Nonaqueous electrolyte, sodium ion battery containing this electrolyte, and power consumption device

Abstract

The present application provides a nonaqueous electrolyte comprising a first sodium salt including at least one of sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate, and a second sodium salt including one, two, or more of a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group. The nonaqueous electrolyte according to the present application can be applied to a sodium-ion battery, and can improve the room-temperature and high-temperature cycle performance and the capacity retention rate after high-temperature storage of the sodium-ion battery, and can significantly reduce the battery volume expansion rate after high-temperature storage of the sodium-ion battery.

Description

[Technical Field]

[0001] The present application relates to a non-aqueous electrolyte comprising at least two sodium salts, wherein the first sodium salt comprises at least one of sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate, and the second sodium salt comprises one, two, or more of a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group. The present application also relates to a sodium-ion battery and a power-consuming device comprising the non-aqueous electrolyte. [Background technology]

[0002] The utilization of new energy resources is becoming increasingly important in order to achieve the country's "double carbon" strategic goal. Lithium-ion batteries have a relatively high energy density, showing good development prospects in areas such as mobile phones, computers, electric vehicles, and portable electronic devices. However, lithium resources are limited and unevenly distributed around the world. Furthermore, the price of lithium resources (e.g., lithium carbonate) has risen rapidly in recent years. Resource and cost issues limit the large-scale, long-term use of lithium-ion batteries. Therefore, further development of new battery systems with high performance and low cost is of great research significance.

[0003] Compared with lithium resources, sodium resources are more abundant in the Earth's crust, ranking sixth in abundance. Furthermore, sodium resources are relatively uniformly distributed in the Earth's crust and are found all over the world. Therefore, the utilization of sodium resources is not subject to serious limitations in terms of reserves and location. More importantly, sodium resources are relatively low cost and suitable for large-scale, long-term use. Therefore, sodium-ion batteries have greater advantages over lithium-ion batteries in terms of resources and cost. Furthermore, because metallic sodium and lithium have similar physical and chemical properties, sodium-ion batteries can, to some extent, draw on the development experience and reuse the production processes of lithium-ion batteries.

[0004] Sodium ion batteries show relatively good development prospects in the field of electrochemical energy storage, and the industrial development of sodium ion batteries has great strategic significance and economic value. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide a nonaqueous electrolyte that can be applied to a sodium ion battery, and can improve the high-temperature cycle performance and capacity retention rate after high-temperature storage of the sodium ion battery, and can reduce the battery volume expansion rate after high-temperature storage of the sodium ion battery, as well as a sodium ion battery and a power consuming device that include this nonaqueous electrolyte.

[0006] In order to achieve the above object, a first aspect of the present application provides a non-aqueous electrolyte solution, the non-aqueous electrolyte solution comprising: a first sodium salt, the first sodium salt comprising at least one of sodium hexafluorophosphate (NaPF), sodium hexafluoroarsenate (NaAsF), sodium perchlorate (NaClO), and sodium trifluoroacetate (CFCOONa), optionally wherein the first sodium salt is sodium hexafluorophosphate; and a second sodium salt, the second sodium salt including one, two or more of a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group, and optionally the second sodium salt including a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group.

[0007] The non-aqueous electrolyte is prepared by dissolving a sodium salt electrolyte containing electron-rich anions in a non-aqueous solvent. As described above, the selective addition of the first sodium salt and the second sodium salt can control the solvation structure of the sodium ions and the chemical environment of the solvent molecules in the electrolyte, thereby solving the problem of gas generation due to continuous decomposition of the solvent in sodium-ion batteries.

[0008] In any embodiment, the molar concentration ratio of the first sodium salt to the second sodium salt in the nonaqueous electrolyte is 1 / 1 or more, optionally 3 / 1 or more, and 40 / 1 or less, more optionally 15 / 1 or less.

[0009] In the entire electrolyte, the molar concentration ratio of the first sodium salt to the second sodium salt is within the above range, which can reduce the risk of excessive film formation on the electrode surface and reduce the transport resistance of sodium ions at the electrode / electrolyte interface, thereby having a relatively small impact on the dynamic process of the sodium ion battery.

[0010] In any of the embodiments, the sodium salt having a sulfonic acid group is sodium fluorosulfonate (FSO3Na), sodium trifluoromethanesulfonate (NaSO3CF3), sodium bis(fluorosulfonyl)imide (Na[(FSO2)2N]), sodium bis(trifluoromethanesulfonyl)imide (Na[(CF3SO2)2N]), sodium methanesulfonate (CH3SO3Na), sodium vinylsulfonate (C2H3NaO3S), sodium methylsulfonate (CH3OSO3Na), methylthiosulfonate (Methylthiosulfonate), sodium methyl ... Sodium phosphate (CH3NaO2S2), disodium 1,2-ethanedisulfonate (NaO3SCH2CH2SO3Na), sodium ethyl sulfate (C2H5NaO4S), sodium propanesulfonate (C3H7NaO3S), sodium ethylthiosulfonate (C2H5NaO2S2), sodium 2-iodobenzenesulfonate (C6H4INaO3S), sodium 4-nitrobenzenemethanesulfonate (C7H6NNaO5S), sodium styrenesulfonate (C8H7NaO3S), sodium 4-cumenesulfonate (C9H 11 NaO3S), sodium phenolsulfonate (C6H5NaO4S), sodium β-styrenesulfonate (C8H7NaO3S), sodium cyclohexanesulfonate (C6H 11 NaO3S), sodium 2-cyclohexylaminoethanesulfonate (C8H 16 NNaO3S), 4-amino-N-methylbenzenesulfonylamide (CH 10 N2O2S), sodium polydithiodipropane sulfonate (C6H 12 Na2O6S4), sodium pyridine-3-sulfinate (C5H4NNaO2S), piperazine-1,4-diethanesulfonic acid sodium salt (C8H 17 N2NaO6S2), optionally including one or more of sodium fluorosulfonate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium methanesulfonate, and sodium methyl sulfate.

[0011] In any one of the embodiments, the concentration of the sodium salt having a sulfonic acid group in the non-aqueous electrolyte solution is in the range of 0.0005 to 1 mol / L, and optionally in the range of 0.01 to 0.3 mol / L.

[0012] The second sodium salt, in which the concentration of the sulfonic acid group-containing sodium salt in the electrolyte is 0.0005 mol / L or more, can improve the stability of the first sodium salt in the electrolyte, thereby forming a stable solid electrolyte interfacial film on the electrode surface during the electrochemical reaction process in a sodium-ion battery, effectively suppressing decomposition of the electrolyte solvent and gas generation on the electrode surface, and improving the electrochemical performance of the sodium-ion battery (especially at high temperatures). Optionally, the concentration of the sulfonic acid group-containing sodium salt in the electrolyte can be 0.01 mol / L or more. Furthermore, the concentration of the sulfonic acid group-containing sodium salt in the electrolyte can be 0.3 mol / L or less, which can more effectively reduce the risk of excessive film formation on the electrode and does not significantly affect the electrochemical performance of the sodium-ion battery at high temperatures. Optionally, this concentration can be 0.15 mol / L or less.

[0013] In any embodiment, the sodium salt having an oxalic acid group includes one or more of sodium oxalate (NaC0), sodium bis(oxalato)borate (CBNaO), sodium difluoro(oxalato)borate (CBFNaO), sodium tetrafluoro(oxalato)phosphate (CFNaOP), and sodium difluorobis(oxalato)phosphate (CFNaOP).

[0014] In any one of the embodiments, the concentration of the sodium salt having an oxalic acid group in the non-aqueous electrolyte solution is in the range of 0.0005 to 0.1 mol / L, optionally in the range of 0.006 to 0.08 mol / L, and further optionally in the range of 0.01 to 0.02 mol / L.

[0015] The second sodium salt has a concentration of 0.0005 mol / L or more in the electrolyte, which significantly improves the stability of the first sodium salt in the electrolyte and improves the high-temperature cycle performance and capacity retention rate of the sodium-ion battery after storage. Alternatively, this concentration may be 0.006 mol / L or more, and more preferably 0.01 mol / L or more. Preferably, this concentration is 0.08 mol / L or less, which effectively reduces the possibility of excessive film formation on the electrode by the sodium salt having oxalic acid groups and therefore does not significantly affect the kinetics of the charge / discharge cycle of the sodium-ion battery.

[0016] In any embodiment, the sodium salt having a phosphate group is sodium difluorophosphate (NaPOF), sodium monofluorophosphate (NaPOF), sodium trimetaphosphate (NaPO), sodium hexametaphosphate (NaPO 18 ), sodium hydroxyethylidene diphosphonate (C2H7NaO7P2), disodium clodronate (CH2Cl2Na2O6P2), sodium olpadronate (C5H 15 NO7P2), sodium diethylenetriamine pentamethylene phosphonate (C9H 18 N3Na 10 O 15 P5), sodium tripolyphosphate (Na5P3O 10 ) and disodium phenyl phosphate (C6H5Na2O4P), and optionally one or more of sodium difluorophosphate (NaPO2F2) and sodium fluorophosphate (Na2PO3F).

[0017] In any embodiment, the concentration of the sodium salt having a phosphate group in the non-aqueous electrolyte solution is in the range of 0.0005 to 0.12 mol / L, optionally in the range of 0.01 to 0.05 mol / L, and more optionally in the range of 0.01 to 0.03 mol / L.

[0018] The molar concentration of the second sodium salt containing a phosphate group in the non-aqueous electrolyte is 0.0005 mol / L or more, which improves the stability of the first sodium salt in the electrolyte and allows a thin, strong solid electrolyte film composed mainly of inorganic components to be formed on the electrode surface during the chemical formation process of the sodium-ion battery, thereby significantly reducing the problem of gas generation in the sodium-ion battery. Optionally, this concentration is 0.01 mol / L or more. Furthermore, this concentration is 0.12 mol / L or less, which effectively reduces the possibility of the sodium salt containing a phosphate group forming an excessive film on the electrode surface and does not significantly affect the dynamics of the charge and discharge processes of the sodium-ion battery.

