Sodium secondary battery, battery module, battery pack, and power consumption device

Abstract

This application provides a sodium secondary battery, a battery module, a battery pack, and a power consumption device. The sodium secondary battery includes a positive electrode plate, a negative electrode plate, a first electrolyte located on the positive electrode plate side, and a second electrolyte located on the negative electrode plate side, the first electrolyte and the second electrolyte containing different organic solvents, the first electrolyte containing an ester-based solvent, a sulfone-based solvent, or a fluoroether-based solvent, and the second electrolyte containing an ether-based solvent or an amide-based solvent. The combination of different organic solvents with the positive and negative electrodes reduces gas generation and expansion of the battery, while optimizing the electrochemical stability window width of the battery, improving the cycle stability of the battery, and further enhancing the overall performance of the battery.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application incorporates by reference Chinese patent application No. 202310070478.0, entitled "Sodium Secondary Battery, Battery Module, Battery Pack and Power Consumption Device," filed on January 16, 2023, which is incorporated herein by reference in its entirety. [Technical Field]

[0002] The present application relates to the field of secondary batteries, and in particular to sodium secondary batteries, battery modules, battery packs and power consuming devices. [Background technology]

[0003] Sodium batteries have great potential for application in large-scale energy storage due to their abundant reserves, relatively low price and wide operating temperature range.

[0004] The compatibility of the electrolyte solvent with the positive and negative electrodes has an important impact on the overall performance of the battery. However, conventional solvents have difficulty in simultaneously matching both the positive and negative electrode active materials. For example, the use of a fluoroether-based solvent in the electrolyte in combination with a high-potential positive electrode material can improve battery stability. However, the fluoroether-based solvent is prone to react with the sodium metal at the negative electrode, which affects the storage performance of the battery and fails to meet the application needs of next-generation electrochemical systems. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and its object is to provide a sodium secondary battery, which includes a first electrolyte and a second electrolyte containing different organic solvents, and by combining different organic solvents with positive and negative electrode plates, respectively, gas generation expansion of the battery is reduced, the electrochemical stability window width of the battery is optimized, the cycle stability of the battery is improved, and the overall performance of the battery is further enhanced.

[0006] A first aspect of the present application provides a sodium secondary battery, the sodium secondary battery including a positive electrode plate, a negative electrode plate, a first electrolyte located on the positive electrode plate side, and a second electrolyte located on the negative electrode plate side, the first electrolyte and the second electrolyte including different organic solvents, the first electrolyte including an ester-based solvent, a sulfone-based solvent, or a fluoroether-based solvent, and the second electrolyte including an ether-based solvent or an amide-based solvent.

[0007] By combining a first electrolyte and a second electrolyte containing different organic solvents on the positive and negative electrode plates, respectively, the high voltage advantages of the positive electrode active material can be fully utilized, and the drawback of high voltage-resistant solvents being highly reactive at the negative electrode can be overcome, reducing the amount of gas generated by the battery, optimizing the width of the electrochemical stability window of the battery, improving the high-pressure cycle stability of the battery, and further enhancing the overall performance of the battery.

[0008] The first electrolyte contains an ester solvent, a sulfone solvent, or a fluoroether solvent, and the second electrolyte contains an ether solvent or an amide solvent, which fully utilizes the advantages of each solvent, thereby reducing gas generation and expansion of the battery, optimizing the electrochemical stability window width of the battery, improving the high-pressure cycle stability of the battery, and further enhancing the overall performance of the battery.

[0009] In either embodiment, there is at least one interface between the first electrolyte and the second electrolyte.

[0010] By having at least one interface between the first electrolyte and the second electrolyte, the first electrolyte and the second electrolyte cannot form a homogeneous phase but each become a single phase independent of each other, and further, contact between the positive electrode plate and the second electrolyte is avoided to reduce decomposition of the second electrolyte at the positive electrode, and contact between the negative electrode plate and the first electrolyte is avoided to reduce active reactions of the first electrolyte at the negative electrode.

[0011] In any embodiment, the mass ratio of the first electrolyte to the second electrolyte is 2 / 8 to 8 / 2.

[0012] Controlling the mass ratio of the first electrolyte to the second electrolyte within an appropriate range is advantageous for widening the electrochemical window of the battery, improving the cycle performance and storage performance of the battery, reducing the gas generation rate of the battery, and enhancing the safety of the battery.

[0013] In any embodiment, the first electrolyte and the second electrolyte are separated by a first separator, which includes at least one of a sodium ion-substituted perfluorosulfonic acid resin film, a sodium fast ion conductor solid electrolyte, and an oxide solid electrolyte.

[0014] After sodium ion substitution, the perfluorosulfonic acid resin film (Nafion), the sodium fast ion conductor solid electrolyte, and the oxide solid electrolyte can maintain the separation between the first and second electrolytes and prevent their interpenetration, forming a dual-cavity battery structure. However, they realize the exchange of sodium ions between the first and second electrolytes, making the chemical reaction reversible, allowing the battery to be repeatedly charged.

[0015] In any embodiment, the sodium fast ion conductor solid electrolyte is Na 3+x M y M´ 2-y Si 2-z P z O 12 wherein M and M' may independently comprise at least one selected from Zr, Ca, Mg, Zn, La, Ti, and Nb, and 0≦x<1, 0≦y<2, and 0≦z<2; the oxide solid electrolyte comprises at least one of Na-β-Al2O3 and Na-β″-Al2O3, the Na-β-Al2O3 comprising β-Na2O 11Al2O3, and the Na-β″-Al2O3 comprising β″-Na2O 5Al2O3.

[0016] The perfluorosulfonic acid resin film, sodium fast ion conductor solid electrolyte, and oxide solid electrolyte can effectively isolate the solvent without impeding the transport of sodium ions, which is advantageous for increasing the electrochemical stability window width of the battery, reducing the storage expansion rate of the battery, widening the electrochemical window of the battery, reducing the gas generation rate of the battery, and improving the safety of the battery.

[0017] In any embodiment, the sodium secondary battery includes at least two layers of a second separator, the first electrolyte and the second electrolyte are respectively infiltrated on different layers of the second separator, the second separator includes at least one of a polyethylene film, a polypropylene film, and a glass fiber film, and the added volume V per unit capacity of the first electrolyte and the second electrolyte is 3 μL / mAh or less. <V<10μL / mAhである。

[0018] By ensuring that the volume V of the first and second electrolytes added per unit volume falls within the lean electrolyte range, almost all of the electrolyte is adsorbed onto the second separator, reducing the amount of free-flowing electrolyte, thereby preventing interpenetration between the first and second electrolytes. Adding small amounts of the first and second electrolytes in drops provides isolation between the two, widening the electrochemical window of the battery, improving cycle stability, reducing gas generation, and enhancing battery safety.

[0019] In either embodiment, the viscosity of the first electrolyte and the viscosity of the second electrolyte are both greater than 500 mPa·s, and optionally greater than 1000 mPa·s.

[0020] Both the first electrolyte and the second electrolyte have high viscosity and low fluidity, so that they form a clear phase interface, making it difficult for mutual infiltration to occur, and enabling phase separation to be achieved.

[0021] In any embodiment, the first electrolyte and the second electrolyte both contain a sodium salt, and the mass content of the sodium salt in the first electrolyte and the second electrolyte is 2% to 70%, and optionally 15% to 20%, based on the total mass of the first electrolyte and the second electrolyte, respectively.

[0022] The mass content of the sodium salt in each of the first and second electrolytes is controlled to 2% to 70%, based on the total mass of the first and second electrolytes, respectively, thereby broadening the application field of sodium secondary batteries. The mass content of the sodium salt in each of the first and second electrolytes is controlled to 15% to 20%, based on the total mass of the first and second electrolytes, respectively, thereby further widening the electrochemical window of the battery, improving the cycle stability of the battery, reducing the gas generation rate of the battery, and improving the safety of the battery.

[0023] In any embodiment, the sodium salts include one or more of sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium tetrafluoroyttriate, sodium hexafluoroarsenate, sodium acetate, sodium trifluoroacetate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium (n-perfluorobutylsulfonyl)imide, and optionally one or more of sodium hexafluorophosphate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, and optionally one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[0024] All of the above sodium salts are advantageous in widening the electrochemical window of the battery, improving the storage performance of the battery, reducing the gas generation rate of the battery, and improving the safety of the battery.

[0025] In any embodiment, the first electrolyte and / or the second electrolyte includes a polymer, and the mass content of the polymer in each of the first electrolyte and the second electrolyte is 2% to 30%, and optionally 10% to 20%, based on the total mass of the first electrolyte and the second electrolyte, respectively.

[0026] Introducing a polymer into the first electrolyte and / or the second electrolyte effectively reduces the fluidity between the first and second electrolytes, achieving separation between the first and second electrolytes while simultaneously weakening the solvation effect of sodium ions, further reducing the gassing rate and improving the storage performance and safety of the battery. Controlling the polymer mass content in both the first and second electrolytes to 2% to 30% based on the total mass of the first and second electrolytes, respectively, is advantageous for widening the electrochemical window of the battery, improving the cycle performance and storage performance of the battery, reducing the gassing rate of the battery, and improving battery safety. Controlling the polymer mass content in both the first and second electrolytes to 10% to 20% based on the total mass of the first and second electrolytes, respectively, is advantageous for widening the electrochemical window of the battery, improving the cycle performance and storage performance of the battery, reducing the gassing rate of the battery, and further improving battery safety.

[0027] In any embodiment, the polymer comprises one or more of polyethylene oxide, polyethylene glycol, polyvinylpyrrolidone, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyvinyl chloride, polyacrylamide, polytrimethylene carbonate, and perfluoropolyether.

[0028] All of the above polymers are advantageous in widening the electrochemical window of the battery, improving the cycle performance and storage performance of the battery, and reducing the gas generation rate of the battery, thereby improving the safety of the battery.

