Electrolytes for sodium secondary batteries, sodium secondary batteries, and power consumption devices

Abstract

The present application provides an electrolyte for a sodium secondary battery, a sodium secondary battery, and a power consuming device. The electrolyte for a sodium secondary battery includes a diluent, and the diluent is represented by the general formula C n H 2n+2 The diluent contains an alkane, and the value of n is 8 to 13. The diluent can improve the high-temperature cycle performance of the battery, reduce the high-temperature gas generation phenomenon of the battery, and improve the electrochemical performance and safety performance of the battery at high temperatures.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application invokes Chinese patent application No. 202310070404.7, filed on January 16, 2023, titled "Electrolyte for sodium secondary battery, sodium secondary battery, and power consumption device," and all of its provisions are incorporated into this application.

[0002] This application relates to the technology of sodium secondary batteries, and more particularly to electrolytes for sodium secondary batteries, sodium secondary batteries, and power consumption devices. [Background technology]

[0003] With the advancement of battery technology, lithium-ion batteries have come to dominate the portable electronics market and are gradually expanding into large-scale electrical energy storage applications. However, conventional lithium resources can no longer meet the urgent need to establish large-scale and high-energy-density energy storage systems. As a result, sodium-based batteries, which are abundant, inexpensive, and possess electrochemical properties similar to lithium-ion batteries, have emerged as a response to the situation. However, sodium-based batteries, which are currently being widely studied, have relatively poor high-temperature cycling performance and are accompanied by serious high-temperature gas generation phenomena, severely limiting their further application. [Overview of the Initiative]

[0004] This application has been made in view of the above-mentioned problems, and its purpose is to provide an electrolyte for sodium secondary batteries that improves the high-temperature cycle performance of the battery, reduces the high-temperature gas generation phenomenon of the battery, and improves the electrochemical performance and safety performance of sodium secondary batteries at high temperatures.

[0005] A first aspect of this application provides an electrolyte for a sodium secondary battery, the electrolyte comprising a diluent, the diluent of general formula C n H 2n+2containing an alkane, where the value of n is from 8 to 13, and the general formula is C n H 2n+2 By using the alkane as a diluent, a protective layer is formed around the solvation structure, reducing the direct contact between the solvent and the positive and negative electrodes, reducing the side reactions between the positive and negative electrodes and the solvent, improving the cycle performance of the battery at high temperatures, suppressing the gas generation phenomenon during high-temperature cycling of the sodium secondary battery, and improving the electrochemical performance and safety performance of the battery at high temperatures.

[0006] In any embodiment, the diluent includes one or more of n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, 2,3-dimethylheptane, 3-methylheptane, 4-methylheptane, 3-ethylhexane, and optionally one or two of n-nonane and n-decane.

[0007] In any embodiment, the electrolyte further includes a co-solvent, and the co-solvent includes a compound represented by Structural Formula I, JPEG0007905528000001.jpg17165Here, R1 is selected from C 3-9 alkyl groups, and R2 is selected from halogen-substituted or unsubstituted C 1-3 alkyl groups.

[0008] The co-solvent can improve the miscibility between the solvent and the diluent. The diluent contributes to forming a protective layer around the solvation structure, and the co-solvent forms a protective layer structure with the co-solvent as the inner layer and the diluent as the outer layer around the solvation structure as a bridge connecting the solvation structure and the diluent, reducing the side reactions between the positive and negative electrodes and the solvent, endowing the battery with excellent room-temperature cycle performance and high-temperature cycle performance, and having a low high-temperature gas generation amount.

[0009] In any embodiment, R2 includes one or more of -CF3, -CH3, -CH2-CF3, -CH2-CH3, -CF2-CF3, and optionally one or two of -CF2-CF3 and -CF3.

[0010] In any embodiment, the cosolvent comprises one or more of methyl propyl ether, methyl butyl ether, methylheptyl ether, ethyl propyl ether, 2-ethoxybutane, ethylheptyl ether, ethyl amyl ether, methyl octyl ether, propyl butyl ether, propyl nonyl ether, trifluoromethylheptyl ether, 1,1,2,2,2-pentafluoroethylpropyl ether, and 2,2,2-trifluoroethylbutyl ether, and is selectively one or more of methyl butyl ether, methylheptyl ether, ethyl propyl ether, ethylheptyl ether, trifluoromethylheptyl ether, and 1,1,2,2,2-pentafluoroethylpropyl ether.

[0011] In each embodiment, the molar ratio of the diluent to the cosolvent is 1:7 to 7:1, and selectively 1:5 to 5:1.

[0012] By maintaining an appropriate molar ratio between the diluent and cosolvent, a protective layer structure is formed around the solvation structure, with the cosolvent as the inner layer and the diluent as the outer layer. Furthermore, side reactions between the positive and negative electrodes and the solvent are reduced, resulting in the battery having excellent room-temperature and high-temperature cycling performance, and low gas generation.

[0013] In each embodiment, the electrolyte comprises an ethylene glycol ether-based solvent.

[0014] Using ethylene glycol ether-based solvents, the battery exhibits excellent room-temperature and high-temperature cycling performance, as well as low high-temperature gas generation.

[0015] In each embodiment, the molar ratio of the ethylene glycol ether solvent to the diluent is 1:5 to 3:1, and selectively 1:3 to 1:1.

[0016] When the molar ratio of the ethylene glycol ether-based solvent to the diluent is within an appropriate range, it is advantageous for the diluent to form a protective layer around the solvated structure, resulting in the battery having excellent room-temperature and high-temperature cycling performance, and low high-temperature gas generation.

[0017] In any embodiment, the ethylene glycol ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether.

[0018] In any embodiment, the electrolyte further comprises a sodium salt, the sodium salt comprising at least one of a first sodium salt and a second sodium salt, the first sodium salt comprising one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate, and the second sodium salt comprising one or more of sodium difluoro(oxalato)borate, sodium bis(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[0019] With the right sodium salt, the battery exhibits excellent room-temperature and high-temperature cycling performance, as well as low high-temperature gas generation.

[0020] In each embodiment, the mass content of the first sodium salt is 3% to 40%, and selectively 5% to 30%, based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent.

[0021] By having the first sodium salt in an appropriate mass content, the battery exhibits excellent room-temperature and high-temperature cycling performance, as well as low high-temperature gas generation.

[0022] In each embodiment, the mass content of the second sodium salt is 0.1% or more, and selectively 1% or more, based on the total mass of the sodium salt, the ethylene glycol ether system, and the cosolvent.

[0023] By having an appropriate mass content of the second sodium salt, the room-temperature and high-temperature cycle performance of the battery can be improved, and the high-temperature gas generation phenomenon of the battery can be reduced.

[0024] A second aspect of this application provides a sodium secondary battery, the sodium secondary battery comprising the electrolyte in any of the embodiments.

[0025] In each embodiment, the sodium secondary battery includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector.

[0026] This technology can improve the room-temperature and high-temperature cycle performance of undercoated batteries, reduce high-temperature gas generation in batteries, and enhance the electrochemical and safety performance of batteries.

[0027] In each embodiment, the surface density of the undercoating is 5 to 50 g / m². 2 That is the case.

[0028] An appropriate undercoating surface density can optimize the metal deposition effect, improve the high-temperature and room-temperature cycling performance of the battery, and reduce high-temperature gas generation. At the same time, an appropriate undercoating surface density can increase the energy density of the battery and meet its usage demands.

