Secondary battery electrolyte, secondary battery, battery module, battery pack, and power consumption device

Abstract

The present application provides a secondary battery electrolyte comprising an electrolyte salt, a solvent, and a polyether, which can reduce high-temperature gas generation in secondary batteries and improve the safety performance of the batteries.

Description

[Technical Field]

[0001] The present application relates to the technical field of secondary batteries, and in particular to secondary battery electrolytes, secondary batteries, battery modules, battery packs, and power consuming devices. [Background technology]

[0002] As society develops, various problems, including energy shortages and environmental pollution, become increasingly prominent. To achieve the social goal of sustainable development, researchers have gradually turned their attention to secondary batteries. Although secondary batteries are the most suitable energy storage systems for portable electronic products and electric vehicles, their performance significantly deteriorates in high-temperature environments, posing serious safety risks.

[0003] The electrolyte serves as a medium for transferring secondary ions between the positive and negative electrodes, and its performance directly affects the high-temperature performance of secondary batteries. Conventional electrolytes are prone to decomposition in high-temperature environments and to react with the negative electrode, resulting in serious gas generation. Therefore, developing an electrolyte with high stability at high temperatures to improve the high-temperature performance of batteries is an urgent issue that must be addressed by those skilled in the art. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and aims to provide an electrolyte solution that reduces the high-temperature gas generation phenomenon in batteries and broadens the application environment of batteries.

[0005] A first aspect of the present application provides a secondary battery electrolyte solution comprising an electrolyte salt, a solvent, and a polyether.

[0006] Polyether provides a polymer skeleton in the electrolyte, reduces the kinetic activity of the solvent molecules in the electrolyte, reduces direct contact between the positive and negative electrodes and the solvent, suppresses gas generation during high-temperature cycling of the secondary battery, and improves the safety performance of the battery at high temperatures.

[0007] In some embodiments, the electrolyte solution contains lithium ions, and the mass content of the lithium ions is 0.05% to 0.46%, based on the total mass of the electrolyte solution.

[0008] With an appropriate mass content of lithium ions, the normal temperature cycle performance and the high temperature cycle performance of the battery can be further improved through synergistic action, and the high temperature gas generation phenomenon of the battery can be reduced.

[0009] In any embodiment, based on the total weight of the electrolyte, the weight content of the polyether is 10% to 70%.

[0010] With an appropriate mass content of polyether, the electrolyte has a suitable viscosity, and the battery has excellent initial coulombic efficiency, room temperature cycle performance, high temperature performance, and low high-temperature gas generation, which contributes to expanding the operating temperature range of the battery.

[0011] In an optional embodiment, the polyether is formed by in situ polymerization of cyclic ether compounds in an electrolyte solution induced by a Lewis acid.

[0012] By producing polyether through in-situ polymerization in the electrolyte, the polyether can be uniformly distributed in the electrolyte, effectively reducing the high-temperature gas generation phenomenon in the battery.

[0013] In any embodiment, the Lewis acid is derived from an additive in the electrolyte, and the additive comprises one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate.

[0014] Under certain conditions, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate can generate Lewis acids that induce in situ polymerization of cyclic ether compounds to generate polyethers. At the same time, the above additives provide a certain amount of lithium ions, and through their synergistic effect, can improve the room temperature cycle performance and high temperature cycle performance of the battery and reduce the high temperature gas generation phenomenon of the battery.

[0015] In an optional embodiment, the Lewis acid is derived from an additive in the electrolyte, and the additive comprises one or two selected from lithium hexafluorophosphate and lithium tetrafluoroborate.

[0016] Appropriate additives can improve the normal temperature cycling performance and high temperature cycling performance of the battery and reduce the high temperature gas generation phenomenon of the battery.

[0017] In any embodiment, based on the total mass of the electrolyte, the mass content of the added additive is 1% to 10%.

[0018] With an appropriate mass content of the additive, the electrolyte has suitable viscosity and good ionic conductivity, and the battery has excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, which contributes to further expanding the operating temperature range of the battery.

[0019] In any embodiment, based on the total mass of the electrolyte, the mass content of the added additive is 2% to 6%.

[0020] The additive with a suitable mass content can improve the initial coulombic efficiency, normal temperature cycle performance and high temperature cycle performance of the battery, and reduce the high temperature gas generation phenomenon of the battery.

[0021] In any embodiment, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0022] The ring-opening polymerization conditions of the above cyclic ether compounds are mild, which is conducive to the occurrence of in situ polymerization reaction and the formation of polyether with an appropriate mass content, resulting in an electrolyte with suitable viscosity and good ionic conductivity, and a battery with excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, which contributes to further expanding the operating temperature range of the battery.

[0023] In any embodiment, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0024] In an optional embodiment, the solvent comprises a chain ether compound.

[0025] The chain ether compounds provide the electrolyte with suitable viscosity and excellent ionic conductivity. At the same time, the chain ether compounds and polyethers have the same ether bond, which can improve the compatibility of the electrolyte system. The chain ether compounds as a solvent can further improve the uniformity of the polyether distribution in the electrolyte, improve the initial coulombic efficiency, room temperature cycle performance, and high temperature cycle performance of the battery, reduce the amount of high-temperature gas generated by the battery, improve the electrochemical performance and safety performance of the battery, and extend the operating temperature of the battery.

[0026] In any embodiment, the solvent comprises one or more selected from ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether.

[0027] In any embodiment, the volume content of the cyclic ether compound added is 1 / 5 to 5 based on the total volume of the solvent in the electrolytic solution.

[0028] The appropriate volume content of the cyclic ether compound allows the electrolyte to contain an appropriate mass content of polyether, which can ensure that the electrolyte has suitable viscosity and excellent ionic conductivity, reduce the high-temperature gas generation phenomenon of the battery, and help ensure that the battery has excellent initial coulombic efficiency, room temperature cycling performance, and high-temperature cycling performance.

[0029] In any embodiment, the volume content of the cyclic ether compound added is 1 / 3 to 3 based on the total volume of the solvent in the electrolyte solution.

[0030] The appropriate volume content of the cyclic ether compound allows the electrolyte to contain an appropriate mass content of polyether, which can ensure that the electrolyte has suitable viscosity and excellent ionic conductivity, reduce the high-temperature gas generation phenomenon of the battery, and help ensure that the battery has excellent initial coulombic efficiency, room temperature cycling performance, and high-temperature cycling performance.

[0031] In any embodiment, the electrolyte salt comprises at least one of a first sodium salt and a second sodium salt, wherein the first sodium salt comprises one or more selected from sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate, and the anion structure of the second sodium salt comprises at least one of the structures shown in Formula I and Formula II: [ka] R1, R2, and R3 are each independently fluorine or C1 to C6 fluoroalkyl.

[0032] By including the first sodium salt or the second sodium salt in the electrolyte, the battery has low high temperature gas production.

[0033] In any embodiment, the mass content of the first sodium salt in the electrolyte solution is 2% to 40%, based on the total mass of the electrolyte solution.

[0034] The appropriate mass content of the first sodium salt can ensure the reversible deposition and desorption of metal ions on the negative electrode, which is particularly applicable to negative electrode-free sodium batteries. At the same time, the appropriate mass content of the first sodium salt can ensure that the electrolyte has suitable viscosity and excellent ionic conductivity, thereby improving the initial coulombic efficiency and room temperature cycling performance of the battery and reducing the high-temperature gas generation phenomenon of the battery.

[0035] In any embodiment, the second sodium salt comprises one or more of sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide.

[0036] The anion in the second sodium salt can be reduced on the surface of the negative electrode to produce a sulfur-containing compound and a nitrogen-containing compound, which can effectively passivate the negative electrode, reduce the occurrence of side reactions between the negative electrode and the electrolyte, improve the high-temperature cycle performance of the battery, reduce the high-temperature gas generation phenomenon of the battery, and improve the electrochemical performance and safety performance of the battery.

[0037] In any embodiment, the mass content of the second sodium salt in the electrolyte solution is 1% to 10%, based on the total mass of the electrolyte solution.

[0038] The appropriate mass content of the second sodium salt forms a structurally stable and uniformly distributed SEI, which contributes to improving the high-temperature cycle performance of the battery and reducing the high-temperature gas generation phenomenon of the battery.

[0039] In any embodiment, the viscosity of the electrolyte at 25° C. is less than 1300 mPa·s.

[0040] The appropriate viscosity of the electrolyte not only ensures the excellent ionic conductivity of the electrolyte, but also ensures that the electrolyte has good wettability with the electrodes, so that the battery has both excellent electrochemical performance and safety performance.

[0041] A second aspect of the present application is adding an additive which is a Lewis acid or a Lewis acid precursor and a cyclic ether compound to a composition which includes an electrolyte salt and a solvent; and polymerizing in situ for at least 24 hours to obtain a secondary battery electrolyte.

[0042] The cyclic ether compound is polymerized in situ using a Lewis acid or a Lewis acid generated from a Lewis acid precursor to produce a polyether that is uniformly distributed in the electrolyte. The polyether provides a polymer backbone in the electrolyte, reduces the molecular dynamics activity of the solvent in the electrolyte, reduces direct contact between the positive and negative electrodes and the solvent, suppresses gas generation during high-temperature cycling in secondary batteries, improves the high-temperature gas generation phenomenon of the battery, and enhances the safety performance of the battery at high temperatures.

[0043] In an optional embodiment, the additive comprises one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate.

[0044] Under certain conditions, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate can generate Lewis acids to induce the polymerization of cyclic ether compounds, while providing a certain amount of lithium ions, improving the room temperature cycle performance and high temperature cycle performance of the battery and reducing the high temperature gas generation phenomenon of the battery.

[0045] In an optional embodiment, the additive comprises one or two selected from lithium hexafluorophosphate, lithium tetrafluoroborate.