[0019] In any embodiment, the sodium salts having a boric acid group include sodium tetrafluoroborate (NaBF), sodium metaborate (BNaO), sodium tetraphenylborate ((CH)BNa), and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (C 32 H 12 BF 24 Na), optionally including one or more of sodium tetrafluoroborate, sodium metaborate, and sodium tetraphenylborate, and further optionally including one or more of sodium tetrafluoroborate and sodium metaborate.

[0020] In any one of the embodiments, the concentration of the sodium salt having a boric acid group in the non-aqueous electrolyte solution is in the range of 0.0005 to 0.05 mol / L, and optionally in the range of 0.01 to 0.04 mol / L.

[0021] In the second sodium salt, the molar concentration of the boric acid-containing sodium salt in the nonaqueous electrolyte is 0.0005 mol / L or more, which can have a certain effect on improving the stability of the first sodium salt in the electrolyte and can also form a thin, dense solid electrolyte interfacial film on the electrode surface of a sodium-ion battery, thereby suppressing the continuous decomposition of the electrolyte solvent at the electrode / electrolyte interface, thereby significantly reducing the problem of gas generation in sodium-ion batteries, and also improving the cycling (especially at high temperatures) and capacity retention of sodium-ion batteries after high-temperature storage. Furthermore, this concentration is 0.05 mol / L or less, which effectively reduces the possibility of excessive film formation by the boric acid-containing sodium salt on the electrode surface and does not significantly affect the kinetics of the charge and discharge processes of sodium-ion batteries.

[0022] In any embodiment, when sodium hexafluorophosphate is used in combination with at least one of sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate in the first sodium salt, the concentration of the sodium salt other than sodium hexafluorophosphate in the non-aqueous electrolyte is 0.001 mol / L or more, optionally 0.01 mol / L or more, further optionally 0.03 mol / L or more, and 1 mol / L or less, optionally 0.5 mol / L or less.

[0023] In the first sodium salt, if the concentration of the sodium salt other than sodium hexafluorophosphate (NaPF6) in the non-aqueous solvent is 0.001 mol / L or more, it has the effect of improving the electrochemical performance of sodium-ion batteries at high temperatures. If the concentration ratio of the other sodium salt in the non-aqueous solvent is 1 mol / L or less, it is possible to control to some extent the solvation structure of sodium ions in the electrolyte and the chemical environment of the non-aqueous solvent molecules, which has the effect of suppressing the problem of electrolyte decomposition and gas generation under high temperature conditions, and has the effect of promoting the improvement of the electrochemical performance of sodium-ion batteries at high temperatures.

[0024] In any embodiment, the second sodium salt comprises a sodium salt having a sulfonic acid group, and further comprises one or more of a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group.

[0025] In the second sodium salt, the combination of a sodium salt having a sulfonic acid group with a sodium salt having one or more of an oxalic acid group, a phosphate group, and a boric acid group generates a synergistic effect, synergistically participating in the solvation process of sodium ions in the electrolyte, donating some electrons to the sodium ions, and effectively suppressing the strong electron-attracting tendency of sodium ions toward non-aqueous solvent molecules, thereby significantly suppressing the continuous decomposition of the electrolyte and gas generation. Furthermore, the combination of a sodium salt having a sulfonic acid group with a sodium salt having one or more of an oxalic acid group, a phosphate group, and a boric acid group can form a thin and dense solid electrolyte interfacial film rich in inorganic components at the electrode / electrolyte interface, which has the effect of significantly improving the electrochemical performance of sodium ion batteries (especially at high temperatures).

[0026] In any embodiment, the second sodium salt comprises a sodium salt having a sulfonic acid group and a sodium salt having an oxalic acid group, and optionally the molar ratio of the sodium salt having a sulfonic acid group to the sodium salt having an oxalic acid group is from 0.03 / 1 to 70 / 1, and optionally from 0.5 / 1 to 20 / 1.

[0027] The combined use of a sodium salt having an oxalic acid group with a sodium salt having a phosphate group and a sodium salt having a boric acid group has the effect of improving the effects of suppressing decomposition of the electrolyte and gas generation. When the molar ratio of the sodium salt having a sulfonic acid group to the sodium salt having an oxalic acid group is 1 / 1 to 10 / 1, there is a relatively high possibility that a thin solid electrolyte interfacial film mainly composed of inorganic components will form on the electrode surface during the charge / discharge process of a sodium ion battery.

[0028] In any one of the embodiments, the non-aqueous electrolyte solution contains a cyclic carbonate, and the mass concentration ratio of the cyclic carbonate in the non-aqueous electrolyte solution is 10% or more, and optionally 15% or more and 60% or less.

[0029] When the mass concentration ratio of the cyclic carbonate in the non-aqueous electrolyte is within the above range, the stability of the electrode / electrolyte interfacial film under high temperature conditions of a sodium ion battery can be improved to some extent without fundamentally affecting the sodium ion migration rate.

[0030] In any embodiment, the non-aqueous electrolyte solution contains a chain carbonate and a chain carboxylic acid ester, and the mass percentage of the sum of the chain carbonate and the chain carboxylic acid ester in the non-aqueous electrolyte solution is 40% or more, optionally 50% or more, more optionally 60% or more, and 90% or less, optionally 85% or less, and further optionally 80% or less.

[0031] If the mass percentage of the chain carbonate and chain carboxylic acid ester in the electrolyte is 40% or more, optionally 50% or more, and more optionally 60% or more, the viscosity of the electrolyte will not be too high. The upper limit of the content is 90% or less, optionally 85% or less, and more optionally 80% or less, the degree of decrease in ionic conductivity will not be large, and the impact on the electrochemical performance of the sodium ion battery will be relatively small.

[0032] In any embodiment, the non-aqueous electrolyte solution includes at least one cyclic carbonate and at least one chain ester, and the mass percentage of the at least one cyclic carbonate to the at least one chain ester is 0.1:1 or more and 1.5:1 or less, optionally 1:1 or less, and further optionally between 0.2:1 and 1:1.

[0033] When the mass percentages of the cyclic carbonate and the chain ester in the nonaqueous electrolyte described in the present application are within the above ranges, there is a certain effect of inhibiting the decomposition of the electrolyte and the gas generation phenomenon at high temperatures in a sodium ion battery, and there is a certain effect of promoting the improvement of the electrochemical performance of the sodium ion battery.

[0034] In any embodiment, the nonaqueous electrolyte solution includes one or more of a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate and an ether, a combination of a chain carbonate and a chain carboxylic acid ester, a combination of a chain carbonate and an ether, a combination of a chain carboxylic acid ester and an ether, a combination of a cyclic carbonate, a chain carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain carbonate and an ether, a combination of a cyclic carbonate, a chain carboxylic acid ester and an ether, and a combination of a chain carbonate, a chain carboxylic acid ester and an ether.

[0035] The non-aqueous electrolyte solution of the present application contains cyclic carbonates, chain carbonates, chain carboxylic acid esters, ethers, etc. as non-aqueous solvents. These specific combinations of non-aqueous solvents not only improve the dissolution and dispersion ability of the electrolyte sodium salt, but also participate in the formation of certain specific sodium ion solvation structures, thereby effectively suppressing the decomposition of the solvent in the electrolyte and the associated gas generation problems, and further improving the electrochemical performance of sodium ion batteries (especially under high temperature conditions).

[0036] In any embodiment, the non-aqueous solvent in the non-aqueous electrolyte includes one or more of propylene carbonate, ethyl methyl carbonate, ethyl acetate, diethyl carbonate, methyl propionate, ethyl propionate, diethylene glycol dimethyl ether, and fluoroethylene carbonate.

[0037] In any embodiment, the non-aqueous electrolyte solution includes one or more of an acid anhydride-based additive, a fluorine-containing organic additive, a nitrile-based additive, a silicone-based additive, an aldehyde-based additive, a sulfur-containing additive, a lithium salt-based additive, and a potassium salt-based additive, and optionally the total mass percentage of these additives in the non-aqueous electrolyte solution is 0.001% or more, optionally 0.2% or more and 5% or less, optionally 4% or less.

[0038] To further optimize the stability of film formation on the electrode surface during the charge / discharge process of a sodium ion battery and obtain a thin and dense electrode / electrolyte interfacial film mainly composed of inorganic components, the additive is selectively added to the electrolyte. The mass percentage of the additive in the non-aqueous electrolyte is 0.001% or more, and optionally 0.2% or more, to enhance the stability of film formation on the electrode surface. The upper limit is 5% or less, and optionally 4% or less, to reduce the possibility of excessive film formation on the electrode surface.

[0039] A second aspect of the present application provides a sodium-ion battery, which includes a positive electrode plate, a negative electrode plate, and the non-aqueous electrolyte described in the first aspect of the present application.

[0040] A third aspect of the present application provides a power consuming device, the power consuming device including the non-aqueous electrolyte described in the first aspect of the present application or the sodium ion battery described in the second aspect of the present application. [Brief explanation of the drawings]

[0041] [Figure 1]1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. 4. [Figure 6] 1 is a schematic diagram of a power consumption device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE INVENTION

[0042] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing a nonaqueous electrolyte and a sodium ion battery will be described in detail. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of structures that are actually the same may be omitted. This is to avoid unnecessary lengthening of the following description 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.

[0043] 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, with the selected lower and upper limits defining 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 of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 6 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 a list of all real numbers between "0-5" and is merely a shorthand representation of combinations of these numbers. Also, when a parameter is expressed as an integer ≧2, this is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] 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.

