In-situ gel polymer electrolyte and preparation method and application thereof

Abstract

The present invention relates to the technical field of lithium ion battery manufacturing, and in particular to an in-situ gel polymer electrolyte and its preparation method and application. It includes: dissolving lithium salt in a mixed organic solvent of 1,3-dioxolane and carbonate organic matter, stirring and mixing evenly under the conditions of room temperature, inert gas protection and a rotation speed of 100 to 1000 rpm; dissolving additives in an electrolyte, stirring under the conditions of room temperature, inert gas protection and a rotation speed of 100 to 1000 rpm; adding an initiator, stirring under the conditions of room temperature, inert gas protection and a rotation speed of 100 to 1000 rpm to obtain an in-situ gel polymer electrolyte. The advantages are: the initiator triggers the in-situ polymerization of 1,3-dioxolane, forms a gel polymer electrolyte in situ in the battery, improves the compatibility of the interface, and reduces the battery impedance; forms a stable interface film, improves the stability of the electrode interface, and improves the room temperature rate performance and low temperature performance of the battery.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery manufacturing, and in particular to an in-situ gel polymer electrolyte and a preparation method and application thereof. Background Art

[0002] With the popularity of electric vehicles, lithium-ion and sodium-ion batteries are increasingly used. Compared with traditional liquid electrolytes, solid electrolytes have higher modulus and better safety. However, solid electrolytes have lower conductivity and poor interfacial compatibility. Gel electrolytes have both the high conductivity of liquid electrolytes and the high modulus and good safety of solid electrolytes, so they have received widespread attention.

[0003] At present, the common lithium salt for the preparation of gel electrolyte is lithium bis(trifluoromethylsulfonyl)imide, and Lewis acid is used to catalyze cyclic ether solvents, such as 1,3-dioxolane (DOL), to make it undergo ring-opening polymerization to prepare gel electrolyte. In the Chinese invention patent application with publication number CN109786675A, publication date May 21, 2019, and invention name "A method for interface modification of metal lithium negative electrode of solid-state lithium battery", lithium hexafluoroarsenate (LiAsF6) is used as a catalyst to initiate polymerization to form a gel polymer electrolyte. In the Chinese invention patent application with publication number CN110635165A, publication date May 21, 2019, and invention name "Method for preparing gel polymer electrolyte and gel battery by in-situ ring-opening polymerization", lithium difluorooxalate borate is used as an initiator to successfully induce 1,3-dioxolane (DOL) to undergo ring-opening polymerization to form a gel polymer electrolyte. However, the above schemes have the following problems: CN109786675A uses lithium salt lithium hexafluoroarsenate (LiAsF6), which is highly toxic and not conducive to safe production; CN110635165A requires additional high temperature, which will cause certain safety risks for lithium-ion batteries.

[0004] Therefore, finding a suitable initiator to initiate the ring-opening polymerization of 1,3-dioxolane (DOL) at room temperature to construct an in-situ polymerized gel electrolyte with high safety and stability is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0005] In order to solve the above problems, the present invention provides an in-situ gel polymer electrolyte and a preparation method and application thereof.

[0006] The first object of the present invention is to provide a method for preparing an in-situ gel polymer electrolyte, which specifically comprises the following steps:

[0007] S1. Preparation of electrolyte: dissolve lithium salt in a mixed organic solvent of 1,3-dioxolane (DOL) and carbonate organic matter, stir at high speed for 10 min to 24 h at room temperature, inert gas protection and a speed of 100 to 1000 rpm to mix evenly;

[0008] S2. The additive is dissolved in the electrolyte prepared in step S1, and stirred at high speed for 10 min to 24 h at room temperature, under inert gas protection and at a speed of 100 to 1000 rpm;

[0009] S3. Add initiator and stir at high speed for 10 min to 1 h at room temperature, inert gas protection and a rotation speed of 100 to 1000 rpm to prepare an in-situ gel polymer electrolyte.

[0010] Preferably, the volume ratio of 1,3-dioxolane (DOL) to the carbonate organic matter is 1-6:1-2; the carbonate organic matter includes at least one of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and fluoroethylene carbonate.

[0011] Preferably, the lithium salt is at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, and lithium tetrafluoroborate, and the total concentration of the lithium salt in the electrolyte is 0.5 to 3M.

[0012] Preferably, the initiator is fluoroanhydride with a concentration of 0.1-20 mM.

[0013] Preferably, the initiator is hexafluoroglutaric anhydride.

