An interface-free low-impedance high-safety all-solid-state battery and a preparation method thereof

Abstract

The application discloses a kind of interfaceless low impedance high safety all-solid-state battery and preparation method thereof.The application makes electrolyte mixed solution before polymerization uniformly permeate into the positive electrode, negative electrode and separator of battery cell by low-temperature uniform infiltration wetting, temperature is kept at 15~20 DEG C, then gradually improves temperature to make second mixed solution polymerization reaction, makes polymerization reaction uniformly by this heating mode, polymerization is uniform in in-situ polymerization process, battery interface impedance is low, battery consistency stability is good, first cycle efficiency is high.We make all-solid-state battery with unique interfaceless three-dimensional network structure, thereby improve first cycle efficiency and improve the overall electrochemical performance of battery.Finally, since using the component and equipment that polymerization has been common to form polymer, especially existing lithium ion battery production equipment, it is easy to industrialization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state batteries, in particular to a full-solid-state battery with no interface, low impedance and high safety and a preparation method thereof. BACKGROUND

[0002] Electrolyte is an important component of lithium-ion batteries. Currently, the industry mainly uses liquid electrolyte, but the liquid electrolyte needs to use adhesives and separators, thereby reducing the energy density of the liquid electrolyte battery as a whole. In addition, the liquid electrolyte, which is usually made of organic molecules, is flammable, reducing the safety of the battery. At low temperatures, the liquid electrolyte gradually freezes, reducing the ionic conductivity; while at higher temperatures, the liquid electrolyte evaporates and generates bubbles with high impedance.

[0003] Due to these limitations of liquid electrolyte, solid electrolyte is increasingly attracting the attention of researchers as a potential alternative. Compared with liquid electrolyte, solid electrolyte achieves higher battery energy density by reducing battery mass and increasing electrochemical window, is not flammable, is more stable within a temperature range, and does not leak under extreme temperature or pressure. However, existing solid-state battery technology is not mature enough to achieve industrialization. Existing preparation methods either are not optimized or produce solid-state batteries with high interface impedance between the produced electrodes and electrolytes (thus having poor rate and cycle performance).

[0004] Solid-state electrolyte is mainly prepared by in-situ polymerization, whereby monomer, lithium salt, cross-linking agent and initiator compounds are injected into the battery, and after applying heat, the electrolyte solidifies into a solid. Using such a method, due to the uneven dispersion of monomer, lithium salt, cross-linking agent and initiator compounds in the positive electrode, negative electrode and separator, in addition to the uneven temperature distribution in the battery, the in-situ polymerization reaction is not uniform, resulting in uneven solid electrolyte interface, so that the consistency and stability of the battery produced is poor, and the electrochemical performance is poor. The battery produced in this way has high internal resistance, which reduces the first cycle efficiency.

[0005] In addition to liquid injection and heating, there are other technologies that use in-situ polymerization. Some technologies can initialize in-situ polymerization before assembling the battery. This can be done by coating an electrolyte material on a membrane to form an electrolyte membrane, which can have different compounds on both sides of the membrane, and then sticking to the electrodes, which results in poor electrode-electrolyte interface contact and high impedance, ultimately reducing battery performance. To solve the above problems, one method is to mix the reaction monomer into the cathode and anode, and then inject the cross-linking agent and initiator for in-situ polymerization, however, this scheme still cannot solve the problem of uneven polymerization.

[0006] Considering the current lithium battery industry, such as existing production lines, equipment and supply chain, the in-situ polymerized liquid injection scheme is the simplest and most convenient method to prepare batteries, while also minimizing additional costs and promoting the development of solid-state batteries.

[0007] However, current research on in-situ polymerization focuses more on the theoretical structure of the material and the polymerization reaction, and less on the actual solid-state battery industrialization, such as liquid injection. There are few solutions to the problems that arise when using such methods, such as high interfacial impedance, uneven polymerization, poor battery consistency and stability, and low first cycle efficiency. SUMMARY

[0008] The present application is directed to the problem of high interfacial impedance, poor battery consistency and stability, and low first cycle efficiency caused by uneven polymerization during in-situ polymerization of solid-state batteries in the prior art, and provides a preparation method for a full solid-state battery with no interface, low impedance and high safety, as well as a full solid-state battery prepared thereby.

