Electrolytes, secondary batteries, and power consumption devices

Abstract

This application provides a secondary battery, an electrolyte, and a power consumption device. The secondary battery comprises a positive electrode plate, an electrolyte, a separator, and a negative electrode current collector. The electrolyte comprises a non-aqueous solvent, an electrolyte salt, and an additive, wherein the non-aqueous solvent comprises an ether-based organic solvent, and the additive comprises a first additive, the first additive comprising one or more of phosphite ester-based additives or borate ester-based additives. This application provides an electrolyte, a secondary battery, and a power consumption device for improving the cycle performance and Coulomb efficiency of the secondary battery.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority to Chinese Patent Application No. 202310833096.9, proposed on July 7, 2023, entitled “Electrolyte, Secondary Battery and Power Consumption Device,” and all contents of that application are incorporated herein by reference.

[0002] This application relates to the battery technology field, and more particularly to electrolytes, secondary batteries, and power consumption devices. [Background technology]

[0003] As lithium-ion battery technology gradually expands its applications in markets such as consumer electronics, electric vehicles, and energy storage, the problem of lithium resource shortages is also beginning to emerge. Sodium-based batteries are gradually attracting attention because sodium is abundant on Earth, and they occupy an important strategic position in application fields with relatively high cost requirements, such as energy storage. Metallic sodium has a higher reduction potential and a larger relative molecular mass than metallic lithium, so the energy density of sodium-ion secondary batteries, which operate on a similar principle, is significantly lower than that of lithium-ion batteries. Furthermore, the larger ionic radius of sodium ions leads to greater volume expansion during insertion and removal from the positive and negative electrode materials, reducing the reversibility of the battery cycle. All of these factors significantly limit the widespread application of sodium-ion secondary batteries. With the development and progress of electrolyte and additive technology, and surface modification technology, the problem of sodium dendrite growth due to uneven deposition on metal surfaces, which has plagued the academic community for a long time, has been significantly improved, and it is expected that the safety performance of products will also be significantly enhanced, bringing high-energy-density sodium metal negative electrodes back into people's sights.

[0004] However, sodium metal has extremely high chemical activity and readily reacts violently with electrolytes to form solid electrolyte interfacial films, so the practical application of sodium metal anodes faces enormous challenges. [Overview of the project] [Means for solving the problem]

[0005] This application provides an electrolyte, a secondary battery, and a power consumption device for improving the cycle performance and Coulomb efficiency of a secondary battery.

[0006] A first aspect of this application provides a secondary battery comprising a positive electrode plate, an electrolyte, a separator, and a negative electrode current collector, wherein the electrolyte comprises a non-aqueous solvent, an electrolyte salt, and an additive, the non-aqueous solvent comprising an ether-based organic solvent, and the additive comprising a first additive, the first additive comprising one or more of phosphite ester-based additives or borate ester-based additives.

[0007] By introducing the first additive into an ether-based organic solvent electrolyte, the first additive forms a film on the positive electrode surface, effectively reducing oxidative decomposition of the ether-based solvent on the positive electrode surface and decreasing the reciprocal movement of products due to oxidative decomposition between the positive and negative electrodes. Furthermore, the first additive is relatively stable with respect to sodium metal and preferentially undergoes oxidative decomposition on the oxide positive electrode surface to form a CEI film containing boron or phosphorus compounds, thereby suppressing oxidative decomposition of the ether-based electrolyte on the positive electrode surface while simultaneously protecting the positive electrode structure from destruction, and further improving the Coulomb efficiency and cycle performance of the battery. In particular, the trivalent boron atom in the borate ester additive has an empty P orbital, which is expressed as Lewis acidic overall, and can coordinate with anions to increase the transport rate of lithium / sodium ions. It can also coordinate with oxygen atoms in ether-based organic solvent molecules to reduce the charge density of oxygen in the solvent molecules, increase the solvent oxidation potential, and further resist oxidation of the ether-based organic solvent by the positive electrode active material.

[0008] In any embodiment of the first aspect, the secondary battery is a sodium-ion secondary battery.

[0009] In any embodiment of the first aspect, the secondary battery is a sodium secondary battery without a negative electrode. Since the sodium secondary battery without a negative electrode does not have sodium metal pre-set on the negative electrode side, it effectively mitigates the problem of reduced Coulomb efficiency and cycle performance due to the vigorous reaction between the sodium metal and the electrolyte.

[0010] In any embodiment of the first aspect, the negative electrode current collector comprises a conductive substrate and a selective conductive layer, the conductive layer being provided on at least one side of the conductive substrate, the conductive substrate comprising one of bare copper, aluminum foil, aluminum alloy foil, and an aluminum-based composite current collector, the selective conductive layer comprising a conductive agent and an adhesive, and further selectively, the conductive agent comprising graphite, graphene, carbon fiber, carbon black, soft carbon, hard carbon, multi-walled carbon nanotubes, or single-walled carbon nanotubes. The provision of the conductive layer is advantageous for sodium ions to be reduced by electrons during the charging process and deposited on the negative electrode current collector to form a sodium metal negative electrode.

[0011] In any embodiment of the first aspect, the ether-based organic solvent includes one or more of ethylene glycol diethyl ether (DEE), ethylene glycol dimethyl ether (DME, 1,2-dimethoxyethane), diethylene glycol dimethyl ether (DEGDME, diethylene glycol dimethyl ether), tetraethylene glycol dimethyl ether (TEGDME), triethylene glycol dimethyl ether (TRGDME), ethylene glycol ethyl methyl ether, ethylene glycol dibutyl ether (DBE), 1,3-dioxolane (DOL), 1,4-dioxane (1,4-dioxane), tetrahydrofuran (THF), or methyltetrahydrofuran. Each of the above ether-based organic solvents has a stable chemical structure, good fluidity, good solubility of additives, and is advantageous for the exertion of the effects of the additives.

[0012] In any embodiment of the first aspect, the ether-based organic solvent selectively contains ethylene glycol diethyl ether. This is advantageous because the interaction between ethylene glycol diethyl ether and anions is weakened, and its oxidation resistance is stronger, thus allowing the additives within it to exert their effects more effectively.

[0013] In any embodiment of the first aspect, the mass content of ethylene glycol diethyl ether in the electrolyte is selectively 30% or more, and selectively 40% to 65%. By controlling the proportion of ethylene glycol diethyl ether in the electrolyte, overcharging of the battery capacity can be effectively suppressed, and the stability of the battery to the high-voltage positive electrode and the Coulomb efficiency of the battery can be improved.

[0014] In any embodiment of the first aspect, the phosphite ester additive comprises one or more of tris(trimethylsilane) phosphite (TMSP), trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, or triphenyl phosphite. The phosphite ester additive more efficiently oxidizes and decomposes on the oxide cathode surface to form a CEI film containing phosphorus compounds, thereby more reliably suppressing the oxidative decomposition of ether-based organic solvents on the cathode surface while simultaneously protecting the cathode structure from destruction.

[0015] In any embodiment of the first aspect, the borate ester additive comprises one or more of tris(trimethylsilane)borate (TMSB), trimethylborate (TMB), triethylborate (TEB), tripropylborate (TPB), tributylborate (TBB), or triphenylborate. The borate ester additive more efficiently oxidizes and decomposes on the oxide cathode surface to form a CEI film containing boron compounds, thereby more reliably suppressing the oxidative decomposition of ether-based organic solvents on the cathode surface while simultaneously protecting the cathode structure from destruction.

[0016] In any embodiment of the first aspect, the first additive comprises tris(trimethylsilane)phosphite and / or tris(trimethylsilane)borate. When either of the two substances is used as the first additive, the resulting CEI film is more stable and the protective effect on the cathode structure is more pronounced.

[0017] In any embodiment of the first aspect, the mass content of the first additive in the electrolyte is 0.2% to 5%, and selectively 0.2% to 3%, and by utilizing the first additive, a sufficient CEI film can be formed, providing protection to the positive electrode, while avoiding an increase in internal resistance due to excessive CEI film thickness, which would affect the multiplier performance of the battery.

