Electrolyte, secondary battery and electronic device

Abstract

The present disclosure provides an electrolyte, a secondary battery and an electronic device. The electrolyte includes a first additive selected from at least one of silane amides, and a second additive selected from at least one of fluorinated ethylene carbonates.

Description

[0001] ELECTROLYTE, SECONDARY BATTERY AND ELECTRONIC DEVICE

[0002] FIELD

[0003] The present disclosure relates to the technical field of batteries, and more particularly to an electrolyte, a secondary battery and an electronic device.

[0004] BACKGROUND

[0005] Secondary batteries have been widely used in various applications, such as electronic terminals and vehicles, and the demand for high-capacity, high-stability, long-life batteries and storage performance at a high temperature is gradually increasing. The electrolyte, as a “bridge” connecting a positive electrode and a negative electrode in the battery, has a significant impact on the overall performance of the battery.

[0006] Therefore, there is still a need for providing an electrolyte for improving the performance of the secondary battery including such an electrolyte.

[0007] SUMMARY

[0008] The present disclosure provides an electrolyte, a secondary battery and an electronic device.

[0009] In a first aspect, embodiments of the present disclosure provide an electrolyte. The electrolyte includes a first additive selected from at least one of silane amides, and a second additive selected from at least one of fluorinated ethylene carbonates.

[0010] In some embodiments, the first additive comprises at least one selected from compounds having a general formula (I); where Ri and R2 are independently selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, or substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups; R3, R4, and R5 represent hydrogen atoms, or are independently selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, and substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups.

[0011] In some embodiments, the first additive comprises at least one selected from compounds having a general formula (I): where Ri is selected from isobutyl, trifluoromethyl, or perfluorosubstituted ethyl; R2 is selected from methyl, or ethyl; R3 is selected from methyl, vinyl, or allyl; R4 is selected from methyl, vinyl, or allyl groups; R5 is selected from methyl, vinyl, or allyl groups.

[0012] In some embodiments, the second additive includes at least one selected from compounds having a general formula (II); where Rs represents a hydrogen atom, or is selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, and substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups.

[0013] In some embodiments, the second additive comprises at least one selected from compounds having a general formula (II): where Re is selected from hydrogen atoms, fluorine atoms, methyl groups, or allyl groups.

[0014] In some embodiments, the first additive includes at least one selected from:

[0015]

[0016] In some embodiments, the second additive includes at least one selected from:

[0017] In some embodiments, the electrolyte includes 0.3wt% to 2wt% of the first additive, and 0.5wt% to 5wt% of the second additive based on a total mass of the electrolyte.

[0018] In some embodiments, a mass ratio of the first additive to the second additive is 1 : 10 to 2: 1, optionally, 1 :5 to 1 : 1.

[0019] In some embodiments, the electrolyte further includes no more than 5wt% of a third additive based on a total mass of the electrolyte; the third additive includes at least one selected from vinyl carbonate (VC), 1,3,2-dioxathiolane 2,2-dioxide (DTD) , 1,3-propane sultone (PS), tri s(trimethyl silyl) phosphate (TMSP), tri s(trimethyl silyl) phosphite (TMSPi), tri s(trimethyl silyl) borate (TMSB), methyl methane disulfonate (MMDS), vinyl ethylene carbonate (VEC), butanedinitrile, hexanedinitrile, 1,3,6-hexanetrimethylnitrile, sodium difluorophosphate, disodium monofluorophosphate, and sodium tetrafluoroborate.

[0020] In some embodiments, the electrolyte further includes 5wt% to 20wt% of a sodium salt based on a total mass of the electrolyte.

[0021] In some embodiments, the electrolyte further includes 5wt% to 20wt% of a lithium salt based on a total mass of the electrolyte.

[0022] In some embodiments, the electrolyte further comprises 75wt% to 90wt% of a non-aqueous solvent based on the total mass of the electrolyte.

[0023] In a second aspect, embodiments of the present disclosure provide a battery includes the electrolyte according to any one of embodiments in the first aspect.

[0024] In a third aspect, embodiments of the present disclosure provide an electronic device includes the secondary battery according to any one of embodiments in the second aspect.

[0025] According to the embodiments of the present disclosure, the first additive is selected from silane amides, and the second additive is selected from fluorinated ethylene carbonates. Silane amides are reacted with the trace amounts of water or acid in the electrolyte to eliminate water and acid in the electrolyte to prevent acid damage to the structure of cathode electrolyte interface (CEI) or solid electrolyte interphase (SEI), thereby improving the stability of the CEI / SEI structure. Fluorinated ethylene carbonates have low film-forming impedance and good filmforming ability. In addition, silane amides have lone pair electrons, which combine with Lewis acid to reduce the amount of Lewis acid in the electrolyte, thereby preventing fluorinated ethylene carbonates from defluorination decomposition, and improving the stability of the second additive. In this way, the secondary battery including the electrolyte in the present disclosure has improved first coulombic efficiency, rate performance, cycling performance, and high-temperature storage performance.

[0026] Additional aspects and advantages of the present disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure.

[0027] DETAILED DESCRIPTION

[0028] Embodiments of the present disclosure are described in detail below. When a plurality of embodiments and modified examples are included in the following description, use in appropriate combination of characteristic portions thereof are anticipated in advance.

[0029] Reference will now be made in detail to embodiments. The implementations set forth in the following description of the embodiments do not represent all implementations consistent with the present disclosure.

[0030] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. The terms “comprises” and “includes” and any variation thereof in the description and claims of the present disclosure are intended to indicate a non-exclusive inclusion. As used in the embodiments of the present disclosure and the appended claims, “a / an”, and “the” in singular forms are intended to include plural forms, unless clearly indicated in the context otherwise. It should also be understood that, the term “and / or” used herein represents and contains any or all possible combinations of one or more associated listed items.

