Electrolyte for sodium secondary battery, sodium secondary battery and power consumption device

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] The present application relates to the technical field of sodium secondary batteries, and in particular to an electrolyte for sodium secondary batteries, a sodium secondary battery, and a power consuming device.

[0002] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application incorporates by reference Chinese patent application No. 202310075482.6, entitled "Electrolyte for Sodium Secondary Battery, Sodium Secondary Battery and Power Consumption Device," filed on January 16, 2023, which is incorporated herein by reference in its entirety. [Background technology]

[0003] With the development of battery technology, lithium secondary batteries have dominated the portable electronics market and are gradually expanding into large-scale electrical energy storage applications. However, traditional lithium resources are no longer able to meet the urgent demand for large-scale, high-energy density energy storage systems. Therefore, sodium secondary batteries, which have abundant sodium reserves, low cost, and similar electrochemical properties to lithium secondary batteries, have emerged due to the situation. However, the sodium secondary batteries currently being widely studied have relatively poor high-temperature cycle performance and suffer from serious high-temperature gas generation, which severely limits the further application of sodium secondary batteries. Summary of the Invention

[0004] In view of the problems existing in the background art, the present application provides an electrolyte for a sodium secondary battery, which aims to improve the high-temperature cycle performance of a sodium secondary battery, reduce the high-temperature gas generation phenomenon of a sodium secondary battery, and improve the electrochemical performance and safety performance of a sodium secondary battery at high temperatures.

[0005] A first aspect of the present application provides an electrolyte for a sodium secondary battery, the electrolyte including an additive, the additive including a fluoroether-based compound.

[0006] Fluoroether compounds have a relatively low lowest unoccupied molecular orbital (LUMO) and can be reduced on the surface of the negative electrode to form an SEI mainly composed of organic fluorides, which greatly enhances the structural stability and uniformity of the SEI on the negative electrode surface, reduces direct contact between the negative electrode and the solvent, reduces side reactions between the negative electrode and the solvent, improves the high-temperature cycle performance of sodium secondary batteries, reduces the high-temperature gas generation phenomenon of sodium secondary batteries, and improves the electrochemical performance and safety performance of sodium secondary batteries at high temperatures.

[0007] In any embodiment, the fluoroether-based compound comprises one or more compounds according to Formula I: TIFF2025532250000002.tif20150 wherein 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 any embodiment, the fluoroether compound may be 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 , 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, 2,2,2-trifluoroethyl ether, and optionally 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, ethyl nonafluorobutyl ether.

[0009] In any embodiment, the mass content of the additive is 0.2% to 10%, and optionally 0.5% to 6.5%, based on the total mass of the electrolyte.

[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 amount of high temperature gas generation, and extends the operating temperature of the battery.

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

[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 amount of high temperature gas generation, and extends the operating temperature of the battery.

[0013] The electrolyte contains an ether-based solvent, which can 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.

[0014] In any embodiment, the sodium salts include one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate.

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

[0016] In either embodiment, the electrolyte further comprises a lithium salt.

[0017] The electrolyte contains a lithium salt, which can 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.

[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] A second aspect of the present application provides a sodium secondary battery, the sodium secondary battery comprising the electrolyte of the first aspect.

[0020] In any embodiment, the sodium secondary battery includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector; Sodium secondary batteries satisfy the relationship 0.3≦Z-0.01X≦6, Here, based on the total mass of the electrolyte, X g / m 2 is the areal density of the undercoating and Z% is the mass content of the additive.

[0021] The areal density of the undercoating on at least one side of the negative electrode current collector is X g / m 2 By controlling the mass content Z% of the additive based on the total mass of the electrolyte 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 of the battery can be expanded.

[0022] In any embodiment, the sodium secondary battery includes a negative electrode plate, the negative electrode plate including 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; Sodium secondary batteries satisfy the relationship 0.84≦Y-0.01X≦5.84, Here, based on the total mass of the electrolyte, X g / m 2 is the areal density of the undercoating and Y% is the mass content of the lithium salt.