[0046] Unless otherwise specified, all steps in this application may be performed in order, randomly, or optionally in order. For example, when a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, when a method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, e.g., 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.

[0047] 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.

[0048] 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, the following conditions satisfy "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and both A and B are true (or exist).

[0049] Sodium-ion batteries are primarily composed of positive and negative electrode materials capable of absorbing and releasing sodium ions, along with an electrolyte containing sodium salt and a non-aqueous solvent. The electrolyte plays an important role in the development process of sodium-ion batteries. The electrolyte acts as a bridge for sodium ion transport between the positive and negative electrodes, determining the capacity of the positive and negative electrode materials and thereby affecting the electrochemical performance of the battery. However, the electrolyte can also be affected by factors such as the positive and negative electrode materials, the environment (e.g., temperature), and test conditions (e.g., voltage).

[0050] Generally, the electrolyte of a sodium-ion battery is significantly affected by the anode material. Anode materials for sodium-ion batteries include metallic sodium, carbon materials (e.g., hard carbon, graphite, etc.), and metal compounds (e.g., metal oxides, alloys, etc.). These materials often have a relatively low sodium absorption potential, which can lead to reductive decomposition of the electrolyte. The reductive decomposition of the electrolyte solvent on the anode surface becomes more severe, especially at high temperatures. Continuous decomposition of the solvent causes serious gas generation problems in sodium-ion batteries, and large amounts of generated gas (e.g., carbon dioxide, carbon monoxide, hydrogen, propylene, etc.) accumulate within the battery, increasing the risk of safety issues during use. Furthermore, the continuous decomposition of the solvent often results in the formation of a large amount of organic decomposition products, which are deposited on the surface of the negative electrode to form a thick and uneven organic solid electrolyte (SEI) film, which significantly slows the transfer kinetics of sodium ions at the negative electrode / electrolyte interface and ultimately deteriorates the electrochemical performance (e.g., cycle and rate performance) of the sodium-ion battery (especially at high temperatures). Furthermore, the continuous deposition of the organic SEI film causes the electrode to swell, and the electrode swelling and massive gas generation lead to volume expansion of the sodium-ion battery, which poses certain safety risks during the use of the sodium-ion battery.

[0051] The electrolyte in sodium-ion batteries can be affected by factors such as the operating voltage and chemical composition of the positive electrode material. Currently, the positive electrode materials used in sodium-ion batteries mainly include transition metal oxides, polyanion compounds, and Prussian blue analogues. These positive electrode materials often undergo sodium ion absorption / desorption reactions in the high-voltage range. Under high pressure, the electrolyte undergoes oxidative decomposition at the positive electrode, resulting in significant gas generation. Furthermore, the transition metals (e.g., iron, cobalt, nickel, etc.) in some metal oxide positive electrode materials have relatively strong catalytic properties and can catalyze the decomposition of the solvent and the electrolyte / positive electrode interfacial film. As a result, sodium-ion batteries require continuous consumption of electrolyte to form a film during use, resulting in the loss of large amounts of reversibly active sodium and solvent, ultimately significantly reducing the service life of the sodium-ion battery. Under high-temperature conditions, the decomposition rate of the electrolyte often accelerates significantly, exacerbating the gas generation problem. Furthermore, the continuous decomposition of the solvent generates a large amount of organic decomposition products, which are deposited on the surface of the positive electrode, forming a thick and uneven electrolyte / positive electrode interfacial film, which seriously increases the sodium ion transmission resistance at the electrolyte / positive electrode interface, ultimately affecting the electrochemical performance of the sodium ion battery.

[0052] During actual use of sodium-ion batteries, as the electrochemical reaction progresses, the battery continuously dissipates heat and its temperature rises. Under high-temperature conditions, the problem of gas generation due to electrolyte decomposition becomes more serious, which affects the industrial development of sodium-ion batteries. Therefore, it is of great research significance to design a rational electrolyte that can meet the high-temperature usage needs of sodium-ion batteries and improve the safety and electrochemical performance of sodium-ion batteries.

[0053] Our research has revealed that the gas generation problem in sodium-ion batteries is primarily due to the persistent decomposition of the solvent at the electrode / electrolyte interface, which is closely related to the chemical environment of the solvent electrolyte. Generally, in sodium-ion battery electrolytes, due to the difference in electrostatic potential between sodium ions and solvent molecules, sodium ions attract solvent molecules through electrostatic interactions and distribute around them, forming a solvated sodium-ion shell layer structure. However, due to the strong electron-attracting property of sodium ions, some solvent molecules transfer electrons to the sodium ions, weakening the chemical bond strength within the solvent molecules in the shell layer structure and reducing the chemical stability of these solvent molecules. At the same time, the lowest unoccupied molecular orbital (LUMO) energy of the solvated sodium ions is further reduced compared to pure solvent molecules. This makes the solvent molecules in the solvated sodium-ion housing structure more susceptible to reductive decomposition by gaining electrons at the anode surface, making the electrolyte more susceptible to reductive decomposition compared to pure solvent. Therefore, controlling the chemical environment of the solvent molecules in sodium-ion battery electrolytes is key to suppressing gas generation due to solvent decomposition.

[0054] Based on previous reports and our systematic research, we have found that the composition of metal salts (especially the anions in the metal salts) plays a crucial role in the chemical and electrochemical stability of batteries. In the same solvent, the type of metal salt determines the solvation structure and thermodynamic stability of the electrolyte, thereby influencing the electrolyte's decomposition behavior and further controlling the electrode / electrolyte interfacial properties and the electrode's electrochemical performance. Introducing electron-rich anions into the electrolyte system of sodium-ion batteries can significantly reduce the problems of solvent decomposition and gas generation. Electron-rich anions participate in the solvation structure of sodium ions, donating some electrons to the sodium ions and weakening their strong electron-withdrawing ability toward solvent molecules. This reduces the weakening of chemical bonds and the instability of molecular structures caused by local electron deficiencies in solvent molecules. Furthermore, our research has found that the type and radius of the anions can further control the solvation structure of sodium ions in the electrolyte and the chemical environment of solvent molecules. More importantly, several different types of anions can also have synergistic effects in the electrolyte. These anions act as electron "sponges" to donate electrons to the solvated shell layer of sodium ions, synergistically improving the chemical, electrochemical, and thermal stability of the electrolyte. Furthermore, our research has shown that when some electrons in some fluorine-containing anions are transferred to sodium ions, the local chemical bonds in the ionic structure are weakened, leading to preferential decomposition during the electrochemical reaction of sodium-ion batteries, forming a thin, dense electrode / electrolyte interfacial film rich in inorganic components. This significantly suppresses the persistent decomposition of the solvent in the electrolyte and gas evolution, effectively improving the electrochemical performance of sodium-ion batteries, especially at high temperatures.

[0055] Therefore, the purpose of this application is to provide a sodium ion battery electrolyte and a sodium ion battery containing electron-rich anions by controlling the solvation structure of sodium ions and the chemical environment of solvent molecules in the electrolyte, thereby solving the problem of gas generation caused by continuous decomposition of the solvent in sodium ion batteries.

[0056] Based on the above, a first aspect of the present application provides a non-aqueous electrolyte, the non-aqueous electrolyte comprising: a first sodium salt, the first sodium salt comprising at least one of sodium hexafluorophosphate (NaPF), sodium hexafluoroarsenate (NaAsF), sodium perchlorate (NaClO), and sodium trifluoroacetate (CFCOONa), optionally wherein the first sodium salt is sodium hexafluorophosphate; and a second sodium salt, the second sodium salt including one, two or more of a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group, and optionally the second sodium salt including a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group.

[0057] In the present application, the sulfonic acid group in the sodium salt having a sulfonic acid group is, for example, SO3 2- , (SO3CF3) - , [N(FSO2)2] - The oxalic acid group in the sodium salt having an oxalic acid group includes, but is not limited to, C2O4 2- , (C2O4BF2) - , [(C2O4)2B] - The boric acid group in the sodium salt having a boric acid group includes, but is not limited to, BF4 - , BO2 - The phosphate group in the sodium salt having a phosphate group includes, but is not limited to, for example, PO4 3- , (PO3F) 2- , (PO2F2) - This includes, but is not limited to:

[0058] The non-aqueous electrolyte is prepared by dissolving a sodium salt electrolyte containing electron-rich anions in a non-aqueous solvent. As described above, the selective addition of the first sodium salt and the second sodium salt can control the solvation structure of the sodium ions and the chemical environment of the solvent molecules in the electrolyte, thereby solving the problem of gas generation due to continuous decomposition of the solvent in sodium-ion batteries.

[0059] In some alternative embodiments, the molar concentration ratio of the first sodium salt to the second sodium salt in the nonaqueous electrolyte is 1 / 1 or more, optionally 2 / 1 or more, more optionally 5 / 1 or more, further optionally 10 / 1 or more, and is 1000 / 1 or less, optionally 40 / 1 or less, more optionally 20 / 1 or less.

[0060] In some embodiments, the molar concentration ratio of the first sodium salt to the second sodium salt in the non-aqueous electrolyte is 1 / 1 or more, optionally 3 / 1 or more, and 40 / 1 or less, more optionally 15 / 1 or less.

[0061] When the molar concentration ratio of the first sodium salt to the second sodium salt is within the above range in the entire electrolyte, the risk of excessive film formation on the electrode surface can be reduced and the transport resistance of sodium ions at the electrode / electrolyte interface can be reduced, thereby making the impact on the dynamic process of the sodium ion battery relatively small.

