In-situ polymerization solid-state electrolyte precursor liquid and solid-state battery

Abstract

The application discloses an in-situ polymerization solid electrolyte precursor liquid and a solid-state battery, and relates to the technical field of lithium ion batteries. Raw materials for preparing the precursor liquid include monomers, diluents, cross-linking agents, lithium salts, solvents and initiators. The mass ratio of the monomers, the diluents, the cross-linking agents, the lithium salts and the solvents is 2:3. The monomers include small organic molecules containing fluorine and unsaturated functional groups. The diluents are fluorine-substituted ether organic substances. The viscosity of the precursor liquid is less than or equal to 10 mPa.s. By using small organic molecules containing fluorine and unsaturated functional groups as monomers due to small intermolecular interaction force, and adding fluorine-substituted ether organic substances as diluents due to weak coordination with lithium salts, and by matching appropriate cross-linking agents, lithium salts and solvents, a solid electrolyte precursor liquid with low viscosity and local high concentration of lithium ions can be obtained, the solid electrolyte precursor liquid has good wettability, the wettability time can be shortened, the lithium ion migration kinetic potential barrier can be reduced, and the ionic conductivity can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to an in-situ polymerization solid electrolyte precursor solution and a solid-state battery. BACKGROUND

[0002] Secondary batteries are one of the important ways of energy storage at present, and are widely used in automobiles, electronic products and the like, mainly including lead-acid batteries, nickel-cadmium batteries, zinc-manganese batteries, lithium ion batteries and the like. Among them, lithium ion batteries become the first choice of high value-added product batteries due to their high energy density, long cycle life, no memory effect and many other advantages, and lithium metal is considered to be one of the most promising negative electrode materials for lithium batteries due to its low density (0.59 g·cm 3 ), high theoretical specific capacity (3860 mAh·g -1 ) and extremely low negative oxidation-reduction potential (-3.040 V vs. SHE). However, lithium metal batteries are limited by lithium dendrite growth effect, therefore, the prior art usually adopts a solid-state electrolyte with a certain mechanical strength or a high-concentration electrolyte solution to inhibit lithium dendrite growth and avoid the battery out of control caused by lithium dendrite piercing the separator.

[0003] The existing solid-state electrolyte usually adopts an in-situ polymerization process, but during the preparation process, the solid-state electrolyte precursor solution dissolved with monomers, cross-linking agents and high-concentration lithium salts usually has a large viscosity, and it is difficult to quickly infiltrate the electrode after the battery is assembled, which leads to large interface impedance of the solidified lithium metal and the positive electrode, poor interface contact, makes it difficult for the positive electrode capacity to be fully released, and causes rapid capacity decay and low coulombic efficiency of the battery. Therefore, how to obtain an in-situ polymerization solid-state electrolyte precursor solution with low viscosity and local high concentration is the key to improving the electrochemical performance of the solid-state battery.

[0004] It can be seen that the prior art still needs to be improved and enhanced. SUMMARY

[0005] In view of the above shortcomings of the prior art, the purpose of the present application is to provide an in-situ polymerization solid electrolyte precursor solution and a solid-state battery, which aims to solve the problems of poor interface contact, lithium metal surface dendrite growth and rapid capacity decay of the solid-state battery generated by the in-situ polymerization in the prior art.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] An in-situ polymerization solid electrolyte precursor solution, wherein the raw materials for preparing the precursor solution include: monomers, diluents, cross-linking agents, lithium salts, solvents and initiators; the mass ratio of the monomers, diluents, cross-linking agents, lithium salts and solvents is 2:3; the monomers include organic small molecules containing fluorine and unsaturated functional groups; the diluents are fluorine-substituted ether organic substances; and the viscosity of the precursor solution is ≤10 mPa·s.

[0008] The in-situ polymerization solid electrolyte precursor liquid, the small molecule organic containing fluorine and unsaturated functional groups includes at least one of 2,2,2-trifluoroethyl methacrylate, 2,2,2-trifluoroethyl acrylate, 1,1-bis(trifluoromethyl)-2,2,3,3,3,3-pentafluoropropyl 2-fluoroacrylate, methyl methacrylate-2,2,3,3,4,4,4-heptafluorobutyl, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, fluoroalkyl acrylate, perfluoroalkyl ethyl acrylate, hexafluorobutyl methacrylate, hexafluoroisopropyl methacrylate.