[0023] The areal density of the undercoating on at least one side of the negative electrode current collector is X g / m 2 and the mass content Y% of the lithium salt based on the total mass of the electrolyte is controlled to satisfy the relational expression 0.84≦Y-0.01X≦5.84, thereby improving the room 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.

[0024] In any embodiment, the areal density of the undercoating is between 5 and 50 g / m 2 is.

[0025] When the areal density of the undercoating is within an appropriate range, it is 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.

[0026] In either embodiment, the undercoating comprises one or more of a carbon coating, an alloy coating, and a metal oxide coating, and optionally is a carbon coating.

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

[0028] In either embodiment, the sodium secondary battery is a non-anode sodium metal battery.

[0029] A sodium secondary battery is a negative electrode-free sodium metal battery that can 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.

[0030] A third aspect of the present application provides a battery module, which includes the sodium secondary battery of the second aspect.

[0031] A fourth aspect of the present application provides a battery pack, which includes the sodium secondary battery of the second aspect or the battery module of the third aspect.

[0032] A fifth aspect of the present application provides a power consumption device, which includes at least one of the sodium secondary battery of the second aspect, the battery module of the third aspect, or the battery pack of the fourth aspect. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a schematic diagram of a sodium secondary battery according to an embodiment of the present application. [Figure 2] FIG. 2 is an exploded view of the sodium secondary battery according to the embodiment of the present application shown in FIG. 1. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. 4. [Figure 6] 1 is a schematic diagram of a power consumption device that uses a sodium secondary battery according to an embodiment of the present application as a power source. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the secondary battery, battery module, battery pack, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of actually identical structures may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0035] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and any combination is possible; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also possible. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all possible. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents that the present specification has already listed all real numbers between "0-5," and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, the terms "comprise" and "include" used in this application may be open-ended or closed-ended. For example, the terms "comprise" and "include" may further include or include other components not listed, or may include or include only the listed components.

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

[0040] At high temperatures, inorganic components at the solid electrolyte interface (SEI) of a sodium rechargeable battery dissolve, creating a porous structure. This causes the electrolyte to continuously decompose on the negative electrode surface, resulting in the SEI constantly decomposing and regenerating, consuming the limited sodium resources within the battery. This increases the battery's self-discharge and reduces its cycle performance. At the same time, at high temperatures, the positive and negative electrodes of a sodium rechargeable battery undergo chemical reactions with the electrolyte, releasing heat and generating gas, causing the battery's volume to expand. In severe cases, this can lead to a short circuit within the battery, reducing the safety performance of the battery and severely limiting its applications.

[0041] [Electrolyte for sodium secondary batteries] The present application provides an electrolyte for a sodium secondary battery, the electrolyte including an additive, and the additive including a fluoroether-based compound.

[0042] In this specification, the term "sodium secondary battery" refers to a secondary battery that uses sodium ions as a charge carrier, and the negative electrode active material of the 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, and a sodium secondary battery that uses metallic sodium as the negative electrode active material is referred to as a sodium metal battery.

[0043] In some embodiments, the negative electrode active material of the sodium secondary battery comprises one or more of a graphitic carbon material, an amorphous carbon material, and a nanocarbon material.

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

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

[0046] As used herein, the term "anodeless sodium metal battery" refers to a sodium metal battery in which the assembly process uses a current collector as the anode, and during charging, sodium ions deposit on the current collector to form a sodium metal anode.

[0047] As used herein, the term "electrolyte" refers to a carrier that transports ions in a sodium secondary battery, and includes a liquid electrolyte, a solid electrolyte, or a quasi-solid electrolyte.

[0048] As used herein, the term "additive" refers to a component present in a relatively small amount in the electrolyte, and may be a gas, liquid, or solid. Conceptually, the only difference between an additive, a solvent, and a sodium salt is their presence in the electrolyte.

[0049] As used herein, the term "fluoroether compounds" refers to compounds obtained after direct fluorine substitution modification of ether compounds.

