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 electrolyte for a sodium secondary battery includes a diluent, and the diluent includes an alkylalkoxysilane compound. The present application provides an electrolyte for a sodium secondary battery, the electrolyte including a diluent including an alkylalkoxysilane compound, which can reduce high-temperature gas generation in the battery and improve battery safety.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application incorporates by reference Chinese patent application No. 202310075590.3, 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.

[0002] 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. [Background technology]

[0003] With the development of society, various problems, including energy shortages and environmental pollution, are becoming increasingly prominent. To achieve the social goal of sustainable development, researchers are increasingly turning to secondary batteries. Although secondary batteries are the energy storage system of choice for portable electronic products and electric vehicles, they suffer from significant performance degradation and serious safety risks in high-temperature environments.

[0004] Electrolytes serve as a medium for transport between the positive and negative electrodes of secondary batteries, and their performance directly affects the high-temperature performance of secondary batteries. Conventional electrolytes are prone to decomposition under high-temperature conditions and are prone to react with the negative electrode, resulting in serious gas generation. Therefore, developing an electrolyte with high stability at high temperatures to improve the high-temperature performance of batteries has become a pressing issue for those skilled in the art. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide an electrolyte for a sodium secondary battery that reduces the high-temperature gas generation phenomenon in the battery and expands the application environment of the battery.

[0006] A first aspect of the present application provides an electrolyte for a sodium secondary battery, the electrolyte including a diluent, and the diluent including an alkylalkoxysilane compound.

[0007] The carbon-oxygen bond in the alkylalkoxysilane compound has strong bond energy, which endows the alkylalkoxysilane compound with excellent chemical stability, improves the electrochemical window of the electrolyte, and provides the electrolyte with excellent electrochemical stability. In addition, the alkylalkoxysilane compound acts as a diluent, forming a protective layer around the solvated structure, reducing direct contact between the solvent and the positive and negative electrodes, suppressing gas generation during high-temperature cycling of sodium secondary batteries, and improving the safety performance of the battery at high temperatures.

[0008] In any embodiment, the diluent comprises one or more compounds of Formula I, Formula II, Formula III, or Formula IV; JPEG2025532309000002.jpg55165Here, R1 is C1-C 10 R2 is selected from C1-C6 alkyl groups.

[0009] In any embodiment, the diluent comprises one or more selected from methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, and optionally one or more of methyltrimethoxysilane, methyltriethoxysilane, and tetraethoxysilane.

[0010] In any embodiment, the electrolyte further comprises a solvent, and the volume ratio Y of the diluent to the solvent is 0.5-7, and optionally 1-5.

[0011] When the volume ratio of the diluent to the solvent is within an appropriate range, 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 high-temperature cycle performance and safety performance of the battery can be improved.

[0012] In either embodiment, the solvent comprises an ethereal solvent.

[0013] The ether-based solvent allows the battery to have excellent normal temperature cycle performance and high temperature cycle performance, and a low amount of high temperature gas generation.

[0014] In any embodiment, the solvent comprises one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, and optionally one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, and tetraethylene glycol dimethyl ether.

[0015] In any embodiment, the electrolyte comprises a sodium salt; The electrolyte satisfies the relationship 5 / (1+Y)≦X≦50 / (1+Y), where X% is the mass content of the sodium salt, based on the total mass of the electrolyte, and Y is the volume ratio of the diluent to the solvent.

[0016] By controlling the mass content of the sodium salt (X%) based on the total mass of the electrolyte and the volume ratio Y of the diluent to the solvent so that 5 / (1+Y)≦X≦50 / (1+Y) is satisfied, the room temperature cycle performance of the battery can be improved, and the electrochemical performance of the battery can be improved.

[0017] In any embodiment, the sodium salts include one or more of sodium perchlorate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium trifluoroacetate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[0018] A second aspect of the present application provides a sodium secondary battery, the sodium secondary battery comprising the electrolyte of the first aspect.

[0019] 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.

