Method for preparing composite solid electrolyte through in-situ polymerization based on oxygen free radical catalysis

Abstract

The invention provides a method for preparing a composite solid electrolyte through in-situ polymerization based on oxygen free radical catalysis, and the composite solid electrolyte is prepared from the following raw material components in parts by weight: 20-40 parts of a small molecule polymerization monomer, 1-4 parts of an initiator, 2-6 parts of a lithium salt, 1-5 parts of a filler, 2-6 parts of a polymerization inhibitor and 10-20 parts of an organic solvent. When the prepared composite solid electrolyte is used for the lithium ion battery, the composite solid electrolyte has the characteristics of catalytic polymerization reaction, uniform polymerization reaction, cross-linked three-dimensional network structure, high ionic conductivity and the like, and the stability, the rate and the cycle performance of the semi-solid lithium ion battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method for preparing a composite solid electrolyte by in-situ polymerization based on oxygen free radical catalysis. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density and low self-discharge, and have become the most widely used electrochemical energy storage devices. They have been widely used in digital products, new energy vehicles and other fields. Currently, most of the commercial lithium-ion batteries use organic liquid electrolytes, but the energy density of liquid lithium batteries is close to the bottleneck. At the same time, when encountering extreme situations such as puncture and short circuit, they will cause fire and explosion accidents. Therefore, the commercial application of large-capacity, high-energy lithium secondary batteries is limited. Designing and developing high-performance electrolytes is very necessary to improve the safety performance and electrochemical performance of lithium secondary batteries.

[0003] Compared with the safety issues brought by traditional organic electrolytes, the use of solid electrolytes can greatly reduce the combustible components in the battery, greatly improving the safety performance of the battery. However, in such an electrode structure, the solid-solid interface impedance between the battery pole and the solid electrolyte is very large, which will affect the ionic conductivity of the electrode, and then lead to poor charge and discharge performance and rate performance of the battery. Polymer solid electrolytes have good flexibility and excellent interface contact, which can greatly improve the safety and cycle performance of existing lithium-ion batteries. However, the low ionic conductivity of polymer solid electrolytes at room temperature limits their industrial application, and the speed and uniformity of the polymerization reaction cannot be effectively controlled.

[0004] To solve the above problems, organic / inorganic composite solid electrolytes are often used to solve the problems of solid-state battery interface contact and ionic conductivity, but the in-situ curing reaction rate and polymerization heterogeneity of the polymer seriously affect the electrical performance of the battery. Therefore, it is necessary to develop a method for preparing composite solid electrolytes based on in-situ polymerization catalyzed by oxygen free radicals. Summary of the invention

[0005] The present application provides a method for preparing a composite solid electrolyte by in-situ polymerization based on oxygen free radical catalysis, so as to solve the problem of solid-state battery interface contact and ionic conductivity solved by the method of using organic / inorganic composite solid electrolyte in the prior art, but the problem that the in-situ curing reaction speed of the polymer and the heterogeneity of polymerization seriously affect the electrical performance of the battery, thereby achieving the purpose of improving the stability, rate and cycle performance of semi-solid lithium-ion batteries.

[0006] The present application provides a composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis. The raw material components for preparing the composite solid electrolyte include, by weight, 20-40 parts of a small molecule polymerization monomer, 1-4 parts of an initiator, 2-6 parts of a lithium salt, 1-5 parts of a filler, 2-6 parts of an inhibitor, and 10-20 parts of an organic solvent.

[0007] Preferably, the small molecule polymer monomer includes any one or a combination of at least two of acrylic acid, methacrylic acid, methyl methacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, acrylonitrile, ethylene carbonate, ethylene oxide or 1,3-dioxolane.

[0008] Preferably, the initiator includes any one of azobisisobutyronitrile, azobisisoheptanenitrile, azoisobutylcyanoformamide, dimethyl azobisisobutyrate, dicumyl peroxide or dibenzoyl peroxide, or a combination of at least two thereof.

[0009] Preferably, the lithium salt includes any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(difluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium bis(oxalatoborate), lithium difluorooxalatoborate or lithium bis(oxalatoborate), or a combination of at least two thereof.