[0029] In any embodiment, the ester-based solvent comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), γ-butyrolactone (BL), 1,3-propane sultone (1,3-PS), methyl propionate (MP), methyl butyrate (MB), ethyl acetate (EA), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate (EB); The sulfone solvent may comprise one or more of dimethyl sulfoxide (DMSO), methyl ethyl sulfone (EMS), ethyl isopropyl sulfone (EIS), ethyl vinyl sulfone (EVS), sulfolane (SL), trifluoromethyl ethyl sulfone (FMES), trifluoromethyl propyl sulfone (FMPS), 1,1,1-trifluoro-3-(methylsulfonyl)propane (FPMS), 1,1,1-trifluoro-2-(methylsulfonyl)ethane (TFEMS), and 1,1,2,2-tetrafluoro-3-(methylsulfonyl)propane (TFPMS); The fluoroether solvents include 2,2,3,3-tetrafluoro-1,4-dimethoxybutane (FDMB), 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane (F3DEE), 1,2-bis(2,2-difluoroethoxy)ethane (F4DEE), 2-(2-(2,2-difluoroethoxy)ethoxy)-1,1,1-trifluoroethane (F5DEE), 1,2-bis(2,2,2-trifluoroethoxy)ethane (F6DEE), 1,1,1,3,3,3-hexafluoroisopropyl methyl ether (HME), methyl ether 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether (THE), 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane (DTDOL), 2-ethoxy-4-(trifluoromethyl)-1,3-dioxopentane (ETDOL), octafluorotetrahydrofuran (PFTHF), The ether solvent may include one or more of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), ethylene glycol diethyl ether (DEE), diethylene glycol diethyl ether (DEGDEE), diisopropyl ether (DIE), dibutyl ether (DBE), diethylene glycol dibutyl ether (DEGDBE), 1,4-dimethoxybutane (DMB), 1,4-diethoxybutane (DEB), 1,3-dioxolane (DOL), tetrahydrofuran (THF), 15-crown ether-5 (15-Crown-5), 12-crown ether-4 (12-Crown-4), and 18-crown ether-6 (18-Crown-6); The amide solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N,N-dimethylacetoacetamide (DMAA), 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide (DMCF3SA), N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), 2,3,6-trifluorobenzenesulfonamide (TFBFSA), N,N-dimethyl - 4-Fluorobenzenesulfonamide (DMFBFSA), N-methyl-N-trimethylsilane trifluoroacetamide (MSTFA).

[0030] By using the above ester-based solvents, sulfone-based solvents, fluoroether-based solvents, ether-based solvents, or amide-based solvents in combination, the high-voltage cycle stability, storage performance, and safety of sodium secondary batteries can be effectively improved, and the applications of sodium secondary batteries can be expanded.

[0031] In any embodiment, the sodium secondary battery is a sodium metal battery.

[0032] In any embodiment, the sodium secondary battery is a non-negative electrode sodium secondary battery.

[0033] In any embodiment, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a transition metal layered oxide, a polyanionic compound, and a Prussian blue compound, and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na(Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 )O2, Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 O2, Na4Fe3(PO4)2P2O7, NaFePO4, Na3V2(PO4)3, Na 1.9It includes one or more of CoFe(CN)6, Na2NiFe(CN)6, and NaMnFe(CN)6.

[0034] All of the above positive electrode active materials are advantageous in widening the electrochemical window of the battery, improving the storage performance of the battery, reducing the gas generation rate of the battery, and improving the safety of the battery.

[0035] In any embodiment, the surface of the positive electrode active material has a coating layer, and the coating layer includes one or more of a carbon material, ZrO, TiO, polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride, and the carbon material includes one or more of amorphous carbon, graphite, and graphene.

[0036] The coating layer contains a positive electrode active material, which is advantageous in improving the high voltage cycle stability and storage performance of the battery.

[0037] In any embodiment, the thickness of the coating layer is between 2 nm and 1000 nm, and optionally between 10 nm and 100 nm.

[0038] Controlling the thickness of the coating layer within an appropriate range is advantageous for improving the high voltage cycle stability and electrical performance of the battery.

[0039] In any embodiment, the negative electrode plate includes a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, the undercoating including one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

[0040] The undercoating not only has excellent electrical conductivity but also favors uniform deposition of metal ions on the surface of the current collector, improving the cycle performance and safety of the battery.

[0041] In any embodiment, the areal density of the undercoating is less than 5 g / m 2 ~50g / m 2 is.

[0042] Surface density is 5g / m 2 ~50g / m 2 The undercoating favors a uniform distribution of nucleation sites, promotes uniform deposition of the metal, and does not affect the electron transport behavior.

[0043] In any embodiment, the undercoating has a thickness of 2 μm to 100 μm.

[0044] The thickness of the undercoating can be controlled to be 2 μm to 100 μm, which can provide sufficient nucleation sites, favor the uniform deposition of metal ions, and suppress dendrites.

[0045] A second aspect of the present application provides a battery module, which includes the sodium secondary battery of the first aspect of the present application.

[0046] A third aspect of the present application provides a battery pack, which includes the sodium secondary battery of the first aspect of the present application or the battery module of the second aspect of the present application.

[0047] A fourth aspect of the present application provides a power consumption device, the power consumption device including at least one of the sodium secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, and the battery pack of the third aspect of the present application. [Brief explanation of the drawings]

[0048] [Figure 1] 1 is a schematic diagram of a sodium secondary battery according to an embodiment of the present application. [Figure 2] 1 is a schematic diagram of a sodium secondary battery according to an embodiment of the present application. [Figure 3]FIG. 3 is an exploded view of the sodium secondary battery shown in FIG. 2 according to the embodiment of the present application. [Figure 4] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 5] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 6] FIG. 6 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. 5. [Figure 7] 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

[0049] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the sodium 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 and 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.

[0050] 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.

[0051] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0052] 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.

[0053] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0054] 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.

[0055] 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).

[0056] In conventional technology, the combination of electrolyte solvents and positive and negative electrode materials affects the performance of sodium batteries. For example, in sodium metal batteries or anode-less sodium secondary batteries, polyanionic compounds or high-energy-density transition metal layered oxides are often used as positive electrode materials. During the charge and discharge process of sodium metal or sodium batteries, a sodium metal phase is deposited on the negative electrode side as the negative electrode material. The transition metal layered oxide has a high working potential as a positive electrode material. Ether-based solvents have relatively low reactivity with sodium metal on the negative electrode side, but cannot withstand high voltages on the positive electrode side, affecting battery stability. Fluoroether-based solvents still have excellent stability under high voltages on the positive electrode side, but have relatively high reactivity with sodium metal on the negative electrode side, affecting the storage performance and service life of the battery. Therefore, new electrolyte systems need to be developed to enable sodium batteries to meet the application needs of next-generation electrochemical systems.

[0057] [Sodium secondary battery] Based on this, the present application proposes a sodium secondary battery, which includes a positive electrode plate, a negative electrode plate, a first electrolyte located on the positive electrode plate side, and a second electrolyte located on the negative electrode plate side, and the first electrolyte and the second electrolyte include different organic solvents.

[0058] As used herein, the term "sodium secondary battery" refers to a secondary battery that uses sodium ions as a carrier. The negative electrode active material in a sodium secondary battery may be any material, including, but not limited to, hard carbon, sodium metal, transition metal oxides, transition metal selenides, and alloys. Here, the sodium metal may be sodium metal pre-deposited on the negative electrode plate before packaging the battery, or sodium metal deposited on the negative electrode during the battery cycling process. A secondary battery that uses a current collector as the negative electrode before packaging the battery and does not pre-deposit sodium metal on the negative electrode plate is called a non-negative electrode sodium secondary battery, and is also a type of sodium secondary battery.

[0059] In some embodiments, the structure of a sodium secondary battery according to the present application is as shown in Figure 1. Sodium secondary battery 6 includes a positive electrode plate 61, a negative electrode plate 62, a first electrolyte 631 located on the positive electrode plate 61 side, and a second electrolyte 632 located on the negative electrode plate 62 side, with different organic solvents being included in first electrolyte 631 located on the positive electrode plate 61 side and second electrolyte 632 located on the negative electrode plate 62 side, thereby allowing different solvents to be matched according to the characteristics of the positive electrode active material on positive electrode plate 61 and the negative electrode active material on negative electrode plate 62, not only making full use of the high voltage advantages of the positive electrode active material but also overcoming the drawback of high reactivity at the negative electrode of solvents that can withstand high voltage.

[0060] This secondary battery includes a first electrolyte and a second electrolyte containing different organic solvents, and by combining different organic solvents with the positive and negative electrode plates, it is possible to reduce negative electrode gas generation expansion, optimize the electrochemical stability window of the battery, improve the high-pressure cycle stability of the battery, and further enhance the overall performance of the battery.

[0061] In some embodiments, the first electrolyte includes an ester-based solvent, a sulfone-based solvent, or a fluoroether-based solvent, and the second electrolyte includes an ether-based solvent or an amide-based solvent.

[0062] As used herein, the term "ester solvent" refers to an organic solvent that contains an ester group, which may or may not be substituted with a functional group.

[0063] As used herein, the term "sulfonic solvent" refers to an organic solvent that contains a sulfonic group, which may or may not be substituted with a functional group.

[0064] As used herein, the term "ether-based solvent" refers to a solvent whose molecules are ether-based compounds, and the ether-based solvent molecules do not contain the element fluorine.

[0065] As used herein, the term "fluoroether solvent" refers to a solvent of an ether-based compound containing the element fluorine. In some embodiments, the fluoroether solvent is obtained after direct fluorine substitution modification of the ether-based solvent molecule.

[0066] The fluoroether solvent in the electrolyte solution of the present application is not an inert fluoroether solvent with high steric hindrance, but a fluoroether solvent that can form a first solvation layer with the sodium salt in the electrolyte solution. In some embodiments, the solubility of sodium hexafluorophosphate in the fluoroether solvent is greater than 16 g at 25° C. In some embodiments, the solubility of sodium bis(fluorosulfonyl)imide salt in the fluoroether diluent is greater than 40 g at 25° C. Due to the relatively strong interaction between the fluoroether solvent and the sodium salt, which can participate in the first solvation layer, the sodium salt has high solubility in the corresponding fluoroether solvent.

