Electrolyte additive, electrolyte and battery

Abstract

Provided in the present application are an electrolyte additive, an electrolyte and a battery. The electrolyte additive comprises a first additive, a second additive and a third additive; the first additive comprises a compound represented by formula 1, R1 being selected from a C atom or an O atom, R2 being selected from formula 5 or formula 6, R3 being selected from methylene, formula 7 and formula 8, R4 being selected from formula 9 or formula 10, and R2, R3 and R4 at least comprising one sulfur atom; the second additive comprises at least one of a compound represented by formula 2 and a compound represented by formula 3, X comprising a P atom or a B atom; the third additive comprises a compound represented by formula 4: R-N=C=O formula 4, R comprising at least one of an alkyl group, an O=C=N-substituted alkyl group, a cycloalkyl group, an O=C=N-substituted cycloalkyl group, an aryl group and an O=C=N-substituted aryl group. Thus, the present application can form on electrode surfaces stable and low-impedance interfacial films, thereby reducing the impedance of batteries and the gas production of the batteries, and improving the cycle performance of the batteries.

Description

Electrolyte additive, electrolyte and battery

[0001] Priority information

[0002] This application claims priority to and the benefit of Chinese Patent Application No. 202410720189.5, filed on June 5, 2024, and is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the field of batteries, in particular, to an electrolyte additive, an electrolyte and a battery. BACKGROUND

[0004] In recent years, secondary batteries have been widely used in portable electronic products, electric vehicles and energy storage fields. However, with the increasing market performance requirements, the electrolyte under high temperature conditions will accelerate the reaction of the electrolyte on the surface of the electrode material, thereby causing the electrolyte to decompose and generate gas. The generated gas can cause the battery to swell and burst, which can easily cause the battery to rupture and the electrolyte to leak, thereby posing a great safety hazard. The electrolyte in the related art also has problems such as slow ion kinetics, slow solvation and desolvation process of ions, and reduced ion deintercalation rate. The above problems can cause the concentration polarization in the battery to increase, the internal impedance of the battery to increase, and the cycle life of the battery to decrease. SUMMARY

[0005] The present application aims to at least partially solve one of the technical problems in the related art.

[0006] The first aspect of the present application provides an electrolyte additive, comprising a first additive, a second additive and a third additive, wherein the first additive comprises a compound represented by Formula 1: R1 is selected from a C atom or an O atom, R2 is selected from R3 is selected from a methylene group, R4 is selected from and at least one of R2, R3 and R4 contains a sulfur atom; the second additive comprises at least one of a compound represented by Formula 2 and a compound represented by Formula 3: X comprises a P atom or a B atom; the third additive comprises a compound represented by Formula 4: R-N=C=O Formula 4, R comprises at least one of an alkyl group, an O=C=N-substituted alkyl group, a cycloalkyl group, an O=C=N-substituted cycloalkyl group, an aryl group and an O=C=N-substituted aryl group. In this way, a stable and low-impedance interface film can be formed on the surface of the electrode, the impedance of the battery can be reduced, the gas production of the battery can be reduced, and the cycle performance of the battery can be improved.

[0007] According to some embodiments of the present application, R includes at least one of an alkyl group of 1-10 carbon atoms, an O=C=N-substituted alkyl group of 1-10 carbon atoms, a cycloalkyl group of 1-10 carbon atoms, an O=C=N-substituted cycloalkyl group of 1-10 carbon atoms, an aryl group of 6-10 carbon atoms, and an O=C=N-substituted aryl group of 6-10 carbon atoms.

[0008] According to some embodiments of the present application, the mass ratio of the first additive, the second additive, and the third additive in the electrolyte additive is 1:(0.01-10):(0.01-10). In this way, a stable and low-impedance interface film is formed on the electrode surface, gas production of the battery is reduced, water or acid generated by reaction in the electrolyte is removed, and the stability of the electrode structure is improved.

[0009] According to some embodiments of the present application, the first additive includes at least one of

[0010] According to some embodiments of the present application, the second additive includes at least one of In this way, a stable and high-conductivity interface film is formed on the electrode surface, the transmission capacity of the electrode for electric charge is improved, and the impedance of the battery is reduced.

[0011] According to some embodiments of the present application, the third additive includes at least one of In this way, while water and acid are removed, the third additive of the above-mentioned type can be polymerized on the electrode surface to form a polymer long chain, and then a stable and low-impedance interface film is formed to reduce the internal resistance of the battery.