[0018] In any embodiment of the first aspect, the additive further comprises a second additive, the second additive comprising a C2-C7 fluoroalkyl ether additive. By introducing the second additive into the electrolyte, the second additive forms a film on the negative electrode surface, effectively reducing the reduction of the oxidative decomposition products on the negative electrode surface, and further suppressing the reciprocal movement of the oxidative decomposition products between the positive and negative electrodes. Furthermore, the reaction between the second additive and sodium metal is relatively weak, and the inorganic SEI components such as NaF produced by the reaction disperse on the negative electrode, forming a film, effectively suppressing the reciprocal movement of the oxidative decomposition products between the positive and negative electrodes, thereby achieving the objective of effectively improving Coulomb efficiency and enhancing the battery's cycle performance.

[0019] In any embodiment of the first aspect, the C2-C7 fluoroalkyl ether additives are 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, 1,1,2,3,3,3-pentafluoropropyl-2,2,2- This comprises one or more of the following: difluoroethyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1,1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, or 2,2,2-trifluoroethyl ether. The reaction between each of the above C2-C7 fluoroalkyl ether additives and sodium metal is relatively weak, and the inorganic SEI components such as NaF produced by the reaction are dispersed on the negative electrode, which more effectively suppresses the reciprocal movement of oxidative decomposition products of the electrolyte between the positive and negative electrodes, thereby better achieving the effect of suppressing capacity overcharging.

[0020] In any embodiment of the first aspect, the fluoroalkyl ether-based additives of C2 to C7 are selectively one or more of methyl nonafluorobutyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. It achieves both high cycle performance and high capacity retention characteristics of the secondary battery.

[0021] In any embodiment of the first aspect, the mass content of the second additive in the above electrolyte is 0.2% to 5%, and selectively 0.2% to 2%. By using the second additive, a sufficient SEI film can be formed to form a protective effect on the negative electrode, and it is possible to avoid the increase in internal resistance due to the overly large thickness of the SEI film and the influence on the rate performance of the battery.

[0022] In any embodiment of the first aspect, the above electrolyte salt includes one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium hexafluoroarsenate (NaAsF6), sodium trifluoroacetate (CF3COONa), sodium trifluoromethanesulfonate (CF3NaO3S, NaOTf), and sodium tetraphenylborate (NaBPh4). At low temperatures, sodium trifluoromethanesulfonate has a relatively high solubility in ether-based organic solvents, and the efficiency of sodium metal deposition and stripping is relatively high, giving the battery relatively good cycle performance at low temperatures (for example, when below -30°C). At room temperature, the side reaction between sodium trifluoromethanesulfonate and the sodium metal negative electrode becomes intense, deteriorating the cycle performance of the entire battery. By adopting other electrolyte salts in the above electrolyte, the cycle performance of the secondary battery at room temperature can be enhanced.

[0023] In any embodiment of the first aspect, the electrolyte contains a first sodium salt and sodium trifluoromethanesulfonate, and the first sodium salt contains any one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, or sodium hexafluoroarsenate. Thereby, the low-temperature cycle performance and room-temperature cycle performance of the secondary battery having this electrolyte can be enhanced.

[0024] In any embodiment of the first aspect, optionally, the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, and optionally, the mass content of the first sodium salt in the electrolyte is 3% to 40%, and optionally 5% to 30%.

[0025] When the electrolyte of the present application contains sodium trifluoromethanesulfonate, at low temperature, the solubility of sodium trifluoromethanesulfonate (NaOTf) in diethylene glycol dimethyl ether is relatively high. In any embodiment of the second aspect, optionally, the ether-based organic solvent contains diethylene glycol dimethyl ether in order to further increase the ionic conductivity of the electrolyte at low temperature. Further, the mass content of diethylene glycol dimethyl ether in the electrolyte is optionally 20% or more, and optionally 25% to 40%. Of course, when the electrolyte does not contain sodium trifluoromethanesulfonate, the ether-based organic solvent may contain diethylene glycol dimethyl ether.

[0026] In any embodiment of the first aspect, the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, and optionally, the mass content of the first sodium salt in the electrolyte is 3% to 40%, and optionally 5% to 30%, thereby better improving the low-temperature cycle performance and room-temperature cycle performance of the secondary battery.

[0027] In any embodiment of the first aspect, optionally, the mass ratio of sodium trifluoromethanesulfonate to diethylene glycol dimethyl ether is X, where 0.05 ≦ X ≦ 0.2, and optionally 0.1 ≦ X ≦ 0.13. Thereby, the ionic conductivity of the electrolytic solution at low temperatures is further improved.

[0028] In any embodiment of the first aspect, the positive electrode active material of the positive electrode plate is a layered metal oxide. Optionally, the positive electrode active material has the chemical formula Na x Mn a Q b O 2-c-d F c and contains one or more of the oxides, where 0.5 < x ≦ 1, 0 < a, 0 < b, 0 ≦ c ≦ 0.2, -0.1 ≦ d ≦ 0.1, and Q contains one or more elements among Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi.

[0029] The second aspect of the present application provides an electrolytic solution, which includes a non-aqueous solvent, an electrolyte salt, and an additive. Here, the non-aqueous solvent includes an ether-based organic solvent, and the additive includes a first additive, and the first additive includes one or more of a phosphite-based additive or a borate-based additive.

[0030] The technical effects of the electrolyte described above will be explained using the example of a positive electrode active material being an oxide. By introducing the first additive into an ether-based organic solvent electrolyte, the first additive forms a film on the positive electrode surface, effectively reducing the oxidative decomposition of the ether-based solvent on the positive electrode surface and decreasing the reciprocal movement of products due to oxidative decomposition between the positive and negative electrodes. Furthermore, the first additive is relatively stable with respect to sodium metal and preferentially undergoes oxidative decomposition on the oxide positive electrode surface to produce a CEI film containing boron or phosphorus compounds, thereby suppressing the oxidative decomposition of the ether-based electrolyte on the positive electrode surface while protecting the positive electrode structure from destruction, and further improving the Coulomb efficiency and cycle performance of the battery. In particular, the trivalent boron atom in the borate ester additive has an empty P orbital, which is expressed as Lewis acidic overall, and can coordinate with anions to increase the transport rate of sodium ions. It can also coordinate with oxygen atoms in ether-based organic solvent molecules to reduce the charge density of oxygen in the solvent molecules, increase the solvent oxidation potential, and further resist oxidation of the ether-based organic solvent by the positive electrode oxide.

[0031] In any embodiment of the second aspect, the ether-based organic solvent includes one or more of ethylene glycol diethyl ether (DEE), ethylene glycol dimethyl ether (DME, 1,2-dimethoxyethane), diethylene glycol dimethyl ether (DEGDME, diethylene glycol dimethyl ether), tetraethylene glycol dimethyl ether (TEGDME), triethylene glycol dimethyl ether (TRGDME), ethylene glycol ethyl methyl ether, ethylene glycol dibutyl ether (DBE), 1,3-dioxolane (DOL), 1,4-dioxane (1,4-dioxane), tetrahydrofuran (THF), or methyltetrahydrofuran. Each of the above ether-based organic solvents has a stable chemical structure, good fluidity, good solubility of additives, and is advantageous for the exertion of the effects of the additives.

[0032] In any embodiment of the second aspect, the ether-based organic solvent selectively contains ethylene glycol diethyl ether. This is advantageous because the interaction between ethylene glycol diethyl ether and anions is weakened, and its oxidation resistance is stronger, thus allowing the additives within it to exert their effects more effectively.

[0033] In any embodiment of the second aspect, the mass content of ethylene glycol diethyl ether in the electrolyte is selectively 30% or more, and selectively 40% to 65%. By controlling the proportion of ethylene glycol diethyl ether in the electrolyte, overcharging of the battery capacity can be effectively suppressed, and the stability of the battery to the high-voltage positive electrode and the Coulomb efficiency of the battery can be improved.

[0034] In any embodiment of the second aspect, the phosphite ester additive comprises one or more of tris(trimethylsilane) phosphite (TMSP), trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, or triphenyl phosphite. The phosphite ester additive more efficiently oxidizes and decomposes on the oxide cathode surface to form a CEI film containing phosphorus compounds, thereby more reliably suppressing the oxidative decomposition of ether-based organic solvents on the cathode surface while simultaneously protecting the cathode structure from destruction.