[0009] A preparation method for a full solid-state battery with no interface, low impedance and high safety, the full solid-state battery comprising a battery cell, the preparation method comprising the following steps:

[0010] (1) mixing a reaction monomer, a crosslinking agent and a lithium salt to obtain a first mixed solution, and reducing the temperature of the first mixed solution to 15-20°C;

[0011] (2) reducing the temperature of the initiator to 15-20°C, then adding the initiator to the first mixed solution after temperature reduction and mixing to obtain a second mixed solution;

[0012] (3) keeping the second mixed solution at 15-20°C and injecting it into the battery cell, and maintaining it at 15-20°C for a certain period of time to allow the second mixed solution to soak into the battery cell;

[0013] (4) gradually increasing the temperature in a gradual manner to cause the second mixed solution to undergo a polymerization reaction, and obtaining a full solid-state battery with a solid-state electrolyte.

[0014] Preferably, the reaction monomer is at least one of polyethylene glycol methyl ether methacrylate, polyethylene glycol dimethyl methacrylate, methacryloyloxypropyl-terminated polydimethylsiloxane, monomethacryloyloxypropyl-terminated polydimethylsiloxane, and poly(triethoxyvinylsilane). The reaction monomer is specially selected to produce a polymer that has both ionic conductivity and mechanical stability, and is also very common in the liquid lithium ion battery industry.

[0015] More preferably, the reaction monomer is composed of at least two different monomers, at least one of which is an amorphous, low glass transition temperature (Tg) reaction monomer, such as polyethylene glycol methyl ether methacrylate (POEM), polyethylene glycol dimethacrylate (PEGDMA). Preferably, the mass of such amorphous, low Tg reaction monomer can account for 20% to 50% of the total mass of the reaction monomer. By adding such an amorphous, low Tg reaction monomer, the ion transport efficiency of the battery can be improved to some extent, and the macroscopic surface can improve the capacity, internal resistance and other electrical properties of the battery.

[0016] Preferably, the crosslinking agent mainly functions to connect the long chains of the polymerization reaction to form a crosslinked network. The crosslinking agent is at least one of the following: polyethylene glycol diacrylate, trihydroxymethyl propane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, polyether multiacrylate.

[0017] The lithium salt mainly functions to provide ion transport carriers for the system. The lithium salt is at least one of the following: LiBF4, LiBF6, LiAF6, LiPF6, LiClO4, LiB(C6H5)4, LiAlCl4, LiBr, LiCF3O3, LiN(CF3O2)2, LiC(CF3OO2)3, LiN(O2C2F5)2, Li[B(O4C2)]2.

[0018] The initiator is used to initiate the polymerization reaction of the reaction monomer. The initiator is azobisdimethyl isobutyronitrile.

[0019] Preferably, 1 to 4 parts of initiator, 12 to 24 parts of lithium salt, and 20 to 40 parts of crosslinking agent are added per 100 parts of reaction monomer by mass.

[0020] After the liquid injection, the second mixed solution needs to be fully infiltrated into the battery. Preferably, in step (3), the infiltration time is not less than 48 hours. The longer the infiltration time, the more conducive to infiltration, but at the same time, it needs to be considered that the reaction monomer and initiator have been added in the second mixed solution at the same time, although the polymerization reaction can be slowed down at a lower temperature, but the polymerization reaction may still occur, so more preferably, in step (3), the infiltration time is 48 to 60 hours.