[0067] As used herein, the term "amide solvent" refers to an organic solvent that contains an amide group, which may or may not be substituted with a functional group.

[0068] In some embodiments, the organic solvent in the first electrolyte comprises an ester-based solvent and the organic solvent in the second electrolyte comprises an ether-based solvent. In some embodiments, the organic solvent in the first electrolyte comprises an ester-based solvent and the organic solvent in the second electrolyte comprises an amide-based solvent. In some embodiments, the organic solvent in the first electrolyte comprises a sulfone-based solvent and the organic solvent in the second electrolyte comprises an ether-based solvent. In some embodiments, the organic solvent in the first electrolyte comprises a fluoroether-based solvent and the organic solvent in the second electrolyte comprises an ether-based solvent. In some embodiments, the organic solvent in the first electrolyte comprises a sulfone-based solvent and the organic solvent in the second electrolyte comprises an amide-based solvent. In some embodiments, the organic solvent in the first electrolyte comprises a fluoroether-based solvent and the organic solvent in the second electrolyte comprises an amide-based solvent.

[0069] Ester-based solvents, sulfone-based solvents, and fluoroether-based solvents all have relatively high highest occupied molecular orbital (HOMO) levels and can withstand the high operating potential of the positive electrode active material. However, ester-based solvents, sulfone-based solvents, and fluoroether-based solvents also exhibit higher reactivity with negative electrode sodium metal. Ether-based solvents and amide-based solvents have relatively high stability with negative electrode sodium metal.

[0070] Therefore, when the first electrolyte contains an ester solvent, a sulfone solvent, or a fluoroether solvent, and the second electrolyte contains an ether solvent or an amide solvent, the advantages of each solvent are fully utilized, which can reduce gas generation and expansion of the battery, optimize the electrochemical stability window width of the battery, improve the high-pressure cycle stability of the battery, and further enhance the overall performance of the battery.

[0071] In some embodiments, the ester-based solvent comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), γ-butyrolactone (BL), 1,3-propane sultone (1,3-PS), methyl propionate (MP), methyl butyrate (MB), ethyl acetate (EA), ethyl propionate (EP), propyl propionate (PP), and ethyl butyrate (EB).

[0072] In some embodiments, the sulfone solvent comprises one or more of dimethyl sulfoxide (DMSO), methyl ethyl sulfone (EMS), ethyl isopropyl sulfone (EIS), ethyl vinyl sulfone (EVS), sulfolane (SL), trifluoromethyl ethyl sulfone (FMES), trifluoromethyl propyl sulfone (FMPS), 1,1,1-trifluoro-3-(methylsulfonyl)propane (FPMS), 1,1,1-trifluoro-2-(methylsulfonyl)ethane (TFEMS), 1,1,2,2-tetrafluoro-3-(methylsulfonyl)propane (TFPMS).

[0073] In some embodiments, the fluoroether solvent is 2,2,3,3-tetrafluoro-1,4-dimethoxybutane (FDMB, [ka] ), 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane (F3DEE, [ka] ), 1,2-bis(2,2-difluoroethoxy)ethane (F4DEE, [ka] ), 2-(2-(2,2-difluoroethoxy)ethoxy)-1,1,1-trifluoroethane (F5DEE, [ka] ), 1,2-bis(2,2,2-trifluoroethoxy)ethane (F6DEE, [ka] ), 1,1,1,3,3,3-hexafluoroisopropyl methyl ether (HME), methyl ether 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether (THE), 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane (DTDOL), 2-ethoxy-4-(trifluoromethyl)-1,3-dioxopentane (ETDOL), octafluorotetrahydrofuran (PFTHF).

[0074] In some embodiments, the ether solvent comprises one or more of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), ethylene glycol diethyl ether (DEE), diethylene glycol diethyl ether (DEGDEE), diisopropyl ether (DIE), dibutyl ether (DBE), diethylene glycol dibutyl ether (DEGDBE), 1,4-dimethoxybutane (DMB), 1,4-diethoxybutane (DEB), 1,3-dioxolane (DOL), tetrahydrofuran (THF), 15-crown ether-5 (15-Crown-5), 12-crown ether-4 (12-Crown-4), and 18-crown ether-6 (18-Crown-6).

[0075] In some embodiments, the amide solvent is N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N,N-dimethylacetoacetamide (DMAA), 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide (DMCF3SA), N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), 2,3,6-trifluorobenzenesulfonamide (TFBFSA), N,N-dimethyl - 4-Fluorobenzenesulfonamide (DMFBFSA), N-methyl-N-trimethylsilane trifluoroacetamide (MSTFA).

[0076] In some embodiments, there is at least one interface between the first electrolyte and the second electrolyte.

[0077] In some embodiments, there is a single layer interface between the first electrolyte and the second electrolyte, and in some embodiments, there is a double or more layer interface between the first electrolyte and the second electrolyte.

[0078] The interface between the first electrolyte and the second electrolyte may be formed in any manner. In some embodiments, the first electrolyte and the second electrolyte are in contact with each other but have a distinct interphase therebetween. In some embodiments, the first electrolyte and the second electrolyte are prevented from directly contacting each other by forming multiple interfaces via spacers.

[0079] By having at least one interface between the first electrolyte and the second electrolyte, the first electrolyte and the second electrolyte cannot form a homogeneous phase but each become a single phase independent of each other, and further, contact between the positive electrode plate and the second electrolyte is avoided to reduce decomposition of the second electrolyte at the positive electrode, and contact between the negative electrode plate and the first electrolyte is avoided to reduce active reactions of the first electrolyte at the negative electrode.

[0080] In some embodiments, the mass ratio of the first electrolyte to the second electrolyte is between 2 / 8 and 8 / 2.

[0081] In some embodiments, the mass ratio of the first electrolyte to the second electrolyte is optionally 2 / 8, 3 / 7, 4 / 6, 5 / 5, 6 / 4, 7 / 3, or 8 / 2.

[0082] Controlling the mass ratio of the first electrolyte to the second electrolyte within an appropriate range is advantageous for widening the electrochemical window of the battery, improving the cycle performance and storage performance of the battery, reducing the gas generation rate of the battery, and enhancing the safety of the battery.

[0083] In some embodiments, with continued reference to FIG. 1, a first electrolytic quality 631 and second electrolyte 632 are separated by a first separator 64, which includes at least one of a sodium ion-substituted perfluorosulfonic acid resin film, a sodium fast ion conductor solid electrolyte, and an oxide solid electrolyte.

[0084] The first separator 64 can keep the first electrolyte 631 and the second electrolyte 632 separated and prevent their interpenetration, which corresponds to forming a dual-cavity battery structure, which realizes the exchange of sodium ions between the first electrolyte 631 and the second electrolyte 632, making the chemical reaction reversible and allowing the battery to be repeatedly charged.

[0085] The above technical solution can realize effective isolation of different electrolytes in a sodium secondary battery, and further improve the long-term reliability, cycle stability and storage stability of the battery.

[0086] In some embodiments, the sodium fast ion conductor solid electrolyte is Na 3+x M y M´ 2-y Si 2-z P z O 12wherein M and M' may independently comprise at least one selected from Zr, Ca, Mg, Zn, La, Ti, and Nb, and 0≦x<1, 0≦y<2, and 0≦z<2.

[0087] In some embodiments, x is optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.

[0088] In some embodiments, y is optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9.

[0089] In some embodiments, z is optionally 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9.

[0090] In some embodiments, the sodium fast ion conductor solid electrolyte is Na 3.4 Zr 1.9 Zn 0.1 Si 2.2 P 0.8 O 12 , Na3Zr 1.75 Mg 0.25 SiPO 12 , Na 3.3 Zr 1.7 La 0.3 SiPO 12 , Na 3.1 Ca 0.05 Zr 1.95 SiPO 12 It includes at least one of the following.

[0091] In some embodiments, the oxide solid electrolyte includes at least one of Na-β-AlO and Na-β″-AlO, wherein the Na-β-AlO includes β-NaO·11AlO, and the Na-β″-AlO includes β″-NaO·5AlO.

[0092] In some embodiments, the sodium secondary battery includes at least two layers of a second separator, the first electrolyte and the second electrolyte being respectively infiltrated onto different layers of the second separator, and the second separator includes at least one of a polyethylene film, a polypropylene film, or a glass fiber film.

[0093] Polyethylene film, polypropylene film, or glass fiber film are commonly used separators for secondary batteries, and because they allow solvents to permeate through them, a separator including at least two layers is installed in a sodium secondary battery, and different electrolytes and different layers of the separator are allowed to permeate each other, thereby reducing interpenetration between the first electrolyte and the second electrolyte.

[0094] In some embodiments, a first electrolyte is wetted onto a polyethylene film and a second electrolyte is wetted onto a glass fiber film. In some embodiments, a first electrolyte is wetted onto a polypropylene film and a second electrolyte is wetted onto a glass fiber film. In some embodiments, a first electrolyte is wetted onto a glass fiber film and a second electrolyte is wetted onto a polypropylene film.

[0095] The above technical solution is low cost, applicable to conventional battery production technology, and suitable for large-scale popular use.

[0096] In some embodiments, the added volume V per unit volume of the first electrolyte and the second electrolyte is 3 μL / mAh, respectively. <V<10μL / mAhである。

[0097] As used herein, the term "added volume per unit capacity, V" is calculated by dividing the added volume of the first electrolyte or second electrolyte by the capacity of the corresponding battery.

[0098] The capacity of the battery in question is obtained by testing a battery having the same load and the same type of positive electrode active material and negative electrode active material at a constant capacity.

[0099] In some embodiments, the added volume V per unit volume of the first electrolyte and the second electrolyte is optionally 3 μL / mAh, 4 μL / mAh, 5 μL / mAh, 6 μL / mAh, 7 μL / mAh, 8 μL / mAh, 9 μL / mAh, or 10 μL / mAh.

