Electrolyte for sodium-ion battery, sodium-ion battery containing the same, and power consumption device

Abstract

This application provides an electrolyte for a sodium-ion battery. The electrolyte contains an ether-based compound as a solvent, a sodium borate-based compound as a sodium salt, and a borate ester-based compound as an additive. The proportion of the ether-based compound in the entire solvent of the electrolyte is 50% by weight or more. The electrolyte can suppress the volume expansion of the battery and the growth of sodium dendritic crystals. This application further provides a sodium-ion battery, a battery module, a battery pack, and an electric power consumption device containing the electrolyte.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to an electrolyte of a sodium-ion battery, a sodium-ion battery containing the same, and a battery module, a battery pack, and a power consumption device containing the sodium-ion battery.

Background Art

[0002] In recent years, the demand for lithium-ion batteries has been increasing steadily. However, the limited lithium resources restrict the sustainable development of lithium-ion batteries. As an important candidate for lithium-ion batteries, sodium-ion batteries have been attracting increasing attention.

[0003] After a sodium-ion battery undergoes multiple charge-discharge cycles, the volume of the battery may expand, and sodium dendrite growth may occur on the electrode. The volume expansion of the battery and the growth of sodium dendrites reduce the Coulomb efficiency of the battery, shorten the cycle life, and ultimately affect the safety performance of the battery. Conventional sodium-ion batteries still have room for improvement in the above aspects.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present application has been made in view of the above problems, and aims to reduce the volume expansion of a sodium-ion battery after cycling and suppress the formation of sodium dendrites on the electrode.

Means for Solving the Problems

[0005] To achieve the above object, a first aspect of the present application provides an electrolyte of a sodium-ion battery, the electrolyte containing an ether-based compound as a solvent, a sodium borate-based compound as a sodium salt, and a borate ester-based compound as an additive, wherein the proportion of the ether-based compound in the entire solvent of the electrolyte is 50% by weight or more.

[0006] Thereby, in the present application, a specific combination in the electrolyte can suppress volume expansion and sodium dendrite growth after cycling of the sodium-ion battery. Therefore, the sodium-ion battery containing the electrolyte has good Coulomb efficiency and cycle performance.

[0007] In any embodiment, the borate ester compound has the structure of the following formula (I),

Chemical formula

[0008] By further selecting the borate ester compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved.

[0009] In any embodiment, based on the total weight of the electrolyte, the content of the borate ester compound is 0.5 wt% to 10 wt%, optionally 1 wt% to 5 wt%, for example 2 wt%.

[0010] By further selecting the content of the borate ester compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved.

[0011] In any embodiment, the sodium borate compound is one or more selected from sodium difluoroborate and a compound having the structure of the following formula (II),

Chemical formula

[0012] By further selecting a sodium borate-based compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved.

[0013] In any embodiment, based on the total volume of the electrolyte, the concentration of the sodium borate-based compound is 0.5 M to 8 M, and optionally 1 M to 4 M.

[0014] By further selecting the content of the sodium borate-based compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved.

[0015] In any embodiment, the ether-based compound is one or more selected from aliphatic ethers having 4 to 20 carbon atoms, alicyclic ethers having 3 to 8 carbon atoms, aromatic ethers having 7 to 20 carbon atoms, and crown ethers. Optionally, the ether-based compound is one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether. More optionally, the ether-based compound is one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether.

[0016] By further selecting an ether-based compound, it contributes to suppressing sodium dendritic crystal growth and volume expansion of the battery.

[0017] In any embodiment, the proportion of the ether-based compound in the entire solvent of the electrolyte is 60% by weight or more, optionally 80% by weight or more. More optionally, the solvent consists of an ether-based compound.

[0018] By controlling the proportion of the ether-based compound in the entire solvent of the electrolyte, it contributes to suppressing sodium dendritic crystal growth and volume expansion of the battery.

[0019] The second aspect of the present application further provides a sodium-ion battery including the electrolyte according to the first aspect of the present application.

[0020] The third aspect of the present application provides a battery module including the sodium-ion battery according to the second aspect of the present application.

[0021] The fourth aspect of the present application provides a battery pack including the battery module according to the third aspect of the present application.