[0050] Fluoroether compounds have a relatively low lowest unoccupied molecular orbital (LUMO) and preferentially undergo reduction reactions with sodium salts over solvents to produce thermally stable organic fluorides, forming a structurally stable and uniformly distributed SEI on the surface of the negative electrode. The SEI containing a large amount of fluoride is less susceptible to secondary decomposition and regeneration, reducing sodium consumption within the sodium secondary battery and improving the high-temperature cycle performance of the sodium secondary battery. Meanwhile, the structurally stable and uniformly distributed SEI reduces direct contact between the electrolyte and the negative electrode, reducing side reactions between the electrolyte and the negative electrode, suppressing hydrogen gas generation during high-temperature cycles of the sodium secondary battery and improving the high-temperature gas generation phenomenon of the sodium secondary battery.

[0051] In some embodiments, the fluoroether-based compound comprises one or more compounds according to Formula I: TIFF2025532250000003.tif20150 wherein 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] As used herein, the term "C1-C6 alkyl group" refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, the radical being free of unsaturation, having from 1 to 6 carbon atoms and attached to the remainder of the molecule via a single bond.

[0053] As used herein, the term "fluoro-substituted" means that at least one hydrogen atom of the compound or chemical moiety is replaced with a fluorine atom or a fluoroalkyl group.

[0054] As used herein, the term "fluoroalkyl group" refers to an alkyl group that contains at least one fluorine atom.

[0055] In some embodiments, 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, 1,1,2,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ether, 1,1,2,3,3-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-based 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 additive content by weight is 0.2% to 10% based on the total weight of the electrolyte. In some embodiments, the additive content by weight is optionally 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%, 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% , 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%, 9.5%~10%.

[0058] When the mass content of the additive is within an appropriate range, a uniformly structured and uniformly distributed SEI is formed on the surface of the negative electrode, which further ensures that the battery has low interfacial impedance and provides the SEI with excellent sodium ion transport performance. The battery has excellent room temperature cycle performance and high temperature cycle performance, low high-temperature gas generation, and extends the operating temperature range of the battery.

[0059] In some embodiments, the additive content by weight is 0.5% to 6.5% based on the total weight of the electrolyte. In some embodiments, the additive content by weight is optionally 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%, or 1% to 2.5% based on the total weight 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%, 6%~6.5%.

[0060] When the mass content of the additive is within an appropriate range, a uniformly structured and uniformly distributed SEI is formed on the surface of the negative electrode, which further ensures that the battery has low interfacial impedance, allows the SEI to have excellent sodium ion transport performance, 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.

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

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

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

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

[0065] The molecules of ether solvents can establish a stable electrode / electrolyte interface on the surface of the negative electrode, form a stable SEI, reduce electrochemical polarization, 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 of the battery. At the same time, both ether solvents and fluoroether compounds contain ether bonds, which can improve the stability of the system.

[0066] In some embodiments, the mass content of the sodium salt is 3% to 40%, based on the total mass of the electrolyte. In some embodiments, the mass content of the sodium salt is optionally 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%, or 10% to 20%, based on the total mass of the electrolyte. , 10% to 25%, 10% to 30%, 10% to 35%, 10% to 40%, 15% to 20%, 15% to 25%, 15% to 30%, 15% to 35%, 15% to 40%, 20% to 25%, 20% to 30%, 20% to 35%, 20% to 40%, 25% to 30%, 25% to 35%, 25% to 40%, 30% to 35%, 30% to 40%, 35% to 40%.

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

[0068] In some embodiments, the mass content of the sodium salt is 5% to 30% based on the total mass of the electrolyte, optionally any one of 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% based on the total mass of the electrolyte.

[0069] When the mass content of the sodium salt is within an appropriate range, the electrolyte has appropriate viscosity and excellent ionic conductivity, which can 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.

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

[0071] In some embodiments, the lithium salt comprises 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.

