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 consumption device. The sodium secondary battery electrolyte includes an additive, the additive including a fluoroether-based compound. The addition of the additive including a fluoroether-based compound to the electrolyte 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 the battery at high temperatures.

Description

[Technical Field]

[0001] 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.

[0002] [Cross-reference of related applications] This application invokes Chinese patent application No. 202310075482.6, 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 through such invocation. [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 project]

[0004] In light of the problems present in the background technology, this application provides an electrolyte for sodium secondary batteries that aims to improve the high-temperature cycling performance of sodium secondary batteries, reduce the high-temperature gas generation phenomenon of sodium secondary batteries, and improve 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 an additive, the additive comprising a fluoroether compound.

[0006] Fluoroether compounds have relatively low lowest empty molecular orbitals (LUMOs) and can be reduced on the negative electrode surface to produce SEI mainly composed of organic fluorides. This greatly enhances the structural stability and uniformity of the negative electrode surface SEI, reduces direct contact between the negative electrode and the solvent, decreases side reactions between the negative electrode and the solvent, improves the high-temperature cycling performance of sodium secondary batteries, reduces high-temperature gas generation phenomena in sodium secondary batteries, and improves the electrochemical and safety performance of sodium secondary batteries at high temperatures.

[0007] In any embodiment, the fluoroether compound comprises one or more compounds represented by formula I. TIFF0007898614000001.tif20150 Here, R1 and R2 are each independently selected from fluorine-substituted or unsubstituted C1-C6 alkyl groups, and at least one of R1 and R2 contains a fluorine atom.

[0008] In each embodiment, the fluoroether compound is 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1 The material comprises one or more of the following: 1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, and 2,2,2-trifluoroethyl ether, and is selectively one or more of the following: bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, ethyl perfluorobutyl ether, and ethyl nonafluorobutyl ether.

[0009] In each embodiment, the mass content of the additive is 0.2% to 10% of the total mass of the electrolyte, and selectively 0.5% to 6.5%.

[0010] When the mass content of the additive is within an appropriate range, the battery has excellent normal-temperature cycle performance and high-temperature cycle performance, has a low high-temperature gas generation amount, and broadens the operating temperature range of the battery.

[0011] In any of the embodiments, the electrolyte further includes a sodium salt and an ether-based solvent. Based on the total mass of the electrolyte, the mass content of the sodium salt is 3% to 40%, and optionally 5% to 30%.

[0012] When the mass content of the sodium salt is within an appropriate range, the battery has excellent normal-temperature cycle performance and high-temperature cycle performance, has a low high-temperature gas generation amount, and broadens the operating temperature range of the battery.

[0013] When the electrolyte includes an ether-based solvent, the normal-temperature cycle performance and high-temperature cycle performance of the battery can be improved, the high-temperature gas generation phenomenon of the battery can be reduced, and the electrochemical performance and safety performance of the battery can be improved.

[0014] In any of the embodiments, the sodium salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate.

[0015] In any of the embodiments, the ether-based 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, ethylene glycol dibutyl ether, tetrahydrofuran, and methyltetrahydrofuran, and optionally one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0016] In any of the embodiments, the electrolyte further includes a lithium salt.

[0017] The electrolyte contains a lithium salt, thereby improving the normal-temperature cycle performance and high-temperature cycle performance of the battery, reducing the high-temperature gas generation phenomenon of the battery, and improving the electrochemical performance and safety performance of the battery.

[0018] In any embodiment, the lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoroacetate, lithium tetraphenylborate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0019] The second aspect of the present application provides a sodium secondary battery, and the sodium secondary battery includes the electrolyte of the first aspect.

[0020] In any embodiment, the sodium 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. The sodium secondary battery satisfies the relational expression of 0.3 ≦ Z - 0.01X ≦ 6. Here, based on the total mass of the electrolyte, X g / m is the surface density of the undercoating, and Z% is the mass content of the additive.

[0021] By controlling the surface density X g / m of the undercoating on at least one side of the negative electrode current collector and the mass content Z% based on the total mass of the electrolyte of the additive to satisfy 0.3 ≦ Z - 0.01X ≦ 6, the high-temperature cycle performance of the battery can be improved, the high-temperature gas generation phenomenon of the battery can be reduced, and the operating temperature range of the battery can be widened. ​​​​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, and the electrolyte includes a lithium salt. A sodium secondary battery satisfies the relationship 0.84 ≤ Y - 0.01X ≤ 5.84. Here, using the total mass of electrolytes as a reference, X g / m³ 2 is the surface density of the undercoating, and Y% is the mass content of the lithium salt.

[0023] Surface density X g / m² of the undercoating on at least one side of the negative electrode current collector 2 By controlling the mass content Y% of the lithium salt electrolyte, based on the total mass of the electrolyte, so that it satisfies the relationship 0.84 ≤ Y - 0.01X ≤ 5.84, the room temperature cycle performance and high temperature cycle performance of the battery can be improved, the high-temperature gas generation phenomenon of the battery can be reduced, and the electrochemical performance and safety performance of the battery can be improved.

[0024] In each embodiment, the surface density of the undercoating is 5 to 50 g / m². 2 That is the case.