[0021] In the present application, when the battery after liquid injection is heated from low temperature to a higher polymerization temperature to promote the occurrence of polymerization reaction, the temperature field in the system will be inconsistent if the heating rate is too fast, and the polymerization reaction may not be uniformly polymerized at the same time, resulting in relatively low battery performance capacity and shortened cycle life. However, a longer heating time will affect the production efficiency, and the production energy consumption and cost will also be increased. Therefore, preferably, in step (4), the temperature is gradually increased at a heating rate of not more than 1℃ / h until 60-80℃ during the polymerization reaction, and the temperature is maintained at this temperature for not less than 24h. More preferably, the temperature is gradually increased at a heating rate of 0.5-1℃ / h until 60-80℃ during the polymerization reaction. Most preferably, the temperature is gradually increased at a heating rate of 1℃ / h until 60-80℃ during the polymerization reaction.

[0022] The liquid injection process can be repeated multiple times or completed at one time. Specifically, battery vacuuming and electrolyte injection are one cycle, and the entire liquid injection process is performed twice or more cycles, which can ensure that the electrolyte is in a negative pressure state during liquid injection, so that the electrolyte is more easily infiltrated into the electrode pores, improving the overall wettability and liquid injection efficiency. Preferably, in step (3), when the second mixed solution is injected into the battery at 15-20℃, the environmental dew point is controlled at -45℃ to -65℃, and the vacuum degree is controlled at -98kPa to -2kPa.

[0023] Preferably, after the polymerization reaction in step (4), the first formation and the first degassing are performed, and then the solid electrolyte is aged, and after the aging is completed, the second formation and the second degassing are performed.

[0024] The purpose of the first formation step is to complete the reaction between the electrolyte and the electrode and form a stable solid electrolyte interface. Preferably, the conditions for the first formation are: charging current 0.01C-0.5C, and charging time 30 minutes-360 minutes.

[0025] The purpose of the first degassing step is to collect and discharge the gas generated in the first formation. Preferably, the conditions for the first degassing are: -98kPa to -2kPa pressure for 1-20 times, each time for 1-20s.

[0026] The purpose of the second formation step is to further improve the formation of the electrode and electrolyte interface. Preferably, the conditions for the second formation are: charging current 0.01C-0.5C, and charging until the voltage reaches the rated voltage 4.2V.

[0027] The purpose of the second degassing step is to collect and discharge the gas generated in the second formation reaction. Preferably, the conditions for the second degassing are: -98kPa to -2kPa pressure for 1-20 times, each time for 1-20s.

[0028] The purpose of aging is to make the initial side reaction of the battery complete, form a stable and firm SEI film on the surface of the positive and negative electrode particles, and make the subsequent battery cycle stable.

[0029] The application further provides the full-solid-state battery prepared by the preparation method.

[0030] Compared with the prior art, the application solves the problems of uneven polymerization, high interface impedance, poor consistency stability of the battery and low first cycle efficiency in the in-situ polymerization process. Only one liquid injection is needed, and the electrolyte mixture before polymerization is uniformly infiltrated into the positive electrode, negative electrode and separator at a temperature of 15-20 DEG C through low-temperature uniform infiltration and wetting, and then the temperature is gradually increased to make the second mixture undergo polymerization reaction, so that the polymerization reaction is uniformly carried out through this temperature rising mode, the polymerization is uniform in the in-situ polymerization process, the interface impedance of the battery is low, the consistency stability of the battery is good, and the first cycle efficiency is high. We make the full-solid-state battery with a unique three-dimensional network structure without interface, thereby improving the first cycle efficiency and improving the overall electrochemical performance of the battery. Finally, since the components and equipment for polymerization are already common, especially the existing lithium ion battery production equipment, the application is easy to industrialize. DETAILED DESCRIPTION

[0031] The positive electrode sheet, negative electrode sheet and separator in the solid-state cylindrical battery prepared in the following examples are as follows:

[0032] 1. NCM811 electrode sheet was prepared as the positive electrode by using the conventional lithium ion battery preparation process, silicon-carbon electrode sheet was prepared as the negative electrode by using the conventional lithium ion battery preparation process, and the traditional high-porosity porous polyethylene separator with an aluminum oxide coating was cut into a suitable size.