[0014] Preferably, the additive includes at least one of trimethylsilyl borate, trimethylsilyl phosphate, vinylene carbonate, 1,3-propane sultone, and citraconic anhydride; the mass of the additive accounts for 0.1-5% of the total mass of the electrolyte.

[0015] Preferably, the inert gas is argon; and the room temperature is 15-30°C.

[0016] The second object of the present invention is to provide an in-situ gel polymer electrolyte prepared by the in-situ gel polymer electrolyte preparation method.

[0017] The third object of the present invention is to provide an application of an in-situ gel polymer electrolyte in the preparation of a lithium ion battery.

[0018] Preferably, the in-situ gel polymer electrolyte is injected into a lithium-ion battery and allowed to stand at room temperature for 12 to 24 hours to obtain the obtained product;

[0019] The positive electrode in the lithium-ion battery is at least one of nickel-cobalt-manganese, nickel-cobalt-aluminum, lithium cobaltate, lithium nickel-manganese oxide, lithium-rich manganese-based solid solution, lithium manganese oxide, and lithium iron phosphate; the negative electrode is at least one of artificial graphite, natural graphite, mesophase carbon microbeads, silicon-based negative electrode, and tin-based negative electrode.

[0020] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0021] (1) Using an initiator to initiate in-situ polymerization of 1,3-dioxolane (DOL) to form a gel polymer electrolyte in-situ in the battery, thereby improving the compatibility of the interface and reducing the battery impedance;

[0022] (2) The plasticizing effect of carbonate organic matter in the mixed organic solvent can reduce the crystallinity of the polymer after the ring-opening polymerization of 1,3-dioxolane (DOL) and improve the ionic conductivity of the electrolyte;

[0023] (3) The in-situ polymerization strategy can avoid the solvent volatilization step in the process production, reduce the production cost and complexity, and is suitable for large-scale production;

[0024] (4) The use of different additives and hexafluoroglutaric anhydride can form a stable interfacial film and improve the stability of the electrode interface;

[0025] (5) Hexafluoroglutaric anhydride can improve the high temperature stability and flame retardant properties of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a flow chart of a method for preparing an in-situ gel polymer electrolyte according to an embodiment of the present invention.

[0027] Figure 2 This is a physical picture of an in-situ gel polymer electrolyte provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0030] The present invention provides a method for preparing an in-situ gel polymer electrolyte, which specifically comprises the following steps:

[0031] S1. Preparation of electrolyte: dissolve lithium salt in a mixed organic solvent of 1,3-dioxolane (DOL) and carbonate organic matter, stir at high speed for 10 min to 24 h at room temperature, argon atmosphere protection and a speed of 100 to 1000 rpm, so that the lithium salt is completely dissolved in the mixed organic solvent;

[0032] S2. The additive is dissolved in the electrolyte prepared in step S1, and stirred at high speed for 10 min to 24 h at room temperature, argon atmosphere protection and a speed of 100 to 1000 rpm;

[0033] S3. Add initiator, stir at high speed for 10 min to 1 h at room temperature, argon atmosphere protection and rotation speed of 100 to 1000 rpm to prepare in-situ gel polymer electrolyte. Figure 1 shown.

[0034] Specifically, the lithium salt is at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, and lithium tetrafluoroborate, and the total concentration of the lithium salt in the electrolyte is 0.5-3M.

[0035] Specifically, the carbonate organic matter includes at least one of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and fluoroethylene carbonate, and the volume ratio of 1,3-dioxolane (DOL) to the carbonate organic matter is 1-6:1-2.

[0036] Specifically, the additive includes at least one of trimethylsilyl borate, trimethylsilyl phosphate, vinylene carbonate, 1,3-propane sultone, and citraconic anhydride; the mass of the additive accounts for 0.1 to 5% of the total mass of the electrolyte.

[0037] Specifically, the initiator is hexafluoroglutaric anhydride, and the concentration is 0.1-20 mM. Similar fluorinated anhydrides can achieve 1,3-dioxolane (DOL) catalytic polymerization to prepare electrolytes.

[0038] A method for preparing a high energy density lithium ion battery is also provided, comprising: injecting the prepared in-situ gel polymer electrolyte into the lithium ion battery, and leaving it to stand at room temperature for 12 to 24 hours to obtain the high energy density lithium ion battery.