[0062] In some embodiments, the sodium salt having a sulfonic acid group is sodium fluorosulfonate (FSO3Na), sodium trifluoromethanesulfonate (NaSO3CF3), sodium bis(fluorosulfonyl)imide (Na[(FSO2)2N]), sodium bis(trifluoromethanesulfonyl)imide (Na[(CF3SO2)2N]), sodium methanesulfonate (CH3SO3Na), sodium vinylsulfonate (C2H3NaO3S), sodium methylsulfonate (CH3OSO3Na), methylthiosulfonate (Methylthiosulfonate), sodium methyl ... Sodium phosphate (CH3NaO2S2), disodium 1,2-ethanedisulfonate (NaO3SCH2CH2SO3Na), sodium ethyl sulfate (C2H5NaO4S), sodium propanesulfonate (C3H7NaO3S), sodium ethylthiosulfonate (C2H5NaO2S2), sodium 2-iodobenzenesulfonate (C6H4INaO3S), sodium 4-nitrobenzenemethanesulfonate (C7H6NNaO5S), sodium styrenesulfonate (C8H7NaO3S), sodium 4-cumenesulfonate (C9H 11 NaO3S), sodium phenolsulfonate (C6H5NaO4S), sodium β-styrenesulfonate (C8H7NaO3S), sodium cyclohexanesulfonate (C6H 11 NaO3S), sodium 2-cyclohexylaminoethanesulfonate (C8H 16 NNaO3S), 4-amino-N-methylbenzenesulfonylamide (CH 10 N2O2S), sodium polydithiodipropane sulfonate (C6H 12 Na2O6S4), sodium pyridine-3-sulfinate (C5H4NNaO2S), piperazine-1,4-diethanesulfonic acid sodium salt (C8H 17 N2NaO6S2), optionally including one or more of sodium fluorosulfonate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium methanesulfonate, and sodium methyl sulfate.

[0063] In some embodiments, the concentration of the sodium salt having a sulfonic acid group in the non-aqueous electrolyte is in the range of 0.0005 to 1 mol / L, and optionally in the range of 0.01 to 0.3 mol / L.

[0064] In some alternative embodiments, the concentration of the sodium salt having a sulfonic acid group in the non-aqueous electrolyte is 0.001 mol / L or more, optionally 0.01 mol / L or more, and 0.3 mol / L or less, optionally 0.15 mol / L or less.

[0065] In the second sodium salt, the concentration of the sulfonic acid group-containing sodium salt in the electrolyte is 0.0005 mol / L or more, which can improve the stability of the first sodium salt in the electrolyte, thereby forming a stable solid electrolyte interfacial film on the electrode surface during the electrochemical reaction process in a sodium-ion battery, effectively suppressing decomposition of the electrolyte solvent and gas generation on the electrode surface, and improving the electrochemical performance of the sodium-ion battery (especially at high temperatures). Optionally, the concentration of the sulfonic acid group-containing sodium salt in the electrolyte can be 0.01 mol / L or more. However, the concentration of the sulfonic acid group-containing sodium salt in the electrolyte can be 1 mol / L or less, which can more effectively reduce the risk of excessive film formation on the electrode and therefore does not significantly affect the electrochemical performance of the sodium-ion battery at high temperatures. Optionally, this concentration can be 0.15 mol / L or less.

[0066] In some embodiments, the sodium salt having an oxalic acid group comprises one or more of sodium oxalate (NaC0), sodium bis(oxalato)borate (CBNaO), sodium difluoro(oxalato)borate (CBFNaO), sodium tetrafluoro(oxalato)phosphate (CFNaOP), and sodium difluorobis(oxalato)phosphate (CFNaOP).

[0067] Sodium bis(oxalato)borate and sodium difluoro(oxalato)borate have both an oxalic acid group and a boric acid group, and may be classified as sodium salts having an oxalic acid group or as sodium salts having a boric acid group, and are herein classified as sodium salts having an oxalic acid group. Similarly, sodium tetrafluoro(oxalato)phosphate and sodium difluorobis(oxalato)phosphate may be classified as sodium salts having a phosphate group, and are herein classified as sodium salts having an oxalic acid group.

[0068] In some alternative embodiments, the concentration of the sodium salt having an oxalic acid group in the non-aqueous electrolyte is 0.001 mol / L or more, optionally 0.006 mol / L or more, and further optionally 0.01 mol / L or more and 0.08 mol / L or less.

[0069] In some embodiments, the concentration of the sodium salt having an oxalic acid group in the non-aqueous electrolyte solution is in the range of 0.0005 to 0.1 mol / L, optionally in the range of 0.006 to 0.08 mol / L, and further optionally in the range of 0.01 to 0.02 mol / L.

[0070] The second sodium salt has a concentration of 0.0005 mol / L or more in the electrolyte, which significantly improves the stability of the first sodium salt in the electrolyte and improves the high-temperature cycle performance and capacity retention rate of the sodium-ion battery after storage. Alternatively, this concentration may be 0.006 mol / L or more, and more preferably 0.01 mol / L or more. Preferably, this concentration is 0.08 mol / L or less, which effectively reduces the possibility of excessive film formation on the electrode by the sodium salt having oxalic acid groups and therefore does not significantly affect the kinetics of the charge / discharge cycle of the sodium-ion battery.

[0071] In some embodiments, the sodium salt having a phosphate group is sodium difluorophosphate (NaPOF), sodium monofluorophosphate (NaPOF), sodium trimetaphosphate (NaPO), sodium hexametaphosphate (NaPO 18 ), sodium hydroxyethylidene diphosphonate (C2H7NaO7P2), disodium clodronate (CH2Cl2Na2O6P2), sodium olpadronate (C5H 15 NO7P2), sodium diethylenetriamine pentamethylene phosphonate (C9H 18 N3Na 10 O 15 P5), sodium tripolyphosphate (Na5P3O 10 ) and disodium phenyl phosphate (C6H5Na2O4P), and optionally one or more of sodium difluorophosphate (NaPO2F2) and sodium fluorophosphate (Na2PO3F).

[0072] In some alternative embodiments, the concentration of the sodium salt having a phosphate group in the non-aqueous electrolyte is 0.001 mol / L or more, and optionally 0.01 mol / L or more and 0.12 mol / L or less.

[0073] In some embodiments, the concentration of the sodium salt having a phosphate group in the non-aqueous electrolyte solution is in the range of 0.0005 to 0.12 mol / L, optionally in the range of 0.01 to 0.05 mol / L, and more optionally in the range of 0.01 to 0.03 mol / L.

[0074] In the second sodium salt, the molar concentration of the phosphate-containing sodium salt in the nonaqueous electrolyte is 0.0005 mol / L or more, which improves the stability of the first sodium salt in the electrolyte and allows a thin, strong solid electrolyte film composed mainly of inorganic components to be formed on the electrode surface during the chemical formation process of the sodium-ion battery, thereby significantly reducing the problem of gas generation in the sodium-ion battery. Optionally, this concentration is 0.01 mol / L or more. Furthermore, this concentration is 0.12 mol / L or less, which effectively reduces the possibility of the phosphate-containing sodium salt forming an excessive film on the electrode surface and does not significantly affect the dynamics of the charge and discharge processes of the sodium-ion battery.

[0075] In some embodiments, the sodium salts having boric acid groups include sodium tetrafluoroborate (NaBF), sodium metaborate (BNaO), sodium tetraphenylborate ((C6H5)4BNa), and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (C 32 H 12 BF 24 Na), optionally including one or more of sodium tetrafluoroborate, sodium metaborate, and sodium tetraphenylborate, and further optionally including one or more of sodium tetrafluoroborate and sodium metaborate.

[0076] In some alternative embodiments, the concentration of the boric acid group-containing sodium salt in the non-aqueous electrolyte is 0.001 mol / L or more, and optionally 0.008 mol / L or more and 0.03 mol / L or less.

[0077] In some embodiments, the concentration of the boric acid group-containing sodium salt in the non-aqueous electrolyte is in the range of 0.0005 to 0.05 mol / L, and optionally in the range of 0.01 to 0.04 mol / L.

[0078] The molar concentration of the boric acid-containing sodium salt in the second sodium salt in the non-aqueous electrolyte is 0.0005 mol / L or more, which can improve the stability of the first sodium salt in the electrolyte and allow a thin, dense solid electrolyte interfacial film to form on the electrode surface during the electrochemical reaction in a sodium-ion battery. This suppresses the sustained decomposition of the electrolyte solvent at the electrode / electrolyte interface, thereby significantly reducing gas generation problems in the sodium-ion battery. It also improves the cycling performance of the sodium-ion battery (especially at high temperatures) and the capacity retention rate after high-temperature storage. Furthermore, this concentration is 0.05 mol / L or less, which effectively reduces the possibility of excessive film formation on the electrode surface by the boric acid-containing sodium salt and therefore does not significantly affect the dynamics of the charge / discharge cycles of the sodium-ion battery. Optionally, the concentration of the boric acid-containing sodium salt in the non-aqueous electrolyte is in the range of 0.01 to 0.02 mol / L.

[0079] In some embodiments, when sodium hexafluorophosphate is used in combination with at least one of sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate in the first sodium salt, the concentration of the sodium salt other than sodium hexafluorophosphate in the non-aqueous electrolyte is 0.001 mol / L or more, optionally 0.01 mol / L or more, further optionally 0.03 mol / L or more, and 1 mol / L or less, optionally 0.5 mol / L or less.

[0080] Alternatively, in the first sodium salt, the concentration of the sodium salt other than sodium hexafluorophosphate (NaPF6) in the non-aqueous solvent is preferably 0.005 mol / L or more, more preferably 0.01 mol / L or more, and even more preferably 0.02 mol / L or more, and the upper limit of the concentration is preferably 0.7 mol / L or less, and even more preferably 0.6 mol / L or less.

