Electrolyte and carbon fluoride battery

Abstract

The invention provides an electrolyte and a carbon fluoride battery. The electrolyte is prepared from the following components in percentage by mass: 0.01 to 1 percent of anhydride additive, 0.1 to 5 percent of silane additive, 0.1 to 10 percent of fluoroalkane and the balance of organic solvent and lithium salt, wherein the chemical formula of the silane additive is (R1) bSia (R2) 2a + 2-b, a is 1 or 2, b is an integer from 1 to 6, 2a + 2-b is an integer from 0 to 5, R1 is selected from any one of substituted or unsubstituted C2-C10 alkenyl groups, and R2 is selected from any one of substituted or unsubstituted C1-10 alkyl groups. And the contents of the anhydride additive, the silane additive and the fluoroalkane are controlled in the range, so that the synergistic effect among the components can be fully exerted, and the stability of the carbon fluoride battery under long-term and high-temperature storage conditions can be further improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrolyte and a carbon fluoride battery. Background Art

[0002] There are some unstable carbon-fluorine bonds in fluorinated carbon materials. Under high temperature or long-term storage, these unstable carbon-fluorine bonds will undergo homolytic or heterolytic cleavage to form carbon free radicals, fluorine free radicals or carbon cations, fluoride ions, which have high chemical activity and can easily cause the decomposition of the electrolyte, resulting in rapid decay of the battery capacity.

[0003] The Chinese patent application with the patent application publication number CN114175320A discloses that the stability of negative electrode metal lithium can be improved by introducing fluorocarbonate into the electrolyte, and the side reaction between metal lithium and electrolyte during storage can be inhibited, thereby reducing the self-discharge of the battery and improving the stability of the battery during storage. Although fluorocarbonate can improve the stability of negative electrode metal lithium and inhibit the decomposition of electrolyte, it cannot solve the problem of reaction between positive electrode carbon fluoride and electrolyte, and the improvement effect is limited.

[0004] The Chinese patent application with the patent application publication number CN114628670A discloses the application of nitrogen-doped-carbon-coated fluorinated carbon in lithium / fluorinated carbon battery. In the patent, an aqueous solution of trishydroxymethylaminomethane is used as a buffer, and a polydopamine fluorinated carbon composite material is first obtained through the self-polymerization reaction of dopamine hydrochloride. The composite material is calcined under an inert atmosphere to obtain a nitrogen-doped-carbon-coated fluorinated carbon electrode material. The coating of the surface carbon layer blocks the direct contact between the electrolyte and the fluorinated carbon, reduces the self-discharge phenomenon of the battery, and improves the high-temperature shelf performance of the battery. However, the preparation process of the fluorinated carbon surface coating is complicated and costly, which is not conducive to large-scale production. Summary of the invention

[0005] The main purpose of the present application is to provide an electrolyte and a carbon fluoride battery to solve the problem of poor stability of carbon fluoride batteries in high-temperature storage in the prior art.

[0006] In order to achieve the above-mentioned object, according to one aspect of the present application, an electrolyte is provided, which comprises, by mass percentage, 0.01-1% of anhydride additives, 0.1-5% of silane additives, 0.1-10% of fluoroalkane, and the remainder of organic solvent and lithium salt; wherein the chemical formula of the silane additive is (R1) b Si a (R2) 2a+2-b , wherein a is 1 or 2, b is an integer from 1 to 6, 2a+2-b is an integer from 0 to 5, and R1 is selected from substituted or unsubstituted C2 to C 10Any of the alkenyl groups, R2 is selected from substituted or unsubstituted C1 to C 10 Any of the alkyl groups.

[0007] Further, the above b is an integer from 1 to 4; and / or 2a+2-b is an integer from 0 to 4; and / or R1 is selected from any one of substituted or unsubstituted C2 to C4 alkenyl groups; and / or R2 is selected from any one of substituted or unsubstituted C1 to C4 alkyl groups; further, R1 is selected from any one of vinyl, propenyl, allyl or butenyl; and / or R2 is selected from any one of methyl, ethyl, propyl or butyl; further, R1 is vinyl or allyl; and / or R2 is any one of methyl, ethyl or propyl.