[0012] According to some embodiments of the present application, the electrolyte additive further includes a fourth additive, and the fourth additive includes at least one of vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, 1,3-propane sultone, and polystyrene. In this way, the fourth additive cooperates with the first additive, the second additive, and the third additive to decompose in advance at the initial stage of battery formation, to form an interface film through carbon chain ring opening, to improve the stability of the interface film, to improve the wettability of the electrolyte, and thus to improve the cycle performance of the battery.

[0013] According to some embodiments of the present application, the mass ratio of the first additive, the second additive, the third additive, and the fourth additive in the electrolyte additive is 1:(0.01-10):(0.01-10):(0.005-100).

[0014] ​The second aspect of the present application provides an electrolyte, comprising the electrolyte additive provided by the first aspect of the present application.

[0015] According to some embodiments of the present application, the mass percentage of the first additive is 0.1%-5% based on the total mass of the electrolyte. Thus, a low-impedance interface film is formed on the electrode surface, reducing the internal resistance of the battery, while reducing the contact between the electrolyte solvent and the electrode, reducing the probability of electrolyte solvent decomposition, and reducing battery gas production.

[0016] According to some embodiments of the present application, the mass percentage of the second additive is 0.1%-5% based on the total mass of the electrolyte. Thus, a low-impedance interface film is formed on the electrode surface, reducing the internal resistance of the battery.

[0017] According to some embodiments of the present application, the mass percentage of the third additive is 0.1%-5% based on the total mass of the electrolyte. Thus, while water and acid are inhibited, a stable, low-impedance interface film is formed, reducing the internal resistance of the battery.

[0018] According to some embodiments of the present application, the electrolyte further comprises a fourth additive, and the mass percentage of the fourth additive is 0.5%-5% based on the total mass of the electrolyte. Thus, the fourth additive synergistically acts with the first additive, the second additive, and the third additive to decompose early and form an interface film by carbon chain ring opening at the initial stage of battery formation, improve the stability of the interface film, improve the wettability of the electrolyte, and thus improve the cycle performance of the battery.

[0019] According to some embodiments of the present application, the electrolyte further comprises an electrolyte salt, and the mass percentage of the electrolyte salt is 12%-18% based on the total mass of the electrolyte.

[0020] The third aspect of the present application provides a battery comprising the electrolyte additive provided by the first aspect of the present application or the electrolyte provided by the second aspect of the present application.

[0021] According to some embodiments of the present application, the battery comprises a positive electrode sheet and a negative electrode sheet, wherein the battery is a lithium ion battery, the positive electrode active material of the positive electrode sheet comprises LiFe 1-x’ M’ x’ PO4, LiMn 2-y’ M y’ O4, and LiNi x Co y Mn z M 1-x-y-zone or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M includes one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0≤x’<1, 0≤y’≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1; and / or the battery is a sodium ion battery, the positive electrode active material of the positive electrode plate includes Na c P d (W a O b )Z e wherein P includes a transition metal element, W includes at least one of phosphorus, sulfur, silicon, tungsten, z includes F atoms, 0≤c≤10, 0≤d≤5, 0≤a≤10, 0≤b≤10, 0≤e≤5; and / or the negative electrode active material of the negative electrode plate includes at least one of soft carbon, hard carbon, silicon-based material, tin-based material. DETAILED DESCRIPTION

[0022] Embodiments of the present application are described in detail below. The embodiments described below are exemplary only, and are not to be construed as limiting the present application. Unless otherwise defined, scientific and technical terms used in the embodiments have the same meaning as commonly understood by one of ordinary skill in the art to which the application pertains. Unless otherwise indicated, the techniques or conditions described herein are those currently used or otherwise described in the literature. Unless otherwise indicated, all reagents or instruments are commercially available and are used according to the manufacturer’s instructions.

[0023] The first aspect of the present application provides an electrolyte additive, the electrolyte additive comprising a first additive, a second additive and a third additive.

[0024] The first additive comprises a compound represented by Formula 1: R1 is selected from a C atom or an O atom, and R2 is selected from R3 is selected from a methylene group, R4 is selected from and at least one of R2, R3 and R4 contains a sulfur atom.

[0025] The second additive comprises at least one of a compound represented by Formula 2 and a compound represented by Formula 3:

[0026] X includes a P atom or a B atom.