[0025] By ensuring the undercoating surface density is within an appropriate range, the battery's room-temperature and high-temperature cycle performance can be improved, the high-temperature gas generation phenomenon in the battery can be reduced, and the battery's electrochemical and safety performance can be enhanced.

[0026] 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.

[0027] In any embodiment, the undercoating includes one or more of the following: superconducting carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[0028] In each embodiment, the sodium secondary battery is a sodium metal battery without a negative electrode.

[0029] Sodium secondary batteries are non-negative 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.

[0030] A third aspect of this application provides a battery module which includes a sodium secondary battery according to the second aspect.

[0031] 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.

[0032] 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]

[0033] [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]

[0034] The following describes in detail embodiments of the 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.

[0035] 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 an abbreviated representation of 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.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0037] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts.

[0038] 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.

[0039] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the conditions A is true (or exists) and B is false (or does not exist), the condition A is false (or does not exist) but B is true (or exists), and the condition both A and B are true (or exist) all satisfy "A or B."

[0040] Under high-temperature conditions, inorganic components in the solid electrolyte interface (SEI) of a sodium secondary battery dissolve, causing the SEI to exhibit a porous structure. The electrolyte continuously decomposes on the negative electrode surface, and the SEI continues to decompose and regenerate, constantly consuming the limited sodium resources inside the sodium secondary battery. This increases the self-discharge of the sodium secondary battery and worsens its cycle performance. Simultaneously, under high-temperature conditions, chemical reactions occur between the positive and negative electrodes of the sodium secondary battery and the electrolyte. These reactions release heat, generate gas, cause volume expansion of the battery, and in severe cases, can lead to short circuits within the battery, reducing the safety performance of the sodium secondary battery and severely limiting its applications.

[0041] [Electrolyte for sodium-based secondary batteries] This application provides an electrolyte for a sodium secondary battery, the electrolyte comprising an additive, the additive comprising a fluoroether compound.

[0042] In this specification, the term "sodium secondary battery" refers to a secondary battery that uses sodium ions as charge carriers, and the negative electrode active material of a sodium secondary battery includes carbon-based materials, titanium-based materials, alloy materials, layered transition metal oxides, layered transition metal selenides, organic materials, or metallic sodium. Here, a sodium secondary battery in which metallic sodium is the negative electrode active material is referred to as a sodium metal battery.

[0043] In some embodiments, the negative electrode active material of a sodium secondary battery includes one or more of graphite-based carbon materials, amorphous carbon materials, and nanocarbon materials.

[0044] In some embodiments, the negative electrode active material of a sodium secondary battery is hard carbon.

[0045] In some embodiments, the negative electrode active material of a sodium secondary battery is metallic sodium.

[0046] 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.

[0047] 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.

[0048] In this specification, the term "additive" refers to a component present in relatively small amounts in an electrolyte, and may be a gas, liquid, or solid. Conceptually speaking, the only difference between an additive, a solvent, and a sodium salt is the amount present in the electrolyte.

[0049] In this specification, the term "fluoroether compound" refers to a compound obtained after modifying an ether compound by direct fluorine substitution.

[0050] Fluoroether compounds have relatively low lowest empty molecular orbitals (LUMOs), preferentially undergoing redepository reactions with sodium salts over solvents, producing highly thermally stable organic fluorides and forming structurally stable and uniformly distributed SEI on the negative electrode surface. SEI containing a large amount of fluoride is less susceptible to secondary decomposition and regeneration, reducing sodium consumption inside the sodium secondary battery and improving the high-temperature cycle performance of the sodium secondary battery. Furthermore, structurally stable and uniformly distributed SEI reduces direct contact between the electrolyte and the negative electrode, decreasing side reactions between the electrolyte and the negative electrode, suppressing hydrogen gas generation during high-temperature cycling of the sodium secondary battery, and improving the high-temperature gas generation phenomenon of the sodium secondary battery.

[0051] In some embodiments, the fluoroether compound comprises one or more compounds represented by formula I. TIFF0007898614000002.tif20150 Here, R1 and R2 are each independently selected from fluorine-substituted or unsubstituted C1-C6 alkyl groups, and at least one of R1 and R2 contains a fluorine atom.

[0052] In this specification, the term "C1-C6 alkyl group" refers to a linear or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, the group being unsaturated, having 1 to 6 carbon atoms, and attached to the rest of the molecule via single bonds.

[0053] In this specification, the term "fluorine substitution" means that at least one hydrogen atom of the compound or chemical moiety is substituted with a fluorine atom or a fluorinated alkyl group.

[0054] In this specification, the term "fluorinated alkyl group" refers to an alkyl group containing at least one fluorine atom.

[0055] In some embodiments, the fluoroether compounds are 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoro This includes one or more of the following: ethyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1,1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, and 2,2,2-trifluoroethyl ether.

[0056] In some embodiments, the fluoroether compound includes one or more of bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, ethyl perfluorobutyl ether, and ethyl nonafluorobutyl ether.