[0020] The conductive undercoating has the characteristic of low metal nucleation potential, which can effectively improve the 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.

[0021] In any embodiment, the areal density of the undercoating is between 5 and 50 g / m 2 is.

[0022] An appropriate range of undercoating area density can optimize the metal deposition effect, improve the high-temperature cycle performance and room-temperature cycle performance of the battery, and reduce the high-temperature gas generation phenomenon of the battery. At the same time, an appropriate range of undercoating area density can increase the energy density of the battery and meet the usage demands of the battery.

[0023] 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.

[0024] In either embodiment, the undercoating comprises one or more of superconducting carbon black, ketjen black, acetylene black, carbon nanotubes, and graphene.

[0025] In either embodiment, the sodium secondary battery is a non-anode sodium metal battery.

[0026] 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.

[0027] A third aspect of the present application provides a battery module, which includes the sodium secondary battery of the second aspect.

[0028] 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.

[0029] 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]

[0030] [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

[0031] 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.

[0032] 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.

[0033] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0034] 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.

[0035] 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.

[0036] 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).

[0037] When a secondary battery is used or stored at high temperatures, the reaction between the positive and negative electrodes and the electrolyte becomes more active, the amount of heat released from the reaction increases significantly, a large amount of gas is generated, and the volume of the battery is likely to expand. In serious cases, this may cause a short circuit inside the battery, which may seriously affect the safety performance of the battery.

[0038] [Electrolyte for sodium secondary batteries] The present application provides an electrolyte for a sodium secondary battery, the electrolyte including a diluent, and the diluent including an alkylalkoxysilane compound.

[0039] 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.

[0040] 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.

[0041] In some embodiments, the negative electrode active material of the sodium secondary battery is hard carbon.

[0042] In some embodiments, the negative electrode active material of the sodium secondary battery is metallic sodium.

[0043] 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.

[0044] 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.

[0045] As used herein, the term "diluent" refers to an insoluble or sparingly soluble component of an electrolyte salt in which there is no significant coordination or association between the diluent molecules and the cations of the electrolyte salt, and the diluent does not disrupt the solvation structure.

[0046] A solvated structure occurs when the solvent molecules in an electrolyte have a much stronger binding force to cations than to anions, and after a sodium salt dissolves in the solvent, the solvent aggregates around the sodium ions. The aggregates formed by the sodium ions and the solvent are called solvated structures.

[0047] As used herein, the term "alkylalkoxysilane compound" refers to a compound in which, of the four bonds bonded to the silicon atom, at least one bond is bonded to an alkoxy group and the remaining bonds are bonded to alkyl groups, where the alkoxy group is composed of one alkyl group and one oxygen atom.

[0048] As used herein, the term "electrochemical window" refers to the difference between the oxidation potential and the reduction potential of an electrolyte; the wider the electrochemical window, the greater the electrochemical stability of the electrolyte.

[0049] The use of alkylalkoxysilane compounds as diluents not only contributes to the strong bond energy of the carbon-oxygen bond in alkylalkoxysilane compounds, but also provides the alkylalkoxysilane compounds with excellent chemical stability and an improved electrochemical window for the electrolyte. Furthermore, due to the relatively low solubility of alkylalkoxysilane compounds in sodium salts, the alkylalkoxysilane compounds do not directly contribute to the solvation structure of sodium ions and do not affect the film formation performance on the surfaces of the positive and negative electrodes of sodium secondary batteries. Furthermore, the alkylalkoxysilane compounds form a protective layer around the solvation structure, reducing direct contact between the solvent and the positive and negative electrodes. This suppresses gas generation during high-temperature cycling of sodium secondary batteries and improves the safety performance of the battery at high temperatures. Furthermore, the addition of alkylalkoxysilane compounds as diluents reduces the viscosity of the electrolyte and increases its ionic conductivity without destroying the solvation structure, thereby benefiting the electrochemical performance of the battery.

[0050] In some embodiments, the diluent comprises one or more compounds of Formula I, Formula II, Formula III, or Formula IV, JPEG2025532309000003.jpg55165Here, R1 is C1-C 10 R2 is selected from C1-C6 alkyl groups.