[0035] In any embodiment of the second aspect, the borate ester additive comprises one or more of tris(trimethylsilane)borate (TMSB), trimethylborate (TMB), triethylborate (TEB), tripropylborate (TPB), tributylborate (TBB), or triphenylborate. The borate ester additive more efficiently oxidizes and decomposes on the oxide cathode surface to form a CEI film containing boron compounds, thereby more reliably suppressing the oxidative decomposition of ether-based organic solvents on the cathode surface while simultaneously protecting the cathode structure from destruction.

[0036] In any embodiment of the second aspect, the first additive comprises tris(trimethylsilane) phosphite and / or tris(trimethylsilane) borate. When either of the two substances is used as the first additive, the resulting CEI film is more stable and the protective effect on the cathode structure is more pronounced.

[0037] In any embodiment of the second aspect, the mass content of the first additive in the electrolyte is 0.2% to 5%, and selectively 0.2% to 3%, and the first additive is used to form a sufficient CEI film, providing protection to the positive electrode while avoiding an increase in internal resistance due to excessive CEI film thickness, which would affect the battery's magnification performance.

[0038] In any embodiment of the second aspect, the additive further comprises a second additive, the second additive comprising a C2-C7 fluoroalkyl ether additive. By introducing the second additive into the electrolyte, the second additive forms a film on the negative electrode surface, effectively reducing the reduction of the oxidative decomposition products on the negative electrode surface, and further suppressing the reciprocal movement of the oxidative decomposition products between the positive and negative electrodes. Furthermore, the reaction between the second additive and sodium metal is relatively weak, and the inorganic SEI components such as NaF produced by the reaction are dispersed on the negative electrode, effectively suppressing the reciprocal movement of the oxidative decomposition products between the positive and negative electrodes, thereby achieving the objective of effectively improving Coulomb efficiency and enhancing the battery's cycle performance.

[0039] In any embodiment of the second aspect, the C2-C7 fluoroalkyl ether additives are 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, 1,1,2,3,3,3-pentafluoropropyl-2,2,2- This comprises one or more of the following: difluoroethyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1,1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, or 2,2,2-trifluoroethyl ether. The reaction between each of the above C2-C7 fluoroalkyl ether additives and sodium metal is relatively weak, and the inorganic SEI components such as NaF produced by the reaction are dispersed on the negative electrode, which more effectively suppresses the reciprocal movement of oxidative decomposition products of the electrolyte between the positive and negative electrodes, thereby better achieving the effect of suppressing capacity overcharging.

[0040] In any embodiment of the second aspect, the C2-C7 fluoroalkyl ether additives are selectively one or more of methyl nonafluorobutyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. This achieves both high cycle performance and high capacity maintenance characteristics for secondary batteries.

[0041] In any embodiment of the second aspect, the mass content of the second additive in the electrolyte is 0.2% to 5%, and selectively 0.2% to 2%. By using the second additive, a sufficient SEI film can be formed, providing protection to the negative electrode, while avoiding an increase in internal resistance due to excessive SEI film thickness, which would affect the battery's magnification performance.

[0042] In any embodiment of the second aspect, the electrolyte salt includes one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium hexafluoroarsenate (NaAsF6), sodium trifluoroacetate (CF3COONa), sodium trifluoromethanesulfonate (CF3NaO3S, NaOTf), and sodium tetraphenylborate (NaBPh4). At low temperatures, sodium trifluoromethanesulfonate has relatively high solubility in ether-based organic solvents and relatively high Coulomb efficiency for the deposition and detachment of sodium metal, giving the battery relatively good cycle performance at low temperatures (for example, below -30°C). At room temperature, the side reaction between sodium trifluoromethanesulfonate and the sodium metal anode becomes vigorous, worsening the overall cycle performance of the battery. By adopting other electrolyte salts in the electrolyte, the cycle performance of the secondary battery at room temperature can be improved.

[0043] In any embodiment of the second aspect, the electrolyte comprises a first sodium salt and sodium trifluoromethanesulfonate, wherein the first sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, or sodium hexafluoroarsenate. This enhances the low-temperature and room-temperature cycle performance of the secondary battery having this electrolyte.

[0044] In any embodiment of the second aspect, selectively, the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, selectively, the mass content of the first sodium salt in the electrolyte is 3% to 40%, and selectively, 5% to 30%.

[0045] When the electrolyte of this application contains sodium trifluoromethanesulfonate, sodium trifluoromethanesulfonate (NaOTf) has relatively high solubility in diethylene glycol dimethyl ether at low temperatures. To further increase the ionic conductivity of the electrolyte at low temperatures, in any embodiment of the first aspect, the ether-based organic solvent selectively contains diethylene glycol dimethyl ether, and the mass content of diethylene glycol dimethyl ether in the electrolyte is selectively 20% or more, and selectively 25% to 40%. Of course, when the electrolyte does not contain sodium trifluoromethanesulfonate, the ether-based organic solvent may contain diethylene glycol dimethyl ether.

[0046] In any embodiment of the second aspect, the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, and selectively, the mass content of the first sodium salt in the electrolyte is 3% to 40%, and selectively, 5% to 30%, thereby better improving the low-temperature cycle performance and room-temperature cycle performance of the secondary battery.

[0047] In any embodiment of the second aspect, the mass ratio of sodium trifluoromethanesulfonate to diethylene glycol dimethyl ether is selectively X, where 0.05 ≤ X ≤ 0.2, and selectively 0.1 ≤ X ≤ 0.13. This further improves the ionic conductivity of the electrolyte at low temperatures.

[0048] A third aspect of this application provides a power consumption device, which includes a secondary battery, which is selected from the secondary batteries in any one embodiment of the first aspect. To more clearly illustrate the technical concept of the embodiments of this application, the following is a brief introduction to the drawings that may be used in the embodiments of this application. It is obvious that the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without expending any creative effort. [Brief explanation of the drawing]

[0049] [Figure 1] This is a schematic diagram of a secondary battery according to one embodiment of the present application. [Figure 2] Figure 1 is an exploded view of a secondary battery according to one embodiment of this application. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present application. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of this application. [Figure 6] This is a schematic diagram of a power consumption device in which a secondary battery is used as a power source according to one embodiment of this application. In the drawing, the drawing is not drawn to actual scale. [Modes for carrying out the invention]

[0050] The embodiments of this application will be described in more detail below, linking them with the drawings and examples. The detailed descriptions of the embodiments and drawings below are for illustrative purposes to illustrate the principles of this application, but are not intended to limit the scope of this application; in other words, this application is not limited to the embodiments described.

[0051] The following describes in detail embodiments of the negative electrode plate, secondary battery, and power consumption device specifically disclosed in this application, with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and redundant explanations of structures that are actually the same may be omitted. This is to avoid making the following explanation unnecessarily long and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and do not limit the topics described in the claims.

[0052] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the endpoints, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 can also be expected. Furthermore, if 1 and 2 are listed as the minimum range values ​​and 3, 4, and 5 are listed as the maximum range values, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 can all be expected. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression of 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" represents all real numbers between "0 to 5" already listed in this specification, and "0 to 5" is simply an abbreviated representation of combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0054] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts.

[0055] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the fact that the method referred to above may further include step (c) means that step (c) may be added to the method in any order, for example the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), and so on.

[0056] Unless otherwise specified, the terms “includes” and “inclusion” as used in this application may be open or closed. For example, “includes” and “inclusion” may mean that other components not listed may be included or inclusion, or that only the listed components may be included or inclusion.

[0057] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the conditions A is true (or exists) and B is false (or does not exist), the condition A is false (or does not exist) but B is true (or exists), and the condition both A and B are true (or exist) all satisfy "A or B."

[0058] [Secondary battery] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be used continuously after being discharged by activating the active material through a charging method.