[0008] Furthermore, the above-mentioned silane additive is selected from any one or more of vinyltrimethylsilane, vinyltriethylsilane, divinyldimethylsilane, divinyldipropylsilane, trivinylmethylsilane, trivinylethylsilane, tetravinylsilane, tetraallylsilane and divinyltetramethyldisilane; further, the silane additive is a combination of tetravinylsilane and divinyldimethylsilane, and the mass ratio of tetravinylsilane to divinyldimethylsilane is 1:0.1~5.

[0009] Furthermore, the fluoroalkane is selected from C4 to C 10 Any one or more of fluoroalkanes; further, the fluoroalkanes are selected from any one or more of 1,1,3,3-pentafluorobutane, 2H,3H-decafluoropentane, 1H-perfluoropentane, perfluoro-n-pentane, perfluorohexane, 1H-perfluorohexane, 1,1-difluoroheptane, 1,7-difluoroheptane and perfluorooctane; further, the fluoroalkanes are a combination of 2H,3H-decafluoropentane and 1H-perfluorohexane, and the mass ratio of 2H,3H-decafluoropentane to 1H-perfluorohexane is 1:0.1-0.5.

[0010] Furthermore, the mass ratio of the above-mentioned acid anhydride additive, silane additive and fluoroalkane is 0.5-1:1-1.5:1.

[0011] Furthermore, the concentration of lithium salt in the above electrolyte is 0.5-2 mol / L.

[0012] Further, the above-mentioned acid anhydride additive is selected from any one or more of phenyl maleic anhydride, maleic anhydride, phthalic anhydride, 2,3-pyridinedicarboxylic anhydride, succinic anhydride, biphenyl anhydride, adipic anhydride, glutaric anhydride, glutaric anhydride, benzoic anhydride, citraconic anhydride, phenoxyacetic anhydride, phenylsuccinic anhydride and NA-anhydride; further, the acid anhydride additive is phthalic anhydride.

[0013] Further, the lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium trifluoromethanesulfonate, lithium bis(oxalatoborate) and lithium bis(fluorooxalatoborate); further, the lithium salt is lithium tetrafluoroborate.

[0014] Further, the above-mentioned organic solvent is selected from any one or more of ethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and gamma-martinol; further, the organic solvent is a combination of propylene carbonate and ethylene glycol dimethyl ether, and the mass ratio of propylene carbonate to ethylene glycol dimethyl ether is 1:0.2-5.

[0015] According to another aspect of the present application, a carbon fluoride battery is provided, comprising a carbon fluoride positive electrode sheet, an electrolyte and a negative electrode sheet, wherein the electrolyte is the aforementioned electrolyte.

[0016] By applying the technical solution of the present application, anhydride additives have a strong ability to remove HF, can effectively capture free fluorine in the electrolyte, and reduce the generation of fluorine free radicals. At the same time, as an electrophilic reagent, anhydride can react electrophilically with fluorine in unstable carbon-fluoride bonds in carbon fluoride, which helps to remove unstable carbon-fluoride bonds, thereby helping to improve the stability of positive electrode materials. Silane additives contain alkenyl groups, which can react with the surface of metallic lithium to form a stable passivation layer, and at the same time, free radical polymerization or ion polymerization is carried out under the action of carbon cations or carbon free radicals, forming a passivation layer on the active surface of the positive electrode, blocking direct contact between the electrolyte and carbon fluoride, thereby helping to inhibit the decomposition of the electrolyte, and then helping to improve the high-temperature storage stability of the battery. The introduction of fluoroalkanes helps to improve the wettability of carbon fluoride electrodes, which is beneficial to maintaining the internal resistance stability of the battery. At the same time, fluoroalkanes can generate a passivation layer containing lithium fluoride on the surface of metallic lithium, enhancing the stability of metallic lithium. Controlling the contents of anhydride additives, silane additives and fluoroalkanes within the above ranges helps to fully exert the synergistic effect between the components, thereby helping to further improve the stability of carbon fluoride batteries under long-term and high-temperature storage conditions. DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below in conjunction with the embodiments.