[0051] As used herein, the term "C1-C 10 An "alkyl group" is a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, the radical being free of unsaturation, having from 1 to 10 carbon atoms, and attached to the remainder of the molecule through a single bond.

[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] In some embodiments, the diluent comprises one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, and n-decyltrimethoxysilane.

[0054] In some embodiments, the diluent comprises one or more of methyltrimethoxysilane, methyltriethoxysilane, and tetraethoxysilane.

[0055] In some embodiments, the electrolyte further comprises a solvent.

[0056] In some embodiments, the solvent comprises an ethereal solvent.

[0057] In some embodiments, the solvent comprises one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane.

[0058] In some embodiments, the solvent comprises one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetraethylene glycol dimethyl ether.

[0059] The molecules of the ether solvents establish a stable electrode / electrolyte interface on the surface of the negative electrode, forming a stable SEI, reducing electrochemical polarization and improving the cycle performance of the battery. At the same time, the ether solvents and alkylalkoxysilane compounds share the same carbon-oxygen bond, ensuring their mutual solubility. This helps the alkylalkoxysilane compound form a protective layer around the solvated structure, reducing the gassing phenomenon of the battery.

[0060] In summary, the ether-based solvent allows the battery to have excellent normal temperature cycle performance and high temperature cycle performance, and a low amount of high temperature gas generation.

[0061] In some embodiments, the volume ratio Y of the diluent to the solvent is 0.5 to 7. In some embodiments, the volume ratio Y of the diluent to the solvent 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, 0.5 to 7, 1 to 1.5, 1 to 2, 1 to 2.5, 1 to 3, or 1 to 3.5. , 1~4, 1~4.5, 1~5, 1~5.5, 1~6, 1~6.5, 1~7, 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, 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, 2.5~3, 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, 3~3.5, 3~4, 3~4.5, 3~5, 3~5.5, 3~6, ​​3~6.5, 3~7, 3.5~4, 3.5~4.5, 3.5~5, 3.5~5.5, 3.5~6 , 3.5~6.5, 3.5~7, 4~4.5, 4~5, 4~5.5, 4~6, 4~6.5, 4~7, 4.5~5, 4.5~5.5, 4.5~6, 4.5~6.5, 4.5~7, 5~5.5, 5~6, 5~6.5, 5~7, 5.5~6, 5.5~6.5, 5.5~7, 6~6.5, 6~7, 6.5~7.

[0062] When the volume ratio of the diluent to the solvent is within an appropriate range, 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 high-temperature cycle performance and safety performance of the battery can be improved.

[0063] In some embodiments, the ratio Y of the volume of the diluent to the solvent is 1 to 5. In some embodiments, the ratio Y of the volume of the diluent to the solvent is optionally 1 to 1.5, 1 to 2, 1 to 2.5, 1 to 3, 1 to 3.5, 1 to 4, 1 to 4.5, 1 to 5, 1.5 to 2, 1.5 to 2.5, 1.5 to 3, 1.5 to 3.5, 1.5 to 4, 1.5 to 4.5, 1.5 to 5, 2 to 2.5, 2 to 3, 2 to 3.5, 2 to 4, or 2 to 4.5. , 2~5, 2.5~3, 2.5~3.5, 2.5~4, 2.5~4.5, 2.5~5, 3~3.5, 3~4, 3~4.5, 3~5, 3.5~4, 3.5~4.5, 3.5~5, 3.5~5.5, 3.5~6, 4~4.5, 4~5, 4~5.5, 4~6, 4.5~5, 4.5~5.5, 4.5~6.

[0064] When the volume ratio of the diluent to the solvent is within an appropriate range, the 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 operating temperature of the battery can be expanded.

[0065] In some embodiments, the electrolyte comprises a sodium salt; The electrolyte satisfies the relationship 5 / (1+Y)≦X≦50 / (1+Y), where X% is the mass content of the sodium salt, based on the total mass of the electrolyte, and Y is the volume ratio of the diluent to the solvent.