[0057] In some embodiments, the mass content of the additive is 0.2% to 10% relative to the total mass of the electrolyte. In some embodiments, the mass content of the additive is selectively 0.2% to 0.5%, 0.2% to 1%, 0.2% to 1.5%, 0.2% to 2%, 0.2% to 2.5%, 0.2% to 3%, 0.2% to 3.5%, 0.2% to 4%, 0.2% to 4.5%, 0.2% to 5%, 0.2% to 5.5%, 0.2% to 6%, 0.2% to 6.5%, 0.2% to 7%, 0.2% to 7.5%, 0.2% to 8%, 0.2% to 8.5%, 0.2% to 9%, 0.2% to 9.5%, 0.2% to 10%, 0.5% to 1%, and 0.5%. %~1.5%, 0.5%~2%, 0.5%~2.5%, 0.5%~3%, 0.5%~3.5%, 0.5%~4%, 0.5%~4.5%, 0.5%~5%, 0.5%~5.5%, 0.5%~6%, 0.5%~6.5%, 0.5%~7%, 0.5%~7.5%, 0.5%~8%, 0.5%~8.5%, 0.5%~9%, 0.5%~9.5%, 0.5%~10%, 1%~1.5%, 1%~2%, 1%~2.5%, 1%~3%, 1%~3.5%, 1%~4%, 1%~4.5%, 1%~5%, 1%~5.5%, 1%~6%, 1%~6.5 %, 1%~7%, 1%~7.5%, 1%~8%, 1%~8.5%, 1%~9%, 1%~9.5%, 1%~10%, 1.5%~2%, 1.5%~2.5%, 1.5%~3%, 1.5%~3.5%, 1.5%~4%, 1.5%~4.5%, 1.5%~5%, 1.5%~5.5%, 1.5%~6%, 1.5%~6.5%, 1.5%~7%, 1.5%~7.5%, 1.5%~8%, 1.5%~8.5%, 1.5%~9%, 1.5%~9.5%, 1.5%~10%, 2%~2.5%, 2%~3%, 2%~3.5%, 2%~4%, 2%~ 4.5%, 2%~5%, 2%~5.5%, 2%~6%, 2%~6.5%, 2%~7%, 2%~7.5%, 2%~8%, 2%~8.5%, 2%~9%, 2%~9.5%, 2%~10%, 2.5%~3%, 2.5%~3.5%, 2.5%~4%, 2.5%~4.5%, 2.5%~5%, 2.5%~5.5%, 2.5%~6%, 2.5%~6.5%, 2.5%~7%, 2.5%~7.5%, 2.5%~8%, 2.5%~8.5%, 2.5%~9%, 2.5%~9.5%, 2.5%~10%, 3%~3.5%, 3%~4%, 3%~4.5%, 3%~5%, 3%~5.5%, 3%~6%, 3%~6.5%, 3%~7%, 3%~7.5%, 3%~8%, 3%~8.5%, 3%~9%, 3%~9.5%, 3%~10%, 3.5%~4%, 3.5%~4.5%, 3.5%~5%, 3.5%~5.5%, 3.5%~6%, 3.5%~6.5%, 3.5%~7%, 3.5%~7.5%, 3.5%~8%, 3.5%~8.5%, 3.5%~9%, 3.5%~9.5%, 3.5%~10%, 4%~4.5%, 4%~ 5%, 4%~5.5%, 4%~6%, 4%~6.5%, 4%~7%, 4%~7.5%, 4%~8%, 4%~8.5%, 4%~9%, 4%~9.5%, 4%~10%, 4.5%~5%, 4.5%~5.5%, 4.5%~6%, 4.5%~6.5%, 4.5%~7%, 4.5%~7.5%, 4.5%~8%, 4.5%~8.5%, 4.5%~9%, 4.5%~9.5%, 4.5%~10%, 5%~5.5%, 5%~6%, 5%~6.5%, 5%~7%, 5%~7.5%, 5%~8%, 5%~8.5%, 5%~9%, 5%~9.5%, 5%~10%, 5.5%~6%, 5.5%~6.5%, 5.5%~7%, 5.5%~7.5%, 5.5%~8%, 5.5%~8.5%, 5.5%~9%, 5.5%~9.5%, 5.5%~10%, 6%~6.5%, 6%~7%, 6%~7.5%, 6%~8%, 6%~8.5%, 6%~9%, 6%~9.5%, 6%~10%, 6.5%~7%, 6.5%~7.5%, 6.5%~8%, 6.5%~8.5% It is one of the following percentages: 6.5%~9%, 6.5%~9.5%, 6.5%~10%, 7%~7.5%, 7%~8%, 7%~8.5%, 7%~9%, 7%~9.5%, 7%~10%, 7.5%~8%, 7.5%~8.5%, 7.5%~9%, 7.5%~9.5%, 7.5%~10%, 8%~8.5%, 8%~9%, 8%~9.5%, 8%~10%, 8.5%~9%, 8.5%~9.5%, 8.5%~10%, 9%~9.5%, 9%~10%, or 9.5%~10%.

[0058] By ensuring that the additive's mass content is within an appropriate range, a uniformly structured and uniformly distributed SEI is formed on the negative electrode surface, further guaranteeing that the battery has low interfacial impedance and that the SEI has excellent sodium ion transport performance. As a result, the battery has excellent room temperature and high temperature cycling performance, low high-temperature gas generation, and a wide operating temperature range.