[0009] The in-situ polymerization solid electrolyte precursor liquid, the monomer further includes vinylene carbonate.

[0010] The in-situ polymerization solid electrolyte precursor liquid, the diluent is selected from at least one of 2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, perfluoro nonenyl trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether.

[0011] The in-situ polymerization solid electrolyte precursor liquid, the lithium salt is selected from at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate.

[0012] The in-situ polymerization solid electrolyte precursor liquid, the crosslinking agent is pentaerythritol tetraacrylate or ethylene glycol dimethacrylate.

[0013] The in-situ polymerization solid electrolyte precursor liquid, the mass ratio of the monomer to the diluent is (1:2) to (2:1).

[0014] A solid-state battery includes a positive electrode, a separator, a negative electrode, and a solid-state electrolyte, wherein the solid-state electrolyte is obtained by in-situ polymerization of the in-situ polymerization solid electrolyte precursor liquid as described above.

[0015] The in-situ polymerization solid-state battery, the temperature of the in-situ polymerization is 70-90℃.

[0016] The in-situ polymerization solid-state battery, the separator includes one of a polyimide film, a glass cellulose film, a polyvinylidene fluoride film, and an unsaturated olefin polymer film.

[0017] Beneficial effects:

[0018] The application provides a solid-state electrolyte precursor liquid and a solid-state battery, which are prepared by using a small organic molecule containing fluorine and an unsaturated functional group as a monomer due to small intermolecular interaction force, adding a fluorine-substituted ether organic molecule as a diluent due to weak coordination with lithium salt, matching a suitable crosslinking agent, lithium salt and solvent, so as to obtain a solid-state electrolyte precursor liquid with low viscosity and local high concentration effect of lithium ion concentration, the precursor liquid has good wettability, can effectively improve the wettability of the precursor liquid and the electrode material, shorten the wettability time, reduce the lithium ion migration kinetic potential barrier to improve the ionic conductivity; after the electrode material is fully wetted, the lithium ion concentration in the solid-state electrolyte generated by in-situ polymerization shows a local high concentration effect, which can increase the growth energy barrier of lithium dendrite and inhibit the growth of lithium dendrite, thereby effectively improving the rate performance and cycle stability, and solving a series of technical difficulties encountered by the current in-situ polymerization solid-state battery. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The AC impedance spectrum curve of the solid-state battery prepared from the solid-state electrolyte precursor liquid of Example 1 and the solid-state battery prepared from the solid-state electrolyte precursor liquid of Comparative Example 2.

[0020] Figure 2 The linear voltammetry scan curve of the solid-state battery prepared from the solid-state electrolyte precursor liquid of Example 1 and the solid-state battery prepared from the solid-state electrolyte precursor liquid of Comparative Example 2.

[0021] Figure 3 The AC impedance spectrum curve of the solid-state battery prepared from the solid-state electrolyte precursor liquid of Example 1 and the solid-state battery prepared from the solid-state electrolyte precursor liquid of Comparative Example 2.

[0022] Figure 4 The rate performance and coulombic efficiency test results of the solid-state battery prepared from the solid-state electrolyte precursor liquid of Example 1 and the solid-state battery prepared from the solid-state electrolyte precursor liquid of Comparative Example 2. DETAILED DESCRIPTION

[0023] The application provides a solid-state electrolyte precursor liquid and a solid-state battery, which are prepared by using a small organic molecule containing fluorine and an unsaturated functional group as a monomer due to small intermolecular interaction force, adding a fluorine-substituted ether organic molecule as a diluent due to weak coordination with lithium salt, matching a suitable crosslinking agent, lithium salt and solvent, so as to obtain a solid-state electrolyte precursor liquid with low viscosity and local high concentration effect of lithium ion concentration, the precursor liquid has good wettability, can effectively improve the wettability of the precursor liquid and the electrode material, shorten the wettability time, reduce the lithium ion migration kinetic potential barrier to improve the ionic conductivity; after the electrode material is fully wetted, the lithium ion concentration in the solid-state electrolyte generated by in-situ polymerization shows a local high concentration effect, which can increase the growth energy barrier of lithium dendrite and inhibit the growth of lithium dendrite, thereby effectively improving the rate performance and cycle stability, and solving a series of technical difficulties encountered by the current in-situ polymerization solid-state battery.

