2 to 1-35

[0090] Except for adjusting the relevant preparation parameters according to Table 1 in <Preparation of Electrolyte> and <Preparation of Silicon-containing Substance>, the rest are the same as in Examples 1-1.

[0091] Examples 2-1 to 2-12

[0092] Except for the addition of cyclic esters and adjustment of relevant preparation parameters according to Table 2 in the <Preparation of Electrolyte>, the rest is the same as in Examples 1-21.

[0093] Examples 3-1 to 3-6

[0094] Except for the addition of a fluorinated solvent and adjustment of the relevant preparation parameters according to Table 3 in the <Preparation of Electrolyte>, the rest is the same as in Examples 2-8.

[0095] Comparative Example 1-1

[0096] Except for the preparation of the electrolyte according to the steps in <Electrolyte Preparation>, the rest is the same as in Example 1.

[0097] <Preparation of Electrolyte>

[0098] In an argon atmosphere glove box with a water content of less than 10 ppm, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 1:1, and then W is added by mass percentage. V Lithium bis(fluorosulfonyl)imide was dissolved and mixed evenly, and stirred until homogeneous to obtain an electrolyte. The mass percentage (W) of lithium bis(fluorosulfonyl)imide was determined based on the mass of the electrolyte. V The percentage of W by mass of the base solvent is 15.4%. J It is 84.6%.

[0099] The relevant preparation parameters and performance tests for each embodiment and comparative example are shown in Tables 1 to 3.

[0100] Table 1

[0101]

[0102]

[0103] Note: In Table 1, " / " indicates that there are no relevant preparation parameters.

[0104] As can be seen from Examples 1-1 to 1-35 and Comparative Example 1-1, the mass percentage of silicon in the silicon-containing materials, the type and content of fluorosulfonamide compounds in the examples are all within the scope of this application, while the comparative examples do not simultaneously meet the above characteristics. The lithium-ion batteries in the examples of this application have high cycle capacity retention and low cycle thickness expansion rate and high-temperature storage thickness expansion rate, thus demonstrating that the lithium-ion batteries made using the electrolyte and silicon-containing materials provided in this application have good cycle performance and high-temperature storage performance.

[0105] Table 2

[0106]

[0107]

[0108] Note: In Table 2, " / " indicates that there are no relevant preparation parameters.

[0109] As can be seen from Examples 2-1 to 2-12, when cyclic esters are further added, and the types and contents of cyclic esters are within the scope of this application, the resulting lithium-ion batteries have higher cycle capacity retention and lower high-temperature storage thickness expansion rate, thus indicating that the cycle performance and high-temperature storage performance of lithium-ion batteries are further improved.

[0110] Table 3

[0111]

[0112] Note: In Table 3, " / " indicates that there are no relevant preparation parameters.

[0113] As can be seen from Examples 3-1 to 3-6, when a fluorinated solvent is further added, and the type and content of the fluorinated solvent are within the scope of this application, the resulting lithium-ion battery has a higher cycle capacity retention rate and a lower high-temperature storage thickness expansion rate, thus indicating that the cycle performance and high-temperature storage performance of the lithium-ion battery are further improved.

[0114] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode material layer, the negative electrode material layer comprises a silicon-containing material, the particles of the silicon-containing material comprising silicon element, and the mass percentage B of the silicon element B is 5% to 85% based on the mass of the silicon-containing material; The electrolyte comprises one or more fluorosulfonamide compounds represented by formula (I): ； in, R1 is selected from C1 to C1, where fluorine atoms are present or partially substituted with fluorine. 10 Alkyl, wholly or partially fluorinated C6 to C 10 aryl, wholly or partially fluorinated C1 to C 10 Oxyalkyl, wholly or partially fluorinated C6 to C 10 The oxygen-containing aryl group; the O atom in R1 is not directly bonded to the S atom; R2 and R3 are each independently selected from substituted or unsubstituted C1 to C5 alkyl groups, substituted or unsubstituted C6 to C5 alkyl groups. 10 The aryl group, wherein the substituent in the substituted C1 to C5 alkyl group is a fluorine atom, and the substituted C6 to C5 alkyl group... 10 The substituents in the aryl group are fluorine atoms; Based on the mass of the electrolyte, the mass percentage A of the fluorosulfonamide is 10% to 70%; The electrolyte further comprises a fluorinated solvent, and the mass percentage E of the fluorinated solvent is 5% to 35% based on the mass of the electrolyte. The fluorinated solvent includes at least one of fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl ethylene carbonate, trifluoroethanol acetate, or difluoroethanol acetate. The electrolyte further includes cyclic esters; based on the mass of the electrolyte, the mass percentage C of the cyclic esters is 10% to 40%, and the cyclic esters include at least one of ethylene carbonate, propylene carbonate, trimethylene carbonate, ethylene sulfate, propylene sulfate, or 1,3-propanediol cyclic sulfate. Where P1 = A / B, the value of P1 is 0.1 to 2; P2 = A / C, the value of P2 is 1 to 7.

2. The secondary battery according to claim 1, wherein, The mass percentage A of the fluorosulfonamide is 10% to 65%.

3. The secondary battery according to any one of claims 1 to 2, wherein, Based on the mass of the silicon-containing material, the mass percentage B of the silicon element is 5% to 65%.

4. The secondary battery according to any one of claims 1 to 2, wherein, The silicon-containing material includes silicon-oxygen composite materials or silicon-carbon composite materials, and the surface of the silicon-oxygen composite material or silicon-carbon composite material particles includes at least one of LiF, AlF3, Li2CO3, amorphous carbon or graphitized carbon.

5. The secondary battery according to claim 1, wherein, The value of P1 ranges from 0.5 to 2.

6. The secondary battery according to any one of claims 1 to 2, wherein, The fluorosulfonamide compound represented by formula (I) is selected from at least one of the following formulas (I-1) to (I-32): 。 7. The secondary battery according to any one of claims 1 to 2, wherein, The percentage of A is 20% to 60%.

8. An electrical device comprising a secondary battery as described in any one of claims 1 to 7.

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