[0022] The fifth aspect of the present application provides a power consumption device including at least one selected from the sodium-ion battery according to the second aspect of the present application, the battery module according to the third aspect of the present application, or the battery pack according to the fourth aspect of the present application.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0024] Hereinafter, embodiments specifically disclosing the electrolyte of the sodium-ion battery of the present application, its manufacturing method, the sodium-ion battery, the battery module, the battery pack, and the electrical device will be described in detail with appropriate reference to the drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of substantially the same structures may be omitted. This is to avoid making the following description unnecessarily redundant and to enable those skilled in the art to easily understand. Also, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the gist described in the claims.

[0025] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit. A predetermined range is limited by selecting one lower limit and one upper limit, and the boundary of the predetermined range is limited by the selected lower limit and upper limit. The range thus limited may include both end values or may not include both end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form one range. For example, when ranges of 60 to 120 and 80 to 110 are listed for a certain parameter, ranges of 60 to 110 and 80 to 120 are also understood to be expected. Also, when 1 and 2 are listed as the values of the minimum range and 3, 4, and 5 are listed as the values of the maximum range, ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all predictable. In the present application, unless otherwise explained, the numerical range "a~b" represents an abbreviated expression of any combination of real numbers between a and b, and both a and b are real numbers. For example, the numerical range "0~5" means that all real numbers between "0~5" are listed in this specification, and "0~5" is simply an abbreviated expression of the combination of these numerical values. Note that when it is described that a certain parameter is an integer ≧2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specifically explained, all embodiments and alternative embodiments of the present application can be combined with each other to form new technical solutions.

[0027] Unless otherwise specified, all technical features of this application and optional technical features can be combined with each other to form new technical solutions.

[0028] Unless otherwise specified, all steps of this application may be performed in sequence or randomly, preferably in sequence. For example, when it is stated that the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), steps (a), (c), and (b), or steps (c), (a), and (b).

[0029] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application represent an open-ended form and may also be in a closed-ended form. For example, the "comprising" and "including" can represent that they may further comprise or include other components not listed, or may comprise or include only the listed components.

[0030] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any one of the conditions that A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist) satisfies the condition "A or B".

[0031] Sodium ion batteries may experience volume expansion of the battery and growth of sodium dendritic crystals on the electrodes after multiple charge-discharge cycles. The volume expansion of the battery and the growth of sodium dendritic crystals reduce the Coulombic efficiency of the battery, shorten the cycle life, and ultimately affect the safety performance of the battery. Therefore, there is a requirement for sodium ion batteries to reduce their volume expansion after cycling and suppress the formation of sodium dendritic crystals.

[0032] The applicant has found that when an ether-based compound is used as a solvent in the electrolyte of a sodium ion battery and the electrolyte contains a sodium borate-based compound and a borate ester-based compound simultaneously, the volume expansion of the obtained sodium ion battery is significantly reduced and the growth of sodium dendritic crystals is suppressed.

[0033] Therefore, in one embodiment of the present application, the present application provides an electrolyte for a sodium ion battery, the electrolyte comprising an ether-based compound as a solvent, a sodium borate-based compound as a sodium salt, and a borate ester-based compound as an additive, wherein the proportion of the ether-based compound in the entire solvent of the electrolyte is 50% by weight or more.

[0034] Although the mechanism is not yet clear, the applicant has surprisingly found in the present application that by including a large amount of an ether-based compound in the solvent of the electrolyte and adding a sodium borate-based compound and a borate ester-based compound to the electrolyte, the volume expansion of the sodium ion battery after multiple cycles can be significantly reduced and the growth of sodium dendritic crystals on the electrodes can be prevented. Without being bound by theory, it is speculated that the combination of the above substances forms a solid electrolyte interface (SEI) layer rich in inorganic borate on the surface of the electrode, and since the SEI layer has high mechanical stability, it suppresses volume expansion and the growth of sodium dendritic crystals. Therefore, the sodium ion battery containing the electrolyte has good Coulombic efficiency and cycle performance.