[0018] As analyzed in the background technology of the present application, the carbon fluoride battery in the prior art has the problem of poor stability in high-temperature storage. In order to solve this problem, the present application provides an electrolyte and a carbon fluoride battery.

[0019] In a typical embodiment of the present application, an electrolyte is provided, which comprises, by mass percentage, 0.01-1% of anhydride additives, 0.1-5% of silane additives, 0.1-10% of fluoroalkane, and the remainder of organic solvent and lithium salt; wherein the chemical formula of the silane additive is (R1) b Si a (R2) 2a+2-b , wherein a is 1 or 2, b is an integer from 1 to 6, 2a+2-b is an integer from 0 to 5, and R1 is selected from substituted or unsubstituted C2 to C 10 Any of the alkenyl groups, R2 is selected from substituted or unsubstituted C1 to C 10 Any of the alkyl groups.

[0020] Anhydride additives have strong HF removal capabilities and can effectively capture free fluorine in the electrolyte and reduce the generation of fluorine free radicals. At the same time, as an electrophilic reagent, anhydride can react electrophilically with fluorine in unstable carbon-fluorine bonds in carbon fluoride, which helps to remove unstable carbon-fluorine bonds, thereby helping to improve the stability of the positive electrode material. Silane additives contain olefin groups, which can react with the surface of metallic lithium to form a stable passivation layer. At the same time, free radical polymerization or ion polymerization is carried out under the action of carbon cations or carbon free radicals to form a passivation layer on the active surface of the positive electrode, blocking direct contact between the electrolyte and carbon fluoride, thereby helping to inhibit the decomposition of the electrolyte, and then helping to improve the high-temperature storage stability of the battery. The introduction of fluoroalkanes helps to improve the wettability of carbon fluoride electrodes, which is beneficial to maintaining the stability of the internal resistance of the battery. At the same time, fluoroalkanes can form a passivation layer containing lithium fluoride on the surface of metallic lithium, enhancing the stability of metallic lithium. Controlling the contents of anhydride additives, silane additives and fluoroalkanes within the above ranges helps to fully exert the synergistic effect between the components, thereby helping to further improve the stability of carbon fluoride batteries under long-term and high-temperature storage conditions.

[0021] In order to further improve the stability of carbon fluoride batteries under long-term and high-temperature storage conditions, in one embodiment of the present application, the above b is an integer from 1 to 4; and / or, 2a+2-b is an integer from 0 to 4; and / or, R1 is selected from any one of substituted or unsubstituted C2 to C4 alkenyl; and / or, R2 is selected from any one of substituted or unsubstituted C1 to C4 alkyl; in one embodiment of the present application, R1 is selected from any one of vinyl, propenyl, allyl or butenyl; and / or, R2 is selected from any one of methyl, ethyl, propyl or butyl; in one embodiment of the present application, R1 is vinyl or allyl; and / or, R2 is any one of methyl, ethyl or propyl.

[0022] In one embodiment of the present application, the above-mentioned silane additive is selected from any one or more of vinyltrimethylsilane, vinyltriethylsilane, divinyldimethylsilane, divinyldipropylsilane, trivinylmethylsilane, trivinylethylsilane, tetravinylsilane, tetraallylsilane and divinyltetramethyldisilane; in one embodiment of the present application, the silane additive is a combination of tetravinylsilane and divinyldimethylsilane, and the mass ratio of tetravinylsilane to divinyldimethylsilane is 1:0.1~5.