[0046] Appropriate additives can improve the normal temperature cycling performance and high temperature cycling performance of the battery and reduce the high temperature gas generation phenomenon of the battery.

[0047] In any embodiment, based on the total mass of the electrolyte, the mass content of the added additive is 1% to 10%.

[0048] With an appropriate mass content of additives, the electrolyte has appropriate viscosity and good ionic conductivity, the battery has excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, the battery has excellent electrochemical performance and safety performance, and the operating temperature of the battery can be expanded.

[0049] In any embodiment, based on the total mass of the electrolyte, the mass content of the added additive is 2% to 6%.

[0050] The additive with a suitable mass content can improve the initial coulombic efficiency, normal temperature cycle performance and high temperature cycle performance of the battery, and reduce the high temperature gas generation phenomenon of the battery.

[0051] In any embodiment, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0052] The use of suitable cyclic ether compounds allows the polymerization conditions for the ring-opening reaction to be mild, contributing to the occurrence of in-situ polymerization, resulting in the production of polyethers with suitable mass content, the electrolyte having suitable viscosity and good ionic conductivity, the battery having excellent initial coulombic efficiency, room temperature cycling performance, high temperature cycling performance, and low high-temperature gas generation, the battery having excellent electrochemical performance and safety performance, and the battery operating temperature range being extended.

[0053] In any embodiment, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0054] In any embodiment, the volume content of the cyclic ether compound added is 1 / 5 to 5 based on the total volume of the solvent in the electrolytic solution.

[0055] The appropriate volume content of the cyclic ether compound allows the electrolyte to contain an appropriate mass content of polyether, which simultaneously ensures that the electrolyte has appropriate viscosity and excellent ionic conductivity, reduces the high-temperature gas generation phenomenon of the battery, and ensures that the battery has excellent initial coulomb efficiency, room temperature cycle performance, and high-temperature cycle performance.

[0056] In any embodiment, the volume content of the cyclic ether compound added is 1 / 3 to 3 based on the total volume of the solvent in the electrolyte solution.

[0057] The appropriate volume content of the cyclic ether compound allows the electrolyte to contain an appropriate mass content of polyether, which can ensure that the electrolyte has excellent viscosity and ionic conductivity, further reduce the high-temperature gas generation phenomenon of the battery, and also ensure that the battery has excellent initial coulomb efficiency, room temperature cycling performance, and high-temperature cycling performance.

[0058] A third aspect of the present application provides a secondary battery comprising an electrolytic solution, the electrolytic solution comprising the electrolytic solution of the first aspect or the electrolytic solution produced by the production method of the second aspect.

[0059] In any embodiment, the secondary battery includes at least one of a sodium ion battery and a lithium ion battery.

[0060] In any embodiment, the secondary battery is a negative electrode-free sodium metal battery.

[0061] In anode-free sodium batteries, the metallic sodium in the anode is generated during subsequent cycles, and because the sodium-ion battery has no voltage before the first charge, the sodium-ion battery can be stored for a long period of time without self-discharge, and no current is generated even if the battery is short-circuited, further improving the safety of the battery.

[0062] In any embodiment, the secondary battery includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and an undercoat layer formed on at least a portion of the surface of the negative electrode current collector.

[0063] The conductive undercoat layer has the feature of low metal nucleation potential, which can effectively improve the metal deposition / dissolution performance, and at the same time, solution This improves the large volume change that occurs in the cell during the process, making the cell structure more stable, improving the high-temperature cycle performance of the battery, and reducing the high-temperature gas generation phenomenon of the battery.

[0064] In an optional embodiment, the primer layer is a conductive carbon coating.

[0065] The conductive carbon coating can effectively reduce the overpotential caused by metal deposition, inhibit the formation of metal dendrites, improve the room temperature cycle performance and high temperature cycle performance of the battery, and reduce the high temperature gas generation phenomenon of the battery.

[0066] In any embodiment, the areal density of the conductive carbon coating is between 5 and 50 g / m 2 is.

[0067] A suitable range of surface density of the undercoat layer can optimize the metal deposition effect, improve the high-temperature cycle performance and room-temperature cycle performance of the battery, and reduce the high-temperature gas generation phenomenon of the battery, while also improving the energy density of the battery and meeting the usage needs of the battery.

[0068] A fourth aspect of the present application is a battery module including the secondary battery of the third aspect.

[0069] A fifth aspect of the present application provides a battery pack including at least one of the secondary battery of the third aspect and the battery module of the fourth aspect.

[0070] A sixth aspect of the present application provides a power consumption device including at least one of the secondary battery of the third aspect, the battery module of the fourth aspect, and the battery pack of the fifth aspect. [Brief explanation of the drawings]

[0071] [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 shown in FIG. 4 according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of a power consuming device that uses a secondary battery as a power source according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0072] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the present application's positive electrode active material and manufacturing method thereof, positive electrode plate, secondary battery, battery module, battery pack, and electric device will be described in detail. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate easy understanding by those skilled in the art. Furthermore, 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 scope of the claims.

[0073] The "ranges" disclosed herein 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 given range. Such defined ranges may be inclusive or exclusive of both the endpoints and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a given parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are recited as minimum range values ​​and 3, 4, and 5 are recited as maximum range values, then the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. Unless otherwise specified herein, a numerical range "a to b" represents a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" are listed herein, and "0 to 5" is simply shorthand for combinations of these numbers. Note that describing a parameter as an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0074] Unless otherwise stated, all embodiments and alternative embodiments in the present application can be combined with each other to form new technical solutions.

[0075] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0076] Unless otherwise specified, all steps herein may be performed in sequence or randomly, preferably in sequence. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, when it is stated that the method may further include step (c), it means that step (c) can be added to the method in any order; for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b).

[0077] Unless otherwise specified, the terms "comprise" and "comprises" used herein may be open-ended or closed-ended. For example, the terms "comprise" and "comprises" may indicate that the compound may further include or include other components not listed, or may include or include only the listed components.

[0078] Unless otherwise stated, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0079] When a secondary battery is used or stored at high temperatures, the reaction between the positive and negative electrodes and the electrolyte becomes more active, significantly increasing the amount of heat released from the reaction and generating a large amount of gas, which makes the battery prone to volume expansion and, in serious cases, may even cause a short circuit inside the battery, seriously affecting the safety performance of the battery.

[0080] [Electrolyte] Based on this, the present application provides an electrolyte solution comprising an electrolyte salt, a solvent, and a polyether.

[0081] As used herein, the term "electrolyte" refers to a composition that establishes an ionic conduction channel between the positive and negative electrodes within a battery while simultaneously blocking electronic conduction, and includes a solvent and an electrolyte salt. The electrolyte may be in any form, such as a low-viscosity, flowable liquid or a high-viscosity gel.

[0082] As used herein, the term "electrolyte salt" refers to a compound that consists of metal cations and anions and that is itself capable of conducting electricity in aqueous solution or in the molten state.

[0083] As used herein, the term "polyether" refers to a polymer containing an ether (-OCO-) segment in the polymer backbone, including polyalkylene oxide, aromatic polyether, epoxy resin, acetal resin, polyethersulfone, and polyetherimide. The degree of polymerization of the polyether is not limited herein, and it is understood that the polyether may be a high polymer or an oligomer.

[0084] In some embodiments, the polyether is a polyalkylene oxide.

[0085] As used herein, the term "polyalkylene oxide" refers to a polymer obtained by ring-opening homopolymerization or copolymerization of alkylene oxide under the action of a catalyst. Examples of polyalkylene oxide include polyethylene oxide, polypropylene oxide, polytetrahydrofuran, polytetrahydropyran, poly-1,3-dioxolane, poly-1,4-dioxane, and ethylene oxide-propylene oxide copolymers.

[0086] The addition of polyether to the electrolyte provides a polymer skeleton, which can serve to bind the solvent molecules, thereby reducing the kinetic activity of the solvent molecules in the electrolyte, reducing direct contact between the positive and negative electrodes and the solvent, reducing the possibility of chemical reaction between the positive and negative electrodes and the solvent, suppressing gas generation during high-temperature cycling in the secondary battery, improving the high-temperature gas generation performance of the secondary battery, and enhancing the safety performance of the secondary battery at high temperatures.

[0087] In some embodiments, the electrolyte solution includes lithium ions, and the mass content of the lithium ions is 0.05% to 0.46% based on the total mass of the electrolyte solution. In some embodiments, the mass content of the lithium ions is optionally any one of 0.05% to 0.1%, 0.05% to 0.2%, 0.05% to 0.3%, 0.05% to 0.4%, 0.4% to 0.46%, 0.1% to 0.2%, 0.1% to 0.3%, 0.1% to 0.4%, 0.1% to 0.46%, 0.2% to 0.3%, 0.2% to 0.4%, 0.2% to 0.46%, 0.3% to 0.4%, and 0.3% to 0.46% based on the total mass of the electrolyte solution.

[0088] The appropriate mass content of lithium ions can improve the normal temperature cycle performance and high temperature cycle performance of the battery and reduce the high temperature gas generation phenomenon of the battery.

[0089] Taking a sodium metal battery as an example, the introduction of lithium ions can further effectively inhibit the growth of sodium dendrites during the sodium metal deposition process. During the charging process of a sodium metal battery, an electrochemical reaction occurs at the negative electrode in which sodium ions gain electrons and are reduced to sodium metal. In the initial stage of the reaction, sodium metal deposits unevenly on the surface of the current collector, forming dendrites, the tips of which have a high negative charge density due to the tip effect. Both lithium ions and sodium ions are positive monovalent cations and carry a single positive charge. However, due to their smaller radius, lithium ions have a higher positive charge density and are distributed to the tips of dendrites before sodium ions. This effectively reduces the continued deposition of sodium ions at the tips of sodium dendrites, inhibits the growth of sodium dendrites, and significantly improves the cycle performance of the sodium metal battery.

