Electrolyte and battery

Abstract

The invention provides an electrolyte and a battery, and relates to the technical field of batteries, the electrolyte comprises an electrolyte, a solvent and an additive, and the additive comprises a gas phase flame retardant additive and a liquid phase flame retardant additive. According to the technical scheme, the gas-phase flame-retardant additive and the liquid-phase flame-retardant additive are adopted, the gas-phase flame-retardant additive and the liquid-phase flame-retardant additive synergistically exert the flame-retardant effect, gas or liquid is released or a protective layer is formed in the combustion process, the combustion reaction is prevented from being further expanded, and therefore the flame-retardant effect is achieved; the gas-phase flame-retardant additive and the liquid-phase flame-retardant additive both have a certain degree of heat resistance, so that the heat resistance of the electrolyte can be improved, the combustion reaction of the electrolyte is not easily caused under the condition of short-circuit severe heat release of the battery, and the combustion risk of the electrolyte is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrolyte and a battery. Background Art

[0002] Sodium-ion batteries are currently widely used, especially layered oxide sodium-ion batteries, which have great advantages: higher energy density, low cost, good rate performance, and their safety is also higher than that of lithium-ion batteries.

[0003] There are still certain dangers under extreme usage conditions. At present, organic electrolytes are generally used as electrolytes for sodium-ion batteries. The commonly used organic solvents in electrolytes are carbonate compounds, such as DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), PC (propylene carbonate), etc. The flash points of these organic solvents are very low, and the electrolytes are extremely flammable. Therefore, sodium-ion batteries still have the risk of fire and combustion. Summary of the invention

[0004] The main purpose of the present invention is to provide an electrolyte and a battery, aiming to reduce the risk of spontaneous combustion of the battery.

[0005] To achieve the above object, the present invention provides an electrolyte, comprising an electrolyte, a solvent and an additive, wherein the additive comprises a gas phase flame retardant additive and a liquid phase flame retardant additive.

[0006] In one embodiment, the electrolyte includes a sodium salt, and the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bis(oxalato)borate, and sodium difluorophosphate.

[0007] In one embodiment, the total molar concentration of the sodium salt is 0.6 mol / L to 1.5 mol / L;

[0008] Preferably, the total molar concentration of the sodium salt is 0.8 mol / L to 1.2 mol / L.

[0009] In one embodiment, the gas phase flame retardant additive comprises a phosphazene compound; and / or,

[0010] The liquid phase flame retardant additive includes at least one of 1,3,5-tris[(3,3,3-trifluoropropyl)methyl]cyclotrisiloxane and perfluoro(2-methyl-3-pentanone).

[0011] In one embodiment, the additive further includes a film-forming additive.

[0012] In one embodiment, in the electrolyte, the mass percentage of the film-forming additive is 1% to 4%; and / or,

[0013] The film-forming additive includes at least two of fluoroethylene carbonate (FEC), propene sulphate (PS), diethyl sulfate (DTD) and 1,3-propene sultone (PST).

[0014] In one embodiment, the solvent includes diethyl ethylphosphonate and at least one of a phosphate compound, a fluoroether, and a fluoroester.

[0015] In one embodiment, in the electrolyte, the mass proportion of diethyl ethylphosphonate is not less than 15%.

[0016] The present invention also provides a battery, comprising the aforementioned electrolyte.

[0017] In one embodiment, the battery is a sodium ion battery, which includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte. The material of the positive electrode plate is a layered oxide, the material of the negative electrode plate is hard carbon, and the material of the separator is polypropylene, polyethylene, or a composite of polypropylene and polyethylene.

[0018] In the technical solution of the present invention, by adopting gas phase flame retardant additives and liquid phase flame retardant additives, the gas phase flame retardant additives have a higher vapor pressure and can quickly form flame retardant vapor groups to inhibit gas phase (electrolyte volatilization and decomposition produce a large amount of gas) combustion; the liquid phase flame retardant additives have a lower vapor pressure and can flame retardant in the liquid phase (unvolatile residual liquid electrolyte), and the two synergistically exert a flame retardant effect, thereby achieving a flame retardant effect. DETAILED DESCRIPTION

[0019] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0020] It should be noted that, in the embodiments, those without specifying specific conditions are carried out according to normal conditions or conditions recommended by the manufacturer. Those without specifying the manufacturer of reagents or instruments used are conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes, and "A and / or B" is taken as an example, including schemes A, B, or A and B that meet the same time. In addition, the technical schemes between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in the field to achieve. When the combination of the technical schemes is contradictory or cannot be achieved, it should be considered that the combination of such technical schemes does not exist, and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work, all belong to the scope of protection of the present invention.