[0024] In view of the problems of poor interface contact, dendrite growth on the surface of lithium metal, rapid capacity decay and the like of the solid-state battery generated by in-situ polymerization in the prior art, the present application provides a solid-state electrolyte precursor solution prepared by in-situ polymerization, and the raw materials for preparing the precursor solution include: monomer, diluent, crosslinking agent, lithium salt, initiator and solvent, wherein the mass ratio of the monomer, diluent, crosslinking agent, lithium salt and solvent is 2:3; the monomer includes organic small molecules containing fluorine and unsaturated functional groups, and such organic small molecules have relatively small intermolecular interaction force, which can reduce the viscosity of the precursor solution, and further improve the wettability of the precursor solution to the electrode material and the separator; the diluent is fluorine-substituted ether organic matter, and the coordination effect of the fluorine-substituted ether organic matter with the lithium salt is weak, which can reduce the viscosity of the precursor solution while forming a local high concentration effect of lithium ions. Therefore, by using the monomer and diluent with special functional groups, a solid-state electrolyte precursor solution with low viscosity and local high concentration of lithium ions can be obtained, the viscosity of the precursor solution is ≤10 mPa·s, the electrode material and the separator can be better infiltrated, the infiltration time is shortened, the lithium ion migration kinetic potential barrier is reduced to improve the ionic conductivity, and when the average concentration of lithium ions in the precursor solution is only 0.5 mol / L-1.5 mol / L, a local high concentration effect of lithium ions with a local concentration ≥3 mol / L can be formed, which can increase the lithium dendrite growth energy barrier and inhibit the growth of lithium dendrites, thereby effectively improving the rate performance and cycle stability, and solving a series of technical difficulties encountered by the in-situ polymerization solid-state battery.

[0025] Since the organic small molecules containing fluorine and unsaturated functional groups have relatively low intermolecular interaction force, they can reduce the viscosity of the solution and facilitate the rapid infiltration of the precursor solution into the electrode material. As a preferred embodiment, the monomer is selected from at least one of 2,2,2-trifluoroethyl methacrylate, 2,2,2-trifluoroethyl acrylate, 1,1-bis(trifluoromethyl)-2,2,3,3,3,3-pentafluoropropyl 2-fluoroacrylate, methyl methacrylate-2,2,3,3,4,4,4-heptafluorobutyl, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, fluoroalkyl acrylate, perfluoroalkyl ethyl acrylate, hexafluorobutyl methacrylate, hexafluoroisopropyl methacrylate (HFIP-M), but is not limited to the above-mentioned organic matter containing fluorine and unsaturated functional groups, and can also be other organic matter containing fluorine and unsaturated functional groups. Since the aforementioned monomers are all fluorine-containing and acrylate esters, the acrylate contained in the molecules can provide unsaturated bonds, which facilitates the in-situ polymerization of the precursor solution to form a solid-state electrolyte; the fluorine contained therein can be used as a component for constructing the SEI of the battery; and the ester group contained therein has an enhancing effect on the electrochemical stability of the battery.

[0026] In a more preferable embodiment, the monomer further comprises vinylene carbonate, which cooperates with the small organic molecules containing fluorine and unsaturated functional groups to further improve the stability and conductivity of the battery.

[0027] Although high concentration of lithium ion electrolyte is beneficial to inhibit the growth of lithium dendrites, high concentration of lithium ion will result in high viscosity of the precursor solution, and high viscosity of the precursor solution is difficult to infiltrate the separator and the positive material, resulting in poor interface contact, and further poor electrochemical performance. The addition and selection of the diluent is a key factor to reduce the viscosity of the precursor solution, improve the ionic conductivity of the solid-state battery and form local high concentration of lithium ion. In view of this, in a preferable embodiment, the diluent is selected from at least one of 2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, perfluoro nonenyl trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether. Since the coordination of the aforementioned diluent with lithium ion is weak, it can greatly reduce the viscosity of the precursor solution, but at the same time can promote the formation of local high concentration of lithium salt, which can increase the growth barrier of lithium dendrites and inhibit the growth of lithium dendrites, thereby effectively improving the rate performance and cycle stability.