[0059] In some embodiments, the mass content of the additive is 0.5% to 6.5% relative to the total mass of the electrolyte. In some embodiments, the mass content of the additive is selectively 0.5% to 1%, 0.5% to 1.5%, 0.5% to 2%, 0.5% to 2.5%, 0.5% to 3%, 0.5% to 3.5%, 0.5% to 4%, 0.5% to 4.5%, 0.5% to 5%, 0.5% to 5.5%, 0.5% to 6%, 0.5% to 6.5%, 1% to 1.5%, 1% to 2%, and 1% to 2.5% relative to the total mass of the electrolyte. , 1%~3%, 1%~3.5%, 1%~4%, 1%~4.5%, 1%~5%, 1%~5.5%, 1%~6%, 1%~6.5%, 1.5%~2%, 1.5%~2.5%, 1.5%~3%, 1.5%~3.5%, 1.5%~4%, 1.5%~4.5%, 1.5%~5%, 1.5%~5.5%, 1.5%~6%, 1.5%~6.5%, 2%~2.5%, 2%~3%, 2%~3.5%, 2%~4 %, 2%~4.5%, 2%~5%, 2%~5.5%, 2%~6%, 2%~6.5%, 2.5%~3%, 2.5%~3.5%, 2.5%~4%, 2.5%~4.5%, 2.5%~5%, 2.5%~5.5%, 2.5%~6%, 2%~6.5%, 3%~3.5%, 3%~4%, 3%~4.5%, 3%~5%, 3%~5.5%, 3%~6%, 3%~6.5%, 3.5%~4%, 3.5%~4 It is one of the following: 0.5%, 3.5%~5%, 3.5%~5.5%, 3.5%~6%, 3.5%~6.5%, 4%~4.5%, 4%~5%, 4%~5.5%, 4%~6%, 4%~6.5%, 4.5%~5%, 4.5%~5.5%, 4.5%~6%, 4.5%~6.5%, 5%~5.5%, 5%~6.5%, 5%~6%, 5.5%~6%, 5.5%~6.5%, or 6%~6.5%.

[0060] By ensuring that the mass content of the additive is within an appropriate range, a uniformly structured and uniformly distributed SEI is formed on the negative electrode surface, further guaranteeing that the battery has low interfacial impedance, and enabling the SEI to have excellent sodium ion transport performance. This improves the high-temperature cycle performance of the battery, reduces high-temperature gas generation phenomena, and improves the electrochemical and safety performance of the battery at high temperatures.

[0061] In some embodiments, the electrolyte further comprises a sodium salt and an ether-based solvent.

[0062] In some embodiments, the sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate.

[0063] In some embodiments, the 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, ethylene glycol dibutyl ether, tetrahydrofuran, and methyltetrahydrofuran.

[0064] In some embodiments, the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0065] Molecules of ether-based solvents can construct a stable electrode / electrolyte interface on the negative electrode surface, form a stable SEI, reduce electrochemical polarization, improve the room-temperature and high-temperature cycling performance of the battery, reduce high-temperature gas generation, and improve the electrochemical performance and safety of the battery. At the same time, both ether-based solvents and fluoroether-based compounds contain ether bonds, which can improve the stability of the system.

[0066] In some embodiments, the mass content of sodium salt is 3% to 40% relative to the total mass of the electrolyte. In some embodiments, the mass content of 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%, 10% to 15%, and 10% to 20% relative to the total mass of the electrolyte. It is one of the following percentages: 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%~40%.

[0067] By having an appropriate mass content of sodium salts, the electrolyte has appropriate viscosity and excellent ionic conductivity, the battery has excellent room temperature and high temperature cycle performance, low high-temperature gas generation, and extends the operating temperature range of the battery.

[0068] In some embodiments, the mass content of sodium salt is 5% to 30% relative to the total mass of the electrolyte. In some embodiments, the mass content of sodium salt is selectively one of the following, relative to the total mass of the electrolyte: 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%.

[0069] By ensuring the sodium salt mass content is within an appropriate range, the electrolyte can possess appropriate viscosity and excellent ionic conductivity, improving the battery's room-temperature and high-temperature cycle performance, reducing high-temperature gas generation, and enhancing the battery's electrochemical and safety performance.

[0070] In some embodiments, the electrolyte further comprises a lithium salt.

[0071] In some embodiments, the lithium salt includes one or more of the following: lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoroacetate, lithium tetraphenylborate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0072] Taking a sodium metal battery as an example, the introduction of lithium ions can also effectively suppress the growth of sodium dendrites during the sodium metal deposition process. During the charging process of a sodium metal battery, an electrochemical reaction occurs at the negative electrode in which sodium ions gain electrons and are converted back into sodium metal. In the initial stages of the reaction, sodium metal is unevenly deposited on the surface of the current collector, forming dendrites, and the tips of the dendrites have a relatively high negative charge density due to the tip effect. On the other hand, both lithium ions and sodium ions are positively monovalent cations and have one unit of positive charge, but because lithium ions have a smaller radius, they have a higher positive charge density and are distributed to the tips of the dendrites before sodium ions. This effectively reduces the continuous deposition of sodium ions at the tips of sodium dendrites, suppresses the growth of sodium dendrites, and further greatly improves the battery's cycle performance.