[0023] Controlling the types of silane additives within the above range helps to form a more stable passivation layer on the surface of metallic lithium, thereby helping to inhibit the decomposition of the electrolyte and improve the stability of metallic lithium and the electrolyte. In addition, the above types of silane additives are more likely to undergo free radical polymerization or ion polymerization under the action of carbon cations / carbon radicals, forming a passivation layer on the active surface of the positive electrode to block the contact between the electrolyte and the carbon fluoride, thereby helping to further improve the stability of the carbon fluoride battery under long-term and high-temperature storage conditions. The combination of tetravinylsilane and divinyldimethylsilane can further improve the storage stability of the battery. Tetravinylsilane contains four vinyl groups, which will form a dense mesh passivation film when reduced at the negative electrode. During the storage process, the passivation layer gradually thickens and the impedance increases significantly. After storage, the discharge of the battery cell has a serious voltage hysteresis problem, accompanied by battery capacity loss; the passivation layer formed by divinyldimethylsilane is a linear structure, and the film stability is worse than that of tetravinylsilane. The impedance of the passivation layer formed is smaller, resulting in the long-term / high-temperature storage stability of the battery cell being weaker than that of the tetravinylsilane system; when tetravinylsilane and divinyldimethylsilane are used together, the two are reduced at the negative electrode, and the passivation layer formed is dense and has a small impedance, and the high-temperature and long-term storage stability of the battery cell is better.

[0024] In one embodiment of the present application, the fluoroalkane is selected from C4 to C 10 Any one or more of fluoroalkanes; in one embodiment of the present application, the fluoroalkanes are selected from any one or more of 1,1,3,3-pentafluorobutane, 2H,3H-decafluoropentane, 1H-perfluoropentane, perfluoro-n-pentane, perfluorohexane, 1H-perfluorohexane, 1,1-difluoroheptane, 1,7-difluoroheptane and perfluorooctane; in one embodiment of the present application, the fluoroalkanes are a combination of 2H,3H-decafluoropentane and 1H-perfluorohexane, and the mass ratio of 2H,3H-decafluoropentane to 1H-perfluorohexane is 1:0.1-0.5.

[0025] Controlling the types of fluoroalkanes within the above range will help to further improve the stability of the battery's internal resistance. The combination of 2H,3H-decafluoropentane and 1H-perfluorohexane can further improve the high-temperature and long-term storage stability of the battery cell. 2H,3H-decafluoropentane has good solubility in the electrolyte, but 2H,3H-decafluoropentane has a low boiling point and is volatile. When the content of 2H,3H-decafluoropentane in the electrolyte is high, the battery cell will have obvious gas production problems during high-temperature storage, which is not conducive to the high-temperature storage of the battery; 1H-perfluorohexane and other fluoroalkanes with longer molecular chains have very poor solubility in the electrolyte, resulting in an extremely low content of fluoroalkanes in the electrolyte, and the role of fluoroalkanes cannot be played; 2H,3H -Decafluoropentane can improve the solubility of long-chain fluorinated alkanes in the electrolyte. When 2H,3H-decafluoropentane and 1H-perfluorohexane are used together, the content of 2H,3H-decafluoropentane in the electrolyte decreases, and the content of 1H-perfluorohexane increases. 2H,3H-decafluoropentane improves the wettability of the fluorinated carbon electrode. 1H-perfluorohexane can form an adsorption layer on the surface of the fluorinated carbon electrode to improve the stability of the fluorinated carbon electrode. 2H,3H-decafluoropentane and 1H-perfluorohexane are reduced at the negative electrode to form a passivation layer containing LiF, and the stability of metallic lithium is further improved, so that the storage stability of the battery cell is further improved.

[0026] In one embodiment of the present application, the mass ratio of the above-mentioned acid anhydride additives, silane additives and fluoroalkane is 0.5-1:1-1.5:1.

[0027] The function of anhydride additives in the electrolyte is to capture free fluorine and remove unstable carbon-fluorine bonds, while silane additives form a stable passivation layer on the electrode surface, and fluoroalkanes enhance electrode wettability and generate a passivation layer containing lithium fluoride. Controlling the mass ratio of anhydride additives, silane additives and fluoroalkanes within the above range helps to form a synergistic chemical environment inside the battery, helps to reduce the occurrence of side reactions, and thus helps to improve the stability of carbon fluoride batteries under long-term and high-temperature storage conditions.

[0028] In one embodiment of the present application, the concentration of lithium salt in the above electrolyte is 0.5-2 mol / L.