[0100] By ensuring that the volume V of the first and second electrolytes added per unit volume falls within the lean electrolyte range, almost all of the electrolyte is adsorbed onto the second separator, reducing the amount of free-flowing electrolyte, thereby preventing interpenetration between the first and second electrolytes. Adding small amounts of the first and second electrolytes in drops provides isolation between the two, widening the electrochemical window of the battery, improving cycle stability, reducing gas generation, and enhancing battery safety.

[0101] In some embodiments, the viscosity of the first electrolyte and the viscosity of the second electrolyte are both greater than 500 mPa·s, and optionally greater than 1000 mPa·s. In some embodiments, the viscosity of the first electrolyte is optionally 501 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 1000 mPa·s, 1001 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, or 4000 mPa·s. 、4500mPa s, 5000mPa s, 6000mPa s, 7000mPa s, 8000mPa s, 9000mPa s, 10000mPa s, 20000mPa ·s, 30000mPa·s, 40000mPa·s, 50000mPa·s, 60000mPa·s, 70000mPa·s, 80000mPa·s, 90000mPa·s or 100,000 mPa·s, and the viscosity of the second electrolyte is optionally 501 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 1000 mPa·s, 1001 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s. 、4 500mPa·s, 5000mPa·s, 6000mPa·s, 7000mPa·s, 8000mPa·s, 9000mPa·s, 10000mPa·s, 20000mPa·s, 30000mPa·s, 40000mPa·s, 50000mPa·s, 60000mPa·s, 70000mPa·s, 80000mPa·s, 90000mPa·s or 100000mPa·s.

[0102] Both the first electrolyte and the second electrolyte have high viscosity and low fluidity, so that they form a clear phase interface, making it difficult for mutual infiltration to occur, and enabling phase separation to be achieved.

[0103] In some embodiments, the first electrolyte and the second electrolyte both comprise a polymer.

[0104] The introduction of a polymer into both the first and second electrolytes effectively reduces the fluidity between the first and second electrolytes, realizing the separation between the first and second electrolytes while weakening the solvation effect of sodium ions, further reducing the gas generation rate, and improving the storage performance and safety of the battery.

[0105] In some embodiments, both the first electrolyte and the second electrolyte comprise a sodium salt, and the mass content of the sodium salt in the first electrolyte is 2% to 70%, and optionally 15% to 20%, based on the total mass of the first electrolyte, and the mass content of the sodium salt in the second electrolyte is 2% to 70%, and optionally 15% to 20%, based on the total mass of the second electrolyte.

[0106] In some embodiments, the mass content of the sodium salt in each of the first electrolyte and the second electrolyte is optionally 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70% based on the total mass of the first electrolyte and the second electrolyte, respectively.

[0107] The mass content of the sodium salt in each of the first and second electrolytes is controlled to 2% to 70%, based on the total mass of the first and second electrolytes, respectively, thereby broadening the application field of sodium secondary batteries. The mass content of the sodium salt in each of the first and second electrolytes is controlled to 15% to 20%, based on the total mass of the first and second electrolytes, respectively, thereby further widening the electrochemical window of the battery, improving the cycle stability of the battery, reducing the gas generation rate of the battery, and improving the safety of the battery.

[0108] In some embodiments, the sodium salts include one or more of sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium tetrafluoroyttriate, sodium hexafluoroarsenate, sodium acetate, sodium trifluoroacetate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium (n-perfluorobutylsulfonyl)imide, optionally one or more of sodium hexafluorophosphate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, optionally one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

[0109] In some embodiments, the first electrolyte comprises sodium perchlorate and the second electrolyte comprises sodium perchlorate. In some embodiments, the first electrolyte comprises sodium perchlorate and the second electrolyte comprises sodium hexafluorophosphate. In some embodiments, the first electrolyte comprises sodium hexafluorophosphate and the second electrolyte comprises sodium perchlorate. In some embodiments, the first electrolyte comprises sodium perchlorate and the second electrolyte comprises sodium bis(fluorosulfonyl)imide. In some embodiments, the first electrolyte comprises sodium hexafluorophosphate and the second electrolyte comprises sodium bis(trifluoromethanesulfonyl)imide. All of the above sodium salts are advantageous in widening the electrochemical window of the battery, improving the storage performance of the battery, reducing the gassing rate of the battery, and improving the safety of the battery.

[0110] In some embodiments, the first electrolyte and the second electrolyte both comprise a sodium salt and an organic solvent, the sodium salt of the first electrolyte comprises one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide, the organic solvent of the first electrolyte comprises one of an ester-based solvent, a sulfone-based solvent, and a fluoroether-based solvent, and the second electrolyte comprises sodium hexafluorophosphate and the second electrolyte comprises an ether-based solvent.

[0111] In some embodiments, the first electrolyte and the second electrolyte both comprise a sodium salt and an organic solvent, the sodium salt of the first electrolyte comprising one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium perchlorate, the organic solvent of the first electrolyte comprising one or more of ethyl methyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane, and dimethyl sulfoxide, the sodium salt of the second electrolyte comprising one or more of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide, and the organic solvent of the second electrolyte comprising one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and 15-crown ether-5.

[0112] In some embodiments, the first electrolyte and / or the second electrolyte comprises a polymer, and the mass content of the polymer in the first electrolyte is 2% to 30%, and optionally 10% to 20%, based on the total mass of the first electrolyte, and the mass content of the polymer in the second electrolyte is 2% to 30%, and optionally 10% to 20%, based on the total mass of the second electrolyte.

[0113] In some embodiments, the first electrolyte comprises a polymer, and the mass content of the polymer in the first electrolyte is optionally 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 27%, or 30%, based on the total mass of the first electrolyte.

[0114] In some embodiments, the second electrolyte comprises a polymer, and the mass content of the polymer in the second electrolyte is optionally 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 27%, or 30%, based on the total mass of the second electrolyte.

[0115] Controlling the polymer mass content in each of the first electrolyte and the second electrolyte to 2% to 30% based on the total mass of the first electrolyte and the second electrolyte respectively is advantageous for widening the electrochemical window of the battery, improving the cycle performance and storage performance of the battery, reducing the gas generation rate of the battery, and enhancing the safety of the battery.

[0116] By controlling the polymer mass content in each of the first electrolyte and the second electrolyte to 10% to 20% based on the total mass of the first electrolyte and the second electrolyte, respectively, the electrochemical window of the battery can be further widened, the cycle performance and storage performance of the battery can be improved, and the gas generation rate of the battery can be reduced, which is advantageous for further improving the safety of the battery.

[0117] In some embodiments, the polymer comprises one or more of polyethylene oxide, polyethylene glycol, polyvinylpyrrolidone, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyvinyl chloride, polyacrylamide, polytrimethylene carbonate, and perfluoropolyether.

[0118] In some embodiments, the polymer comprises polyethylene oxide. In some embodiments, the polymer comprises polyvinylpyrrolidone. In some embodiments, the polymer comprises polyvinylidene fluoride. In some embodiments, the polymer comprises polyethylene oxide and a perfluoropolyether. In some embodiments, the polymer comprises polyethylene oxide and polyvinylpyrrolidone.

[0119] All of the above polymers are advantageous in widening the electrochemical window of the battery, improving the cycle performance and storage performance of the battery, and reducing the gas generation rate of the battery, thereby improving the safety of the battery.

[0120] In some embodiments, the first electrolyte and the second electrolyte both comprise a sodium salt, an organic solvent, and a polymer, the sodium salt of the first electrolyte comprising one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium perchlorate, the organic solvent of the first electrolyte comprising one or more of ethyl methyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane, and dimethyl sulfoxide, and the polymer of the first electrolyte comprises a sodium salt, an organic solvent, and a polymer. includes one or more of polyvinylidene fluoride, polyethylene oxide, and perfluoropolyether; the sodium salt of the second electrolyte includes one or more of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; the organic solvent of the second electrolyte includes one or more of ethyl methyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and N,N-dimethylacetamide; and the polymer of the second electrolyte includes one or more of polyvinylpyrrolidone and polyethylene oxide.

[0121] In some embodiments, the sodium secondary battery is a sodium metal battery.

[0122] A sodium metal battery has a sodium metal phase pre-deposited on a negative electrode current collector as a negative electrode, and has a higher theoretical capacity and energy density than conventional negative electrode materials because of the sodium metal phase as a negative electrode.

[0123] In some embodiments, the sodium secondary battery is a negative electrode-less sodium secondary battery.

[0124] Anode-less sodium secondary batteries contain only anode current collectors without any pre-deposited anode active material. During initial charging, sodium ions gain electrons on the anode side, and metallic sodium accumulates on the current collector surface, forming a sodium metal phase. During discharge, metallic sodium is converted back to sodium ions and returns to the cathode, enabling cycle charging and discharging. Compared with other sodium secondary batteries and sodium metal batteries, anode-less sodium secondary batteries are not limited by the anode material, allowing for higher energy density. Furthermore, anode-less sodium secondary batteries have high cycle performance and high molding efficiency, effectively reducing battery manufacturing costs and cycle times.

[0125] In some embodiments, the CB value of the negative electrode-less sodium secondary battery is 0.1 or less.

[0126] The CB value is calculated by dividing the capacity per unit area of ​​the negative electrode plate in a secondary battery by the capacity per unit area of ​​the positive electrode plate. Because a negative electrode-less battery does not contain a negative electrode active material, the capacity per unit area of ​​the negative electrode plate is relatively small, and the CB value of the secondary battery is 0.1 or less.

[0127] In some embodiments, referring to FIG. 3 , 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. A non-Newtonian fluid electrolyte composition is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select the number according to specific needs.

[0128] [Positive electrode plate] In some embodiments, the positive electrode plate includes an active positive electrode material, the active positive electrode material including at least one of a transition metal layered oxide, a polyanionic compound, and a Prussian blue compound, and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na(Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 )O2, Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 O2, Na4Fe3(PO4)2P2O7, NaFePO4, Na3V2(PO4)3, Na 1.9 It includes one or more of CoFe(CN)6, Na2NiFe(CN)6, and NaMnFe(CN)6.