[0035] In some embodiments, the borate compound has the structure of the following formula (I), [Chemical formula] wherein R 1 , R 2 , R 3 are the same or different and are selected from an alkyl group, an aryl group, an alkylsilyl group, an alkenyl group, an alkynyl group, and a cyanoalkyl group, and the above groups are optionally substituted by a halogen, and optionally, the halogen is fluorine, and optionally, R 1 , R 2 , R 3 are the same or different and are selected from a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a C6-C12 aryl group, a C6-C12 halogenated aryl group, a C1-C6 alkylsilyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, and a cyano-C1-C6 alkyl group, and optionally, at least one of R 1 , R 2 and R 3 represents a C1-C6 fluoroalkyl group or a C6-C12 fluoroaryl group, Optionally, the borate compound is one or more selected from trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, tris(2,2,2-trifluoroethyl) borate, tris(hexafluoroisopropyl) borate, triphenyl borate, tris(trimethylsilyl) borate, tris(triethylsilyl) borate, tris(pentafluorophenyl) borate, (di-n-butyl)(vinyl) borate, (di-n-butyl)(propargyl) borate, tris(2-cyanoethyl) borate, and further optionally, the borate compound is one or more selected from trimethyl borate, triethyl borate, tripropyl borate, and tributyl borate. Borate compounds with particularly small molecules are advantageous.

[0036] By further selecting a borate compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved. In particular, when the borate compound contains fluorine, NaF in the SEI layer can further provide protection for the negative electrode.

[0037] In some embodiments, based on the total weight of the electrolyte, the content of the borate compound is 0.5 wt% to 10 wt%, optionally 1 wt% to 5 wt%, for example 2 wt% to 3 wt%.

[0038] By further selecting the content of the borate compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved.

[0039] In some embodiments, the sodium borate compound is one or more selected from sodium difluoroborate and a compound having the structure of the following formula (II),

Chemical formula

Chemical formula

[0040] By further selecting the sodium borate compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved. In particular, when the sodium borate compound contains fluorine, NaF in the SEI layer can further provide protection for the negative electrode.

[0041] In some embodiments, based on the total volume of the electrolyte, the concentration of the sodium borate compound is 0.5M to 8M, optionally 1M to 4M, for example 1M to 2M, for example 1.5M.

[0042] By further selecting the content of the sodium borate compound, the volume expansion of the battery can be further reduced, and the cycle performance and Coulomb efficiency of the battery can be improved.

[0043] In some embodiments, the ether compound is one or more selected from aliphatic ethers having 4 to 20 carbon atoms, alicyclic ethers having 3 to 8 carbon atoms, aromatic ethers having 7 to 20 carbon atoms, and crown ethers. Optionally, the ether compound is one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ethers. Further optionally, the ether compound is one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether.

[0044] By further selecting an ether compound, a stable electrode / electrolyte interface can be constructed on the surfaces of sodium metal anodes, carbon material anodes, and other non-carbon material anodes, a stable solid electrolyte interface (SEI) can be formed, electrochemical polarization can be reduced, and it contributes to suppressing sodium dendrite crystal growth and volume expansion of the battery.

[0045] In some embodiments, the proportion of the ether compound in the total solvent of the electrolyte is 60 wt% or more, or 70 wt% or more, optionally 80 wt% or more, for example 85 wt% or more, or 90 wt% or more, or 95 wt% or more, or 98 wt% or more. Further optionally, the solvent consists of an ether compound.

[0046] By controlling the proportion of the ether compound in the total solvent of the electrolyte, a stable electrode / electrolyte interface can be constructed on the anode surface, a stable solid electrolyte interface can be formed, which contributes to suppressing sodium dendrite crystal growth and volume expansion of the battery, and further improving the cycle performance and Coulomb efficiency of the battery.

[0047] As can be understood by those skilled in the art, in a sodium-ion battery, the electrolyte plays a role of conducting ions between the positive electrode plate and the negative electrode plate. The electrolyte contains an electrolyte salt and a solvent. In the sodium-ion battery of the present application, the electrolyte salt is a sodium salt.

[0048] The sodium borate-based compound itself can be used as an electrolyte salt. In some embodiments, in addition to the sodium borate-based compound, the electrolyte salt is NaClO 4 , NaPF 6 , NaBF 4 , NaTFSI (sodium bis(trifluoromethanesulfonyl)imide), NaFSI (sodium bis(fluorosulfonyl)imide), and may further include one or more substances selected therefrom. In some embodiments, based on the total volume of the electrolyte, the total molar concentration of the electrolyte salt is 0.5M to 8M, and optionally 1M to 4M.