[0073] The electrolyte contains lithium salts, which improves the battery's room-temperature and high-temperature cycle performance, reduces high-temperature gas generation, and enhances the battery's electrochemical and safety performance.

[0074] [Sodium secondary battery] This application provides a sodium secondary battery, the sodium secondary battery comprising an electrolyte in any of the embodiments.

[0075] 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. A sodium secondary battery satisfies the relationship 0.3 ≤ Z - 0.01X ≤ 6. Here, using the total mass of electrolytes as a reference, X g / m³ 2 is the surface density of the undercoating, and Z% is the mass content of the additive.

[0076] 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.

[0077] 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 the metal deposition / dissolution process brings to the battery core, 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.

[0078] Taking a non-negative metal battery as an example, during the initial charging process, the additive first undergoes re-decomposition on the undercoating of the current collector surface, and some of the decomposition products accumulate on the undercoating to form SEI. During the discharge process, metallic sodium is converted back into sodium ions and returns to the positive electrode, enabling cyclic charging and discharging.

[0079] The applicant has determined the undercoating surface density of sodium secondary batteries to be X g / m². 2By controlling the mass content Z% of the additive, based on the total electrolyte mass, within the numerical range of 0.3 ≤ Z - 0.01X ≤ 6, we unexpectedly discovered that the synergistic effect between the undercoating and the additive improves the stability and uniformity of the SEI, further enhancing the high-temperature cycle performance of the battery, reducing high-temperature gas generation, and expanding the battery's operating temperature range.

[0080] 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. For sodium-ion secondary batteries, the following ranges apply: 0.3≦Z-0.01X≦0.5, 0.3≦Z-0.01X≦1, 0.3≦Z-0.01X≦1.5, 0.3≦Z-0.01X≦2, 0.3≦Z-0.01X≦2.5, 0.3≦Z-0.01X≦3, 0.3≦Z-0.01X≦3.5, 0.3≦Z-0.01X≦4, 0.3≦Z-0.01X≦4.5, 0.3≦Z-0.01X≦5, 0.3≦Z-0.01X≦5.5, 0.3≦Z-0.01X≦6, 0.5≦Z-0.01X≦1, 0.5≦Z-0.01X≦1.5, 0.5≦Z-0.01X≦2, 0.5≦Z-0.01X≦2. 5, 0.5≦Z-0.01X≦3, 0.5≦Z-0.01X≦3.5, 0.5≦Z-0.01X≦4, 0.5≦Z-0.01X≦4.5, 0.5≦Z-0.01X≦5, 0.5≦Z-0.01X≦5.5, 0.5≦Z-0.01X≦6, 1≦Z-0.01X≦1.5, 1≦Z-0 .01X≦2, 1≦Z-0.01X≦2.5, 1≦Z-0.01X≦3, 1≦Z-0.01X≦3.5, 1≦Z-0.01X≦4, 1≦Z-0.01X≦4.5, 1≦Z-0.01X≦5, 1≦Z-0.01X≦5.5, 1≦Z-0.01X≦6, 1.5≦Z-0.01X≦2, 1.5≦Z-0.01X≦2.5, 1.5≦Z-0.01X≦3, 1.5≦Z-0.01X≦3.5, 1.5≦Z-0.01X≦4, 1.5≦Z-0.01X≦4.5, 1.5≦Z-0.01X≦5, 1.5≦Z-0.01X≦5.5, 1.5≦Z-0.01X≦6, 2≦Z-0 .01X≦2.5, 2≦Z-0.01X≦3, 2≦Z-0.01X≦3.5, 2≦Z-0.01X≦4, 2≦Z-0.01X≦4.5, 2≦Z-0.01X≦5, 2≦Z-0.01X≦5.5, 2≦Z-0.01X≦6, 2.5≦Z-0.01X≦3, 2.5≦Z-0.01X≦ 3.5, 2.5≦Z-0.01X≦4, 2.5≦Z-0.01X≦4.5, 2.5≦Z-0.01X≦5, 2.5≦Z-0.01X≦5.5, 2.5≦Z-0.01X≦6, 3≦Z-0.01X≦3.5, 3≦Z-0.01X≦4, 3≦Z-0.01X≦4.5, 3≦Z-0.0 1X≦5, 3≦Z-0.01X≦5.5, 3≦Z-0.01X≦6, 3.5≦Z-0.01X≦4, 3.5≦Z-0.01X≦4.5, 3.5≦Z-0.01X≦5, 3.5≦Z-0.01X≦5.5, 3.5≦Z-0.01X≦6, 4≦Z-0.01X≦4.5, 4≦Z-0.Any one of the relational expressions of 01X≦5, 4≦Z - 0.01X≦5.5, 4≦Z - 0.01X≦6, 4.5≦Z - 0.01X≦5, 4.5≦Z - 0.01X≦5.5, 4.5≦Z - 0.01X≦6, 5≦Z - 0.01X≦5.5, 5≦Z - 0.01X≦6, 5.5≦Z - 0.01X≦6 is satisfied, and... Here, based on the total mass of the electrolyte, X g / m 2 is the surface density of the undercoating, and Z% is the mass content of the additive.