[0129] In some embodiments, 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. Alternatively, 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。

[0130] In some embodiments, the polyanionic compound comprises a metal ion, a transition metal ion, and a 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

[0131] In some embodiments, the Prussian blue-based 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-based 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。

[0132] All of the above positive electrode active materials are advantageous in widening the electrochemical window of the battery, improving the storage performance of the battery, reducing the gas generation rate of the battery, and improving the safety of the battery.

[0133] In some embodiments, the surface of the positive electrode active material has a coating layer, and the coating layer includes one or more of a carbon material, ZrO, TiO, polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride, and the carbon material includes one or more of amorphous carbon, graphite, and graphene.

[0134] As used herein, the term "amorphous carbon" refers to a carbon material that has a very low degree of graphitization crystallization and is close to an amorphous form, and does not have a specific shape or periodic structure discipline. By way of example, amorphous carbon includes, but is not limited to, carbon black, charcoal, or coke.

[0135] As used herein, the term "graphite" refers to an allotrope of carbon and includes natural and artificial graphite.

[0136] As used herein, the term "graphene" refers to sp 2 Graphene is a carbon material in which hybrid-bonded carbon atoms are densely packed into a single layer of a two-dimensional cellular lattice structure. By way of example, graphene includes, but is not limited to, single-layer graphene and multi-layer graphene.

[0137] As used herein, the term "single-layer graphene" refers to a single-layer structure consisting of carbon atoms densely packed periodically in a hexagonal honeycomb structure. By way of example, the thickness of single-layer graphene is only 0.3 nm to 0.4 nm.

[0138] As used herein, the term "multilayer graphene" refers to a graphene produced by stacking 2 to 10 single-layer graphene layers together, with a total thickness of less than 100 nm.

[0139] The coating layer contains a positive electrode active material, which is advantageous for improving the cycle performance and storage performance of the battery.

[0140] In some embodiments, the thickness of the coating layer is between 2 nm and 1000 nm, optionally between 10 nm and 100 nm.

[0141] In some embodiments, the thickness of the coating layer is optionally 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm.

[0142] Controlling the thickness of the coating layer within an appropriate range is advantageous for improving the high voltage cycle stability and electrical performance of the battery.

[0143] The positive electrode plate 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.

[0144] The positive electrode plate 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).

[0145] The positive electrode plate further includes a positive electrode current collector, which may be a conductive carbon piece, a metal foil, a 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 coated metal foil, and the porous metal plate are each independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector may be a composite current collector formed by combining a metal foil with a polymer base film.

[0146] 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.

[0147] [Negative electrode plate] In some embodiments, the negative electrode plate includes a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, the undercoating including one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.

[0148] The undercoating not only has excellent electrical conductivity but also favors uniform deposition of metal ions on the surface of the current collector, improving the cycle performance and safety of the battery.

[0149] In some embodiments, the negative electrode plate may include only a negative electrode current collector with an undercoating and no negative electrode active material. The negative electrode plate may also include a pre-deposited metallic phase on a negative electrode current collector with an undercoating.

[0150] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, the metal foil sheet may be aluminum foil or copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0151] In some embodiments, the areal density of the undercoating is 5 g / m 2 ~50g / m 2 is.

[0152] Surface density is 5g / m 2 ~50g / m 2 The undercoating favors a uniform distribution of nucleation sites, promotes uniform deposition of the metal, and does not affect the electron transport behavior.

[0153] In some embodiments, the undercoating has a thickness of between 2 μm and 100 μm.

[0154] The thickness of the undercoating can be controlled to be 2 μm to 100 μm, which can provide sufficient nucleation sites, favor the uniform deposition of metal ions, and suppress dendrites.

[0155] In some embodiments, the positive and negative electrodes and the separator can be fabricated into an electrode assembly by a winding or lamination process.

[0156] In some embodiments, the sodium secondary battery may include an outer casing, which may be used to package the electrode assembly and electrolyte.

[0157] 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.

[0158] 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. 2 shows an example of a sodium secondary battery 5 having a rectangular structure.

[0159] In some embodiments, referring to FIG. 3 , 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. A non-Newtonian fluid electrolyte composition is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select the number according to specific needs.

[0160] [Battery module] 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.

[0161] Fig. 4 shows an example of a battery module 4. Referring to Fig. 4, 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.

[0162] 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.

[0163] [Battery pack] 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.

[0164] 5 and 6 show an example of a battery pack 1. Referring to FIGS. 5 and 6, 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.

[0165] [Power consumption equipment] In one embodiment of the present application, a power consuming device is provided, which includes at least one of the sodium secondary battery of any of the embodiments, the battery module of any of the embodiments, or the battery pack of any of the embodiments.

[0166] The power consuming device includes 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 and satellites, energy storage systems, etc.

[0167] As the power consuming device, a sodium secondary battery, a battery module, or a battery pack can be selected depending on the usage demand.

[0168] 7 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. This power consuming device can employ a battery pack or a battery module to meet the demand for high power output and high energy density of sodium secondary batteries.

[0169] 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.

[0170] Example The following examples of the present application are described. 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. In the examples, unless specific techniques or conditions are shown, the techniques or conditions are performed according to the techniques or conditions described in the literature in the field or according to the product specifications. The reagents or instruments used do not indicate their manufacturers, and are all ordinary products that are commercially available.

[0171] 1. Manufacturing method Example 1 1) Electrolyte production In a dry argon gas atmosphere, the solvents ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1, and sodium perchlorate (NaClO4) was added. The mixture was stirred uniformly to completely dissolve the sodium perchlorate, yielding a first electrolyte. The concentration of sodium perchlorate was 1 mol / L based on the total volume of the first electrolyte.

[0172] In a dry argon gas atmosphere, sodium hexafluorophosphate and the solvent ethylene glycol dimethyl ether (DME) were uniformly stirred and mixed to completely dissolve the sodium hexafluorophosphate, yielding a second electrolyte. The concentration of sodium hexafluorophosphate was 1 mol / L based on the total volume of the second electrolyte.

[0173] The mass ratio of the first electrolyte to the second electrolyte is 1:1.

[0174] 2) Manufacturing of positive electrode plates 2.5 wt% polyvinylidene fluoride adhesive was thoroughly dissolved in N-methylpyrrolidone (NMP), and then 2.0 wt% Super P, 1.0 wt% carbon nanotubes, and 94.5 wt% Na4Fe3(PO4)2P2O7 positive electrode active material were added and stirred to obtain a positive electrode slurry. The slurry was evenly applied to the surface of an aluminum foil current collector and then transferred to a vacuum oven for complete drying. The dried electrode plate was roll pressed and punched to obtain a positive electrode plate.

[0175] 3) Manufacturing of negative electrode plates Carbon nanotubes and carboxymethyl cellulose (CMC) were added to deionized water in a mass ratio of 1:0.4 and stirred to form a uniform slurry. The slurry was then applied to the surface of the negative electrode current collector copper foil to form an undercoating, which was then transferred to a vacuum oven to dry completely and then punched out. The thickness of the undercoating was 20 μm and the surface density was 25 g / m. 2 Thus, a negative electrode plate with no negative electrode structure was obtained.

[0176] 4) Separator Sodium fast ion conductor Na 3.4 Zr 1.9 Zn 0.1 Si 2.2 P 0.8 O 12 was used as the separator.

[0177] 5) Battery manufacturing The positive electrode plate, negative electrode plate, and separator were assembled into a dual-cavity battery. A first electrolyte was added to the cavity between the positive electrode plate and the separator, and a second electrolyte was added to the cavity between the negative electrode plate and the separator to obtain an uncharged battery. The uncharged battery was then subjected to steps such as standing, chemical formation, and capacity testing to obtain the uncharged sodium secondary battery of Example 1.

[0178] Examples 2 to 15 In Examples 2 to 15, dual-cavity batteries were still used, but the types and compositions of materials were different, and the other manufacturing methods were basically the same as in Example 1. The thickness of the coating layer of the positive electrode active material in Examples 8, 10, and 15 was 30 nm, and the specific materials were as shown in Tables 1 and 2.

[0179] Example 16 1) Electrolyte production In a dry argon gas atmosphere, sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and a solvent, dimethyl sulfoxide (DMSO), were uniformly mixed and stirred until the sodium bis(trifluoromethanesulfonyl)imide was completely dissolved, yielding a first electrolyte. The concentration of sodium bis(trifluoromethanesulfonyl)imide was 1 mol / L based on the total volume of the first electrolyte.

[0180] In a dry argon gas atmosphere, sodium hexafluorophosphate (NaPF6) and the solvent diethylene glycol dimethyl ether (G2) were uniformly stirred and mixed to completely dissolve the sodium hexafluorophosphate, yielding a second electrolyte. The concentration of sodium hexafluorophosphate was 1 mol / L based on the total volume of the second electrolyte.

[0181] The mass ratio of the first electrolyte to the second electrolyte is 1:1.

[0182] 2) Manufacturing of positive electrode plates 2.5 wt% polyvinylidene fluoride adhesive was thoroughly dissolved in N-methylpyrrolidone (NMP), and then 2.0 wt% Super P, 1.0 wt% carbon nanotubes, and 94.5 wt% Na4Fe3(PO4)2P2O7 positive electrode active material were added and stirred to obtain a positive electrode slurry. The slurry was evenly applied to the surface of an aluminum foil current collector and then transferred to a vacuum oven for complete drying. The dried electrode plate was roll pressed and punched to obtain a positive electrode plate.

[0183] 3) Manufacturing of negative electrode plates Carbon nanotubes and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 1:0.4 with deionized water and stirred to form a uniform slurry. The slurry was then coated onto the surface of a negative electrode current collector copper foil, which was then transferred to a vacuum oven to completely dry. The undercoating was then punched out to obtain a negative electrode plate with a no-anode structure. The thickness of the undercoating was 20 μm, and the areal density was 25 g / m. 2 is.