[0031] Term “optionally” means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0032] Term “range” disclosed in the present disclosure is defined in the form of a lower limit and an upper limit, a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The range defined in this way can be inclusive or exclusive, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is understood that ranges of 60- 110 and 80-120 are also obtained. In addition, if the listed minimum values are 1 and 2, and if the listed maximum values are 3, 4 and 5, the ranges of 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 may be obtained. In the present disclosure, unless otherwise specified, the numerical range “a-b” means the abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range “0-5” means that all the real numbers between “0-5” have been listed, and “0-5” is only the abbreviated representation of these numerical combinations. In addition, when a parameter is an integer >2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] As used herein, term “alkyl” refers to a saturated hydrocarbon group, having a linear or branched structure. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl (e.g. n-propyl, isopropyl), butyl (e.g. n-butyl, isobutyl, sec-butyl, tert-butyl). For example, a C1-C4 alkyl group indicates an alkyl group including 1 to 4 carbon atoms. Examples of suitable alkyl groups include, but are not limited to, methyl (Me, -CEE), ethyl (Et, -CH2CH3), 1 -propyl (n-Pr, n- propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CEE)2), 1 -butyl (n-Bu, n-butyl, - CH2CH2CH2CH3), 2-methyl-l -propyl (i-Bu, i-butyl, -CEECEhEEE^), 2-butyl (s-Bu, s-butyl, - CH(CEE)CH2CH3), and 2-methyl-2-propyl (t-Bu, t-butyl, -C(CEE)3).

[0034] As used herein, term “unsaturated hydrocarbon” refers to alkenyl group or alkynyl group, including a hydrocarbon having at least one site of unsaturation. Suitable examples include, but are not limited to, vinyl (-CH=CH2), allyl (-CEECE^CEE), cyclopentenyl (-C5H7), 5-hexenyl (- CH2CH2CH2CH2CH=CH2), ethynyl (-C=CH) and propargyl (-CH2C=CH).

[0035] In the related art, existing secondary batteries, especially sodium ion batteries, may still have high battery impedance, low first coulombic efficiency, and poor cycling stability, which lead to poor rate performance and cycling performance of the secondary batteries, limiting their application.

[0036] Fluorinated ethylene carbonates have low film-forming impedance and good film-forming ability, and may be used as an additive in the electrolyte of the secondary batteries to improve the cycle life of the batteries. However, the sodium salt or the lithium salt included in the electrolyte, such as NaPFe or LiPFe, is prone to decompose to produce Lewis acid (such as, PF5) and HF. Fluorinated ethylene carbonate additives will undergo defluorination decomposition reaction and ring-opening polymerization reaction in the presence of Lewis acid (such as, PF5), resulting in a continuous decrease of the fluorinated ethylene carbonate additives in the electrolyte. In addition, HF is corrosive and will cause dissolution of transition metal ions and damage to the solid electrolyte interphase (SEI) or cathode electrolyte interface (CEI), reducing the structural stability of the CEI or SEI.

[0037] Therefore, an object of the present disclosure is to provide an electrolyte including two additives having a synergistic effect, thereby improving performances, such as a cycle life, high- temperature storage performance and first coulombic efficiency, of the battery.

[0038] In a first aspect, embodiments of the present disclosure provide an electrolyte. The electrolyte includes a first additive and a second additive. The first additive is selected from at least one of silane amides, and the second additive is selected from at least one of fluorinated ethylene carbonates.

[0039] Silane amides may be reacted with the trace amounts of water or acid in the electrolyte to eliminate water and acid in the electrolyte to prevent acid damage to the CEI / SEI structure, thereby improving the stability of the CEI / SEI structure. Fluorinated ethylene carbonates have low filmforming impedance and good film-forming ability. In addition, silane amides have lone pair electrons, which may combine with Lewis acid to reduce the amount of Lewis acid in the electrolyte, thereby preventing fluorinated ethylene carbonates from defluorination decomposition, and improving the stability of the second additive. In this way, a secondary battery including the electrolyte in the present disclosure has improved first coulombic efficiency, rate performance, cycling performance, and high-temperature storage performance.

[0040] In some embodiments, the first additive includes at least one selected from compounds having a general formula (I): where Ri and R2 are independently selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, or substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups; R3, R4, and R5 represent hydrogen atoms, or are independently selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, and substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups.

[0041] In some embodiments, the first additive includes at least one selected from compounds having a general formula (I): where Ri is selected from isobutyl, trifluoromethyl, or perfluorosubstituted ethyl; R2 is selected from methyl, or ethyl; R3 is selected from methyl, vinyl, or allyl; R4 is selected from methyl, vinyl, or allyl groups; R5 is selected from methyl, vinyl, or allyl groups.

[0042] In some embodiments, the first additive includes at least one selected from:

[0043] In some embodiments, the first additive includes at least one selected from:

[0044] In some embodiments, the first additive is: In some embodiments, the second additive includes at least one selected from compounds having a general formula (II): where Re represents a hydrogen atom, or is selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, and substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups.

[0045] In some embodiments, the second additive includes at least one selected from compounds having a general formula (II): where Re is selected from hydrogen atoms, fluorine atoms, methyl groups, or allyl groups. In some embodiments, the second additive includes at least one selected from:

[0046] In some embodiments, the second additive includes at least one selected from:

[0047] In some embodiments, the second additive is:

[0048] The specific compounds in the first additive and the second additive may be obtained commercially or prepared according to common methods in the related art. The electrolyte may be obtained by mixing raw materials.

[0049] In some embodiments, the electrolyte includes 0.3wt% to 2wt% of the first additive, and 0.5wt% to 5wt% of the second additive based on a total mass of the electrolyte. In some embodiments, the electrolyte includes 0.4wt% to 1 ,5wt% of the first additive, and 0.8wt% to 2wt% of the second additive based on the total mass of the electrolyte. For example, the electrolyte includes 0.5wt% of the first additive, and lwt% of the second additive based on the total mass of the electrolyte.

