Battery and electronic equipment

Abstract

The invention relates to a battery and electronic equipment. The battery comprises a negative plate and an electrolyte, the negative plate comprises a negative current collector and a negative coating arranged on at least one side surface of the negative current collector; the negative electrode coating comprises a silicon-based material; the electrolyte comprises a first additive, a second additive, a third additive and a fourth additive; the first additive comprises a fluorosulfonamide compound; the second additive comprises an unsaturated carbonate compound; the third additive comprises a lithium salt additive; the fourth additive comprises a nitrile compound; the battery simultaneously satisfies the following relational expressions: 0.2 < = (A + B + C) / X < = 85 formula 1; formula 2: 0.1 < = D / (B + C) < = 2.4; 0.03 < = C / A < = 1.5 formula 3. According to the scheme provided by the invention, the battery can present excellent safety performance, high-temperature cycle performance and low-temperature cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery and an electronic device. BACKGROUND

[0002] Lithium ion batteries are widely used in 3C digital, power tools, aerospace, energy storage, electric vehicles and other fields due to their high specific energy, no memory effect, long cycle life and other advantages. The rapid development of electronic information technology and consumer products puts forward higher requirements for the electrochemical performance of lithium ion batteries.

[0003] At present, silicon-based negative electrode materials are considered as one of the most potential negative electrode materials for the next generation of high-energy-density lithium ion batteries due to their extremely high theoretical specific capacity (about 4200 mAh / g), suitable operating voltage and abundant natural reserves. However, silicon materials face severe challenges in practical application. The core problem is that silicon will undergo a huge volume change (expansion rate can reach more than 300%) during charging and discharging, which leads to problems such as active material particle breakage, repeated rupture and regeneration of solid electrolyte interface film (SEI film), poor electrode structure stability, and seriously affects the cycle performance and safety performance of the battery. In addition, the poor conductivity of silicon material itself also limits the performance of the battery at low temperature.

[0004] To address the above challenges, the industry generally tries to improve the structural stability of silicon negative electrode through nanocrystallization, compounding and other means, and focuses on optimizing the electrolyte formula to build a stable interface film. In the optimization of electrolyte, the use of functional additives is the key. However, a single additive often has limited functionality and is difficult to cope with the complex failure mechanism of the silicon negative electrode with multiple interfaces and multiple scales.

[0005] Therefore, developing a multi-component synergistic electrolyte system to solve the interface stability of silicon negative electrode, ion transport kinetics, and compatibility and thermal safety of the full battery has become the key to breakthrough in the art. SUMMARY

[0006] To solve or partially solve the problems in the related art, the present application provides a battery and an electronic device, which exhibit excellent safety performance, high-temperature cycle performance and low-temperature cycle performance.

[0007] The first aspect of the present application provides a battery, comprising a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode current collector and a negative electrode coating layer arranged on at least one side surface of the negative electrode current collector; the negative electrode coating layer comprises a silicon-based material; The electrolyte comprises a first additive, a second additive, a third additive and a fourth additive; the first additive comprises a fluorosulfonyl amide compound; the second additive comprises an unsaturated carbonate compound; the third additive comprises a lithium salt additive; and the fourth additive comprises a nitrile compound. The battery simultaneously satisfies the following relationships: 0.2≤(A+B+C) / X≤85 Equation 1; 0.1≤D / (B+C)≤2.4 Equation 2; 0.03≤C / A≤1.5 Equation 3; wherein a mass percentage content of the first additive in the electrolyte is A; a mass percentage content of the second additive in the electrolyte is B; a mass percentage content of the third additive in the electrolyte is C; a mass percentage content of the fourth additive in the electrolyte is D; and a mass percentage content of silicon element in the negative electrode coating is X.

[0008] The battery of the first aspect, wherein the battery simultaneously satisfies the following relationships: 0.38≤(A+B+C) / X≤38 Equation 4; 0.13≤D / (B+C)≤1.88 Equation 5; 0.03≤C / A≤1 Equation 6.

[0009] The battery of the first aspect, wherein 3%≤A≤70%; and / or, 0.5%≤B≤20%.

[0010] The battery of the first aspect, wherein 1%≤C≤20%; and / or, 1%≤D≤15%.

[0011] The battery of the first aspect, wherein 1%≤X≤100%.

[0012] The battery of the first aspect, wherein the first additive comprises at least one of 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide, dimethylsulfamoyl fluoride, N,N-diethylsulfamoyl fluoride; and / or, the second additive comprises at least one of vinylene carbonate and / or fluoroethylene carbonate; and / or, the third additive comprises at least one of lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium bis(oxalato)borate; and / or, the fourth additive comprises at least one of 1,3,6-hexanetricarbonitrile, 1,4-dicyanobutane, butanedinitrile, 1,2-bis(cyanoethyloxy)ethane.