[0059] Generally, a secondary battery includes a positive electrode plate, a negative electrode current collector (or negative electrode plate), a separator, and an electrolyte. During charging and discharging of the battery, active ions (e.g., lithium ions or sodium ions) move back and forth between the positive and negative electrode plates, undergoing absorption and release. The separator is placed between the positive and negative electrode plates and primarily serves to prevent short circuits between the positive and negative electrodes, while also allowing active ions to pass through. The electrolyte primarily serves to conduct active ions between the positive and negative electrode plates.

[0060] There is a problem in that secondary batteries have reduced Coulomb efficiency and insufficient cycle performance. To solve the above problem, the first embodiment of this application provides a secondary battery comprising a positive electrode plate, an electrolyte, a separator, and a negative electrode current collector, wherein the electrolyte comprises a non-aqueous solvent, an electrolyte salt, and an additive, the non-aqueous solvent comprising an ether-based organic solvent, and the additive comprising a first additive, the first additive comprising one or more of a phosphite ester-based additive or a borate ester-based additive.

[0061] By introducing the first additive into an ether-based organic solvent electrolyte, the first additive forms a film on the positive electrode surface, effectively reducing oxidative decomposition of the ether-based electrolyte on the positive electrode surface and decreasing the reciprocal movement of oxidative decomposition products between the positive and negative electrodes. Furthermore, the first additive is relatively stable with respect to sodium metal and preferentially undergoes oxidative decomposition on the oxide positive electrode surface to form a CEI film containing boron or phosphorus compounds, thereby suppressing oxidative decomposition of the ether-based electrolyte on the positive electrode surface while simultaneously protecting the positive electrode structure from destruction, and further improving the Coulomb efficiency and cycle performance of the battery. In particular, the trivalent boron atom in the borate ester additive has an empty P orbital, which is expressed as Lewis acidic overall, and can coordinate with anions to increase the transport rate of lithium / sodium ions. It can also coordinate with oxygen atoms in ether-based organic solvent molecules to reduce the charge density of oxygen in the solvent molecules, increase the solvent oxidation potential, and further resist oxidation of the ether-based electrolyte by positive electrode oxides.

[0062] The secondary battery of this application may be a lithium-ion secondary battery or a sodium-ion secondary battery. In some embodiments, the secondary battery is a sodium-ion secondary battery.

[0063] The sodium-ion secondary battery described above may be a typical sodium-ion secondary battery with a negative electrode, or a sodium-ion secondary battery without a negative electrode. The negative electrode in a typical sodium-ion secondary battery with a negative electrode may be a typical sodium metal negative electrode. To obtain an even higher battery core energy density, sodium-ion secondary batteries without a negative electrode, in which the positive electrode material is desodiumized and deposited in situ onto the negative electrode current collector, are also being studied.

[0064] A sodium secondary battery without a negative electrode is a battery constructed in which the negative electrode active material layer is not spontaneously installed on the negative electrode side during the battery manufacturing process. For example, the negative electrode active material layer is formed without installing a sodium metal or carbonaceous active material layer on the negative electrode through processes such as coating or deposition during the battery manufacturing process. During the initial charge, sodium ions gain electrons on the negative electrode side, and metallic sodium deposits on the current collector surface to form a sodium metallic phase. During discharge, the metallic sodium is converted back into sodium ions and returns to the positive electrode, enabling cycle charging and discharging. Compared to other sodium secondary batteries, a sodium secondary battery without a negative electrode can achieve a higher energy density because it lacks a negative electrode active material layer.

[0065] In some embodiments, to improve battery performance, several common materials that can be used as negative electrode active materials, such as carbonaceous materials, metal oxides, and alloys, may be placed on the negative electrode side of a sodium secondary battery without a negative electrode. Although these materials have a certain capacity, they are not used as the main negative electrode active material in the battery because the amount of these materials is small (if a carbonaceous material is used, this carbonaceous material is considered to be a conductive material), and a negative electrode active material layer that performs the function of sodium insertion is not formed (for example, a conductive layer is formed), and a sodium secondary battery configured in this way may still be considered a sodium secondary battery without a negative electrode.

[0066] In some embodiments, the CB value of a sodium secondary battery without a negative electrode is 0.1 or less. The CB value is calculated by dividing the capacity per unit area of ​​the negative electrode plate in a secondary battery by the capacity per unit area of ​​the positive electrode plate. Since a battery without a negative electrode contains no negative electrode active material or only a small amount of negative electrode active material, the capacity per unit area of ​​the negative electrode plate is relatively small, and the CB value of the secondary battery is 0.1 or less.

[0067] In some embodiments of this application, the secondary battery is selectively a sodium metal secondary battery without a negative electrode.

[0068] [Negative electrode current collector] In some embodiments of this application, the negative electrode current collector includes a conductive substrate and a selective conductive layer, the conductive layer being provided on at least one side of the conductive substrate. In some embodiments, the conductive layer is provided on one surface or two opposing surfaces of the conductive substrate. The selective conductive layer indicates that a conductive layer may or may not be provided.

[0069] When a negative electrode current collector is used as the negative electrode in a sodium secondary battery without a negative electrode, it is necessary to deposit sodium metal on the negative electrode current collector after the initial charge to form the negative electrode plate. Therefore, post-generation of sodium metal can more effectively mitigate problems caused by the reaction between sodium metal and the electrolyte.

[0070] In some embodiments, the conductive substrate includes one of bare copper, aluminum foil, aluminum alloy foil, and an aluminum-based composite current collector. The aluminum-based composite current collector includes a polymer base film and aluminum foil and / or aluminum alloy foil formed on both sides of the polymer base film. Specifically, the aluminum-based composite current collector has a "sandwich" structure, where the polymer base film is located in the center and aluminum foil is provided on both sides thereof, or aluminum alloy foil is provided on both sides thereof, or aluminum foil may be provided on one side of the polymer base film and aluminum alloy foil on the other side. The polymer base film includes one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polychloroethylene, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylethylene, polyformaldehyde, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate. Aluminum-based composite current collectors have better ductility and are advantageous for maintaining electrode integrity during the sodium metal deposition / exfoliation process.

[0071] In some embodiments, the conductive layer comprises a conductive agent and an adhesive, and more selectively, the conductive agent comprises one or more of conductive carbon, conductive polymers, and conductive ceramic materials. Here, conductive carbon includes, but is not limited to, graphite, graphene, carbon fibers, carbon black, carbon dots, soft carbon, hard carbon, multi-walled carbon nanotubes, or single-walled carbon nanotubes.

[0072] In some embodiments, the conductive layer further selectively includes an adhesive. For example, the adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0073] In some embodiments, a negative electrode current collector can be manufactured by the following method. Components for manufacturing the negative electrode current collector, such as a conductive agent, an adhesive, and any other component, are dispersed in a solvent (e.g., deionized water) to form a conductive slurry. The conductive slurry is then coated onto a substrate, and after processes such as drying and cold pressing, a negative electrode current collector is obtained.

[0074] [Electrolyte] The electrolyte according to some embodiments of this application comprises a non-aqueous solvent, an electrolyte salt, and an additive, wherein the non-aqueous solvent comprises an ether-based organic solvent, and the additive comprises a first additive, the first additive comprising one or more of a phosphite ester-based additive or a borate ester-based additive.

[0075] In some embodiments of this application, when the secondary battery is a sodium-ion secondary battery, sodium metal has extremely high chemical activity and reacts violently with the electrolyte to form a solid electrolyte interface film, thus facing significant challenges in the practical application of sodium metal anodes. For example, carbonate-based additives in common electrolytes, including FEC, DFEC, and VC, preferentially react with the sodium metal anode during the charging process, making it difficult to form an effective protective layer on the positive electrode surface and reducing the battery's cycle stability. Combining common ether-based electrolytes with sodium salts can achieve highly reversible sodium metal deposition / detachment efficiency. However, the upper limit of the voltage window of the ether-based electrolyte itself is relatively low, and especially when matched with a layered oxide cathode with a relatively high proportion of transition metal elements, the catalytic action of the surface transition metal elements further intensifies the decomposition of the ether-based electrolyte. On the other hand, during the charging process, the products generated by the oxidative decomposition of the ether-based electrolyte (mainly the solvent within it) at the positive electrode move to the sodium metal anode, where a reduction reaction occurs, and the products return to the positive electrode and are oxidized. The reciprocating oxidation-reduction transfer that occurs in ether-based electrolytes significantly reduces the energy conversion efficiency of sodium-ion secondary batteries and further affects their cycle performance. Furthermore, studies have shown that oxidative decomposition of the ether-based electrolyte at the positive electrode causes the actual charge capacity of the sodium-ion secondary battery to exceed its design capacity, resulting in capacity overcharging, which, when embodied in a sodium-ion secondary battery, reduces the Coulomb efficiency of the battery.