[0039] The positive electrode in the high energy density lithium-ion battery is at least one of nickel cobalt manganese, nickel cobalt aluminum, lithium cobalt oxide, lithium nickel manganese oxide, lithium-rich manganese-based solid solution, lithium manganese oxide, and lithium iron phosphate; the negative electrode is at least one of artificial graphite, natural graphite, mesophase carbon microbeads, silicon-based negative electrode, and tin-based negative electrode.

[0040] Example 1

[0041] This embodiment provides a method for preparing an in-situ gel polymer electrolyte, which specifically comprises the following steps:

[0042] S1. Preparation of electrolyte: dissolve lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide) in a mixed organic solvent of 1,3-dioxolane (DOL) and carbonate organic matter, and stir at high speed for 5 hours at room temperature, under argon atmosphere protection and at a speed of 800 rpm, so that the lithium salt is completely dissolved in the mixed organic solvent; the volume ratio of 1,3-dioxolane (DOL) and carbonate organic matter is 6:1; the carbonate organic matter is ethylene carbonate; the total concentration of lithium bis(trifluoromethanesulfonyl imide and lithium bis(fluorosulfonyl imide) is 2M;

[0043] S2. The additive trimethylsilyl borate is dissolved in the electrolyte prepared in step S1, and stirred at high speed for 12 hours at room temperature, argon atmosphere protection and a speed of 500 rpm; the mass of trimethylsilyl borate accounts for 1% of the total mass of the electrolyte;

[0044] S3. Hexafluoroglutaric anhydride with a concentration of 10 mM was added, and the mixture was stirred at high speed for 1 h at room temperature, argon atmosphere protection and a rotation speed of 100 rpm to prepare an in-situ gel polymer electrolyte.

[0045] Application examples:

[0046] The prepared in-situ gel polymer electrolyte was injected into a lithium-ion battery and left to stand at room temperature for 24 hours to obtain a high energy density lithium-ion battery; wherein the positive electrode was nickel-cobalt-manganese; and the negative electrode was natural graphite. The prepared battery was subjected to charge and discharge cycle tests at room temperature and 0.1C. The test results showed that the initial capacity was 0.5Ah; the 10C / 10C capacity retention rate was 75.11% at room temperature (about 25°C); the 0.5C / 0.5C capacity retention rate was 86.21% at low temperature (about -20°C); it showed excellent charge and discharge performance and a long cycle life.

[0047] Example 2

[0048] This embodiment provides a method for preparing an in-situ gel polymer electrolyte, which specifically comprises the following steps:

[0049] S1. Preparation of electrolyte: dissolve lithium hexafluorophosphate and lithium nitrate in a mixed organic solvent of 1,3-dioxolane (DOL) and carbonate organic matter, stir at high speed for 10 minutes at room temperature, argon atmosphere protection and a speed of 1000 rpm, so that the lithium salt is completely dissolved in the mixed organic solvent; the volume ratio of 1,3-dioxolane (DOL) and carbonate organic matter is 1:2; carbonate organic matter includes ethylene carbonate and methyl ethyl carbonate; the total concentration of lithium hexafluorophosphate and lithium nitrate is 3M;

[0050] S2. The additive trimethylsilyl borate is dissolved in the electrolyte prepared in step S1, and stirred at high speed for 12 hours at room temperature, argon atmosphere protection and a speed of 500 rpm; the mass of trimethylsilyl borate accounts for 0.5% of the total mass of the electrolyte;

[0051] S3. Hexafluoroglutaric anhydride with a concentration of 0.5 mM was added, and the mixture was stirred at high speed for 1 h at room temperature, argon atmosphere protection and a rotation speed of 100 rpm to prepare an in-situ gel polymer electrolyte.

[0052] Application examples:

[0053] The prepared in-situ gel polymer electrolyte was injected into a lithium-ion battery and left to stand at room temperature for 24 hours to obtain a high energy density lithium-ion battery; wherein the positive electrode was nickel-cobalt-manganese; and the negative electrode was natural graphite. The prepared battery was subjected to charge and discharge cycle tests at room temperature and 0.1C. The test results showed that the initial capacity was 0.49Ah; the 10C / 10C capacity retention rate was 60.73% at room temperature (about 25°C); the 0.5C / 0.5C capacity retention rate was 75.68% at low temperature (about -20°C); it showed excellent charge and discharge performance and a long cycle life.