[0013] The battery of the first aspect, wherein the first additive is 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide; the second additive is vinylene carbonate; the third additive is lithium bisfluorosulfonylimide; and the fourth additive is 1,3,6-hexanetricarbonitrile.

[0014] The battery of the first aspect, wherein the silicon-based material comprises at least one of silicon, silicon-carbon composite, silicon oxide.

[0015] The battery of the first aspect, wherein the battery further comprises a cathode sheet comprising a cathode active material, the cathode active material comprising one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate; the transition metal lithium oxide has a chemical formula of Li 1+x Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; wherein M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, Zr.

[0016] The second aspect of the present application provides an electronic device comprising the battery of the first aspect.

[0017] The technical solution provided by the present application can include the following beneficial effects: on the one hand, the first additive, the second additive, the third additive and the fourth additive synergistically act: the fluorosulfonylamide compound is preferentially reduced on the surface of the negative electrode to form a rigid SEI film base rich in LiF, providing high mechanical strength and thermal stability, and the sulfonamide group can capture H + and HF to purify the interface environment; the unsaturated carbonate compound forms an elastic SEI outer layer by polymerization of the vinyl group, which is complementary to the rigid LiF layer, enhancing the tolerance of the SEI interface film to the volume expansion of silicon; the lithium salt additive not only provides high bulk phase ionic conductivity, but its decomposition products (such as LiF, Li2S x O y ) are more involved in constructing an interface structure with high ionic conductivity, optimizing the ion transmission channel; the nitrile compound forms a stable CEI film on the surface of the positive electrode through multiple cyano groups, and captures the dissolved transition metal ions through complexation, blocking their destruction of the negative electrode SEI; the four of them synergistically form a "rigid base-elastic buffer-ion transmission-positive electrode protection" all-round interface protection system; on the other hand, by precisely controlling the three core relationships, the performance is synergistically optimized, which not only ensures better effective protection of the silicon material and the positive electrode, but also further improves the ion transmission rate, ultimately significantly improving the safety performance, high-temperature cycle performance and low-temperature cycle performance of the battery.

[0018] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. DETAILED DESCRIPTION

[0019] For the purposes of this application, the application will now be described in detail. Before describing the application in detail, it is to be understood that the application is not limited to the specific embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0020] Where a numerical range is provided, it is understood that every number within that range is also specifically disclosed. Every minimum or maximum numeric limitation given is included in the disclosure whether or not it is explicitly stated to be included in the disclosure. The minimum and maximum of every stated range of values is expressly included in the disclosure.

[0021] Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present application, the preferred methods and materials are now described.

[0022] At present, silicon-based negative electrode materials are considered as one of the most potential negative electrode materials for the next generation of high-energy-density lithium-ion batteries due to their extremely high theoretical specific capacity (about 4200 mAh / g), suitable working voltage and abundant natural reserves. However, silicon materials face severe challenges in practical application. The core problem is that silicon will undergo a huge volume change (expansion rate can reach more than 300%) during charging and discharging, which leads to problems such as active material particle breakage, repeated rupture and regeneration of the solid electrolyte interface film (SEI film), poor electrode structure stability, and seriously affects the cycle performance and safety performance of the battery. In addition, the poor electrical conductivity of silicon materials also limits the performance of the battery at low temperature.

[0023] To address the above challenges, the industry generally attempts to improve the structural stability of silicon negative electrodes through nanocrystallization, compounding and other means, and focuses on optimizing the electrolyte formula to build a stable interface film. In electrolyte optimization, the use of functional additives is key. However, a single additive often has limited functionality and is difficult to cope with the complex failure mechanism of the silicon negative electrode with multiple interfaces and multiple scales. For example, although traditional vinylene carbonate (VC) can form a polymer SEI film, its film layer has insufficient mechanical strength, and excessive use will increase the interface impedance; fluorine-containing sulfamide compounds can form a stable SEI film rich in LiF, but may have a negative impact on low-temperature performance; and LiFSI and other lithium salts can provide high ionic conductivity, but there is a risk of corrosion of the current collector.

[0024] To solve the above problems, the application provides a battery, which comprises a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode current collector and a negative electrode coating arranged on at least one side surface of the negative electrode current collector; the negative electrode coating comprises a silicon-based material; the electrolyte comprises a first additive, a second additive, a third additive and a fourth additive; the first additive comprises a fluorosulfonylamide compound; the second additive comprises an unsaturated carbonate compound; the third additive comprises a lithium salt additive; and the fourth additive comprises a nitrile compound.