[0049] In some embodiments, the solvent of the electrolyte, in addition to ether-based compounds, includes at least one solvent selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0050] In some embodiments, the electrolyte optionally further includes other additives. For example, the additives can include a negative electrode film-forming additive and a positive electrode film-forming additive, and can also include additives that can improve a predetermined performance of the battery, such as an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature performance or low-temperature performance of the battery.

[0051] Next, the sodium ion battery, battery module, battery pack, and power consumption device of the present application will be described with appropriate reference to the drawings hereinafter.

[0052] In one embodiment of the present application, a sodium ion battery including the electrolytic solution of the present application is provided.

[0053] Normally, a sodium ion battery includes a positive electrode plate, a negative electrode plate, an electrolytic solution, and a separator. During the charge and discharge process of the battery, active ions repeatedly insert and desorb between the positive electrode plate and the negative electrode plate. The electrolytic solution plays a role of conducting ions between the positive electrode plate and the negative electrode plate. The separator is provided between the positive electrode plate and the negative electrode plate, mainly plays a role of preventing short circuit between the positive and negative electrodes, and at the same time can allow ions to pass through.

[0054] [Positive Electrode Plate] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer contains a positive electrode active material.

[0055] As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0056] In some embodiments, as the positive electrode current collector, a conductive carbon plate, a metal foil material, a carbon-coated metal foil material, a porous metal plate, or a composite current collector can be employed. The conductive carbon material of the conductive carbon plate can be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphite, graphene, and carbon nanofiber. The metal materials of the metal foil material, the carbon-coated metal foil material, and the porous metal plate can each be independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector may be a composite current collector formed by the composite of a metal foil material and a polymer-based film.

[0057] The positive electrode current collector is, for example, one or more of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil, and it is preferable to employ aluminum foil.

[0058] In some embodiments, as the positive electrode active material, a positive electrode active material for a sodium ion battery known in the art can be employed. As an example, the positive electrode active material can include at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue-based compound. However, the present application is not limited to these materials.

[0059] Optionally, in the sodium transition metal oxide, the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na x MO 2 where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≦ 1.

[0060] Optionally, the polyanionic compound may be a compound having sodium ions, transition metal ions, and a tetrahedral (YO 4 ) n- anion unit. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n represents the valence state of (YO 4 ) n- .

[0061] The polyanionic compound may be a compound having sodium ions, transition metal ions, a tetrahedral (YO 4 ) n- anion unit, and halogen anions. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n represents the valence state of (YO 4 )n- represents the valence state of, and the halogen may be at least one of F, Cl, and Br.

[0062] The polyanionic compound may be a compound having sodium ions, a tetrahedral (YO 4 ) n- anion unit, a polyhedral unit (ZO y ) m+ and a selective halogen anion. Y may be at least one of P, S, and Si, n represents the valence state of (YO 4 ) n- , Z represents a transition metal, and may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. m represents the valence state of (ZO y ) m+ , and the halogen may be at least one of F, Cl, and Br.

[0063] The polyanionic compound may be, for example, NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , NaM’PO 4 F (M’ is one or more of V, Fe, Mn, and Ni) and Na 3 (VO y ) 2 (PO 4 ) 2 F 3-2y (0 ≦ y ≦ 1), or at least one of them.

[0064] The Prussian blue-based compound may be a compound having sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue-based compound may be, for example, Na a Me b Me’ c (CN) 6wherein Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, and 0 < a ≤ 2, 0 < b < 1, and 0 < c < 1.

[0065] In some embodiments, the positive electrode film layer optionally further comprises a binder. As an example, the binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene vinyl acetate copolymer (EVA), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0066] In some embodiments, the positive electrode film layer optionally further comprises a conductive agent. As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0067] In some embodiments, a positive electrode plate can be manufactured by the following method. Components for manufacturing the above-described positive electrode plate, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. After applying the positive electrode slurry to a positive electrode current collector and undergoing processes such as drying and cold pressing, a positive electrode plate can be obtained.

[0068] [Negative Electrode Plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer contains a negative electrode active material.

[0069] As an example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0070] In some embodiments, the negative electrode current collector includes, but is not limited to, a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a foamed nickel, a foamed copper, or a composite current collector coated with a conductive metal.