[0028] In a preferable embodiment, the lithium salt is selected from at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate, which has weak coordination with the aforementioned diluent, but has good dispersibility and stability in the aforementioned monomer and diluent. The solvent is a mixed solvent of 1,3-dioxolane and ethylene glycol dimethyl ether, preferably a mixed solvent of 1,3-dioxolane and ethylene glycol dimethyl ether in a mass ratio of 1:1, which has good solubility for the aforementioned lithium salt.

[0029] In a preferable embodiment, the cross-linking agent is selected from pentaerythritol tetraacrylate or ethylene glycol dimethyl acrylate, or other acrylate or methacrylate substances. The aforementioned cross-linking agent has high activity at 70-90°C, facilitating in-situ polymerization at this temperature, and is relatively stable at room temperature. In addition, the use of acrylate substances as cross-linking agents can also improve the mechanical strength and mechanical stability of the solid-state electrolyte after in-situ polymerization, inhibit the growth of lithium dendrites, and effectively improve the rate performance and cycle stability.

[0030] In a preferred embodiment, the initiator is selected from one of azo compounds or porphyrin active compounds, such as azobisisobutyronitrile (AIBN) or amino tetraphenyl porphyrin (TAPP), which can initiate monomer polymerization under the condition of very small amount of addition, so as to form the solid electrolyte in situ by polymerization of the precursor solution. It should be noted that the amount of initiator added is usually about 1% of the mass of the monomer.

[0031] In actual application, the in-situ polymerization solid electrolyte precursor solution is prepared by the following method: taking lithium salt and solvent, stirring and mixing to obtain solution A with lithium ion concentration of 3-5 mol / L; taking monomer, diluent and crosslinking agent, stirring and mixing to obtain solution B; taking solution A and solution B in a mass ratio of 3:2, mixing, then adding initiator, stirring and mixing to obtain the in-situ polymerization solid electrolyte precursor solution.

[0032] In the preparation process, when stirring and mixing are required, a magnetic stirrer or other equipment with stirring and mixing functions can be used for stirring and mixing, and the magnetic stirrer is preferred, which facilitates sealing during stirring and mixing, so as to avoid exposure of the materials to air. In the preparation of solution A and solution B, the stirring time of the magnetic stirrer is determined according to the mixing condition of the materials, and the materials must be uniformly mixed, which usually requires 60-90 min. When solution A and solution B are mixed, the stirring time is shorter due to the further reduced viscosity, and the materials can be mixed uniformly in about 30 min.

[0033] In a preferred embodiment, the mass ratio of monomer to diluent in solution B is (1:2)-(2:1), so as to obtain a suitable viscosity.

[0034] In addition, if the monomer and the diluent contain moisture, it will affect the in-situ polymerization, therefore, in a preferred embodiment, the monomer and the diluent also need to be dehydrated before solution B is prepared. Specifically, molecular sieves can be added to the monomer and the diluent to remove trace amounts of water in the monomer and the diluent by molecular sieves.

[0035] It should be noted that if the dehydrated monomer and diluent, and the prepared solution A and solution B are not used immediately, they need to be sealed and refrigerated at 2-8°C to avoid direct exposure to air or high temperature environment.

[0036] The second aspect of the present application also provides a solid-state battery, which comprises a positive electrode, a separator, a negative electrode and a solid-state electrolyte, wherein the solid-state electrolyte is obtained by in-situ polymerization of the in-situ polymerized solid-state electrolyte precursor liquid as described above. In the preparation of the solid-state battery, the positive electrode, the separator and the negative electrode are assembled first, then the electrolyte precursor liquid is injected, and then the battery is compressed under a pressure of 100 kPa, and is left to stand at room temperature for 4-24 hours, and then is reacted at a constant temperature of 70-90°C for 30-90 minutes, so that the solid-state battery is obtained.

[0037] It should be noted that when the solid-state battery is prepared, the separator must be fully soaked with the precursor liquid, and the standing time is based on the full absorption of the precursor liquid by the separator.