[0025] The application does not limit the selection of the negative electrode current collector, which can be selected according to actual needs, for example, a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a foamed nickel, a foamed copper or a composite current collector can be selected. Preferably, the negative electrode current collector comprises a copper foil. The negative electrode coating of the application comprises a negative electrode active material, which comprises a silicon-based material. The silicon-based material of the application is a material comprising silicon elements, and the selection of the silicon-based material is not limited, which can be selected according to actual needs, for example, elemental silicon, silicon-carbon materials, silicon-oxygen materials, etc.

[0026] The fluorosulfonylamide compound of the application refers to an organic compound comprising a fluorine functional group and a sulfonamide functional group (-S(=O)2N-). The unsaturated carbonate compound of the application refers to a compound containing a carbon-carbon unsaturated bond (double bond or triple bond) in addition to a carbonate functional group (-O-CO-O-) in the molecule. The lithium salt additive of the application refers to a compound containing lithium ions. The nitrile compound of the application refers to an organic compound containing a cyano group (-CN).

[0027] The battery of the application simultaneously satisfies the following relationships: 0.2≤(A+B+C) / X≤85 Formula 1; 0.1≤D / (B+C)≤2.4 Formula 2; 0.03≤C / A≤1.5 Formula 3; wherein the mass percentage content of the first additive in the electrolyte is A; the mass percentage content of the second additive in the electrolyte is B; the mass percentage content of the third additive in the electrolyte is C; the mass percentage content of the fourth additive in the electrolyte is D; and the mass percentage content of silicon elements in the negative electrode coating is X.

[0028] The setting of (A+B+C) / X of relationship 1 is to match sufficient interface protection resources for unit silicon content to prevent insufficient interface protection or excessive additives; for example, (A+B+C) / X can be 0.2, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80 or 85, etc. The setting of D / (B+C) of relationship 2 aims to balance the resource allocation of positive electrode protection and negative electrode protection to avoid interface instability on either side; for example, D / (B+C) can be 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2 or 2.4, etc. The setting of C / A of relationship 3 is used to optimize the ion conductivity and structural stability ratio of the interface film; for example, C / A can be 0.03, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4 or 1.5, etc.

[0029] According to the above scheme provided by the application, the battery exhibits excellent safety performance, high-temperature cycle performance and low-temperature cycle performance. The applicant analyzes the principle and believes that the reason is that, on the one hand, the first additive, the second additive, the third additive and the fourth additive synergistically act: the fluorosulfonylamide compound forms a rigid SEI film base rich in LiF on the negative electrode surface by the fluorine functional group and the sulfonamide functional group, providing high mechanical strength and thermal stability, and the sulfonamide group can capture H + and HF to purify the interface environment; the unsaturated carbonate compound forms an elastic SEI outer layer by polymerization of the carbon-carbon unsaturated bond, which is complementary to the rigid LiF layer, enhancing the tolerance of the SEI interface film to the volume expansion of silicon; the lithium salt additive not only provides high bulk ion conductivity, but also its decomposition products (such as LiF, Li2S x O y ) participate in the construction of high ion conductivity interface structure, optimizing the ion transmission channel; the nitrile compound forms a stable CEI film on the positive electrode surface through multiple cyano groups, and captures the dissolved transition metal ions through complexation, blocking their destruction of the negative electrode SEI; the four of them synergistically form a "rigid base-elastic buffer-ion transmission-positive electrode protection" all-round interface protection system; on the other hand, the performance is optimized by precisely controlling the three core relationships, which not only ensures better protection of the silicon material and the positive electrode, but also further improves the ion transmission rate, ultimately making the safety performance, high-temperature cycle performance and low-temperature cycle performance of the battery significantly improved.

[0030] When (A+B+C) / X<0.2, the interface protection is seriously insufficient, the silicon particles are directly exposed to the electrolyte, leading to continuous side reactions, and the cycle performance deteriorates sharply; when (A+B+C) / X>85, the electrolyte additive is seriously excessive, forming an excessively thick interface film, the ion migration impedance increases significantly, leading to the cycle performance of the battery to decline. When D / (B+C)<0.1, the positive electrode protection is insufficient, leading to incomplete CEI film and poor thermal safety, and high-temperature cycle attenuation; when D / (B+C)>2.4, the nitrile compound is excessive, forming an excessively thick CEI film, increasing the kinetic resistance, leading to the cycle performance of the battery to decline. When C / A<0.03, the ion conductivity is seriously insufficient, leading to sharp deterioration of low-temperature performance; when C / A>1.5, the interface structure is unstable and the risk of side reactions increases, leading to cycle performance decline.