[0072] Taking sodium metal batteries as an example, the introduction of lithium ions can also effectively inhibit 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 to sodium metal. At the initial stage of the reaction, sodium metal deposits unevenly on the current collector surface, forming dendrites, the tips of which have a relatively high negative charge density due to the tip effect. Meanwhile, both lithium ions and sodium ions are positive monovalent cations with a single positive charge. However, due to their smaller ion radius, lithium ions have a higher positive charge density and are distributed to the dendrite tips before sodium ions. This effectively reduces the continued deposition of sodium ions at the sodium dendrite tips, inhibits the growth of sodium dendrites, and significantly improves the battery's cycle performance.

[0073] The electrolyte contains a lithium salt, which can 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.

[0074] [Sodium secondary battery] The present application provides a sodium secondary battery, which includes the electrolyte in any of the embodiments.

[0075] In some embodiments, a sodium secondary battery includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector; Sodium secondary batteries satisfy the relationship 0.3≦Z-0.01X≦6, Here, based on the total mass of the electrolyte, X g / m 2 is the areal density of the undercoating and Z% is the mass content of the additive.

[0076] As used herein, the term "undercoating on at least one side of a negative electrode current collector" refers to an undercoating on one or both sides of the current collector, and the undercoating may be in direct contact with the current collector, i.e., no other structure is included between the current collector and the undercoating, or the undercoating may not be in direct contact with the current collector, i.e., another structure is included between the current collector and the undercoating.

[0077] The undercoating has the characteristic of low metal nucleation potential, which can effectively improve metal deposition / dissolution performance, and can also reduce the large volume changes that the metal deposition / dissolution process brings to the battery core, stabilize the battery core structure, improve the battery's room temperature cycle performance and high temperature cycle performance, reduce the high-temperature gas generation phenomenon in the battery, and improve the battery's electrochemical performance and safety performance.

[0078] Taking anode-less metal batteries as an example, during the initial charging process, the additive first undergoes reduction decomposition on the undercoating on the current collector surface, and some of the decomposition products accumulate on the undercoating to form SEI. During the discharging process, metallic sodium transforms into sodium ions and returns to the positive electrode, enabling cyclic charging and discharging.

[0079] The applicant has determined that the undercoating surface density of a sodium secondary battery is X g / m 2By controlling the mass content Z% of the additive based on the total mass of the electrolyte within the range of 0.3≦Z-0.01X≦6, it was unexpectedly discovered that the synergistic effect of the undercoating and the additive can improve the stability and uniformity of the SEI, further improving the high-temperature cycle performance of the battery, reducing the high-temperature gas generation phenomenon of the battery, and expanding the operating temperature range of the battery.

[0080] In some embodiments, a sodium secondary battery includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector; For sodium secondary batteries, the following limits 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 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.Satisfies one of the following relational expressions: 0.01X≦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. Here, based on the total mass of the electrolyte, X g / m 2 is the areal 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 including a negative electrode current collector and an undercoating formed on at least one side of the negative electrode current collector, the electrolyte including a lithium salt, and the 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 is the areal density of the undercoating and Y% is the mass content of the lithium salt.

[0082] In some embodiments, a sodium secondary battery includes a negative electrode plate, the electrolyte including a lithium salt, the negative electrode plate including 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.Satisfy one of the following relations: 0.01X≦5.5, 4.5≦Y-0.01X≦5, 4.5≦Y-0.01X≦5.5, 5≦Y-0.01X≦5.5. Here, based on the total mass of the electrolyte, X g / m 2 is the areal density of the undercoating and Y% is the mass content of the lithium salt.

[0083] The undercoating containing free electrons electrostatically adsorbs lithium ions, which have a relatively high positive charge density. The lithium ions then deposit on the undercoating via the SEI layer, effectively reducing the overpotential of sodium metal deposition and suppressing the formation of sodium dendrites, which is beneficial for improving the cycle performance of the battery.

[0084] The applicant has determined that the undercoating surface density of the secondary battery is X g / m 2 It was unexpectedly discovered that by controlling the mass content Y% of the undercoating and lithium salt based on the total mass of the electrolyte within the range of 0.84≦Y-0.01X≦5.84, a synergistic effect between the undercoating and the lithium salt can be achieved, improving the stability and uniformity of the SEI, further improving the room 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.