[0038] Since the solid-state battery uses the aforementioned in-situ polymerized solid-state electrolyte precursor liquid as the precursor liquid, the precursor liquid has a low viscosity, so it can fully soak the separator in a short time, generally 4 hours. The monomer in the precursor liquid is a small organic molecule containing fluorine and an unsaturated functional group, which can be rapidly in-situ polymerized at 70-90°C, thus greatly shortening the preparation time of the battery.

[0039] In a preferred embodiment, the positive electrode uses one of lithium iron phosphate, high-voltage lithium cobalt oxide and nickel-cobalt-manganese ternary positive electrode as the positive electrode material active substance; the separator comprises one of a polyimide film, a glass cellulose film, a polyvinylidene fluoride film and an unsaturated olefin polymer film, and such a separator is prepared by an electrospinning process, has a high porosity, is easy to soak with the precursor liquid, and is chemically stable.

[0040] To further illustrate the in-situ polymerized solid-state electrolyte precursor liquid and the solid-state battery provided by the present application, the following examples are provided.

[0041] Example 1

[0042] An in-situ polymerized solid-state electrolyte precursor liquid, which is prepared by the following steps:

[0043] (1) 861 parts of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are dissolved in 968 parts of a solvent by mass fraction, and stirred until mixed uniformly to obtain solution A; wherein the solvent is composed of 1,3-dioxolane (DOL) and dimethoxyethane (DME) in a mass ratio of 1:1;

[0044] (2) 24 parts of completely water-free methyl 2,2,2-trifluoroethyl acrylate (TFEA), 24 parts of bis(2,2,2-trifluoroethyl) ether (BTFE) and 42 parts of pentaerythritol tetraacrylate (PETEA), 10 parts of vinylene carbonate (VC) are mixed and stirred uniformly to obtain solution B;

[0045] (3) Take 30 parts of solution A and 20 parts of solution B by mass fraction, stir and mix evenly, add 0.2 parts of azobisisobutyronitrile (AIBN), stir until mixed evenly, to obtain an in-situ polymerization solid electrolyte precursor solution.

[0046] Example 2

[0047] An in-situ polymerization solid electrolyte precursor solution is prepared by the following steps:

[0048] (1) Dissolve 861 parts of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 968 parts of solvent by mass fraction, stir until mixed evenly, to obtain solution A; wherein the solvent is the same as that of Example 1;

[0049] (2) Mix and stir 24 parts of completely water-free hexafluoroisopropyl methacrylate (HFIP-M), 24 parts of 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 42 parts of pentaerythritol tetraacrylate (PETEA), and 10 parts of vinylene carbonate (VC) evenly, to obtain solution B;

[0050] (3) Take 30 parts of solution A and 20 parts of solution B by mass fraction, stir and mix evenly, add 0.2 parts of azobisisobutyronitrile (AIBN), stir until mixed evenly, to obtain an in-situ polymerization solid electrolyte precursor solution.

[0051] Example 3

[0052] An in-situ polymerization solid electrolyte precursor solution is prepared by the following steps:

[0053] (1) Dissolve 456 parts of lithium hexafluorophosphate (LiPF6) in 968 parts of solvent by mass fraction, stir until mixed evenly, to obtain solution A; wherein the solvent is the same as that of Example 1; (2) Mix and stir 24 parts of completely water-free 2,2,2-trifluoroethyl acrylate (TFEA), 24 parts of bis 1,1,2-trifluoro-2-ethyl-2,2,2-trifluoro ether (HFE-347), 42 parts of pentaerythritol tetraacrylate (PETEA), and 10 parts of vinylene carbonate (VC) evenly, to obtain solution B;

[0054] (3) Take 30 parts of solution A and 20 parts of solution B by mass fraction, stir and mix evenly, add 0.2 parts of azobisisobutyronitrile (AIBN), stir and mix evenly, to obtain an in-situ polymerization solid electrolyte precursor solution.