[0033] Preparation of the positive electrode:

[0034] The positive electrode slurry was coated on the positive electrode current collector aluminum foil, and dried in a vacuum drying box at 70-110 DEG C for 10 hours, then the electrode was compacted by a roller compactor, and then the composite positive electrode sheet was obtained through slitting and punching processes.

[0035] The active component in the positive electrode slurry is NCM811, and the structural formula is: LiNi 0.8 Co 0.1 Mn 0.1 O2, and the material is a compound with a complex structure, and the surface is coated with a uniform solid-state electrolyte (Li 1.4 Al 0.4 Ti 1.6(PO4)3, hereinafter referred to as LATP) coating layer, with a capacity of up to 210 mAh / g (0.5C / 0.5C charge-discharge).

[0036] The active component in the positive electrode slurry accounts for 96.5% of the mass percentage of the positive electrode slurry, and the mass ratio of NCM811, conductive agent and binder is 96.5:1.5:2, wherein the conductive agent is SP-acetylene black, and the binder is PVDF5130.

[0037] Preparation of the negative electrode:

[0038] The negative electrode slurry is coated on the negative electrode current collector copper foil, and dried in a vacuum drying oven at 70-110°C for 10h, then the electrode is compacted by a roller press, and then cut and punched to obtain the negative electrode sheet.

[0039] The active component in the negative electrode slurry is SiO / graphite, with a capacity of up to 450 mAh / g (0.5C / 0.5C charge-discharge).

[0040] The active component in the negative electrode slurry accounts for 96:1.5:2.5 of the mass percentage of the negative electrode slurry, and the mass ratio of SiO / graphite, conductive agent and binder is 96:1.5:2.5, wherein the conductive agent is SP-acetylene black, and the binder is CMC+SBR.

[0041] Example 1

[0042] A preparation method of a solid-state cylindrical battery with no interface and low internal resistance safety is as follows:

[0043] 1. Prepare the positive electrode sheet, negative electrode sheet and separator respectively.

[0044] 2. Wind, assemble and dry the positive and negative electrode sheets and the separator prepared in step 1 to prepare a dry battery without liquid injection.

[0045] 3. Mix 6.25g of polyethylene glycol methyl ether methacrylate (POEM) monomer, 6.25g of methacryloxypropyl-terminated polydimethylsiloxane (PDMD) monomer, 1.5g of LiPF6 and 2.5g of polyether polyacrylate crosslinking agent to prepare a primary electrolyte, and stir the mixture for 4 hours. Reduce the temperature to 15°C, then add 0.125g of initiator azobisisobutyronitrile, and continue to stir the mixture for another 4 hours.

[0046] 4. Inject the electrolyte prepared in step 3 into the dry battery prepared in step 2. The dew point of the injection environment is controlled at -60°C, and the vacuum degree is -90kPa. The battery is soaked for 60h at a temperature of 15°C, and then slowly heated to 60°C at a speed of 1°C / h, and kept for 24h, so that the reaction proceeds uniformly, and the polymerization in the in-situ polymerization process is uniform.

[0047] 5. The polymerized battery prepared in step 4 was subjected to formation and primary degassing. The formation charging current was 0.01C, and the charging time was 360 minutes. The primary degassing vacuum was -98 kPa, and the exhaust was performed once, with an exhaust time of 20 s.

[0048] 6. The battery cell prepared in step 5 was subjected to room temperature aging, secondary formation, secondary degassing, and capacity grading to complete the preparation of the solid-state battery. The aging temperature was 45°C, and the time was 120 h. The secondary formation charging current was 0.01C, and the voltage was charged to the rated voltage of 4.2V. The secondary degassing vacuum was -2 kPa, and the exhaust was performed 20 times, with an exhaust time of 20 s each time.

[0049] 7. The prepared solid-state battery was subjected to electrochemical performance testing to measure the capacity, internal resistance, life cycle, rate capability, and high-temperature storage performance. The battery also underwent safety performance testing, such as tests involving needle puncture and overcharging. No explosion or combustion was observed.