[0027] The third additive includes a compound shown in Formula 4: R-N=C=O Formula 4, R includes at least one of alkyl, O=C=N-substituted alkyl, cycloalkyl, O=C=N-substituted cycloalkyl, aryl, O=C=N-substituted aryl.

[0028] Therefore, a stable and low-impedance interface film can be formed on the electrode surface, the transmission rate of active metal ions is improved, the impedance of the battery is reduced, the gas production of the battery is reduced, and the rate capability and cycle performance of the battery are improved.

[0029] The principle of the application capable of achieving the above beneficial effects is described in detail as follows:

[0030] The electrolyte additive provided in the application includes a first additive, a second additive and a third additive. The first additive has a ring structure of ethylene carbonate (EC) and vinyl sulfate (DTD), and has a higher HOMO energy and a lower LUMO energy than the carbonate solvent, so that the first additive can be preferentially subjected to a redox polymerization reaction at the positive and negative electrodes to form an interface film (CEI film of the positive electrode and SEI film of the negative electrode) on the electrode surface. The interface film has good ionic conductivity, can improve the transmission rate of active metal ions, and further reduce the internal resistance of the battery. In addition, the interface film formed on the electrode surface can also reduce the probability of contact between the electrolyte and the electrode (positive and negative electrodes), thereby reducing the risk of catalytic decomposition of the electrolyte to produce gas. At the same time, in order to prevent the interface film from continuously thickening and affecting the transmission of active metal ions as the charging and discharging proceeds, the second additive is introduced. The product after decomposition of the second additive and the first additive form an interface film on the electrode surface, so that the interface film formed on the electrode surface contains trimethylsiloxyalkyl (Me3-Si-O-R), the interface film formed thereby has more pores and better conductivity, which can improve the transmission rate of active metal ions and further reduce the internal resistance of the battery. At the same time, the interface film can also reduce the adhesion of organic matter in the electrolyte to the electrode surface to form long-chain substances, reduce the steric effect caused by the excessive length of the carbon chain on the transmission of active metal ions, and further reduce the SEI internal resistance of the battery. However, the second additive includes a leaving group (residue of acid or alcohol), which can react with trace water or acid in the electrolyte to generate acid, affecting the stability of the electrolyte. Therefore, the third additive is introduced. The isocyanate in the third additive can react with water, alcohol and acid to remove water and suppress acid, and can also inhibit the hydrolysis of lithium salt and the gas production of the battery. At the same time, the isocyanate can also polymerize on the electrode surface to generate a polyamide group substance, participate in the formation of the interface film, and improve the stability of the interface film while reducing the impedance of the interface film, thereby improving the cycle performance of the battery. The use of the second additive and the third additive together can also avoid the excessive reaction rate of the water removal reaction, and ensure the smooth operation of the battery.

[0031] According to some embodiments of the present application, R comprises at least one of an alkyl group of 1-10 carbon atoms, an O=C=N-substituted alkyl group of 1-10 carbon atoms, a cycloalkyl group of 1-10 carbon atoms, an O=C=N-substituted cycloalkyl group of 1-10 carbon atoms, an aryl group of 6-10 carbon atoms, an O=C=N-substituted aryl group of 6-10 carbon atoms.

[0032] According to some embodiments of the present application, the first additive comprises at least one of Thereby, the first additive of the above-mentioned kind can preferentially undergo a polymerization reaction at the positive and negative electrodes in preference to the solvent to form an interface film (CEI film for the positive electrode and SEI film for the negative electrode) on the electrode surface, and the interface film formed has a better ionic conductivity, which can improve the transmission rate of active metal ions, thereby reducing the internal resistance of the battery. In addition, the interface film formed on the electrode surface can also reduce the probability of contact between the electrolyte and the electrode (positive and negative electrodes), thereby reducing the risk of catalytic decomposition of the electrolyte to produce gas.

[0033] According to some embodiments of the present application, the second additive comprises at least one of Thereby, the second additive of the above-mentioned kind can participate in the formation of a low-impedance interface film on the electrode surface after decomposition, and the decomposition product and the first additive together form an interface film on the electrode surface, forming an interface film containing trimethylsiloxy groups (Me3-Si-O-R) on the electrode surface, and the interface film formed has more pores and better conductivity, which can improve the transmission rate of active metal ions, thereby reducing the internal resistance of the battery. At the same time, the interface film can also reduce the adhesion of organic matter in the electrolyte to the electrode surface to form long-chain substances, reduce the steric effect of excessively long carbon chains on the transmission of active metal ions, and further improve the internal resistance of the battery.