[0050] In some embodiments, a mass ratio of the first additive to the second additive is 1 : 10 to 2: 1. In some embodiments, the mass ratio of the first additive to the second additive is 1 :5 to 1 : 1, such as, 1 : 2, 1 : 4, or 3: 5.

[0051] When using the first additive and the second additive within the above-mentioned ranges and / or in the above-mentioned ratios, the first additive and the second additive have a good synergistic effect, which may further improve the battery performances such as the first coulombic efficiency, the rate performance, the cycling performance, and the high-temperature storage performance.

[0052] In some embodiments, the electrolyte further includes no more than 5wt% of a third additive based on a total mass of the electrolyte. In some embodiments, the electrolyte the electrolyte further includes no more than 3wt% of a third additive based on the total mass of the electrolyte, such as lwt%, 2wt%. Alternatively, the electrolyte does not includes other additives. The third additive may include at least one selected from carbonate (VC), 1,3,2-dioxathiolane 2,2-dioxide (DTD), 1,3-propane sultone (PS), tri s(trimethyl silyl) phosphate (TMSP), tri s(trimethyl silyl) phosphite (TMSPi), tri s(trimethyl silyl) borate (TMSB), methyl methane disulfonate (MMDS), vinyl ethylene carbonate (VEC), butanedinitrile, hexanedinitrile, 1,3,6-hexanetrimethylnitrile, sodium difluorophosphate, disodium monofluorophosphate, and sodium tetrafluoroborate.

[0053] The third additive and the amount of the third additive may be selected according to actual needs. The third additive may be applied to improve properties of the electrolyte as needed without damaging the synergistic effect of the first additive and the second additive. The above specific materials of the third additive are only examples, any other suitable additive may be applied.

[0054] In some embodiments, the electrolyte may include 5wt% to 20wt% of a sodium salt based on a total mass of the electrolyte. In some embodiments, the electrolyte may include 10wt% to 15wt% of a sodium salt based on a total mass of the electrolyte. For example, the electrolyte may include llwt%, 12wt%, 13wt%, or 14 wt% of a sodium salt based on a total mass of the electrolyte.

[0055] The sodium salt may include at least one selected from sodium hexafluorophosphate, sodium difluoro(oxalate)borate, sodium tetrafluorob orate, sodium bis(oxalato)borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imine, sodium trifluorom ethyl sulfonate, and sodium bis(trifluoromethylsulfonate)imine.

[0056] In some embodiments, the electrolyte may include 5wt% to 20wt% of a lithium salt based on a total mass of the electrolyte. In some embodiments, the electrolyte may include 10wt% to 15wt% of a lithium salt based on a total mass of the electrolyte. For example, the electrolyte may include llwt%, 12wt%, 13wt%, or 14 wt% of a lithium salt based on a total mass of the electrolyte.

[0057] In some embodiments, the lithium salt may include at least one selected from lithium hexafluorophosphate, lithium tetrafluorob orate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulphonyl)imide, lithium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalate)borate, lithium difluoro(bisoxalato) phosphate, and lithium tetrafluorooxalate phosphate.

[0058] The electrolytes in embodiments of the present disclosure may be suitable for lithium-ion batteries and sodium-ion batteries, which have high compatibility and wide application.

[0059] In some embodiments, the electrolyte may include 75wt% to 90wt% of a non-aqueous solvent based on the total mass of the electrolyte. In some embodiments, the electrolyte may include 80wt% to 85wt% of a non-aqueous solvent based on the total mass of the electrolyte. For example, based on the total mass of the electrolyte, the electrolyte may include 81wt%, 82wt%, 83wt%, or 84wt% of a non-aqueous solvent.

[0060] In some embodiments, the non-aqueous solvent may include at least one selected from esters, ethers, sulfones, hydrofluoroethers, and carboxylate esters.

[0061] In some embodiments, the non-aqueous solvent may include at least one selected from ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxy ethane (DME), di ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, sulfolane (SUL), l,l,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (D2), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), and propyl propionate (PP).

[0062] Embodiments of the present disclosure also provide a method for preparing an electrolyte.

[0063] In some embodiments, the method includes providing a non-aqueous solvent; mixing an electrolyte salt, a first additive and a second additive into the non-aqueous solvent; and obtaining an electrolyte. The first additive is selected from at least one of silane amides; and the second additive is selected from at least one of fluorinated ethylene carbonates.

[0064] The method for preparing the electrolyte in an embodiment of the present disclosure is simple to operate and suitable for industrial production.

[0065] In some embodiments, the electrolyte salt may be a sodium salt or a lithium salt.

[0066] The first additive, the second additive, the sodium salt or the lithium salt and the non-aqueous solvent in the electrolyte according to any one of embodiments in the first aspect are applicable to the method embodiments.

[0067] In some embodiments, the electrolyte salt is in a range of 5wt% to 20wt%, the first additive is in a range of 0.3wt% to 2wt%, the second additive is in a range of 0.5wt% to 5wt% and the nonaqueous solvent is in a range of 75wt% to 90wt% based on a total mass of the electrolyte.

[0068] In some embodiments, the method may further include adding a third additive into the electrolyte. The third additive in the electrolyte according to any one of embodiments in the first aspect is applicable to the method embodiments.

[0069] The method provided in the preset disclosure has the same advantage as the electrolyte in the first aspect of the preset disclosure, which will not be repeated.

[0070] In a second aspect, the present disclosure provides a secondary battery. The secondary battery includes the electrolyte according to any one of embodiments in the first aspect.

[0071] In some embodiments, the secondary battery includes a positive electrode plate, a negative electrode plate, a separator and the electrolyte according to any one of embodiments in the first aspect.

[0072] In some embodiments, the secondary battery may be a sodium ion battery.

[0073] In the sodium ion battery, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes the cathode active material.

[0074] As an example, the positive electrode current collector has two surfaces along a thickness direction thereof and facing in opposite directions, and the positive electrode film layer is provided on either or both of the two surfaces.