[0085] In some embodiments, the areal density of the undercoating is between 5 and 50 g / m 2 is.

[0086] In some embodiments, the areal density of the undercoating is preferably between 5 and 10 g / m 2 , 5~20g / m 2 , 5 to 30 g / 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 range of undercoating area density can improve the normal temperature cycle performance and high temperature cycle performance of the battery, reduce the high temperature gas generation phenomenon of the battery, and at the same time, increase the energy density of the battery to meet the usage demands of the battery.

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

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

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

[0091] In some embodiments, the undercoating comprises an adhesive, the adhesive comprising any one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene butadiene rubber, sodium alginate, lithium / sodium polyacrylate, polytetrafluoroethylene, polyimide, and polyurethane.

[0092] In some embodiments, the undercoating is a metal coating, the metal has a body-centered cubic structure, and the metal comprises any one of α-Fe, V, Nb, Cr, Mo, Ta, and W.

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

[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, and the conductive polymer comprises any one of polyaniline, polythiophene, polypyrrole, and polyphenylene vinylene.

[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 comprises at least one of conductive carbon black, graphite, carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and fullerenes.

[0098] In some embodiments, the sodium secondary battery is a non-anode sodium metal battery.

[0099] In some embodiments, the secondary battery is a non-anode sodium metal battery. Non-anode sodium metal batteries do not use anode active materials, but instead use only anode current collectors as anodes. During the initial charging process, sodium plating is completed on the anode, which is then returned to the cathode during discharge, achieving charge-discharge cycling. Because they do not use anode materials and only use anode current collectors, non-anode sodium metal batteries effectively overcome the shortcomings of sodium metal batteries and can achieve higher energy densities than metallic sodium anodes.

[0100] The anode-free sodium metal battery can 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.

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

[0102] The CB value is calculated by dividing the capacity per unit area of ​​the negative electrode plate in a sodium secondary battery by the capacity per unit area of ​​the positive electrode plate. Because no-anode sodium metal batteries contain any negative active material, the capacity per unit area of ​​the negative electrode plate is relatively small, and the CB value of the secondary battery is less than 0.1.

[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. Because sodium ions do not form an alloy with aluminum, and considering cost and weight reduction, sodium secondary batteries preferentially employ aluminum-based current collectors, which are either aluminum foil, aluminum alloy foil, or aluminum-based composite current collectors. 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 a polymer base film located in the center and aluminum foils on both sides, or aluminum foils on both sides. Alternatively, an aluminum alloy foil may be provided on one side of a polymer base film and an aluminum alloy foil on the other side, and the polymer base film may be made of any one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polychloroethylene, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, polyparaphenylene terephthalamide, polypropylethylene, polyformaldehyde, epoxy resin, phenol resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and 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 including a positive electrode active material, which may include at least one of a layered transition metal oxide, a polyanion-type compound, and a Prussian blue-based 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. Optionally, the layered transition metal oxide may be, 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) n- The compound may have an anionic unit, wherein the metal ion is optionally one of sodium ion, lithium ion, potassium ion, and zinc ion, the transition metal is optionally at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y is optionally at least one of P, S, and Si, and n is (YO4) n- represents the valence state of

[0107] The Prussian blue compound may be a compound 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. 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; <a≦2、0<b<1、0<c<1である。

[0108] The positive electrode active material layer may further include a conductive agent to improve the conductive performance of the positive electrode, which may be one or more of 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 include an adhesive to firmly adhere the positive electrode active material and optional conductive agent to the positive electrode current collector, and the adhesive may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0110] The positive electrode current collector may 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 may be one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal materials of the metal foil, the carbon-coated metal foil, and the porous metal plate may each independently be 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 with a polymer base film.

[0111] In some embodiments, a positive electrode plate can be manufactured as follows: Components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, which is then coated onto a positive electrode current collector, and the positive electrode plate is obtained after processes such as drying and cold pressing.

[0112] [Separator] In some embodiments, the sodium secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any known porous separator with good chemical stability and mechanical stability may be selected.