[0029] In any embodiment, the undercoating includes one or more of a carbon coating, an alloy coating, and a metal oxide coating, and is selectively a carbon coating.

[0030] In any embodiment, the undercoating includes one or more of the following: superconducting carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[0031] In each embodiment, the sodium secondary battery is a sodium metal battery without a negative electrode.

[0032] Sodium secondary batteries are negative electrode sodium metal batteries that can improve the room temperature and high temperature cycle performance of the battery, reduce the high-temperature gas generation phenomenon of the battery, and improve the electrochemical performance and safety performance of the battery.

[0033] A third aspect of this application provides a battery module which includes a sodium secondary battery according to the second aspect.

[0034] A fourth aspect of this application provides a battery pack comprising a sodium secondary battery according to the second aspect or a battery module according to the third aspect.

[0035] A fifth aspect of this application provides a power consumption device comprising at least one of a sodium secondary battery according to the second aspect, a battery module according to the third aspect, or a battery pack according to the fourth aspect. [Brief explanation of the drawing]

[0036] [Figure 1] This is a schematic diagram of a sodium secondary battery according to one embodiment of the present application. [Figure 2] Figure 1 is an exploded view of a sodium secondary battery according to one embodiment of this application. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present application. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of this application. [Figure 6]This is a schematic diagram of a power consumption device that uses a sodium secondary battery as a power source according to one embodiment of this application. [Modes for carrying out the invention]

[0037] The following describes in detail embodiments of the sodium secondary battery, battery module, battery pack, and power consumption device disclosed in this application, with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and redundant explanations of structures that are actually the same may be omitted. This is to avoid making the following explanation unnecessarily long and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and do not limit the topics described in the claims.

[0038] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the endpoints, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 can also be assumed. Furthermore, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 can all be assumed. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers a-b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is simply a shortened expression for combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

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

[0041] Unless otherwise specified, the terms “includes” and “inclusion” as used in this application may be open or closed. For example, “includes” and “inclusion” may mean that other components not listed may be included or inclusion, or that only the listed components may be included or inclusion.

[0042] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, the conditions where A is true (or exists) and B is false (or does not exist), where A is false (or does not exist) but B is true (or exists), and where both A and B are true (or exist) all satisfy "A or B".

[0043] When a sodium secondary battery is used or stored at a high temperature, the reaction activities of the positive and negative electrodes and the electrolyte are enhanced, side reactions during the battery cycling process increase significantly, a large amount of gas is generated, the battery is prone to volume expansion, and in severe cases, a short circuit may occur inside the battery, which may also have a serious impact on the electrochemical performance and safety performance of the battery.

[0044] [Electrolyte for Sodium Secondary Battery] This application provides an electrolyte for a sodium secondary battery. The electrolyte contains a diluent, and the diluent contains an alkane of the general formula C n H 2n+2 where the value of n is 8 - 13.

[0045] As used herein, the term "sodium secondary battery" refers to a secondary battery that uses sodium ions as charge carriers. The negative electrode active material of a sodium secondary battery includes a carbon-based material, a titanium-based material, an alloy material, a layered transition metal oxide, a layered transition metal selenide, an organic material, or metallic sodium. Here, a sodium secondary battery with metallic sodium as the negative electrode active material is referred to as a sodium metal battery.

[0046] In some embodiments, the negative electrode active material of the sodium secondary battery includes one or more of a graphite-based carbon material, an amorphous carbon material, and a nano-carbon material.

[0047] In some embodiments, the negative electrode active material of the sodium secondary battery is hard carbon.

[0048] In some embodiments, the negative electrode active material of a sodium secondary battery is metallic sodium.

[0049] In this specification, the term "non-negative electrode sodium metal battery" refers to a sodium metal battery in which the assembly process uses a current collector as the negative electrode, and sodium ions accumulate on the current collector during the charging process to form a sodium metal negative electrode.

[0050] In this specification, the term "electrolyte" refers to a carrier that transports ions in a sodium secondary battery, and includes liquid electrolytes, solid electrolytes, or quasi-solid electrolytes.

[0051] In this specification, the term "diluent" refers to an insoluble or sparingly soluble component of an electrolyte salt, where there is no significant coordination or association between the diluent molecule and the cation of the electrolyte salt, and the diluent does not disrupt the solvation structure.

[0052] A solvated structure is a structure formed when a sodium salt dissolves in an electrolyte, and the solvent molecules bind to the cations much more strongly than the anions. As a result, the solvent aggregates around the sodium ions. The aggregates formed by the sodium ions and the solvent are called solvated structures.

[0053] In this specification, the term "alkane" refers to a chain-like saturated hydrocarbon compound in which all carbon atoms in the molecule are bonded by single bonds, and all remaining valence bonds are bonded to hydrogen atoms.

[0054] General formula C n H 2n+2Alkanes have relatively low solubility in sodium salts, and do not directly participate in the solvation structure of sodium ions. They do not affect the film formation performance on the positive and negative electrode surfaces of sodium secondary batteries. Furthermore, alkanes form a protective layer around the solvation structure, reducing direct contact between the solvent and the positive and negative electrodes, minimizing side reactions between the electrodes and the solvent, improving the high-temperature cycle performance of the battery, and suppressing gas generation during high-temperature cycling of sodium secondary batteries. Additionally, by adding alkane diluents, the viscosity of the electrolyte can be reduced and the ionic conductivity of the electrolyte increased without destroying the solvation structure, thereby improving the electrochemical performance of the battery.

[0055] Taking a sodium metal battery as an example, alkanes are very stable with sodium metal, and do not chemically react with the sodium metal negative electrode. Alkanes are used to form a protective layer around the solvent structure, reducing direct contact between the solvent and the positive and negative electrodes. Furthermore, the surrounding alkanes do not react with the positive and negative electrodes, reducing side reactions between the positive and negative electrodes and the solvent, thereby improving the electrochemical performance and safety performance of the battery at high temperatures.

[0056] In summary, the general formula C is n H 2n+2 Alkane diluents can improve the high-temperature cycling performance of batteries, reduce high-temperature gas generation phenomena in batteries, and improve the electrochemical and safety performance of batteries at high temperatures.

[0057] In some embodiments, the diluent is of the general formula C8H 18 C9H 20 , C 10 H 22 , C 11 H 24 , C 12 H 26 , C 13 H 28 It contains one or more of the alkanes.

[0058] In some embodiments, the diluent includes one or more of the following: n-octane and its isomers, n-nonane and its isomers, n-decane and its isomers, n-undecane and its isomers, n-dodecane and its isomers, n-tridecane and its isomers.

[0059] In this specification, the term "isomer" refers to a compound that has the same molecular formula but a different structure. For example, isomers of n-octane include, but are not limited to, 2-methylheptane, 3-methylheptane, 4-methylheptane, 3-ethylhexane, 2,2-dimethylhexane, 2-methyl-3-ethylpentane, 2,2,3-trimethylpentane, and 2,2,3,3-tetramethylbutane.

[0060] In some embodiments, the diluent comprises one or more of n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, 2,3-dimethylheptane, 3-methylheptane, 4-methylheptane, and 3-ethylhexane.