[0010] Preferably, the filler includes a first filler and a second filler, the particle size of the first filler is 10nm-500nm; the first filler includes at least one of inorganic nano Al2O3, TiO2, SiO2, ZrO2, Ta2O5, and La2O3; the particle size of the second filler is 300-1000nm; the second filler includes at least one of Li(3x)La(2 / 3-x)TiO, Li1+xAlxTi2-x(PO4)3 (x=0.2-0.5), Li7-xLa3Zr2-xMxO12 (M is one of the metal elements Nb / Ta / Y / Ca, x=0-2), and sulfur-LISICON.

[0011] Preferably, the polymerization inhibitor includes any one of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-hydroquinone, 2-tert-butyl-hydroquinone, p-benzoquinone, methylhydroquinone or tetrachlorobenzoquinone, or a combination of at least two thereof.

[0012] Preferably, the organic solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, dimethoxymethane or acetonitrile, or a combination of at least two thereof.

[0013] Preferably, 1-4 parts of additives are also included, and the additives include any one or a combination of at least two of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, ethylene sulfate, and sodium dodecyl sulfate.

[0014] Preferably, a method for preparing a composite solid electrolyte based on in-situ polymerization catalyzed by oxygen free radicals comprises the following steps:

[0015] A. mixing a small molecule polymerization monomer, an initiator, a lithium salt, a filler and an organic solvent to obtain an in-situ curing electrolyte precursor;

[0016] B. Inject the in-situ curing electrolyte precursor into the battery cell, let it stand for 1 minute under a vacuum of -80 kPa, and let it stand for 12-48 hours in an environment of 20-35°C after vacuum packaging. The pressure during curing is 0.6-3 MPa, and it is cured at 45-80°C for 4-12 hours. The battery formation is completed at 70°C to obtain the in-situ curing composite solid electrolyte.

[0017] Preferably, based on the total mass of the in-situ solidified electrolyte precursor as 100%, the mass percentage of the small molecule polymerized monomer is 1%-40%, the mass percentage of the initiator to the mass percentage of the polymerized monomer is 0.01%-3%, the concentration of the lithium salt in the in-situ solidified electrolyte precursor is 1-3 mol / L, the mass percentage of the inhibitor to the mass percentage of the polymerized monomer is 0.0005%-10%, the mass percentage of the organic solvent is 60%-90%, and the mass percentage of the additive is 0-10%.

[0018] Beneficial effects:

[0019] (1) The preparation method of the present invention is simple. When the composite solid electrolyte is used in a lithium ion battery, it has the characteristics of catalytic polymerization reaction and uniform polymerization reaction, cross-linked three-dimensional network structure, high ion conductivity, etc., and can improve the stability, rate and cycle performance of semi-solid lithium ion batteries.

[0020] (2) The present invention adds a polymerization inhibitor to generate an induction period to delay the polymerization time of the polymerization monomer, and the curing reaction is carried out after the in-situ curing precursor liquid is fully infiltrated into the lithium ion battery, thereby forming an in-situ curing composite solid electrolyte with uniform curing.

[0021] (3) In the present invention, the first filler added to the raw materials for preparing the composite solid electrolyte, the inorganic nanofiller, on the one hand, reduces the crystallinity of the polymer after the polymerization reaction, and enhances the chain segment mobility of the polymer, which is beneficial to the transmission of lithium ions, thereby improving the ionic conductivity of the solid electrolyte; on the other hand, the inorganic nanofiller can serve as a polymerization reaction center and can be uniformly dispersed in the in-situ solidification precursor liquid, and then can be well dispersed in the pores of the positive electrode plate, which can effectively promote a uniform polymerization reaction, thereby forming a solidified uniform solid electrolyte. In addition, the inorganic nanofiller contacts with the active material, and lithium ions diffuse to the interface to form a fast ion layer, which is beneficial to improving the ionic conductivity while protecting the side reactions of the positive electrode material and the residual electrolyte, improving and enhancing the stability of the material, and improving the cycle performance of the battery.