[0113] In some embodiments, the separator may be made of 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 multi-layer composite film, without any particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitation.

[0114] In some embodiments, the positive and negative electrodes and the separator can be fabricated into an electrode assembly by a winding or lamination process.

[0115] In some embodiments, the sodium secondary battery may include an outer casing, which may be used to package the electrode assembly and the electrolyte.

[0116] In some embodiments, the exterior of the sodium secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the sodium secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0117] The present application does not particularly limit the shape of the sodium secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Fig. 1 shows an example of a sodium secondary battery 5 having a rectangular structure.

[0118] In some embodiments, referring to FIG. 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged within the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The sodium secondary battery 5 may include one or more electrode assemblies 52, and those skilled in the art can select the number of electrode assemblies 52 according to specific 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] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, a plurality of sodium secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of sodium secondary batteries 5 may be fixed by fasteners.

[0121] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of sodium secondary batteries 5 are accommodated in this accommodating space.

[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, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0123] 4 and 5 show an example of a battery pack 1. Referring to FIGS. 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, and the upper housing 2 covers the lower housing 3 and may form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0124] The present application also provides a power consuming device, the power consuming device including at least one of a sodium secondary battery, a battery module, or a battery pack according to the present application. The sodium secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming 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, satellites, energy storage systems, etc.

[0125] The power consumption device can be selected as a sodium secondary battery, a battery module, or a battery pack depending on its usage needs.

[0126] 6 shows an example of a power consumption device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density needs of sodium secondary batteries, a battery pack or battery module can be employed.

[0127] Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. These devices are generally required to be thin, and can employ a sodium secondary battery as a power source.

[0128] Example Examples of the present application are described below. The examples described below are illustrative and are intended only to interpret the present application and should not be understood as limitations on the present application. While specific techniques or conditions are not specified in the examples, they are carried out according to techniques or conditions described in literature in the art or according to product specifications. Manufacturers of the reagents and instruments used are not indicated, and all are commercially available ordinary products. While the following examples only describe the case where the secondary battery is a sodium-ion battery, the present application is not limited thereto.

[0129] 1. Manufacturing method Example 1 1) Electrolyte production In an argon gas atmosphere glove box with a moisture content of <10 ppm, sodium hexafluorophosphate (sodium salt), lithium hexafluorophosphate (lithium salt), and methyl nonafluorobutyl ether (additive) were added to an ethylene glycol dimethyl ether solvent, where, 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 The positive electrode active material Na3V2(PO4)3, the adhesive polyvinylidene fluoride (PVDF), and the conductive carbon black (Super-P) were uniformly mixed in a mass ratio of 96%:2%:2% in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. This was then applied to the surface of an aluminum foil using a squeeze coater according to the mass requirement per unit area of ​​the positive electrode active material, dried, and then pressed into a cold press to form a coated electrode plate at a density of 2.5 g / cm. 3 The final positive electrode plate was obtained by cold pressing at the design pressure density.

[0131] 3) Manufacturing of negative electrode plates The carbon nanotubes and sodium alginate were added to deionized water and stirred into a uniform slurry. The slurry was coated onto an aluminum foil negative electrode current collector, dried, and cut into a negative electrode plate with a no-anode structure, where the areal density of the undercoating was 20 g / m. 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 this order, and a separator was placed between the positive and negative electrodes to provide isolation. The electrolyte was added to the positive and negative electrodes to form a button battery.

[0134] Examples 2 to 29 Except for the different electrolyte formulations and / or manufacturing parameters of the negative electrode plates, the other steps of Examples 2 to 29 are the same as those of Example 1, where the manufacturing methods of the negative electrode plates of Examples 24 and 25 are as follows, and the specific parameters are as shown in Table 1.

