Solid-state battery and method of manufacturing the same

Abstract

The present application relates to a preparation method of a solid-state battery, comprising the following steps: a step of mixing a polymer monomer, a crosslinking agent, an electrolyte salt and an initiator to prepare a precursor solution under a vacuum or a protective gas atmosphere; a step of injecting the precursor solution into a porous support material between a positive electrode and a negative electrode and assembling the battery; and a step of simultaneously curing the precursor solution contacting the negative electrode side at a high temperature and curing the precursor solution contacting the positive electrode side at a low temperature. The solid-state battery prepared by the preparation method has better interface stability and a wider electrochemical window, and can effectively improve the comprehensive performance of the solid-state battery, such as cycle performance and rate performance.

Description

Technical Field

[0001] This application relates to the field of all-solid-state battery technology, and in particular to a solid-state battery and a method for preparing the solid-state battery. Background Technology

[0002] This section provides background information relevant to this application, which does not necessarily constitute prior art.

[0003] To address the issues of poor solid-solid interface contact and high impedance between the solid electrolyte and electrodes in solid-state lithium batteries (ASSLBs), existing technical solutions include in-situ polymerization. This technology involves injecting a solid electrolyte precursor solution containing initiators, polymer monomers, lithium salts, and additives into the assembled battery (positive electrode / separator / negative electrode) using the electrolyte injection method common in liquid batteries. Under the action of the initiator and at a certain temperature, the polymer monomers in the precursor solution gradually polymerize and solidify to form a solid electrolyte. Because the liquid precursor solution first wets the electrode interfaces on both sides before solidifying, it largely preserves the boundary morphology, thus significantly improving the interfacial contact between the solid electrolyte and electrodes.

[0004] In in-situ polymerization technology, polymerization temperature is a crucial indicator. Polymer monomers can polymerize within a certain temperature range, and the specific temperature selection depends on factors such as the type of polymer monomer and the type of initiator. Existing polymers used in solid electrolytes, such as polymethyl methacrylate (PMMA), polyethylene glycol methyl ether acrylate (PEGMEA), polyethylene glycol diacrylate (PEGDA), and poly(1,3-dioxane) (PDOL), generally have polymerization temperatures ranging from approximately 60°C to approximately 80°C. During the thermosetting of the solid electrolyte precursor solution, existing in-situ polymerization techniques involve heating the precursor solution at a uniform temperature (e.g., 60°C or 80°C) for a certain period to induce cross-linking polymerization of the polymer monomers, forming a homogeneous solid electrolyte.

[0005] However, since the solid electrolyte prepared by the "uniform thermosetting" process of in-situ polymerization technology is uniform in microstructure and macro performance, this leads to an irreconcilable contradiction between "mechanical-electrochemical performance" in solid batteries: (1) Contradiction 1 (dendritic prevention vs. interface contact): The negative electrode side (especially the lithium metal negative electrode) requires extremely high mechanical modulus to physically block the penetration of lithium dendrites, while the positive electrode side needs the electrolyte to have a low modulus and good flexibility to maintain close contact in order to adapt to the volume expansion (breathing effect) of active particles during charging and discharging. Homogeneous electrolytes cannot meet these two requirements at the same time; (2) Contradiction 2 (strength vs. conductivity): Although increasing the crosslinking density can improve the strength (dendritic prevention), it will significantly limit the mobility of polymer chain segments, resulting in a significant decrease in lithium ion migration number and ionic conductivity.