[0022] (4) In the present invention, the second filler added to the raw materials for preparing the composite solid electrolyte, the micro-nano solid electrolyte filling, on the one hand, acts as a lithium ion fast conductor to provide high ion conductivity; on the other hand, the micro-nano solid electrolyte material forms a close contact with the active material and the polymer electrolyte interface, thereby reducing the impedance of the semi-solid lithium ion battery and improving the performance of the battery; at the same time, the micro-nano solid electrolyte is in close contact with the active material, diffuses on the surface of the active material during the electrochemical reaction to form a protective layer, stabilizes the structure of the active material and thereby improves the cycle performance of the battery.

[0023] The above description is only an overview of the technical solution of the embodiment of the present application. In order to more clearly understand the technical means of the embodiment of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase "embodiments" in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application is clearly and completely described below.

[0028] The present application provides a composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis. The raw material components for preparing the composite solid electrolyte include, by weight, 20-40 parts of a small molecule polymerization monomer, 1-4 parts of an initiator, 2-6 parts of a lithium salt, 1-5 parts of a filler, 2-6 parts of an inhibitor, and 10-20 parts of an organic solvent.

[0029] Embodiment 1:

[0030] The raw material components for preparing the composite solid electrolyte include, by weight, 20 parts of small molecule polymerization monomers, 1 part of initiator, 2 parts of lithium salt, 1 part of filler, 2 parts of inhibitor and 10 parts of organic solvent.

[0031] In this embodiment, the small molecule polymer monomer includes a combination of acrylic acid, methacrylic acid, and methyl methacrylate.

[0032] In this embodiment, the initiator includes azobisisobutyronitrile, azobisisoheptanenitrile, and azoisobutylcyanocyanide.

[0033] In this embodiment, the lithium salt includes a combination of lithium hexafluorophosphate and lithium tetrafluoroborate.

[0034] In this embodiment, the filler includes a first filler and a second filler, the particle size of the first filler is 10nm; the first filler includes a combination of inorganic nano-Al2O3 and TiO2; the particle size of the second filler is 300nm; the second filler includes Li(3x)La(2 / 3-x)TiO3.

[0035] In this embodiment, the polymerization inhibitor includes a combination of hydroquinone and p-hydroxyanisole.

[0036] In this embodiment, the organic solvent includes a combination of ethylene carbonate, propylene carbonate and dimethyl carbonate.

[0037] This embodiment further includes 1 part of additives, wherein the additives include a combination of vinylene carbonate and fluoroethylene carbonate.

[0038] In this embodiment, a method for preparing a composite solid electrolyte based on in-situ polymerization catalyzed by oxygen free radicals comprises the following steps:

[0039] A. mixing a small molecule polymerization monomer, an initiator, a lithium salt, a filler and an organic solvent to obtain an in-situ curing electrolyte precursor;

[0040] B. Inject the in-situ curing electrolyte precursor into the battery cell, let it stand for 1 minute under a vacuum of -80 kPa, and let it stand for 12 hours in a 20°C environment after vacuum packaging. The pressure during curing is 0.6 MPa, and it is cured at 45°C for 4 hours. The battery formation is completed at 70°C to obtain the in-situ curing composite solid electrolyte.

[0041] In this embodiment, taking the total mass of the in-situ curing electrolyte precursor as 100%, the mass percentage of the small molecule polymerized monomer is 5%, the mass percentage of the initiator to the mass percentage of the polymerized monomer is 1%, the concentration of the lithium salt in the in-situ curing electrolyte precursor is 1 mol / L, the mass percentage of the inhibitor to the mass percentage of the polymerized monomer is 1%, the mass percentage of the organic solvent is 90%, and the mass percentage of the additive is 3%.

[0042] Embodiment 2:

[0043] The raw material components for preparing the composite solid electrolyte include 40 parts of small molecule polymerization monomers, 4 parts of initiators, 6 parts of lithium salts, 5 parts of fillers, 6 parts of inhibitors and 20 parts of organic solvents in parts by weight.

[0044] In this embodiment, the small molecule polymer monomer includes a combination of pentaerythritol tetraacrylate and pentaerythritol triacrylate.

[0045] In this embodiment, the initiator includes azoisobutylcyanamide and dimethyl azobisisobutyrate.

[0046] In this embodiment, the lithium salt includes lithium bis(difluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

[0047] In this embodiment, the filler includes a first filler and a second filler, the particle size of the first filler is 500nm; the first filler includes a combination of inorganic nano-SiO2 and ZrO2; the particle size of the second filler is 1000nm; the second filler includes Li1+xAlxTi2-x(PO4)3(x=0.3).