[0055] Example 4

[0056] A in-situ polymerization solid electrolyte precursor solution is prepared by the following steps:

[0057] (1) 561 parts of lithium difluorosulfone imide are dissolved in 968 parts of a solvent, and stirred until mixed uniformly to obtain solution A; wherein the solvent is the same as the solvent in Example 1 in terms of composition;

[0058] (2) 16 parts of completely water-free 2,2,2-trifluoroethyl acrylate, 32 parts of 2,2,2-trifluoroethyl ether, 42 parts of ethylene glycol dimethacrylate (PEGDA), and 10 parts of vinylene carbonate (VC) are stirred and mixed uniformly to obtain solution B;

[0059] (3) 30 parts of solution A and 20 parts of solution B are taken, stirred and mixed uniformly, 0.2 parts of azobisisobutyronitrile (AIBN) is added, stirred and mixed uniformly to obtain an in-situ polymerization solid electrolyte precursor solution.

[0060] Example 5

[0061] A in-situ polymerization solid electrolyte precursor solution is prepared by the following steps:

[0062] (1) 279 parts of lithium tetrafluoroborate is dissolved in 968 parts of a solvent, and stirred until mixed uniformly to obtain solution A; wherein the solvent is the same as the solvent in Example 1 in terms of composition;

[0063] (2) 32 parts of completely water-free 1,1-bis(trifluoromethyl)-2,2,3,3,3,3-pentafluoropropyl 2-fluoroacrylate, 16 parts of bis 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 42 parts of ethylene glycol dimethacrylate (PEGDA), and 10 parts of vinylene carbonate (VC) are stirred and mixed uniformly to obtain solution B;

[0064] (3) 30 parts of solution A and 20 parts of solution B are taken, stirred and mixed uniformly, 0.2 parts of azobisisobutyronitrile (AIBN) is added, stirred and mixed uniformly to obtain an in-situ polymerization solid electrolyte precursor solution.

[0065] Example 6

[0066] A in-situ polymerization solid electrolyte precursor solution is prepared by the following steps:

[0067] (1) 431 parts of lithium difluoro oxalate borate is dissolved in 968 parts of a solvent, and stirred until mixed uniformly to obtain solution A; wherein the solvent is the same as the solvent in Example 1 in terms of composition;

[0068] (2) According to mass parts, 24 parts of completely water-free 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 24 parts of 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether and 42 parts of pentaerythritol tetraacrylate (PETEA), 10 parts of vinylene carbonate (VC) are stirred and uniformly mixed to obtain solution B;

[0069] (3) According to mass parts, 30 parts of solution A and 20 parts of solution B are stirred and uniformly mixed, 0.2 parts of azobisisobutyronitrile (AIBN) is added, and stirred and uniformly mixed to obtain an in-situ polymerization solid electrolyte precursor solution.

[0070] Example 7

[0071] An in-situ polymerization solid electrolyte precursor solution is prepared by the following steps:

[0072] (1) According to mass parts, 319 parts of lithium perchlorate is dissolved in 968 parts of solvent, and stirred until uniformly mixed to obtain solution A; wherein the solvent is the same as the solvent of Example 1;

[0073] (2) According to mass parts, 24 parts of completely water-free 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 24 parts of bis-perfluorononyl trifluoroethyl ether and 42 parts of pentaerythritol tetraacrylate (PETEA), 10 parts of vinylene carbonate (VC) are stirred and uniformly mixed to obtain solution B;

[0074] (3) According to mass parts, 30 parts of solution A and 20 parts of solution B are stirred and uniformly mixed, 0.2 parts of azobisisobutyronitrile (AIBN) is added, and stirred and uniformly mixed to obtain an in-situ polymerization solid electrolyte precursor solution.

[0075] Example 8

[0076] An in-situ polymerization solid electrolyte precursor solution is prepared by the following steps:

[0077] (1) According to mass parts, 581 parts of lithium bis(oxalate)borate is dissolved in 968 parts of solvent, and stirred until uniformly mixed to obtain solution A; wherein the solvent is the same as the solvent of Example 1;

[0078] (2) According to mass parts, 12 parts of completely water-free fluoroalkyl acrylate, 12 parts of perfluoroalkyl ethyl acrylate, 24 parts of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether and 42 parts of pentaerythritol tetraacrylate (PETEA), 10 parts of vinylene carbonate (VC) are stirred and uniformly mixed to obtain solution B;

[0079] (3) 30 parts of solution A and 20 parts of solution B were taken by mass fraction, stirred and mixed uniformly, 0.2 parts of azobisisobutyronitrile (AIBN) was added, stirred and mixed uniformly to obtain an in-situ polymerization solid-state electrolyte precursor solution.