[0071] In some embodiments, the negative electrode active material includes at least one of graphite, sodium metal, sodium alloy, carbon black (hard carbon or soft carbon), silicon material, silicon oxygen material, tin material, tin oxygen material, or silicon carbon composite material.

[0072] In some embodiments, the negative electrode active material includes graphite. The graphite may be artificial graphite or natural graphite. In the case of graphite-based materials, sodium ions and ether-based compound molecules can undergo a highly reversible co-insertion reaction in graphite to form a stable graphite ternary intercalation compound, which contributes to enhancing the initial Coulombic efficiency and rate performance of the battery.

[0073] In some embodiments, the negative electrode film layer optionally further includes a binder. The binder includes, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylate-modified styrene butadiene rubber, epoxy resin, or nylon.

[0074] In some embodiments, the negative electrode film layer optionally further includes a conductive agent. The conductive agent can be selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder, metal fiber, copper, nickel, aluminum, silver, or polyphenylene derivative.

[0075] In some embodiments, the negative electrode film layer may further selectively include other auxiliaries such as, for example, a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0076] In some embodiments, the negative electrode plate can be manufactured by the following method. Components for manufacturing the above-described negative electrode plate, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. After applying the negative electrode slurry to a negative electrode current collector and undergoing processes such as drying and cold pressing, a negative electrode plate can be obtained.

[0077] [Separator] In some embodiments, the sodium ion battery further includes a separator. In the present application, there is no particular limitation on the type of the separator, and any known separator having a porous structure with good chemical stability and mechanical stability can be selected.

[0078] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0079] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be manufactured as an electrode assembly by a winding process or a lamination process.

[0080] In some embodiments, the sodium ion battery can include an exterior body. The exterior body can be used to package the above electrode assembly and electrolyte solution.

[0081] In some embodiments, the housing of the sodium-ion battery may be a rigid case such as a rigid plastic case, an aluminum case, or a steel case. The housing of the sodium-ion battery may also be a soft pack such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0082] In the present application, the shape of the sodium-ion battery is not particularly limited and may be cylindrical, square, or any other arbitrary shape. For example, FIG. 1 shows a sodium-ion battery 5 having a square structure as an example.

[0083] In some embodiments, referring to FIG. 2, the housing may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates surround to form a housing chamber. The case 51 has an opening communicating with the housing chamber, and the cover plate 53 can cover the opening so as to seal the housing chamber. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the housing chamber. The electrolytic solution infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the sodium-ion battery 5 may be one or more, and those skilled in the art can select according to specific actual requirements.

[0084] In some embodiments, the sodium-ion battery can be assembled into a battery module, and the number of sodium-ion batteries included in the battery module 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 module.

[0085] FIG. 3 shows a battery module 4 as an example. Referring to FIG. 3, in the battery module 4, a plurality of sodium-ion batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other arbitrary form. Further, the plurality of sodium-ion batteries 5 may be fixed by fastening members.

[0086] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of sodium-ion batteries 5 are accommodated in the accommodation space.

[0087] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0088] FIGS. 4 and 5 show a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper box 2 and a lower box 3. The upper box 2 covers the lower box 3 and can form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery box according to any form.

[0089] Furthermore, the present application further provides a power consumption device including at least one of the sodium ion battery, battery module, or battery pack provided by the present application. The sodium ion battery, battery module, or battery pack may be used as a power source of the power consumption device, or may be used as an energy storage unit of the power consumption device. The power consumption device may include, but is not limited to, mobile devices (e.g., mobile phones, notebook computers, etc.), electric vehicles (e.g., secondary battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric cars, ships, and satellites, energy storage systems, and the like.

[0090] As the power consumption device, a sodium ion battery, battery module, or battery pack can be selected according to the usage needs thereof.

[0091] FIG. 6 shows a power consumption device as an example. The power consumption device is, for example, a secondary battery electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements for high power and high energy density for the sodium ion battery of the power consumption device, a battery pack or a battery module can be adopted.

[0092] Another example of the device may be a mobile phone, a tablet, a notebook computer, etc. The device usually requires weight reduction and thinning, and a sodium ion battery can be adopted as a power source.