[0048] In this embodiment, the polymerization inhibitor includes a combination of 2,6-di-tert-butyl-p-cresol and 2,5-di-tert-butyl-hydroquinone.

[0049] In this embodiment, the organic solvent includes a combination of dimethyl carbonate and diethyl carbonate.

[0050] This embodiment also includes 4 parts of additives, and the additives include a combination of propylene sulfite, ethylene sulfate, and sodium dodecyl sulfate.

[0051] In this embodiment, a method for preparing a composite solid electrolyte based on in-situ polymerization catalyzed by oxygen free radicals comprises the following steps:

[0052] A. mixing a small molecule polymerization monomer, an initiator, a lithium salt, a filler and an organic solvent to obtain an in-situ curing electrolyte precursor;

[0053] B. Inject the in-situ curing electrolyte precursor into the battery cell, let it stand for 1 minute under a vacuum of -80 kPa, and let it stand for 48 hours in a 35°C environment after vacuum packaging. The pressure during curing is 3 MPa, and it is cured at 80°C for 12 hours. The battery formation is completed at 70°C to obtain the in-situ curing composite solid electrolyte.

[0054] In this embodiment, taking the total mass of the in-situ solidifying electrolyte precursor as 100%, the mass percentage of the small molecule polymerized monomer is 20%, the mass percentage of the initiator to the mass percentage of the polymerized monomer is 3%, the concentration of the lithium salt in the in-situ solidifying electrolyte precursor is 3 mol / L, the mass percentage of the inhibitor to the mass percentage of the polymerized monomer is 10%, the mass percentage of the organic solvent is 63%, and the mass percentage of the additive is 4%.

[0055] Embodiment three:

[0056] The raw material components for preparing the composite solid electrolyte include, by weight, 30 parts of small molecule polymerization monomers, 3 parts of initiators, 4 parts of lithium salts, 3 parts of fillers, 4 parts of inhibitors and 15 parts of organic solvents.

[0057] In this embodiment, the small molecule polymer monomer includes a combination of acrylic acid, pentaerythritol tetraacrylate, and pentaerythritol triacrylate.

[0058] In this embodiment, the initiator includes azobisisobutyronitrile, dimethyl azobisisobutyrate, and dicumyl peroxide.

[0059] In this embodiment, the lithium salt includes a combination of lithium bis(difluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(oxalatoborate).

[0060] In this embodiment, the filler includes a first filler and a second filler, the particle size of the first filler is 100nm; the first filler includes a combination of inorganic nano-Al2O3 and ZrO2; the particle size of the second filler is 600nm; the second filler includes Li(3x)La(2 / 3-x)TiO3.

[0061] In this embodiment, the polymerization inhibitor includes a combination of 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-hydroquinone, and 2-tert-butyl-hydroquinone.

[0062] In this embodiment, the organic solvent includes a combination of diethyl carbonate, ethyl methyl carbonate, and dimethoxymethane.

[0063] This embodiment further includes 1-4 parts of additives, wherein the additives include a combination of propylene sulfite, ethylene sulfate, and sodium dodecyl sulfate.

[0064] In this embodiment, a method for preparing a composite solid electrolyte based on in-situ polymerization catalyzed by oxygen free radicals comprises the following steps:

[0065] A. mixing a small molecule polymerization monomer, an initiator, a lithium salt, a filler and an organic solvent to obtain an in-situ curing electrolyte precursor;

[0066] B. Inject the in-situ curing electrolyte precursor into the battery cell, let it stand for 1 minute under a vacuum of -80 kPa, and let it stand for 36 hours in a 30°C environment after vacuum packaging. The pressure during curing is 2 MPa, and it is cured at 70°C for 8 hours. Complete the battery formation at 70°C to obtain the in-situ curing composite solid electrolyte.

[0067] In this embodiment, taking the total mass of the in-situ solidifying electrolyte precursor as 100%, the mass percentage of the small molecule polymerized monomer is 20%, the mass percentage of the initiator to the mass percentage of the polymerized monomer is 2%, the concentration of the lithium salt in the in-situ solidifying electrolyte precursor is 2 mol / L, the mass percentage of the inhibitor to the mass percentage of the polymerized monomer is 5%, the mass percentage of the organic solvent is 68%, and the mass percentage of the additive is 5%.