[0075] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil may be used. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metallic material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a substrate of a high molecular material such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0076] In some embodiments, the cathode material is a compound capable of reversibly intercalating and deintercalating Na+. As an example, the cathode active material includes transition metal oxides, polyanionic compounds, Prussian blue (PB) and analogues of PB (PBAs), and the like.

[0077] In some embodiments, the cathode active material is a transition metal oxide, for example, a sodium-containing composite oxide represented by NaxMCh or NayNfcCU (where M is a transition metal, 0 < x < l, 0 < y < 2), a spinel-like oxide, and a metal chalcogenide of a layered structure or an olivine structure. For example, the cathode active material is selected from sodium cobalt oxide such as NaCoCh, sodium manganese oxide such as NaM CU, sodium nickel oxide such as NaNiCh, sodium titanium oxide such as Na^Tis CU, sodium manganese nickel composite oxide and sodium manganese nickel cobalt composite oxide; a material having an olivine-type crystalline structure such as NaMPCU (M = Fe, Mn, Ni).

[0078] In some embodiments, the cathode active material is optionally a sodium-containing composite oxide of a layered structure or a spinel structure, for example, NaCoCh, NaM CU, NaNiCh, NaNii / 2Mni / 2O2, NaNii / sMni / sCoi / sCh, NaNio.eMno.2Coo.2O2, NaNii-x-y-zCoxAlyMgzO2 (where 0 < x < 1, 0 < y < 0.1, 0 < z < 0.1, 0 < 1-x-y-z < 1). In some embodiments, a part of the constituent elements of the sodium-containing composite oxides may be substituted with an additional element such as Ge, Ti, Zr, Mg, Al, Mo, and Sn. In some embodiments, the cathode active material is a polyanionic compound. As an example, the polyanionic compound may be a class of compounds having sodium ions, transition metal ions, and tetrahedral (YO4)n" anionic units. The transition metal may include at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Y may be at least one selected from P, S and Si, and n in a group of (YO4)n" represents a valence of the group. The polyanionic compound may be a class of compounds having sodium ions, transition metal ions, tetrahedral (YCU)11' anion units, and halide anions. The transition metal may include at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Y may be at least one selected from P, S and Si, n in a group of (YO4)n" represents a valence of the group, and halogen may include at least one selected from F, Cl, and Br. The polyanionic compounds may be a class of compounds having sodium ions, tetrahedral (YCU)11' anionic units, polyhedral units (ZOy)m+and optionally halide anions. Y may be at least one selected from P, S and Si, n in a group of (YO4)n" represents a valence of the group, Z represents a transition metal, which may be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, m in a group of (ZOy)m+represents a valence of the group, and halogen may include at least one selected from F, Cl, and Br. The polyanionic compound is, for example, at least one of NaFePCU, Na3V2(PO4)3, NaM’PC F (M’ is at least one selected from V, Fe, Mn and Ni) or Na3(VOy)2(PO4)2F3-2y(0 < y < 1).

[0079] In some embodiments, the cathode active material is a Prussian blue (PB) and its analogues (PB As). As an example, Prussian blue (PB) and its analogues (PB As) may be a class of compounds having a sodium ion, a transition metal ion, and a cyanide ion (CN‘). The transition metal may include at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue (PB) and its analogues (PBAs) are for example NaaMebMe’c(CN)6, where Me and Me’ each independently include at least one selected from Ni, Cu, Fe, Mn, Co and Zn, where 0 <a < 2, 0 <b <1, and 0 <c <1.

[0080] In some embodiments, the positive electrode film layer optionally includes a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene- hexafluoropropylene copolymer, or fluoroacrylate resin.

[0081] In some embodiments, the positive electrode film layer includes the binder of 0.1 to 3.5%, optionally 0.5 to 2.5% by weight.

[0082] In some embodiments, the positive electrode film layer optionally includes a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments, the positive electrode film layer includes the conductive agent of 0.05% to 5%, optionally 0.5% to 3% by weight.

[0084] In some embodiments, the positive electrode plate may be prepared by: dispersing the above- mentioned components for preparing the positive electrode plate, such as the cathode active material, the conductive agent, the binder and any other components in a solvent (such as N-methyl pyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and obtaining the positive electrode plate after drying, cold pressing and other processes.

[0085] In the sodium ion battery, a negative electrode plate typically includes a negative current collector and an anode active material layer disposed on the negative current collector. The anode active material layer includes the anode active material.

[0086] The negative electrode plate may include only the negative electrode current collector, i.e. not include the anode active material. The negative electrode plate may include a pre-deposited metal phase on the negative current collector. The negative electrode current collector may be made of a conventional metal foil, a carbon-coated metal foil, or a porous metal plate. As an example, a copper foil or an aluminum foil may be used as the negative electrode current collector.

[0087] Specific type of the anode active material is not limited, and an active material known in the art which may be used for a negative electrode of a sodium ion battery can be used, and those skilled in the art can make a selection according to actual requirements. As an example, the anode active material may include, but is not limited to, one or more of a sodium metal, a carbon material, an alloy material, a transition metal oxide and / or sulfide, a phosphorus-based material, a titanate material. Specifically, the carbon material may include one or more of hard carbon, soft carbon, amorphous carbon, nano- structured carbon materials; the alloy material may include an alloy material formed by one or more of Si, Ge, Sn, Pb and Sb; the transition metal oxides and sulfides have a general formula MxNy, where M includes one or more of Fe, Co, Ni, Mn, Sn, Mo, Sb and V, and N includes O or S; the phosphorus-based material may include one or more of red phosphorus, white phosphorus and black phosphorus; the titanate material may include one or more of ISfeTisO?, Na2TieOi3, Na^isOu, Li^isOn and NaTi2(PC>4)3. These materials are commercially available.

[0088] The anode active material layer further generally optionally includes a conductive agent for improving an electrical conductivity of the anode active material layer, and a binder for binding the anode active material and the conductive agent to the negative electrode current collector. The types of the conductive agent and the binder are not particularly limited, and may be selected according to actual requirements.