[0081] The concentration of sodium hexafluorophosphate in the non-aqueous electrolyte solution described in the present application may be any concentration or a normal concentration, and optionally the concentration of sodium hexafluorophosphate in the non-aqueous electrolyte solution described in the present application is 0.4 to 1.6 mol / L.

[0082] In the first sodium salt, if the concentration of the sodium salt other than sodium hexafluorophosphate (NaPF6) in the non-aqueous solvent is 0.001 mol / L or more, it has the effect of improving the electrochemical performance of sodium-ion batteries at high temperatures. If the concentration ratio of the other sodium salt in the non-aqueous solvent is 1 mol / L or less, it is possible to control to some extent the solvation structure of sodium ions in the electrolyte and the chemical environment of the non-aqueous solvent molecules, which has the effect of suppressing the problem of electrolyte decomposition and gas generation under high temperature conditions, and has the effect of promoting the improvement of the electrochemical performance of sodium-ion batteries at high temperatures.

[0083] In some embodiments, the second sodium salt comprises a sodium salt having a sulfonic acid group, and further comprises one or more of a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group.

[0084] In the second sodium salt, the combination of a sodium salt having a sulfonic acid group with a sodium salt having one or more of an oxalic acid group, a phosphate group, and a boric acid group generates a synergistic effect, synergistically participating in the solvation process of sodium ions in the electrolyte, donating some electrons to the sodium ions, and effectively suppressing the strong electron-attracting tendency of sodium ions toward non-aqueous solvent molecules, thereby significantly suppressing the continuous decomposition of the electrolyte and gas generation. Furthermore, the combination of a sodium salt having a sulfonic acid group with a sodium salt having one or more of an oxalic acid group, a phosphate group, and a boric acid group can form a thin and dense solid electrolyte interfacial film rich in inorganic components at the electrode / electrolyte interface, which has the effect of significantly improving the electrochemical performance of sodium ion batteries (especially at high temperatures).

[0085] In some embodiments, the second sodium salt comprises a sodium salt having a sulfonic acid group and a sodium salt having an oxalic acid group, and optionally the molar ratio of the sodium salt having a sulfonic acid group to the sodium salt having an oxalic acid group is from 0.03 / 1 to 70 / 1, and optionally from 0.5 / 1 to 20 / 1. Still more optionally, the molar ratio of the sodium salt having a sulfonic acid group to the sodium salt having an oxalic acid group is from 1 / 1 to 10 / 1.

[0086] The combined use of a sodium salt having an oxalic acid group with a sodium salt having a phosphate group and a sodium salt having a boric acid group has the effect of improving the effect of suppressing decomposition of the electrolyte and gas generation. When the molar ratio of the sodium salt having a sulfonic acid group to the sodium salt having an oxalic acid group is 1 / 1 to 10 / 1, there is a relatively high possibility that a thin solid electrolyte interfacial film mainly composed of inorganic components will form on the electrode surface during the charge / discharge process of a sodium-ion battery.

[0087] The non-aqueous solvent in the non-aqueous electrolyte may include a cyclic carbonate, a linear ester, and / or an ether, and optionally, the non-aqueous solvent includes one or more of a cyclic carbonate, a chain carbonate, a chain carboxylic acid ester, and an ether.

[0088] In some embodiments, the non-aqueous electrolyte solution contains a cyclic carbonate, and the mass concentration of the cyclic carbonate in the non-aqueous electrolyte solution is 10% or more, optionally 15% or more and 60% or less.

[0089] The cyclic carbonate is one that is commonly used as a solvent in batteries, and includes, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), propylene sulfite (PS), vinylethylene carbonate (VEC), 4-ethynyl-1,3-dioxolan-2-one (EEC), cis-4,5-difluoro-1,3-dioxolan-2-one, and trans-4,5-difluoro-1,3-dioxolan-2-one, and optionally one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC).

[0090] When the mass concentration ratio of the cyclic carbonate in the non-aqueous electrolyte is within the above range, the stability of the electrode / electrolyte interfacial film under high temperature conditions of a sodium ion battery can be improved to some extent without fundamentally affecting the sodium ion migration rate.

[0091] Among cyclic carbonates, the use of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) and vinylene carbonate (VC) has a certain improving effect on the dynamic process of sodium ion batteries at high temperatures.

[0092] In some embodiments, the non-aqueous electrolyte solution contains a chain carbonate and a chain carboxylic acid ester, and the mass percentage of the sum of the chain carbonate and the chain carboxylic acid ester in the non-aqueous electrolyte solution is 40% or more, optionally 50% or more, more optionally 60% or more, and 90% or less, optionally 85% or less, and further optionally 80% or less.

[0093] The chain carbonate can be used as a solvent in a battery and may optionally include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, ethyl propyl carbonate, dipropyl carbonate, and dibutyl carbonate, and the chain carbonate may optionally include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC).

[0094] The chain carboxylic acid ester can be used as a solvent in a battery, and optionally includes one or more of methyl formate (MF), ethyl formate (EF), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate (EB), methyl acetate (MA), ethyl acetate (EA), and propyl acetate (PA), and optionally includes one or more of methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl acetate (MA), ethyl acetate (EA), and propyl acetate (PA).

[0095] If the mass percentage of the chain carbonate and chain carboxylic acid ester in the electrolyte is 40% or more, optionally 50% or more, and more optionally 60% or more, the viscosity of the electrolyte will not be too high. The upper limit of the content is 90% or less, optionally 85% or less, and more optionally 80% or less, the degree of decrease in ionic conductivity will not be large, and the impact on the electrochemical performance of the sodium ion battery will be relatively small.

[0096] In some embodiments, the non-aqueous electrolyte solution comprises at least one cyclic carbonate and at least one linear ester, and the mass percentage of the at least one cyclic carbonate to the at least one linear ester is 0.1:1 or more and 1.5:1 or less, optionally 1:1 or less, and further optionally between 0.2:1 and 1:1.

[0097] The cyclic carbonate is as described above. The chain ester includes the chain carbonate and chain carboxylic acid ester described above.

[0098] Optionally, the total number of types of cyclic carbonates and chain esters in the non-aqueous electrolyte solution described in the present application is two or more.

[0099] When the mass percentages of the cyclic carbonate and the chain ester in the nonaqueous electrolyte described in the present application are within the above ranges, there is a certain effect of inhibiting the decomposition of the electrolyte and the gas generation phenomenon at high temperatures in a sodium ion battery, and there is a certain effect of promoting the improvement of the electrochemical performance of the sodium ion battery.

[0100] In some embodiments, the non-aqueous electrolyte solution comprises one or more of a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate and an ether, a combination of a chain carbonate and a chain carboxylic acid ester, a combination of a chain carbonate and an ether, a combination of a chain carboxylic acid ester and an ether, a combination of a cyclic carbonate, a chain carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain carbonate and an ether, a combination of a cyclic carbonate, a chain carbonate and an ether, a combination of a cyclic carbonate, a chain carboxylic acid ester and an ether, or a combination of a chain carbonate, a chain carboxylic acid ester and an ether.

[0101] As described above, the cyclic carbonate, the chain carbonate, and the chain carboxylic acid ester can be used as a solvent in the battery, and optionally includes one or more of dioxolane (DOL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2Me-THF), tetrahydropyran (THP), 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (DG), 1,2-diethoxyethane, and 1,2-dibutoxyethane.

[0102] The non-aqueous electrolyte solution of the present application contains cyclic carbonates, chain carbonates, chain carboxylic acid esters, ethers, etc. as non-aqueous solvents. These specific combinations of non-aqueous solvents not only improve the dissolution and dispersion ability of the electrolyte sodium salt, but also participate in the formation of certain specific sodium ion solvation structures, thereby effectively suppressing the decomposition of the solvent in the electrolyte and the associated gas generation problems, further improving the electrochemical performance of sodium ion batteries (especially under high temperature conditions).

[0103] In some embodiments, the non-aqueous solvent in the non-aqueous electrolyte includes one or more of propylene carbonate, ethyl methyl carbonate, ethyl acetate, diethyl carbonate, methyl propionate, ethyl propionate, diethylene glycol dimethyl ether, and fluoroethylene carbonate.

[0104] In some embodiments, the non-aqueous electrolyte solution includes one or more of an acid anhydride-based additive, a fluorine-containing organic additive, a nitrile-based additive, a silicone-based additive, an aldehyde-based additive, a sulfur-containing additive, a lithium salt-based additive, and a potassium salt-based additive, and optionally the total mass percentage of these additives in the non-aqueous electrolyte solution is 0.001% or more, optionally 0.2% or more, and 5% or less, optionally 4% or less.