[0061] In some embodiments, the diluent comprises one or two of n-nonane and n-decane.

[0062] With an appropriate diluent, the protective layer structure surrounding the solventized structure becomes more stable, and the electrolyte has appropriate viscosity and excellent ionic conductivity, further improving the room-temperature and high-temperature cycle performance of the battery and reducing the high-temperature gas generation phenomenon of the battery.

[0063] In some embodiments, the electrolyte further comprises a cosolvent, the cosolvent comprising a compound represented by structural formula I, JPEG0007905528000002.jpg17165 Here, R1 is C 3-9 Selected from alkyl groups, R2 is halogen-substituted or unsubstituted C 1-3 Selected from alkyl groups.

[0064] In this specification, the term "C 3-9An alkyl group is a linear or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms. The group is non-saturated, has 3 to 9 carbon atoms, and is attached to the rest of the molecule via single bonds.

[0065] In this specification, the term "C 1-3 An alkyl group is a linear or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms. The group is non-saturated, has 1 to 3 carbon atoms, and is attached to the rest of the molecule via single bonds.

[0066] In this specification, the term "halogen substitution" means that at least one hydrogen atom of the compound or chemical moiety is substituted with a halogen atom or a halogen alkyl group.

[0067] In this specification, the term "halogen alkyl group" refers to an alkyl group containing at least one halogen atom.

[0068] In this specification, the term "halogen" refers to fluorine, chlorine, bromine, or iodine.

[0069] Taking ethylene glycol ether solvents as an example, R1 is a long-chain alkyl group that is mutually soluble with alkane diluents, and R2 forms an alkoxy group with an oxygen atom and is mutually soluble with the solvent. The co-solvent can improve the miscibility between the solvent and the diluent, and the diluent contributes to forming a protective layer around the solvation structure. Furthermore, the co-solvent acts as a bridge between the solvation structure and the diluent, forming a protective layer structure around the solvation structure with the co-solvent as the inner layer and the diluent as the outer layer. This reduces side reactions between the positive and negative electrodes and the solvent, enabling the battery to have excellent room-temperature and high-temperature cycling performance and low high-temperature gas generation.

[0070] In some embodiments, R2 includes one or more of -CF3, -CH3, -CH2-CF3, -CH2-CH3, and -CF2-CF3.

[0071] In some embodiments, R2 includes one or two of -CF2-CF3, -CF3.

[0072] In some embodiments, R2 includes -CF2-CF3.

[0073] In some embodiments, the cosolvent includes one or more of methyl propyl ether, methyl butyl ether, methylheptyl ether, ethyl propyl ether, 2-ethoxybutane, ethylheptyl ether, ethyl amyl ether, methyl octyl ether, propyl butyl ether, propyl nonyl ether, trifluoromethylheptyl ether, 1,1,2,2,2-pentafluoroethylpropyl ether, and 2,2,2-trifluoroethylbutyl ether.

[0074] In some embodiments, the cosolvent includes one or more of methyl butyl ether, methylheptyl ether, ethyl propyl ether, ethylheptyl ether, trifluoromethylheptyl ether, and 1,1,2,2,2-pentafluoroethylpropyl ether.

[0075] In some embodiments, the molar ratio of the diluent to the cosolvent is 1:7 to 7:1. In some embodiments, the molar ratio of the diluent to the cosolvent is selectively 1:7 to 1:6, 1:7 to 1:5, 1:7 to 1:4, 1:7 to 1:3, 1:7 to 1:2, 1:7 to 1:1, 1:7 to 2:1, 1:7 to 3:1, 1:7 to 4:1, 1:7 to 5:1, 1:7 to 6:1, 1:7 to 7:1, 1:6 to 1:5, 1:6 to 1:4, 1:6 to 1:3, 1:6 to 1:2, 1:6 to 1:1. , 1:6~2:1, 1:6~3:1, 1:6~4:1, 1:6~5:1, 1:6~6:1, 1:6~7:1, 1:5~1:4, 1:5~1:3, 1:5~1:2, 1:5~1:1, 1:5~2:1, 1:5~3:1, 1:5~4:1, 1:5~5:1, 1:5~6:1, 1:5~7:1, 1:4~1:3, 1:4~1:2, 1:4~1:1, 1:4~2:1, 1:4~3: 1, 1:4~4:1, 1:4~5:1, 1:4~6:1, 1:4~7:1, 1:3~1:2, 1:3~1:1, 1:3~2:1, 1:3~3:1, 1:3~4:1, 1:3~5:1, 1:3~6:1, 1:3~7:1, 1:2~1:1, 1:2~2:1, 1:2~3:1, 1:2~4:1, 1:2~5:1, 1:2~6:1, 1:2~7:1, 1:1~2:1, 1:1~3 It is one of the following: 1, 1:1~4:1, 1:1~5:1, 1:1~6:1, 1:1~7:1, 2:1~3:1, 2:1~4:1, 2:1~5:1, 2:1~6:1, 2:1~7:1, 3:1~4:1, 3:1~5:1, 3:1~6:1, 3:1~7:1, 4:1~5:1, 4:1~6:1, 4:1~7:1, 5:1~6:1, 5:1~7:1, or 6:1~7:1.

[0076] When the molar ratio of the diluent to the cosolvent is within an appropriate range, the diluent forms a protective structure on the outer layer of the solvation structure, which is advantageous in reducing side reactions between the positive and negative electrodes and the solvent, resulting in the battery having excellent room temperature and high temperature cycling performance and low gas generation.

[0077] In some embodiments, the molar ratio of the diluent to the cosolvent is 1:5 to 5:1. In some embodiments, the molar ratio of the diluent to the cosolvent is selectively 1:5 to 1:4, 1:5 to 1:3, 1:5 to 1:2, 1:5 to 1:1, 1:5 to 2:1, 1:5 to 3:1, 1:5 to 4:1, 1:5 to 5:1, 1:4 to 1:3, 1:4 to 1:2, 1:4 to 1:1, 1:4 to 2:1, 1:4 to 3:1, 1:4 to 4:1, 1:4 to 5:1, 1:3 to 1:2, 1:3 to 1: It is one of the following: 1, 1:3~2:1, 1:3~3:1, 1:3~4:1, 1:3~5:1, 1:2~1:1, 1:2~2:1, 1:2~3:1, 1:2~4:1, 1:2~5:1, 1:1~2:1, 1:1~3:1, 1:1~4:1, 1:1~5:1, 2:1~3:1, 2:1~4:1, 2:1~5:1, 3:1~4:1, 3:1~5:1, 4:1~5:1.

[0078] Maintaining an appropriate molar ratio between the diluent and cosolvent is advantageous for forming a protective structure on the outer layer of the solvation structure, reducing side reactions between the positive and negative electrodes and the solvent, further improving the room-temperature and high-temperature cycling performance of the battery, and reducing the high-temperature gas generation phenomenon of the battery.

[0079] In some embodiments, the electrolyte includes an ethylene glycol ether-based solvent.

[0080] In some embodiments, the ethylene glycol ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether.

[0081] In this specification, the term "ethylene glycol ether" refers to a compound having the structure shown in formula II. JPEG0007905528000003.jpg13150 Here, the value of m is 1 to 4, and R3 is C 1-6 Selected from alkyl groups.