[0089] As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0090] As an example, the binder may include at least one selected from styrene butadiene rubber (SBR), styreneic block copolymers (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0091] The anode active material layer may optionally include a thickener such as carboxymethyl cellulose (CMC). The present disclosure is not limited to the above, and other materials which may be used as the thickener for the negative electrode plate of the sodium-ion battery may be used in the present disclosure.

[0092] In the sodium ion battery, a separator may be a porous membrane with good chemical stability and mechanical stability, which is not limited in the present disclosure.

[0093] In some embodiments, the material of the separator is 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. When the separator is a multilayer composite film, materials of individual layers may be the same or different.

[0094] In the sodium ion battery, an electrolyte may be the electrolyte in the embodiments of the present disclosure.

[0095] In some embodiments, the secondary battery may be a lithium ion battery.

[0096] In the lithium ion battery, a positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes the cathode active material.

[0097] As an example, the positive electrode current collector has two surfaces along a thickness direction thereof and facing in opposite directions, and the positive electrode film layer is provided on either or both of the two surfaces.

[0098] The positive electrode film layer includes the cathode active material. The cathode active material may be selected from materials capable of absorbing and releasing lithium.

[0099] The specific kind of the cathode active material is not particularly limited and may be selected according to requirements. As an example, the cathode active material may include, but is not limited to, lithium iron phosphate (LiFePC ), lithium manganese phosphate (LiMnPC ), lithium cobalt phosphate (LiCoPC ), iron pyrophosphate (Li2FeP2O?), lithium cobaltate (LiCoCh), spineltype lithium manganate (LiM C ), spinel-type lithium nickel manganate (LiNio.5Mn1.5O4), layered lithium manganate (LiMnO2), lithium nickelate (LiNiO2), lithium niobate (LiNbO2), lithium ferrite (LiFeCh), lithium magnesium oxide (LiMgCh), lithium calcium oxide (LiCaCh), lithium cuprate (LiCuCh), lithium zincate (LiZnCh), lithium molybdate (LiMoCh), lithium tantalate (LiTaCh), lithium tungstate (LiWCh), lithium nickel cobalt aluminum oxide (LiNixCoyAh-x-yCh, 0<x<l, 0<y<l, 0 <x + y<l, e.g. LiNi0.sCo0.15Al0.05O2), lithium nickel cobalt manganese oxides (LiNixCoyMni-x-yO2, 0<x<l, 0<y<l, 0<x + y<l, e.g., LiNii / 3Coi / 3Mni / 3O2, liNio.5Coo.2Mno.3O2, liNio.6Coo.2Mno.2O2, liNio.sCoo.1Mno.1O2, etc.), lithium-rich materials (e.g. lithium-rich nickel cobalt manganese oxides), manganese oxides (Mn02), vanadium oxides, sulfur oxides, silicate oxides, and at least one of its respective modified compounds. These materials may be used separately or in combination (for example two or more kinds of materials are used).

[0100] The above cathode active material may be modified, for example is doped, coated, or both doped and coated with a modification compound.

[0101] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil may be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metallic material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a substrate of a high molecular material such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0102] In some embodiments, the positive electrode film layer optionally includes a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene- hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0103] In some embodiments, the positive electrode film layer optionally includes a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0104] In some embodiments, the positive electrode plate may be prepared by: dispersing the above- mentioned components for preparing the positive electrode plate, such as the cathode active material, the conductive agent, the binder and any other components in a solvent (such as N-methyl pyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and obtaining the positive electrode plate after drying, cold pressing and other processes. In the lithium ion battery, a negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes an anode active material.

[0105] As an example, the negative electrode current collector has two surfaces along a thickness direction thereof and facing in opposite directions, and the negative electrode film layer is provided on either or both of the two surfaces.

[0106] In some embodiments, the negative current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metallic material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a substrate of a high molecular material such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0107] In some embodiments, the anode active material may be an anode active material known in the art for a battery. As an example, the anode active material may include at least one selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin- based materials and lithium titanate. The silicon-based material may be at least one selected from elemental silicon, silicon-oxygen compounds, silicon-carbon complexes, silicon-nitrogen complexes, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide compounds, and tin alloys. The present disclosure is not limited to these materials, and other materials that may be used as an anode active material for a battery may be used. These anode active materials may be used separately or in combination (for example two or more kinds of materials are used).

[0108] In some embodiments, the negative electrode film layer optionally includes a binder. The binder may be at least one selected from 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).

[0109] In some embodiments, the negative electrode film layer optionally includes a conductive agent. The conductive agent may be at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the negative electrode film layer optionally includes other adjuvants, such as thickeners (e.g. sodium carboxymethylcellulose (CMC-Na)).

[0111] In some embodiments, the negative electrode plate may be prepared by: dispersing the above- mentioned components for preparing the negative electrode sheet, such as the anode active material, the conductive agent, the binder and any other components in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and obtaining the negative electrode plate after drying, cold pressing and other processes.

[0112] In the lithium ion battery, a separator may be a porous membrane with good chemical stability and mechanical stability, which is not limited in the present disclosure.

[0113] In some embodiments, the material of the separator is 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. When the separator is a multilayer composite film, materials of individual layers may be the same or different.

[0114] In the lithium ion battery, an electrolyte may be the electrolyte in the embodiments of the present disclosure.

[0115] In some embodiments, the battery may be a battery module or a battery pack, which may be applied in electronic devices, such as mobile terminals and vehicles.

[0116] In some embodiments, the secondary battery includes an outer package. The outer package is used to package the electrodes and the electrolyte.

[0117] In some embodiments, the outer package of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell and the like. Alternatively, the outer package of the secondary battery may be a soft package, such as a soft bag. The soft bag may be made of a polymer material such as plastics, polypropylene, polybutylene terephthalate and polybutylene succinate.

