A method for preparing a solid-state battery

Abstract

The present invention discloses a method for preparing a solid-state battery, comprising the following steps: S1, preparing PVDF polymer electrolyte slurry; S2, in-situ curing of electrolyte film; S3, preparing grafted monomer solution; S4, in-situ grafting polymerization on the electrolyte surface. The present invention effectively improves the problem of lithium ion transmission between the solid electrolyte film and the electrode by coating the electrolyte slurry on the surface of the positive and negative pole pieces, and the contact is good after curing. At the same time, PVDF polymers have the advantages of high dielectric constant, good thermal stability, resistance to chemical medium corrosion, high mechanical strength, strong flexibility, etc., which effectively improves the cycle stability and safety of the battery. In order to further improve the contact performance of the interface, the present invention further grafts and polymerizes the PVDF electrolyte film layer on the positive and negative pole pieces by adding a grafted monomer solution to the battery cell and curing in situ, thereby further improving the contact performance of the interface, and the corresponding solid-state battery performance can also be further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and in particular relates to a method for preparing a solid-state battery. Background Art

[0002] At present, the growing development of new energy industries such as consumer electronics, electric vehicles, and large-scale energy storage has put forward higher requirements for the safety and energy density of secondary batteries. The liquid electrolytes in secondary batteries are currently inflammable, explosive, and easy to erupt in the event of failure or abuse, causing certain safety issues in the use of secondary batteries. Therefore, how to improve the safety performance of liquid electrolytes is an urgent problem to be solved. Solid electrolytes have a higher thermal decomposition temperature than liquid electrolytes. Therefore, the development of solid electrolytes is one of the current research directions to significantly improve the safety of lithium batteries.

[0003] Common solid electrolytes include oxides, sulfides and polymer electrolytes. Among them, polymer electrolytes have better performance than oxide or sulfide electrolytes, mainly in the following aspects: 1. The interface contact performance of polymer electrolytes is significantly better than that of oxide and sulfide solid electrolytes, so its interface impedance is small; 2. Polymers do not react in the air and have stable performance; and unlike sulfide solid electrolytes and garnet oxide solid electrolytes, polymer solid electrolytes are not easy to decompose when exposed to water, so they have higher safety performance; 3. Polymer electrolytes have good mechanical properties and are easy to process, which is conducive to large-scale production and application; 4. Polymer electrolytes have high stability to low-potential negative electrodes.

[0004] However, although the interface contact of various polymer electrolyte membranes is better than that of oxide and sulfide solid electrolytes, it is still far behind that of traditional electrolytes. The electrode and the solid electrolyte are in point contact, which is prone to cracks and pores, limiting the transmission of lithium ions at the interface, thereby shortening the battery life and increasing safety risks. Therefore, further improving the contact performance between the polymer electrolyte and the electrode plate will be of great significance to improving the performance of solid-state batteries. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a solid-state battery, which can further improve the problem of interface contact between the positive and negative electrodes and the electrolyte membrane, thereby further improving the cycle stability and safety of the battery.

[0006] In a first aspect, the present invention provides a method for preparing a solid-state battery, using the following technical solution:

[0007] A method for preparing a solid-state battery comprises the following steps:

[0008] S1. preparing PVDF polymer electrolyte slurry;

[0009] S2, in-situ curing of the electrolyte film: applying the PVDF polymer electrolyte slurry in step S1 to the two surfaces of the positive electrode sheet and the two surfaces of the negative electrode sheet respectively, and after drying, obtaining the positive electrode sheet with the electrolyte film layer and the negative electrode sheet with the electrolyte film layer;

[0010] S3, preparing a grafting monomer solution: dissolving a grafting monomer, an initiator, a catalyst, a ligand, and a lithium salt in a solvent to obtain a grafting monomer solution;

[0011] S4, in-situ graft polymerization on the electrolyte surface: assemble the positive electrode sheet with the electrolyte membrane layer and the negative electrode sheet with the electrolyte membrane layer in step S2 into a battery cell by stacking; add the grafted monomer solution in step S3 to the battery cell, encapsulate it, heat and cure it, and obtain a solid-state battery.