[0076] The above electrolyte, by introducing the first additive into an ether-based organic solvent system, allows the first additive to form a film on the positive electrode surface, effectively reducing oxidative decomposition of the ether-based electrolyte on the positive electrode surface and decreasing the reciprocal movement of oxidative decomposition products between the positive and negative electrodes. Furthermore, the first additive is relatively stable with respect to sodium metal and preferentially undergoes oxidative decomposition on the oxide positive electrode surface to form a CEI film containing boron or phosphorus compounds, thereby suppressing oxidative decomposition of the ether-based electrolyte on the positive electrode surface while simultaneously protecting the positive electrode structure from destruction, and further improving the Coulomb efficiency and cycle performance of the battery. In particular, the trivalent boron atom in the borate ester additive has an empty P orbital, which is expressed as Lewis acidic overall, and can coordinate with anions to increase the transport rate of lithium / sodium ions. It can also coordinate with oxygen atoms in the ether-based organic solvent molecule to reduce the charge density of oxygen in the solvent molecule, increase the solvent oxidation potential, and further resist oxidation of the ether-based electrolyte by the positive electrode oxide.

[0077] The ether-based organic solvent of this application may be selected from commonly used ether-based organic solvents in electrolytes, and in some embodiments, the ether-based organic solvent includes one or more of ethylene glycol diethyl ether (DEE), ethylene glycol dimethyl ether (DME, 1,2-dimethoxyethane), diethylene glycol dimethyl ether (DEGDME, diethylene glycol dimethyl ether), tetraethylene glycol dimethyl ether (TEGDME), triethylene glycol dimethyl ether (TRGDME), ethylene glycol ethyl methyl ether, ethylene glycol dibutyl ether (DBE), 1,3-dioxolane (DOL), 1,4-dioxane (1,4-dioxane), tetrahydrofuran (THF), or methyltetrahydrofuran. Each of the above ether-based organic solvents has a stable chemical structure, good fluidity, and good solubility of additives.

[0078] The antioxidant properties of a solvent in an electrolyte are determined by the interaction between the solvent molecule and anions. In the above-mentioned ether-based organic solvent, the interaction between ethylene glycol diethyl ether and anions is weakened, resulting in stronger oxidation resistance. In some embodiments, the ether-based organic solvent selectively contains ethylene glycol diethyl ether. By controlling the proportion of ethylene glycol diethyl ether in the electrolyte, the oxidation resistance of the electrolyte to the positive electrode active material can be more effectively enhanced, capacity overcharging during battery charging can be more effectively suppressed, and the stability of the battery to the high-voltage positive electrode and the Coulomb efficiency of the battery can be improved. Therefore, the mass content of ethylene glycol diethyl ether in the electrolyte is selectively 30% or more, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%, and selectively 40% to 65%.

[0079] The phosphite ester additive used in this application may be a general phosphite ester additive for electrolytes, and in some embodiments, the phosphite ester additive includes one or more of tris(trimethylsilane) phosphite (TMSP), trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, or triphenyl phosphite. The phosphite ester additive more efficiently oxidizes and decomposes on the oxide cathode surface to form a CEI film containing phosphorus compounds, thereby more reliably suppressing oxidative decomposition of the ether-based electrolyte on the cathode surface while simultaneously protecting the cathode structure from destruction.

[0080] The borate ester additive used in this application may be a general borate ester additive for electrolytes, and in some embodiments, the borate ester additive includes one or more of tris(trimethylsilane)borate (TMSB), trimethylborate (TMB), triethylborate (TEB), tripropylborate (TPB), tributylborate (TBB), or triphenylborate. The borate ester additive more efficiently oxidizes and decomposes on the oxide cathode surface to form a CEI film containing boron compounds, thereby more reliably suppressing oxidative decomposition of the ether-based electrolyte on the cathode surface while protecting the cathode structure from destruction.

[0081] In some embodiments, the first additive comprises tris(trimethylsilane)phosphite and / or tris(trimethylsilane)borate. When either of the two substances is used as the first additive, the resulting CEI film is more stable and the protective effect on the cathode structure is more pronounced.

[0082] In some embodiments, the mass content of the first additive in the electrolyte is 0.2% to 5%, for example, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, and selectively 0.2% to 3%. By utilizing the first additive, a sufficient CEI film can be formed, providing protection to the positive electrode, while avoiding an increase in internal resistance due to excessive CEI film thickness, which would affect the battery's overcharge performance.

[0083] When the electrolyte of this application is applied to a sodium metal battery system, sodium metal has extremely high chemical activity and reacts violently with the electrolyte on the negative electrode side, easily generating a solid electrolyte interface film. This reduces the battery's efficiency and cycle life. Furthermore, this interface film is unstable, and during the cycling process, as the sodium metal deposits and peels off, this interface film is constantly ruptured and reconstructed, continuously increasing the battery's internal resistance.

[0084] To solve the above problems, in some embodiments, the additive further comprises a second additive, the second additive comprising a C2-C7 fluoroalkyl ether additive. By introducing the second additive into the electrolyte, the second additive forms a film on the negative electrode surface, effectively reducing the reduction of products generated by the oxidative decomposition of the ether electrolyte on the positive electrode surface, and further suppressing the reciprocal movement of these products between the positive and negative electrodes. Furthermore, the reaction between the second additive and sodium metal is relatively weak, and the inorganic SEI components such as NaF generated by the reaction disperse on the negative electrode and form a film. This formed SEI film effectively suppresses the reciprocal movement of the products of the oxidative decomposition of the ether electrolyte between the positive and negative electrodes, thereby more effectively suppressing capacity overcharging, further increasing the Coulomb efficiency of the battery, and further improving the battery's cycle performance.

[0085] In some embodiments, the C2-C7 fluoroalkyl ether additives used in this application include 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, and 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoro This includes, but is not limited to, one or more of the following: ethyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1,1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, or 2,2,2-trifluoroethyl ethyl ether.

[0086] The reaction between each of the above C2-C7 fluoroalkyl ether additives and sodium metal is relatively weak, and the inorganic SEI components such as NaF generated by the reaction are dispersed on the negative electrode, more effectively suppressing the reciprocal movement of oxidative decomposition products of the ether electrolyte between the positive and negative electrodes, thereby better suppressing capacity overcharging and further improving the Coulombic efficiency of the battery.

[0087] One of the main functions of the above C2-C7 fluoroalkyl ether additives is to form an SEI film on the negative electrode. Therefore, the higher the activity of forming the film, the more advantageous it is for SEI film formation. However, the higher the activity of forming the film, the greater the consumption of negative electrode capacity. Therefore, in order to achieve both high cycle performance and high capacity maintenance characteristics of the secondary battery, in some embodiments, the above C2-C7 fluoroalkyl ether additives are selectively one or more of methyl nonafluorobutyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0088] The amount of the second additive used in the electrolyte can be determined by referring to conventional techniques. In some embodiments, the mass content of the second additive in the electrolyte is 0.2% to 5%, for example, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, and selectively 0.2% to 2%. By using the second additive, a sufficient SEI film can be formed, providing protection to the negative electrode, while avoiding an increase in internal resistance due to excessive SEI film thickness, which would affect the improvement of the battery's overcharge performance.

[0089] The electrolyte salt used in this application may be selected from electrolyte salts commonly used in general secondary batteries. For example, in some embodiments, when the secondary battery is a lithium-ion secondary battery, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0090] In some embodiments, when the electrolyte is used in a sodium-ion secondary battery, the electrolyte salt includes one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium hexafluoroarsenate (NaAsF6), sodium trifluoroacetate (CF3COONa), sodium trifluoromethanesulfonate (CF3NaO3S, NaOTf), and sodium tetraphenylborate (NaBPh4).