[0066] In some embodiments, the electrolyte contains a sodium salt, and the electrolyte satisfies any one of the following relational expressions: 5 / (1 + Y) ≤ X ≤ 10 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 15 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 20 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 25 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 30 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 35 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 40 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 5 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 15 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 20 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 25 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 30 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 35 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 40 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 10 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 15 / (1 + Y) ≤ X ≤ 20 / (1 + Y), 15 / (1 + Y) ≤ X ≤ 25 / (1 + Y), 15 / (1 + Y) ≤ X ≤ 30 / (1 + Y), 15 / (1 + Y) ≤ X ≤ 35 / (1 + Y), 15 / (1 + Y) ≤ X ≤ 40 / (1 + Y), 15 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 15 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 20 / (1 + Y) ≤ X ≤ 25 / (1 + Y), 20 / (1 + Y) ≤ X ≤ 30 / (1 + Y), 20 / (1 + Y) ≤ X ≤ 35 / (1 + Y), 20 / (1 + Y) ≤ X ≤ 40 / (1 + Y), 20 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 20 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 25 / (1 + Y) ≤ X ≤ 30 / (1 + Y), 25 / (1 + Y) ≤ X ≤ 35 / (1 + Y), 25 / (1 + Y) ≤ X ≤ 40 / (1 + Y), 25 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 25 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 30 / (1 + Y) ≤ X ≤ 35 / (1 + Y), 30 / (1 + Y) ≤ X ≤ 40 / (1 + Y), 30 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 30 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 35 / (1 + Y) ≤ X ≤ 40 / (1 + Y), 35 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 35 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 40 / (1 + Y) ≤ X ≤ 45 / (1 + Y), 40 / (1 + Y) ≤ X ≤ 50 / (1 + Y), 45 / (1 + Y) ≤ X ≤ 50 / (1 + Y).

[0067] The sodium salt and the solvent are involved in the formation of a solvated structure of sodium ions, while the diluent forms a protective layer around the solvated structure. To ensure that the protective layer formed by the solvated structure and the diluent reaches an optimal blend ratio, the sodium salt, the solvent, and the diluent must form an effective blend.

[0068] The applicant unexpectedly discovered that by controlling the mass content of the sodium salt (X%) relative to the total mass of the electrolyte and the volume ratio Y of the diluent to the solvent so that 5 / (1+Y)≦X≦50 / (1+Y), an optimal blend ratio of the diluent to the solvated structure can be achieved, and the diluent can form a protective layer around the solvated structure, thereby improving the room temperature cycling performance of the battery and improving the electrochemical performance of the battery.

[0069] In some embodiments, the sodium salts include one or more of sodium perchlorate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium trifluoroacetate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide.

[0070] In some embodiments, a sodium secondary battery is provided, the sodium secondary battery including the electrolyte of any of the embodiments.

[0071] 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.

[0072] 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.

[0073] The undercoating has the characteristic of low metal nucleation potential, which can effectively improve the deposition / dissolution performance of sodium metal, as well as reduce the large volume change that the sodium metal deposition / dissolution process brings to the battery core, stabilize the battery core structure, 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] In some embodiments, the areal density of the undercoating is between 5 and 50 g / m 2 In some embodiments, the areal density of the undercoating is preferably 5 to 10 g / m 2 , 5 to 20 g / 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 / m 2 , 20~50g / m 2 , 30-40g / m 2 , 30~50g / m 2 , 40~50g / m 2 It is one of the following.

[0075] An appropriate range of undercoating area density can optimize the metal deposition effect, improve the high-temperature cycle performance and room-temperature cycle performance of the battery, and reduce the high-temperature gas generation phenomenon of the battery. At the same time, an appropriate range of undercoating area density can increase the energy density of the battery and meet the usage demands of the battery.

[0076] In some embodiments, the undercoating comprises one or more of a carbon coating, an alloy coating, and a metal oxide coating.