[0118] The shape of the secondary battery may be cylindrical, square or any other shape, which is not limited in the present disclosure.

[0119] The secondary battery provided in the second aspect of the preset disclosure has the same advantage as the electrolyte in the first aspect of the preset disclosure, which will not be repeated.

[0120] In a third aspect, the present disclosure provides an electronic device. The electronic device includes the battery according to any one of embodiments in the second aspect.

[0121] In some embodiments, the electronic device may be electric cars, electric motorcycles, computers, mobile phones, smart watches, and so on.

[0122] The electronic device provided in the third aspect of the preset disclosure has the same advantage as the electrolyte in the first aspect of the preset disclosure, which will not be repeated.

[0123] Examples

[0124] Hereinafter, the present disclosure will be further described with Examples, but the present disclosure is not limited to these Examples.

[0125] It is noted that the materials and reagents used in embodiments may all be obtained commercially or prepared according to common methods in the related art.

[0126] The first additive used in Examples are listed in Table 1, and the second additive used in Examples are listed in Table 2.

[0127] Table 1 Inventive Example 1 (IE1)

[0128] Production of Positive Electrode Plate

[0129] 96.5 parts by mass of NaNii Fei Mni Ch, 2 parts by mass of conductive carbon black SP, and 1.5 parts by mass of polyvinylidene fluoride (PVDF) were evenly dispersed into an appropriate amount (lOOmL) of N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode mixture slurry. Then, the positive electrode mixture slurry was applied on both surfaces of an aluminum foil with a thickness of 12pm, the aluminum foil was dried and then rolled, and cut to a predetermined size to produce a positive electrode. Production of Negative Electrode Plate

[0130] 96.5 parts by mass of hard carbon, 1 part by mass of conductive carbon black SP, 0.6 part by mass of carboxymethylcellulose (CMC), and 1.9 part by mass of styrene-butadiene rubber (SBR) were evenly dispersed into an appropriate amount of deionized water to obtain a negative electrode mixture slurry. Then, the negative electrode mixture slurry was applied on both surfaces of an aluminum foil with a thickness of 8pm, the aluminum foil was dried and then rolled, and cut to a predetermined size to produce a negative electrode.

[0131] Preparation of Electrolyte

[0132] In an argon atmosphere (EECKO. l ppm, O2<0.1 ppm), 42.7 parts by mass of PC, and 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPFe, 0.5 parts by mass of Compound 1, and 1 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0133] Production of Battery

[0134] The above positive electrode, a PE separator and the above negative electrode were rolled into a cylindrical cell in a sequence, the cylindrical cell was placed into a shell, and the electrolyte was injected inside the shell. After spot welding, rolling, and packaging, a cylindrical battery was obtained.

[0135] Inventive Example 2 (IE2)

[0136] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.2 parts by mass of PC, and 42.2 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPFe, 0.5 parts by mass of Compound 2, and 2 parts by mass of Compound 8 were dissolved to prepare an electrolyte.

[0137] Inventive Example 3 (IE3)

[0138] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.7 parts by mass of PC, and 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 0.5 parts by mass of Compound 3, and 1 part by mass of Compound 9 were dissolved to prepare an electrolyte.

[0139] Inventive Example 4 (IE4)

[0140] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.7 parts by mass of PC, and 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 0.5 parts by mass of Compound 4, and 1 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0141] Inventive Example 5 (IE5)

[0142] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.8 parts by mass of PC, and 42.8 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 0.3 parts by mass of Compound 1, and 0.5 parts by mass of Compound 7 were dissolved to prepare an electrolyte.

[0143] Inventive Example 6 (IE6)

[0144] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 41.95 parts by mass of PC, and 41.95 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 2 parts by mass of Compound 1, and 1 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0145] Inventive Example 7 (IE7)

[0146] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 39.7 parts by mass of PC, and 39.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 0.5 parts by mass of Compound 1, 5 parts by mass of Compound 9, 1 part by mass of PS, and 1 part by mass of DTD were dissolved to prepare an electrolyte.

[0147] Inventive Example 8 (IE8)

[0148] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 40.2 parts by mass of PC, and 40.2 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 0.5 parts by mass of Compound 1, 1 part by mass of Compound 9, 3 parts by mass of PS, and 2 parts by mass of DTD were dissolved to prepare an electrolyte.

[0149] Inventive Example 9 (IE9)

[0150] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 45 parts by mass of PC, and 45 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 5 part by mass of NaPFe, 2 parts by mass of Compound 1, and 3 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0151] Inventive Example 10 (IE 10)

[0152] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 37.5 parts by mass of PC, and 37.5 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 20 part by mass of NaPFe, 2 parts by mass of Compound 1, and 3 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0153] Inventive Example 11 (IE11)

[0154] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 20 parts by mass of EC, 20 parts by mass of DEC, and 40 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPFe, 0.5 parts by mass of Compound 1, and 1 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0155] Inventive Example 12 (IE 12)

[0156] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.7 parts by mass of PC, and 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 0.5 parts by mass of Compound 5, and 1 part by mass of Compound 10 were dissolved to prepare an electrolyte.

[0157] Inventive Example 13 (IE13)

[0158] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.7 parts by mass of PC, and 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, 0.5 parts by mass of Compound 6, and 1 part by mass of Compound 10 were dissolved to prepare an electrolyte.

[0159] Inventive Example 14 (IE 14)

[0160] Production of Positive Electrode

[0161] 96.5 parts by mass of LiNio.sCoo.15Alo.05O2, 2 parts by mass of conductive carbon black SP, and 1.5 parts by mass of polyvinylidene fluoride (PVDF) were evenly dispersed into an appropriate amount (lOOmL) of N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode mixture slurry. Then, the positive electrode mixture slurry was applied on both surfaces of an aluminum foil with a thickness of 12pm, the aluminum foil was dried and then rolled, and cut to a predetermined size to produce a positive electrode.