[0080] Example 9

[0081] An in-situ polymerization solid-state electrolyte precursor solution was prepared by the following steps:

[0082] (1) 581 parts of lithium bisoxalate borate was dissolved in 968 parts of solvent by mass fraction, stirred and mixed uniformly to obtain solution A; wherein the solvent was the same as that of Example 1;

[0083] (2) 24 parts of fluorine alkyl acrylate, 24 parts of 1,1,2,2-tetrafluoroethyl methyl ether and 42 parts of pentaerythritol tetraacrylate (PETEA) were stirred and mixed uniformly to obtain solution B; (3) 30 parts of solution A and 20 parts of solution B were taken by mass fraction, stirred and mixed uniformly, 0.2 parts of azobisisobutyronitrile (AIBN) was added, stirred and mixed uniformly to obtain an in-situ polymerization solid-state electrolyte precursor solution.

[0084] Comparative Example 1

[0085] A solid-state electrolyte precursor solution was prepared by basically the same method as Example 1, except that 2,2,2-trifluoroethyl methyl acrylate (TFEA) monomer was not added in solution B.

[0086] Comparative Example 2

[0087] A solid-state electrolyte precursor solution was prepared by basically the same method as Example 1, except that bis(2,2,2-trifluoroethyl) ether (BTFE) diluent was not added in solution B.

[0088] Comparative Example 3

[0089] A solid-state electrolyte precursor solution was prepared by basically the same method as Example 1, except that in solution B, the mass fraction of 2,2,2-trifluoroethyl methyl acrylate (TFEA) was 40 parts and the mass fraction of bis(2,2,2-trifluoroethyl) ether (BTFE) was 8 parts.

[0090] Comparative Example 4

[0091] A solid-state electrolyte precursor solution was prepared by basically the same method as Example 1, except that in solution B, the mass fraction of 2,2,2-trifluoroethyl methyl acrylate (TFEA) was 8 parts and the mass fraction of bis(2,2,2-trifluoroethyl) ether (BTFE) was 40 parts.

[0092] The precursor solutions prepared from Examples 1-9 and Comparative Examples 1-4 were subjected to viscosity tests, and the test results are shown in Table 1; at the same time, the precursor solutions prepared from Examples 1-9 and Comparative Examples 1-4 were used in solid-state batteries, and the solid-state batteries were assembled in the order of positive shell-positive material-low viscosity local high concentration in-situ polymerization solid-state electrolyte precursor solution-separator-low viscosity local high concentration in-situ polymerization solid-state electrolyte precursor solution-lithium metal sheet-gasket-spring-negatve shell, and after assembly, the batteries were compressed and sealed under a 100 kPa hydraulic press, and then left to stand for 4 h, and then subjected to in-situ polymerization at 70°C for 90 min; after polymerization, the batteries were left to stand at room temperature for 12 h, and then subjected to electrochemical performance tests, including: placing the batteries in an electrochemical workstation for AC impedance and linear voltammetry tests; and placing the batteries in a NEWARE charge-discharge tester for rate charge-discharge tests according to the steps of: 5 cycles at a current density of 0.1C-5 cycles at a current density of 0.2C-5 cycles at a current density of 0.5C-5 cycles at a current density of 1C-5 cycles at a current density of 2C-5 cycles at a current density of 0.1C. The specific test results are shown in Table 1 and Figures 1-4

[0093] Table 1

[0094]

[0095]

[0096] As can be seen from the viscosity of the precursor solution measured in Examples 1-9 in Table 1, after adding the diluent, the viscosity of the system is significantly reduced; however, since the addition of different diluents will have different effects on the performance, the appropriate diluent needs to be selected according to the material properties. As can be seen from the viscosity of Comparative Example 1 and Comparative Example 2, if no monomer or diluent is added, the viscosity of the system will be large; and as can be seen from the ionic conductivity of Comparative Example 2, the ionic conductivity of the solid-state battery prepared therefrom is also significantly lower than that of Example 1. As can be seen by comparing Comparative Example 3 and Comparative Example 4, the ratio of monomer to diluent will significantly affect the performance of the material: specifically, significantly less diluent than monomer will result in a less obvious decrease in viscosity; significantly more diluent than monomer will result in a lower level of ionic conductivity.