[0031] In a specific embodiment, the SEI film of the present application comprises an SEI film bottom layer and an SEI film surface layer arranged in a stack, the components of the SEI film bottom layer comprising LiF and Li2S x O y , and the components of the SEI film surface layer comprising polycarbonate and Li2S x O y .

[0032] In a specific embodiment, the components of the CEI film of the present application comprise LiF, lithium alkoxide and LiN.

[0033] In a specific embodiment, the battery simultaneously satisfies the following relationships: 0.38≤(A+B+C) / X≤38 Equation 4; 0.13≤D / (B+C)≤1.88 Equation 5; 0.03≤C / A≤1 Equation 6.

[0034] For example, (A+B+C) / X can be 0.38, 0.5, 1, 5, 10, 15, 20, 25, 30, 35 or 38, etc.; for example, D / (B+C) can be 0.13, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8 or 1.88, etc.; for example, C / A can be 0.03, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc.

[0035] When the battery simultaneously satisfies the above relationships, the synergistic effect of the four additives is better, the rigidity and elasticity of the SEI film are better, the stability of the CEI film is higher, the protection effect on the negative electrode and the positive electrode is better, and the ion conductivity is greatly improved, thereby significantly improving the high and low temperature cycle performance and thermal shock safety performance of the battery.

[0036] In one specific embodiment, 3%≤A≤70%, for example, A can be 3%, 5%, 10%, 20%, 30%, 40%, 50%, 60% or 70%, etc. When the mass content of the first additive is within the above range, the mechanical strength and thermal stability of the rigid SEI film substrate formed on the negative electrode surface are more optimal, there are less acidic substances in the electrolyte, and there are fewer battery side reactions, thereby further improving the safety performance and high-low temperature cycle performance of the battery. If A is less than 3%, the negative electrode interface protection is insufficient, the LiF film formation is incomplete, and the dendrite inhibition ability and acid capture effect are reduced, resulting in an increase in battery side reactions, which degrades the safety performance and high-low temperature cycle performance of the battery; if A is greater than 70%, the over-thick composite SEI film seriously hinders ion migration, affecting the low-temperature cycle performance of the battery.

[0037] In one specific embodiment, 0.5%≤B≤20%, for example, B can be 0.5%, 1%, 2%, 5%, 10%, 15% or 20%, etc. When the mass percentage content of the unsaturated carbonate compound is within the above range, the SEI film has higher elasticity and is more resistant to volume expansion of the silicon material, avoiding problems such as rupture and pulverization of the negative electrode active layer, thereby ensuring the safety performance and high-low temperature cycle performance of the battery. If B is less than 0.5%, the formation of the elastic SEI layer is insufficient, and the buffering capacity for silicon volume expansion is reduced; if B is greater than 20%, the over-thick polymer layer results in excessive interface impedance, affecting the rate characteristics.

[0038] In one specific embodiment, 1%≤C≤20%, for example, C can be 1%, 2%, 5%, 10%, 15% or 20%, etc. When the mass percentage content of the lithium salt additive is within the above range, the bulk and interface ion conductivity is higher, and the ion transmission channel is more optimal, resulting in higher high-low temperature cycle performance of the battery. If C is less than 1%, the bulk and interface ion conductivity is insufficient; if C is greater than 20%, the side reactions are intensified, which can corrode the current collector and affect the thermal safety.

[0039] In one specific embodiment, 1%≤D≤15%, for example, D can be 1%, 2%, 5%, 10% or 15%. When the mass percentage content of the nitrile compound is within the above range, the stability of the CEI film is more optimal, which can better protect the positive electrode, capture transition metal ions, reduce battery side reactions, and more greatly improve the high-low temperature performance and safety performance of the battery. If D is less than 1%, the CEI film is incomplete, resulting in insufficient positive electrode protection and reduced metal ion capture ability; if D is greater than 15%, the over-thick positive electrode interface film increases polarization, affecting capacity development.

[0040] In one specific embodiment, 1%≤X≤100%, for example, X can be 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc. When the silicon content is within the above range, the silicon-based material can fully play the advantage of high capacity in the battery, while avoiding excessive volume expansion, thereby improving the electrochemical performance of the battery.

[0041] In one specific embodiment, the first additive includes at least one of 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide (compound a-1), dimethylsulfamoyl fluoride (compound a-2), and N,N-diethylsulfamoyl fluoride (compound a-3). When the first additive is selected from the above compounds, the first additive has a more optimal synergistic effect with other additives, so that the SEI film has higher rigidity, better mechanical strength and thermal stability, and can better reduce acidic substances in the electrolyte, thereby improving the safety performance and high-low temperature cycle performance of the battery.