[0162] Production of Negative Electrode

[0163] 96.5 parts by mass of graphite, 1 part by mass of conductive carbon black SP, 0.6 part by mass of carboxymethylcellulose (CMC), and 1.9 part by mass of styrene-butadiene rubber (SBR) were evenly dispersed into an appropriate amount of deionized water to obtain a negative electrode mixture slurry. Then, the negative electrode mixture slurry was applied on both surfaces of an aluminum foil with a thickness of 8pm, the aluminum foil was dried and then rolled, and cut to a predetermined size to produce a negative electrode.

[0164] Preparation of Electrolyte

[0165] In an argon atmosphere (H2CKO.I ppm, O2<0.1 ppm), A battery was produced in the same manner as in El except that, in the production of the electrolyte, 42.7 parts by mass of PC, and 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of LiPFe, 0.5 parts by mass of Compound 1, and 1 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0166] Production of Battery

[0167] The above positive electrode, a PE separator and the above negative electrode were rolled into a cylindrical cell in a sequence, the cylindrical cell was placed into a shell, and the electrolyte was injected inside the shell. After spot welding, rolling, and packaging, a cylindrical battery was obtained.

[0168] Comparative Example 1 (CE1)

[0169] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.7 parts by mass of PC, 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, and 1.5 part by mass of Compound 7 were dissolved to prepare an electrolyte.

[0170] Comparative Example 2 (CE2)

[0171] Abattery was produced in the same manner as in IE1 except for an electrolyte. In this example, in the production of the electrolyte, 42.7 parts by mass of PC, 42.7 parts by mass of EMC were mixed to obtain a mixed solvent. At room temperature, into the mixed solvent, 13.1 part by mass of NaPF6, and 1.5 parts by mass of Compound 1 were dissolved to prepare an electrolyte.

[0172] Tests

[0173] Evaluation of Discharge Capacity Retention Rate

[0174] For the sodium batteries, under an environment temperature at 25°C, the batteries of Inventive Examples and Comparative Examples was charged at a constant current of 0.5 C until 4.0 V, and then charged at a constant voltage of 4.0 V until a current value reached 0.05 C. After the battery was left to stand for 30 minutes, the battery was discharged at a constant current of 0.2 C and 5 C until 1.5 V respectively, and the discharge capacities was recorded. For the lithium batteries, under an environment temperature at 25°C, the lithium batteries of Inventive Examples and Comparative Examples was charged at a constant current of 0.5 C until 4.2 V, and then charged at a constant voltage of 4.2 V until a current value reached 0.05 C. After the battery was left to stand for 30 minutes, the battery was discharged at a constant current of 0.2 C and 5 C until 3 V respectively, and the discharge capacities was recorded.

[0175] 5 C discharge capacity retention rate (%) = (5 C discharge capacity / 0.2 C discharge capacity) x 100%

[0176] Evaluation of Cycling Performance at Room Temperature

[0177] For the sodium batteries, under an environment temperature at 25°C, the batteries of Inventive Examples and Comparative Examples was charged at a constant current of 0.5 C until 4.0 V, and then charged at a constant voltage of 4.0 V until a current value reached 0.05 C. After the battery was left to stand for 5 minutes, the battery was discharged at a constant current of 1 C until 1.5 V. This charge and discharge was specified as one cycle, and 400 cycles were performed at 25°C. For the lithium batteries, under an environment temperature at 25°C, the batteries of Inventive Examples and Comparative Examples was charged at a constant current of 0.5 C until 4.2 V, and then charged at a constant voltage of 4.2 V until a current value reached 0.05 C. After the battery was left to stand for 5 minutes, the battery was discharged at a constant current of 1 C until 3 V. This charge and discharge was specified as one cycle, and 400 cycles were performed at 25°C.

[0178] Capacity retention rate after 400 cycles (%) = (discharge capacity at 400thcycle / discharge capacity at 1stcycle) X 100%

[0179] First Coulombic efficiency = discharge capacity at 1stcycle / charge capacity at 1stcycle

[0180] Evaluation of Direct Current Resistance (DCR) of the battery at 25°C

[0181] The batteries of Inventive Examples and Comparative Examples was charged at a constant current of 4 C for 30s at 25°C. A starting voltage, an ending voltage and a starting current were recorded.

[0182] DCR = (starting voltage - ending voltage) / starting current.

[0183] Evaluation of storage at 60°C

[0184] For the sodium batteries, the batteries of Examples and Comparative Examples was performed 5 charge and discharge cycles at a charge / discharge rate of 0.5 C / 0.5 C at a room temperature, and then the battery is charged at a constant current of 0.5 C until 4.0 V. A capacity of 0.5 C and the direct current resistance (DCR) of the battery were recorded as Q and R. The fully charged battery was stored in a 60°C environment for 56 days. DCR of the battery on the 7th, 14th, 28thand 56thdays were recorded as R7, R14, R28, and R56, respectively. Then, the battery was charged and discharged at a rate of 0.5 C / 0.5 C at 25°C, and the discharge capacities were recorded as Q?-b, Qi4-b, Q28-b, and Qse-b at 0.5 C.

[0185] For the lithium batteries, the batteries of Examples and Comparative Examples was performed 5 charge and discharge cycles at a charge / discharge rate of 0.5 C / 0.5 C at a room temperature, and then the battery is charged at a constant current of 0.5 C until 4.2 V. A capacity of 0.5 C and the direct current resistance (DCR) of the battery were recorded as Q and R. The fully charged battery was stored in a 60°C environment for 56 days. DCR of the battery on the 7th, 14th, 28thand 56thdays were recorded as R7, Ru, R28, and R56, respectively. Then, the battery was charged and discharged at a rate of 0.5 C / 0.5 C at 25°C, and the discharge capacities were recorded as Q?-b, Qi4-b, Q28-b, and Qse-b at 0.5 C.

[0186] The capacity recovery retention rate and DCR increase rate for high-temperature storage of the battery were calculated as follows.

[0187] Capacity recovery retention rate=Qn-b / Qx100%;

[0188] DCR increase rate = Rn / Rx100%, where, n represents the nthday of storage.