[0184] 4) Separator Polyethylene film and glass fiber film 5) Battery manufacturing A positive electrode plate, polyethylene film, glass fiber film, and negative electrode plate were stacked in this order and wound to obtain a bare cell. A tab was welded to the bare cell, and the bare cell was placed in an aluminum case and baked at 80°C to remove moisture. Then, 4 μL / mAh of the first electrolyte was dispensed onto the polyethylene film, and 6 μL / mAh of the second electrolyte was dispensed onto the glass fiber, and the case was sealed to obtain an uncharged battery. The uncharged battery was then subjected to subsequent processes such as standing, hot / cold pressing, chemical conversion, shaping, and capacity testing to obtain the uncharged sodium secondary battery of Example 16.

[0185] Examples 17 to 19 Examples 17 to 19 are similar to the manufacturing method of Example 16, and the thickness of the coating layer of the positive electrode active material in Example 19 is 30 nm. The specific materials are as shown in Tables 1 and 2.

[0186] Example 20 1) Electrolyte production In a dry argon gas atmosphere, sodium hexafluorophosphate, the solvent ethyl methyl carbonate (EMC), and polyvinylidene fluoride polymer were uniformly stirred and mixed until the sodium hexafluorophosphate was completely dissolved, yielding a first electrolyte. Based on the total volume of the first electrolyte, the concentration of sodium hexafluorophosphate was 1 mol / L. Based on the total mass of the first electrolyte, the mass content of polyvinylidene fluoride was 10%. The viscosity of the first electrolyte was 906 mPa·s.

[0187] In a dry argon gas atmosphere, sodium hexafluorophosphate, the solvent ethylene glycol dimethyl ether (DME), and polyethylene oxide polymer were mixed and stirred uniformly until the sodium hexafluorophosphate was completely dissolved, yielding a second electrolyte. Based on the total volume of the second electrolyte, the concentration of sodium hexafluorophosphate was 1 mol / L. Based on the total mass of the second electrolyte, the mass content of polyethylene oxide was 20%. The viscosity of the second electrolyte was 538 mPa·s.

[0188] 2) Manufacturing of positive electrode plates 2.5 wt% polyvinylidene fluoride adhesive was thoroughly dissolved in N-methylpyrrolidone (NMP), and then 2.0 wt% Super P, 1.0 wt% carbon nanotubes, and 94.5 wt% Na4Fe3(PO4)2P2O7 positive electrode active material were added and stirred to obtain a positive electrode slurry. The slurry was evenly applied to the surface of an aluminum foil current collector and then transferred to a vacuum oven for complete drying. The dried electrode plate was roll pressed and punched to obtain a positive electrode plate.

[0189] 3) Manufacturing of negative electrode plates Carbon nanotubes and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 1:0.4 with deionized water and stirred to form a uniform slurry. The slurry was then coated onto the surface of a negative electrode current collector copper foil, which was then transferred to a vacuum oven to completely dry. The undercoating was then punched out to obtain a negative electrode plate with a no-anode structure. The thickness of the undercoating was 20 μm, and the areal density was 25 g / m. 2 is.

[0190] 4) Separator Polyethylene film 5) Battery manufacturing The first electrolyte and the second electrolyte were cast on both sides of the separator, and then the positive electrode plate, the first electrolyte, the separator, the second electrolyte, and the negative electrode plate were stacked in this order. The separator coated with the electrolyte was placed between the positive and negative electrodes to provide isolation, and then wound up to obtain a bare cell. Tabs were welded to the bare cell, and the bare cell was placed in an aluminum case and baked at 80°C to remove moisture, resulting in an uncharged battery. The uncharged battery was then subjected to the following processes in order: standing, hot and cold pressing, chemical formation, shaping, capacity testing, etc., and the battery was then tested in the following examples. 20 A negative electrode-free sodium secondary battery was obtained.

[0191] Examples 21-22 Examples 21 and 22 are similar to the manufacturing method of Example 20, but the type of positive electrode active material is adjusted. Here, the thickness of the coating layer of the positive electrode active material in Example 22 is 30 nm, and the specific materials are as shown in Tables 1 and 2.

[0192] Example 23 1) Electrolyte production In a dry argon gas atmosphere, sodium hexafluorophosphate, the solvent 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane (F3DEE), polyvinylidene fluoride polymer, and perfluoropolyether polymer were uniformly stirred and mixed until the sodium hexafluorophosphate was completely dissolved, yielding a first electrolyte. Based on the total volume of the first electrolyte, the concentration of sodium hexafluorophosphate was 1 mol / L. Based on the total mass of the first electrolyte, the mass content of polyvinylidene fluoride was 10%, and the mass content of perfluoropolyether was 10%. The viscosity of the first electrolyte was 1087 mPa·s.

[0193] In a dry argon gas atmosphere, sodium hexafluorophosphate, the solvent N,N-dimethylacetamide (DMA), and polyvinylpyrrolidone polymer were mixed and stirred uniformly until the sodium hexafluorophosphate was completely dissolved, yielding a second electrolyte. Based on the total volume of the second electrolyte, the concentration of sodium hexafluorophosphate was 1 mol / L. Based on the total mass of the second electrolyte, the mass content of polyethylene oxide was 10%. The viscosity of the first electrolyte was 675 mPa·s.

[0194] 2) Manufacturing of positive electrode plates 2.5 wt% polyvinylidene fluoride adhesive was thoroughly dissolved in N-methylpyrrolidone (NMP), and then 2.0 wt% Super P, 1.0 wt% carbon nanotubes, and 94.5 wt% Na4Fe3(PO4)2P2O7 positive electrode active material were added and stirred to obtain a positive electrode slurry. The slurry was evenly applied to the surface of an aluminum foil current collector and then transferred to a vacuum oven for complete drying. The dried electrode plate was roll pressed and punched to obtain a positive electrode plate.

[0195] 3) Manufacturing of negative electrode plates Carbon nanotubes and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 1:0.4 with deionized water and stirred to form a uniform slurry. The slurry was then coated onto the surface of a negative electrode current collector copper foil, which was then transferred to a vacuum oven to completely dry. The undercoating was then punched out to obtain a negative electrode plate with a no-anode structure. The thickness of the undercoating was 20 μm, and the areal density was 25 g / m. 2 is.

[0196] 4) Separator Polyethylene film 5) Battery manufacturing The first electrolyte and the second electrolyte were cast onto both sides of the separator, and the positive electrode plate, the first electrolyte, the separator, the second electrolyte, and the negative electrode plate were stacked in this order. The electrolyte-coated separator was positioned between the positive and negative electrodes to provide isolation, and then wound up to obtain a bare cell. Tabs were welded to the bare cell, which was then placed in an aluminum case and baked at 80°C to remove moisture, resulting in an uncharged battery. The uncharged battery was then subjected to subsequent processes such as standing, hot and cold pressing, chemical formation, shaping, and capacity testing to obtain the uncharged sodium secondary battery of Example 1.

[0197] Examples 24-25 Examples 24 to 25 are similar to the manufacturing method of Example 23, but the type of positive electrode active material is adjusted. Here, the thickness of the coating layer of the positive electrode active material in Example 25 is 30 nm, and the specific materials are as shown in Tables 1 and 2.

[0198] Comparative Example 1 1) Electrolyte production In a dry argon gas atmosphere, the solvents ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) are mixed in a volume ratio of 1:1:1, sodium perchlorate (NaClO4) is added, and the mixture is stirred evenly to completely dissolve the sodium perchlorate. The concentration of sodium perchlorate is 1 mol / L based on the total volume of the electrolyte.

[0199] 2) Manufacturing of positive electrode plates 2.5 wt% polyvinylidene fluoride adhesive was thoroughly dissolved in N-methylpyrrolidone (NMP), and then 2.0 wt% Super P, 1.0 wt% carbon nanotubes, and 94.5 wt% Na4Fe3(PO4)2P2O7 positive electrode active material were added and stirred to obtain a positive electrode slurry. The slurry was evenly applied to the surface of an aluminum foil current collector and then transferred to a vacuum oven for complete drying. The dried electrode plate was roll pressed and punched to obtain a positive electrode plate.

[0200] 3) Manufacturing of negative electrode plates Carbon nanotubes and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 1:0.4 with deionized water and stirred to form a uniform slurry. The slurry was then coated onto the surface of a negative electrode current collector copper foil, which was then transferred to a vacuum oven to completely dry. The undercoating was then punched out to obtain a negative electrode plate with a no-anode structure. The thickness of the undercoating was 20 μm, and the areal density was 25 g / m. 2 is.

[0201] 4) Separator Polyethylene film 5) Battery manufacturing A positive electrode plate, polyethylene film, and negative electrode plate were stacked in this order and wound up to obtain a bare cell. A tab was welded to the bare cell, which was then placed in an aluminum case and baked at 80°C to remove moisture. An electrolyte was then poured into the case and sealed to obtain an uncharged battery. The uncharged battery was then subjected to further processes, such as standing, hot / cold pressing, chemical formation, shaping, and capacity testing, to obtain a non-negative electrode sodium secondary battery of Comparative Example 1.

[0202] Comparative Examples 2 to 15 The manufacturing methods of Comparative Examples 2 to 15 were basically the same as that of Comparative Example 1, and the specific materials were as shown in Tables 1 and 2.

[0203] 2. Performance test 1. Test of the added volume per unit volume of the first electrolyte and the second electrolyte It is calculated by dividing the volume of the first electrolyte or the second electrolyte added by the capacity of the corresponding battery.

[0204] The capacity of the corresponding battery is obtained by measuring the capacity of a battery having the same load and the same type of positive electrode active material and negative electrode active material as the corresponding example.

[0205] 2. Battery performance test 1) Coulomb efficiency test The coulombic efficiency test process is as follows: At 25°C, the fabricated battery is charged at a constant current of 0.1 C to 3.7 V (sodium iron pyrophosphate positive electrode) or 4.0 V (layered oxide positive electrode) to obtain the initial charge capacity (Cc1), and then discharged at a constant current of 0.1 C to 2.5 V to obtain the initial discharge capacity (Cd1). After performing n charge and discharge cycles, the number of cycles (n) at which the capacity is reduced to 80% is recorded, and the average coulombic efficiency of the battery is calculated according to the following formula: Coulomb efficiency at the first cycle = initial discharge capacity (Cd1) / initial charge capacity (Cc1) × 100% The Coulomb efficiency at the nth cycle is calculated as follows: nth discharge capacity (Cdn) / nth charge capacity (Ccn) × 100%. The average value of the coulombic efficiencies from the second cycle to the nth cycle was taken as the average coulombic efficiency of the battery.