[0042] In one specific embodiment, the second additive includes vinylene carbonate (compound b-1) and / or fluoroethylene carbonate (compound b-2). When the second additive is selected from the above compounds, the second additive can better participate in synergistic effect, further improve the elasticity of the SEI film, and more effectively alleviate the volume expansion of silicon, thereby significantly improving the safety performance and high-low temperature cycle performance of the battery.

[0043] In one specific embodiment, the third additive includes at least one of lithium bisfluorosulfonylimide (compound c-1), lithium bis(trifluoromethanesulfonyl)imide (compound c-2), lithium difluorophosphate (compound c-3), lithium difluoro(oxalato)borate (compound c-4), lithium tetrafluoroborate (compound c-5), and lithium bis(oxalato)borate (compound c-6). When the third additive is selected from the above lithium salts, the lithium ion transmission rate of the battery is higher, and the impedance of the battery is lower, thereby further improving the high-low temperature cycle performance of the battery.

[0044] In one specific embodiment, the fourth additive includes at least one of 1,3,6-hexanetricarbonitrile (compound d-1), 1,4-dicyanobutane (compound d-2), butanedinitrile (compound d-3), and 1,2-bis(cyanoethoxy)ethane (compound d-4). When the fourth additive is selected from the above compounds, the fourth additive can have a more optimal synergistic effect with the first additive, the second additive, and the third additive, so that the stability of the CEI film on the positive electrode surface is more optimal, the positive electrode is better protected, and the SEI film is prevented from being damaged by transition metal ions dissolved from the positive electrode, thereby obtaining a battery with better safety performance and high-low temperature cycle performance.

[0045] In a preferred embodiment, the first additive is 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide; the second additive is vinylene carbonate; the third additive is lithium bisfluorosulfonylimide; and the fourth additive is 1,3,6-hexanetricarbonitrile. These four compounds can better synergize, further improve the stability of SEI film and CEI film, and increase the lithium ion transmission rate, thereby protecting the positive and negative electrodes of the battery, reducing the side reactions of the battery, and further improving the safety performance and high-low temperature cycle performance of the battery.

[0046] In an embodiment, the silicon-based material includes at least one of silicon, silicon-carbon composite, and silicon oxide. When the silicon-based material is selected from the above materials, the silicon-based material can fully exert its high capacity characteristics in the battery, while alleviating the volume expansion problem of the silicon-based material during charging and discharging, thereby ensuring the cycle stability and electrochemical performance of the battery.

[0047] In an embodiment, the electrolyte further includes a solvent, and the solvent includes at least one of vinyl carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Specifically, the above solvent types are selected to dissolve the first additive, the second additive, the third additive, and the fourth additive, thereby preparing an electrolyte with stable performance.

[0048] In an embodiment, the electrolyte further includes a lithium salt, and the lithium salt includes lithium hexafluorophosphate and / or lithium bis(trifluoromethylsulfonyl)imide.

[0049] It should be noted that the preparation method of the electrolyte is not particularly limited in the present application, and those skilled in the art can prepare it into an electrolyte according to conventional technical means, for example, by mixing the raw materials according to the ratio.

[0050] In an embodiment, the negative active material further includes at least one of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O 12 , Li-Al alloy.

[0051] In one embodiment, the negative electrode coating further comprises a negative electrode conductive agent, a negative electrode binder, a thickening agent, and a solvent. The negative electrode conductive agent comprises at least one of natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene, and other carbon materials. The negative electrode binder comprises butadiene rubber and the like. The thickening agent comprises CMC and the like. The solvent comprises deionized water.

[0052] In one embodiment, the battery further comprises a positive electrode sheet comprising a positive electrode current collector and a positive electrode coating disposed on at least one surface of the positive electrode current collector. The positive electrode coating comprises a positive electrode active material, which comprises one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadium phosphate; the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; wherein M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, Zr.

[0053] The type of the positive electrode current collector of the present application is not particularly limited, and it can be any material known to be suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector comprises metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, and carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector is a metal material.

[0054] In one embodiment, the positive electrode coating further comprises a positive electrode conductive agent, a positive electrode binder, and a solvent. The type of the positive electrode conductive agent is not limited in the present application, and any known conductive agent can be used. In some embodiments, the positive electrode conductive agent mentioned in the present application comprises at least one of natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene, and other carbon materials.

[0055] The type of the positive electrode binder is not limited in the present application, and any known positive electrode binder can be used. In some embodiments, the positive electrode binder comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose.

[0056] In the lithium ion battery mentioned in the present application, a separator is usually disposed between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator are not particularly limited, as long as they do not significantly impair the effects of the present application.