[0091] Here, sodium trifluoromethanesulfonate has relatively high solubility in ether-based organic solvents at low temperatures, and the efficiency of sodium metal deposition and detachment is relatively high, giving the battery relatively good cycle performance at low temperatures (for example, below -30°C). At room temperature, the side reaction between sodium trifluoromethanesulfonate and the sodium metal anode becomes vigorous, worsening the overall cycle performance of the battery. By using other electrolyte salts in the electrolyte, the cycle performance of the secondary battery at room temperature can be improved.

[0092] In some embodiments, the electrolyte selectively comprises a first sodium salt and sodium trifluoromethanesulfonate, wherein the first sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, or sodium hexafluoroarsenate. This enhances the low-temperature and room-temperature cycling performance of secondary batteries having this electrolyte.

[0093] In some embodiments, the mass content of sodium trifluoromethanesulfonate in the electrolyte is selectively 2% to 10%, for example 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, and selectively 2% to 5%. The mass content of the first sodium salt in the electrolyte is selectively 3% to 40%, for example 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40%, and selectively 5% to 30%.

[0094] When the electrolyte of this application contains sodium trifluoromethanesulfonate, sodium trifluoromethanesulfonate (NaOTf) has relatively high solubility in diethylene glycol dimethyl ether at low temperatures. To further increase the ionic conductivity of the electrolyte at low temperatures, in some embodiments, the ether-based organic solvent selectively contains diethylene glycol dimethyl ether. Furthermore, the mass content of diethylene glycol dimethyl ether in the electrolyte is selectively 20% or more, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and selectively 25% to 40%. Of course, if the electrolyte does not contain sodium trifluoromethanesulfonate, the ether-based organic solvent may contain diethylene glycol dimethyl ether.

[0095] In some embodiments, the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, for example 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, and selectively, the mass content of the first sodium salt in the electrolyte is 3% to 40%, for example 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40%, selectively 5% to 30%, thereby better improving the low-temperature and room-temperature cycle performance of the secondary battery.

[0096] In some embodiments, to further improve the ionic conductivity of the electrolyte at low temperatures, the mass ratio of sodium trifluoromethanesulfonate to diethylene glycol dimethyl ether is selectively set to X, where 0.05 ≤ X ≤ 0.2, for example, the minimum value of X may be 0.05, 0.08, or 0.1, and the maximum value of X may be 0.12, 0.125, 0.13, 0.15, 0.17, or 0.2, and selectively 0.1 ≤ X ≤ 0.13. This improves the low-temperature cycle performance of the battery.

[0097] [Positive electrode plate] The positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer contains a positive electrode active material.

[0098] As an example, the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on either one or both of the two opposing surfaces of the positive electrode current collector.

[0099] In some embodiments, the positive electrode current collector may employ a metal foil sheet or a composite current collector. For example, as the metal foil sheet, an aluminum foil may be employed. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as substrates of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0100] When the secondary battery is a sodium ion secondary battery, the positive electrode active material of the positive electrode plate is a layered metal oxide. In some embodiments, the above positive electrode active material has a chemical formula of Na x Mn a Q b O 2-c-d F c and includes one or more selected from the group consisting of oxides, where 0.5 < x ≤ 1, 0 < a, 0 < b, 0 ≤ c ≤ 0.2, -0.1 ≤ d ≤ 0.1, and Q includes one or more of the elements Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi. For example, NaNi<00000!1>Fe<{ 1 / 3 Mn 1 / 3 O2.

[0101] In some embodiments, the positive electrode film layer further selectively includes an adhesive. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0102] In some embodiments, the positive electrode film layer further selectively includes a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, a positive electrode plate can be manufactured by the following method. Components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and any other component, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode plate is obtained.

[0104] [Separator] In some embodiments, the secondary battery further includes a separator. This application does not particularly limit the type of separator, and any known porous separator having good chemical and mechanical stability may be selected.

[0105] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and is not particularly limited.

[0106] In some embodiments, the positive electrode plate, negative electrode plate, and separator can be manufactured into an electrode assembly by a winding process or a lamination process.

[0107] In some embodiments, the secondary battery may include a secondary battery cell, a battery module, or a battery pack, and may also include an outer casing. This outer casing may be used to package the electrode assembly and electrolyte.

[0108] In some embodiments, the casing of the secondary battery may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0109] This application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular secondary battery cell 5 as an example.

[0110] In some embodiments, referring to Figure 2, the casing may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing and forming a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening so as to seal the housing cavity. The positive electrode plate, negative electrode plate and separator can form an electrode assembly 52 by a winding or lamination process. The electrode assembly 52 is packaged within the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery cell 5 may be one or more, and those skilled in the art can specifically select according to their actual needs.

[0111] In some embodiments, the secondary battery cells may be assembled into a battery module, and the number of secondary battery cells included in the battery module may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0112] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, the multiple secondary battery cells 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary battery cells 5 may be fixed in place with fasteners.

[0113] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of secondary battery cells 5 are housed.

[0114] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0115] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, the upper housing 2 covering the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0116] Furthermore, this application provides a power consumption device, the power consumption device including a sodium-ion secondary battery according to this application. The sodium-ion secondary battery may be used as a power source for the power consumption device, or as an energy storage unit for the power consumption device. The power consumption device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0117] As the power consumption device, a specific type of secondary battery, such as a secondary battery cell, battery module, or battery pack, can be selected according to the usage requirements.

[0118] Figure 6 shows an example of a power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high output and high energy density of the secondary battery of this power consumption device, a battery pack or battery module may be used. [Examples]

[0119] [Examples] Examples of the present application are described below. The examples described below are illustrative and are used solely for the purpose of interpreting this application and should not be understood as limitations thereon. Unless otherwise specified in the examples, specific techniques or conditions are followed in accordance with the techniques, conditions, or product specifications described in the literature in the art. Unless otherwise specified, the reagents or equipment used are all commonly available commercial products.

[0120] Example 1 1) Electrolyte In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), sodium trifluoromethanesulfonate (NaOTf) and sodium hexafluorophosphate (NaPF6) were dissolved in diethylene glycol dimethyl ether and ethylene glycol diethyl ether (DEE) according to the electrolyte formulation of Example 1. Tris(trimethylsilane) phosphite and methyl nonafluorobutyl ether were added and the mixture was stirred and mixed uniformly to produce the electrolyte.

[0121] 2) Manufacturing of positive electrode plates NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, polyvinylidene fluoride (PVDF) as an adhesive, and conductive carbon black (Super-P) as a conductive agent are uniformly mixed in N-methylpyrrolidone (NMP) solvent in a mass ratio of 96:2:2 to produce a positive electrode slurry. This slurry is then applied to the surface of aluminum foil using a squeeze coater according to the mass requirement per unit area of ​​the positive electrode active material, dried, and then the coated electrode plate is pressed using a cold press at a density of 2.5 g / cm². 3 The final positive electrode plate was obtained by cold pressing and manufacturing using the design compaction method.

[0122] 3) Manufacturing of the negative electrode current collector Single-walled carbon nanotubes and sodium alginate are added to deionized water and stirred to form a uniform slurry. The slurry is then coated onto aluminum foil and dried to form a conductive layer, which is then cut to obtain a negative electrode current collector with a negative electrode-less structure. Here, the surface density of the conductive layer is 25 g / m². 2 That is the case.

[0123] 4) Separator A polypropylene film was used as the separator.

[0124] 5) Battery manufacturing The positive electrode plate, separator, and negative electrode current collector were wound or stacked in order, with the separator positioned between the positive electrode plate and the negative electrode current collector to provide isolation. Tabs were welded to the bare battery core, the bare battery core was placed in an aluminum case, and after firing at 80°C to remove water, the electrolyte was injected and sealed to obtain an uncharged battery. The uncharged battery was then subjected to a series of processes including standing, hot and cold pressing, chemical conversion, shaping, and capacity testing to obtain the sodium secondary battery product of Example 1.

[0125] The electrolyte compositions for Examples 2-30 and Comparative Examples 1-3 are shown in Table 1, and are otherwise the same as those for Example 1.