[0034] According to some embodiments of the present application, the third additive comprises at least one of Thereby, the third additive of the above-mentioned kind can remove water or acid in the electrolyte, reduce the impact on the electrode structure, and also generate a polymer long chain on the electrode surface to participate in the formation of the interface film, thereby improving the stability of the interface film, reducing the impedance of the interface film, and further reducing the internal resistance of the battery, improving the rate performance and cycle performance of the battery.

[0035] According to some embodiments of the present application, the mass ratio of the first additive, the second additive, and the third additive in the electrolyte additive is 1:(0.01-10):(0.01-10), for example, can be 1:0.05:0.05, 1:1:1, 1:1:5, 1:1:10, 1:5:1, 1:10:1, etc., or can be a range composed of any of the above values. Thus, by making the mass ratio of the first additive, the second additive, and the third additive in the above range, the synergistic effect between the first additive, the second additive, and the third additive can be better exerted, a stable and low-resistance interface film is formed on the electrode surface, the transmission rate of active metal ions is improved, the internal resistance of the battery is reduced, the gas production of the battery is reduced, and the rate performance and cycle performance of the battery are improved.

[0036] According to some embodiments of the present application, the electrolyte additive can further include a fourth additive, and the fourth additive includes at least one of vinylene carbonate, fluoroethylene carbonate (FEC), ethylene sulfate, 1,3-propane sultone, and polystyrene (PS). Thus, the fourth additive synergistically acts with the first additive, the second additive, and the third additive, decomposes in advance at the initial stage of battery formation, and its decomposition product can participate in the formation of the interface film, thereby improving the electrical conductivity and stability of the interface film, and thus improving the cycle performance of the battery.

[0037] According to some embodiments of the present application, the mass ratio of the first additive, the second additive, the third additive, and the fourth additive in the electrolyte additive is 1:(0.01-10):(0.01-10):(0.005-100).

[0038] The second aspect of the present application provides an electrolyte including the electrolyte additive provided by the first aspect of the present application. Thus, the electrolyte has all the features and advantages of the electrolyte additive described above, which will not be repeated here. In general, at least has the advantages of reducing the internal resistance of the battery and reducing the gas production of the battery.

[0039] According to some embodiments of the present application, the mass percentage of the first additive based on the total mass of the electrolyte can be 0.1%-5%, for example, 0.1%, 1%, 2%, 3%, 4% or 5%, or a range consisting of any of the above values. In this way, by making the content of the first additive in the above range, the first additive can be preferentially formed into a film on the electrode surface, and the interface film formed by the product of the decomposition of the first additive has better ionic conductivity, which can improve the transmission rate of active metal ions, thereby reducing the internal resistance of the battery. In addition, the interface film formed on the electrode surface can also reduce the probability of contact between the electrolyte and the electrode (positive and negative electrodes), thereby reducing the risk of catalytic decomposition of the electrolyte to produce gas. According to some specific embodiments of the present application, the mass percentage of the first additive based on the total mass of the electrolyte can be 0.1%-0.5%.

[0040] According to some embodiments of the present application, the mass percentage of the second additive based on the total mass of the electrolyte is 0.1%-5%, for example, 0.1%, 1%, 2%, 3%, 4% or 5%, or a range consisting of any of the above values. In this way, by making the content of the second additive in the above range, an interface film with more pores and better conductivity is formed on the electrode surface, thereby improving the transmission rate of active metal ions and reducing the internal resistance of the battery. According to some specific embodiments of the present application, the mass percentage of the second additive based on the total mass of the electrolyte can be 0.1%-0.5%.

[0041] According to some embodiments of the present application, the mass percentage of the third additive based on the total mass of the electrolyte is 0.1%-5%, for example, 0.1%, 1%, 2%, 3%, 4% or 5%, or a range consisting of any of the above values. In this way, by making the content of the third additive in the above range, water or acid in the electrolyte can be removed, reducing the impact on the electrode structure, and at the same time, a polymer long chain can be generated on the electrode surface to participate in the formation of the interface film, thereby improving the stability of the interface film, reducing the impedance of the interface film, and further reducing the internal resistance of the battery and improving the rate performance and cycle performance of the battery. According to some specific embodiments of the present application, the mass percentage of the third additive based on the total mass of the electrolyte can be 0.1%-0.5%.