[0081] 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, the electrolyte includes a lithium salt, and the sodium secondary battery satisfies the relational expression of 0.84≦Y - 0.01X≦5.84, Here, based on the total mass of the electrolyte, X g / m 2 is the surface density of the undercoating, and Y% is the mass content of the lithium salt.

[0082] In some embodiments, the sodium secondary battery includes a negative electrode plate, the electrolyte includes a lithium salt, 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, and the sodium secondary battery has the following properties: 0.84≦Y-0.01X≦5.84, 0.84≦Y-0.01X≦1.84, 0.84≦Y-0.01X≦2.84, 0.84≦Y-0.01X≦3.84, 0.84≦Y-0.01X≦4.84, 0.84≦Y-0.01X≦5.84, 1.84≦Y-0.01X≦2.84, 1.84≦Y-0.01X≦3.84, 1.84≦Y-0.01X≦4.84, 1.84≦Y-0.01X≦5.84, 2.84≦Y-0.01X≦3.84, 2.84≦Y-0.01X≦4.84, 2.84≦Y-0.01X≦5.84, 3.84≦Y-0.01X≦4.84, 3.84≦Y-0.01X≦5.84 , 4.84≦Y-0.01X≦5.84, 0.84≦Y-0.01X≦1.5, 0.84≦Y-0.01X≦2, 0.84≦Y-0.01X≦2.5, 0.84≦Y-0.01X≦3, 0.84≦Y-0.01X≦3.5, 0.84≦Y-0.01X≦4, 0.84≦Y-0.0 1X≦4.5, 0.84≦Y-0.01X≦5, 1.84≦Y-0.01X≦5.5, 1.5≦Y-0.01X≦2, 1.5≦Y-0.0 1X≦2.5, 1.5≦Y-0.01X≦3, 1.5≦Y-0.01X≦3.5, 1.5≦Y-0.01X≦4, 1.5≦Y-0.01X ≤4.5, 1.5≦Y-0.01X≦5, 1.5≦Y-0.01X≦5.5, 2≦Y-0.01X≦2.5, 2≦Y-0.01X≦3, 2≦Y-0.01X≦3.5, 2≦Y-0.01X≦4, 2≦Y-0.01X≦4.5, 2≦Y-0.01X≦5, 2≦Y-0.01X≦5. 5, 2.5≦Y-0.01X≦3, 2.5≦Y-0.01X≦3.5, 2.5≦Y-0.01X≦4, 2.5≦Y-0.01X≦4.5, 2.5≦Y-0.01X≦5, 2.5≦Y-0.01X≦5.5, 3≦Y-0.01X≦3.5, 3≦Y-0.01X≦4, 3≦Y-0.0 1X≦4.5, 3≦Y-0.01X≦5, 3≦Y-0.01X≦5.5, 3.5≦Y-0.01X≦4, 3.5≦Y-0.01X≦4.5, 3.5≦Y-0.01X≦5, 3.5≦Y-0.01X≦5.5, 4≦Y-0.01X≦4.5, 4≦Y-0.01X≦5, 4≦Y-0.The following conditions must be met: 01X ≤ 5.5, 4.5 ≤ Y - 0.01X ≤ 5, 4.5 ≤ Y - 0.01X ≤ 5.5, or 5 ≤ Y - 0.01X ≤ 5.5. Here, using the total mass of electrolytes as a reference, X g / m³ 2 is the surface density of the undercoating, and Y% is the mass content of the lithium salt.

[0083] An undercoat containing free electrons electrostatically adsorbs lithium ions with a relatively high positive charge density, and the deposition of lithium ions on the undercoat via the SEI layer effectively reduces the overpotential of sodium metal deposition, suppresses the formation of sodium dendrites, and is advantageous for improving the battery's cycle performance.

[0084] The applicant has determined the undercoating surface density of secondary batteries to be X g / m². 2 We unexpectedly discovered that by controlling the mass content Y% of the lithium salt, based on the total electrolyte mass, within the numerical range of 0.84 ≤ Y - 0.01X ≤ 5.84, the synergistic effect between the undercoating and the lithium salt improves the stability and uniformity of SEI, further enhancing the battery's room-temperature and high-temperature cycle performance, reducing high-temperature gas generation, and improving the battery's electrochemical and safety performance.

[0085] In some embodiments, the surface density of the undercoating is 5-50 g / m². 2 That is the case.

[0086] 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 / m2 , 20-50g / m 2 30-40g / m 2 30-50g / m 2 40-50g / m 2 It is one of the following.

[0087] An appropriate undercoating density improves the battery's room-temperature and high-temperature cycling performance and reduces high-temperature gas generation. Simultaneously, an appropriate undercoating density increases the battery's energy density, meeting its usage demands.

[0088] In some embodiments, the undercoating includes one or more of a carbon coating, an alloy coating, and a metal oxide coating.

[0089] In some embodiments, the undercoating includes a carbon coating.