[0090] In some embodiments, the weight content of the polyether is 10% to 70% based on the total weight of the electrolyte, or optionally any one of 10% to 20%, 10% to 30%, 10% to 40%, 10% to 50%, 10% to 60%, 10% to 70%, 20% to 30%, 20% to 40%, 20% to 50%, 20% to 60%, 20% to 70%, 30% to 40%, 30% to 50%, 30% to 60%, 30% to 70%, 40% to 50%, 40% to 60%, 40% to 70%, 50% to 60%, 50% to 70%, and 60% to 70% based on the total weight of the electrolyte.

[0091] With an appropriate mass content of polyether, the electrolyte has appropriate viscosity and excellent ionic conductivity, and the battery has excellent initial coulombic efficiency, room temperature cycle performance and high temperature performance, and the battery has low high-temperature gas generation, and the operating temperature of the battery can be expanded.

[0092] In some embodiments, the polyether is formed by in situ polymerization of cyclic ether compounds in an electrolyte solution induced by a Lewis acid.

[0093] As used herein, the term "cyclic ether compound" refers to a product in which hydrogen in a hydroxy group of an alcohol or phenol is replaced with a hydrocarbon group, and the carbon and oxygen atoms in the product form a cyclic structure. Examples of cyclic ether compounds include, but are not limited to, ethylene oxide, propylene oxide, epoxybutane, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,4-dioxane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, and methyltetrahydrofuran.

[0094] As used herein, the term "Lewis acid" refers to a molecule, ion, or atomic group that can accept an incoming electron pair, i.e., an electron pair acceptor. Lewis acids mainly include metal cations in coordination compounds, and some molecules and ions have an eight-electron structure at the center, but can expand their coordination sphere to accept more electron pairs; some molecules and ions have an eight-electron structure at the center, but can accept more electron pairs by rearranging valence shell electrons; and some closed-shell molecules can accept incoming electron pairs through their antibonding molecular orbitals.

[0095] In some embodiments, the Lewis acid may be a cation or metal ion, such as a sodium ion, an alkyl cation, or a nitro cation.

[0096] In some embodiments, the Lewis acid may be an electron-deficient compound such as boron trifluoride, phosphorus pentafluoride, aluminum trichloride, sulfur trioxide, and the like.

[0097] As used herein, the term "in situ polymerization" refers to a polymer produced by polymerization reaction of reactive monomers in an electrolyte solution.

[0098] In some embodiments, the Lewis acid is added directly to the electrolyte in the form of an additive, hi some embodiments, the Lewis acid is produced by decomposition of an additive in the electrolyte.

[0099] Polyethers produced by in situ polymerization can effectively solve the problem of low solubility of polymers in electrolytes. In situ polymerization allows the polyether to be distributed uniformly in the electrolyte, increasing its direct interaction with the solvent molecules in the electrolyte and further reducing direct contact between the solvent molecules in the electrolyte and the positive and negative electrodes, effectively mitigating the high-temperature gas generation phenomenon in batteries. Furthermore, in situ polymerization can occur in situ within the secondary battery system after the electrolyte is injected, effectively avoiding the processing difficulties that arise when the addition of polyether makes the electrolyte too viscous, making battery assembly difficult. This allows for optimized battery performance and increased production efficiency without changing the original battery production process.

[0100] In some embodiments, the Lewis acid is derived from an additive in the electrolyte, and the additive comprises one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate.

[0101] As used herein, the term "additive" refers to a minor component of the electrolyte solution, which may be a gas, liquid, or solid. Conceptually, the distinction between additives, solvents, and electrolyte salts lies solely in their different contents in the electrolyte solution.

[0102] Under certain conditions, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate decompose to produce Lewis acids that induce the polymerization of cyclic ether compounds to produce polyethers. At the same time, the lithium salts can provide a certain amount of lithium ions, improving the room temperature cycle performance and high temperature cycle performance of the battery and reducing the high temperature gas generation phenomenon of the battery.

[0103] In some embodiments, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate are thermally decomposed at certain temperatures to produce Lewis acids.

[0104] In some embodiments, lithium hexafluorophosphate is thermally decomposed and the products include the Lewis acid phosphorus pentafluoride and lithium fluoride.

[0105] In some embodiments, lithium tetrafluoroborate is thermally decomposed and the products include the Lewis acid boron trifluoride and lithium fluoride.

[0106] In some embodiments, lithium perchlorate is thermally decomposed and the products include lithium Lewis acid chloride.

[0107] In some embodiments, lithium difluoro(oxalato)borate is thermally decomposed and the products include the Lewis acid boron trifluoride and lithium fluoride.

[0108] In some embodiments, the Lewis acid is derived from an additive in the electrolyte, and the additive comprises one or two selected from lithium hexafluorophosphate and lithium tetrafluoroborate.

[0109] Lithium hexafluorophosphate and lithium tetrafluoroborate are easily thermally decomposed under mild conditions, which facilitates in-situ polymerization in the electrolyte system and ensures the reliability of the reaction. Appropriate additives can improve the room temperature cycle performance and high temperature cycle performance of the battery and reduce the amount of gas generation in the high temperature environment of the battery.

[0110] In some embodiments, the mass content of the added additive is 1% to 10% based on the total mass of the electrolyte. In some embodiments, the mass content of the added additive is optionally 1% to 2%, 1% to 3%, 1% to 4%, 1% to 5%, 1% to 6%, 1% to 7%, 1% to 8%, 1% to 9%, 1% to 10%, 2% to 3%, 2% to 4%, 2% to 5%, 2% to 6%, 2% to 7%, 2% to 8%, 2% to 9%, 2% to 10%, 3% to 4%, 3% to 5%, 3% to 6%, 3% to 7%, 3% to 8%, 3% to 9%, 3% to 10 ... Any one of the following: %~7%, 3%~8%, 3%~9%, 3%~10%, 4%~5%, 4%~6%, 4%~7%, 4%~8%, 4%~9%, 4%~10%, 5%~6%, 5%~7%, 5%~8%, 5%~9%, 5%~10%, 6%~7%, 6%~8%, 6%~9%, 6%~10%, 7%~8%, 7%~9%, 7%~10%, 8%~9%, 8%~10%, 9%~10%.

[0111] With an appropriate mass content of additives, the electrolyte has suitable viscosity and good ionic conductivity, and the battery has excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, and the operating temperature of the battery can be further expanded.

[0112] In some embodiments, the mass content of the additives added is 2% to 6% based on the total mass of the electrolyte. In some embodiments, the mass content of the additives added is optionally 2% to 3% based on the total mass of the electrolyte. 、 Any one of the following: 2%-4%, 2%-5%, 2%-6%, 3%-4%, 3%-5%, 3%-6%, 4%-5%, 4%-6%, 5%-6%.

[0113] The additive with a suitable mass content can improve the initial coulombic efficiency, normal temperature cycle performance and high temperature cycle performance of the battery, and reduce the high temperature gas generation phenomenon of the battery.

[0114] In some embodiments, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0115] The addition of a suitable cyclic ether compound facilitates ring-opening polymerization, contributing to the in situ polymerization reaction in the electrolyte to produce a suitable mass content of polyether, which allows the electrolyte to have suitable viscosity and good ionic conductivity, and the battery to have excellent initial coulombic efficiency, room temperature cycling performance, high temperature cycling performance, and low high-temperature gas generation, thereby further expanding the operating temperature range of the battery.

[0116] In some embodiments, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0117] The cyclic polymers are easily induced by Lewis acids to undergo ring-opening reactions at room temperature, resulting in highly reliable in-situ polymerization. For batteries, the reactants can be added during the injection process, and the in-situ polymerization can be completed before the batteries are shipped, eliminating the need for additional time and processes and further improving production efficiency.

[0118] In some embodiments, the solvent comprises a chain ether compound.

[0119] As used herein, the term "chain ether compound" refers to a product in which the hydrogen in the hydroxy group of an alcohol or phenol is replaced with a hydrocarbon group, and the carbon and oxygen atoms in the product are interconnected to form a chain.

[0120] The chain ether compounds provide the electrolyte with suitable viscosity and excellent ionic conductivity. At the same time, the chain ether compounds and polyethers have the same ether bond, which improves the compatibility of the electrolyte system and allows the polyether to be uniformly distributed in the electrolyte, thereby improving the initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the battery, reducing the high-temperature gas generation phenomenon of the battery, improving the electrochemical performance and safety performance of the battery, and contributing to expanding the operating temperature of the battery.

[0121] The molecules of chain ether compounds can establish a stable electrode / electrolyte interface on the surface of the negative electrode of a sodium metal battery (including the negative electrode of a negative-electrode-free battery), a negative electrode made of a carbon material, and a negative electrode made of other non-carbon materials, forming a stable solid electrolyte interface (SEI), reducing electrochemical polarization and improving the initial coulombic efficiency and high-temperature cycle performance of the battery.

[0122] Taking a sodium metal battery as an example, ether solvents have high compatibility with alkali metal negative electrodes, and can effectively passivate sodium metal, forming a thin, uniform, and dense SEI film on the surface of the sodium metal, and further inhibiting the formation of sodium dendrites, preventing the SEI film from becoming thicker due to the growth and evolution of sodium dendrites, which would affect ion conduction.

[0123] As used herein, the term "anode-free battery" refers to a battery that employs a current collector as the anode during packaging. In anode-free batteries, metal ions are deposited on the current collector during charging to form a metallic anode.

[0124] In some embodiments, the solvent comprises one or more selected from ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether.

[0125] In some embodiments, based on the total volume of the solvent in the electrolyte, the volume content of the cyclic ether compound added is 1 / 5 to 5. In some embodiments, based on the total volume of the solvent in the electrolyte, the volume content of the cyclic ether compound added is optionally any one of 1 / 4 to 4, 2 / 7 to 3.5, 1 / 3 to 3, 2 / 5 to 2.5, 1 / 2 to 2, and 2 / 3 to 1.5.