[0126] [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5] [Table 1-6]

[0127] test: 1) Mean Coulomb Efficiency Test At 25°C and normal pressure (0.1 MPa), the battery was charged with a constant current at a 0.1C multiplier until it reached 3.8V. The charged capacity at this time was defined as the battery's charge capacity. After standing for 5 minutes, it was discharged with a constant current at a 0.1C multiplier until the voltage reached 2.2V, and then stood for another 5 minutes. The discharge capacity at this time was defined as the battery's discharge capacity. The battery's Coulomb efficiency (%) = discharge capacity / charge capacity × 100%. After 400 charge-discharge cycles, the average Coulomb efficiency of the battery was calculated.

[0128] 2) Room temperature cycle performance At 25°C and normal pressure (0.1 MPa), the battery was charged with a constant current of 0.1C until the voltage reached 3.8V, and then discharged with a constant current of 0.1C until the voltage reached 2.2V. This constituted one charge-discharge cycle. The capacity after the initial discharge was set to 100%, and the charge-discharge cycle was repeated 400 times. After stopping the test, the cycle capacity retention rate was recorded, and the room-temperature capacity retention rate was used as an indicator to evaluate the battery's room-temperature cycle performance.

[0129] 3) Low-temperature cycle performance At -30°C and normal pressure (0.1 MPa), the battery was charged with a constant current of 0.1C until the voltage reached 3.8V, and then discharged with a constant current of 0.1C until the voltage reached 2.2V. This constituted one charge-discharge cycle. The capacity after the initial discharge was set to 100%, and the charge-discharge cycle was repeated 200 times. After stopping the test, the cycle capacity retention rate was recorded, and the low-temperature capacity retention rate was used as an indicator to evaluate the battery's low-temperature cycle performance.

[0130] The test results are recorded in Table 2.

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

[0132] As can be seen from the data comparison between the Examples and Comparative Examples 1-3, the combination of the first additive, the second additive, and the ether-based organic solvent in the electrolyte of this application had a clear effect in improving the low-temperature cycle performance, room-temperature cycle performance, and Coulomb efficiency (which explains that the higher the Coulomb efficiency, the more significantly the improvement in capacity overcharging) of the sodium battery.

[0133] As can be seen from the data comparison of Examples 1-5, changes in the amount of the first additive directly affected the low-temperature and room-temperature cycle performance of the battery, but the Coulomb efficiency hardly changed. Whether the amount of the first additive was too low (Example 5) or too high (Example 3), it led to a decrease in both low-temperature and room-temperature cycle performance. This may be because when the amount of the first additive was too low, the resulting CEI film was insufficient, resulting in inadequate protection of the positive electrode and further affecting cycle performance, while when the amount of the first additive was too high, the resulting CEI film was too thick, increasing the internal resistance of the positive electrode and further affecting cycle performance.

[0134] As can be seen from the data comparison between Example 1 and Examples 6-8, when tris(trimethylsilane) phosphite or tris(trimethylsilane) borate is selected as the first additive, the battery's cycle performance and Coulomb efficiency are particularly excellent.

[0135] As can be seen from the data comparison between Example 1 and Examples 9-12, when the amount of the second additive used changes, the low-temperature cycle performance, room-temperature cycle performance, and Coulomb efficiency are all affected, which explains that the second additive simultaneously affects the battery's cycle performance and capacity overcharge performance. In particular, regarding capacity overcharge performance, it was explained that within a certain usage range, as the amount of the second additive used increases, the Coulomb efficiency of the battery increases, and the improvement in battery capacity overcharge performance becomes apparent. However, when the amount of the second additive was increased from 2% to 5%, the Coulomb efficiency remained above 90%, but also showed a downward trend, and when it was continued to increase to 7%, the Coulomb efficiency showed a further downward trend.

[0136] As can be seen from the data comparison in Examples 1, 13-16, when different fluoroalkyl group additives were selected as the second additive, the battery's cycle performance and Coulomb efficiency differed in each case, but all of them had the effect of improving cycle performance and Coulomb efficiency.

[0137] As can be seen from the data comparison between Example 1 and Examples 17-21, firstly, the use of sodium trifluoromethanesulfonate is advantageous in improving the low-temperature cycle performance of the battery, and secondly, sodium trifluoromethanesulfonate had different effects on the low-temperature and room-temperature cycle performance of the battery. Within a certain usage range (e.g., less than 5%), with increasing the amount of sodium trifluoromethanesulfonate used, the low-temperature cycle performance clearly improved, but the room-temperature cycle performance slightly decreased. With further increases in the amount of sodium trifluoromethanesulfonate used (e.g., up to 10%), the low-temperature cycle performance did not improve, but the room-temperature cycle performance clearly decreased. This may be because sodium trifluoromethanesulfonate has relatively high solubility in ether-based organic solvents at low temperatures, and the Coulomb efficiency of sodium metal deposition and detachment is relatively high, giving the battery relatively good cycle performance at low temperatures (e.g., below -30°C). At room temperature, the reaction between sodium trifluoromethanesulfonate and the sodium metal anode became more vigorous, resulting in a deterioration of the overall battery cycle performance.

[0138] Furthermore, as can be seen from the data comparison of Example 1 and Examples 17-19, when the mass ratio of sodium trifluoromethanesulfonate to diethylene glycol dimethyl ether was increased within a certain range, the low-temperature cycle performance of the battery could also be improved. And as can be seen from the data comparison of Examples 22, 26, 29 and other examples, the amount of diethylene glycol dimethyl ether used had a significant effect on the low-temperature cycle performance of the battery. This may be because diethylene glycol dimethyl ether is an important solvent for dissolving sodium trifluoromethanesulfonate, and the effect of sodium trifluoromethanesulfonate in improving the low-temperature cycle performance of the battery can only be fully exerted when there is enough diethylene glycol dimethyl ether to sufficiently dissolve sodium trifluoromethanesulfonate. As can be seen from the data comparison of Examples 25, 27 and other examples, when diethylene glycol dimethyl ether was not included or its content was too low, the Coulomb efficiency of the battery became relatively low, the reaction products of the electrolyte increased, the battery decayed faster, and both the low-temperature cycle performance and the room-temperature cycle performance deteriorated.

[0139] As can be seen from the data comparison of Examples 1, 23, and 24, the composition of the sodium salt had a certain effect on the battery's cycle performance and Coulomb efficiency, but all of them were able to improve it.

[0140] As can be seen from the data comparison between Example 28 and the other examples and comparative examples, the second additive has a clear effect on both the battery's cycle performance and Coulomb efficiency. Without the second additive, the cycle performance and Coulomb efficiency of Example 28 were clearly improved compared to the corresponding performance of Comparative Examples 2 and 3, depending on the combination of the first additive and other components. After continuing to add the second additive, Example 1's low-temperature cycle, high-temperature cycle, and Coulomb efficiency all increased significantly compared to Example 28.

[0141] Furthermore, it should be explained that the Coulomb efficiency of Examples 28 and 29 was not as good as that of Comparative Example 1 because a second additive was used in Comparative Example 1, and that the second additive could better improve the capacity overcharge effect. However, the cycle performance of Examples 28 and 29 was still relatively good, and it was explained that the first additive could better improve the effect of cycle performance (it also had the effect of improving Coulomb efficiency, but the improvement in cycle performance was more evident).

[0142] As can be seen from the data comparison of Example 1, Example 25, and Example 30, when ethylene glycol diethyl ether was replaced with an equal amount of diethylene glycol dimethyl ether or ethylene glycol dimethyl ether, the oxidation resistance of these two substances was not as good as that of ethylene glycol diethyl ether. Therefore, the cycle performance and Coulomb efficiency of both Example 25 and Example 30 were not as good as that of Example 1.

[0143] While this application has been described with reference to preferred embodiments, various improvements can be made thereto, and components therein can be replaced with equivalents, without departing from the scope of this application. In particular, each technical feature referred to in each embodiment can be combined in any manner, provided that no structural conflicts exist. This application is not limited to the specific embodiments disclosed herein, but includes all technical ideas that fall within the scope of the claims. [Explanation of Symbols]

[0144] 1. Battery pack, 2. Upper casing, 3. Lower casing, 4. Battery module, 5. Secondary battery cell, 5. Case, 5. Electrode assembly, 5. Cover plate.