[0042] According to some embodiments of the present application, the electrolyte can further include a fourth additive, the mass percentage of the fourth additive in the total mass of the electrolyte being 0.5%-5%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, or a range formed by any of the above values. Thus, the fourth additive cooperates with the first additive, the second additive, and the third additive to decompose and participate in the formation of the interface film at the initial stage of battery formation, thereby improving the conductivity and stability of the interface film and the cycle performance of the battery.

[0043] According to some embodiments of the present application, the electrolyte further includes an electrolyte salt, the mass percentage of the electrolyte salt in the total mass of the electrolyte being 12%-18%. For example, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or a range formed by any of the above values. Thus, the electrolyte can have both high ionic conductivity and low cost.

[0044] For example, when the battery is a lithium ion battery, the electrolyte salt can include at least one of lithium hexafluorophosphate and lithium bisfluorosulfonylimide.

[0045] For example, when the battery is a sodium ion battery, the electrolyte salt can include at least one of sodium hexafluorophosphate and sodium bisfluorosulfonylimide.

[0046] According to some embodiments of the present application, the electrolyte further includes a solvent, the solvent including at least one of a carbonate compound with 3-6 carbon atoms, a carboxylic ester compound with 3-8 carbon atoms, a sulfone compound, and an ether compound. The solvent in the electrolyte is an important carrier for ion transmission, and can have high ionic conductivity after the electrolyte salt is dissolved, thereby improving the cycle life, charge-discharge rate, high-temperature performance, low-temperature performance, and energy density of the battery by selecting the above-mentioned solvent.

[0047] According to some embodiments of the present application, the carbonate compound with 3-6 carbon atoms includes at least one of ethylene carbonate (EC), propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate (EMC), diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0048] According to some embodiments of the present application, the carboxylic ester compound with 3-8 carbon atoms includes at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, and propyl propionate.

[0049] According to some embodiments of the present application, the sulfone compound includes sulfolane.

[0050] According to some embodiments of this application, the ether compound includes at least one of triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether.

[0051] A third aspect of this application provides a battery comprising the electrolyte provided in the second aspect of this application. Therefore, this battery possesses all the features and advantages of the aforementioned electrolyte, which will not be repeated here. In general, it has at least the advantages of low internal resistance and low gas production.

[0052] According to some specific embodiments of this application, the battery may be a lithium-ion battery or a sodium-ion battery.

[0053] According to some specific embodiments of this application, when the battery is a lithium-ion battery, the positive electrode active material may include LiFe. 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z One or more of O2, wherein M' includes one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and M includes one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0054] According to some specific embodiments of this application, when the battery is a lithium-ion battery, the positive electrode active material may further include one or more of sulfides, selenides, and halides.

[0055] As an example, the positive electrode active material may include LiCoO2, LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al0.3 one or more of O2.

[0056] According to some embodiments of the application, when the battery is a sodium-ion battery, the positive active material comprises Na c P d (W a O b )Z e , wherein P comprises a transition metal element, W comprises at least one of phosphorus, sulfur, silicon, tungsten, z comprises F atoms, 0≤c≤10, 0≤d≤5, 0≤a≤10, 0≤b≤10, 0≤e≤5.

[0057] As an example, the positive active material comprises at least one of NaFePO4, Na2FeP2O7, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, Na2Fe(SO4)2.

[0058] According to some embodiments of the application, when the battery is a sodium-ion battery, the positive active material comprises at least one of overplated metal oxides, overplated metal sulfides, phosphorus-based materials, titanate materials, Prussian blue-based materials.

[0059] Generally, a battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and mainly plays a role of preventing short circuit between the positive electrode and the negative electrode, while allowing ions to pass through.

[0060] In some embodiments of the application, the positive current collector can comprise a metal foil or a composite positive current collector. For example, the metal foil can be an aluminum foil. The composite positive current collector can comprise a polymer material base layer and a metal layer formed on at least one side surface of the polymer material base layer, for example, the composite negative current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material base material (such as a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. base material).

[0061] In some embodiments of the application, the positive active material layer can also optionally comprise a conductive agent. As an example, the conductive agent can comprise at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0062] In some embodiments of the present application, the positive electrode active material layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0063] In some embodiments of the present application, the positive electrode tab can be prepared by dispersing the above-described components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, and the binder, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector, and then performing processes such as drying, cold pressing, and the like.

[0064] The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material.