[0021] Sodium-ion batteries are currently widely used, especially layered oxide sodium-ion batteries, which have great advantages: higher energy density, low cost, good rate performance, and their safety is also higher than that of lithium-ion batteries.

[0022] There are still certain dangers under extreme usage conditions. At present, organic electrolytes are generally used as electrolytes for sodium-ion batteries. The commonly used organic solvents in electrolytes are carbonate compounds, such as DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), PC (propylene carbonate), etc. The flash points of these organic solvents are very low, and the electrolytes are extremely flammable. Therefore, sodium-ion batteries still have the risk of fire and combustion.

[0023] In view of this, the present invention provides an electrolyte, comprising an electrolyte, a solvent and an additive, wherein the additive comprises a gas phase flame retardant additive and a liquid phase flame retardant additive.

[0024] In the technical solution of the present invention, by adopting gas-phase flame retardant additives and liquid-phase flame retardant additives, the two synergistically exert a flame retardant effect. At the same time, both the gas-phase flame retardant additives and the liquid-phase flame retardant additives have a certain degree of heat resistance, can effectively absorb heat, reduce the volatilization of the electrolyte or decomposition at high temperature, thereby improving the thermal stability of the electrolyte, making it difficult for the battery to trigger a combustion reaction of the electrolyte even when the battery is short-circuited and releases heat violently, thereby reducing the combustion risk of the electrolyte; wherein, the gas-phase flame retardant additive has a high vapor pressure and can quickly form a flame-retardant vapor group, thereby effectively inhibiting the combustion process; the liquid-phase flame retardant additive prevents the combustion of the remaining electrolyte, further improving the flame retardant performance of the electrolyte.

[0025] In one embodiment, the electrolyte includes a sodium salt, and the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bis(oxalato)borate, and sodium difluorophosphate.

[0026] In the technical solution of the present invention, by adopting sodium salt as the electrolyte, the electrolyte can be used as the electrolyte of a sodium ion battery and can be applied to a sodium ion battery to reduce the risk of spontaneous combustion of the sodium ion battery; by adopting at least one of the above-mentioned sodium salts, the sodium salt is given higher thermal stability to prevent the electrolyte from decomposing or volatilizing, thereby ensuring the safety and reliability of the battery in a high temperature environment; in addition, the sodium salt as an electrolyte can also form a stable passivation film on the electrode surface of the battery during the application process of the battery, reduce the side reaction between the electrode and the electrolyte, improve the stability and conductivity of the electrode interface, thereby improving the charge and discharge efficiency and cycle life of the battery.

[0027] In one embodiment, the total molar concentration of the sodium salt is 0.6 mol / L to 1.5 mol / L.

[0028] In the technical solution of the present invention, by limiting the total molar concentration of the sodium salt to 0.6 mol / L to 1.5 mol / L, sufficient ion concentration is provided to ensure that the electrolyte has good electrical conductivity and electrochemical properties, reduce the interaction between ions, improve the fluidity of the electrolyte, and enhance the conductive properties of the electrolyte.

[0029] Preferably, the total molar concentration of the sodium salt is 0.8 mol / L to 1.2 mol / L.

[0030] In the technical solution of the present invention, by limiting the total molar concentration of the sodium salt to 0.8 mol / L to 1.2 mol / L, the performance of the electrolyte is better, which can ensure sufficient ion concentration without causing excessive aggregation between ions, thereby reducing the occurrence of excessive viscosity of the electrolyte or precipitation of solid precipitation.

[0031] In one embodiment, the gas phase flame retardant additive includes a phosphazene compound. In the technical solution of the present invention, by using a phosphazene compound as a gas phase flame retardant additive, the rapidly formed flame retardant vapor group retards the volatile combustibles (the electrolyte volatilizes or decomposes to generate combustible gases).