[0054] Example 3

[0055] This embodiment provides a method for preparing an in-situ gel polymer electrolyte, which specifically comprises the following steps:

[0056] S1. Preparation of electrolyte: dissolve lithium bis(trifluoromethanesulfonyl imide) and lithium tetrafluoroborate in a mixed organic solvent of 1,3-dioxolane (DOL) and carbonate organic matter, and stir at high speed for 24 hours at room temperature, under argon atmosphere protection and at a speed of 100 rpm, so that the lithium salt is completely dissolved in the mixed organic solvent; the volume ratio of 1,3-dioxolane (DOL) and carbonate organic matter is 1:1; the carbonate organic matter is a mixture of ethyl methyl carbonate, dimethyl carbonate and fluoroethylene carbonate; the total concentration of lithium bis(trifluoromethanesulfonyl imide and lithium tetrafluoroborate is 1M;

[0057] S2. The additive trimethylsilyl phosphate is dissolved in the electrolyte prepared in step S1, and stirred at high speed for 12 h at room temperature, argon atmosphere protection and a speed of 500 rpm; the mass of trimethylsilyl phosphate accounts for 2% of the total mass of the electrolyte;

[0058] S3. Add hexafluoroglutaric anhydride at a concentration of 20 mM, and stir at high speed for 30 minutes at room temperature, under argon atmosphere protection and a rotation speed of 500 rpm to prepare an in-situ gel polymer electrolyte.

[0059] Application examples:

[0060] The prepared in-situ gel polymer electrolyte was injected into a lithium-ion battery and left to stand at room temperature for 12 hours to obtain a high energy density lithium-ion battery; wherein the positive electrode was lithium cobalt oxide; and the negative electrode was mesophase carbon microspheres. The prepared battery was subjected to charge and discharge cycle tests at room temperature and 0.1C. The test results showed that the initial capacity was 0.495Ah; the 10C / 10C capacity retention rate was 63.11% at room temperature (about 25°C); the 0.5C / 0.5C capacity retention rate was 80.43% at low temperature (about -20°C); it showed excellent charge and discharge performance and a long cycle life.

[0061] Example 4

[0062] This embodiment provides a method for preparing an in-situ gel polymer electrolyte, which specifically comprises the following steps:

[0063] S1. Preparation of electrolyte: dissolve lithium bis(trifluoromethanesulfonyl imide) and lithium nitrate in a mixed organic solvent of 1,3-dioxolane (DOL) and carbonate organic matter, and stir at high speed for 30 minutes at room temperature, under argon atmosphere protection and a rotation speed of 1000 rpm, so that the lithium salt is completely dissolved in the mixed organic solvent; the volume ratio of 1,3-dioxolane (DOL) and carbonate organic matter is 2:1; the carbonate organic matter is fluoroethylene carbonate; the total concentration of lithium bis(trifluoromethanesulfonyl imide and lithium nitrate is 1M;

[0064] S2. The additive is dissolved in the electrolyte prepared in step S1, and stirred at high speed for 12 hours at room temperature, argon atmosphere protection and a speed of 500 rpm; the additive is a mixture of trimethylsilyl borate and citraconic anhydride; the mass of the additive accounts for 5% of the total mass of the electrolyte;

[0065] S3. Add hexafluoroglutaric anhydride at a concentration of 20 mM, and stir at high speed for 30 minutes at room temperature, under argon atmosphere protection and a rotation speed of 500 rpm to prepare an in-situ gel polymer electrolyte.

[0066] Application examples:

[0067] The prepared in-situ gel polymer electrolyte was injected into a lithium-ion battery and left to stand at room temperature for 24 hours to obtain a high energy density lithium-ion battery; wherein the positive electrode was lithium nickel manganese oxide; and the negative electrode was natural graphite. The prepared battery was subjected to charge and discharge cycle tests at room temperature and 0.1C. The test results showed that the initial capacity was 0.5Ah; the 10C / 10C capacity retention rate was 68.19% at room temperature (about 25°C); and the 0.5C / 0.5C capacity retention rate was 83.87% at low temperature (about -20°C); it showed excellent charge and discharge performance and a long cycle life.