[0068] The positive electrode of the battery cell uses an oxygen-containing lithium battery material that can better provide oxygen free radicals. The oxygen-containing lithium battery material includes ultra-high nickel ternary material LiNi(1-xy)CoxMnyO2(0<x,y<0.05), ultra-high nickel quaternary material LiNi(1-xyz)CoxMnyTO2(0<x,y,z<0.05,T=Al, Zr, W, Nb, Ta), xLi2MnO3(1-x)LiMO2(M=Ni, Co, Mn), Li2NiO2, etc. or any combination thereof. Oxygen-containing lithium battery materials provide oxygen free radicals mainly through two ways of excitation: ① Electrochemical reaction excitation of oxygen-containing lithium battery materials under high pressure: Ultra-high nickel materials (Ni≥0.9) are under high formation voltage (4.2 / 4.3V), and the Ni on the surface of the material 4+ Overlapping with the oxygen energy band, Ni 4+The decomposition of the strong oxidizing electrolyte releases active oxygen free radicals from the lattice oxygen; the xLi2MnO3(1-x)LiMO2(M=Ni, Co, Mn) material undergoes not only cation redox reaction but also anion O 2- The redox reaction (O 2- → O or O2 - →O2), it is easier to generate oxygen free radicals and catalyze polymerization reactions, but the release of oxygen will reduce the average valence state of the transition metal, resulting in cyclic voltage decay and deterioration of cycle performance; ② High temperature excitation: The activation energy of the electrochemical reaction of the material is reduced at high temperature, and lattice oxygen is more easily released to form oxygen free radicals.

[0069] Comparative Example

[0070] The comparative example is that the positive electrode material is conventional NCM622 material, and the rest is the same as that of Example 1.

[0071] Testing and analysis

[0072] Under the same conditions, the batteries prepared in the above Examples 1-3 and the comparative example were subjected to impedance tests and cycle performance tests. The specific test methods are as follows:

[0073] Under the same conditions, the batteries prepared in the above Examples 1-3 and the comparative example were subjected to impedance tests and cycle performance tests. The specific test methods are as follows:

[0074] Battery AC impedance: The battery of each embodiment and comparative example was tested on an electrochemical workstation with an AC impedance voltage signal of 10 mV and a frequency range of 10 6 -10 -2 Hz, ionic conductivity is calculated from EIS results combined with the ionic conductivity formula;

[0075] 25℃ cycle performance test: At 25℃, the lithium-ion battery is charged to 4.2V at a current density of 1C and a constant current and voltage, with a cut-off rate of 0.05C, and left for 10 minutes. Then, it is discharged to 2.75V at a current density of 1C and left for 10 minutes. The capacity retention rate of 500 cycles is tested (the capacity retention rate is terminated when it decays to 80%).

[0076] The test results are shown in the following table

[0077]

[0078] Combined with Table 1, it can be obtained that compared with the battery of Comparative Example 1, the batteries of Examples 1-3 have higher ionic conductivity, which is because the batteries of Examples 1-3 are semi-solid batteries made of composite solid electrolytes catalyzed by oxygen in situ curing provided by the present invention. Comparing Examples 1 and 2, the ionic conductivity of the lithium-rich manganese-based material is slightly lower and the cycle performance is poor, which is related to the inherent properties of the lithium-rich manganese-based material. It is necessary to further optimize and modify the oxygen release of the lithium-rich manganese-based material to cause voltage decay and manganese dissolution. Comparing Examples 1 and 3, the mixed system of ultra-high nickel positive electrode and lithium-rich manganese-based, the synergistic effect of both parties optimizes the overall electrochemical performance of the battery, and the ionic conductivity and cycle performance are improved. Comparing Example 1 and the comparative example, the conventional 622 positive electrode material is not easy to release lattice oxygen due to the stability of the structure, and it is impossible to better catalyze the polymerization reaction to form a uniform three-dimensional network structure, so the ionic conductivity is slightly low, but the battery has excellent cycle performance (NCM622 material structural stability is better than ultra-high nickel ternary and lithium-rich manganese-based materials).