[0126] The appropriate volume content of the cyclic ether compound ensures that the ring-opening reaction proceeds smoothly, and the electrolyte contains an appropriate mass content of polyether. At the same time, this ensures that the electrolyte has suitable viscosity and good ionic conductivity, reduces the high-temperature gas generation phenomenon of the battery, and ensures that the battery has good initial coulombic efficiency, room temperature cycle performance, and high temperature cycle performance.

[0127] In some embodiments, the volume content of the cyclic ether compound added, based on the total volume of the solvent in the electrolyte, is 1 / 3 to 3. In some embodiments, the volume content of the cyclic ether compound added, based on the total volume of the solvent in the electrolyte, is optionally any one of 1 / 3 to 3, 2 / 5 to 2.5, 1 / 2 to 2, and 2 / 3 to 1.5.

[0128] The appropriate volume content of the cyclic ether compound ensures that the ring-opening reaction proceeds smoothly, and the electrolyte contains an appropriate mass content of polyether, which in turn ensures that the electrolyte has suitable viscosity and good ionic conductivity, further reducing the high-temperature gas generation phenomenon of the battery, and ensuring that the battery has good initial coulombic efficiency, room temperature cycling performance, and high-temperature cycling performance.

[0129] In some embodiments, the electrolyte salt comprises at least one of a first sodium salt and a second sodium salt, wherein the first sodium salt comprises one or more selected from sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate, and the anion structure of the second sodium salt comprises at least one of the structures shown in Formula I and Formula II: [ka] R1, R2, and R3 are each independently fluorine or C1 to C6 fluoroalkyl.

[0130] As used herein, the term "C1-C6 fluoroalkyl" refers to an alkane having from 1 to 6 carbon atoms substituted with at least one fluorine.

[0131] In some embodiments, the second sodium salt comprises one or more selected from sodium fluorosulfonate, sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium (fluorosulfonyl)(trifluoromethanesulfonyl)imide.

[0132] In some embodiments, the second sodium salt comprises one or two selected from sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide.

[0133] The weak bonding force between the anions and sodium ions in the first sodium salt allows for rapid deposition and release of metal ions, contributing to improved dynamic performance of the battery. Particularly in anode-free batteries, the second sodium salt can effectively ensure the battery's capacity and cycle performance. The second sodium salt can optimize the deposition and release of metal ions, improving the cycle performance of secondary batteries. At the same time, appropriate concentrations of the first and second sodium salts ensure that the electrolyte has suitable viscosity and excellent ionic conductivity, improving the overall electrochemical performance of secondary batteries.

[0134] The strong bonding force between the anions and sodium ions in the second sodium salt makes it more likely to participate in the solvation structure of the electrolyte salt, and as metal ions accumulate, they come into contact with the surface of the anode and are easily reduced on the surface of the anode to form an SEI mainly composed of sulfides and nitrides, which greatly improves the structural stability and uniformity of the SEI on the surface of the secondary battery. The SEI containing a large amount of sulfides and nitrides is less likely to undergo secondary decomposition and regeneration, reducing metal consumption within the battery and improving the high-temperature cycle performance of the secondary battery. Meanwhile, the stable and uniformly distributed SEI reduces direct contact between the electrolyte and metal, thereby reducing side reactions between the electrolyte and metal, suppressing gas generation during high-temperature cycles in the secondary battery and improving the high-temperature gas generation phenomenon of the secondary battery.

[0135] In some embodiments, the electrolyte salt comprises a first sodium salt.

[0136] The inclusion of the first sodium salt in the electrolyte solution allows the battery to have excellent initial coulombic efficiency, room temperature cycling performance and high temperature cycling performance, and the battery to have low high temperature gas production.

[0137] In some embodiments, the electrolyte salt comprises a second sodium salt.

[0138] The inclusion of a second sodium salt in the electrolyte results in the battery having low high temperature gas production.

[0139] In some embodiments, the electrolyte salt comprises a first sodium salt and a second sodium salt.

[0140] The inclusion of the first sodium salt and the second sodium salt in the electrolyte solution ensures that the metal ions can be reversibly deposited and exfoliated, and also ensures that the SEI has a stable structure and is uniformly distributed, thereby improving the high-temperature cycle performance of the secondary battery and the high-temperature gas generation performance of the secondary battery.

[0141] In some embodiments, the mass content of the first sodium salt in the electrolyte solution is 2% to 40%, based on the total mass of the electrolyte solution, and optionally any one of 2% to 10%, 2% to 20%, 2% to 30%, 10% to 20%, 10% to 30%, 10% to 40%, 20% to 30%, 20% to 40%, and 30% to 40%, based on the total mass of the electrolyte solution.

[0142] The appropriate mass content of the first sodium salt ensures that the metal ions can be reversibly deposited and stripped, and at the same time, the electrolyte has suitable viscosity and excellent ionic conductivity, which can improve the initial coulombic efficiency and room temperature cycling performance of the battery, and reduce the high-temperature gas generation phenomenon of the battery.

[0143] In some embodiments, the mass content of the second sodium salt in the electrolyte is 1% to 10% based on the total mass of the electrolyte, and optionally any one of 1% to 2%, 1% to 4%, 1% to 6%, 1% to 8%, 1% to 10%, 2% to 4%, 2% to 6%, 2% to 8%, 2% to 10%, 4% to 6%, 6% to 8%, 6% to 10%, and 8% to 10% based on the total mass of the electrolyte.

[0144] The appropriate mass content of the second sodium salt contributes to the formation of a stable and uniformly distributed SEI. , electricIt can improve the high-temperature cycle performance of the battery and reduce the high-temperature gas generation phenomenon of the battery.

[0145] In some embodiments, the viscosity of the electrolyte at 25° C. is less than 1300 mPa·s. In some embodiments, the viscosity of the electrolyte at 25° C. is optionally 1.5 mPa·s to 200 mPa·s, 1.5 mPa·s to 400 mPa·s, 1.5 mPa·s to 600 mPa·s, 1.5 mPa·s to 800 mPa·s, 1.5 mPa·s to 1000 mPa·s, 1.5 mPa·s to 1200 mPa·s, or 200 mPa·s to 400 mPa·s. 、2 The range is any one of 00mPa·s to 600mPa·s, 200mPa·s to 800mPa·s, 200mPa·s to 1000mPa·s, 200mPa·s to 1300mPa·s, 400mPa·s to 600mPa·s, 400mPa·s to 800mPa·s, 400mPa·s to 1000mPa·s, 400mPa·s to 1300mPa·s, 600mPa·s to 800mPa·s, 600mPa·s to 1000mPa·s, 600mPa·s to 1300mPa·s, 800mPa·s to 1000mPa·s, and 800mPa·s to 1300mPa·s.

[0146] The viscosity of the electrolyte can be tested using any known means. For example, a rheometer is used to measure the viscosity of the electrolyte at 25°C.

[0147] An electrolyte with appropriate viscosity will ensure that the electrolyte has excellent ionic conductivity, and at the same time, the electrolyte has good wettability to the electrodes, ensuring good contact between the electrolyte and the electrodes, and enhancing the electrochemical performance of the battery.

[0148] In some embodiments, the electrolyte solution further includes a solvent other than the chain ether compound solvent. Non-limiting examples of the other solvent include at least one selected from vinylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0149] In some embodiments, the electrolyte may further include other additives that can selectively improve specific performance of the battery, such as an additive that improves the overcharge performance of the battery or an additive that improves the thermal stability of the electrolyte.

[0150] [Electrolyte solution manufacturing method] The present application further provides a method for producing a secondary battery electrolyte, the method including the steps of adding an additive that is a Lewis acid or a Lewis acid precursor and a cyclic ether compound to a composition including an electrolyte salt and a solvent, and polymerizing the additive in situ for at least 24 hours to obtain a secondary battery electrolyte.

[0151] As used herein, the term "Lewis acid precursor" may refer to a chemical substance capable of generating a Lewis acid under certain conditions, and the conditions that induce the Lewis acid precursor to generate a Lewis acid may be thermal decomposition, chemical reaction, or photoinitiation.

[0152] In some embodiments, the polymerization temperature is any one of 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, and 60°C.

[0153] In some embodiments, the polymerization time is any one of 24 hours, 36 hours, 48 ​​hours, 60 hours, and 72 hours.

[0154] The above-mentioned mild polymerization conditions and controllable reaction time make the in-situ polymerization low cost and highly efficient, which contributes to its industrial widespread use and application.

[0155] The Lewis acid or Lewis acid generated from the Lewis acid precursor is used to induce in situ polymerization of a cyclic ether compound to produce a uniformly distributed polyether. The resulting polyether can provide a polymer backbone and serve to bind solvent molecules, thereby reducing the kinetic activity of the solvent molecules in the electrolyte, reducing direct contact between the positive and negative electrodes and the solvent, reducing the possibility of chemical reaction between the positive and negative electrodes and the solvent, suppressing gas generation during high-temperature cycling in the secondary battery, improving the high-temperature gas generation performance of the secondary battery, and enhancing the high-temperature safety performance of the secondary battery.

[0156] In some embodiments, the additive comprises one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate.

[0157] Under certain conditions, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate decompose to produce Lewis acids that induce the polymerization of cyclic ether compounds to produce polyethers. At the same time, the lithium salts can provide a certain amount of lithium ions, improving the room temperature cycle performance and high temperature cycle performance of the battery and reducing the high temperature gas generation phenomenon of the battery.

[0158] In some embodiments, the Lewis acid is derived from an additive in the electrolyte, and the additive comprises one or two selected from lithium hexafluorophosphate and lithium tetrafluoroborate.

[0159] Lithium hexafluorophosphate and lithium tetrafluoroborate are prone to thermal decomposition, which makes in situ polymerization more likely to occur, ensuring the reliability of the reaction.