[0012] Preferably, in step S1, the specific method for preparing the PVDF polymer electrolyte slurry is: adding lithium salt and PVDF polymer into solvent 1, stirring and mixing, and obtaining the PVDF polymer electrolyte slurry.

[0013] Preferably, the PVDF polymer is one or more of polyvinylidene fluoride PVDF, polyvinylidene fluoride-hexafluoropropylene copolymer P (VDF-HFP), polytrifluoroethylene-vinylidene fluoride copolymer P (VDF-TrFE), polychlorotrifluoroethylene-vinylidene fluoride copolymer P (VDF-CTFE), polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene copolymer (P (VDF-TrFE-CTFE)); the concentration of the PVDF polymer is 50~170g / L.

[0014] Preferably, the lithium salt is one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, lithium dioxalatoborate, and lithium nitrate; and the concentration of the lithium salt is 15-75 g / L.

[0015] Preferably, solvent 1 is N-methylpyrrolidone (NMP), N,N - one or more of dimethylformamide (DMF) and tetrahydrofuran (THF).

[0016] Preferably, in step S2, the positive electrode plate is one of a lithium cobalt oxide positive electrode plate, a lithium manganese oxide positive electrode plate, a lithium iron phosphate positive electrode plate, and a ternary positive electrode plate; the negative electrode plate is one of a carbon material negative electrode, a silicon-carbon negative electrode, and a metal lithium negative electrode.

[0017] Preferably, in step S2, the thickness of the electrolyte membrane layer on each surface of the positive electrode sheet and the negative electrode sheet is 10-30 μm.

[0018] Preferably, in step S2, during drying, the mixture is first dried at room temperature for 6 to 24 hours, and then dried at 60 to 90° C. for 0.5 to 2 hours.

[0019] Preferably, in step S3, the monomer is dimethylaminoethyl methacrylate (DMAEMA) or polyethylene glycol methacrylate (PEGMA), and the monomer concentration is 1.5-4 mol / L;

[0020] The initiator is ethyl 2-bromoisobutyrate (EBiB), and the initiator concentration is 0.01~0.05mol / L;

[0021] The catalyst is CuCl or CuBr, and the catalyst concentration is 0.01~0.05mol / L;

[0022] The ligand is 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), and the ligand concentration is 0.01~0.05mol / L.

[0023] Preferably, in step S3, the lithium salt is one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, lithium dioxalatoborate, and lithium nitrate, and the concentration of the lithium salt is 25-100 g / L.

[0024] Preferably, in step S3, the solvent is one or more of tetrahydrofuran, acetone, and 1,3-bis(1,1,2,2-tetrafluoroethoxy)propane.

[0025] Preferably, in step S4, the ratio of the amount of grafted monomer solution added to the cell capacity is 1.5-2.5 g / Ah; the heating curing temperature is 50-70° C., and the heating curing time is 10-24 h.

[0026] The steps S3 and S4 need to be performed in an anhydrous and oxygen-free environment.

[0027] In a second aspect, the present invention provides a solid-state battery prepared using the above-mentioned preparation method.

[0028] In the present invention, a PVDF polymer electrolyte membrane is first prepared on the surface of the positive electrode sheet and the negative electrode sheet. The upper surface of the PVDF polymer electrolyte membrane contains a large number of CF bonds, which can be directly initiated by ATRP graft polymerization by alkyl fluoride (the specific reaction equation can be seen in Figure 1 ), PMMA is cross-linked and grafted on the surface of the PVDF polymer electrolyte membrane layer, thereby realizing the polymerization link between the polymer electrolyte membranes on both sides of the positive and negative electrodes, effectively improving the interface contact problem.