[0079] In summary, the preparation method of the present invention is simple. When the prepared composite solid electrolyte is used in lithium-ion batteries, it has the characteristics of catalytic polymerization reaction and uniform polymerization reaction, cross-linked three-dimensional network structure, high ion conductivity, etc., which can improve the stability, rate and cycle performance of semi-solid lithium-ion batteries.

[0080] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis, characterized in that: The raw material components for preparing the composite solid electrolyte include 20-40 parts of small molecule polymerization monomers, 1-4 parts of initiators, 2-6 parts of lithium salts, 1-5 parts of fillers, 2-6 parts of inhibitors and 10-20 parts of organic solvents in parts by weight.

2. The composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis according to claim 1, characterized in that: The small molecule polymer monomer includes any one of acrylic acid, methacrylic acid, methyl methacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, acrylonitrile, ethylene carbonate, ethylene oxide or 1,3-dioxolane, or a combination of at least two thereof.

3. The composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis according to claim 1, characterized in that: The initiator includes any one of azobisisobutyronitrile, azobisisoheptanenitrile, azoisobutylcyanoformamide, dimethyl azobisisobutyrate, dicumyl peroxide or dibenzoyl peroxide, or a combination of at least two thereof.

4. The composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis according to claim 1, characterized in that: The lithium salt includes any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(difluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalato)borate, lithium difluorooxalatoborate or lithium bis(oxalato)borate, or a combination of at least two thereof.

5. The composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis according to claim 1, characterized in that: The filler includes a first filler and a second filler, the particle size of the first filler is 10nm-500nm; the first filler includes at least one of inorganic nano Al2O3, TiO2, SiO2, ZrO2, Ta2O5, and La2O3; the particle size of the second filler is 300-1000nm; the second filler includes at least one of Li(3x)La(2 / 3-x)TiO3, Li1+xAlxTi2-x(PO4)3 (x=0.2-0.5), Li7-xLa3Zr2-xMxO12 (M is one of the metal elements Nb / Ta / Y / Ca, x=0-2), and sulfur-LISICON.

6. The composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis according to claim 4 or 5, characterized in that: The polymerization inhibitor includes any one of hydroquinone, p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-hydroquinone, 2-tert-butyl-hydroquinone, p-benzoquinone, methyl hydroquinone or tetrachlorobenzoquinone, or a combination of at least two thereof.

7. The composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis according to claim 1, characterized in that: The organic solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, dimethoxymethane or acetonitrile, or a combination of at least two thereof.

8. The composite solid electrolyte prepared by in-situ polymerization based on oxygen free radical catalysis according to claim 1, characterized in that: The invention also includes 1 to 4 parts of additives, wherein the additives include any one of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, ethylene sulfate, and sodium dodecyl sulfate, or a combination of at least two of them.

9. A method for preparing a composite solid electrolyte based on in-situ polymerization catalyzed by oxygen free radicals, characterized in that: The steps include: A. mixing a small molecule polymerization monomer, an initiator, a lithium salt, a filler and an organic solvent to obtain an in-situ curing electrolyte precursor; B. Inject the in-situ curing electrolyte precursor into the battery cell, let it stand for 1 minute under a vacuum of -80 kPa, and let it stand for 12-48 hours in an environment of 20-35°C after vacuum packaging. The pressure during curing is 0.6-3 MPa, and it is cured at 45-80°C for 4-12 hours. The battery formation is completed at 70°C to obtain the in-situ curing composite solid electrolyte.

10. The method for preparing a composite solid electrolyte based on in-situ polymerization catalyzed by oxygen free radicals according to claim 9, characterized in that: Taking the total mass of the in-situ solidified electrolyte precursor as 100%, the mass percentage of the small molecule polymerized monomer is 1%-40%, the mass percentage of the initiator to the mass percentage of the polymerized monomer is 0.01%-3%, the concentration of the lithium salt in the in-situ solidified electrolyte precursor is 1-3 mol / L, the mass percentage of the inhibitor to the mass percentage of the polymerized monomer is 0.0005%-10%, the mass percentage of the organic solvent is 60%-90%, and the mass percentage of the additive is 0-10%.

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