[0160] Appropriate additives can improve the normal temperature cycling performance and high temperature cycling performance of the battery and reduce the high temperature gas generation phenomenon of the battery.

[0161] In some embodiments, the mass content of the added additive is 1% to 10% based on the total mass of the electrolyte. In some embodiments, the mass content of the added additive is optionally 1% to 2%, 1% to 3%, 1% to 4%, 1% to 5%, 1% to 6%, 1% to 7%, 1% to 8%, 1% to 9%, 1% to 10%, 2% to 3%, 2% to 4%, 2% to 5%, 2% to 6%, 2% to 7%, 2% to 8%, 2% to 9%, 2% to 10%, 3% to 4%, 3% to 5%, 3% to 6%, 3% to 7%, 3% to 8%, 3% to 9%, 3% to 10 ... Any one of the following: %~7%, 3%~8%, 3%~9%, 3%~10%, 4%~5%, 4%~6%, 4%~7%, 4%~8%, 4%~9%, 4%~10%, 5%~6%, 5%~7%, 5%~8%, 5%~9%, 5%~10%, 6%~7%, 6%~8%, 6%~9%, 6%~10%, 7%~8%, 7%~9%, 7%~10%, 8%~9%, 8%~10%, 9%~10%.

[0162] With an appropriate mass content of additives, the electrolyte has suitable viscosity and good ionic conductivity, and the battery has excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, and the operating temperature of the battery can be further expanded.

[0163] In some embodiments, the mass content of the added additive is 2% to 6% based on the total mass of the electrolyte, or optionally any one of 2% to 3%, 2% to 4%, 2% to 5%, 2% to 6%, 3% to 4%, 3% to 5%, 3% to 6%, 4% to 5%, 4% to 6%, and 5% to 6% based on the total mass of the electrolyte.

[0164] The additive with a suitable mass content can improve the initial coulombic efficiency, normal temperature cycle performance and high temperature cycle performance of the battery, and reduce the high temperature gas generation phenomenon of the battery.

[0165] In some embodiments, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0166] The addition of a suitable cyclic ether compound facilitates ring-opening polymerization, contributing to the in situ polymerization reaction and producing a suitable mass content of polyether, which allows the electrolyte to have suitable viscosity and good ionic conductivity, and the battery to have excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, thereby further expanding the operating temperature range of the battery.

[0167] In some embodiments, the cyclic ether compound comprises one or more selected from 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

[0168] The cyclic polymers are susceptible to ring-opening reactions induced by Lewis acids at room temperature, resulting in highly reliable in-situ polymerization. The in-situ polymerization reaction can be completed during the packaging process, eliminating the need for additional time or processes, further improving production efficiency.

[0169] In some embodiments, based on the total volume of the solvent in the electrolyte, the volume content of the cyclic ether compound added is 1 / 5 to 5. In some embodiments, based on the total volume of the solvent in the electrolyte, the volume content of the cyclic ether compound added is optionally any one of 1 / 4 to 4, 2 / 7 to 3.5, 1 / 3 to 3, 2 / 5 to 2.5, 1 / 2 to 2, and 2 / 3 to 1.5.

[0170] The appropriate volume content of the cyclic ether compound can ensure the mass content of the polyether in the electrolyte, which allows the electrolyte to have appropriate viscosity and excellent ionic conductivity, reduces the high-temperature gas generation phenomenon of the battery, and ensures that the battery has excellent initial coulomb efficiency, room temperature cycling performance, and high-temperature cycling performance.

[0171] In some embodiments, the volume content of the cyclic ether compound added, based on the total volume of the solvent in the electrolyte, is 1 / 3 to 3. In some embodiments, the volume content of the cyclic ether compound added, based on the total volume of the solvent in the electrolyte, is optionally any one of 1 / 3 to 3, 2 / 5 to 2.5, 1 / 2 to 2, and 2 / 3 to 1.5.

[0172] The appropriate volume content of the cyclic ether compound can ensure the mass content of the polyether in the electrolyte, which allows the electrolyte to have appropriate viscosity and excellent ionic conductivity, reduces the high-temperature gas generation phenomenon of the battery, and ensures that the battery has excellent initial coulomb efficiency, room temperature cycling performance, and high-temperature cycling performance.

[0173] [Secondary battery] The present application further provides a secondary battery comprising an electrolyte solution, the electrolyte solution comprising the electrolyte solution according to any embodiment or the electrolyte solution produced by the production method according to any embodiment.

[0174] In some embodiments, the secondary battery includes at least one of a sodium ion battery and a lithium ion battery.

[0175] In some embodiments, the secondary battery is a negative electrode-free sodium metal battery.

[0176] As used herein, the term "anode-free sodium metal battery" refers to a sodium metal battery that employs a current collector as the anode during packaging, in which sodium ions are deposited on the current collector during charging to form a sodium metal anode.

[0177] In anode-free sodium metal batteries, the metallic sodium on the anode is generated during subsequent cycles, and because the sodium-ion battery has no voltage before the first charge, the sodium-ion battery can be stored for a long period of time without self-discharge, and no current is generated even if the battery is short-circuited, making it extremely safe. Because there is no anode active material on the surface of the anode current collector and only the anode current collector is used, this battery can achieve a higher energy density.

[0178] In some embodiments, the secondary battery includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and an undercoat layer formed on at least a portion of the surface of the negative electrode current collector.

[0179] The undercoat layer has the feature of low metal nucleation potential, which can effectively improve the metal deposition / dissolution performance, and at the same time, solution This improves the large volume change that occurs in the cell during the process, making the cell structure more stable, improving the high-temperature cycle performance of the battery, and reducing the high-temperature gas generation phenomenon of the battery.

[0180] In some embodiments, the negative electrode current collector used in the negative plate includes at least one of a metal foil current collector, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, and a carbon paper current collector. Because sodium ions do not form an alloy with aluminum and because cost and weight considerations are taken into account, an aluminum-based current collector is preferentially adopted for sodium-ion batteries. The aluminum-based current collector is any one of aluminum foil, aluminum alloy foil, and aluminum-based composite current collector. The aluminum-based composite current collector includes a polymer-based film and aluminum foil and / or aluminum alloy foil formed on both sides of the polymer-based film. Specifically, the aluminum-based composite current collector has a "sandwich" structure, with a polymer-based film located in the center and aluminum foils on both sides, or aluminum foils on both sides. Alternatively, an aluminum alloy foil may be provided on one side of a polymer base film and an aluminum alloy foil on the other side, and the polymer base film may be made of any one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly-p-phenylene terephthalamide, polypropylene-ethylene, polyformaldehyde, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate.

[0181] In some embodiments, the primer layer comprises a binder, and the binder comprises any one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene butadiene rubber, sodium alginate, lithium / sodium polyacrylate, polytetrafluoroethylene, polyimide, and polyurethane.

[0182] In some embodiments, the undercoat layer is a metal coating, the metal has a body-centered cubic structure, and the metal comprises any one of α-Fe, V, Nb, Cr, Mo, Ta, and W.

[0183] In some embodiments, the undercoat layer is an alloy coating, and the alloy comprises any one or more of the following metals: Au, Ag, Sn, Sb.

[0184] In some embodiments, the primer layer is a metal oxide coating, and the oxide comprises at least one of copper oxide, aluminum oxide.

[0185] In some embodiments, the primer layer is a conductive polymer coating, and the conductive polymer comprises any one of polyaniline, polythiophene, polypyrrole, and polyphenylacetylene.

[0186] In some embodiments, the primer layer is a conductive ceramic coating, and the conductive ceramic material comprises at least one of TiB2, TiC, and B4C3.

[0187] In some embodiments, the primer layer is a conductive carbon coating, and the conductive carbon comprises at least one of conductive carbon black, graphite, carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and fullerenes.

[0188] The conductive carbon coating can effectively reduce the overpotential caused by metal deposition, inhibit the formation of metal dendrites, improve the room temperature cycle performance and high temperature cycle performance of the battery, and reduce the high temperature gas generation phenomenon of the battery.

[0189] In some embodiments, the areal density of the conductive carbon coating is between 5 and 50 g / m 2 In some embodiments, the areal density of the conductive carbon coating is preferably 5 to 10 g / m 2 , 5~20g / m 2 , 5 to 30 g / m 2 , 5~40g / m 2 , 5~50g / m 2 , 10-20g / m 2 , 10~30g / m 2, 10~40g / m 2 , 10~50g / m 2 , 20-30g / m 2 , 20~40g / m 2 , 20~50g / m 2 , 30-40g / m 2 , 30~50g / m 2 , 40~50g / m 2 Any one of the following:

[0190] The appropriate range of surface density of the undercoat layer can optimize the metal deposition effect, improve the coulomb efficiency and cycle performance of the battery, and reduce the high-temperature gas generation phenomenon of the battery. At the same time, the appropriate range of surface density of the undercoat layer can improve the energy density of the battery and meet the usage needs of the battery.

[0191] [Positive electrode] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer formed on at least a portion of a surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, and the positive electrode active material can include at least one of a layered transition metal oxide, a polyanion-type compound, and a Prussian blue compound.

[0192] The transition metal in the layered transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Optionally, the layered transition metal oxide may be, for example, Na x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu; <x≦1である。

[0193] Polyanionic compounds include metal ions, transition metal ions, and tetrahedral (YO4) n-The compound may have an anionic unit, wherein the metal ion is optionally one of sodium ion, lithium ion, potassium ion, and zinc ion, the transition metal is optionally at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y is optionally at least one of P, S, and Si, and n is (YO4) n- represents the valence state of

[0194] The Prussian blue compound may be a compound having a sodium ion, a transition metal ion, and a cyanide ion (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound may be, for example, Na a Me b Me' c (CN)6, where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn; <a≦2、0<b<1、0<c<1である。

[0195] The positive electrode active material layer may further include a conductive agent to improve the conductive performance of the positive electrode, which may be one or more of Super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0196] The positive electrode active material layer may further include a binder to firmly bond the positive electrode active material and optional conductive agent to the positive electrode current collector, and the binder may optionally be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0197] The positive electrode current collector may be a conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate, or composite current collector. The conductive carbon material of the conductive carbon sheet may be one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate may each independently be at least one selected from copper, aluminum, nickel, and stainless steel. The composite current collector may be a composite current collector formed by combining a metal foil with a polymer-based film.