[0105] In order to further optimize the stability of the film formed on the electrode surface during the charge and discharge process of sodium ion batteries and to obtain a thin and dense electrode / electrolyte interfacial film mainly composed of inorganic components, some additives can be selectively added to the electrolyte, for example, some additives can be added, and currently the specifics are introduced as follows:

[0106] The acid anhydride additive may be used in the electrolyte, and may include, but is not limited to, one or more of succinic anhydride, maleic anhydride, caproic anhydride, maleic anhydride, succinic anhydride, butyric anhydride, crotonic anhydride, phthalic anhydride, pyromellitic dianhydride, allylsuccinic anhydride, or 3-allylsuccinic anhydride; The fluorine-containing organic additive may include, but is not limited to, one or more of fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), tris(2,2,2-trifluoroethyl) borate, tris(hexafluoroisopropyl) phosphate, and tris(2,2,2-trifluoroethyl) phosphite; Nitrile additives may be used in the electrolyte, and may include, but are not limited to, one or more of succinonitrile, malononitrile, isophthalonitrile, glutaronitrile, methoxypentafluorocyclotriphosphazene, acrylonitrile, cyclobutanenitrile, dimethylaminopropionitrile, ethoxypentafluorocyclotriphosphazene, dicyandiamide, phenoxypentafluorocyclotriphosphazene, ethyl cyanoacrylate, p-chlorophenylacetonitrile, 2-chloro-5-nitrobenzonitrile, p-toluenesulfonylmethylisonitrile, adiponitrile, and pimelonitrile, Silicone-based additives may be used in the electrolyte and may include, but are not limited to, one or more of silane, trimethylsilanol, trimethylchlorosilane, hexamethyldisiloxane, bis(diethylamino)silane, chloromethylsilane, octamethylcyclotetrasiloxane, N-methyl-N-trimethylsilane trifluoroacetamide, diphenylsilanediol, phenyltrichlorosilane, chlorophenylsilane, tris(trimethylsilane)phosphate, bromodifluoro(trimethylsilyl)methane, or methyldichlorosilane. The aldehyde additive may include, but is not limited to, one or more of, for example, 2-imidazole carboxaldehyde, 3-indole carboxaldehyde, 2-pyrrole carboxaldehyde, p-chlorobenzaldehyde, 6-chloronicotinaldehyde, 1-methylindole-3-carboxaldehyde, 2-aldehydethiazole, 5-chloro-2-furfural, or azole-2-carboxaldehyde; The sulfur-containing additive may be used in the electrolyte, and may include, but is not limited to, one or more of thiourea, sultone, 1,5-naphthalenedisulfonic acid, dimethyl sulfone, sulfolane, methylsulfonic anhydride, dimethyl sulfoxide, 2-mercapto-5-methyl-1,3,4-thiadiazole, dithiooxalamide, tert-butyldimethylsilyl triflate, disodium 2,7-dihydroxynaphthalene-3,6-disulfonate, vinyl sulfate, propylene sulfate, butylene sulfate, or vinyl sulfone; The lithium salt additive may be used in the electrolyte, and may include, but is not limited to, one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoroacetate, lithium fluorosulfonate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium methanesulfonate, or lithium ethyl sulfate. The potassium salt additive may be used in the electrolyte, and may include, but is not limited to, one or more of potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium trifluoroacetate, potassium fluorosulfonate, potassium trifluoromethanesulfonate, potassium bis(fluorosulfonyl)imide, and potassium bis(trifluoromethanesulfonyl)imide. The mass percentage of the additive in the non-aqueous electrolyte is 0.001% or more, and optionally 0.2% or more, which has the effect of enhancing the stability of film formation on the electrode surface, and the upper limit is 5% or less, and optionally 4% or less, which reduces the possibility of excessive film formation on the electrode surface.

[0107] The detection of the components of the electrolyte of the sodium ion battery in this application can be carried out by referring to the Standard for Detection of Sodium Salt in Electrolyte: General Rules for Ion Chromatography Analysis Method in General Rules for Analytical Methods of Modern Analytical Instruments (JY / T 020-1996, promulgated on January 23, 1997, implemented on April 1, 1997), and the sodium salt and anions in the electrolyte are tested and analyzed using the ion chromatography analysis method.

[0108] A second aspect of the present application provides a sodium-ion battery, which includes a positive electrode plate, a negative electrode plate, and the non-aqueous electrolyte described in the first aspect of the present application.

[0109] All of the above statements regarding the non-aqueous electrolyte also apply to the sodium ion battery described as the second aspect of the present application and the power consuming device described as the third aspect of the present application.

[0110] In the sodium ion battery, the use of components such as the positive electrode plate, the negative electrode plate, and the separator other than the nonaqueous electrolyte is not particularly limited.

[0111] The positive electrode material used in the sodium ion battery positive electrode plate in this application is an electroactive material that can reversibly absorb / desorb sodium ions, and may include, but is not limited to, any one of transition metal oxides, Prussian blue analogs, polyanionic compounds, and organic positive electrode materials, but this application is not limited to these materials.

[0112] In the present application, the negative electrode material used in the negative electrode plate of a sodium ion battery is an electroactive material that can reversibly absorb / desorb sodium ions, and may be appropriately selected from any one of metallic sodium, hard carbon, graphite, metal oxide, metal sulfide, metal phosphide, and alloy negative electrode, but the present application is not limited to these materials.

[0113] In the sodium ion battery described in the present application, the positive electrode plate and the negative electrode plate may further include a conductive agent and an adhesive, the type and content of which are not specifically limited and can be selected and optimized according to actual needs.

[0114] In the sodium ion battery described in the present application, the separator is often disposed between the positive electrode plate and the negative electrode plate, and serves to separate the positive and negative electrode plates. The type and thickness of the separator are not specifically limited, and may be any one of separator materials conventionally used in batteries, such as polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer composite film thereof, but the present application is not limited to these materials.

[0115] In some alternative embodiments, the sodium ion battery includes a positive electrode plate and a negative electrode plate, and the capacity ratio of the positive electrode plate to the negative electrode plate is 1:(1 to 1.3).

[0116] In the sodium ion battery of the present application, when the capacity ratio of the positive electrode plate to the negative electrode plate is within the above range, the possibility of the electrolyte forming an excessive film on the electrode surface is reduced, and the rate of continuous decomposition of the electrolyte and the accompanying gas generation can be appropriately slowed, which promotes the improvement of the electrochemical performance of the sodium ion battery (especially at high temperatures).

[0117] For example, the test method for the capacity ratio between the positive and negative plates is as follows.

[0118] Positive electrode plate capacity test: The positive electrode plate was punched into a small wafer with a diameter of 14 mm, and a button battery was assembled using a metallic sodium sheet as the negative electrode and a polypropylene film as the separator. A constant current charge / discharge test was performed at a rate of 0.1 C in the voltage range of 1.5 to 4.2 V to obtain the positive electrode charge specific capacity Q1. Negative plate capacity test: The negative plate was punched into a small wafer with a diameter of 14 mm, and a metallic sodium sheet was used as the negative electrode and a polypropylene film was used as the separator to assemble a button battery. A constant current charge / discharge test was performed in the voltage range of 0.005 to 2 V. The discharge process was performed at a constant current discharge rate of 0.05 C, 40 μA, and 10 μA to 0.005 V, and the charge process was performed at a constant current charge rate of 0.05 C to 2 V. The charge specific capacity was Q2. The positive and negative electrode capacity ratio is Q1 / Q2.

[0119] In some embodiments, the positive and negative plates and separators can be fabricated into an electrode assembly by a winding or lamination process.

[0120] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and electrolyte.

[0121] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the 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.

[0122] The present application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows an example of a rectangular secondary battery.

[0123] In some embodiments, referring to FIG. 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and 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 in the accommodating cavity. An electrolyte 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 actual needs.

[0124] Secondary batteries include battery cell types, battery module types, and battery pack types. In some embodiments, the battery cells may be assembled into a battery module, and the number of battery cells 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.

[0125] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, a plurality of battery cells 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 battery cells 5 may be fixed by fasteners.

[0126] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of battery cells 5 are accommodated in this accommodating space.

[0127] In some embodiments, the battery cells may be assembled into a battery pack. In some embodiments, the battery modules may be further assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0128] 4 and 5 show an example of a battery pack 1. Referring to FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 may cover the lower housing 3 to 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.

[0129] The present application further provides a power consuming device, the power consuming device including a secondary battery according to the second aspect of the present application. The secondary battery 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.

[0130] The power consumption device may be a secondary battery selected according to its usage demand.

[0131] An example of a power consumption device is shown in Figure 6. The power consumption device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the demand for high power output and high energy density of secondary batteries in these power consumption devices, a battery pack or a battery module may be employed.

[0132] 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 secondary battery as a power source.

[0133] Example The following describes examples of the present application. The examples described below are illustrative and are used only to interpret the present application, and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be carried out according to the techniques or conditions described in literature in the field or according to the product instructions. If the manufacturer of the reagents or instruments used is not specified, they are all commercially available ordinary products.

[0134] The present application will be further described below in conjunction with examples, which are used only to illustrate the present application and are not intended to limit the scope of the present application.

[0135] The secondary batteries of the examples and comparative examples are all manufactured according to the following method.

[0136] (1) Electrolyte production Example 1: In an argon gas atmosphere glove box (H2O<0.1 ppm, O2<0.1 ppm), non-aqueous organic solvents (see Table 1 below) were uniformly mixed in the mass ratios shown in Table 1, and the first sodium salt, the second sodium salt, and sodium salts such as additives shown in Table 1 were slowly added thereto and stirred uniformly to obtain the corresponding electrolyte solution. The other examples and comparative examples are all similar to Example 1, and the corresponding non-aqueous electrolytes were prepared using the non-aqueous solvent, first sodium salt, second sodium salt, and additives shown in Table 1. (2) Manufacturing of positive electrode plates Positive electrode active material NaCu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 O2, acetylene black as a conductive agent, and polyvinylidene fluoride as an adhesive are dissolved in N-methylpyrrolidone solvent in a mass ratio of 94:3:3, and the mixture is thoroughly and uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated on a positive electrode current collector, which is then dried, cold pressed, and slit to obtain a positive electrode plate. (3) Manufacturing of negative electrodes The active material hard carbon, the conductive agent acetylene black, the adhesive styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose were dissolved in a solvent deionized water in a weight ratio of 95:2:2:1, and the mixture was uniformly mixed with the solvent deionized water to prepare a negative electrode slurry. The negative electrode slurry was then uniformly coated on a negative electrode current collector copper foil, which was then dried, cold pressed, and slit to obtain a negative electrode plate. (4) Separator manufacturing A polypropylene membrane was used as a separator. (5) Manufacturing of sodium-ion batteries (battery cores) A positive electrode plate, a separator, and a negative electrode plate were stacked in this order, and a separator was placed between the positive and negative electrodes to provide isolation. The stack was then wound and packaged to obtain a pouch cell. After vacuum drying, an electrolyte was injected, and the cells were subjected to processes such as chemical formation and standing to produce a sodium ion pouch cell with a capacity of 2 Ah.