[0082] In this specification, the term "C 1-6 An alkyl group is a linear or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms. The group is non-saturated, has 1 to 6 carbon atoms, and is attached to the rest of the molecule via single bonds.

[0083] The molecules of ethylene glycol ether-based solvents can establish a stable electrode / electrolyte interface on the negative electrode surface, form a stable SEI, reduce electrochemical polarization, and provide the battery with excellent room-temperature and high-temperature cycling performance, as well as low high-temperature gas generation.

[0084] In some embodiments, the molar ratio of the ethylene glycol ether solvent to the diluent is 1:5 to 3:1. In some embodiments, the molar ratio of the ethylene glycol ether solvent to the diluent is one of the following: 1:5 to 1:4, 1:5 to 1:3, 1:5 to 1:2, 1:5 to 1:1, 1:5 to 2:1, 1:5 to 3:1, 1:4 to 1:3, 1:4 to 1:2, 1:4 to 1:1, 1:4 to 2:1, 1:4 to 3:1, 1:3 to 1:2, 1:3 to 1:1, 1:3 to 2:1, 1:3 to 3:1, 1:2 to 1:1, 1:2 to 2:1, 1:2 to 3:1, 1:1 to 2:1, 1:1 to 3:1, 2:1 to 3:1.

[0085] When the molar ratio of the ethylene glycol ether-based solvent to the diluent is within an appropriate range, it is advantageous for the diluent to form a protective layer around the solvated structure, resulting in the battery having excellent room-temperature and high-temperature cycling performance, and low high-temperature gas generation.

[0086] In some embodiments, the molar ratio of the ethylene glycol ether solvent to the diluent is 1:3 to 1:1. In some embodiments, the molar ratio of the ethylene glycol ether solvent to the diluent is one of the following: 1:3 to 1:2, 1:3 to 1:1, or 1:2 to 1:1.

[0087] When the molar ratio of the ethylene glycol ether-based solvent to the diluent is within an appropriate range, it is advantageous for the diluent to form a protective layer around the solvated structure, further improving the room-temperature and high-temperature cycle performance of the battery and reducing the high-temperature gas generation phenomenon of the battery.

[0088] In some embodiments, the electrolyte further comprises a sodium salt, the sodium salt comprising at least one of a first sodium salt and a second sodium salt.

[0089] In some embodiments, the sodium salt comprises a first sodium salt and a second sodium salt.

[0090] In some embodiments, the first sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate.

[0091] The weak bonding force between anions and sodium ions in the first sodium salt allows for rapid deposition and detachment of sodium metal, which is advantageous for improving the kinetic performance of the battery. In particular, in a non-negative electrode sodium metal battery, the first sodium salt can effectively guarantee the battery's cycle performance, and with the appropriate sodium salt, the electrolyte has appropriate viscosity and excellent ionic conductivity, resulting in a battery with excellent room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation.

[0092] In some embodiments, the second sodium salt includes one or more of the following: sodium difluoro(oxalato)borate, sodium bis(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[0093] The second sodium salt includes a sulfur-containing organic sodium salt or a boron-containing organic sodium salt, and readily participates in the formation of a structurally stable and uniformly distributed SEI, thereby improving the high-temperature cycle performance of the battery and reducing the high-temperature gas generation phenomenon of the battery. Furthermore, with the appropriate sodium salt, the electrolyte has appropriate viscosity and excellent ionic conductivity, and the battery has excellent room-temperature cycle performance, high-temperature cycle performance, and low high-temperature gas generation.

[0094] In some embodiments, the mass content of the first sodium salt is 3% to 40% based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent. In some embodiments, the mass content of the first sodium salt is selectively 3% to 5%, 3% to 10%, 3% to 15%, 3% to 20%, 3% to 25%, 3% to 30%, 3% to 35%, 3% to 40%, 5% to 10%, 5% to 15%, 5% to 20%, 5% to 25%, 5% to 30%, 5% to 35%, 5% to 40%, and 10%. It is one of the following percentages: 15%, 10%, 20%, 10%, 25%, 10%, 30%, 10%, 35%, 10%, 40%, 15%, 20%, 15%, 25%, 15%, 30%, 15%, 35%, 15%, 40%, 20%, 25%, 20%, 30%, 20%, 35%, 20%, 40%, 25%, 30%, 25%, 35%, 25%, 40%, 30%, 35%, 30%, 40%, or 35%.

[0095] By having the mass content of the primary sodium salt within an appropriate range, the electrolyte has appropriate viscosity and excellent ionic conductivity, the battery has excellent room temperature cycling performance and high temperature cycling performance, low high-temperature gas generation, and extends the operating temperature range of the battery.

[0096] In some embodiments, the mass content of the first sodium salt is 5% to 30% based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent. In some embodiments, the mass content of the first sodium salt is selectively one of the following, based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent: 5% to 10%, 5% to 15%, 5% to 20%, 5% to 25%, 5% to 30%, 10% to 15%, 10% to 20%, 10% to 25%, 10% to 30%, 15% to 20%, 15% to 25%, 15% to 30%, 20% to 25%, 20% to 30%, and 25% to 30%.

[0097] By ensuring the mass content of the primary sodium salt is within an appropriate range, the electrolyte can possess appropriate viscosity and excellent ionic conductivity, thereby improving the battery's room-temperature and high-temperature cycle performance and enhancing its electrochemical performance.

[0098] In some embodiments, the mass content of the second sodium salt is 0.1% or more based on the total mass of the sodium salt, the ethylene glycol ether system and the cosolvent. In some embodiments, the mass content of the second sodium salt is one or more of the following, based on the total mass of the sodium salt, the ethylene glycol ether system and the cosolvent: 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, and 40%.

[0099] By ensuring the mass content of the second sodium salt is within an appropriate range, the electrolyte can have appropriate viscosity and excellent ionic conductivity, improving the battery's room-temperature and high-temperature cycle performance and reducing the high-temperature gas generation phenomenon of the battery.

[0100] In some embodiments, the mass content of the second sodium salt is 1% or more based on the total mass of the sodium salt, the ethylene glycol ether system and the cosolvent. In some embodiments, the mass content of the second sodium salt is one or more of the following, based on the total mass of the sodium salt, the ethylene glycol ether system and the cosolvent: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, and 40%.

[0101] By ensuring the mass content of the second sodium salt is within an appropriate range, the electrolyte possesses appropriate viscosity and excellent ionic conductivity, further improving the battery's room-temperature and high-temperature cycle performance and reducing the high-temperature gas generation phenomenon of the battery.

[0102] In some embodiments, the electrolyte further selectively includes other additives that can improve certain aspects of the battery's performance, such as additives that improve the battery's overcharge performance or additives that improve the thermal stability of the electrolyte.

[0103] [Sodium secondary battery] This application provides a sodium secondary battery, the sodium secondary battery comprising an electrolyte in any of the embodiments.

[0104] In some embodiments, the sodium secondary battery includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector.

[0105] In this specification, the term "undercoating on at least one side of the negative electrode current collector" means that an undercoating is applied to one or both sides of the current collector, and the undercoating may be in direct contact with the current collector, i.e., there is no other structure between the current collector and the undercoating, and the undercoating may not be in direct contact with the current collector, i.e., there is a further other structure between the current collector and the undercoating.