[0032] In one embodiment, the liquid phase flame retardant additive includes at least one of 1,3,5-tris[(3,3,3-trifluoropropyl)methyl]cyclotrisiloxane and perfluoro(2-methyl-3-pentanone). In the technical solution of the present invention, by using at least one of 1,3,5-tris[(3,3,3-trifluoropropyl)methyl]cyclotrisiloxane and perfluoro(2-methyl-3-pentanone) as the liquid phase flame retardant additive, it has a high boiling point and low volatility, can effectively flame retard the non-volatile residual electrolyte, and reduce the risk of combustion; at the same time, the liquid phase flame retardant additive has excellent thermal stability, can maintain its physical and chemical properties at high temperatures, and prevent the electrolyte from decomposing or volatilizing.

[0033] Specifically, in some embodiments of the present invention, the phosphazene compound includes ethoxy (pentafluoro) cyclotriphosphazene or hexafluorocyclotriphosphazene.

[0034] In one embodiment, the additive further includes a film-forming additive.

[0035] In the technical solution of the present invention, by adding film-forming additives, a uniform and stable passivation film can be formed on the electrode surface, reducing the side reactions between the electrode and the electrolyte, improving the stability and conductivity of the electrode interface, and thus further improving the charge and discharge efficiency and cycle life of the battery.

[0036] In one embodiment, the mass proportion of the film-forming additive in the electrolyte is 1% to 4%. In the technical solution of the present invention, by setting the mass proportion of the film-forming additive to 1% to 4%, the film-forming additive can form a uniform and stable passivation film on the electrode surface of the battery, effectively reducing the side reaction between the electrode and the electrolyte, and improving the stability and conductivity of the electrode interface. At the same time, the film-forming additive can also reduce the decomposition and gas production of the electrolyte, reduce the internal pressure of the battery, and improve the overall safety performance of the battery.

[0037] In one embodiment, the film-forming additive includes at least two of fluoroethylene carbonate (FEC), propene sulphate (PS), diethyl sulfate (DTD) and 1,3-propene sultone (PST).

[0038] In the technical solution of the present invention, by adopting at least two film-forming additives, at least two film-forming agents can play a synergistic role to form protective films on the positive and negative electrodes of the battery respectively. For example, when fluoroethylene carbonate (FEC) and diethylene sulfate (DTD) are used in combination, FEC can form a stable SEI film on the surface of the negative electrode, and DTD can form a stable passivation film on the surface of the positive electrode, thereby comprehensively improving the electrochemical performance of the battery; wherein, FEC can form a stable SEI film (solid electrolyte interface film) on the electrode surface, reduce the side reaction between the electrode and the electrolyte, and improve the cycle stability and rate performance of the battery; PS can form a uniform protective film on the electrode surface, reduce the decomposition of the electrolyte, and improve the cycle life and safety of the battery; DTD can form a stable passivation film on the electrode surface, reduce the side reaction between the electrode and the electrolyte, and improve the cycle stability and rate performance of the battery; PST can form a uniform and stable passivation film on the electrode surface, reduce the decomposition of the electrolyte, and improve the cycle life and safety of the battery.

[0039] In one embodiment, the solvent includes diethyl ethylphosphonate (DEEP) and at least one of a phosphate compound, a fluoroether, and a fluoroester.

[0040] In the technical solution of the present invention, diethyl ethylphosphonate and at least one of phosphate compounds, fluoroethers and fluoroesters are used as solvents to improve the thermal stability of the solvent, so that the physical and chemical properties of the solvent can be maintained under high temperature conditions, and the electrolyte can be prevented from decomposing or volatilizing, thereby ensuring the stability and safety of the electrolyte under high temperature environments; wherein DEEP, phosphate compounds, fluoroethers and fluoroesters all have good electrochemical stability and high dielectric constants, can provide good ion transport performance, and improve the conductivity of the electrolyte. At the same time, DEEP can form a stable SEI film on the electrode surface, reduce the side reactions between the electrode and the electrolyte, and improve the cycle stability and rate performance of the battery;

[0041] In one embodiment, in the electrolyte, the mass proportion of diethyl ethylphosphonate is not less than 15%.

[0042] In the technical solution of the present invention, since DEEP has high thermal stability, high phosphorus content and good flame retardant effect, when the mass proportion of DEEP is not less than 15%, the thermal stability of the electrolyte is significantly improved, ensuring the safety and reliability of the battery in a high temperature environment.

[0043] The present invention also provides a battery, comprising the aforementioned electrolyte.

[0044] In the technical solution of the present invention, by adopting the electrolyte as mentioned above to prepare the battery, excellent electrochemical performance, thermal stability and safety performance are achieved, and the cycle life, charge and discharge efficiency and low temperature performance of the battery are significantly improved, which has important practical significance and broad application prospects.