[0057] In one embodiment, the separator includes a porous sheet or nonwoven fabric-like substance having excellent liquid retention, and the separator includes a resin or glass fiber separator material including, but not limited to, polyolefin, aramid, polytetrafluoroethylene, polyether sulfone, and the like.

[0058] In one embodiment, the lithium ion battery can include an outer package that can be used to encapsulate the electrode assembly and the electrolyte described above.

[0059] In one embodiment, the outer package of the lithium ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the lithium ion battery can also be a soft package, such as a pouch-type soft package. The soft package can be made of plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, and the like can be listed.

[0060] The shape of the lithium ion battery according to the present application is not particularly limited, and can be cylindrical, square, or any other arbitrary shape.

[0061] The present application also provides an electronic device including the lithium ion battery described above.

[0062] For example, the electronic device described above can include a mobile device (such as a mobile phone, a notebook computer, and the like), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, and the like), an electric train, a ship and a satellite, an energy storage system, and the like, but is not limited thereto.

[0063] The present application is further illustrated by the following examples.

[0064] Example 1 1. Preparation of electrolyte In an environment with a water content of less than 10 ppm, 1M lithium hexafluorophosphate was added to propyl propionate, mixed uniformly, and then an additive (the type and amount of the additive are shown in Table 1) was added to obtain an electrolyte.

[0065] 2. Preparation of positive electrode sheet The positive electrode active material lithium cobaltate, the positive electrode conductive agent acetylene black (Super P), and the polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 97:1.5:1.5, and uniformly dispersed with 1-methyl-2-pyrrolidone (NMP) to prepare a uniform positive electrode slurry. The mixed positive electrode slurry was coated on both sides of an aluminum foil current collector, and then baked, rolled, and cut to obtain a positive electrode sheet.

[0066] 3. Preparation of negative electrode sheet The negative active material artificial graphite, silicon negative electrode, conductive agent acetylene black (Super P), thickening agent CMC and negative electrode binder SBR are mixed uniformly in a mass ratio of 74:20:2:1.2:2.8, and are uniformly dispersed with deionized water to prepare a uniform negative electrode slurry. After the mixed slurry is coated on both sides of the copper foil current collector, baking, rolling, and sheet cutting are performed to obtain a negative electrode sheet.

[0067] 4. Preparation of a lithium ion battery The prepared positive electrode sheet, separator and negative electrode sheet are stacked in order, with the separator between the positive and negative electrode sheets. After winding and tab welding, a bare cell is obtained. The bare cell is placed in an aluminum plastic film, and liquid injection and packaging are performed to obtain a lithium ion battery.

[0068] Examples 2-45, Comparative Examples 1-30 and most of the steps of Example 1 are the same, except that the types and contents of the additives of the electrolyte in Table 1 and the content of silicon in the negative active layer are used.

[0069] Table 1

[0070] Test Example The batteries prepared in the examples and comparative examples are tested for the following properties: 1. Thermal shock test The lithium ion batteries prepared in the above examples and comparative examples are charged at 25°C to the cut-off voltage at a rate of 1C, and the cut-off current is 0.025C. The batteries are transferred to an oven and heated to 150°C at a rate of 5°C / min, and are kept constant for 60 min. If the battery does not catch fire or explode, it is considered to pass. The number of test cells is 20.

[0071] 2. 45°C cycle performance test The lithium ion batteries prepared in the above examples and comparative examples are charged and discharged at 45°C at a rate of 1C / 1C within the cut-off voltage range. The discharge capacity of the first week is counted as C1, and the discharge capacity of the Nth cycle is counted as C2. The cycle capacity retention rate R2 = C2 / C1 is obtained by dividing the Nth week capacity by the first week capacity. The cycle number of the lithium ion battery when the cycle capacity retention rate R2 is 70% is recorded.

[0072] 3. 0°C cycle performance test The lithium ion batteries prepared in each of the above examples and comparative examples were subjected to charge-discharge cycling at 0°C within the charge-discharge cut-off voltage range at a rate of 1C / 1C, the discharge capacity in the first week was counted as Y1, and the discharge capacity in the Nth cycle was counted as Y2; the capacity in the Nth week divided by the capacity in the first week gave the cycle capacity retention rate X2=Y2 / Y1 in the Nth week, and the cycle number of the lithium ion battery when the cycle capacity retention rate X2 was 70% was recorded.

[0073] The test results described above are shown in Table 2.

[0074] Table 2

[0075] As can be seen from the test results in Table 2, the performance tests of Examples 1-45 are overall better than those of Comparative Examples 1-30. As no functional additives were added in Comparative Example 1, the number of thermal shock passes was only 1, the cycle number at 0°C was only 356 cycles, and the cycle number at 45°C was only 345 cycles, and the performance was the worst. Through data comparison, it can be seen that when the synergistic interface protection of the four additives is lacking, the overall performance of the battery is severely insufficient.