[0029] Beneficial effects of the present invention:

[0030] 1) The present invention coats the surface of the positive and negative pole pieces with PVDF polymer electrolyte slurry, which has good contact after curing, effectively improving the problem of lithium ion transmission between the solid electrolyte film and the electrode. At the same time, PVDF polymers have the advantages of high dielectric constant, good thermal stability, chemical corrosion resistance, high mechanical strength, and strong flexibility, which effectively improves the cycle stability and safety of the battery. In order to further improve the contact performance of the interface, the present invention adds a grafted monomer solution to the battery cell, and through an in-situ curing method, the PVDF electrolyte film layer on the positive and negative pole pieces is further grafted, polymerized and cross-linked, thereby further improving the contact performance of the interface, and the performance of the solid-state battery is also further improved.

[0031] 2) The solid-state battery preparation method provided by the present invention is simple and has low energy consumption. The battery does not require pressurization during use, which is convenient for promotion and industrialization and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the schematic diagram of PMMA grafted onto the surface of PVDF polymer solid electrolyte.

[0033] Figure 2 This is a cycle performance diagram of the solid-state batteries prepared in Example 1 and Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0034] Figure 3 The cycle performance diagram of the solid-state batteries prepared in Example 2 and Example 3.

[0035] Figure 4 The cycle performance diagram of the solid-state batteries prepared in Example 4 and Example 5.

[0036] Figure 5 This is a SEM image of the cross-section of the disassembled battery cell of the solid-state battery prepared in Example 6. DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0038] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0040] Example 1

[0041] The method for preparing the solid-state battery of this embodiment comprises the following steps:

[0042] Step 1: Take 0.8 g LiFSI and 1 g P(VDF-HFP) and dissolve them in 12 g DMF to obtain a polymer solid electrolyte slurry.

[0043] Step 2: Take the NCM622 positive electrode sheet, the positive electrode size is 43*56 mm, and the surface density is 22.3 mg / cm 2 ; Select artificial graphite negative electrode sheet, the negative electrode size is 45*58 mm, and the surface density is 12.6 mg / cm 2 . Use a 200μm scraper to evenly coat part of the polymer solid electrolyte slurry in step S1 on the surface of the NCM622 positive electrode sheet and the artificial graphite negative electrode sheet, then dry at room temperature for 12 hours, transfer to a 70℃ forced air oven and dry for 1 hour. After drying, the thickness of the polymer solid electrolyte membrane is about 20μm. Then, use the same method to coat the other side of the NCM622 positive electrode sheet and the artificial graphite negative electrode sheet with the polymer solid electrolyte slurry. After drying, remove the excess polymer electrolyte membrane on the edge of the electrode sheet and the ear, and obtain the positive electrode sheet with an electrolyte membrane layer and the negative electrode sheet with an electrolyte membrane layer.

[0044] Step 3: In a glove box, take 0.5 g LiFSI, 3.25 mL DMAEMA, 13.2 mg CuBr, and 24.6 μL HMTETA and dissolve them in 3 mL tetrahydrofuran. After they are completely dissolved, add 13.2 μL EBiB and mix well to obtain a grafted monomer solution.

[0045] Step 4: In a glove box, take 6 positive electrode sheets with electrolyte membrane layers obtained in step 2 and 7 negative electrode sheets with electrolyte membrane layers, and obtain a 0.5Ah battery cell by stacking them. After welding the pole ears, put them into aluminum-plastic film for top and side sealing, add 1.25 g of the grafted monomer solution obtained in step 3 to the battery cell, let it stand in vacuum for 5 min, perform vacuum pre-sealing, and then transfer it to a 60°C oven for curing for 12 h. After curing, separate the capacity and finally seal it to obtain a solid-state battery.

[0046] Comparative Example 1

[0047] The method is basically the same as Example 1, except that the grafting monomer solution is not prepared in step 3, and the grafting monomer solution is not added in the corresponding step 4, and the corresponding solid-state battery is prepared.