[0045] In one embodiment, the battery is a sodium ion battery, which includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte. The material of the positive electrode plate is a layered oxide, the material of the negative electrode plate is hard carbon, and the material of the separator is polypropylene, polyethylene, or a composite of polypropylene and polyethylene.

[0046] In the technical solution of the present invention, by adopting layered oxide as the positive electrode material, it has a high theoretical specific capacity and good cycle stability, can be used to provide a stable sodium ion embedding and de-embedding process, improve the overall performance of the battery, so as to improve the theoretical specific capacity and cycle stability of the sodium ion battery; by adopting hard carbon as the negative electrode material, the hard carbon material can provide stable sodium ion embedding and de-embedding sites during the charge and discharge process, reduce the volume change of the electrode material, and improve the cycle life and rate performance of the battery; by adopting a composite material as the material of the diaphragm, it can maintain its physical and chemical properties under high temperature conditions to prevent short circuit and thermal runaway.

[0047] In one embodiment, the positive electrode dressing of the positive electrode sheet includes layered oxide, carbon black, carbon nanotubes, polyvinylidene fluoride and positive electrode solid electrolyte, wherein the mass ratio of layered oxide, carbon black, carbon nanotubes, polyvinylidene fluoride and positive electrode solid electrolyte is 92:2:1.5:2.5:2. In the technical scheme of the present invention, layered oxide as positive electrode active material has high theoretical specific capacity and good cycle stability. This material can provide a stable sodium ion insertion and deinsertion process, and improve the overall energy density of the battery; carbon black and carbon nanotubes as conductive agents can be evenly distributed in the positive electrode active material, improve the conductivity of the positive electrode material, reduce the resistance inside the electrode, and improve the charge and discharge efficiency of the battery; carbon nanotubes have excellent conductivity and mechanical properties, can form a three-dimensional conductive network, further improve the conductivity and structural stability of the positive electrode material, and improve the rate performance of the battery; polyvinylidene fluoride as a binder can evenly fix the positive electrode active material, conductive agent and solid electrolyte together to form a stable coating, and improve the mechanical strength and conductivity of the positive electrode sheet.

[0048] In one embodiment, the negative electrode dressing of the negative electrode plate includes hard carbon, carbon black, styrene butadiene rubber, sodium carboxymethyl cellulose and a negative electrode solid electrolyte, wherein the mass ratio of hard carbon, carbon black, styrene butadiene rubber, sodium carboxymethyl cellulose and a negative electrode solid electrolyte is 92.5:2:2.5:1:2. In the technical solution of the present invention, hard carbon as a negative electrode active material has a high specific capacity and good cycle stability. Hard carbon materials can provide stable sodium ion embedding and de-embedding sites during the charge and discharge process, reduce the volume change of electrode materials, and improve the cycle life and rate performance of the battery; carbon black, as a conductive agent, can be evenly distributed in the hard carbon material, improve the conductivity of the negative electrode material, reduce the internal resistance of the electrode, and improve the charge and discharge efficiency of the battery; styrene-butadiene rubber (SBR) as a binder has good bonding properties and mechanical strength, and can evenly fix the negative electrode active material, conductive agent and solid electrolyte together to form a stable coating, thereby improving the mechanical strength and conductivity of the negative electrode sheet; sodium carboxymethyl cellulose (CMC) as a thickener can improve the stability and coating performance of the slurry, ensure that the negative electrode material is evenly distributed during the coating process, reduce particle agglomeration, and improve the consistency and performance of the negative electrode sheet.

[0049] In one embodiment, the positive electrode solid electrolyte and the negative electrode solid electrolyte both include a solid electrolyte, and the chemical formula of the solid electrolyte is Na l+x Zr2Si x P 3-x O 12 (0≤x≤3), wherein the solid content of the positive electrode solid electrolyte is 30%, the dispersant is N-methylpyrrolidone, and the solid content of the negative electrode solid electrolyte is 30%, and the dispersant is water. l+xZr2Si x P 3-x O 12 As the solid electrolyte, it has a high sodium ion conductivity, can provide good ion transmission performance, and improve the charge and discharge efficiency and rate performance of the battery; by using N-methylpyrrolidone as a dispersant for the positive electrode solid electrolyte, it can effectively dissolve binders such as polyvinylidene fluoride, so that the positive electrode active material, conductive agent and binder are evenly dispersed in the slurry.