[0106] The undercoating has the characteristic of having a low metal nucleation potential, which can effectively improve the metal deposition / dissolution performance. It can also mitigate the large volume changes that occur in the battery core during the metal deposition / dissolution process, stabilize the battery core structure, improve the room temperature and high temperature cycling performance of the battery, reduce high-temperature gas generation phenomena in the battery, and improve the electrochemical performance and safety performance of the battery.

[0107] In some embodiments, the surface density of the undercoating is 5-50 g / m². 2 That is the case.

[0108] In some embodiments, the surface density of the undercoating is selectively 5-10 g / m². 2 5-20g / m 2 5-30g / m 2 5-40g / m 2 5-50g / m 2 , 10-20g / m 2 , 10-30g / m 2 , 10-40g / m 2 , 10-50g / m 2 20-30g / m 2 20-40g / m 2 , 20-50g / m 2 30-40g / m 2 30-50g / m 2 40-50g / m 2 It is one of the following.

[0109] An appropriate undercoating surface density can optimize the metal deposition effect, improve the high-temperature and room-temperature cycling performance of the battery, and reduce high-temperature gas generation. At the same time, an appropriate undercoating surface density can increase the energy density of the battery and meet its usage demands.

[0110] In any embodiment, the undercoating includes one or more of a carbon coating, an alloy coating, and a metal oxide coating, and is selectively a carbon coating.

[0111] In any embodiment, the undercoating includes one or more of the following: superconducting carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[0112] In some embodiments, the undercoating includes an adhesive, which comprises one of the following: polyvinylidene fluoride, sodium carboxymethylcellulose, styrene-butadiene rubber, sodium alginate, lithium / sodium polyacrylate, polytetrafluoroethylene, polyimide, and polyurethane.

[0113] In some embodiments, the undercoating is a metallic coating, the metal has a body-centered cubic structure, and the metal comprises one of α-Fe, V, Nb, Cr, Mo, Ta, and W.

[0114] In some embodiments, the undercoating is an alloy coating, and the alloy includes an alloy consisting of one or more of the metals Au, Ag, Sn, and Sb.

[0115] In some embodiments, the undercoating is a metal oxide coating, and the oxide comprises at least one of copper oxide and aluminum oxide.

[0116] In some embodiments, the undercoating is a conductive polymer coating, the conductive polymer comprising one of polyaniline, polythiophene, polypyrrole, or polyphenylenevinylene.

[0117] In some embodiments, the undercoating is a conductive ceramic coating, and the conductive ceramic material comprises at least one of TiB2, TiC, and B4C3.

[0118] In some embodiments, the undercoating is a conductive carbon coating, and the conductive carbon includes at least one of conductive carbon black, graphite, carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and fullerene.

[0119] In some embodiments, the sodium secondary battery is a sodium metal battery without a negative electrode.

[0120] In some embodiments, the sodium secondary battery is a sodium metal battery without a negative electrode. The sodium metal battery without a negative electrode does not use a negative electrode active material, employing only a negative electrode current collector as the negative electrode. Sodium plating is completed on the negative electrode during the initial charging process, and this is returned to the positive electrode during discharge, thereby achieving a charge-discharge cycle. Because there is no negative electrode material and only a negative electrode current collector is used, the sodium metal battery without a negative electrode effectively overcomes the shortcomings of sodium metal batteries and can achieve a higher energy density than a metallic sodium negative electrode.

[0121] Sodium secondary batteries are non-negative sodium metal batteries that can improve the room temperature and high temperature cycle performance of the battery, reduce high-temperature gas generation phenomena in the battery, and improve the electrochemical performance and safety performance of the battery at high temperatures.

[0122] In some embodiments, the CB value of the non-negative electrode sodium metal battery is 0.1 or less.

[0123] The CB value in a sodium secondary battery is calculated by dividing the capacity per unit area of ​​the negative electrode plate by the capacity per unit area of ​​the positive electrode plate. Since a non-negative electrode sodium metal battery does not contain negative electrode active material, the capacity per unit area of ​​the negative electrode plate is relatively small, and the CB value of the secondary battery is 0.1 or less.

[0124] In some embodiments, the negative electrode current collector used in the negative electrode plate includes at least one of a metal foil current collector, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, and a carbon paper current collector. Sodium ions do not form alloys with aluminum, and based on considerations of cost reduction and weight reduction, sodium secondary batteries preferentially employ aluminum-based current collectors. The aluminum-based current collector is one of aluminum foil, aluminum alloy foil, and an aluminum-based composite current collector. The aluminum-based composite current collector includes a polymer base film and aluminum foil and / or aluminum alloy foil formed on both sides of the polymer base film. Specifically, the aluminum-based composite current collector has a "sandwich" structure, with the polymer base film located in the center and aluminum foil provided on both sides, or on both sides of the aluminum foil. A luminium alloy foil may be provided, or an aluminum foil may be provided on one side of the polymer base film and an aluminum alloy foil on the other side. The polymer base film is one of the following: polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polychloroethylene, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly-p-phenylene terephthalamide, polypropylethylene, polyformaldehyde, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, or polycarbonate.

[0125] [Positive electrode plate] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer formed on at least a portion of the surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material may include at least one of a layered transition metal oxide, a polyanionic compound, and a Prussian blue compound.

[0126] The transition metal in the layered transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Selectively, the layered transition metal oxide is, for example, NaxMO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 <x≦1である。

[0127] Polyanionic compounds include metal ions, transition metal ions, and tetrahedral (YO4) compounds. n- The compound may have an anionic unit. The metal ion is selectively one of sodium ions, lithium ions, potassium ions, and zinc ions; the transition metal is selectively at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y is selectively at least one of P, S, and Si; and n is (YO4) n- This represents the valence state of an atom.

[0128] Prussian blue compounds include sodium ions, transition metal ions, and cyanide ions (CN - The compound may have ). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound may be, for example, Na a Me b Me' c (CN)6, where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 <a≦2、0<b<1、0<c<1である。

[0129] The positive electrode active material layer may further contain a conductive agent to improve the conductivity of the positive electrode. The conductive agent is selectively one or more of the following: Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0130] The positive electrode active material layer may further contain an adhesive to firmly bond the positive electrode active material and a selective conductive agent to the positive electrode current collector. The adhesive is selectively at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0131] The positive electrode current collector can be a conductive carbon piece, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon piece is selectively one or more of Super P, carbon black, Ketjenblack, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate is independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector may be a composite current collector formed by combining a metal foil and a polymer-based film.

[0132] In some embodiments, a positive electrode plate can be manufactured by the following method. Components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and any other component, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode plate is obtained.

[0133] [Separator] In some embodiments, the sodium secondary battery further includes a separator. This application is not particularly limited to the type of separator, and any known porous separator having good chemical and mechanical stability may be selected.

[0134] In some embodiments, the material of the separator may be selected from at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and is not particularly limited.

[0135] In some embodiments, the positive electrode plate, negative electrode plate, and separator can be manufactured into an electrode assembly by a winding process or a lamination process.

[0136] In some embodiments, the sodium secondary battery may include an outer casing. This casing may be used to package the electrode assembly and the electrolyte.

[0137] In some embodiments, the casing of the sodium secondary battery may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the sodium secondary battery may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0138] This application does not particularly limit the shape of the sodium secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular sodium secondary battery 5 as an example.