[0077] In some embodiments, the undercoating comprises a carbon coating.

[0078] In some embodiments, the undercoating comprises one or more of superconducting carbon black, ketjen black, acetylene black, carbon nanotubes, and graphene.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] In some embodiments, the undercoating is a metal oxide coating, and the oxide comprises at least one of copper oxide and aluminum oxide.

[0083] In some embodiments, the undercoating is a conductive polymer coating, and the conductive polymer comprises any one of polyaniline, polythiophene, polypyrrole, and polyphenylene vinylene.

[0084] In some embodiments, the undercoating is a conductive ceramic coating, and the conductive ceramic material comprises at least one of TiB2, TiC, and B4C3.

[0085] 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.

[0086] In some embodiments, the sodium secondary battery is a non-anode sodium metal battery.

[0087] In some embodiments, the sodium 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.

[0088] 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 at high temperatures.

[0089] In some embodiments, the CB value of the anode-less sodium metal battery is 0.1 or less.

[0090] 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.

[0091] 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.

[0092] [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.

[0093] 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。

[0094] 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

[0095] 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。

[0096] 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.

[0097] 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).

[0098] 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.

[0099] 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.

[0100] [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.

[0101] 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.

[0102] In some embodiments, the positive and negative electrodes and the separator can be fabricated into an electrode assembly by a winding or lamination process.

[0103] In some embodiments, the sodium secondary battery may include an outer casing, which may be used to package the electrode assembly and the electrolyte.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] The power consumption device can be selected as a sodium secondary battery, a battery module, or a battery pack depending on its usage needs.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 1. Manufacturing method Example 1 1) Electrolyte production In an argon gas atmosphere glove box with a water content of <10 ppm, sodium hexafluorophosphate (NaPF6) was dissolved in ethylene glycol dimethyl ether (DME) and stirred to obtain a mixed solution. Methyltrimethoxysilane and the mixed solution were then mixed to obtain an electrolyte, where the volume ratio of methyltrimethoxysilane to ethylene glycol dimethyl ether was 1.5, and the mass content of sodium hexafluorophosphate was 7% based on the total mass of the electrolyte.

[0118] 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 90%:6%:4% 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.

[0119] 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 a negative electrode current collector, dried, and cut to obtain a negative electrode plate with a no-anode structure, where the areal density of the undercoating was 20 g / m. 2 Okay.

[0120] 4) Separator A polyethylene film (PE separator) was used as the separator.

[0121] 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.

[0122] Examples 2 to 27 Except for the different electrolyte formulations and / or manufacturing parameters of the negative electrode plates, the other steps of Examples 2 to 27 are the same as those of Example 1. Here, the manufacturing methods of the negative electrode plates of Examples 26 and 27 are as follows, and the specific parameters are as shown in Table 1.

[0123] Example 26: 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.

[0124] Example 27: The negative electrode plate is aluminum foil. The specific parameters are as shown in Table 1.

[0125] Comparative Examples 1 to 3 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 2 is the same as the manufacturing method of the negative electrode plate of Example 26, and Comparative Example 3 is the same as the manufacturing method of the negative electrode plate of Example 27, and the specific parameters are as shown in Table 1.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] The test procedures for the comparative example and other examples were the same as those described above.

[0130] 3. Test results The test results for the above examples and comparative examples are shown in Table 1.

[0131] [Table 1-1] [Table 1-2] [Table 1-3]

[0132] As can be seen from the above results, the sodium secondary battery electrolytes in Examples 1 to 27 all contain a diluent, and the diluent includes methyltrimethoxysilane, trimethylmethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, or tetraethoxysilane. As can be seen from comparisons between Examples 1 to 25 and Comparative Example 1, and between Examples 26 to 27 and Comparative Examples 2 and 3, sodium secondary battery electrolytes containing an alkylalkoxysilane compound were able to reduce the high-temperature expansion rate of the battery, reduce the high-temperature gas generation phenomenon in the battery, and improve the safety of the battery.