[0050] Example 2

[0051] A method for preparing a solid-state square battery with no interface, low internal resistance, and high safety is as follows:

[0052] 1. Prepare a positive electrode sheet, a negative electrode sheet, and a separator, respectively.

[0053] 2. Wind, hot-press, assemble, and dry the positive and negative electrode sheets and the separator prepared in step 1 to prepare a dry battery without liquid injection.

[0054] 3. Mix 5 g of polyethylene glycol methyl ether methacrylate (POEM) monomer, 5 g of methacryloxypropyl-terminated polydimethylsiloxane (PDMD) monomer, 2.4 g of LiPF6, and 4 g of polyether polyacrylate crosslinking agent to prepare a primary electrolyte, and stir the mixture for 4 hours. Reduce the temperature to 20°C, add 0.2 g of initiator azobisisobutyronitrile, and continue stirring the mixture for another 4 hours.

[0055] 4. Inject the electrolyte prepared in step 3 into the dry battery prepared in step 2. The dew point of the injection environment is controlled at -60°C, and the vacuum is -90 kPa. The battery is soaked at a temperature of 20°C for 48 h, and then slowly heated to 60°C at a rate of 1°C / h, and soaked for 24 h to allow the polymerization reaction to proceed uniformly.

[0056] 5. The battery cell after in-situ polymerization in step 4 was subjected to formation and primary degassing. The formation charging current was 0.5C, and the charging time was 30 minutes. The primary degassing vacuum was -2 kPa, and the exhaust was performed 20 times, with an exhaust time of 20 s each time.

[0057] 6. The cell prepared in step 5 was aged at room temperature, reformed, re- degassed, and capacity graded to complete the preparation of the solid-state battery. The aging conditions were: temperature 80 °C, time 12 h. The reformation conditions were: charge current 0.5 C, and the voltage was charged to 4.2 V, the rated voltage. The re-degassing vacuum was -98 kPa, and the exhaust time was 1 s.

[0058] 7. The prepared solid-state battery was tested for electrochemical performance to measure capacity, internal resistance, cycle life, rate capability, and high-temperature storage performance. The battery also underwent safety performance tests, such as tests involving needle pricking and overcharging. No explosion or combustion was observed.

[0059] Example 3

[0060] The overall method was the same as in Example 1, except that in step 3, the reaction monomer was poly(triethoxylvinylsilane), with an added mass of 6.25 g; the lithium salt was LiCF3O3, with an added mass of 1.5 g; and a crosslinking agent was also added, which was pentaerythritol tetraacrylate, with an added mass of 1.25 g. The mixture was stirred for 4 hours, and the temperature was reduced to 15 °C, after which 0.25 g of the initiator azobisisobutyronitrile was added. The mixture was stirred for another 4 hours. In step 4, the battery was soaked at a temperature of 15 °C for 48 h, and then slowly warmed to 80 °C at a rate of 1 °C / h, and held at that temperature for 24 h, to allow the polymerization reaction to proceed uniformly.

[0061] Example 4

[0062] The overall method was the same as in Example 1, except that in step 3, the reaction monomer was poly(ethylene glycol dimethyl methacrylate), with an added mass of 6.25 g; the lithium salt was LiBF4, with an added mass of 1.5 g; and a crosslinking agent was also added, which was poly(ethylene glycol diacrylate), with an added mass of 2.5 g. The mixture was stirred for 4 hours, and the temperature was reduced to 15 °C, after which 0.125 g of the initiator azobisisobutyronitrile was added. The mixture was stirred for another 4 hours. In step 4, the battery was soaked at a temperature of 20 °C for 48 h, and then slowly warmed to 70 °C at a rate of 1 °C / h, and held at that temperature for 24 h, to allow the polymerization reaction to proceed uniformly.