[0139] In some embodiments, referring to Figure 2, the casing may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing and forming a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening so as to seal the housing cavity. The positive electrode plate, negative electrode plate and separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged within the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the sodium secondary battery 5 may be one or more, and those skilled in the art can specifically select them according to actual needs.

[0140] In some embodiments, the sodium secondary batteries may be assembled into a battery module, and the number of sodium secondary batteries included in the battery module may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0141] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, multiple sodium secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple sodium secondary batteries 5 can be fixed in place by fasteners.

[0142] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of sodium secondary batteries 5 are housed.

[0143] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0144] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, the upper housing 2 covering the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0145] Furthermore, this application provides a power consumption device comprising at least one of a sodium secondary battery, a battery module, or a battery pack according to this application. The sodium secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. The power consumption device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0146] As the power consumption device, a sodium secondary battery, a battery module, or a battery pack can be selected according to the usage demand.

[0147] Figure 6 shows an example of a power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power output and high energy density requirements of the sodium secondary battery in this power consumption device, a battery pack or battery module can be used.

[0148] Other examples of such devices include mobile phones, tablet computers, and laptop computers. These devices generally require a thin profile and can utilize sodium-ion batteries as their power source.

[0149] Examples The following describes embodiments of this application. The embodiments described below are illustrative and are for interpretive purposes only and should not be considered as limitations thereon. In the embodiments, unless specific technical or conditional details are shown, the procedures are carried out in accordance with the technical or conditional details described in the literature in the art or in accordance with the product specifications. The manufacturers of the reagents or instruments used are not indicated, and all are common products that are commercially available. In the embodiments described below, only cases where the secondary battery is a sodium-ion battery are shown, but this application is not limited thereto.

[0150] 1. Manufacturing method Example 1 1) Manufacturing of electrolytes In an argon gas-atmosphered glove box with a moisture content of <10 ppm, the first sodium salt, sodium hexafluorophosphate, and the second sodium salt, sodium bis(fluorosulfonyl)imide, were added to ethylene glycol dimethyl ether solvent to obtain a mixed solution. Subsequently, n-nonane as a diluent and methyl butyl ether as a cosolvent were added to the mixed solution to obtain an electrolyte. Here, the molar ratio of n-nonane to methyl butyl ether was 1:1, and the molar ratio of ethylene glycol dimethyl ether to n-nonane was 1:2. Based on the total mass of the first sodium salt, the second sodium salt, ethylene glycol dimethyl ether, and methyl butyl ether, the mass content of sodium hexafluorophosphate was 15%, and the mass content of sodium bis(fluorosulfonyl)imide was 3%.

[0151] 2) Manufacturing of positive electrode plates A positive electrode slurry was prepared by uniformly mixing the positive electrode active material Na3V2(PO4)3, the adhesive polyvinylidene fluoride (PVDF), and the conductive agent conductive carbon black (Super-P) in a mass ratio of 96%:2%:2% in N-methylpyrrolidone (NMP) solvent. The slurry was then applied to the surface of aluminum foil using a squeeze coater according to the required mass per unit area of ​​the positive electrode active material, dried, and then the coated electrode plate was processed using a cold press at a density of 2.5 g / cm². 3The final positive electrode plate was obtained by cold pressing at the design pressure density during manufacturing.

[0152] 3) Manufacturing of negative electrode plates Carbon nanotubes and sodium alginate are added to deionized water and stirred to form a uniform slurry. The slurry is then coated onto the negative electrode current collector, dried, and cut to obtain a negative electrode plate with a non-negative electrode structure. Here, the surface density of the undercoating is 20 g / m². 2 That is the case.

[0153] 4) Separator A polyethylene film (PE separator) was used as the separator.

[0154] 5) Battery manufacturing The positive electrode plate, separator, and negative electrode plate were stacked in order, with the separator positioned between the positive and negative electrode plates to provide isolation. The electrolyte was then added to assemble a button-type battery.

[0155] Examples 2-38 Aside from differences in the electrolyte composition and / or the manufacturing parameters of the negative electrode plate, the other steps in Examples 2 to 38 are the same as in Example 1. Hereinafter, the manufacturing methods for the negative electrode plate in Examples 37 and 38 are as follows, and the specific parameters are shown in Tables 1 and 2.

[0156] Example 37: Carbon nanotubes and sodium alginate were added to deionized water and stirred to form a uniform slurry. The slurry was then coated onto an aluminum foil negative electrode current collector, dried, and cut to obtain a negative electrode current collector with an undercoating. Here, the surface density of the undercoating was 20 g / m². 2 The negative electrode active material, hard carbon, the conductive agent, acetylene black, the adhesive, styrene-butadiene rubber (SBR), and the thickener, hydroxymethylcellulose (CMC), were thoroughly stirred and mixed in an appropriate amount of deionized water in a weight ratio of 90:5:4:1 to form a uniform negative electrode slurry. This slurry was then applied to a negative electrode current collector having an undercoat, dried at 100°C, and then pressed to obtain a negative electrode plate.

[0157] Example 38: The negative electrode plate is aluminum foil.

[0158] Comparative Examples 1-6 Except for differences in the electrolyte composition and / or the manufacturing parameters of the negative electrode plate, Comparative Example 5 is the same as the negative electrode plate manufacturing method of Example 37, and Comparative Example 6 is the same as the negative electrode plate manufacturing method of Example 38, with the specific parameters shown in Tables 1 and 2.

[0159] 2. Battery performance test 1) Room temperature cycling performance At 25°C and normal pressure (0.1 MPa), the battery was charged to a voltage of 3.5V with a constant current of 0.5C, and then discharged to a voltage of 3.2V with a constant current of 1C. This constituted one charge-discharge cycle. The initial discharge capacity was set to 100%, and the charge-discharge cycle was repeated 500 times. After stopping the test, the cycle capacity retention rate was recorded, and the room-temperature capacity retention rate was used as an indicator to evaluate the battery's room-temperature cycle performance.

[0160] 2) High-temperature cycle performance Under normal pressure (0.1 MPa) at 60°C, the battery was charged to a voltage of 3.5V with a constant current of 0.5C, and then discharged to a voltage of 3.2V with a constant current of 1C. This constituted one charge-discharge cycle. The initial discharge capacity was set to 100%, and the charge-discharge cycle was repeated 500 times. After stopping the test, the cycle capacity retention rate was recorded, and the high-temperature capacity retention rate was used as an indicator to evaluate the battery's high-temperature cycle performance.

[0161] 3) High-temperature gas generation performance Under room temperature (25°C) conditions, the battery was charged to 3.5V with a constant current of 0.5C. After the battery was fully charged, the initial volume of the battery was tested using the drainage method. The battery was stored in a 60°C oven for 24 days, and then removed. It was left at room temperature for 60 minutes. The volume of the battery was tested using the drainage method within 60 minutes after it had cooled to room temperature. The volume expansion rate of the battery was calculated using the volume of the battery tested before storage as the baseline. The volume expansion rate (%) after storing the battery at 60°C for 24 days is = (volume of the battery measured after storage / volume of the battery measured before storage) - 1.

[0162] The test procedures for the comparative examples and other examples are the same as described above.

[0163] III. Test Results The test results for the above examples and comparative examples are shown in Tables 1 and 2.