[0050] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0051] Experimental Materials

[0052] Unless otherwise specified, all reagents used without indicating the manufacturer are conventional products that can be purchased commercially.

[0053] DEEP: diethyl ethylphosphonate;

[0054] TMP: trimethyl phosphate;

[0055] TFP: tris(2,2,2-trifluoroethyl)phosphate;

[0056] TTE: 1,1,2,2-tetrafluoroethyl-2,2,3-tetrafluoropropyl ether;

[0057] CDP: Cresyl diphenyl phosphate;

[0058] NaPF6: sodium hexafluorophosphate;

[0059] NaFSI: sodium bis(fluorosulfonyl)imide;

[0060] HFPN: hexafluorocyclotriphosphazene;

[0061] D3F: 1,3,5-tris[(3,3,3-trifluoropropyl)methyl]cyclotrisiloxane;

[0062] PFPN: ethoxy(pentafluoro)cyclotriphosphazene;

[0063] PFMP: perfluoro(2-methyl-3-pentanone);

[0064] FEC: fluoroethylene carbonate;

[0065] PS: acrylic acid ester;

[0066] DTD: diethyl sulphate;

[0067] TMSB: 2-methyl-3-pentanone;

[0068] EMC: ethyl methyl carbonate;

[0069] PC: propylene carbonate.

[0070] Example 1

[0071] This embodiment provides an electrolyte, the composition of the electrolyte is:

[0072] DEEP:TMP:CDP:NaPF6:NaFSI:PFPN:PFMP:FEC:PS:DTD:TMSB=15%:35%:25.8%:10%:4%:6%:2%:1%:0.5%:0.5%:0.2%.

[0073] Example 2

[0074] This embodiment provides an electrolyte, and the electrolyte composition is:

[0075] DEEP:TMP:CDP:TTE:NaPF6:NaFSI:HFPN:D3F:FEC:PS:DTD:TMSB=15%:25%:25.8%:10%:10%:4%:5%:3%:1%:0.5%:0.5%:0.2%.

[0076] Example 3

[0077] This embodiment provides an electrolyte, and the electrolyte composition is:

[0078] DEEP:TFP:CDP:TTE:NaPF6:NaFSI:HFPN:D3F:FEC:PS:DTD:TMSB=15%:35%:25.8%:10%:4%:5%:3%:1%:0.5%:0.5%:0.2%.

[0079] Comparative Example 1

[0080] This comparative example provides an electrolyte, the electrolyte composition is:

[0081] EMC: PC: NaPF6: NaFSI: PFPN: PFMP: FEC: PS: DTD: TMSB = 50%: 10%: 15.8%: 10%: 4%: 6%: 2%: 1%: 0.5%: 0.5%: 0.2%.

[0083] The electrolyte provided in this comparative example does not contain solvents such as diethyl ethylphosphonate, phosphate compounds, fluoroethers, and fluoroesters.

[0084] Comparative Example 2

[0085] This comparative example provides an electrolyte, the electrolyte composition is:

[0086] TFP:PC:EMC:NaPF6:NaFSI:PFPN:PFMP:FEC:PS:DTD:TMSB=50%:10%:15.8%:10%:4%:6%:2%:1%:0.5%:0.5%:0.2%.

[0087] The electrolyte provided in this comparative example does not contain diethyl ethylphosphonate solvent.

[0088] Comparative Example 3

[0089] This comparative example provides an electrolyte, the electrolyte composition is:

[0090] TMP:CDP:NaPF6:NaFSI:PFPN:FEC:PS:DTD:TMSB=58%:25.8%:10%:4%:2%::1%:0.5%:0.5%:0.2%.

[0091] The electrolyte provided in this comparative example does not contain diethyl ethylphosphonate and liquid phase flame retardant additives.

[0092] Comparative Example 4

[0093] This comparative example provides an electrolyte, the electrolyte composition is:

[0094] DEEP:TMP:CDP:NaPF6:NaFSI:PFPN:FEC:PS:DTD:TMSB=16%:38%:27.5%:10%:4%:2%:1%:0.6%:0.6%:0.3%.

[0095] Compared with Example 1, this comparative example does not contain PFMP.

[0096] The electrolyte of Comparative Example 4 is in the form of an emulsion, contains insoluble particles, and cannot be used directly.