[0097] As can be seen from Figure 1 , the solid-state battery prepared in Example 1 has the characteristic of local high concentration, and its ionic conductivity is higher than that of Comparative Example 1 which uses a high-concentration electrolyte as a solid-state electrolyte, because a low-viscosity and lithium-ion local high-concentration electrolyte is more conducive to the shuttling of lithium ions, and thus has a higher ionic conductivity; as can be seen from Figure 2 ​It can be seen that the example 1 has a wider electrochemical window than the comparative example 2, thereby indicating that the in-situ polymerization solid electrolyte precursor liquid of the present application has low viscosity, thus better wettability, and the obtained solid-state electrolyte has better contact with the electrode material and higher conductivity; thanks to the stable chemical bonding after polymerization, the obtained solid-state electrolyte has more stable chemical properties, thus has a higher electrochemical window; from Figure 3 It can be seen that the example 1 has lower impedance, which can adapt to large current charging and discharging application scenarios, because the precursor liquid prepared in the example 1 can form a local high concentration, and such local high concentration has lower impedance; from Figure 4 It can be seen that the discharge specific capacity and coulombic efficiency of the example 1 are higher than those of the comparative example 1 at each rate, and the example 1 shows better electrochemical performance.

[0098] It can be understood that for those skilled in the art, equivalent replacements or changes can be made according to the technical solutions and inventive concepts of the present application, and all such changes or replacements shall belong to the protection scope of the claims appended to the present application.

Claims

1. An in-situ polymerized solid electrolyte precursor solution, characterized in that, The raw materials for preparing this precursor solution include: monomers, diluents, crosslinking agents, lithium salts, solvents, and initiators; the mass ratio of the monomers, diluents, crosslinking agents, lithium salts, and solvents is 2:3; the monomers include small organic molecules containing fluorine and unsaturated functional groups; the small organic molecules containing fluorine and unsaturated functional groups include: methyl 2,2,2-trifluoroethyl acrylate, ethyl 2,2,2-trifluoroethyl acrylate, 1,1-bis(trifluoromethyl)-2,2,3,3,3,3-pentafluoropropyl 2-fluoroacrylate, methacrylate-2,2,3,3,4,4,4-heptafluorobutyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, and propylene glycol. The precursor solution comprises at least one of the following: fluoroalkyl acrylate, perfluoroalkyl ethyl acrylate, hexafluorobutyl methacrylate, and hexafluoroisopropyl methacrylate; the diluent is selected from at least one of the following: 2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, perfluorononenyl trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl methyl ether, and 1,1,1,3,3,3-hexafluoroisopropylmethyl ether; the viscosity of the precursor solution is ≤10 mPa·s; and the mass ratio of the monomer to the diluent is (1:2) to (2:1).

2. The in-situ polymerized solid electrolyte precursor solution according to claim 1, characterized in that, The monomer also includes vinylene carbonate.

3. The in-situ polymerized solid electrolyte precursor solution according to claim 1, characterized in that, The lithium salt is selected from one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium hexafluorophosphate, lithium perchlorate, and lithium dioxalate borate.

4. The in-situ polymerized solid electrolyte precursor solution according to claim 1, characterized in that, The crosslinking agent is pentaerythritol tetraacrylate or ethylene glycol dimethacrylate.

5. A solid-state battery, comprising a positive electrode, a separator, a negative electrode, and a solid electrolyte, characterized in that, The solid electrolyte is obtained by in-situ polymerization of the in-situ polymerized solid electrolyte precursor liquid as described in any one of claims 1-4.

6. The solid-state battery according to claim 5, characterized in that, The in-situ polymerization temperature is 70–90°C.

7. The solid-state battery according to claim 5, characterized in that, The diaphragm includes one of the following: polyimide membrane, glass cellulose membrane, polyvinylidene fluoride membrane, and unsaturated olefin polymer film.

Images