[0076] Analysis of the synergistic effect of key parameters: 1. Synergistic verification of the relationship: Relationship 1: Interface protection sufficiency verification of (A+B+C) / X Example 14 (ratio 2.00) showed the best overall performance (thermal shock 19 passes, 0°C cycle 787 cycles, 45°C cycle 796 cycles), proving that the interface protection resources and silicon content were optimally matched at this ratio.

[0077] Comparative Example 26 (ratio 0.05) had a very high silicon content due to a severe lack of total amount of additives, and the interface protection completely failed, with the cycle performance rapidly deteriorating to about 420 cycles.

[0078] Comparative Example 25 (ratio 110) had a severe excess of additives, forming an excessively thick interface film that blocked ion migration, and the cycle performance decreased to about 440 cycles.

[0079] Relationship 2: Positive and negative electrode protection balance verification of D / (B+C) Example 20 (ratio 0.63) achieved excellent thermal safety (18 passes) and long cycle life (0°C cycle 773 cycles, 45°C cycle 785 cycles).

[0080] Comparative Example 28 (ratio 0.03) had poor thermal safety (9 passed) and high-temperature cycle attenuation due to a serious lack of positive electrode protective agent D.

[0081] Comparative Example 27 (ratio 10.00) had reduced cycle performance to about 420 cycles due to excessive positive electrode protective agent, which formed a too-thick CEI film and increased kinetic resistance.

[0082] Equation 3: Interface kinetics and stability trade-off verification of C / A Example 14 (ratio 0.17) achieved a perfect balance of high and low temperature performance and safety.

[0083] Comparative Example 30 (ratio 0.01) had a sharp deterioration in low-temperature performance (only 417 cycles at 0°C) due to a serious lack of ionic conductivity.

[0084] Comparative Example 29 (ratio 6.67) had reduced cycle performance to about 445 cycles due to unstable interface structure and increased risk of side reactions.

[0085] 2. Single additive function verification: First additive (A) content effect: Examples 1-5 show that when A increases from 3% to 70%, the number of thermal shock passes increases from 16 to 17, the 45°C cycle performance increases from 638 cycles to 685 cycles, but the 0°C cycle performance decreases from 657 cycles to 612 cycles. This shows that increasing the fluorosulfamide additive can improve safety and high-temperature performance by forming a LiF-rich SEI film, but excessive amounts will increase interface impedance and worsen low-temperature performance.

[0086] Second additive (B) content effect: Examples 6-11 show that when B increases from 0.5% to 20%, the number of thermal shock passes decreases from 19 to 14, the 0°C cycle performance increases from 648 cycles to 715 cycles, and the 45°C cycle performance increases from 668 cycles to 738 cycles. This shows that vinylene carbonate can effectively improve cycle performance, but excessive amounts will have a negative impact on thermal safety due to the exothermic reaction of reduction.

[0087] Third additive (C) content effect: Examples 12-17 show that when C increases from 1% to 20%, the number of thermal shock passes decreases from 18 to 14, the 0°C cycle performance increases from 618 cycles to 638 cycles, and the 45°C cycle performance increases from 658 cycles to 625 cycles. This shows that LiFSI can improve cycle performance, but excessive amounts can slightly affect thermal safety due to increased side reactions.

[0088] Fourth additive (D) content effect: Examples 18~22 show that when D increases from 1% to 15%, the thermal shock passes from 14 to 20, the 0℃ cycle performance increases from 608 to 668, and the 45℃ cycle performance decreases from 718 to 648. This shows that nitrile compounds can significantly improve thermal safety, but excessive amounts can affect high-temperature cycle performance due to the excessive thickness of the CEI film.

[0089] 3. Matching of silicon content (X) and interface protection resources: Examples 23~28 show that when X increases from 1% to 100%, (A+B+C) / X decreases from 38.00 to 0.38, the thermal shock passes from 16 to 14, and the cycle performance decreases from about 620 to about 600. This verifies the "ABC compensation logic": the increase in silicon content must be synchronized with the increase in interface protection resources, otherwise the performance will decline overall.

[0090] 4. Necessity of component integrity: When any of the core components is missing in Comparative Examples 1-5, the performance is significantly degraded. Comparative Example 1 (all missing) has the worst performance; Comparative Example 2 (only A) has insufficient cycle performance; Comparative Example 3 (only B) has poor thermal safety; Comparative Example 4 (only C) has low overall performance; and Comparative Example 5 (only D) has poor cycle performance. This proves that the four additives are indispensable, and the synergistic effect is crucial.