[0006] To address the above problems, existing technical solutions include: (1) using multilayer coating or mechanically stacking electrolyte membranes with different properties. For example, the technical solution disclosed in Chinese Patent CN202510665533X (A composite interface layer and its preparation method, all-solid-state battery) uses a stacked composite interface layer. However, this technical solution increases the interface impedance due to the introduction of an additional artificial physical interface; (2) using a multiple curing process. For example, the technical solution disclosed in Chinese Patent CN2021113314971 (Solid electrolyte, its preparation method and solid secondary battery containing it) is a two-stage curing process (the first curing is carried out at room temperature, and then the second curing is carried out under heating conditions). However, this technical solution is complex (it requires strict control of the liquid volume ratio of room temperature polymerizable polymer monomers to high temperature polymerizable polymer monomers, temperature and curing time), and is not suitable for in-situ curing processes. Summary of the Invention

[0007] This invention aims to address the limitations of existing in-situ polymerization techniques and improve the overall performance of the prepared solid-state batteries. The method for preparing solid-state batteries based on in-situ polymerization technology provided by this invention enables the one-step preparation of solid electrolytes without multi-step coating. This method utilizes asymmetric thermal field control to regulate polymerization kinetics, allowing the prepared solid electrolytes to simultaneously achieve: (1) Negative electrode side: A high cross-linking density and high Young's modulus layer is formed in situ, which effectively inhibits the growth of lithium dendrites; (2) Positive electrode side and bulk phase: A highly conductive layer with low cross-linking density and high chain segment flexibility is formed in situ to ensure excellent interface wetting and ion transport; (3) Gradient transition: Achieve a smooth chemical transition from hard to soft and eliminate interfacial resistance.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing solid-state batteries based on in-situ polymerization technology includes the following steps: The process of preparing a precursor solution by mixing polymerizable monomers, crosslinking agents, electrolyte salts and initiators under vacuum or protective gas atmosphere; The process of injecting the precursor solution into the porous support material between the positive and negative electrodes and assembling the battery; Simultaneously, the process involves high-temperature curing of the precursor solution in contact with the negative electrode side and low-temperature curing of the precursor solution in contact with the positive electrode side.

[0009] The temperature of the high-temperature curing is T. high The temperature for the low-temperature curing is T. low Simultaneously satisfying: 130℃≥T high ≥80℃, 70℃≥T low ≥40℃, temperature difference T high -T low ≥20℃. Curing time is 1-8 hours, depending on monomer activity. The precursor solution in contact with the negative electrode decomposes rapidly at high temperatures, causing a sudden surge in free radical concentration and a rapid, highly dense cross-linking reaction, forming a hard "anti-dendritic shell." Conversely, the precursor solution in contact with the positive electrode cures at low temperatures, resulting in a stable curing reaction and allowing sufficient time for polymer chains to expand and align, forming a "highly conductive core layer" with low cross-linking degree and high free volume. The temperature difference between high-temperature and low-temperature curing allows for the application of an asymmetric thermal field (temperature gradient) along the battery thickness direction during the curing process.

[0010] The polymerizable monomers include high-temperature polymerizable monomers. It should be noted that the high-temperature polymerizable monomers refer to monomers that can polymerize under heating conditions, preferably at a temperature greater than or equal to 40°C and less than or equal to 130°C, through an initiator and thermal initiation, and that the high-temperature polymerizable monomers are liquid at room temperature. For example, the high-temperature polymerizable monomers may be selected from one or more of the following: methyl methacrylate, ethyl methacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, β-propiolactone, ε-caprolactone, vinylene carbonate, ethylene ethylene carbonate, trimethylene carbonate, acrylic anhydride, caprolactam, acrylamide, ethyleneimine, acrylonitrile, trioxymethylene, α-methylstyrene, 1,3,2-dioxopentane, methylpropylene phosphate, triallyl phosphate, and macromonomers with a weight-average molecular weight (MW) less than or equal to 2000. For example, the macromonomer may be selected from one or more of polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethacrylate (PEGDMA), polyethylene glycol methyl ether acrylate, polyethylene glycol methyl ether methacrylate, polyethylene glycol dimethyl ether, and polyethylene glycol diglycidyl ether. Preferably, the polymerizable monomer is at least one of acrylates, olefin double bond monomers (such as VC, VEC, etc.), acrylamide monomers (such as methylenebisacrylamide, N-tert-butylacrylamide, etc.), and siloxane monomers (such as allyltrimethylsilane, diallyldimethylsilane, etc.). More preferably, the polymerizable monomer is an acrylate. Based on the total mass of the polymerizable monomer, crosslinking agent, and initiator, the content of the polymerizable monomer is preferably from 68 wt% to 94.9 wt%.