[0206] The test procedures for the comparative example and other examples were the same as those described above.

[0207] 2) Cycle performance test The cycle performance test process is as follows: At 25°C, the fabricated battery was charged to 3.7 V (sodium iron pyrophosphate cathode) or 4.0 V (layered oxide cathode) at a constant current of 1 C, and then discharged to 2.5 V at 1 C. The resulting capacity was designated as the initial capacity (C0). The above steps were repeated for the same battery, and the discharge capacity (Cn) of the battery after n cycles was recorded. The battery capacity retention rate after each cycle was calculated as Pn = Cn / C0 × 100%, and the number of cycles of the battery was recorded when Pn decreased to 80%. The test process for the comparative example and other examples was the same as above.

[0208] 3) Electrochemical window test The electrochemical window test process is as follows: An electrochemical workstation was used to perform the electrolyte window test, with the test temperature at 25°C, the voltage range at 1.0-5.2V, and the scan rate at 0.1mV / s. The usable window of the electrolyte was determined based on the onset of the peak potential in the CV curve. All cyclic voltammetry (CV) tests in this experiment were completed on a Solartron 1470 multi-channel electrochemical workstation in the UK. The test process for the comparative example and other examples was the same as above.

[0209] 4) Cycle gas generation performance test After leaving the fabricated full cell at 25°C for 4 hours, the battery was charged at a constant current of 0.1C up to 4 / 3.7V, then charged at a constant voltage of 4 / 3.7V up to 0.01C, left to rest for 5 minutes, and the thickness of the full cell was measured. After storing at 25°C for 60 days, the thickness of the full cell was measured and the thickness expansion rate of the battery was calculated using the following formula: Thickness expansion rate of full cell = [(thickness after storage - thickness before storage) / thickness before storage] × 100%. The 25°C storage expansion rate of " / " indicates that the dual-cavity battery has a rigid structure and the thickness expansion rate of the full cell cannot be measured. The test process for the comparative example and other examples was the same as above.

[0210] 5) Room temperature / high temperature storage performance After leaving the manufactured full cell at 25°C for 4 hours, the battery was charged at a constant current of 0.1C up to 4 / 3.7V, and then at a constant voltage of 4 / 3.7V until the current dropped to 0.01C. Through these steps, the battery was charged to 100% SOC, and the battery was stored in a constant temperature environment of 25 / 60°C. The number of days of storage when the battery's storage capacity retention rate was 80% was recorded.

[0211] 3. Analysis of the test results of each example and comparative example According to the above method, the batteries of the examples and comparative examples were manufactured, and the performance parameters were measured. The results are shown in Tables 1, 2 and 3 below.

[0212] [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5] [Table 1-6] Note: " / " in Table 1 indicates that the substance is not contained and the mass content of the substance is the same.

[0213] [Table 2-1] [Table 2-2]

[0214] [Table 3-1] [Table 3-2] Note: The " / " in Table 3 indicates that the dual-cavity battery is a rigid structure battery and the thickness expansion rate of the full cell cannot be tested.

[0215] As can be seen from the above results, the sodium secondary batteries of Examples 1 to 25 all comprised a positive electrode plate, a negative electrode plate, a first electrolyte located on the positive electrode plate side, and a second electrolyte located on the negative electrode plate side, and the first electrolyte and the second electrolyte comprise different organic solvents, the first electrolyte comprising at least one of an ester-based solvent, a sulfone-based solvent, and a fluoroether-based solvent, and the second electrolyte comprising at least one of an ether-based solvent and an amide-based solvent.

[0216] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 4, Example 2 and Comparative Examples 1 and 8, Example 3 and Comparative Examples 7 and 8, Example 4 and Comparative Examples 10 and 11, Example 5 and Comparative Examples 7 and 11, Example 6 and Comparative Example 10, Example 9 and Comparative Examples 2 and 9, Example 10 and Comparative Example 3, Example 11 and Comparative Example 4, Example 12 and Comparative Example 8, Example 13 and Comparative Example 11, Example 14 and Comparative Example 9, Example 16 and Comparative Examples 4 and 12, Example 17 and Comparative Examples 8 and 12, Example 18 and Comparative Examples 5 and 13, Example 19 and Comparative Example 6, Example 20 and Comparative Examples 14 and 15, Example 21 and Comparative Example 16, and Example 23 and Comparative Examples 17 and 18, compared to the sodium secondary battery containing only a single-phase electrolyte in the prior art, the sodium secondary battery containing the first electrolyte and the second electrolyte in the present application maintained high cycle stability and storage stability while also having a wider electrochemical stability window, thereby widening the electrochemical window of the battery and effectively improving its electrochemical stability.

[0217] As can be seen from comparisons between Example 1 and Comparative Examples 1 and 4, Example 2 and Comparative Examples 1 and 8, Example 3 and Comparative Examples 7 and 8, Example 4 and Comparative Examples 10 and 11, Example 5 and Comparative Examples 7 and 11, Example 6 and Comparative Example 10, Example 11 and Comparative Example 4, Example 12 and Comparative Example 8, Example 13 and Comparative Example 11, Example 16 and Comparative Examples 4 and 12, Example 17 and Comparative Examples 8 and 12, Example 20 and Comparative Examples 14 and 15, and Example 23 and Comparative Examples 17 and 18, compared to sodium secondary batteries containing only a single electrolyte, either the first electrolyte or the second electrolyte, for the Na4Fe3(PO4)2P2O7 positive electrode active material, the sodium secondary battery of the present application simultaneously contains the first electrolyte and the second electrolyte, which is advantageous for maintaining the high cycle stability of the battery while increasing the electrochemical stability window width of the battery and widening the electrochemical window of the battery, and is also advantageous for improving the number of storage days at which the storage capacity retention rate of the battery is 80% and improving storage stability.

[0218] Example 9 and Comparative Examples 2 and 9, Example 10 and Comparative Example 3, Example 14 and Comparative Example 9, Example 18 and Comparative Examples 5 and 13, Example 19 and Comparative Example 6, and Example 21 and Comparative Example 16 are compared. 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ]O2 or ZrO2 coated Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 Compared to sodium secondary batteries that contain only a single electrolyte, either the first electrolyte or the second electrolyte, for an O2 positive electrode active material, the sodium secondary battery of the present application simultaneously contains the first electrolyte and the second electrolyte, which is advantageous for maintaining the battery storage stability while increasing the width of the electrochemical stability window of the battery and widening the electrochemical window of the battery, and is also advantageous for improving the coulomb efficiency of the battery and the number of cycles required to achieve an 80% capacity retention rate.

[0219] As can be seen from the comparison between Example 2 and Examples 9-10, Example 5 and Examples 7-8, Example 12 and Examples 14-15, Example 16 and Examples 18-19, Example 20 and Examples 21-22, and Example 23 and Examples 24-25, the positive electrode active material was Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ]O2 or ZrO2 coated Na 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 Compared to the inclusion of O2, the inclusion of Na4Fe3(PO4)2P2O7 in the positive electrode active material is advantageous in improving the number of cycles at which the battery's capacity retention rate remains at 80% and the number of storage days at which the battery's storage capacity retention rate remains at 80%.

[0220] As can be seen from the comparison between Example 10 and Example 9, Example 8 and Example 7, Example 15 and Example 14, Example 19 and Example 18, Example 22 and Example 21, and Example 25 and Example 24, Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 ]O2 cathode active material, Na coated with ZrO2 2 / 3 Ni 1 / 6 Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 The O2 positive electrode active material is advantageous in improving the number of cycles at which the capacity retention rate of the battery is 80% and the number of storage days at which the storage capacity retention rate is 80%.

[0221] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 4, Example 2 and Comparative Examples 1 and 8, Example 3 and Comparative Examples 7 and 8, Example 4 and Comparative Examples 10 and 11, Example 5 and Comparative Examples 7 and 11, Example 6 and Comparative Example 10, Example 9 and Comparative Examples 2 and 9, Example 10 and Comparative Example 3, Example 11 and Comparative Example 4, Example 12 and Comparative Example 8, Example 13 and Comparative Example 11, and Example 14 and Comparative Example 9, the sodium secondary battery in the present application includes a first separator, and the first separator is a mixture of a perfluorosulfonic acid resin film after sodium ion substitution and a Na 3.4 Zr 1.9 Zn0.1 Si 2.2 P 0.8 O 12 and β-Na2O·11Al2O3, which is advantageous in increasing the electrochemical stability window width of the battery, improving the number of storage days at which the storage capacity retention rate of the battery is 80%, and improving storage stability.

[0222] As can be seen from the comparisons between Example 16 and Comparative Examples 4 and 12, Example 17 and Comparative Examples 8 and 12, Example 18 and Comparative Examples 5 and 13, and Example 19 and Comparative Example 6, the sodium secondary battery in the present application includes a two-layer second separator, and the first electrolyte and the second electrolyte are respectively infiltrated onto different second separators, and the second separator includes at least one of a polyethylene film, a polypropylene film, and a glass fiber film, which is advantageous for increasing the electrochemical stability window width of the battery and reducing the storage expansion rate of the battery.

[0223] As can be seen from a comparison between Example 20 and Comparative Examples 14 and 15, Example 21 and Comparative Example 16, and Example 23 and Comparative Examples 17 and 18, compared to conventional sodium secondary batteries that contain only a polymer-containing electrolyte that is the same as the first electrolyte or the second electrolyte, the sodium secondary battery of the present application simultaneously contains a first electrolyte and a second electrolyte, and both the first electrolyte and the second electrolyte contain a polymer, which is advantageous for increasing the electrochemical stability window width of the battery, reducing the storage expansion rate of the battery, and improving the coulombic efficiency of the battery, the number of cycles at which the capacity retention rate is 80%, and the number of storage days at which the storage capacity retention rate is 80%.