[0068] Example 5

[0069] This embodiment provides a method for preparing an in-situ gel polymer electrolyte, which specifically comprises the following steps:

[0070] S1. Preparation of electrolyte: dissolve lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate in a mixed organic solvent of 1,3-dioxolane (DOL) and carbonate organic matter, and stir at high speed for 18 hours at room temperature, under argon atmosphere protection and at a speed of 500 rpm, so that the lithium salt is completely dissolved in the mixed organic solvent; the volume ratio of 1,3-dioxolane (DOL) and carbonate organic matter is 3:1; carbonate organic matter includes ethylene carbonate and dimethyl carbonate; the total concentration of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate is 2M;

[0071] S2. The additive trimethylsilyl borate is dissolved in the electrolyte prepared in step S1, and stirred at high speed for 12 hours at room temperature, argon atmosphere protection and a speed of 500 rpm; the mass of trimethylsilyl borate accounts for 1% of the total mass of the electrolyte;

[0072] S3. Hexafluoroglutaric anhydride with a concentration of 10 mM was added, and the mixture was stirred at high speed for 1 h at room temperature, argon atmosphere protection and a rotation speed of 100 rpm to prepare an in-situ gel polymer electrolyte.

[0073] Application examples:

[0074] The prepared in-situ gel polymer electrolyte was injected into a lithium-ion battery and left to stand at room temperature for 24 hours to obtain a high energy density lithium-ion battery; wherein the positive electrode is nickel-cobalt-manganese; and the negative electrode is a silicon-based negative electrode. The prepared battery was subjected to charge and discharge cycle tests at room temperature and 0.1C. The test results showed that the initial capacity was 0.5Ah; the 10C / 10C capacity retention rate was 72.74% at room temperature (about 25°C); the 0.5C / 0.5C capacity retention rate was 85.43% at low temperature (about -20°C); it showed excellent charge and discharge performance and a long cycle life.

[0075] Figure 2 This is a real picture of the in-situ gel polymer electrolyte prepared by the present invention after being left to stand at room temperature for more than 12 hours. The upper transparent part in the picture is the in-situ gel polymer electrolyte.

[0076] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0077] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an in-situ gel polymer electrolyte, characterized in that: The specific steps include: S1. Preparation of electrolyte: dissolving lithium salt in a mixed organic solvent of 1,3-dioxolane and carbonate organic matter, stirring at high speed for 10min~24h at room temperature, inert gas protection and a speed of 100~1000 rpm, and mixing evenly; the volume ratio of 1,3-dioxolane to the carbonate organic matter is 2~6:1; the carbonate organic matter includes at least one of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and fluoroethylene carbonate; the total concentration of the lithium salt in the electrolyte is 1~3M; S2. Dissolve the additive in the electrolyte prepared in step S1, and stir at high speed for 10 min to 24 h at room temperature, inert gas protection and a speed of 100 to 1000 rpm; the additive includes at least one of trimethylsilyl borate, trimethylsilyl phosphate, vinylene carbonate, 1,3-propane sultone, and citraconic anhydride; the mass of the additive accounts for 0.1 to 5% of the total mass of the electrolyte; S3. Add an initiator, stir at high speed for 10 min to 1 h at room temperature, under inert gas protection and at a speed of 100 to 1000 rpm to obtain an in-situ gel polymer electrolyte precursor; then inject the in-situ gel polymer electrolyte precursor into the lithium ion battery, and let it stand at room temperature for 12 to 24 h to obtain an in-situ gel polymer electrolyte; the initiator is hexafluoroglutaric anhydride, and the concentration is 0.1 to 20 mM.

2. The method for preparing an in-situ gel polymer electrolyte according to claim 1, characterized in that: The lithium salt is at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, and lithium tetrafluoroborate.

3. The method for preparing an in-situ gel polymer electrolyte according to any one of claims 1 to 2, characterized in that: The inert gas is argon; the room temperature is 15-30°C.

4. An in-situ gel polymer electrolyte, characterized in that: The in-situ gel polymer electrolyte is prepared by the preparation method of any one of claims 1 to 3.

5. Use of the in-situ gel polymer electrolyte according to claim 4 in the preparation of lithium ion batteries.

6. The use of an in-situ gel polymer electrolyte in the preparation of a lithium ion battery according to claim 5, characterized in that: The in-situ gel polymer electrolyte precursor is injected into the interior of the lithium ion battery and allowed to stand at room temperature for 12 to 24 hours to obtain a product; The positive electrode in the lithium-ion battery is at least one of nickel-cobalt-manganese, nickel-cobalt-aluminum, lithium cobaltate, lithium nickel-manganese oxide, lithium-rich manganese-based solid solution, lithium manganese oxide, and lithium iron phosphate; the negative electrode is at least one of artificial graphite, natural graphite, mesophase carbon microbeads, silicon-based negative electrode, and tin-based negative electrode.

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