[0063] Example 5

[0064] The overall method was the same as in Example 1, except that in step 4, after the injection, the battery was soaked at a temperature of 10 °C for 60 h, and then slowly warmed to 60 °C at a rate of 1 °C / h, and held at that temperature for 24 h. Because the soaking temperature was too low, the flowability of the electrolyte was reduced, which could cause incomplete soaking, and the battery capacity was relatively low.

[0065] Example 6

[0066] The overall method is the same as Example 1, except that in Step 4, after injection, the battery is controlled to soak at a temperature of 25°C for 60 h, and then slowly heated to 60°C at a rate of 1°C / h, and soaked for 24 h. Due to the excessively high temperature soaking, part of the polymerization reaction may occur in advance, and the polymerization may not be uniformly polymerized in the in-situ polymerization process, and the corresponding battery has a low capacity and a short cycle life.

[0067] Example 7

[0068] The overall method is the same as Example 1, except that in Step 4, after injection, the battery is controlled to soak at a temperature of 15°C for 60 h, and then slowly heated to 60°C at a rate of 2°C / h, and soaked for 24 h. The excessively fast heating rate leads to an inconsistent temperature field in the system, and the polymerization reaction may not be uniformly polymerized at the same time, and the corresponding battery has a low capacity and a short cycle life.

[0069] Example 8

[0070] The overall method is the same as Example 1, except that in Step 4, after injection, the battery is controlled to soak at a temperature of 15°C for 60 h, and then slowly heated to 60°C at a rate of 0.5°C / h, and soaked for 24 h. The reaction is uniformly carried out, and the polymerization is uniformly carried out in the in-situ polymerization process. However, the heating time is relatively long, which has an impact on the production efficiency, and the production energy consumption and cost are also increased.

[0071] Example 9

[0072] The overall method is the same as Example 1, except that in Step 4, after injection, the battery is controlled to soak at a temperature of 15°C for 60 h, and then directly placed in a 60°C temperature box and soaked for 24 h. The excessively fast heating rate leads to an inconsistent temperature field in the system, and the polymerization reaction may not be uniformly polymerized at the same time, and the corresponding battery has a low capacity and a short cycle life.

[0073] Example 10

[0074] The overall method is the same as Example 1, except that in Step 4, after injection, the battery is controlled to soak at room temperature for 60 h, and then slowly heated to 60°C at a rate of 1°C / h, and soaked for 24 h. Similar to Example 6, due to the excessively high soaking temperature and the exothermic process of the polymerization reaction, part of the polymerization reaction may occur in advance, and the polymerization may not be uniformly polymerized in the in-situ polymerization process, and the corresponding battery has a low capacity and a short cycle life.

[0075] Detection Example 1

[0076] The prepared solid-state batteries were subjected to electrochemical performance tests to measure capacity, internal resistance, cycle life, rate capability, and high-temperature storage performance. The batteries were also subjected to safety performance tests, such as tests involving needle pricking and overcharging. No explosion or combustion was observed. The experimental results are shown in Table 1.

[0077] Table 1

[0078]

[0079] Result analysis and conclusion:

[0080] Comparing Example 3 with Example 1, it can be seen that the use of amorphous reaction monomers with low glass transition temperature (Tg) such as polyethylene glycol methyl ether methacrylate (POEM) and polyethylene glycol dimethacrylate (PEGDMA) in the present application can improve the ion transport efficiency of the battery to some extent, macroscopically manifested as improved battery electrical properties such as capacity and internal resistance, and confirmed by experimental results.

[0081] Comparing Example 5 with Example 1, it can be seen that due to the excessively low infiltration temperature, the electrolyte infiltration fluidity is reduced, which may cause incomplete infiltration, and the corresponding battery electrical performance capacity is relatively low.

[0082] Comparing Example 6 and Example 10 with Example 1, it can be seen that due to the excessively high temperature, part of the polymerization reaction may occur prematurely, and the in-situ polymerization process cannot be uniformly polymerized, which results in relatively low battery electrical performance capacity and shortened cycle life.