[0224] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 4, Example 2 and Comparative Examples 1 and 8, Example 3 and Comparative Examples 7 and 8, Example 4 and Comparative Examples 10 and 11, Example 5 and Comparative Examples 7 and 11, Example 6 and Comparative Example 10, Example 9 and Comparative Examples 2 and 9, Example 10 and Comparative Example 3, Example 11 and Comparative Example 4, Example 12 and Comparative Example 8, Example 13 and Comparative Example 11, Example 14 and Comparative Example 9, Example 16 and Comparative Examples 4 and 12, Example 17 and Comparative Examples 8 and 12, Example 18 and Comparative Examples 5 and 13, Example 19 and Comparative Example 6, Example 20 and Comparative Examples 14 and 15, Example 21 and Comparative Example 16, and Example 23 and Comparative Examples 17 and 18, the sodium salt in the present application includes at least one of sodium perchlorate, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide, and is advantageous in increasing the electrochemical stability window width of the battery.

[0225] As can be seen from comparisons between Example 20 and Comparative Examples 12 and 13, Example 21 and Comparative Example 16, and Example 23 and Comparative Examples 14 and 15, both the first electrolyte and the second electrolyte contain a polymer, and the polymer includes one or more of polyvinylidene fluoride, polyethylene oxide, perfluoropolyether, and polyvinylpyrrolidone, which is advantageous for increasing the electrochemical stability window width of the battery, reducing the storage expansion rate of the battery, and improving the coulombic efficiency of the battery, the number of cycles at which the capacity retention rate reaches 80%, and the number of storage days at which the storage capacity retention rate reaches 80%.

[0226] 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]

[0227] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate, 6 sodium secondary battery, 61 positive electrode plate, 62 negative electrode plate, 631 first electrolyte, 632 second electrolyte, 64 first separator.

Claims

1. A sodium secondary battery comprising: a positive electrode plate; a negative electrode plate; a first electrolyte located on the positive electrode plate side; and a second electrolyte located on the negative electrode plate side, wherein the first electrolyte and the second electrolyte contain different organic solvents, the first electrolyte contains an ester-based solvent, a sulfone-based solvent, or a fluoroether-based solvent, and the second electrolyte contains an ether-based solvent or an amide-based solvent.

2. 2. The sodium secondary battery according to claim 1, wherein there is at least one interface between the first electrolyte and the second electrolyte.

3. 3. The sodium secondary battery according to claim 1, wherein a mass ratio of the first electrolyte to the second electrolyte is 2 / 8 to 8 / 2.

4. 4. The sodium secondary battery according to claim 1, wherein the first electrolyte and the second electrolyte are separated by a first separator, and the first separator includes at least one of a sodium ion-substituted perfluorosulfonic acid resin film, a sodium fast ion conductor solid electrolyte, and an oxide solid electrolyte.

5. The sodium fast ion conductor solid electrolyte is Na ３＋ｘ M ｙ M' ２－ｙ Si ２－ｚ P ｚ O １２ wherein M and M' may independently comprise at least one selected from Zr, Ca, Mg, Zn, La, Ti, and Nb, and 0≦x<1, 0≦y<2, and 0≦z<2; and the oxide solid electrolyte is Na-β-Al ２ O ３ and Na-β″-Al ２ O ３ and wherein the Na-β-Al ２ O ３ is β-Na ２ O.11Al ２ O ３ and the Na-β″-Al ２ O ３ is β″-Na ２ O.5Al ２ O ３ The sodium secondary battery according to claim 4, comprising:

6. 4. The sodium secondary battery according to claim 1, wherein the sodium secondary battery includes at least two layers of a second separator, the first electrolyte and the second electrolyte respectively infiltrating different layers of the second separator, the second separator including at least one of a polyethylene film, a polypropylene film, and a glass fiber film, and the added volumes V per unit capacity of the first electrolyte and the second electrolyte are each in the range of 3 μL / mAh<V<10 μL / mAh.

7. 4. The sodium secondary battery according to claim 1, wherein the viscosity of the first electrolyte and the viscosity of the second electrolyte are both greater than 500 mPa·s, and optionally greater than 1000 mPa·s.

8. The sodium secondary battery according to any one of claims 1 to 7, characterized in that the first electrolyte and the second electrolyte both contain a sodium salt, and the mass content of the sodium salt in each of the first electrolyte and the second electrolyte is 2% to 70%, and optionally 15% to 20%, based on the total mass of the first electrolyte and the second electrolyte.

9. The sodium secondary battery according to claim 8, wherein the sodium salt comprises one or more of sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium tetrafluoroyttriate, sodium hexafluoroarsenate, sodium acetate, sodium trifluoroacetate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetraphenylborate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, and sodium (n-perfluorobutylsulfonyl)imide, and optionally one or more of sodium hexafluorophosphate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide, and optionally one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

10. The sodium secondary battery according to any one of claims 1 to 9, characterized in that the first electrolyte and / or the second electrolyte contains a polymer, and the mass content of the polymer in each of the first electrolyte and the second electrolyte is 2% to 30%, and optionally 10% to 20%, based on the total mass of the first electrolyte and the second electrolyte, respectively.

11. 11. The sodium secondary battery according to claim 10, wherein the polymer includes one or more of polyethylene oxide, polyethylene glycol, polyvinylpyrrolidone, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyvinyl chloride, polyacrylamide, polytrimethylene carbonate, and perfluoropolyether.

12. The ester-based solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, γ-butyrolactone, 1,3-propane sultone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, and ethyl butyrate; The sulfone solvent may include one or more of dimethyl sulfoxide, methyl ethyl sulfone, ethyl isopropyl sulfone, ethyl vinyl sulfone, sulfolane, trifluoromethyl ethyl sulfone, trifluoromethyl propyl sulfone, 1,1,1-trifluoro-3-(methylsulfonyl)propane, 1,1,1-trifluoro-2-(methylsulfonyl)ethane, and 1,1,2,2-tetrafluoro-3-(methylsulfonyl)propane; The fluoroether solvents include 2,2,3,3-tetrafluoro-1,4-dimethoxybutane, 2-(2-ethoxyethoxy)-1,1,1-trifluoroethane, 1,2-bis(2,2-difluoroethoxy)ethane, 2-(2-(2,2-difluoroethoxy)ethoxy)-1,1,1-trifluoroethane, 1,2-bis(2,2,2-trifluoroethoxy)ethane, and 1,1,1,3,3,3-hexafluoroisopropyl. methyl ether, 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, methyl ether 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether, 2,2-bis(trifluoromethyl)-1,3-dioxolane, 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxopentane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxopentane, octafluorotetrahydrofuran; The ether solvent may include one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, diisopropyl ether, dibutyl ether, diethylene glycol dibutyl ether, 1,4-dimethoxybutane, 1,4-diethoxybutane, 1,3-dioxolane, tetrahydrofuran, 15-crown ether-5, 12-crown ether-4, and 18-crown ether-6; The sodium secondary battery according to any one of claims 3 to 11, characterized in that the amide-based solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylacetoacetamide, 1,1,1-trifluorofluoro-N,N-dimethylmethanesulfonamide, N,O-bis(trimethylsilyl)trifluoroacetamide, 2,3,6-trifluorobenzenesulfonamide, N,N-dimethyl 4-fluorobenzenesulfonamide, and N-methyl-N-trimethylsilane trifluoroacetamide.

13. 13. The sodium secondary battery according to claim 1, wherein the sodium secondary battery is a sodium metal battery.

14. 14. The sodium secondary battery according to claim 1, wherein the sodium secondary battery is a non-negative electrode sodium secondary battery.

15. The positive electrode plate includes a positive electrode active material, and the positive electrode active material includes at least one of a transition metal layered oxide, a polyanionic compound, and a Prussian blue compound, and the positive electrode active material includes NaNi １／３ Fe １／３ Mn １／３ O ２ , Na(Cu １／９ Ni ２／９ Fe １／３ Mn １／３ ) O ２ , Na ２／３ Ni １／６ Mn ２／３ Cu １／９ Mg １／１８ O ２ , Na ４ Fe ３ (P.O. ４ ) ２ P ２ O ７ , NaFePO ４ , Na ３ V ２ (P.O. ４ ) ３ , Na １．９ CoFe(CN) ６ , Na ２ NiFe(CN) ６ , NaMnFe(CN) ６ 15. The sodium secondary battery according to claim 1, comprising one or more of:

16. The surface of the positive electrode active material has a coating layer, and the coating layer contains a carbon material, ZrO ２ , TiO ２ , polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene), aluminum oxide, zinc oxide, titanium oxide, zirconium oxide, magnesium oxide, silicon oxide, lanthanum oxide, sodium fluoride, lithium fluoride, and aluminum fluoride, and the carbon material includes one or more of amorphous carbon, graphite, and graphene.

17. 17. The sodium secondary battery according to claim 16, wherein the thickness of the coating layer is 2 nm to 1000 nm, and optionally 10 nm to 100 nm.

18. 18. The sodium secondary battery according to claim 1, wherein the negative electrode plate includes a negative electrode current collector and an undercoating disposed on at least one surface of the negative electrode current collector, and the undercoating includes one or more of carbon nanotubes, graphite, graphene, silver-composite carbon nanoparticles, and tin-composite carbon nanoparticles.

19. The areal density of the undercoating is 5 g / m ２ ~50g / m ２ 19. The sodium secondary battery according to claim 18, wherein

20. 20. The sodium secondary battery according to claim 18, wherein the undercoating has a thickness of 2 μm to 100 μm.

21. A battery module comprising the sodium secondary battery according to any one of claims 1 to 20.

22. A battery pack comprising the sodium secondary battery according to any one of claims 1 to 20 or the battery module according to claim 21.

23. 23. A power consuming device comprising at least one of the sodium secondary battery according to claim 1, the battery module according to claim 21, and the battery pack according to claim 22.

Images