[0135] Example 24: Carbon nanotubes and sodium alginate were added to deionized water and stirred into a uniform slurry, which was then coated onto an aluminum foil negative electrode current collector, dried, and cut to obtain a negative electrode current collector with an undercoating, where the areal density of the undercoating was 20 g / m 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 mixed in a weight ratio of 90:5:4:1 in an appropriate amount of deionized water and thoroughly stirred to form a uniform negative electrode slurry. The negative electrode slurry was then coated onto a negative electrode current collector having an undercoat, dried at 100°C, and pressed to obtain a negative electrode plate.

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

[0137] Comparative Examples 1 to 5 Except for the different electrolyte formulations and / or manufacturing parameters of the negative electrode plate, the other steps of Comparative Examples 1 to 3 are the same as those of Example 1, where Comparative Example 4 is the same as the manufacturing method of the negative electrode plate of Example 24, and Comparative Example 5 is the same as the manufacturing method of the negative electrode plate of Example 25, and the specific parameters are as shown in Table 1.

[0138] 2. Battery performance test 1) Room temperature cycle performance At 25°C and atmospheric pressure (0.1 MPa), the battery was charged at a constant current of 0.5 C to a voltage of 3.5 V, and then discharged at a constant current of 1 C to a voltage of 3.2 V, which constituted one charge-discharge cycle. The initial discharge capacity was taken as 100%, and the charge-discharge cycle was repeated 500 times. After the test was stopped, the cycle capacity retention rate was recorded, and the room temperature capacity retention rate was used as an index to evaluate the room temperature cycle performance of the battery.

[0139] 2) High-temperature cycle performance At 60°C and atmospheric pressure (0.1 MPa), the battery was charged at a constant current of 0.5 C to a voltage of 3.5 V, and then discharged at a constant current of 1 C to a voltage of 3.2 V, which constituted one charge-discharge cycle. The initial discharge capacity was taken as 100%, and the charge-discharge cycle was repeated 500 times. After the test was stopped, the cycle capacity retention rate was recorded, and the high-temperature capacity retention rate was used as an index for evaluating the high-temperature cycle performance of the battery.

[0140] 3) High-temperature gas generation performance At room temperature (25°C), the battery was charged to 3.5V at a constant current of 0.5C. After the battery was fully charged, the initial volume of the battery was measured using the drainage method. The battery was stored in an oven at 60°C for 24 days, then removed and left at room temperature for 60 minutes. After cooling to room temperature, the battery volume was measured using the drainage method within 60 minutes. The volume expansion rate of the battery was calculated based on the volume of the battery before storage. The volume expansion rate (%) after storing the battery at 60°C for 24 days = (volume of battery measured after storage / volume of battery measured before storage) - 1.

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

[0142] 3. 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 sodium secondary battery electrolytes in Examples 1 to 29 all contain additives, and the additives include one or more of 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 of Examples 1 to 8, 11 to 23, 26 to 29 with Comparative Example 1, Example 10 with Comparative Example 2, Example 9 with Comparative Example 3, and Examples 24 to 25 with Comparative Examples 4 to 5, the additives were 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 is 0.2% to 10% based on the total mass of the electrolyte, and the battery has excellent room temperature cycle performance and high temperature cycle performance, has low high temperature gas generation, and extends the operating temperature 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%-6.5% based on the total mass of the electrolyte, which could 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.

[0148] The electrolytes in Examples 1 to 29 further contain a sodium salt, which includes sodium hexafluorophosphate (NaPF6) or sodium tetrafluoroborate (NaBF4), and the mass content of the sodium salt is 3% to 40% based on the total mass of the electrolyte. The batteries have excellent room temperature cycle performance and high temperature cycle performance, low high-temperature gas generation, and a wide range of battery operating temperatures.

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

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

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

[0152] As can be seen from a comparison between Examples 1 and 24 and Example 25, by providing an undercoating on at least one side of the negative electrode current collector, the undercoating including a carbon coating, the room temperature cycle performance and high temperature cycle performance of the battery were improved, the high temperature gas generation phenomenon of the battery was reduced, and the electrochemical performance and safety performance of the battery were improved.