[0029] A higher lithium salt concentration helps to improve the conductivity of the electrolyte, but too high a lithium salt concentration can easily increase the viscosity of the electrolyte, hinder ion conduction, and may also cause local overheating of the electrolyte, affecting the overall performance and safety of the battery. Controlling the concentration of lithium salt in the electrolyte within the above range helps to control the viscosity of the electrolyte within an appropriate range while making the electrolyte have a higher conductivity, which helps to efficiently and stably transmit lithium ions inside the battery.

[0030] In one embodiment of the present application, the above-mentioned acid anhydride additive is selected from any one or more of phenyl maleic anhydride, maleic anhydride, phthalic anhydride, 2,3-pyridinedicarboxylic anhydride, succinic anhydride, biphenyl anhydride, adipic anhydride, glutaric anhydride, glutaric anhydride, benzoic anhydride, citraconic anhydride, phenoxyacetic anhydride, phenylsuccinic anhydride and NA-anhydride; in one embodiment of the present application, the acid anhydride additive is phthalic anhydride.

[0031] Controlling the type of anhydride additive within the above range, especially controlling the anhydride additive to be phthalic anhydride, helps to improve the efficiency of removing unstable carbon-fluorine bonds, thereby helping to further improve the stability of carbon fluoride batteries under long-term and high-temperature storage conditions.

[0032] In order to further improve the conductivity of the electrolyte, in one embodiment of the present application, the above-mentioned lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium trifluoromethanesulfonate, lithium bis(oxalatoborate) and lithium bis(fluorooxalatoborate); in one embodiment of the present application, the lithium salt is lithium tetrafluoroborate.

[0033] In one embodiment of the present application, the above-mentioned organic solvent is selected from any one or more of ethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and gamma-martinol; in one embodiment of the present application, the organic solvent is a combination of propylene carbonate and ethylene glycol dimethyl ether, and the mass ratio of propylene carbonate to ethylene glycol dimethyl ether is 1:0.2~5.

[0034] Controlling the type of organic solvent within the above range helps to improve the solubility of lithium salt in the organic solvent, thereby helping to improve the stability and conductivity of the electrolyte. Controlling the mass ratio of propylene carbonate and ethylene glycol dimethyl ether within the above range helps to give full play to the synergistic effect between the two, improve the wettability of the positive electrode fluorinated carbon material, and promote the uniform distribution of lithium ions in the positive electrode material, thereby helping to improve the stability of the fluorinated carbon battery under long-term and high-temperature storage conditions.

[0035] In one embodiment of the present application, the electrolyte includes an organic solvent, a lithium salt, an anhydride additive, a silane additive and a fluoroalkane, wherein the organic solvent is a mixture of propylene carbonate and ethylene glycol dimethyl ether, the mass ratio of propylene carbonate to ethylene glycol dimethyl ether is 1:0.2, the lithium salt is lithium tetrafluoroborate, the concentration of the lithium salt in the electrolyte is 1 mol / L, the anhydride additive is phthalic anhydride, the mass content of the anhydride additive in the electrolyte is 0.5%, the silane additive is a combination of tetravinylsilane and divinyldimethylsilane, and the mass ratio of tetravinylsilane to divinyldimethylsilane is 1:0.1, the mass content of the silane additive in the electrolyte is 1.5%, the fluoroalkane is a combination of 2H, 3H-decafluoropentane and 1H-perfluorohexane, and the mass ratio of 2H, 3H-decafluoropentane to 1H-perfluorohexane is 1:0.1, and the mass content of the fluoroalkane in the electrolyte is 1%.