[0011] The crosslinking agent is used to provide mechanical strength. For example, the crosslinking agent may be selected from at least one of trimethylolpropane triacrylate (TMPTA), ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate (PETEA), ethoxylated bisphenol A diacrylate (BPA-DA), and trimethylolpropane trimethacrylate. Based on the total mass of the polymerizable monomer, crosslinking agent, and initiator, the content of the crosslinking agent is preferably from 5 wt% to 30 wt%.

[0012] The electrolyte salt can be selected according to the type of solid-state battery. For example, the electrolyte salt can be selected from lithium salts or sodium salts. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium dioxalate borate, lithium difluorooxalate borate (LiODFB), and lithium difluorophosphate; the sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium dioxalate borate, sodium difluorooxalate borate, and sodium difluorophosphate. If the electrolyte salt is a lithium salt, preferably, the concentration of the lithium salt in the precursor solution satisfies: [EO]:[Li + The molar ratio is between 10:1 and 20:1.

[0013] The initiator is selected from benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), dimethyl azobisisobutyrate, lauroyl peroxide, diisopropyl peroxide, dicyclohexyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoyl, tert-butyl peroxyvalerate, methyl ethyl ketone peroxide, cyclohexanone peroxide, di-tert-butyl peroxide, dicumyl peroxide, cumene peroxide, cumene hydrogen peroxide, and tert-butyl peroxide. The initiator comprises at least one of the following: hydrogen sulfide, potassium tert-butoxide, lithium tert-butoxide, aluminum triisopropoxide, boron trifluoride diethyl ether, boron trifluoride butyl ether, phosphorus pentafluoride, aluminum trifluoride, aluminum trichloride, aluminum trifluoromethanesulfonate, silver perchlorate, bismuth trichloride, stannous octoate, stannous tetrachloride, zinc dichloride, titanium tetrachloride, titanium tetrabromide, beryllium dichloride, ferric trichloride, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalate borate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorooxalate borate, lithium powder, and sodium powder. The initiator content in the precursor solution should not be excessive; otherwise, it will not disperse well, leading to uneven curing and excessively rapid curing, affecting controllability. Based on the total mass of the polymerizable monomer, crosslinking agent, and initiator, the initiator content is preferably from 0.1 wt% to 2 wt%.

[0014] In one or more embodiments, without affecting the technical effect of the present invention, the precursor solution may be supplemented with functionalized additives, such as fillers, as needed. For example, the filler may be selected from at least one of alumina (Al2O3), silicon dioxide, titanium dioxide, lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate, and sodium zirconium phosphate silicate. The amount of filler added to the precursor solution should not be too small; otherwise, it will be difficult to form a continuous fast ion transport pathway in the solidified electrolyte, resulting in a minimal increase in ionic conductivity. Similarly, the amount of filler added should not be too large; otherwise, it will easily aggregate in the solid electrolyte, destroying the already formed fast ion transport pathway. Based on the total mass of the precursor solution, the amount of initiator added is preferably 1 wt% to 20 wt%.

[0015] The selection of the positive and negative electrodes varies depending on the type of solid-state battery. They can be either lithium-ion or sodium-ion batteries. For example, when the solid-state battery is a lithium-ion battery, its positive electrode active material can be selected from at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, ternary nickel cobalt manganese, and ternary nickel cobalt aluminum; its negative electrode active material can be selected from at least one of metallic lithium, lithium alloy, graphite, hard carbon, silicon carbide, metallic tin, tin dioxide, and lithium titanate. When the solid-state battery is a sodium-ion battery, its positive electrode active material can be selected from at least one of sodium vanadium phosphate, sodium fluorophosphate, sodium manganate, sodium iron manganate, ternary nickel iron manganese, and ternary cobalt iron manganese; its negative electrode active material can be selected from at least one of metallic sodium, sodium alloy, graphite, hard carbon, metallic tin, tin dioxide, lithium titanate, and sodium titanate.