[0065] In some embodiments of the present application, the negative electrode current collector can employ a metal foil or a composite current collector. As a metal foil, for example, an aluminum or copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material base layer such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.

[0066] In some embodiments of the present application, the negative electrode active material can employ a negative electrode active material known in the art for use in a battery. As an example, the negative electrode active material can include at least one of soft carbon, hard carbon, a silicon-based material, a tin-based material, etc., the soft carbon including graphite. The silicon-based material can include at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can include at least one of elemental tin, a tin oxide compound, and a tin alloy.

[0067] In some embodiments of the present application, the negative electrode active material layer can further optionally include a binder. The binder can include at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0068] In some embodiments of the present application, the negative active material layer can also optionally include a conductive agent. The conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0069] In some embodiments of the present application, the negative active material layer can also optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0070] In some embodiments of the present application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after processes such as drying, cold pressing, and the like, the negative electrode sheet can be obtained.

[0071] The present application does not have a particular limitation on the type of the separator film, and any known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0072] In some embodiments of the present application, the material of the separator film can include one or more of polyolefin, aromatic polyamide, polytetrafluoroethylene, polyether sulfone. Further, the separator film includes one or both of polyethylene and polypropylene. In addition, the separator film can be obtained by sequentially stacking multiple layers of materials, for example, the separator film includes a polypropylene layer, a polyethylene layer, and a polypropylene layer sequentially stacked.

[0073] In some embodiments of the present application, the thickness of the separator film can be 9 μm-12 μm, for example, 9 μm, 10 μm, 11 μm, 12 μm, and the like.

[0074] Embodiments of the present application are described in detail below. The embodiments described below are exemplary and are intended to explain the present application, and should not be understood as a limitation of the present application. If a specific technique or condition is not specified in the embodiments, the technique or condition described in the literature in the art or according to the product specification is used. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained on the market.

[0075] Example 1

[0076] 1. Electrolyte preparation: EC and EMC were mixed in a mass ratio of 3:7, electrolyte salt, first additive, second additive, third additive, fourth additive were added, and after mixing uniformly, the electrolyte was obtained, the types and contents of the first additive, the second additive, the third additive, and the fourth additive are shown in Table 1, the electrolyte salt is LiPF6 and LiFSI, the mass ratio of LiPF6 is 10% based on the total mass of the solvent, and the mass ratio of LiFSI is 2%.

[0077] 2. Positive electrode tab preparation: LiFeP04 positive electrode material, conductive agent Super P (conductive carbon black), carbon nanotube, adhesive PVDF (polyvinylidene fluoride) were mixed uniformly at a mass ratio of 94.5:2.5:0.5:2.5, and then vacuum stirred until a certain viscosity and uniform fluidity were obtained. Then the slurry was uniformly coated on both sides of the aluminum foil, and then sequentially dried at 85°C, cold pressed, trimmed, cut, striped, vacuum dried at 85°C for 10 hours, and then welded with tabs to obtain a positive electrode tab with a surface density of 33 mg / cm 2 .

[0078] 3. Negative electrode tab preparation: hard carbon negative electrode material, conductive agent Super P (conductive carbon black), thickening agent CMC-Na (sodium carboxymethyl cellulose), adhesive SBR (styrene-butadiene rubber emulsion) were mixed at a mass ratio of 95:1.5:2.0:1.5 to form a uniform slurry, which was coated on both sides of the aluminum foil, then dried at 85°C, then cold pressed, trimmed, cut, striped, and finally vacuum dried at 85°C for 12 hours, and then welded with tabs to obtain a negative electrode tab with a surface density of 14.2 mg / cm 2 .

[0079] 4. Separator: A porous polyethylene film with a thickness of 9 μm was used as the base material, and a 2 μm adhesive coating was applied to both sides of the base material.

[0080] 5. Preparation of lithium ion battery:

[0081] The above positive electrode tab, separator and negative electrode tab were sequentially stacked and then wound to form a bare cell with a theoretical capacity of 1000 mAh. The bare cell was placed in an outer packaging aluminum foil and vacuum baked at 75°C for 10 hours, and then the above electrolyte was injected. After vacuum packaging, standing, formation, aging, and capacity distribution processes, the lithium ion battery was completed.

[0082] The preparation method of the lithium ion battery in Examples 2-35 and Comparative Examples 1-10 was the same as that in Example 1, and the differences are shown in Table 1.