[0198] In some embodiments, a positive electrode plate can be manufactured by the following method. The components for manufacturing the positive electrode plate described above, such as the positive electrode active material, conductive agent, binder, and any other optional components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is applied to a positive electrode current collector, and after processes such as baking and cold pressing, a positive electrode plate can be obtained.

[0199] [Separator] In some embodiments, the sodium ion battery further includes a separator. The type of separator is not particularly limited in this application, and any separator with a known porous structure having good chemical stability and mechanical stability can be selected.

[0200] In some embodiments, the separator may be made of at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid fiber, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fiber. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers may be the same or different, and are not particularly limited.

[0201] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be wound or stacked to form an electrode assembly.

[0202] In some embodiments, the sodium-ion battery may include an outer casing, which may be used to package the electrode assembly and the electrolyte.

[0203] In some embodiments, the exterior of the sodium-ion battery may be a hard case, such as a hard plastic case, an aluminum case, or a steel case. The exterior of the sodium-ion battery may be a soft pack, such as a bag-type soft pack. The soft pack may be made of plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate.

[0204] In the present application, the shape of the sodium ion battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a sodium ion battery 5 having a rectangular structure as an example.

[0205] In some embodiments, referring to FIG. 2 , the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates surrounding the chamber to form a storage chamber. The case 51 may have an opening communicating with the storage chamber, and the cover plate 53 may cover the opening to seal the storage chamber. 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 storage chamber. The electrolyte permeates the electrode assembly 52. ​​The sodium-ion battery 5 may include one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific actual requirements.

[0206] In some embodiments, the sodium-ion batteries can be assembled into a battery module, and the number of sodium-ion batteries included in the battery module can 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.

[0207] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the plurality of sodium ion batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other form. Furthermore, the plurality of sodium ion batteries 5 may be fixed by fastening members.

[0208] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of sodium ion batteries 5 are accommodated in the accommodating space.

[0209] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0210] 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 provided in the battery box. The battery box may include an upper box 2 and a lower box 3, and the upper box 2 may cover the lower box 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.

[0211] The present application also provides a power consuming device including at least one of the sodium ion batteries, battery modules, or battery packs provided herein. The sodium ion battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, notebook computers, etc.), electric vehicles (e.g., rechargeable battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric cars, marine vehicles, satellites, energy storage systems, etc.

[0212] The power consumption device can be selected as a sodium ion battery, a battery module, or a battery pack according to the needs of its use.

[0213] 6 shows an example of a power consuming device, such as a rechargeable battery electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A battery pack or battery module can be employed to meet the high power and high energy density requirements of the sodium ion batteries of the power consuming device.

[0214] Another example of the device may be a mobile phone, tablet, laptop, etc. Such devices typically require light weight and thinness, and may employ a sodium-ion battery as a power source.

[0215] Example Examples of the present application are described below. The examples described below are illustrative and are intended merely to interpret the present application and should not be understood as limiting the present application. If specific techniques or conditions are not specified in the examples, they are performed according to the techniques or conditions described in the literature in the field or according to the product specifications. If the manufacturers of the reagents or instruments used are not specified, they are all conventional products that are commercially available.

[0216] 1. Manufacturing method Example Example 1 1) Electrolyte production In an argon-atmosphere glovebox with a moisture content of <10 ppm, the first sodium salt, sodium hexafluorophosphate, and the second sodium salt, sodium bis(fluorosulfonyl)imide, were added to ethylene glycol dimethyl ether solvent. After uniform stirring, the additives lithium hexafluorophosphate and 1,3-dioxolane were added. Based on the total weight of the electrolyte, the mass content of lithium hexafluorophosphate was 4%, the mass content of sodium bis(fluorosulfonyl)imide was 5%, and the mass content of sodium hexafluorophosphate was 15%. The electrolyte was polymerized in situ at room temperature (23-27°C) for 48 hours to obtain a secondary battery electrolyte.

[0217] 2) Manufacturing of positive electrode plates The positive electrode active material Na3V2(PO4)3, the binder polyvinylidene fluoride (PVDF), and the conductive carbon black (Super-P) were uniformly mixed in a mass ratio of 96%:2%:2% in N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. This slurry was then coated on the surface of aluminum foil using an extrusion coater according to the mass requirement per unit area of ​​the positive electrode active material, baked, and further pressed into a cold press to form a coated electrode plate with a density of 2.5 g / cm. 3 The final positive electrode plate was manufactured by compressing and cold pressing the design.

[0218] 3) Manufacturing of negative electrode plates Carbon nanotubes and sodium alginate were added to water and stirred to form a uniform slurry. The slurry was applied to the negative electrode current collector, baked, and cut to obtain a negative electrode plate with a negative electrode-free structure. The surface density of the undercoat layer was 10 g / m. 2 It was.

[0219] 4) Separator A polyethylene film (PE membrane) was used as the separator.

[0220] 5) Battery manufacturing The positive electrode plate, separator, and negative electrode plate were stacked in this order, a separator was interposed between the positive and negative electrode plates to function as an insulator, and the above-mentioned electrolyte was added to assemble into a button battery.

[0221] Examples 2 to 4 Examples 2 to 4 are similar to the battery manufacturing method of Example 1, except that lithium hexafluorophosphate is replaced with aluminum chloride, aluminum perchlorate, and lithium tetrafluoroborate, respectively, and the specific adjustment parameters are as shown in Table 1 below.

[0222] Examples 5 to 8 Examples 5 to 8 were similar to the battery manufacturing method of Example 1, but the mass content of lithium hexafluorophosphate in the electrolyte was adjusted, and the specific adjustment parameters were as shown in Table 1 below.

[0223] Examples 9 to 11 Examples 9 to 11 are similar to the battery manufacturing method of Example 1, except that 1,3-dioxolane is replaced with tetrahydropyran, tetrahydrofuran, and 1,4-dioxane, respectively, and the specific adjustment parameters are as shown in Table 1 below.

[0224] Example 12 Example 12 is similar to the battery manufacturing method of Example 1, except that ethylene glycol dimethyl ether is replaced with dimethyl carbonate, and the specific adjustment parameters are as shown in Table 1 below.

[0225] Examples 13 to 18 In Examples 13 to 18, the battery manufacturing method is similar to that of Example 1, but the volume content of 1,3-dioxolane in the electrolyte is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0226] Example 19 Example 19 is a battery fabrication method similar to that of Example 1, except that sodium bis(fluorosulfonyl)imide is replaced with sodium hexafluorophosphate, that is, the mass content of sodium hexafluorophosphate in the electrolyte is 20%, and the specific adjustment parameters are as shown in Table 1 below.

[0227] Example 20 Example 20 is similar to the battery fabrication method of Example 1, except that sodium hexafluorophosphate is replaced with sodium bis(fluorosulfonyl)imide, that is, the mass content of sodium bis(fluorosulfonyl)imide in the electrolyte is 20%, and the specific adjustment parameters are as shown in Table 1 below.

[0228] Examples 21 to 24 In Examples 21 to 24, the battery manufacturing method is similar to that of Example 1, but the mass content of sodium hexafluorophosphate in the electrolyte is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0229] Examples 25-26 Examples 25 and 26 are similar to the battery manufacturing method of Example 1, except that sodium bis(fluorosulfonyl)imide is replaced with sodium trifluoromethanesulfonate and sodium bis(trifluoromethanesulfonyl)imide, respectively, and the specific adjustment parameters are as shown in Table 1 below.

[0230] Examples 27 to 30 In Examples 27 to 30, the battery manufacturing method is similar to that of Example 1, but the mass content of sodium bis(fluorosulfonyl)imide in the electrolyte solution is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0231] Example 31 In Example 31, the battery manufacturing method is similar to that of Example 1, but the manufacturing process of the negative electrode plate is adjusted. Carbon nanotubes and sodium alginate are added to water and stirred to form a uniform slurry. The slurry is applied to the negative electrode current collector, baked, and cut to obtain a negative electrode current collector with an undercoat layer. The areal density of the undercoat layer is 10 g / m. 2 The negative electrode active material hard carbon, the conductive agent acetylene black, the binder styrene butadiene rubber (SBC), and the thickener hydroxymethyl cellulose (CMC) were mixed in a weight ratio of 90:5:4:1 in an appropriate amount of deionized water with sufficient stirring to form a uniform negative electrode slurry. The negative electrode slurry was applied to a negative electrode current collector having an undercoat layer, dried at 100°C, and then pressed to obtain a negative electrode plate. The specific preparation parameters are as shown in Table 1 below.

[0232] Example 32 Example 32 is similar to the battery manufacturing method of Example 1, except that the negative electrode plate is replaced with aluminum foil, and the specific adjustment parameters are as shown in Table 1 below.

[0233] Example 33 Example 33 is similar to the battery manufacturing method of Example 31, except that carbon nanotubes are replaced with aluminum oxide, and the specific adjustment parameters are as shown in Table 1 below.

[0234] Examples 34 to 37 In Examples 34 to 37, the battery manufacturing method is similar to that of Example 1, but the surface density of the undercoat layer of the negative electrode plate is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0235] Example 38 Example 38 is similar to Example 1 in the battery preparation method, but the mass content of lithium hexafluorophosphate in the electrolyte is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0236] Example 39 Example 39 is similar to the battery fabrication method of Example 1, except that the mass content of sodium hexafluorophosphate in the electrolyte is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0237] Comparative Example 1 Comparative Example 1 is similar to the battery manufacturing method of Example 1, but the electrolyte does not contain lithium hexafluorophosphate and 1,3-dioxolane, and the specific adjustment parameters are as shown in Table 1 below.