[0048] Step 4 is as follows:

[0049] Step 4: In a glove box, take 6 positive electrode sheets with electrolyte membrane layers obtained in step 2 and 7 negative electrode sheets with electrolyte membrane layers, and obtain 0.5Ah battery cells by stacking them. After welding the pole ears, put them into aluminum-plastic film for top and side sealing and vacuum pre-sealing, and then transfer them to a 60°C oven for 12 hours. After capacity separation and final sealing, a solid-state battery is obtained.

[0050] Comparative Example 2

[0051] The preparation method of the solid-state battery in this comparative example is:

[0052] Step 1: Take 0.8g LiFSI and 1g P(VDF-HFP), dissolve them in 12g DMF to obtain polymer solid electrolyte slurry; apply the polymer solid electrolyte slurry on a glass plate with a 200μm scraper, dry it at room temperature for 12h, and then transfer it to a 70℃ forced air oven and dry it for 1h; obtain a polymer solid electrolyte membrane and cut it into a size of 47*60mm.

[0053] Step 2: In a glove box, 0.5 g LiFSI, 3.25 mL DMAEMA, 13.2 mg CuBr, and 24.6 μL HMTETA were dissolved in 3 mL tetrahydrofuran. After complete dissolution, 13.2 μL EBiB was added and mixed well to obtain a grafting monomer solution.

[0054] Step 3: In a glove box, take 6 NCM622 positive electrode sheets, 7 graphite negative electrode sheets, and 14 polymer solid electrolyte membranes, and obtain a 0.5Ah battery cell by stacking. After welding the pole ears, put them into an aluminum-plastic film for top and side sealing. Add 1.25 g of the grafted monomer solution obtained in step 2 to the battery cell. After standing in vacuum for 5 minutes, perform vacuum pre-sealing, transfer to a 60°C oven for curing for 12 hours, and after curing, divide the volume and finally seal to obtain a solid-state battery.

[0055] Comparative Example 3

[0056] It is basically the same as Example 1, except that there is no preparation of the polymer solid electrolyte slurry in step 1 and preparation of the solid electrolyte membrane in step 2. In the corresponding step 4, a conventional electrode is used and only the grafted monomer solution is added to prepare the corresponding solid-state battery.

[0057] The details are as follows:

[0058] Step 1: In a glove box, 0.5 g LiFSI, 3.25 mL DMAEMA, 13.2 mg CuBr, and 24.6 μL HMTETA were dissolved in 3 mL tetrahydrofuran. After complete dissolution, 13.2 μL EBiB was added and mixed well to obtain a grafting monomer solution.

[0059] Step 2: In a glove box, take 6 NCM622 positive electrode sheets and 7 graphite negative electrode sheets, and use the stacking method to obtain a 0.5Ah battery cell. After welding the pole ears, put them into an aluminum-plastic film for top and side sealing. Add 1.25 g of the grafted monomer solution obtained in step 3 to the battery cell. After standing in a vacuum for 5 minutes, perform vacuum pre-sealing, and then transfer to a 60°C oven for curing for 12 hours. After curing, separate the capacity and finally seal to obtain a solid-state battery.

[0060] The solid-state batteries prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were subjected to charge and discharge tests. The samples were activated for 2 cycles at a current density of 0.1C at room temperature and a voltage window of 2.8-4.3V, and a long cycle test (450 cycles) was performed at a rate of 1C.

[0061] Figure 2 The cycle performance diagram of the solid-state battery prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. It can be seen that the 1C first cycle discharge capacity of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are 560.4mAh, 558.6mAh, 444.5mAh, and 477.0mAh, respectively, and the discharge capacity after 450 cycles is 486.7mAh, 364.8mAh, 101.3mAh, and 163.1mAh, respectively, and the 450-cycle capacity retention rate is 86.85%, 65.30%, 22.79%, and 34.19%, respectively.