[0153] As can be seen from the comparison between Examples 1, 26 and 27 and Examples 28 and 29, the areal density of the undercoating on at least one side of the negative electrode current collector is X g / m 2 By controlling the mass content Z% of the additive based on the total mass of the electrolyte to satisfy 0.3≦Z-0.01X≦6, it was possible to improve the high-temperature cycle performance of the battery, reduce the high-temperature gas generation phenomenon of the battery, and expand the operating temperature range of the battery.

[0154] As can be seen from a comparison between Examples 1, 16 and 17 and Examples 18 and 19, the areal density of the undercoating on at least one side of the negative electrode current collector is X g / m 2 By controlling the mass content Y% of the lithium salt based on the total mass of the electrolyte to satisfy the relational expression 0.84≦Y-0.01X≦5.84, 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.

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

[0156] As can be seen from the comparison between Example 1 and Example 24, the sodium secondary battery is a negative electrode-less sodium metal battery, and can 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 the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments without departing from the spirit of the present application, and other methods configured by combining some of the components of the embodiments, are also included within the scope of the present application. [Explanation of symbols]

[0158] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 sodium secondary battery, 51 case, 52 electrode assembly, 53 cover plate.

Claims

1. 1. An electrolyte for a sodium secondary battery, comprising an additive, the additive comprising a fluoroether-based compound.

2. The fluoroether-based compound comprises one or more compounds of formula I: Here, R 1 and R 2 each independently represents a fluorine-substituted or unsubstituted C 1 -C 6 alkyl groups, and R 1 , R 2 2. The electrolyte according to claim 1, wherein at least one of the groups contains a fluorine atom.

3. The fluoroether compounds include 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, 1,1,2,3,3,3-pentafluoropropyl 3. The electrolyte of claim 1 or 2, comprising one or more of heptafluoropropyl ether, 1,1,2,2-tetrafluoroethyl 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, 2,2,2-trifluoroethyl ether, and optionally 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, ethyl nonafluorobutyl ether.

4. 4. The electrolyte according to claim 1, wherein the mass content of the additive is between 0.2% and 10%, and optionally between 0.5% and 6.5%, based on the total mass of the electrolyte.

5. 5. The electrolyte according to claim 1, further comprising a sodium salt and an ether-based solvent, wherein the mass content of the sodium salt is 3% to 40%, and optionally 5% to 30%, based on the total mass of the electrolyte.

6. 6. The electrolyte of claim 5, wherein the sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate.

7. 7. The electrolyte according to claim 5, wherein the ether-based 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, 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.

8. 8. The electrolyte of claim 1, further comprising a lithium salt.

9. 9. The electrolyte of claim 8, wherein the lithium salt comprises 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.

10. A sodium secondary battery, comprising the electrolyte according to any one of claims 1 to 9.

11. The sodium secondary battery includes a negative electrode plate, the negative electrode plate including 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 0.3≦Z−0.01X≦6, Here, based on the total mass of the electrolyte, X g / m 2 11. The sodium secondary battery according to claim 10, wherein Z% is the areal density of the undercoating and Z% is the mass content of the additive.

12. The sodium secondary battery includes a negative electrode plate, the negative electrode plate including 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 sodium secondary battery satisfies the relational expression 0.84≦Y−0.01X≦5.84, Here, based on the total mass of the electrolyte, X g / m 2 12. The sodium secondary battery according to claim 10, wherein Y% is the areal density of the undercoating and Y% is the mass content of the lithium salt.

13. The surface density of the undercoating is 5 to 50 g / m 2 13. The sodium secondary battery according to claim 11, wherein

14. 14. The sodium secondary battery according to claim 11, wherein the undercoating is one or more of a carbon coating, an alloy coating, and a metal oxide coating, and is selectively a carbon coating.

15. 15. The sodium secondary battery according to claim 11, wherein the undercoating contains one or more of superconducting carbon black, ketjen black, acetylene black, carbon nanotubes, and graphene.

16. 16. The sodium secondary battery according to claim 10, wherein the sodium secondary battery is a non-negative electrode sodium metal battery.

17. A power consuming device comprising the sodium secondary battery according to any one of claims 10 to 16.

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