[0137] TIFF2025531407000002.tif236143TIFF2025531407000003.tif236135

[0138] The meanings of the abbreviations in Table 1 are as follows:

[0139] Solvent abbreviations: PC: propylene carbonate, EMC: ethyl methyl carbonate, DEC: diethyl carbonate, EP: ethyl propionate, DG: diethylene glycol dimethyl ether, Abbreviations for sodium salts: NaPF6: sodium hexafluorophosphate, NaAsF6: sodium hexafluoroarsenate, NaClO4: sodium perchlorate, C2F3NaO2: sodium trifluoroacetate, Na(FSO2)2N: sodium bis(fluorosulfonyl)imide, CF3NaO3S: sodium trifluoromethanesulfonate, C2BF2NaO4: sodium difluoro(oxalato)borate, C4BNaO8: sodium bis(oxalato)borate, NaPO2F2: sodium difluorophosphate, Na2PO3F: sodium monofluorophosphate, NaBF4: sodium tetrafluoroborate, BNaO2: sodium metaborate. Additive abbreviations: FEC: Fluoroethylene carbonate.

[0140] All materials related to the table are chemically pure and commercially available.

[0141] The following is the test process of the relevant parameters:

[0142] 1. Sodium-ion battery internal resistance mΩ test At 25°C, the sodium-ion battery was charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current was less than 0.05C, and then discharged at 1C for 30 minutes to adjust the battery core power to 50% SOC. The positive and negative probes of a TH2523A AC internal resistance tester were then contacted to the positive and negative electrodes of the battery, respectively, and the internal resistance of the battery was read by the internal resistance tester.

[0143] 2. Capacity retention test at 25℃ for 500 cycles At 25°C, a sodium-ion battery was charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current fell below 0.05C, and then discharged at a constant current of 1C to 1.5V, and then discharged at a constant current of 0.04C to 1.5V, constituting one charge-discharge cycle. The capacity retention of the sodium-ion battery after 500 cycles of repeated charge-discharge cycles was calculated. The specific calculation formula is as follows:

[0144] Capacity retention rate (%) of a sodium-ion battery after 500 cycles at 25°C = (discharge capacity at 500th cycle / discharge capacity at first cycle) x 100%.

[0145] 3. Capacity retention test at 45℃ for 500 cycles At 45°C, a sodium-ion battery was charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current fell below 0.05C, and then discharged at a constant current of 1C to 1.5V, and then discharged at a constant current of 0.04C to 1.5V, constituting one charge-discharge cycle. The capacity retention of the sodium-ion battery after 500 cycles of repeated charge-discharge cycles was calculated. The specific calculation formula is as follows:

[0146] Capacity retention rate (%) of a sodium-ion battery after 500 cycles at 45°C = (discharge capacity at 500th cycle / discharge capacity at first cycle) x 100%.

[0147] 4. Capacity retention test after high temperature storage At 25°C, a sodium-ion battery was discharged at a constant current of 1 / 3C to 1.5V, then charged at a constant current of 1 / 3C to 4.2V, and charged at a constant voltage of 4.2V until the current dropped below 0.05C. The battery was then stored at 60°C in a thermostatic chamber for two months. After high-temperature storage, the sodium-ion battery was cooled to 25°C and discharged at a constant current of 1 / 3C to 1.5V. The capacity retention of the sodium-ion battery after storage at 60°C and 4.2V was calculated. The specific calculation formula is as follows:

[0148] Capacity retention rate (%) of a sodium-ion battery after high-temperature storage at 60°C = (discharge capacity at 25°C after high-temperature storage / initial discharge capacity at 25°C) x 100%.

[0149] 5. Volume expansion test after high temperature storage At 25°C, the battery was charged at a constant current of 1C until the voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current reached 0.05C. At this time, the volume of the sodium-ion battery was tested and designated as V1. The fully charged sodium-ion battery was then placed in a thermostatic box at 60°C and stored for two months. The volume was then tested using the drainage method and designated as V2.

[0150] Volume expansion rate (%) of a sodium-ion battery after storage at 60°C for 2 months = (V2-V1) / V1 x 100%.

[0151] The test results for each example and comparative example are as follows:

[0152] TIFF2025531407000004.tif160156TIFF2025531407000005.tif123156

[0153] As can be seen from the data in Tables 1 and 2, compared to Comparative Examples 1 to 6, Examples 1 to 43 significantly reduced the battery volume expansion rate after high-temperature storage while ensuring the same internal resistance of the battery, and improved the capacity retention rate at room temperature, after high-temperature cycling, and after high-temperature storage.

[0154] As can be seen from the experimental results of Comparative Example 1, even with the presence of the film-forming additive FEC, the sodium-ion battery based on the ester-based electrolyte still exhibited relatively poor cycling performance at 25°C. When the temperature rose to 45°C, the capacity retention rate of the sodium-ion battery after 500 cycles significantly decreased. More seriously, the volume expansion rate of the sodium-ion battery after two months of high-temperature storage was relatively high. This was due to the severe decomposition of the electrolyte during the charge and discharge process of the sodium-ion battery, resulting in the generation of large amounts of gas, which poses a serious safety risk during the use of the sodium-ion battery.

[0155] As can be seen from Comparative Examples 2 to 5, the addition of a second sodium salt containing an electron-rich anion (having sulfonic acid, oxalic acid, phosphate, or boric acid groups) to the electrolyte of Comparative Example 1 improved the capacity retention of the sodium-ion battery after 500 cycles at 25°C and 45°C, as well as after high-temperature (60°C) storage, and reduced the volume expansion rate of the battery. This indicates that the addition of a second sodium salt containing an electron-rich anion can somewhat mitigate the decomposition of the electrolyte and the associated gas generation problem. This is because the solvation structure in which the electron-rich anion joins the sodium ion provides some electrons to the sodium ion, weakening the strong electron-attracting effect of the sodium ion on the solvent molecules in the electrolyte and reducing the extent of the reduction in the chemical bond strength within the solvent molecules, thereby suppressing the decomposition of the solvent molecules and the associated gas generation problem. However, the addition of a sodium salt containing a single electron-rich anion did not have a significant inhibitory effect, which may be related to the number and size of the anion, the electron-donating ability, and the film formation conditions.

[0156] As can be seen from Comparative Example 6, after the first sodium salt (NaPF6) was removed from the electrolyte, the cycle performance of the sodium-ion battery at 25°C and 45°C and the capacity retention rate after high-temperature storage at 60°C were significantly deteriorated. This indicates that the first sodium salt plays an essential role in the overall electrochemical performance of the sodium-ion battery, and that the combined use of the first sodium salt and the second sodium salt can synergistically improve the electrochemical performance of the sodium-ion battery. In addition, the content of the second sodium salt also has a certain effect on the electrochemical performance of the sodium-ion battery.

[0157] As can be seen from Examples 1 to 5, adding 0.0005M and 0.001M of a second sodium salt (Na(FSO2)2N) having sulfonic acid groups to the electrolyte (Examples 1 and 2) improved the 25°C and 45°C cycle performance of the battery, significantly improved the capacity retention rate after high-temperature storage at 60°C, and significantly reduced the battery volume expansion rate after high-temperature storage. However, such low contents of second sodium salt (Na(FSO2)2N) had a relatively poor control effect on the electrolyte. It should be noted that adding 0.01M and 0.03M of second sodium salt (Na(FSO2)2N) (Examples 3 and 4) further improved the electrochemical performance of the sodium-ion battery, with clear improvements in each performance compared to Comparative Examples 1 to 6. As can be seen from Example 5, when the amount of the second sodium salt (Na(FSO2)2N) added is 1M, the resistance of the sodium ion battery increases, because the excessive addition of the second sodium salt leads to excessive film formation, which deteriorates the interfacial resistance and affects the dynamic process of the sodium ion battery.

[0158] In addition to the second sodium salt having sulfonic acid groups, the second sodium salt having oxalic acid groups also had a certain effect on the electrochemical performance of sodium-ion batteries. As can be seen from Examples 6 to 11, adding 0.0005 M of the second sodium salt having oxalic acid groups (CBFNaO) could improve the electrochemical performance of sodium-ion batteries. When the amount added exceeded 0.015 M, the electrochemical performance of the corresponding batteries deteriorated, indicating that excessive addition could affect the interfacial impedance and kinetics of sodium-ion batteries.

[0159] As can be seen from Examples 12-23, the addition of a second sodium salt containing an electron-rich anion (having a phosphate / borate group) similarly enhanced the electrochemical performance of sodium-ion batteries.

[0160] Furthermore, as can be seen from Examples 24 to 29, the blending of a second sodium salt having a sulfonic acid group, an oxalic acid group, a phosphate group, and a boric acid group had a certain improvement effect on the 25°C / 45°C cycle performance, high-temperature storage performance, and volume expansion coefficient at high temperatures of the sodium ion battery.

[0161] As can be seen from Examples 30 to 33, by changing the type of second sodium salt having a sulfonic acid group, an oxalic acid group, a phosphate group, and a boric acid group, a similar improvement effect was also observed on the electrochemical performance of the sodium ion battery.