[0062] It can be seen that the polymer solid electrolyte designed in the present invention is in-situ solidified on the surface of the electrode, and the surface graft polymerization method is used to solve the interface problem between the solid electrolyte membranes. The material exerts a higher capacity, has better cycle performance and capacity retention rate in long cycles, and extends the battery life.

[0063] Example 2

[0064] It is basically the same as Example 1, except that the amount of grafted monomer solution added in step 4 is 1.5 g, and the corresponding solid-state battery is prepared.

[0065] Example 3

[0066] It is basically the same as Example 1, except that the amount of grafted monomer solution added in step 4 is 0.075 g, and the corresponding solid-state battery is prepared.

[0067] The solid-state batteries prepared in Example 2 and Example 3 were subjected to charge and discharge tests. The samples were activated for 2 cycles at a current density of 0.1C at room temperature and a voltage window of 2.8-4.3V, and a long cycle test (450 cycles) was performed at a rate of 1C.

[0068] Figure 3The figure is a cycle performance diagram of the solid-state battery prepared in Example 2 and Example 3. It can be seen that the 1C first cycle discharge capacity of Example 2 and Example 3 is 563.8 mAh and 559.2 mAh respectively, and the discharge capacity after 450 cycles is 463.2 mAh and 438.4 mAh respectively, and the 450 cycle capacity retention rate is 82.16% and 78.39% respectively.

[0069] Example 4

[0070] The method for preparing a solid-state battery in this embodiment comprises the following steps:

[0071] Step 1: 0.75 g LiODFB and 1.1 g P(VDF-CTFE) were dissolved in 13 g DMF to obtain a polymer solid electrolyte slurry.

[0072] Step 2: Take the NCM811 positive electrode sheet, the positive electrode size is 43*56 mm, and the surface density is 31 mg / cm 2 ; Select silicon carbon 450 negative electrode sheet, the negative electrode size is 45*58 mm, and the surface density is 15 mg / cm 2 ; Use a 220μm scraper to evenly coat part of the polymer solid electrolyte slurry on the surface of the NCM811 positive electrode sheet and the silicon carbon 450 negative electrode sheet; then dry at room temperature for 12 hours, transfer to a 60℃ forced air oven and dry for 2 hours. After drying, the thickness of the polymer solid electrolyte membrane is about 20μm; use the same method to coat the other surface of the NCM811 positive electrode sheet and the silicon carbon 450 negative electrode sheet with the polymer solid electrolyte slurry. After drying, remove the excess solid electrolyte membrane on the edge of the sheet and the ear to obtain a positive electrode sheet with an electrolyte membrane layer and a negative electrode sheet with an electrolyte membrane layer.

[0073] Step 3: In a glove box, 0.3 g LiODFB, 2.87 mL DMAEMA, 19.7 mg CuBr, and 31.7 μL HMTETA were dissolved in 3 mL tetrahydrofuran. After complete dissolution, 18.2 μL EBiB was added and mixed well to obtain a grafted monomer solution.

[0074] Step 4: In a glove box, take 6 positive electrode sheets with electrolyte membrane layers obtained in step 2 and 7 negative electrode sheets with electrolyte membrane layers, and obtain a 0.5Ah battery cell by stacking them. After welding the pole ears, put them into aluminum-plastic film for top and side sealing, add 1.0 g of the grafted monomer solution obtained in step 3, let it stand in vacuum for 5 minutes, perform vacuum pre-sealing, and then transfer to a 50°C oven for curing for 15 hours. After curing, separate the volumes and perform final sealing to obtain a solid battery.

[0075] Example 5

[0076] The method for preparing a solid-state battery in this embodiment comprises the following steps:

[0077] Step 1: 0.945 g LiFSI and 1.2 g P(VDF-HFP) were dissolved in 11.2 g THF to obtain a polymer solid electrolyte slurry.