[0083] The preparation method of the battery in Example 27 was the same as that in Example 19, except that the positive electrode active material was Na4Fe3(PO4)2(P2O7) (abbreviated as NFPP), and the electrolyte salt in the electrolyte was NaPF6 and NaFSI, respectively.

[0084] In Example 35, the positive electrode active material was Li(NiCoMn)O2.

[0085] Table 1

[0086] Performance test

[0087] 1. Cycle capacity retention at 25℃

[0088] Capacity retention test at 25℃: The sodium-ion battery was rested for 4h at ambient temperature of 25℃, then the battery was tested for 400 cycles of charge-discharge at 1.0C current, the test voltage window was 1.5V-3.6V, the discharge capacity of the 1st cycle was recorded as C1, the discharge capacity of the 400th cycle was recorded as C400. 400 The capacity retention of 400 cycles at 25℃ was recorded as η1 = C400 / C1*100%. 400

[0089] 2. Thickness expansion rate test at 60℃ for 20 days

[0090] Thickness expansion rate test at 60℃ for 20 days: The thickness of the battery before storage was measured by a flat plate thickness gauge and recorded as d0, after 20 days of storage at 60℃, the thickness of the battery was measured while hot and recorded as d1, the expansion rate of the high-temperature storage battery at 60℃ for 20 days was recorded as η2 = (d1-d0) / d0*100%.

[0091] 3. Capacity retention test at 60℃ for 20 days

[0092] Capacity retention test at 60℃ for 20 days: The battery was charged at 1.0C constant current and constant voltage to 3.6V at ambient temperature of 25℃, then discharged at 1.0C constant current to 1.5V, the discharge capacity was recorded as C0, then the battery was transferred to 60℃ for 20 days, then discharged at 1.0C constant current to 1.5V, the high-temperature storage capacity retention rate was recorded as η3 = C1 / C0*100%.

[0093] 4. Battery direct current resistance (DCR) test

[0094] ​DCR test before storage: at an ambient temperature of 25℃, the battery is charged at 1.0C to 3.6V, 3.6V to the cut-off current 0.05C, then the battery is rested for 30min, then discharged at 1.0C for 30min (adjust to 50% SOC), record the end voltage V1, after resting for 1h, then discharged at 2.0C for 10s, record the end voltage V2, DCR1 before storage = (V1-V2) / (2.0C-1.0C); DCR test after 20 days of storage at 60℃: at an ambient temperature of 25℃, the battery after storage is charged at 1.0C to 3.6V, 3.6V to the cut-off current 0.05C, then the battery is rested for 30min, then discharged at 1.0C for 30min (adjust to 50% SOC), record the end voltage V3, after resting for 1h, then discharged at 2.0C for 10s, record the end voltage V4, DCR2 before storage = (V3-V4) / (2.0C-1.0C); the growth rate of DCR η4 = (DCR2-DCR1) / DCR1*100%.

[0095] The test results of the batteries in Examples 1-35 and Comparative Examples 1-10 are shown in Table 2.

[0096] Table 2

[0097] Conclusion: As can be seen from Examples 1-35 and Comparative Examples 1-10, by adding the first additive, the second additive and the third additive in the electrolyte at the same time, the cycle capacity retention rate of the battery can be improved, the thickness expansion rate of the battery can be reduced, and the internal resistance of the battery can be reduced, which shows that the first additive, the second additive and the third additive contained in the electrolyte at the same time can improve the rate performance and cycle performance of the battery.

[0098] As can be seen from Examples 1-7, by adjusting the content of the first additive, the ionic conductivity of the interface film formed can be improved, the probability of the electrode contacting with the electrolyte can be reduced, and the risk of the electrolyte being catalytically decomposed to produce gas can be reduced, so that the cycle capacity retention rate of the battery can be improved, the thickness expansion rate of the battery can be reduced, and the internal resistance of the battery can be reduced,

[0099] As can be seen from Examples 1, 2, 8-12, by adjusting the content of the second additive, an interface film with more pores and better conductivity can be formed on the surface of the electrode, so that the internal resistance of the battery can be reduced, and the cycle capacity retention rate of the battery can be improved.

[0100] As can be seen from Example 1, Example 2 and Example 13 to Example 17, by adjusting the content of the third additive, the stability of the interfacial film can be improved, and the impedance of the interfacial film can be reduced, thereby improving the rate performance and cycle performance of the battery.