Examples

[0093] Hereinafter, examples of the present application will be described. The examples described below are illustrative and are merely for interpreting the present application, and should not be understood as limiting the present application. When specific technologies or conditions are not specified in the examples, they are carried out according to the technologies or conditions described in the literature in the relevant field or according to the product specifications. When the manufacturer of the reagents or equipment used is not specified, all are commercially available conventional products.

[0094] Example 1 [Manufacture of Positive Electrode Plate] 10 parts by weight of polyvinylidene fluoride as a binder was sufficiently dissolved in N-methylpyrrolidone, and 10 parts by weight of carbon black as a conductive agent and 80 parts by weight of Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) were added to prepare a uniformly dispersed slurry. The slurry was uniformly coated on the surface of an aluminum foil, and then transferred to a vacuum drying oven and completely dried. The obtained electrode plate was rolled and then punched to obtain a positive electrode plate. The load-bearing capacity of the positive electrode plate was 0.3 g / 1540.25 mm 2 .

[0095] [Manufacture of Negative Electrode Plate] First, the hard carbon material was put into a mixed solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1, stirred for 4 hours, washed with deionized water, filtered, and then put into an oven and baked at 80 °C. The carbon material and SBR (styrene-butadiene rubber) of the polymer after the above treatment were added to N-methylpyrrolidone at a weight ratio of 95:5, stirred to form a uniform slurry, the slurry was coated on a copper foil and baked to obtain a carbon material coating to be used, and the coating amount was 0.010 g / 1540.25 mm 2 .

[0096] In an argon gas atmosphere, sodium metal was put into a stainless steel crucible and heated to 200 °C until it was completely melted. Then, a powder of a sodium-bismuth alloy component was added to the liquid sodium metal and stirred sufficiently for 2 hours to ensure that the metal powder and the liquid sodium metal were uniformly mixed. After cooling, a sodium metal alloy active material could be obtained, and the content of bismuth in the sodium metal alloy active material was 5% by weight. The sodium metal alloy active material was compounded on the surface of the carbon material coating by cold pressing to obtain a negative electrode plate, and the load-bearing capacity of the sodium metal alloy active material was 0.025 g / 1540.25 mm 2 .

[0097] [Manufacture of Electrolyte Solution] In a glove box under an argon gas atmosphere (H 2 O < 0.1 ppm, O 2 < 0.1 ppm), sodium difluorooxalate borate and trimethyl borate were dissolved in ethylene glycol dimethyl ether as an organic solvent, stirred uniformly, and an electrolyte solution with a concentration of trimethyl borate of 2% by weight and a concentration of sodium difluorooxalate borate (NaDFOB) of 1.5 mol / L, that is, the electrolyte solution of Example 1, was obtained.

[0098] [Separator] A polypropylene membrane was used as the separator.

[0099] [Manufacture of Sodium Ion Battery] The above positive electrode plate, separator, and negative electrode plate were laminated in order, with the separator interposed between the positive and negative electrode plates, and the above electrolyte solution was added and assembled into a laminated battery.

[0100] Examples 2 to 33 Except for changing the formulation of the electrolyte solution as shown in Table 1, the other steps of Examples 2 to 33 are the same as those of Example 1.

[0101] Example 34 Except that the manufacture of the negative electrode plate was performed as follows, the other steps are the same as those of Example 1.

[0102] 5 parts by weight of the binder sodium carboxymethyl cellulose was sufficiently dissolved in deionized water, and 95 parts by weight of graphite was added and dispersed uniformly to prepare a slurry. The slurry was uniformly coated on the surface of a copper foil, and then transferred to a vacuum drying oven and completely dried. The obtained electrode plate was rolled and then punched to obtain a negative electrode plate. The load resistance of the negative electrode plate was 0.035 g / 1540.25 mm 2 and it was.

[0103] Comparative Examples 1 to 5 Except for changing the formulation of the electrolyte solution as shown in Table 1, the other steps of Comparative Examples 1 to 5 are the same as those of Example 1.