[0078] Step 2: In the glove box, take the lithium iron phosphate positive electrode sheet, the positive electrode size is 43*56 mm, and the surface density is 27 mg / cm 2 ; Select a lithium metal negative electrode sheet with a copper mesh, and the negative electrode size is 45*58 mm; use a 150μm scraper to evenly coat part of the polymer solid electrolyte slurry on the surface of the lithium iron phosphate positive electrode sheet and the lithium metal negative electrode sheet, then dry at room temperature for 12 hours, transfer to a 90℃ forced air oven and dry for 0.5 hours. After drying, the thickness of the polymer solid electrolyte film is about 15μm; then use the same method to coat the other side of the lithium iron phosphate positive electrode sheet and the lithium metal negative electrode sheet with the polymer solid electrolyte slurry. After drying, remove the excess solid electrolyte film on the edge of the electrode sheet and the ear to obtain a positive electrode sheet with an electrolyte film layer and a negative electrode sheet with an electrolyte film layer.

[0079] Step 3: In a glove box, 0.70 g LiFSI, 4.05 mL DMAEMA, 20.5 mg CuBr, and 27.6 μL HMTETA were dissolved in 3 mL tetrahydrofuran. After complete dissolution, 15.3 μL EBiB was added and mixed well to obtain a grafted monomer solution.

[0080] Step 4: In a glove box, take 12 positive electrode sheets with electrolyte membrane layers obtained in step 2 and 14 negative electrode sheets with electrolyte membrane layers, and obtain a 1.0Ah battery cell by stacking them. After welding the pole ears, put them into aluminum-plastic film for top and side sealing, add 2.5g of the grafted monomer solution obtained in step 3, let it stand in vacuum for 5 minutes, and then perform vacuum pre-sealing. Transfer it to a 70°C oven for curing for 10 hours. After curing, divide the volume and finally seal it to obtain a solid-state battery.

[0081] The solid-state batteries prepared in Example 4 and Example 5 were subjected to charge and discharge tests. The samples were activated for 2 cycles at a current density of 0.1C at room temperature and a voltage window of 2.8-4.3V, and a long cycle test (300 cycles) was performed at a rate of 1C.

[0082] Figure 4 The cycle performance diagram of the solid-state battery prepared in Example 4 and Example 5. It can be seen that the 1C first cycle discharge capacity of Example 4 and Example 5 is 503.1 mAh and 490.1 mAh respectively, and the discharge capacity after 300 cycles is 480.3 mAh and 449.2 mAh respectively, and the 300 cycle capacity retention rate is 95.47% and 99.65% respectively.

[0083] Example 6

[0084] In order to better observe the interface contact of the solid-state battery, in this embodiment, the positive electrode sheet with an electrolyte membrane layer and the negative electrode sheet with an electrolyte membrane layer prepared in step 2 of embodiment 1 and the grafting solution prepared in step S3 are used to assemble a solid-state battery with a single electrode sheet. The specific steps are as follows:

[0085] In the glove box, take one positive electrode sheet with an electrolyte membrane layer and one negative electrode sheet with an electrolyte membrane layer, and use the stacking method to obtain a 0.05Ah battery cell. After welding the pole ears, put them into aluminum-plastic film for top and side sealing, add 0.125g of grafted monomer solution to the battery cell, let it stand in vacuum for 5 minutes, and then perform vacuum pre-sealing. Then transfer it to a 60℃ oven for curing for 12 hours. After curing, separate the capacity and finally seal it to obtain a solid-state battery.

[0086] The solid-state battery is disassembled, the battery cell is taken out, and the battery cell is fractured with liquid nitrogen. The cross-section is observed. Figure 5 : It can be seen that the solid electrolyte is very tightly bonded to the positive electrode sheet and the negative electrode sheet.