[0091] When alternative compounds are used in Comparative Examples 21~24, the performance is overall deteriorated: Comparative Example 21 (ordinary sulfonamide) cannot form a LiF-rich SEI film due to the lack of F functional groups; Comparative Example 22 (DTD) forms an interface film with insufficient elasticity; Comparative Example 23 (NaPF6) has low ionic conductivity; and Comparative Example 24 (isocyanate) lacks cyano functional groups, which cannot effectively protect the positive electrode. This highlights the key role of the specific molecular structure of the invention in constructing a gradient interface film.

[0092] 5. Confirmation of the optimal ratio range: Examples 3, 14, 20, etc. are within the preferred range of the core relationship (0.38≤(A+B+C) / X≤38, 0.13≤D / (B+C)≤1.88, 0.03≤C / A≤1), and all show the best performance balance (thermal shock ≥18 passes, 0℃ cycle ≥628 cycles, 45℃ cycle ≥707 cycles). While Comparative Examples 25~30 have some parameters within the ABCD range, the performance is significantly short due to the imbalance of the relationship, further verifying the necessity of the invention to precisely control the synergistic effect through the three relationship formulas.

[0093] In summary, the application successfully constructed a full-range interface protection system of "rigid substrate-elastic buffer-ion transmission-positive electrode protection" by precisely regulating the content ratio of the four additives and the three core relationship formulas. Experimental data fully prove the close coupling characteristics of the ABCDX system: the absence or imbalance of any component will cause a significant performance decline. Only when all parameters are in the optimal range and work together can the high-silicon negative electrode battery achieve the best balance in high safety and high-low temperature cycle performance.

[0094] Embodiments of the application have been described above, the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles, practical applications, or improvements to the technology in the market of the embodiments, or to enable other ordinary skilled in the art to understand the embodiments disclosed herein.

Claims

1. A battery, characterized by, The battery comprises a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode current collector and a negative electrode coating layer arranged on at least one side surface of the negative electrode current collector; the negative electrode coating layer comprises a silicon-based material; The electrolyte comprises a first additive, a second additive, a third additive and a fourth additive; the first additive comprises a fluorosulfamide compound; the second additive comprises an unsaturated carbonate compound; the third additive comprises a lithium salt additive; and the fourth additive comprises a nitrile compound; The battery satisfies the following relationships simultaneously: 0.2≤(A+B+C) / X≤85 Formula 1; 0.1≤D / (B+C)≤2.4 Formula 2; 0.03≤C / A≤1.5 Formula 3; wherein the mass percentage content of the first additive in the electrolyte is A; the mass percentage content of the second additive in the electrolyte is B; the mass percentage content of the third additive in the electrolyte is C; the mass percentage content of the fourth additive in the electrolyte is D; and the mass percentage content of silicon in the negative electrode coating layer is X.

2. The battery of claim 1, wherein, The battery satisfies the following relationships simultaneously: 0.38≤(A+B+C) / X≤38 Formula 4; 0.13≤D / (B+C)≤1.88 Formula 5; 0.03≤C / A≤1 Formula 6.

3. The battery of claim 1, wherein, 3%≤A≤70%; and / or, 0.5%≤B≤20%。 4. The battery of claim 1, wherein, 1%≤C≤20%; and / or, 1%≤D≤15%。 5. The battery of claim 1, wherein, 1%≤X≤100%。 6. The battery according to any one of claims 1 to 3, characterized in that, The first additive comprises at least one of 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide, dimethylsulfamoyl fluoride, and N,N-diethylsulfamoyl fluoride; and / or, The second additive comprises vinylene carbonate and / or fluoroethylene carbonate; and / or, The third additive comprises at least one of lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate; and / or, The fourth additive comprises at least one of 1,3,6-hexanetricarbonitrile, 1,4-dicyanobutane, butanedinitrile, and 1,2-bis(cyanoethyloxy)ethane.

7. The battery of claim 6, wherein, The first additive is 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide; the second additive is vinylene carbonate; the third additive is lithium bisfluorosulfonimide; and the fourth additive is 1,3,6-hexanetricarbonitrile.

8. The battery of claim 1, wherein, The silicon-based material comprises at least one of silicon, a silicon-carbon composite, and a silicon oxide compound.

9. The battery of claim 1, wherein, The battery further comprises a positive electrode sheet comprising a positive electrode active material, the positive electrode active material comprising one or more of a transition metal lithium oxide, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, lithium vanadium phosphate; the transition metal lithium oxide has a chemical formula of Li 1+x Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; wherein M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, Zr.

10. An electronic device, comprising: The battery comprises the battery according to any one of claims 1-9.

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