[0238] Comparative Example 2 Comparative Example 2 is similar to the battery manufacturing method of Comparative Example 1, but the solvent is replaced with dimethyl carbonate, and the specific adjustment parameters are as shown in Table 1 below.

[0239] Comparative Example 3 Comparative Example 3 is similar to the battery manufacturing method of Comparative Example 1, but the mass content of sodium hexafluorophosphate in the electrolyte is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0240] Comparative Example 4 Comparative Example 4 was similar to the battery manufacturing method of Comparative Example 3, except that ethylene glycol dimethyl ether was replaced with dimethyl carbonate.

[0241] Comparative Example 5 Comparative Example 5 is similar to the battery manufacturing method of Example 1, but the electrolyte does not contain 1,3-dioxolane, and the specific adjustment parameters are as shown in Table 1 below.

[0242] Comparative Example 6 Comparative Example 6 is similar to the battery manufacturing method of Example 33, but the electrolyte does not contain lithium hexafluorophosphate and 1,3-dioxolane, and the specific adjustment parameters are as shown in Table 1 below.

[0243] Comparative Example 7 Comparative Example 7 is similar to the battery manufacturing method of Comparative Example 6, but the mass content of sodium hexafluorophosphate in the electrolyte is adjusted, and the specific adjustment parameters are as shown in Table 1 below.

[0244] Comparative Example 8 Comparative Example 8 is similar to the manufacturing method of the battery of Example 1, except that lithium hexafluorophosphate in the electrolyte is replaced with sodium hexafluorophosphate, and the specific adjustment parameters are as shown in Table 1 below.

[0245] 2. Performance test The performance test method is as follows. 1. Polyether 1) Detection of polyethers The battery was disassembled, the polymerized electrolyte was extracted, and the spectrum of the extracted electrolyte was collected in reflectance mode using a Thermo Scientific infrared spectrometer. -1 ~900cm -1 (For example, 850cm -1 The long chain vibration infrared peak of the main chain of the polymer appears around 950 cm -1 ~1050cm -1 (For example, 1000cm -1 If a COC vibration peak appears around 1000 kJ / cm2, it can be determined that the electrolyte contains polyether.

[0246] 2) Polyether mass content The cell was disassembled, and the electrolyte was extracted. 5 mg of the polymerized electrolyte was dissolved and dispersed in tetrahydrofuran using ultrasonic waves. The mass of the polyether in the electrolyte or the mass content of the polyether based on the total mass of the electrolyte was then determined by gel permeation chromatography.

[0247] 2, Electrolyte 1) Lithium ion mass content The electrolyte in the battery was obtained by centrifugation and detected by ion chromatography to obtain the mass content of lithium ions based on the total mass of the electrolyte.

[0248] 2) Viscosity of the electrolyte The viscosity of the electrolyte was measured at 25°C using a rheometer. At 25°C and atmospheric pressure (0.1 MPa), the shear rate of the instrument was set to 0.1 s -1 ~300s -1 The electrolyte was sheared at a setting of 0.05 to obtain viscosity curves at different shear rates, and the obtained viscosity values ​​were read.

[0249] 3) Ionic conductivity of the electrolyte The ionic conductivity of the electrolyte was tested using a conductivity meter at 25°C and atmospheric pressure (0.1 MPa). The conductivity electrode was washed with deionized water and then rinsed with absolute ethanol to remove any remaining water. After drying, the electrode was inserted into a test tube containing the electrolyte to be tested, ensuring that the platinum electrode was submerged below the surface of the electrolyte to be tested. After the meter reading stabilized, the results were recorded. The measurement was repeated three times and the average value was calculated.

[0250] 3, battery 1) Initial coulombic efficiency test At 25°C and atmospheric pressure (0.1 MPa), the battery was charged to 3.5 V at a constant current of 0.1 C, and the charge capacity at this time was recorded as the initial charge capacity of the battery. After that, the battery was left to stand for 5 minutes, and then discharged to 3.2 V at a constant current of 0.1 C. The battery was left to stand for 5 minutes, and the discharge capacity at this time was recorded as the initial discharge capacity of the battery. The initial coulombic efficiency (%) of the battery = initial discharge capacity / initial charge capacity × 100%.

[0251] 2) Room temperature cycle performance At 25°C and atmospheric pressure (0.1 MPa), the battery was charged at a constant current of 0.5 C until the voltage reached 3.5 V, and then discharged at a constant current of 1 C until the voltage reached 3.2 V, which constituted one charge-discharge cycle. The capacity of the initial discharge was taken as 100%, and the charge-discharge cycle was repeated 500 times, after which the test was stopped and the cycle capacity retention rate was recorded. The capacity retention rate was used as an evaluation index for the battery's cycle performance.

[0252] 3) High-temperature cycle performance At 60°C and atmospheric pressure (0.1 MPa), the battery was charged at a constant current of 0.5 C until the voltage reached 3.5 V, and then discharged at a constant current of 1 C until the voltage reached 3.2 V, which constituted one charge-discharge cycle. The capacity of the initial discharge was taken as 100%, and the charge-discharge cycle was repeated 500 times, after which the test was stopped and the cycle capacity retention rate was recorded. The capacity retention rate was used as an evaluation index for the battery's cycle performance.

[0253] 4) High-temperature gas generation performance At room temperature (25°C), the battery was charged to 3.5V at a constant current of 0.5C. After the battery was fully charged, the initial volume of the battery was measured using the drainage method. The battery was placed in an oven at 60°C for 24 days and then removed. It was left at room temperature for 60 minutes. After cooling to room temperature, the battery volume was measured using the drainage method within 60 minutes. The volume expansion rate of the battery was calculated based on the battery volume measured before storage. The volume expansion rate (%) of the battery after 24 days of storage at 60°C = (volume of battery measured after storage / volume of battery measured before storage) - 1.

[0254] 3. Analysis of the test results of each example and comparative example Batteries of each example and comparative example were manufactured by the above method, and performance parameters were measured. The results are shown in Table 1 below.

[0255] [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5]

Table 1-6

Table 1-7

Table 1-8

Table 1-9

Table 1-10

Table 1-11

Table 1-12

Table 1-13

[0256] As can be seen from the above results, the secondary battery electrolytes in Examples 1 to 39 contain an electrolyte salt, a solvent, and a polyether. The electrolyte contains a first sodium salt of sodium hexafluorophosphate and / or a second sodium salt of any one of sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide. The solvent is ethylene glycol dimethyl ether or dimethyl carbonate. The polyether contains any one of poly-1,3-dioxolane, polytetrahydropyran, polytetrahydrofuran, and poly-1,4-dioxane. Comparisons of Examples 1 to 11, 13 to 39 with Comparative Examples 1, 3, 5 to 8, and Example 12 with Comparative Examples 2 and 4 reveal that electrolytes containing polyethers can reduce the high-temperature expansion rate of batteries, reduce high-temperature gas generation, and improve battery safety.

[0257] As can be seen from a comparison of Examples 1, 3, and 4 with Example 2, when the electrolyte contains lithium ions and the mass content of the lithium ions is 0.05% to 0.46% based on the total mass of the electrolyte, the room temperature cycle performance and high temperature cycle performance of the battery can be improved and the high temperature gas generation phenomenon of the battery can be reduced.As can be seen from Examples 1, 5 to 8, and 38, when the electrolyte contains lithium ions and the mass content of the lithium ions is 0.05% to 0.46% based on the total mass of the electrolyte, the battery has excellent room temperature cycle performance and high temperature cycle performance and low high temperature gas generation.

[0258] As can be seen from Examples 1, 13 to 18, when the mass content of polyether is 10% to 70% based on the total mass of the electrolyte, the battery has excellent initial coulombic efficiency, room temperature cycle performance and high temperature performance, low high-temperature gas generation, and the operating temperature of the battery can be expanded.

[0259] As can be seen from Examples 1 to 39, when polyether is produced by in-situ polymerization of cyclic ether compounds in an electrolyte solution induced by any one of Lewis acids selected from phosphorus pentafluoride, aluminum trichloride, lithium chloride, and boron trifluoride, the high-temperature gas generation phenomenon in batteries can be reduced.

[0260] As can be seen from the comparison of Examples 1, 3, and 4 with Example 2, when the Lewis acid is derived from an additive in the electrolyte, and the additive includes one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate, the room temperature cycle performance and high temperature cycle performance of the battery can be improved and the high temperature gas generation phenomenon of the battery can be reduced.

[0261] As can be seen from the comparison between Examples 1 and 4 and Example 3, when the Lewis acid is derived from an additive in the electrolyte, and the additive includes one or two selected from lithium hexafluorophosphate and lithium tetrafluoroborate, the room temperature cycle performance and high temperature cycle performance of the battery are improved, and the high temperature gas generation phenomenon of the battery is reduced.

[0262] As can be seen from Examples 1, 5 to 8, and 38, when the mass content of the added additive is 1% to 10% based on the total mass of the electrolyte, the electrolyte has appropriate viscosity and good ionic conductivity, the battery has excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, the battery has excellent electrochemical performance and safety performance, and the operating temperature of the battery can be expanded.

[0263] As can be seen from the comparison between Examples 1, 6, and 7 and Examples 5 and 8, when the mass content of the added additive is 2% to 6% based on the total mass of the electrolyte, the initial coulombic efficiency, room temperature cycle performance, and high temperature cycle performance of the battery can be improved, and the high temperature gas generation phenomenon of the battery can be reduced.

[0264] As can be seen from Examples 1 and 9 to 11, when the cyclic ether compound includes one or more selected from 1,3-dioxolane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and tetrahydropyran, the electrolyte has suitable viscosity and good ionic conductivity, the battery has excellent initial coulombic efficiency, room temperature cycle performance, high temperature cycle performance, and low high-temperature gas generation, the battery has excellent electrochemical performance and safety performance, and the operating temperature of the battery can be expanded.