[0036] In one embodiment of the present application, the electrolyte includes an organic solvent, a lithium salt, an anhydride additive, a silane additive and a fluoroalkane, wherein the organic solvent is a mixture of propylene carbonate and ethylene glycol dimethyl ether, the mass ratio of propylene carbonate to ethylene glycol dimethyl ether is 1:5, the lithium salt is lithium tetrafluoroborate, the concentration of the lithium salt in the electrolyte is 1 mol / L, the anhydride additive is phthalic anhydride, the mass content of the anhydride additive in the electrolyte is 0.1%, the silane additive is a combination of tetravinylsilane and divinyldimethylsilane, and the mass ratio of tetravinylsilane to divinyldimethylsilane is 1:5, the mass content of the silane additive in the electrolyte is 1.9%, the fluoroalkane is a combination of 2H, 3H-decafluoropentane and 1H-perfluorohexane, and the mass ratio of 2H, 3H-decafluoropentane to 1H-perfluorohexane is 1:0.5, and the mass content of the fluoroalkane in the electrolyte is 1%.

[0037] In another typical embodiment of the present application, a carbon fluoride battery is provided, comprising a carbon fluoride positive electrode sheet, an electrolyte and a negative electrode sheet, wherein the electrolyte is the aforementioned electrolyte.

[0038] Since the above-mentioned carbon fluoride battery contains the electrolyte of the present application, the carbon fluoride battery has high stability under long-term and high-temperature storage conditions.

[0039] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0040] Example 1

[0041] In an argon atmosphere glove box with a water content of less than 10 ppm, propylene carbonate and ethylene glycol dimethyl ether are mixed in a mass ratio of 1:0.2 to obtain an organic solvent, and then lithium salt, anhydride additives, silane additives and fluoroalkane are added to the organic solvent and mixed to obtain an electrolyte, wherein the lithium salt is lithium tetrafluoroborate, and the concentration of the lithium salt in the electrolyte is 1 mol / L, the anhydride additive is phthalic anhydride, and the mass content of the anhydride additive in the electrolyte is 0.5%, the silane additive is tetravinylsilane, and the mass content of the silane additive in the electrolyte is 1.5%, and the fluoroalkane is decafluoropentane, and the mass content of the fluoroalkane in the electrolyte is 1%.

[0042] Example 2

[0043] The difference from Example 1 is that the silane additive is a combination of tetravinylsilane and divinyldimethylsilane, and the mass ratio of tetravinylsilane to divinyltetramethyldisilane is 1:0.1, and an electrolyte is finally obtained.

[0044] Example 3

[0045] The difference from Example 1 is that the silane additive is a combination of tetravinylsilane and divinyldimethylsilane, and the mass ratio of tetravinylsilane to divinyltetramethyldisilane is 1:5, and an electrolyte is finally obtained.

[0046] Example 4

[0047] The difference from Example 1 is that the fluoroalkane is a combination of 2H,3H-decafluoropentane and 1H-perfluorohexane, and the mass ratio of 2H,3H-decafluoropentane to 1H-perfluorohexane is 1:0.1, and an electrolyte is finally obtained.

[0048] Example 5

[0049] The difference from Example 1 is that the fluoroalkane is a combination of 2H,3H-decafluoropentane and 1H-perfluorohexane, and the mass ratio of 2H,3H-decafluoropentane to 1H-perfluorohexane is 1:0.5, and an electrolyte is finally obtained.

[0050] Example 6

[0051] The difference from Example 1 is that the mass content of the anhydride additive in the electrolyte is 1%, the mass content of the silane additive is tetravinylsilane, and the mass content of the silane additive in the electrolyte is 1%, and finally an electrolyte is obtained.

[0052] Example 7

[0053] The difference from Example 1 is that the mass content of the anhydride additive in the electrolyte is 0.1%, the mass content of the silane additive is tetravinylsilane, and the mass content of the silane additive in the electrolyte is 1.9%, and finally an electrolyte is obtained.

[0054] Example 8

[0055] The difference from Example 1 is that the mass ratio of propylene carbonate to ethylene glycol dimethyl ether is 1:5, and an electrolyte is finally obtained.

[0056] Example 9

[0057] The difference from Example 1 is that the mass ratio of propylene carbonate to ethylene glycol dimethyl ether is 1:7, and an electrolyte is finally obtained.

[0058] Example 10

[0059] The difference from Example 1 is that the concentration of lithium salt in the electrolyte is 0.5 mol / L, the mass content of anhydride additives in the electrolyte is 0.01%, the mass content of silane additives in the electrolyte is 0.1%, and the mass content of fluoroalkane in the electrolyte is 10%, and finally an electrolyte is obtained.