[0133] The electrolytes in Examples 1 to 27 further contained an ether solvent such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, or tetraethylene glycol dimethyl ether, and the batteries had excellent room temperature cycle performance and high temperature cycle performance, and low high-temperature gas generation.

[0134] As can be seen from the comparison between Examples 1, 7-10 and Example 11, when the volume ratio Y of the methyltrimethoxysilane diluent to the ethylene glycol dimethyl ether solvent is 0.5-7, 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 cycle performance and safety performance of the battery at high temperatures can be improved.

[0135] As can be seen from the comparison between Examples 1, 8-9 and Examples 7, 10-11, when the volume ratio Y of the methyltrimethoxysilane diluent to the ethylene glycol dimethyl ether solvent is 1-5, the 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 operating temperature of the battery can be expanded.

[0136] As can be seen from a comparison of Examples 1 to 6, 8 to 16, 18 to 20, and 22 to 25 with Examples 7, 17, and 21, by controlling the mass content X% of the sodium salt based on the total mass of the electrolyte and the volume ratio Y of the diluent to the solvent so as to satisfy 5 / (1+Y)≦X≦50 / (1+Y), the room temperature cycle performance of the battery could be improved, and the electrochemical performance of the battery could be improved.

[0137] As can be seen from the comparison between Examples 1 and 26 and Example 27, 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 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.

[0138] As can be seen from the comparison between Examples 1, 22-23 and Examples 24-25, the areal density of the undercoating is 5-50 g / m 2 This 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.

[0139] As can be seen from the comparison between Example 1 and Example 26, the sodium secondary battery is a negative electrode-less sodium metal battery, and it has been 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.

[0140] 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]

[0141] 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 a diluent, wherein the diluent comprises an alkylalkoxysilane compound.

2. the diluent comprises one or more compounds of Formula I, Formula II, Formula III or Formula IV; Here, R 1 is C 1 -C 10 alkyl groups, R 2 is C 1 -C 6 2. The electrolyte of claim 1, wherein the alkyl group is selected from the group consisting of alkyl groups.

3. 3. The electrolyte of claim 1 or 2, wherein the diluent comprises one or more of methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, and optionally one or more of methyltrimethoxysilane, methyltriethoxysilane, and tetraethoxysilane.

4. 4. The electrolyte according to claim 1, further comprising a solvent, wherein a volume ratio Y of the diluent to the solvent is 0.5 to 7, optionally 1 to 5.

5. The electrolyte according to claim 4 , wherein the solvent comprises an ether-based solvent.

6. 6. The electrolyte of claim 4 or 5, wherein the solvent comprises one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, and optionally one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetraethylene glycol dimethyl ether.

7. the electrolyte comprises a sodium salt; the electrolyte satisfies the relational expression 5 / (1+Y)≦X≦50 / (1+Y), 7. The electrolyte according to claim 4, wherein X% is the mass content of the sodium salt, based on the total mass of the electrolyte, and Y is the volume ratio of the diluent to the solvent.

8. 8. The electrolyte of claim 7, wherein the sodium salt comprises one or more of sodium perchlorate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium trifluoroacetate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide.

9. A sodium secondary battery comprising the electrolyte according to any one of claims 1 to 8.

10. 10. The sodium secondary battery according to claim 9, wherein the 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.

11. The surface density of the undercoating is 5 to 50 g / m 2 11. The sodium secondary battery according to claim 10, wherein

12. 12. The sodium secondary battery according to claim 10, wherein the undercoating comprises one or more of a carbon coating, an alloy coating, and a metal oxide coating, and is optionally a carbon coating.

13. 13. The sodium secondary battery according to claim 10, wherein the undercoating contains one or more of superconducting carbon black, ketjen black, acetylene black, carbon nanotubes, and graphene.

14. 14. The sodium secondary battery according to claim 9, wherein the sodium secondary battery is a non-negative electrode sodium metal battery.

15. A power consuming device comprising the sodium secondary battery according to any one of claims 9 to 14.

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