Claims

1. A secondary battery comprising a positive electrode plate, an electrolyte, a separator, and a negative electrode current collector, wherein the electrolyte comprises a non-aqueous solvent, an electrolyte salt, and an additive, the non-aqueous solvent comprises an ether-based organic solvent, and the additive is A secondary battery comprising a first additive, wherein the first additive comprises one or more of a phosphite ester-based additive or a borate ester-based additive.

2. The secondary battery according to claim 1, wherein the secondary battery is a sodium-ion secondary battery, and selectively, the secondary battery is a sodium secondary battery without a negative electrode, and selectively, the negative electrode current collector comprises a conductive substrate and a selective conductive layer, the conductive layer is provided on at least one side of the conductive substrate, the conductive substrate comprises one of bare copper, aluminum foil, aluminum alloy foil, and aluminum-based composite current collector, and selectively, the conductive layer comprises a conductive agent and an adhesive, and further selectively, the conductive agent comprises graphite, graphene, carbon fiber, carbon black, carbon dots, soft carbon, hard carbon, multilayer carbon nanotubes, or single-walled carbon nanotubes.

3. The ether-based organic solvent comprises one or more of ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, ethylene glycol ethyl methyl ether, ethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, or methyltetrahydrofuran, and selectively the ether-based organic solvent contains ethylene glycol diethyl ether and / or diethylene glycol dimethyl ether, and selectively the mass content of ethylene glycol diethyl ether in the electrolyte is 30% or more, selectively 40% to 65%, and selectively the mass content of diethylene glycol dimethyl ether in the electrolyte is 20% or more, selectively 25% to 40%, as described in claim 1 or 2.

4. The secondary battery according to any one of claims 1 to 3, wherein the phosphite ester additive comprises one or more of tris(trimethylsilane) phosphite, trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, or triphenyl phosphite.

5. The secondary battery according to any one of claims 1 to 4, wherein the boric acid ester additive comprises one or more of tris(trimethylsilane)borate, trimethylborate, triethylborate, tripropylborate, tributylborate, or triphenylborate.

6. The secondary battery according to any one of claims 1 to 5, wherein the first additive comprises tris(trimethylsilane) phosphite and / or tris(trimethylsilane) borate, and / or the mass content of the first additive in the electrolyte is 0.2% to 5%, and selectively 0.2% to 3%.

7. The secondary battery according to claim 1 or 2, wherein the additive further comprises a second additive, the second additive comprising a C2-C7 fluoroalkyl ether additive.

8. The aforementioned C2-C7 fluoroalkyl ether additives are 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2 The secondary battery according to claim 7, comprising one or more of the following: 3,3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1,1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, or 2,2,2-trifluoroethyl ethyl ether.

9. The secondary battery according to claim 7 or 8, wherein the mass content of the second additive in the electrolyte is 0.2% to 5%, and selectively 0.2% to 2%.

10. The secondary battery according to any one of claims 1 to 9, wherein the electrolyte salt comprises an electrolyte sodium salt, and selectively comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium trifluoroacetate, sodium trifluoromethanesulfonate, or sodium tetraphenylborate, and selectively comprises a first sodium salt and sodium trifluoromethanesulfonate, and the first sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, or sodium hexafluoroarsenate, and selectively the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, and selectively the mass content of the first sodium salt in the electrolyte is 3% to 40%, and selectively 5% to 30%.

11. The secondary battery according to any one of claims 3 to 9, wherein the electrolyte salt comprises a first sodium salt and sodium trifluoromethanesulfonate, the first sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, or sodium hexafluoroarsenate, selectively the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, selectively the mass content of the first sodium salt in the electrolyte is 3% to 40%, selectively 5% to 30%, and selectively the mass ratio of sodium trifluoromethanesulfonate to diethylene glycol dimethyl ether is X, such that 0.05 ≤ X ≤ 0.2, and selectively 0.1 ≤ X ≤ 0.

13.

12. The positive electrode active material of the positive electrode plate is a layered metal oxide, and selectively, the positive electrode active material has the chemical formula Na ｘ Mn ａ Q ｂ O ２－ｃ－ｄ F ｃ A secondary battery according to any one of claims 1 to 11, comprising one or more oxides of the following, where 0.5 < x ≤ 1, 0 < a, 0 < b, 0 ≤ c ≤ 0.2, -0.1 ≤ d ≤ 0.1, and Q comprising one or more elements from Li, B, Mg, Al, Si, K, Ca, Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, In, Sn, Sb, La, Ce, Ta, W, and Bi.

13. An electrolyte comprising a non-aqueous solvent, an electrolyte salt, and an additive, wherein the non-aqueous solvent comprises an ether-based organic solvent, and the additive is An electrolyte comprising a first additive, wherein the first additive comprises one or more of a phosphite ester-based additive or a borate ester-based additive.

14. The ether-based organic solvent comprises one or more of ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, ethylene glycol ethyl methyl ether, ethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, or methyltetrahydrofuran, and selectively the ether-based organic solvent contains ethylene glycol diethyl ether and / or diethylene glycol dimethyl ether, and selectively the mass content of ethylene glycol diethyl ether in the electrolyte is 30% or more, selectively 40% to 65%, and selectively the mass content of diethylene glycol dimethyl ether in the electrolyte is 20% or more, selectively 25% to 40%, as described in claim 13.

15. The electrolyte according to claim 13 or 14, wherein the phosphite ester additive comprises one or more of tris(trimethylsilane) phosphite, trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, or triphenyl phosphite.

16. The electrolyte according to any one of claims 13 to 15, wherein the boric acid ester additive comprises one or more of tris(trimethylsilane)borate, trimethylborate, triethylborate, tripropylborate, tributylborate, or triphenylborate.

17. The electrolyte according to any one of claims 13 to 16, wherein the first additive comprises tris(trimethylsilane) phosphite and / or tris(trimethylsilane) borate, and / or the mass content of the first additive in the electrolyte is 0.2% to 5%, and selectively 0.2% to 3%.

18. The electrolyte according to any one of claims 13 to 17, wherein the additive further comprises a second additive, the second additive comprising a C2 to C7 fluoroalkyl ether additive.

19. The aforementioned C2-C7 fluoroalkyl ether additives are 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, difluoromethyl-2,2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2 The electrolyte according to claim 18, comprising one or more of the following: 3,3-tetrafluoropropyl difluoromethyl ether, 2,2,3,3-tetrafluoro-1-methoxypropane, 1,1,2,3,3,3-pentafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl perfluorobutyl ether, ethyl nonafluorobutyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, or 2,2,2-trifluoroethyl ethyl ether.

20. The electrolyte according to claim 18 or 19, wherein the mass content of the second additive in the electrolyte is 0.2% to 5%, and selectively 0.2% to 2%.

21. The electrolyte according to any one of claims 13 to 20, wherein the electrolyte salt comprises an electrolyte sodium salt, and selectively comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium trifluoroacetate, sodium trifluoromethanesulfonate, or sodium tetraphenylborate, and selectively comprises a first sodium salt and sodium trifluoromethanesulfonate, and the first sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, or sodium hexafluoroarsenate, and selectively the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, and selectively the mass content of the first sodium salt in the electrolyte is 3% to 40%, and selectively 5% to 30%.

22. The electrolyte according to any one of claims 14 to 20, wherein the electrolyte salt comprises a first sodium salt and sodium trifluoromethanesulfonate, the first sodium salt comprises one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, or sodium hexafluoroarsenate, selectively the mass content of sodium trifluoromethanesulfonate in the electrolyte is 2% to 10%, selectively the mass content of the first sodium salt in the electrolyte is 3% to 40%, selectively 5% to 30%, and selectively the mass ratio of sodium trifluoromethanesulfonate to diethylene glycol dimethyl ether is X, such that 0.05 ≤ X ≤ 0.2, and selectively 0.1 ≤ X ≤ 0.

13.

23. A power consumption device including a secondary battery, wherein the secondary battery is selected from the secondary batteries described in any one of claims 1 to 12.

Images