[0060] Embodiment 11

[0061] The difference from Example 1 is that the concentration of lithium salt in the electrolyte is 2 mol / L, the mass content of anhydride additives in the electrolyte is 1%, the mass content of silane additives in the electrolyte is 5%, and the mass content of fluoroalkane in the electrolyte is 0.1%, and finally an electrolyte is obtained.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that no fluoroalkane is added to finally obtain an electrolyte.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that no silane additive is added to finally obtain an electrolyte.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that the mass content of the anhydride additive in the electrolyte is 2%, the mass content of the silane additive in the electrolyte is 10%, and the mass content of the fluoroalkane in the electrolyte is 0.01%, and finally an electrolyte is obtained.

[0068] Preparation of positive electrode sheet: The carbon fluoride active material, conductive agent and binder solution are mixed according to the mass ratio of carbon fluoride active material, conductive agent and binder of 87:8:5 to form a high viscosity slurry with a viscosity of 12000cp, which is coated on the carbon-coated aluminum foil, one side is coated once, and then the other side is coated once. The coating thickness is 100μm, and the electrode load is 120g / m 2 After drying at 100℃, roller compaction, compaction density is 1.26g / cm 3 , the porosity is 52%, and it is cut or die-cut into corresponding sizes to obtain a fluorinated carbon positive electrode sheet.

[0069] Battery assembly: The lithium ribbon is cut into corresponding sizes to obtain a negative lithium sheet with a thickness of 50 μm, and the above-mentioned carbon fluoride positive electrode sheet, metal lithium negative electrode sheet and separator are assembled into a battery by lamination, and the electrolyte prepared in the embodiment and the comparative example is injected into the battery cell with an injection coefficient of 1.6 g / Ah. After sealing, a lithium carbon fluoride battery is obtained.

[0070] The prepared lithium carbon fluoride battery was discharged at room temperature at 0.01C, with a discharge cut-off voltage of 1.5V, and the discharge capacity and internal resistance R1 of the new battery were recorded; the lithium carbon fluoride battery was placed in a 70°C oven for storage for 1 month, and then tested under the above conditions and the discharge capacity and internal resistance R2 of the battery after high-temperature storage were recorded; discharge capacity retention rate = (discharge capacity of the battery after high-temperature storage / discharge capacity of the new battery) × 100%; internal resistance growth rate = [(internal resistance R2 after storage-internal resistance R1 before storage) / internal resistance R1 before storage] × 100%.

[0071] The lithium carbon fluoride batteries prepared in the examples and comparative examples were subjected to the above tests, and the results of the discharge capacity retention rate and the internal resistance growth rate are shown in Table 1.

[0072] Table 1

[0073]

[0074] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0075] Anhydride additives have strong HF removal capabilities and can effectively capture free fluorine in the electrolyte and reduce the generation of fluorine free radicals. At the same time, as an electrophilic reagent, anhydride can react electrophilically with fluorine in unstable carbon-fluorine bonds in carbon fluoride, which helps to remove unstable carbon-fluorine bonds, thereby helping to improve the stability of the positive electrode material. Silane additives contain olefin groups, which can react with the surface of metallic lithium to form a stable passivation layer. At the same time, free radical polymerization or ion polymerization is carried out under the action of carbon cations or carbon free radicals to form a passivation layer on the active surface of the positive electrode, blocking direct contact between the electrolyte and carbon fluoride, thereby helping to inhibit the decomposition of the electrolyte, and then helping to improve the high-temperature storage stability of the battery. The introduction of fluoroalkanes helps to improve the wettability of carbon fluoride electrodes, which is beneficial to maintaining the stability of the internal resistance of the battery. At the same time, fluoroalkanes can form a passivation layer containing lithium fluoride on the surface of metallic lithium, enhancing the stability of metallic lithium. Controlling the contents of anhydride additives, silane additives and fluoroalkanes within the above ranges helps to fully exert the synergistic effect between the components, thereby helping to further improve the stability of carbon fluoride batteries under long-term and high-temperature storage conditions.