[0104] Battery Performance Test [Coulombic Efficiency] The sodium-ion battery was charged at a constant current of 1 / 3C to 3.65V at 25°C, and then charged at a constant voltage of 3.65V until the current dropped to 0.05C to obtain the initial charge capacity (Cc1). Subsequently, it was discharged at a constant current of 1 / 3C to 2.5V to obtain the initial discharge capacity (Cd1). The coulombic efficiency of the sodium-ion battery was calculated according to the following formula. Coulombic efficiency of sodium-ion battery = Initial discharge capacity (Cd1) / Initial charge capacity (Cc1)

[0105] [Capacity Retention Rate] The sodium-ion battery was charged at a constant current of 1C to 3.65V at 25°C, and then charged at a constant voltage of 3.65V until the current dropped to 0.05C. After that, it was discharged at a constant current of 1C to 2.5V to obtain the discharge capacity (Cd1) of the first cycle. This charge and discharge process was repeated up to n cycles to obtain the discharge capacity of the sodium-ion battery after n cycles, denoted as Cdn. The capacity retention rate of the sodium-ion battery was calculated according to the following formula. Capacity retention rate = Discharge capacity after n cycles (Cdn) / Discharge capacity of the first cycle (Cd1).

[0106] [Volume Expansion] The sodium-ion battery was immersed in a container filled with silicone oil, and the height of the silicone oil liquid surface at this time was recorded. After charging and discharging the battery for a predetermined number of cycles, the liquid surface of the silicone oil rose due to the action of the volume deformation pressure of the battery. The height of the silicone oil liquid surface in the container at this time was observed and recorded. The difference in the height of the liquid surface rise was obtained from the height of the silicone oil liquid surface before and after the charge and discharge cycles of the battery, and the volume expansion amount of the battery due to the cycles was calculated.

[0107] [Sodium Dendrites] The sodium-ion battery after 200 cycles was placed in a glove box under an argon gas atmosphere (H 2 O<0.1ppm, O 2It was disassembled at (<0.1 ppm), and the surface morphology of the negative electrode plate was visually observed with an optical microscope to confirm whether sodium dendritic crystals were formed. When there were no white spots on the negative electrode plate, it was determined that there was no sodium dendritic crystal situation. When there were scattered white spots on the negative electrode plate, it was determined that the sodium dendritic crystal situation was mild. When there were clearly many white spots on the negative electrode plate, it was determined that the sodium dendritic crystal situation was serious.

[0108] The compositions of the electrolytes and the results of the battery performance tests for Examples 1 to 34 and Comparative Examples 1 to 5 are as shown in Table 1 below.

[0109]

Table 1-1

Table 1-2

Table 1-3

Table 1-4

Table 1-5

Table 1-6

[0110] As can be seen from the above results, in Examples 1 to 34, by using an electrolyte containing an ether-based compound as a solvent, a sodium borate-based compound as a sodium salt, and a borate ester-based compound as an additive, the battery has a very small volume expansion amount after a plurality of cycles, and no sodium dendritic crystals appear on the electrodes, and the capacity retention rate and the initial Coulomb efficiency of the battery are high. In particular, when the content of the borate ester is 1 to 5% by weight, or when the content of sodium borate is in the range of 1 to 4 M, the volume expansion amount of the battery is further reduced, and the capacity retention rate and the initial Coulomb efficiency are further enhanced.

[0111] In contrast, Comparative Examples 1 to 5 do not simultaneously contain an ether-based solvent, a sodium borate-based compound, and a borate ester-based compound, or the proportion of the ether-based solvent in the entire solvent is too low. Therefore, sodium dendritic crystals appear after cycling in all cases, and the volume of the battery clearly expands, and the capacity retention rate and the initial Coulomb efficiency of the battery are lower than those of the examples of the present application.

[0112] It should be noted that the present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea within the scope of the technical solution of the present application and exhibiting the same functions and effects are all included within the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that those skilled in the art can conceive can be added to the embodiments, and other forms constituted by combining some components in the embodiments are also included within the scope of the present application.

Explanation of Reference Numerals

[0113] 1 Battery Pack 2 Upper Box 3 Lower Box 4 Battery Module 5 Sodium Ion Battery 51 Case 52 Electrode Assembly 53 Top Cap Assembly

Claims

1. An electrolyte for a sodium-ion battery comprising an ether-based compound as a solvent, a sodium borate-based compound as a sodium salt, and a borate ester-based compound as an additive, wherein the proportion of the ether-based compound in the total solvent of the electrolyte is 50% by weight or more.