[0189] Table 3 shows 5 C discharge capacity retention rate of batteries of Inventive Examples and

[0190] Comparative Examples.

[0191] Table 3 Table 4 shows capacity retention rate after 400 cycles at 25°C of batteries of Inventive

[0192] Examples and Comparative Examples.

[0193] Table 4

[0194] Table 5 shows storage performance at 60°C of batteries of Inventive Examples and

[0195] Comparative Examples.

[0196] Table 5

[0197] According to Inventive Examples, the battery has the electrolyte of the present disclosure, which includes two additives. The first additive is selected from at least one of silane amides, and the second additive is selected from at least one of fluorinated ethylene carbonates. The first additive has a silane group, which may react with NaPFe to produce NaPF2. NaPF2 may reduce the internal resistance of the battery and increase the rate. In addition, the first additive has a nitrogen-atom with lone pair electron, which may coordinate with PF5 originated from NaPFe to reduce PF5, thereby preventing fluorinated ethylene carbonates from defluorination decomposition at the presence of PF5, and improving the stability of the second additive. According to Table 3 to Table 5, the batteries of Inventive Examples have an improved capacity retention rate, improved cycling performance and improved high-temperature storage performance compared with the batteries of Comparative Examples 1 to 2, which includes a single additive. It can be seen that in the electrolyte of IE1, 0.5 parts by mass of Compound 1, and 1 part by mass of Compound 7 are used. For CE1 or CE2, single additive is used but at a same mass part as a total mass of the two additives of IE1. That is, 1.5 parts by mass of Compound 7 is used for CE1 and 1.5 parts by mass of Compound 1 is used for CE2. The battery of IE1 exhibits better performance than that of CE1 or CE2, showing that the two types of additives of the present disclosure can achieve the synergistic effect in improving the battery performances.

[0198] As above, it is found from the results shown in Table 3 to 5 that the electrolyte of the present disclosure, which includes two additives having synergistic effect, remarkably exhibits the effect of improving the battery performance, such as capacity retention rate, cycling performance and storage performance at 60°C.

[0199] Reference throughout this specification to “an embodiment,” “some embodiments,” “one embodiment”, “another example,” “an example,” “a specific example,” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment”, “in an embodiment”, “in another example,” “in an example,” “in a specific example,” or “in some examples,” in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0200] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed here. This application is intended to cover any variations, uses, or adaptations of the disclosure following the general principles thereof and including such departures from the present disclosure as come within known or customary practice in the art. It is intended that the specification and examples be considered as illustrative only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

CLAIMS1. An electrolyte, comprising: a first additive, selected from at least one of silane amides; and a second additive, selected from at least one of fluorinated ethylene carbonates.

2. The electrolyte according to claim 1, wherein the first additive comprises at least one selected from compounds having a general formula (I);where Ri and R2 are independently selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, or substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups; R3, R4, and R5 represent hydrogen atoms, or are independently selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, and substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups.

3. The electrolyte according to claim 1 or 2, wherein the first additive comprises at least one selected from compounds having a general formula (I):where Ri is selected from isobutyl, trifluoromethyl, or perfluorosubstituted ethyl; R2 is selected from methyl, or ethyl; R3 is selected from methyl, vinyl, or allyl; R4 is selected from methyl, vinyl, or allyl groups; R5 is selected from methyl, vinyl, or allyl groups.

4. The electrolyte according to any one of claims 1 to 3, wherein the second additive comprises at least one selected from compounds having a general formula (II);where Re represents a hydrogen atom, or is selected from fluorine atom, substituted or unsubstituted C1-C4 alkyl groups, and substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups.

5. The electrolyte according to any one of claims 1 to 4, wherein the second additive comprises at least one selected from compounds having a general formula (II):where Re is selected from hydrogen atoms, fluorine atoms, methyl groups, or allyl groups.

6. The electrolyte according to any one of claims 1 to 5, wherein the first additive comprises at least one selected from:

7. The electrolyte according to any one of claims 1 to 6, wherein the second additivecomprises at least one selected from:

8. The electrolyte according to any one of claims 1 to 7, wherein the electrolyte comprises 0.3wt% to 2wt% of the first additive, and 0.5wt% to 5wt% of the second additive based on a total mass of the electrolyte.

9. The electrolyte according to any one of claims 1 to 8, wherein a mass ratio of the first additive to the second additive is 1 : 10 to 2: 1, optionally, 1 :5 to 1 : 1.

10. The electrolyte according to any one of claims 1 to 9, wherein the electrolyte further comprises no more than 5wt% of a third additive based on a total mass of the electrolyte; wherein the third additive comprises at least one selected from vinyl carbonate (VC), 1,3,2- di oxathiolane 2,2-dioxide (DTD) , 1,3 -propane sultone (PS), tri s(trimethyl silyl) phosphate (TMSP), tri s(trimethyl silyl) phosphite (TMSPi), tri s(trimethyl silyl) borate (TMSB), methyl methane disulfonate (MMDS), vinyl ethylene carbonate (VEC), butanedinitrile, hexanedinitrile, 1,3,6-hexanetrimethylnitrile, sodium difluorophosphate, disodium monofluorophosphate, and sodium tetrafluoroborate.

11. The electrolyte according to any one of claims 1 to 10, wherein the electrolyte further comprises 5wt% to 20wt% of a sodium salt based on a total mass of the electrolyte.

12. The electrolyte according to any one of claims 1 to 10, wherein the electrolyte further comprises 5wt% to 20wt% of a lithium salt based on a total mass of the electrolyte.

13. The electrolyte according to any one of claims 1 to 12, wherein the electrolyte further comprises 75wt% to 90wt% of a non-aqueous solvent based on the total mass of the electrolyte.

14. A secondary battery comprising the electrolyte according to any one of claims 1 to 13.

15. An electronic device comprising the secondary battery according to claim 14.

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