[0101] As can be seen from Example 18 to Example 20, by simultaneously adding the first additive, the second additive, the third additive and the fourth additive in the electrolyte, the rate performance and cycle performance of the battery can be further improved.

[0102] As can be seen from Example 32 to Example 34, the first additive in the electrolyte can include two kinds, the second additive can include two kinds, and the third additive can include two kinds, which can also have the effect of improving the rate performance and cycle performance of the battery.

[0103] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. An electrolyte additive characterized in that, comprising a first additive, a second additive and a third additive, wherein, The first additive includes a compound represented by Formula 1: Formula 1, R1is selected from a C atom or an O atom, R2is selected from R3is selected from methylene, R4is selected from and at least one of R2, R3 and R4 contains a sulfur atom; the second additive comprises at least one of a compound shown in formula 2, a compound shown in formula 3: X comprises a P atom or a B atom; the third additive comprises a compound shown in formula 4: R-N=C=O formula 4, R comprises at least one of an alkyl group with 1-10 carbon atoms, an alkyl group with 1-10 carbon atoms substituted by O=C=N-, a cycloalkyl group with 1-10 carbon atoms, a cycloalkyl group with 1-10 carbon atoms substituted by O=C=N-, an aryl group with 6-10 carbon atoms, an aryl group with 6-10 carbon atoms substituted by O=C=N-.

2. The electrolyte additive according to claim 1, characterized in that, R comprises at least one of an alkyl group with 1-10 carbon atoms, an alkyl group with 1-10 carbon atoms substituted by O=C=N-, a cycloalkyl group with 1-10 carbon atoms, a cycloalkyl group with 1-10 carbon atoms substituted by O=C=N-, an aryl group with 6-10 carbon atoms, an aryl group with 6-10 carbon atoms substituted by O=C=N-.

3. The electrolyte additive according to claim 1 or 2, characterized in that, a mass ratio of the first additive, the second additive, the third additive in the electrolyte additive is 1:(0.01-10):(0.01-10).

4. The electrolyte additive according to claim 3, characterized in that The first additive includes at least one of 5. The electrolyte additive according to claim 3, characterized in that, The second additive comprises at least one of 6. The electrolyte additive according to claim 3, characterized in that, The third additive comprises at least one of 7. The electrolyte additive according to claim 3, characterized in that, a fourth additive is further included, the fourth additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, 1,3-propane sultone, polystyrene.

8. The electrolyte additive according to claim 7, characterized in that a mass ratio of the first additive, the second additive, the third additive, the fourth additive in the electrolyte additive is 1:(0.01-10):(0.01-10):(0.005-100).

9. An electrolyte, characterized by comprising the electrolyte additive according to any one of claims 1-8.

10. The electrolyte of claim 9, wherein, a mass percentage of the first additive is 0.1%-5% based on a total mass of the electrolyte; and / or a mass percentage of the second additive is 0.1%-5%.

11. The electrolyte of claim 9, wherein, a mass percentage of the third additive is 0.1%-5% based on a total mass of the electrolyte.

12. The electrolyte of claim 9, wherein, a fourth additive is further included in the electrolyte, a mass percentage of the fourth additive is 0.5%-5% based on a total mass of the electrolyte.

13. The electrolyte of claim 9, wherein, the electrolyte further comprises an electrolyte salt, a mass percentage of the electrolyte salt is 12%-18% based on a total mass of the electrolyte.

14. A battery, characterized by comprising the electrolyte additive according to any one of claims 1-8 or the electrolyte according to any one of claims 9-13.

15. The battery of claim 14, wherein, the battery comprises a positive electrode sheet and a negative electrode sheet, wherein, The battery is a lithium ion battery, the positive active material of the positive electrode sheet includes LiFe 1-x’ M’ x’ PO4, LiMn 2-y’ M y’ O4, and LiNi x Co y Mn z M 1-x-y-z O2, wherein M’ includes one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, M includes one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤x’<1, 0≤y’≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1; and / or The battery is a sodium-ion battery, the positive active material of the positive electrode plate comprises Na c P d (W a O b )Z e , wherein P comprises a transition metal element, W comprises at least one of phosphorus, sulfur, silicon, tungsten, z comprises F atoms, 0≤c≤10, 0≤d≤5, 0≤a≤10, 0≤b≤10, 0≤e≤5; and / or a negative electrode active material of the negative electrode sheet comprises at least one of soft carbon, hard carbon, silicon-based material, tin-based material.

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