[0087] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a solid-state battery, characterized in that: The following steps are involved: S1. preparing PVDF polymer electrolyte slurry; S2, in-situ curing of the electrolyte film: applying the PVDF polymer electrolyte slurry in step S1 to the two surfaces of the positive electrode sheet and the two surfaces of the negative electrode sheet respectively, and after drying, obtaining the positive electrode sheet with the electrolyte film layer and the negative electrode sheet with the electrolyte film layer; S3, preparing a grafting monomer solution: dissolving a grafting monomer, an initiator, a catalyst, a ligand, and a lithium salt in a solvent to obtain a grafting monomer solution; S4, in-situ graft polymerization on the electrolyte surface: assembling the positive electrode sheet with the electrolyte membrane layer and the negative electrode sheet with the electrolyte membrane layer in step S2 into a battery cell by laminating; adding the grafted monomer solution in step S3 to the battery cell, pre-sealing, heating and curing, and obtaining a solid-state battery; In the step S3, the grafting monomer is dimethylaminoethyl methacrylate or polyethylene glycol methacrylate, the initiator is 2-bromoethyl isobutyrate, the catalyst is CuCl or CuBr, and the ligand is 1,1,4,7,10,10-hexamethyltriethylenetetramine.

2. The method for preparing a solid-state battery according to claim 1, characterized in that: In the step S1, the specific method for preparing the PVDF polymer electrolyte slurry is: adding lithium salt and PVDF polymer into solvent 1, stirring and mixing, and obtaining the PVDF polymer electrolyte slurry.

3. The method for preparing a solid-state battery according to claim 2, characterized in that: The PVDF polymer is one or more of PVDF, P(VDF-HFP), P(VDF-TrFE), P(VDF-CTFE), and P(VDF-TrFE-CTFE); the concentration of the PVDF polymer is 50-170 g / L; The lithium salt is one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, lithium dioxalatoborate, and lithium nitrate; the concentration of the lithium salt is 15-75 g / L; Solvent 1 is N-methylpyrrolidone, N,N - one or more of dimethylformamide and tetrahydrofuran.

4. The method for preparing a solid-state battery according to claim 1, characterized in that: In the step S2, The positive electrode sheet is one of a lithium cobalt oxide positive electrode sheet, a lithium manganese oxide positive electrode sheet, a lithium iron phosphate positive electrode sheet, and a ternary positive electrode sheet; The negative electrode plate is one of a carbon material negative electrode, a silicon-carbon negative electrode, and a metal lithium negative electrode.

5. The method for preparing a solid-state battery according to claim 1, characterized in that: In the step S2, The thickness of the electrolyte membrane layer on each surface of the positive electrode sheet and the negative electrode sheet is 10~30μm; When drying, first dry at room temperature for 6 to 24 hours, then dry at 60 to 90°C for 0.5 to 2 hours.

6. The method for preparing a solid-state battery according to claim 1, characterized in that: In the step S3, The concentration of the grafted monomer is 1.5~4 mol / L; the concentration of the initiator is 0.01~0.05 mol / L; the concentration of the catalyst is 0.01~0.05 mol / L; and the concentration of the ligand is 0.01~0.05 mol / L.

7. The method for preparing a solid-state battery according to claim 1, characterized in that: In the step S3, The lithium salt is one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, lithium dioxalatoborate, and lithium nitrate, and the concentration of the lithium salt is 25-100 g / L; The solvent is one of tetrahydrofuran, acetone and 1,3-bis(1,1,2,2-tetrafluoroethoxy)propane.

8. The method for preparing a solid-state battery according to claim 1, characterized in that: In the step S4, The ratio of the amount of grafted monomer solution added to the cell capacity is 1.5~2.5g / Ah.

9. The method for preparing a solid-state battery according to claim 1, characterized in that: In the step S4, the heating curing temperature is 50-70° C., and the heating curing time is 10-24 hours.

10. A solid-state battery, characterized in that: The method is prepared according to any one of claims 1 to 9.

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