[0090] In some embodiments, the undercoating includes one or more of the following: superconducting carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[0091] 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.

[0092] 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.

[0093] In some embodiments, the undercoating is an alloy coating, and the alloy is one of Au, Ag, Sn, or Sb. two Includes alloys consisting of one or more metals.

[0094] In some embodiments, the undercoating is a metal oxide coating, and the oxide comprises at least one of copper oxide and aluminum oxide.

[0095] In some embodiments, the undercoating is a conductive polymer coating, the conductive polymer comprising one of polyaniline, polythiophene, polypyrrole, or polyphenylenevinylene.

[0096] In some embodiments, the undercoating is a conductive ceramic coating, and the conductive ceramic material comprises at least one of TiB2, TiC, and B4C3.

[0097] 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.

[0098] In some embodiments, the sodium secondary battery is a sodium metal battery without a negative electrode.

[0099] In some embodiments, the 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.

[0100] A negative electrode sodium metal battery can improve the battery's room temperature and high temperature cycle performance, reduce high-temperature gas generation, and improve the battery's electrochemical and safety performance at high temperatures.

[0101] In some embodiments, the CB value of the non-negative electrode sodium metal battery is 0.1 or less.

[0102] 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.

[0103] 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.

[0104] [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.

[0105] 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。

[0106] 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.

[0107] Prussian blue compounds may be compounds having sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds may include, 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。

[0108] 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.

[0109] 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).

[0110] 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.

[0111] 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.

[0112] [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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] As the power consumption device, a sodium secondary battery, a battery module, or a battery pack can be selected according to the usage demand.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 1. Manufacturing method Example 1 1) Manufacturing of electrolytes In an argon gas-atmosphered glove box with a moisture content of <10 ppm, sodium hexafluorophosphate (sodium salt), lithium hexafluorophosphate (lithium salt), and the additive methyl nonafluorobutyl ether were added to an ethylene glycol dimethyl ether solvent. Based on the total mass of the electrolyte, the mass content of sodium hexafluorophosphate was 15%, the mass content of lithium hexafluorophosphate was 3%, and the mass content of methyl nonafluorobutyl ether was 2%.

[0130] 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 aluminum foil surface 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. 3 The final positive electrode plate was obtained by cold pressing at the design pressure density during manufacturing.

[0131] 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 an aluminum foil 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 Okay.

[0132] 4) Separator A polyethylene film (PE separator) was used as the separator.

[0133] 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.

[0134] Examples 2-29 Aside from differences in the electrolyte composition and / or the manufacturing parameters of the negative electrode plate, the other steps in Examples 2 to 29 are the same as in Example 1, where the manufacturing methods for the negative electrode plate in Examples 24 and 25 are as follows, and the specific parameters are shown in Table 1.

[0135] Example 24: 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 (SBCs), 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.

[0136] Example 25: The negative electrode plate is aluminum foil.

[0137] Comparative Examples 1-5 Aside from differences in the electrolyte composition and / or the manufacturing parameters of the negative electrode plate, the other steps in Comparative Examples 1 to 3 are the same as in Example 1, where Comparative Example 4 is the same as the negative electrode plate manufacturing method of Example 24, and Comparative Example 5 is the same as the negative electrode plate manufacturing method of Example 25, with the specific parameters shown in Table 1.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] The test procedures for the comparative examples and other examples are the same as described above.

[0142] III. Test Results The test results for the above examples and comparative examples are shown in Table 1.

[0143] [Table 1-1] [Table 1-2] [Table 1-3]

[0144] As can be seen from the above results, the electrolytes for sodium secondary batteries in Examples 1 to 29 all contain additives, and the additives include one or more of the following: methyl nonafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis-(2,2,2-trifluoroethyl) ether, and 2,2,3,3-tetrafluoropropyl methyl ether.

[0145] As can be seen from the comparison between Examples 1-8, 11-23, 26-29 and Comparative Example 1, Example 10 and Comparative Example 2, Example 9 and Comparative Example 3, and Examples 24-25 and Comparative Examples 4-5, the additive 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.

[0146] As can be seen from Examples 1 to 29, the mass content of the additive was 0.2% to 10% based on the total mass of the electrolyte, and the battery had excellent room temperature cycling performance and high temperature cycling performance, low high-temperature gas generation, and extended the operating temperature range of the battery.

[0147] As can be seen from the comparison between Examples 1, 26-27 and Examples 28-29, the mass content of the additive was 0.5% to 6.5% based on the total mass of the electrolyte, which improved the 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.

[0148] The electrolytes in Examples 1-29 further contained a sodium salt, which included sodium hexafluorophosphate (NaPF6) or sodium tetrafluoroborate (NaBF4). The mass content of the sodium salt was 3% to 40% of the total mass of the electrolyte. The batteries exhibited excellent room-temperature and high-temperature cycling performance, low high-temperature gas generation, and a wide operating temperature range.

[0149] As can be seen from the comparison between Examples 1, 3-4 and Examples 2 and 5, the mass content of sodium salt was 5% to 30% based on the total mass of the electrolyte, 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.