2. The borate ester-based compound has a structure of the following formula (I), 【Chemical 1】 However, R １ , R ２ , R ３ are the same or different and are selected from an alkyl group, an aryl group, an alkylsilyl group, an alkenyl group, an alkynyl group, a cyanoalkyl group, and the above groups are optionally substituted by a halogen, optionally, the halogen is fluorine, and optionally, R １ , R ２ , R ３ are the same or different and are selected from a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a C6-C12 aryl group, a C6-C12 halogenated aryl group, a C1-C6 alkylsilyl group, a C2-C6 alkenyl group, a C2-C6 alkynyl group, a cyano-C1-C6 alkyl group, and optionally, at least one of R １ , R ２ and R ３ represents a C1-C6 fluoroalkyl group or a C6-C12 fluoroaryl group. Optionally, the borate ester-based compound is one or more selected from trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, tris(2,2,2-trifluoroethyl) borate, tris(hexafluoroisopropyl) borate, triphenyl borate, tris(trimethylsilyl) borate, tris(triethylsilyl) borate, tris(pentafluorophenyl) borate, (di-n-butyl)(vinyl) borate, (di-n-butyl)(propargyl) borate, tris(2-cyanoethyl) borate; and further optionally, the borate ester-based compound is one or more selected from trimethyl borate, triethyl borate, tripropyl borate, tributyl borate. The electrolyte for a sodium-ion battery according to Claim 1.

3. Based on the total weight of the electrolyte, the content of the borate ester-based compound is 0.5% by weight to 10% by weight, and optionally 1% by weight to 5% by weight. The electrolyte for a sodium-ion battery according to Claim 1.

4. The sodium borate-based compound is one or more selected from sodium difluoroborate and a compound having a structure of the following formula (II), 【Chemical Formula 2】 However, R ４ , R ５ , R ６ , R ７ is independently selected from a halogen atom, an alkyl group, a cyano group, an alkoxy group, and an aryl group, and the alkyl group, alkoxy group, and aryl group are optionally substituted by a halogen, and optionally, the halogen is fluorine, or R ４ and R ５ and / or R ６ and R ７ together form the structure of formula (a), [Chemical Formula 3] Optionally, R ４ , R ５ , R ６ , R ７ is independently selected from a halogen atom, a C1-C6 alkyl group, a C1-C6 halogenated alkyl group, a cyano group, a C1-C6 alkoxy group, a phenyl group, or R ４ and R ５ and / or R ６ and R ７ together form a structure of formula (a), optionally, R ４ , R ５ , R ６ , R ７ at least one of which represents a C1-C6 fluoroalkyl group, Optionally, the sodium borate compound is selected from one or more of sodium difluoroborate, sodium tetrafluoroborate, sodium diborate oxalate, sodium difluorooxalate borate, sodium tetraphenylborate, sodium tetracyano borate, sodium tetrakis(trifluoromethyl) borate, sodium bis(trifluoromethyl)difluoroborate, sodium pentafluoroethyltrifluoroborate, sodium dicyanooxalate borate, sodium methoxytricyanoborate, sodium ethoxytricyanoborate, sodium tetramethoxyborate, sodium tetraethoxyborate, sodium cyanotris(2,2,2-trifluoroethyl)borate, and the electrolyte of the sodium ion battery according to claim 1.

5. Based on the total volume of the electrolyte, the concentration of the sodium borate compound is 0.5 M to 8 M, and optionally 1 M to 4 M, and the electrolyte of the sodium ion battery according to claim 1.

6. The ether compound is one or more selected from aliphatic ethers having 4 to 20 carbon atoms, alicyclic ethers having 3 to 8 carbon atoms, aromatic ethers having 7 to 20 carbon atoms, and crown ethers. Optionally, the ether compound is one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether. Further optionally, the ether compound is one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether, and the electrolyte of the sodium ion battery according to claim 1.

7. The proportion of the ether compound in the entire solvent of the electrolyte is 60% by weight or more, optionally 80% by weight or more. Further optionally, the solvent consists of an ether compound, and the electrolyte of the sodium ion battery according to claim 1.

8. A sodium ion battery comprising the electrolyte according to any one of claims 1 to 7.

9. The sodium-ion battery according to claim 8, wherein the negative electrode active material in the negative electrode contains graphite.

10. A battery module comprising the sodium-ion battery according to claim 8.

11. A battery pack comprising the battery module according to claim 10.

12. An electric power consuming device, characterized in that it is selected from the sodium-ion batteries according to claim 8.

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