[0164] [Table 1-1] [Table 1-2] [Table 1-3]

[0165] [Table 2-1] [Table 2-2] [Table 2-3] [Table 2-4]

[0166] As can be seen from the above results, the electrolytes for sodium secondary batteries in Examples 1 to 38 all contained a diluent, and the diluent contained n-nonane, n-decane, n-octane, n-tridecane, or 2,3-dimethylheptane. As can be seen from the comparison between Examples 1 to 21, 23 to 26, 28 to 36 and Comparative Examples 1 to 2, Example 22 and Comparative Example 3, Example 27 and Comparative Example 4, and Examples 37 to 38 and Comparative Examples 5 to 6, the diluent was able to improve the high-temperature capacity retention rate of the battery, improve the high-temperature cycle performance of the battery, reduce the high-temperature expansion rate of the battery, reduce the high-temperature gas generation phenomenon of the battery, and improve the electrochemical performance and safety performance of the battery at high temperatures.

[0167] As can be seen from the comparison between Examples 1-2 and Examples 3-5, the diluent containing n-nonane or n-decane further improved the room-temperature and high-temperature cycle performance of the battery and reduced the high-temperature gas generation phenomenon of the battery.

[0168] The electrolytes for sodium secondary batteries in Examples 1 to 38 all contained a cosolvent, which was methyl butyl ether, methylheptyl ether, ethyl propyl ether, or ethylheptyl ether. The batteries exhibited excellent room-temperature cycling performance, high-temperature cycling performance, and low high-temperature gas generation.

[0169] In Examples 1 to 38, the molar ratio of the diluent to the cosolvent was 1:7 to 7:1, and the batteries exhibited excellent room-temperature cycling performance, high-temperature cycling performance, and low high-temperature gas generation.

[0170] As can be seen from the comparison between Examples 1, 10-11 and Examples 9 and 12, the molar ratio of the diluent to the cosolvent was 1:5 to 5:1, which further improved the room-temperature and high-temperature cycle performance of the battery and reduced the high-temperature gas generation phenomenon of the battery.

[0171] The electrolytes for sodium secondary batteries in Examples 1 to 38 were all contained in an ethylene glycol ether-based solvent, and the diluents were ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, or diethylene glycol dimethyl ether. The batteries exhibited excellent room temperature cycling performance, high temperature cycling performance, and low high-temperature gas generation.

[0172] In Examples 1 to 38, the molar ratio of the ethylene glycol ether-based solvent to the diluent was 1:5 to 3:1, and the batteries exhibited excellent room-temperature cycling performance, high-temperature cycling performance, and low high-temperature gas generation.

[0173] As can be seen from the comparison between Examples 1, 14-15 and Examples 13 and 16, the molar ratio of the ethylene glycol ether solvent to the diluent was 1:3 to 1:1, which further improved the room temperature and high temperature cycle performance of the battery and reduced the high-temperature gas generation phenomenon of the battery.

[0174] The electrolytes in Examples 1 to 38 further contained a sodium salt, the sodium salt comprising one or two of a first sodium salt and a second sodium salt, the first sodium salt comprising sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), or sodium trifluoroacetate (CF3COONa), and the second sodium salt comprising sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), or sodium bis(oxalato)borate (NaBOB), and the batteries exhibited excellent room temperature cycling performance, high temperature cycling performance, and low high-temperature gas generation.

[0175] In Examples 1-26 and 28-38, the mass content of the first sodium salt was 3% to 40% based on the total mass of the sodium salt, ethylene glycol ether-based solvent, and cosolvent. The batteries exhibited excellent room-temperature and high-temperature cycling performance, as well as low high-temperature gas generation.

[0176] As can be seen from the comparison between Examples 1, 24-25 and Examples 23, 26, the mass content of the first sodium salt was 5% to 30% based on the total mass of the sodium salt, ethylene glycol ether solvent, and cosolvent, which further improved the room temperature cycle performance and high temperature cycle performance of the battery, and improved the electrochemical performance of the battery.

[0177] As can be seen from the comparison between Examples 1, 31-32 and Example 30, the mass content of the second sodium salt was 0.1% or more based on the total mass of the sodium salt, ethylene glycol ether solvent, and cosolvent, which improved the room temperature cycle performance and high temperature cycle performance of the battery and reduced the high-temperature gas generation phenomenon of the battery.

[0178] As can be seen from the comparison between Examples 1 and 32 and Examples 30-31, the mass content of the second sodium salt was 1% or more based on the total mass of the sodium salt, ethylene glycol ether solvent, and cosolvent, which further improved the room temperature cycle performance and high temperature cycle performance of the battery and reduced the high-temperature gas generation phenomenon of the battery.

[0179] As can be seen from a comparison between Examples 1 and 37 and Example 38, the negative electrode plate includes a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector, which improved the room temperature cycle performance and high temperature cycle performance of the battery, reduced the high-temperature gas generation phenomenon of the battery, and improved the electrochemical performance and safety performance of the battery.

[0180] As can be seen from the comparison between Examples 1, 33-34 and Examples 35-36, the surface density of the undercoating is 5-50 g / m². 2 As a result, we were able to improve the battery's room-temperature and high-temperature cycle performance, reduce the high-temperature gas generation phenomenon in the battery, and improve the battery's electrochemical and safety performance.

[0181] As can be seen from the comparison between Example 1 and Example 37, the sodium secondary battery is a sodium metal battery without a negative electrode, and it was possible to improve the room temperature cycle performance and high temperature cycle performance of the battery, reduce the high-temperature gas generation phenomenon of the battery, and improve the electrochemical performance and safety performance of the battery.

[0182] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are illustrative, and any embodiments that have substantially the same configuration as the technical idea and produce the same effects within the scope of the technical proposal of this application are included within the scope of the technical proposal of this application. Furthermore, other methods that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive, and by combining some of the components of the embodiments, are also included within the scope of this application, without departing from the spirit of this application. Preferred embodiments of the present invention are as follows: [1] An electrolyte for a sodium secondary battery, wherein the electrolyte includes a diluent, and the diluent is of general formula C nH 2n+2 An electrolyte for sodium secondary batteries, characterized by containing an alkane and having a value of n of 8 to 13. [2] The electrolyte according to [1], characterized in that the diluent comprises one or more of n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, 2,3-dimethylheptane, 3-methylheptane, 4-methylheptane, and 3-ethylhexane, and is selectively one or two of n-nonane and n-decane. [3] The electrolyte further comprises a cosolvent, the cosolvent comprising a compound represented by structural formula I, JPEG0007905528000011.jpg17166 Here, R 1 C 3-9 Selected from alkyl groups, R 2 C is halogen-substituted or unsubstituted. 1-3 The electrolyte according to [1] or [2], characterized in that it is selected from alkyl groups. [4] The above R 2 -CF 3 ,-CH 3 ,-CH 2 -CF 3 ,-CH 2 -CH 3 -CF 2 -CF 3 It includes one or more of the following, and optionally -CF 2 -CF 3 -CF 3 The electrolyte according to [3] above, characterized in that it is one or two of the above. [5] The electrolyte according to [3] or [4], characterized in that the cosolvent comprises one or more of methyl propyl ether, methyl butyl ether, methylheptyl ether, ethyl propyl ether, 2-ethoxybutane, ethylheptyl ether, ethyl amyl ether, methyl octyl ether, propyl butyl ether, propyl nonyl ether, trifluoromethylheptyl ether, 1,1,2,2,2-pentafluoroethylpropyl ether, and 2,2,2-trifluoroethylbutyl ether, and is selectively one or more of methyl butyl ether, methylheptyl ether, ethyl propyl ether, ethylheptyl ether, trifluoromethylheptyl ether, and 1,1,2,2,2-pentafluoroethylpropyl ether. [6] The electrolyte according to any one of the above items [3] to [5], characterized in that the molar ratio of the diluent to the cosolvent is 1:7 to 7:1, and selectively 1:5 to 5:1. [7] The electrolyte according to any one of the above [1] to [6], characterized in that the electrolyte contains an ethylene glycol ether solvent. [8] The electrolyte according to [7], characterized in that the molar ratio of the ethylene glycol ether solvent to the diluent is 1:5 to 3:1, and selectively 1:3 to 1:1. [9] The electrolyte according to [7] or [8], characterized in that the ethylene glycol ether solvent comprises one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether.