[0150] As can be seen from the comparison between Examples 1, 7-8 and Example 9, the electrolyte contains an ether-based solvent, and the ether-based solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol diethyl ether. This 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.

[0151] As can be seen from the comparison between Examples 1, 11-12 and Example 10, the electrolyte further contains a lithium salt, and the lithium salt includes lithium hexafluorophosphate (LiPF6), lithium difluoro(oxalato)borate (LiODFB), or lithium bis(fluorosulfonyl)imide (LiFSI). This further improves the room temperature cycle performance and 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 the battery.

[0152] As can be seen from the comparison between Examples 1 and 24 and Example 25, by installing an undercoating on at least one side of the negative electrode current collector, the undercoating, which includes a carbon coating, was able 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.

[0153] As can be seen from the comparison between Examples 1, 26-27 and Examples 28-29, the surface density X g / m² of the undercoating on at least one side of the negative electrode current collector. 2 By controlling the mass content Z% of the additive, based on the total electrolyte mass, so that 0.3 ≤ Z - 0.01X ≤ 6, we were able to improve the high-temperature cycle performance of the battery, reduce the high-temperature gas generation phenomenon of the battery, and extend the operating temperature range of the battery.

[0154] As can be seen from the comparison between Examples 1, 16-17 and Examples 18-19, the surface density X g / m² of the undercoating on at least one side of the negative electrode current collector. 2 By controlling the mass content Y% of the lithium salt electrolyte, based on the total mass of the electrolyte, so that it satisfies the relationship 0.84 ≤ Y - 0.01X ≤ 5.84, we were able to 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 and safety performance of the battery.

[0155] As can be seen from the comparison between Examples 1, 20-21 and Examples 22-23, the surface density of the undercoating is 5-50 g / m². 2As 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.

[0156] As can be seen from the comparison between Example 1 and Example 24, 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 at high temperatures.

[0157] 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. [Explanation of Symbols]

[0158] 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. An electrolyte for a sodium secondary battery, comprising an additive and an ether-based solvent, wherein the additive comprises a fluoroether-based compound. The fluoroether compound comprises one or more compounds represented by formula I, Here, R1 and R2 are each independently selected from fluorine-substituted or unsubstituted C1-C6 alkyl groups, and at least one of R1 and R2 contains a fluorine atom. The electrolyte for a sodium secondary battery is characterized in that the ether-based solvent contains one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran, and methyltetrahydrofuran.

2. The aforementioned fluoroether compounds are 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3, The electrolyte according to claim 1, characterized by comprising one or more of the following: 3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1,1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, and 2,2,2-trifluoroethyl ether.

3. The electrolyte according to claim 1, characterized in that the fluoroether compound comprises one or more of bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, ethyl perfluorobutyl ether, and ethyl nonafluorobutyl ether.

4. The electrolyte according to claim 1, characterized in that the mass content of the additive is 0.2% to 10% based on the total mass of the electrolyte.

5. The electrolyte according to claim 1, characterized in that the mass content of the additive is 0.5% to 6.5% based on the total mass of the electrolyte.

6. The electrolyte according to claim 1, wherein the electrolyte further contains a sodium salt, and the mass content of the sodium salt is 3% to 40% based on the total mass of the electrolyte.

7. The electrolyte according to claim 1, wherein the electrolyte further contains a sodium salt, and the mass content of the sodium salt is 5% to 30% based on the total mass of the electrolyte.

8. The electrolyte according to claim 6, characterized in that the sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate.

9. The electrolyte according to claim 1, characterized in that the ether-based solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

10. The electrolyte according to claim 1, characterized in that the electrolyte further comprises a lithium salt.

11. The electrolyte according to claim 10, characterized in that the lithium salt comprises one or more of the following: lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoroacetate, lithium tetraphenylborate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

12. A sodium secondary battery, characterized in that it contains the electrolyte described in any one of claims 1 to 11.

13. 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, The aforementioned sodium secondary battery satisfies the relationship 0.3 ≤ Z - 0.01X ≤ 6. Here, based on the total mass of the electrolyte, X g / m 2 The sodium secondary battery according to claim 12, wherein is the surface density of the undercoating, and Z% is the mass content of the additive.

14. 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, and the electrolyte includes a lithium salt. The aforementioned sodium secondary battery satisfies the relationship 0.84 ≤ Y - 0.01X ≤ 5.

84. Here, based on the total mass of the electrolyte, X g / m 2 The sodium secondary battery according to claim 12, wherein is the surface density of the undercoating, and Y% is the mass content of the lithium salt.

15. The surface density of the undercoating is 5 to 50 g / m². 2 The sodium secondary battery according to feature 13.

16. The sodium secondary battery according to claim 13, characterized in that the undercoating is one or more of a carbon coating, an alloy coating, and a metal oxide coating.

17. The sodium secondary battery according to claim 13, characterized in that the undercoating is a carbon coating.

18. The sodium secondary battery according to claim 13, characterized in that the undercoating comprises one or more of the following: superconducting carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

19. The sodium secondary battery according to claim 12, characterized in that the sodium secondary battery is a sodium metal battery without a negative electrode.

20. A power consumption device characterized by including the sodium secondary battery described in claim 12.

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