[0097] Comparative Example 5

[0098] This comparative example provides an electrolyte, the electrolyte composition is:

[0099] DEEP:TMP:CDP:NaPF6:NaFSI:PFMP:FEC:PS:DTD:TMSB=16%:37.5%:26%:10%:6%:2%:1%:0.6%:0.6%:0.3%.

[0100] Compared with Example 1, this comparative example does not contain PFMP.

[0101] The electrolyte of Comparative Example 5 is in a slurry state, contains insoluble particles, and cannot be used directly.

[0102] The electrolytes prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively injected into the same batch of cylindrical sodium ion batteries, wherein the positive electrode material of the cylindrical sodium ion battery was layered oxide, the negative electrode material of the cylindrical sodium ion battery was hard carbon, and the separator material of the cylindrical sodium ion battery was polypropylene, polyethylene, or a composite of polypropylene and polyethylene; the positive electrode dressing of the cylindrical sodium ion battery was composed of: 92% layered oxide, 2% carbon black, 1.5% carbon nanotubes, 2.5% polyvinylidene fluoride, and 2% positive electrode electrolyte dispersion; the negative electrode slurry of the cylindrical sodium ion battery was composed of: 92.5% hard carbon, 2% carbon black, 2.5% styrene-butadiene rubber, 1% sodium carboxymethyl cellulose, and 2% negative electrode electrolyte dispersion; wherein the solid electrolyte of the positive electrode electrolyte dispersion and the negative electrode electrolyte dispersion was Na3Zr2Si2PO 12 The mass proportion of the solid electrolyte in the positive electrode electrolyte dispersion is 30%, and the dispersant is N-methylpyrrolidone. The mass proportion of the solid electrolyte in the negative electrode electrolyte dispersion is 30%, and the dispersant is water.

[0103] The capacities of the batteries prepared using the electrolytes of Examples 1 to 3 and Comparative Examples 1 to 3 were tested. After being divided into different capacities, the batteries were fully charged and subjected to needle puncture tests. The test results are shown in Table 1.

[0104] Table 1 Battery capacity and puncture test results

[0105]

[0106]

[0107] It can be seen from Table 1 that Examples 1 to 3 did not catch fire, while Comparative Examples 1 to 3 all caught fire; in addition, it can be seen from Comparative Example 1 that the battery capacity is slightly higher when using carbonate solvents, and flame retardant solvents such as phosphates will slightly reduce the battery capacity.

[0108] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An electrolyte, characterized in that: The invention comprises an electrolyte, a solvent and an additive, wherein the additive comprises a gas phase flame retardant additive and a liquid phase flame retardant additive.

2. The electrolyte according to claim 1, characterized in that The electrolyte includes a sodium salt, and the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bis(oxalato)borate and sodium difluorophosphate.

3. The electrolyte according to claim 2, characterized in that The total molar concentration of the sodium salt is 0.6 mol / L to 1.5 mol / L; Preferably, the total molar concentration of the sodium salt is 0.8 mol / L to 1.2 mol / L.

4. The electrolyte according to claim 1, characterized in that The gas phase flame retardant additive comprises a phosphazene compound; and / or, The liquid phase flame retardant additive includes at least one of 1,3,5-tris[(3,3,3-trifluoropropyl)methyl]cyclotrisiloxane and perfluoro(2-methyl-3-pentanone).

5. The electrolyte according to claim 1, characterized in that The additives also include film-forming additives.

6. The electrolyte according to claim 5, characterized in that In the electrolyte, the mass proportion of the film-forming additive is 1% to 4%; and / or, The film-forming additive includes at least two of fluoroethylene carbonate (FEC), propene sulphate (PS), diethyl sulfate (DTD) and 1,3-propene sultone (PST).

7. The electrolyte according to claim 1, characterized in that The solvent includes diethyl ethylphosphonate and at least one of a phosphate compound, a fluoroether and a fluoroester.

8. The electrolyte according to claim 1, characterized in that In the electrolyte, the mass proportion of diethyl ethylphosphonate is not less than 15%.

9. A battery, characterized in that: Comprising the electrolyte according to any one of claims 1 to 8.

10. The battery according to claim 9, characterized in that The battery is a sodium ion battery, which includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte. The material of the positive electrode plate is a layered oxide, the material of the negative electrode plate is hard carbon, and the material of the separator is polypropylene, polyethylene, or a composite of polypropylene and polyethylene.

Images