[0162] As can be seen from Examples 34 to 39, the addition of a second sodium salt containing an electron-rich anion (having a sulfonic acid group, an oxalic acid group, a phosphate group, or a boric acid group) to an electrolyte containing a carboxylic acid ester and an ether-based solvent in addition to a carbonate-based solvent also had a similar inhibitory effect on electrolyte decomposition and gas generation in sodium-ion batteries, promoting improved electrochemical performance of sodium-ion batteries (especially at high temperatures). This indicates that the addition of a second sodium salt can provide relatively good control over the solvation process of sodium ions in the electrolyte and the chemical environment of the solvent molecules in the electrolyte, and facilitates the formation of a thin, dense solid electrolyte interfacial film primarily composed of inorganic components, thereby effectively inhibiting the decomposition of the solvent in the electrolyte and the associated gas generation problems, and improving the electrochemical performance of sodium-ion batteries. Furthermore, even after simultaneously adding four types of second sodium salts containing electron-rich anions (having sulfonic acid groups, oxalic acid groups, phosphate groups, and boric acid groups) to the electrolyte, the impedance value of the sodium-ion battery did not change significantly, indicating that the simultaneous use of sodium salts containing electron-rich anions is relatively unlikely to affect the impedance of the sodium-ion battery.

[0163] As can be seen from Examples 40 to 42, the use of a combination of the second sodium salt with a different type of first sodium salt also had a certain improvement effect on the electrochemical performance of the sodium ion battery. At the same time, it was found that there was a certain difference in the electrochemical performance of the sodium ion battery when different types of first sodium salts were used in the electrolyte.

[0164] Furthermore, as can be seen from Example 43, after the additive FEC was removed from the electrolyte, the electrochemical performance of the sodium ion battery deteriorated, which indicates that the additive in the electrolyte participates in the formation of the electrode / electrolyte interfacial film in the sodium ion battery and also plays an important role in improving the electrochemical performance of the sodium ion battery.

[0165] The non-aqueous electrolyte of the sodium ion battery and the sodium ion battery of the present application have certain suitability for solving the problems of electrolyte decomposition and gas generation that exist in the actual application process of the sodium ion battery, and have relatively good applicability in the industrialization process.

[0166] 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. It should be noted that various modifications that a person skilled in the art can make to the embodiments and other methods that are constructed by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0167] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate

Claims

1. A non-aqueous electrolyte solution, a first sodium salt, the first sodium salt comprising at least one of sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate; optionally, the first sodium salt is sodium hexafluorophosphate; A non-aqueous electrolyte solution comprising a second sodium salt, the second sodium salt comprising one, two or more of a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group, and optionally the second sodium salt comprising a sodium salt having a sulfonic acid group, a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group.

2. 2. The non-aqueous electrolyte according to claim 1, wherein the molar concentration ratio of the first sodium salt to the second sodium salt in the non-aqueous electrolyte is 1 / 1 or more, optionally 3 / 1 or more, and 40 / 1 or less, more optionally 15 / 1 or less.

3. Examples of the sodium salt having a sulfonic acid group include sodium fluorosulfonate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium methanesulfonate, sodium vinylsulfonate, sodium methyl sulfate, sodium methylthiosulfonate, disodium 1,2-ethanedisulfonate, sodium ethyl sulfate, sodium propanesulfonate, sodium ethylthiosulfonate, sodium 2-iodobenzenesulfonate, sodium 4-nitrobenzenemethanesulfonate, sodium styrenesulfonate, sodium 4-cumenesulfonate, sodium phenolsulfonate, and sodium β-styrenesulfonate.

3. The non-aqueous electrolyte solution according to claim 1, further comprising one or more of sodium benzenesulfonate, sodium cyclohexanesulfonate, sodium 2-cyclohexylaminoethanesulfonate, 4-amino-N-methylbenzenesulfonylamide, sodium polydithiodipropanesulfonate, sodium pyridine-3-sulfinate, and sodium piperazine-1,4-diethanesulfonate, and optionally one or more of sodium fluorosulfonate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium methanesulfonate, and sodium methylsulfate.

4. The non-aqueous electrolyte solution according to any one of claims 1 to 3, wherein the concentration of the sodium salt having a sulfonic acid group in the non-aqueous electrolyte solution is within a range of 0.0005 to 1 mol / L, and optionally within a range of 0.01 to 0.3 mol / L.

5. 5. The nonaqueous electrolyte solution according to claim 1, wherein the sodium salt having an oxalic acid group comprises one or more of sodium oxalate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetrafluoro(oxalato)phosphate, and sodium difluorobis(oxalato)phosphate, and optionally comprises one or more of sodium oxalate, sodium bis(oxalato)borate, sodium difluoro(oxalato)borate, sodium tetrafluoro(oxalato)phosphate, and sodium difluorobis(oxalato)phosphate.

6. The non-aqueous electrolyte solution according to any one of claims 1 to 5, wherein the concentration of the sodium salt having an oxalic acid group in the non-aqueous electrolyte solution is in the range of 0.0005 to 0.1 mol / L, optionally in the range of 0.006 to 0.08 mol / L, and further optionally in the range of 0.01 to 0.02 mol / L.

7. 7. The nonaqueous electrolyte solution according to claim 1, wherein the sodium salt having a phosphate group comprises one or more of sodium difluorophosphate, sodium monofluorophosphate, sodium trimetaphosphate, sodium hexametaphosphate, sodium hydroxyethylidene diphosphonate, disodium clodronate, sodium olpadronate, sodium diethylenetriaminepentamethylenephosphonate, sodium tripolyphosphate, and disodium phenylphosphate, and optionally comprises one or more of sodium difluorophosphate and sodium fluorophosphate.

8. The non-aqueous electrolyte solution according to any one of claims 1 to 7, characterized in that the concentration of the sodium salt having a phosphate group in the non-aqueous electrolyte solution is in the range of 0.0005 to 0.12 mol / L, optionally in the range of 0.01 to 0.05 mol / L, and more optionally in the range of 0.01 to 0.03 mol / L.

9. The nonaqueous electrolyte solution according to any one of claims 1 to 8, wherein the sodium salt having a boric acid group comprises one or more of sodium tetrafluoroborate, sodium metaborate, sodium tetraphenylborate, and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, optionally one or more of sodium tetrafluoroborate, sodium metaborate, and sodium tetraphenylborate, and further optionally one or more of sodium tetrafluoroborate and sodium metaborate.

10. The non-aqueous electrolyte solution according to any one of claims 1 to 9, wherein the concentration of the sodium salt having a boric acid group in the non-aqueous electrolyte solution is within a range of 0.0005 to 0.05 mol / L, and optionally within a range of 0.01 to 0.04 mol / L.

11. 11. The non-aqueous electrolyte solution according to claim 1, wherein, when sodium hexafluorophosphate is used in combination with at least one of sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate in the first sodium salt, the concentration of the sodium salt other than sodium hexafluorophosphate in the non-aqueous electrolyte solution is 0.001 mol / L or more, optionally 0.01 mol / L or more, further optionally 0.03 mol / L or more, and 1 mol / L or less, optionally 0.5 mol / L or less.

12. 12. The nonaqueous electrolyte solution according to claim 1, wherein the second sodium salt includes a sodium salt having a sulfonic acid group, and further includes one or more of a sodium salt having an oxalic acid group, a sodium salt having a phosphate group, and a sodium salt having a boric acid group.

13. 13. The nonaqueous electrolyte solution according to claim 1, wherein the second sodium salt comprises a sodium salt having a sulfonic acid group and a sodium salt having an oxalic acid group, and optionally, the molar ratio of the sodium salt having a sulfonic acid group to the sodium salt having an oxalic acid group is 0.03 / 1 to 70 / 1, and optionally, 0.5 / 1 to 20 / 1.

14. 14. The nonaqueous electrolyte solution according to claim 1, wherein the nonaqueous electrolyte solution contains a cyclic carbonate, and the mass concentration ratio of the cyclic carbonate in the nonaqueous electrolyte solution is 10% or more, and optionally 15% or more and 60% or less.

15. 15. The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous electrolyte solution contains a chain carbonate and a chain carboxylic acid ester, and the mass percentage of the sum of the chain carbonate and the chain carboxylic acid ester in the non-aqueous electrolyte solution is 40% or more, optionally 50% or more, more optionally 60% or more, and 90% or less, optionally 85% or less, and further optionally 80% or less.

16. 16. The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous electrolyte solution comprises at least one cyclic carbonate and at least one chain ester, and the mass percentage of the at least one cyclic carbonate to the at least one chain ester is 0.1:1 or more and 1.5:1 or less, optionally 1:1 or less, and further optionally between 0.2:1 and 1:

1.

17. 17. The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous electrolyte solution contains one or more of a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate and an ether, a combination of a chain carbonate and a chain carboxylic acid ester, a combination of a chain carbonate and an ether, a combination of a chain carboxylic acid ester and an ether, a combination of a cyclic carbonate, a chain carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain carbonate and an ether, a combination of a cyclic carbonate, a chain carbonate and an ether, a combination of a cyclic carbonate, a chain carboxylic acid ester and an ether, or a combination of a chain carbonate, a chain carboxylic acid ester and an ether.

18. 18. The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous solvent in the non-aqueous electrolyte solution contains one or more of propylene carbonate, ethyl methyl carbonate, ethyl acetate, diethyl carbonate, methyl propionate, ethyl propionate, diethylene glycol dimethyl ether, and fluoroethylene carbonate.

19. 19. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte contains one or more of an acid anhydride-based additive, a fluorine-containing organic additive, a nitrile-based additive, a silicone-based additive, an aldehyde-based additive, a sulfur-containing additive, a lithium salt-based additive, and a potassium salt-based additive, and optionally the total mass percentage of these additives in the non-aqueous electrolyte is 0.001% or more, optionally 0.2% or more and 5% or less, optionally 4% or less.

20. A sodium ion battery comprising a positive electrode plate, a negative electrode plate, and the nonaqueous electrolyte solution according to any one of claims 1 to 19.

21. 21. A power consuming device comprising the nonaqueous electrolyte solution according to any one of claims 1 to 19 or the sodium ion battery according to claim 20.

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