[10] The electrolyte according to any one of [1] to [9], wherein the electrolyte further comprises a sodium salt, the sodium salt comprising one or two of a first sodium salt and a second sodium salt, the first sodium salt comprising one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate, and the second sodium salt comprising one or more of sodium difluoro(oxalato)borate, sodium bis(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[11] The electrolyte according to

[10] , characterized in that the mass content of the first sodium salt is 3% to 40%, and selectively 5% to 30%, based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent.

[12] The electrolyte according to

[10] or

[11] , characterized in that the mass content of the second sodium salt is 0.1% or more, and selectively 1% or more, based on the total mass of the sodium salt, the ethylene glycol ether system and the cosolvent.

[13] A sodium secondary battery characterized by containing the electrolyte described in any one of the above items [1] to

[12] .

[14] The sodium secondary battery according to

[13] , wherein the secondary battery includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector.

[15] The surface density of the undercoating is 5 to 50 g / m². 2 The sodium secondary battery according to

[14] , characterized in that it is the sodium secondary battery described above.

[16] The sodium secondary battery according to

[14] or

[15] , characterized in that the undercoating comprises one or more of a carbon coating, an alloy coating, and a metal oxide coating, and is selectively a carbon coating.

[17] The sodium secondary battery according to any one of the above

[14] to

[16] , characterized in that the undercoating comprises one or more of superconducting carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[18] The sodium secondary battery according to any one of the above items

[13] to

[17] , characterized in that the sodium secondary battery is a sodium metal battery without a negative electrode.

[19] A power consumption device characterized by including a sodium secondary battery as described in any one of the above items

[13] to

[18] . [Explanation of Symbols]

[0183] 1. Battery pack, 2. Upper casing, 3. Lower casing, 4. Battery module, 5. Sodium secondary battery, 5. Case, 5. Electrode assembly, 5. Cover plate.

Claims

1. A sodium secondary battery comprising an electrolyte, wherein the electrolyte comprises a diluent, and the diluent is of general formula C n H 2n+2 It contains the alkane, and the value of n is 8 to 13. The electrolyte further comprises a cosolvent and an ethylene glycol ether-based solvent, the cosolvent comprising a compound represented by structural formula I, Here, R1 is selected from C3-9 alkyl groups, and R2 is selected from halogen-substituted or unsubstituted C1-3 alkyl groups. The electrolyte further comprises a sodium salt, the sodium salt comprising a first sodium salt, the first sodium salt comprising one or more of hexafluorophosphate sodium, tetrafluoroborate sodium, hexafluoroarsenate sodium, and trifluoroacetate sodium. Based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent, the mass content of the first sodium salt is 3% to 40%. A sodium secondary battery characterized by the following features.

2. The sodium secondary battery according to claim 1, characterized in that the diluent contains one or more of n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, 2,3-dimethylheptane, 3-methylheptane, 4-methylheptane, and 3-ethylhexane.

3. The sodium secondary battery according to Claim 1, characterized in that the diluent comprises one or two of n-nonane and n-decane.

4. The aforementioned R 2 is one or more of -CF 3 , -CH 3 , -CH 2 -CF 3 , -CH 2 -CH 3 , -CF 2 -CF 3 The sodium secondary battery according to claim 1, characterized by including one or more of these.

5. The sodium secondary battery according to Claim 1, characterized in that R2 includes one or two of -CF2, -CF3, and -CF3.

6. The sodium secondary battery according to claim 1, characterized in that the cosolvent contains one or more of the following: methyl propyl ether, methyl butyl ether, methylheptyl ether, ethyl propyl ether, 2-ethoxybutane, ethylheptyl ether, ethyl amyl ether, methyl octyl ether, propyl butyl ether, propyl nonyl ether, trifluoromethylheptyl ether, 1,1,2,2,2-pentafluoroethylpropyl ether, and 2,2,2-trifluoroethylbutyl ether.

7. The sodium secondary battery according to claim 1, characterized in that the cosolvent comprises one or more of methyl butyl ether, methylheptyl ether, ethyl propyl ether, ethylheptyl ether, trifluoromethylheptyl ether, and 1,1,2,2,2-pentafluoroethylpropyl ether.

8. The sodium secondary battery according to claim 1, characterized in that the molar ratio of the diluent to the cosolvent is 1:7 to 7:

1.

9. The sodium secondary battery according to claim 1, characterized in that the molar ratio of the diluent to the cosolvent is 1:5 to 5:

1.

10. The sodium secondary battery according to claim 1, characterized in that the molar ratio of the ethylene glycol ether solvent to the diluent is 1:5 to 3:

1.

11. The sodium secondary battery according to claim 1, characterized in that the molar ratio of the ethylene glycol ether solvent to the diluent is 1:3 to 1:

1.

12. The sodium secondary battery according to claim 1, characterized in that the ethylene glycol ether solvent comprises one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether.

13. The sodium secondary battery according to claim 1, characterized in that the mass content of the first sodium salt is 5% to 30% based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent.

14. The sodium secondary battery according to claim 1, wherein the sodium salt further comprises a second sodium salt, the second sodium salt comprising one or more of the following: sodium difluoro(oxalato)borate, sodium bis(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

15. The sodium secondary battery according to claim 14, characterized in that the mass content of the second sodium salt is 0.1% or more based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent.

16. The sodium secondary battery according to claim 14, characterized in that the mass content of the second sodium salt is 1% or more based on the total mass of the sodium salt, the ethylene glycol ether solvent, and the cosolvent.

17. The sodium secondary battery according to claim 1, wherein the secondary battery includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector.

18. The surface density of the undercoating is 5 to 50 g / m². 2 The sodium secondary battery according to claim 17, characterized in that it is the sodium secondary battery described in claim 17.

19. The sodium secondary battery according to claim 17, characterized in that the undercoating includes one or more of a carbon coating, an alloy coating, and a metal oxide coating.

20. The sodium secondary battery according to claim 17, characterized in that the undercoating includes a carbon coating.

21. The sodium secondary battery according to claim 17, characterized in that the undercoating comprises one or more of the following: superconducting carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

22. The sodium secondary battery according to claim 1, characterized in that the sodium secondary battery is a sodium metal battery without a negative electrode.

23. A power consumption device characterized by including a sodium secondary battery as described in claim 1.

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