[0076] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electrolyte, characterized in that: In terms of mass percentage, the electrolyte comprises: 0.01-1% of anhydride additives, 0.1-5% of silane additives, 0.1-10% of fluoroalkane, and the remainder of organic solvent and lithium salt; wherein, The chemical formula of the silane additive is (R1) b Si a (R2) 2a+2-b , wherein a is 1 or 2, b is an integer from 1 to 6, 2a+2-b is an integer from 0 to 5, and R1 is selected from substituted or unsubstituted C2 to C 10 Any of the alkenyl groups, R2 is selected from substituted or unsubstituted C1 to C 10 Any of the alkyl groups.

2. The electrolyte according to claim 1, characterized in that b is an integer from 1 to 4; and / or 2a+2-b is an integer from 0 to 4; and / or R1 is selected from any one of substituted or unsubstituted C2 to C4 alkenyl; and / or R2 is selected from any one of substituted or unsubstituted C1 to C4 alkyl; Preferably, the R1 is selected from any one of vinyl, propenyl, allyl or butenyl; and / or, the R2 is selected from any one of methyl, ethyl, propyl or butyl; More preferably, the R1 is vinyl or allyl; and / or the R2 is any one of methyl, ethyl or propyl.

3. The electrolyte according to claim 2, characterized in that The silane additive is selected from any one or more of vinyltrimethylsilane, vinyltriethylsilane, divinyldimethylsilane, divinyldipropylsilane, trivinylmethylsilane, trivinylethylsilane, tetravinylsilane, tetraallylsilane and divinyltetramethyldisilane; Preferably, the silane additive is a combination of tetravinylsilane and divinyldimethylsilane, and the mass ratio of the tetravinylsilane to the divinyldimethylsilane is 1:0.1-5.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The fluoroalkane is selected from C4 to C 10 Any one or more of fluoroalkanes; Preferably, the fluoroalkane is selected from any one or more of 1,1,3,3-pentafluorobutane, 2H,3H-decafluoropentane, 1H-perfluoropentane, perfluoro-n-pentane, perfluorohexane, 1H-perfluorohexane, 1,1-difluoroheptane, 1,7-difluoroheptane and perfluorooctane; More preferably, the fluoroalkane is a combination of 2H,3H-decafluoropentane and 1H-perfluorohexane, and the mass ratio of the 2H,3H-decafluoropentane to the 1H-perfluorohexane is 1:0.1-0.

5.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The mass ratio of the acid anhydride additive, the silane additive and the fluoroalkane is 0.5-1:1-1.5:

1.

6. The electrolyte according to any one of claims 1 to 5, characterized in that The concentration of the lithium salt in the electrolyte is 0.5 to 2 mol / L.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The acid anhydride additive is selected from any one or more of phenyl maleic anhydride, maleic anhydride, phthalic anhydride, 2,3-pyridinedicarboxylic anhydride, succinic anhydride, biphenyl anhydride, adipic anhydride, glutaric anhydride, glutaric anhydride, benzoic anhydride, citraconic anhydride, phenoxyacetic anhydride, phenylsuccinic anhydride and NA-anhydride; preferably, the acid anhydride additive is phthalic anhydride.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The lithium salt is selected from any one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium trifluoromethanesulfonate, lithium bis(oxalatoborate) and lithium bis(fluorooxalatoborate); preferably, the lithium salt is lithium tetrafluoroborate.

9. The electrolyte according to any one of claims 1 to 8, characterized in that The organic solvent is selected from any one or more of ethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and gamma-martinol. Preferably, the organic solvent is a combination of propylene carbonate and ethylene glycol dimethyl ether, and the mass ratio of the propylene carbonate to the ethylene glycol dimethyl ether is 1:0.2-5.

10. A carbon fluoride battery, comprising a carbon fluoride positive electrode sheet, an electrolyte and a negative electrode sheet, characterized in that: The electrolyte is the electrolytic solution according to any one of claims 1 to 9.

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