[0083] Comparing Example 7 and Example 9 with Example 1, it can be seen that the excessively fast heating rate causes inconsistent temperature field in the system, and the polymerization reaction may not uniformly polymerize at the same time, which results in relatively low battery electrical performance capacity and shortened cycle life. Comparing Example 8 with Example 1, it can be seen that the longer heating time has an impact on production efficiency, and the production energy consumption and cost are also increased.

[0084] As can be seen from the results of the examples, the use of the low-temperature method for uniform penetration and wetting, the control of the temperature at 15-20°C to make the electrolyte mixture before polymerization uniformly penetrate into the positive electrode, negative electrode, and separator of the battery cell, and then the gradual increase of the temperature to make the second mixture undergo polymerization reaction, through this heating method, the polymerization reaction is uniformly carried out, the in-situ polymerization process is uniformly polymerized, the battery interface impedance is low, the battery is consistent and stable, and the first cycle efficiency is high.

Claims

1. A method for fabricating an interface-free, low-impedance, high-safety all-solid-state battery, the all-solid-state battery comprising a cell, characterized in that, The preparation method includes the following steps: (1) Mix the reactant, crosslinking agent and lithium salt to obtain a first mixture, and lower the temperature of the first mixture to 15℃~20℃; (2) The temperature of the initiator is also lowered to 15℃~20℃, and then the initiator is added to the first mixture after cooling and mixed to obtain the second mixture; (3) The second mixture is injected into the cell at 15℃~20℃ and maintained at 15℃~20℃ for a certain period of time to allow the second mixture to wet the cell; (4) Gradually increase the temperature at a rate not exceeding 1℃ / h until it reaches 60~80℃, and maintain this temperature for at least 24h to obtain an all-solid-state battery with solid electrolyte. The reactant monomer is at least one of the following: polyethylene glycol methyl ether methacrylate, polyethylene glycol dimethacrylate, methacryloyloxypropyl-terminated polydimethylsiloxane, monomethacryloyloxypropyl-terminated polydimethylsiloxane, and poly(triethoxyvinylsilane). The crosslinking agent is at least one of the following: polyethylene glycol diacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, and polyether polyacrylate. The initiator is azobisisobutyronitrile (AIBN).

2. The preparation method according to claim 1, characterized in that, The lithium salt is at least one of the following: LiBF4, LiBF6, LiPF6, LiClO4, LiB(C6H5)4, LiAlCl4, or LiBr.

3. The preparation method according to claim 1, characterized in that, By mass, for every 100 parts of reactant monomer, add 1-4 parts of initiator, 12-24 parts of lithium salt, and 20-40 parts of crosslinking agent.

4. The preparation method according to claim 1, characterized in that, In step (3), the soaking time shall not be less than 48 hours.

5. The preparation method according to claim 4, characterized in that, In step (3), the soaking time is 48~60h.

6. The preparation method according to claim 1, characterized in that, In step (3), when the second mixture is injected into the cell at 15℃~20℃, the ambient dew point is controlled between -45℃ and -65℃, and the vacuum degree is controlled between -98kPa and -2kPa.

7. The preparation method according to claim 1, characterized in that, After the polymerization reaction in step (4), the first formation and the first degassing are carried out, followed by the aging of the solid electrolyte. After the aging is completed, the second formation and the second degassing are carried out.

8. The preparation method according to claim 7, characterized in that, The conditions for the first formation are: charging current 0.01C-0.5C, charging time 30 minutes to 360 minutes; The conditions for the second formation are: charging current of 0.01C~0.5C, charging until the voltage reaches the rated voltage of 4.2V; The conditions for the first and second degassing were: 1 to 20 cycles under a pressure of -98 kPa to -2 kPa, each cycle lasting 1 to 20 seconds; The aging conditions are: temperature 45~80℃, time 12~120h.

9. An interface-free, low-impedance, high-safety all-solid-state battery prepared by any of the preparation methods described in claims 1 to 8.

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