[0265] As can be seen from the comparison between Example 1 and Example 12, when the solvent contains a chain ether compound, the viscosity of the electrolyte can be increased, the initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the battery can be improved, the high temperature gas generation phenomenon of the battery can be reduced, the electrochemical performance and safety performance of the battery can be improved, and the operating temperature of the battery can be expanded.

[0266] As can be seen from the comparison of Examples 1, 14 to 17 with Examples 13 and 18, when the volume content of the cyclic ether compound added is 1 / 5 to 5 based on the total volume of the solvent in the electrolyte, the high-temperature gas generation phenomenon of the battery is reduced, and at the same time, the electrolyte has appropriate viscosity and good conductivity, and the battery maintains excellent initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance.

[0267] Comparing Examples 1, 15-16 with Examples 13-14, 17-18, it can be seen that when the volume content of the cyclic ether compound added is 1 / 3-3 based on the total volume of the solvent in the electrolyte, the high-temperature gas generation phenomenon of the battery can be further reduced, and at the same time, the electrolyte has appropriate viscosity and good conductivity, and the battery maintains excellent initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance.

[0268] As can be seen from Examples 1, 19 and 20, when the electrolyte contains at least one of the first sodium salt sodium hexafluorophosphate and the second sodium salt sodium bis(fluorosulfonyl)imide, the battery has low high-temperature gas production.

[0269] As can be seen from Examples 1 and 19, when the electrolyte contains the first sodium salt sodium hexafluorophosphate, the battery has excellent initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance, and the battery has low high temperature gas generation.

[0270] As can be seen from Examples 1 and 20, when the electrolyte contains the second sodium salt, sodium bis(fluorosulfonyl)imide, the battery has low high temperature gas production.

[0271] As can be seen from a comparison between Example 1 and Examples 19 to 20, when the electrolyte contains the first sodium salt, sodium hexafluorophosphate, and the second sodium salt, sodium bis(fluorosulfonyl)imide, the initial coulombic efficiency, room temperature cycle performance, and high temperature cycle performance of the battery can be improved, and the high temperature gas generation phenomenon of the battery can be reduced.

[0272] A comparison of Examples 1, 22, 23, and 39 with Examples 21 and 24 shows that, when the mass content of the first sodium salt, sodium hexafluorophosphate, in the electrolyte is 2% to 40%, based on the total mass of the electrolyte, the initial coulombic efficiency and room temperature cycle performance of the battery can be improved, and the high-temperature gas generation phenomenon of the battery can be reduced.

[0273] As can be seen from Examples 1, 25, and 26, when the second sodium salt includes one or more selected from sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide, the battery has excellent initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance, and low high-temperature gas generation, and the operating temperature of the battery can be expanded.

[0274] As can be seen from the comparison of Examples 1, 28-29 with Examples 27 and 30, when the mass content of the second sodium salt in the electrolyte is 1% to 10% based on the total mass of the electrolyte, the high-temperature cycle performance of the battery can be improved and the high-temperature gas generation phenomenon of the battery can be reduced.

[0275] As can be seen from Examples 1 to 37, when the viscosity of the electrolyte at 25° C. is less than 1300 mPa·s, the electrolyte has an appropriate viscosity and good ionic conductivity.

[0276] As can be seen from the comparison between Example 1 and Example 31, when the secondary battery is a negative electrode-free sodium metal battery, the room temperature cycle performance and high temperature cycle performance of the battery can be improved and the high temperature gas generation phenomenon of the battery can be reduced.

[0277] As can be seen from a comparison between Examples 1 and 33 and Example 32, when the negative electrode plate includes a negative electrode current collector and an undercoat layer formed on at least a portion of the surface of the negative electrode current collector, the high-temperature cycle performance of the battery can be improved and the high-temperature gas generation phenomenon of the battery can be reduced.

[0278] As can be seen from the comparison between Example 1 and Example 33, when the undercoat layer is a conductive carbon coating, it can improve the room temperature cycle performance and high temperature cycle performance of the battery and reduce the high temperature gas generation phenomenon of the battery.

[0279] As can be seen from a comparison of Examples 1, 34-35 and Examples 36-37, the surface density of the conductive carbon coating is 5-50 g / m 2 In this case, the room temperature cycle performance and high temperature cycle performance of the battery can be improved, and the high temperature gas generation phenomenon of the battery can be reduced. [Explanation of symbols]

[0280] 1 battery pack 2 Upper Box 3 Lower Box 4 Battery Module 5 Secondary battery 51 cases 52 Electrode assembly 53 Cover plate

Claims

1. 1. A secondary battery electrolyte comprising an electrolyte salt, a solvent, and a polyether.

2. 2. The electrolyte solution according to claim 1, wherein the electrolyte solution contains lithium ions, and the mass content of the lithium ions is 0.05% to 0.46% based on the total mass of the electrolyte solution.

3. 3. The electrolyte solution according to claim 1, wherein the mass content of the polyether is 10% to 70% based on the total mass of the electrolyte solution.

4. 4. The electrolyte solution according to claim 1, wherein the polyether is produced by in-situ polymerization of a cyclic ether compound in the electrolyte solution induced by a Lewis acid.

5. 5. The electrolyte solution according to claim 4, wherein the Lewis acid is derived from an additive in the electrolyte solution, and the additive comprises one or more selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluoro(oxalato)borate, and optionally one or two of lithium hexafluorophosphate and lithium tetrafluoroborate.

6. The electrolyte according to claim 5, wherein the mass content of the additive added is 1% to 10%, and optionally 2% to 6%, based on the total mass of the electrolyte.

7. The electrolyte solution according to any one of claims 4 to 6, characterized in that the cyclic ether compound comprises one or more selected from 1,3-dioxolane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and tetrahydropyran, and optionally is one or more of 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

8. 8. The electrolytic solution according to claim 1, wherein the solvent contains a chain ether compound.

9. The electrolytic solution according to any one of claims 1 to 8, characterized in that the solvent contains one or more selected from ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether.

10. The electrolyte solution according to any one of claims 4 to 9, characterized in that the volume content of the cyclic ether compound added is 1 / 5 to 5, and optionally 1 / 3 to 3, based on the total volume of the solvent in the electrolyte solution.

11. The electrolyte salt includes at least one of a first sodium salt and a second sodium salt, the first sodium salt including one or more selected from sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, and sodium trifluoroacetate, and the anion structure of the second sodium salt includes at least one of the structures shown in Formula I and Formula II, 【Chemical 1】 R １ , R ２ , R ３ are each independently fluorine or C １ ~C ６ 11. The electrolytic solution according to claim 1, wherein the fluoroalkyl group is a fluoroalkyl group represented by the formula:

12. 12. The electrolyte solution according to claim 11, wherein the mass content of the first sodium salt in the electrolyte solution is 2% to 40%, based on the total mass of the electrolyte solution.

13. 13. The electrolyte solution according to claim 11 or 12, wherein the second sodium salt comprises one or more selected from the group consisting of sodium trifluoromethanesulfonate, sodium bis(fluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide.

14. The electrolyte solution according to any one of claims 11 to 13, wherein the mass content of the second sodium salt in the electrolyte solution is 1% to 10% based on the total mass of the electrolyte solution.

15. 15. The electrolyte solution according to claim 1, wherein the viscosity of the electrolyte solution at 25° C. is less than 1300 mPa·s.

16. adding an additive which is a Lewis acid or a Lewis acid precursor and a cyclic ether compound to a composition which includes an electrolyte salt and a solvent; allowing to polymerize in situ for at least 24 hours to obtain a secondary battery electrolyte; A method for producing a secondary battery electrolyte, comprising:

17. 17. The manufacturing method according to claim 16, wherein the additive comprises one or more selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluoro(oxalato)borate, aluminum chloride, and aluminum trifluoromethanesulfonate, and optionally one or two of lithium hexafluorophosphate and lithium tetrafluoroborate.

18. 18. The method of claim 16 or 17, wherein the mass content of the additive added is 1% to 10%, and optionally 2% to 6%, based on the total mass of the electrolyte.

19. The method according to any one of claims 16 to 18, wherein the cyclic ether compound comprises one or more selected from 1,3-dioxolane, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,2,3,4-diepoxybutane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane, and tetrahydropyran, and optionally one or more of 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, and tetrahydropyran.

20. The method according to any one of claims 16 to 19, wherein the volume content of the cyclic ether compound added is 1 / 5 to 5, and optionally 1 / 3 to 3, based on the total volume of the solvent in the electrolyte solution.

21. A secondary battery comprising an electrolytic solution, the electrolytic solution comprising the electrolytic solution according to any one of claims 1 to 15 or the electrolytic solution produced by the production method according to any one of claims 16 to 20.

22. 22. The secondary battery of claim 21, wherein the secondary battery comprises at least one of a sodium ion battery and a lithium ion battery.

23. 23. The secondary battery according to claim 21, wherein the secondary battery is a negative electrode-free sodium metal battery.

24. The secondary battery according to any one of claims 21 to 23, characterized in that the secondary battery includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and an undercoat layer formed on at least a portion of a surface of the negative electrode current collector.

25. 25. The secondary battery of claim 24, wherein the undercoat layer is a conductive carbon coating.

26. The surface density of the conductive carbon coating is 5 to 50 g / m ２ 26. The secondary battery according to claim 25,

27. A battery module comprising the secondary battery according to any one of claims 21 to 26.

28. A battery pack comprising at least one of the secondary battery according to any one of claims 21 to 26 and the battery module according to claim 27.

29. A power consumption device comprising at least one selected from the group consisting of the secondary battery according to any one of claims 21 to 26, the battery module according to claim 27, and the battery pack according to claim 28.

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