[0016] One method involves injecting the precursor solution into the porous support material between the positive and negative electrodes using the liquid injection method employed in the production of liquid lithium batteries. In one or more embodiments, after injection, the material is left to stand in a vacuum and at room temperature for 1-4 hours to ensure that the pores of the positive and negative electrodes are fully wetted by the precursor solution.

[0017] The battery assembly can adopt existing solid-state battery assembly technology, preferably, the assembly is carried out under conditions where the water and oxygen content are both below 0.1 ppm.

[0018] The porous support material can be any membrane used in the preparation of solid electrolytes. For example, the porous support material is selected from at least one of polyolefin membranes, polyolefin membranes, glass fiber, cellulose nonwoven membranes, polyvinylidene fluoride membranes, polyvinylidene fluoride-hexafluoropropylene membranes, polyimide membranes, and polyethylene terephthalate membranes.

[0019] The solid-state battery prepared by the method provided in this invention includes positive and negative electrodes and a solid electrolyte disposed between the positive and negative electrodes. The solid-state battery satisfies the following condition: the crosslinking density (or Young's modulus) of its solid electrolyte exhibits a gradient distribution in the thickness direction, and the crosslinking density of the solid electrolyte near the negative electrode is significantly higher than that near the positive electrode. The solid-state battery is a lithium-ion secondary battery, a lithium metal secondary battery, a sodium-ion secondary battery, or a sodium metal secondary battery.

[0020] The method for preparing solid-state batteries based on in-situ polymerization technology provided by this invention employs an asymmetric thermal field-induced in-situ polymerization process. It utilizes the polymerization reaction rate constant... k The temperature sensitivity (Arrhenius relation) allows for the application of temperature differences along the thickness of the solid-state battery to control the crosslinking reaction rate in different regions, thereby constructing a gradient network structure. The gradient formation mechanism is based on the Arrhenius equation. k = A*exp(- E a / RT The high-temperature curing on the negative electrode side affects the polymerization rate constant at that location. k The temperature difference is much greater than that on the positive electrode side. Under thermal conduction, a continuous temperature field forms inside the solid-state battery, leading to a continuous gradient distribution of the cross-linking density. Ultimately, the modulus of the solid electrolyte after curing monotonically decreases from the negative electrode to the positive electrode. Compared to high-temperature polymerization using "uniform thermosetting," the preparation method provided by this invention offers better interfacial stability and a wider electrochemical window, effectively improving the overall performance of solid-state batteries, including cycle life and rate capability. It is applicable to various secondary ion batteries such as lithium-ion batteries, lithium metal batteries, sodium-ion batteries, and sodium metal batteries.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) The method for preparing solid-state batteries based on in-situ polymerization technology provided by the present invention perfectly solves the contradiction between "mechanical and electrical conductivity". The gradient solid electrolyte prepared by the present invention can reach the GPa level on the negative electrode side (anti-dendrying), while the bulk phase and positive electrode side maintain high flexibility and high ionic conductivity (excellent electrochemical performance). The overall performance is significantly better than that of existing homogeneous solid electrolytes. (2) Excellent interface compatibility: The gradient structure is naturally connected by chemical bonds, without physical layering, which eliminates the defects of traditional stacked structures such as easy peeling and high interface impedance. (3) Simple process and easy to mass-produce: Only the heating method during curing needs to be changed (from constant temperature to gradient temperature control), without adding a complicated coating process or replacing the existing liquid injection equipment, and it is highly compatible with the existing lithium battery production line; (4) Wide applicability: This method is applicable to a variety of temperature-sensitive chemical systems, such as free radical polymerization, condensation polymerization, and addition polymerization.

[0022] The following description is based on specific embodiments. Detailed Implementation

[0023] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0024] It should be noted that the raw material components described in the embodiments of the present invention are all commercially available products, the separator model described is Celgard 2500 (25μm PP single layer), and the soft-pack all-solid-state battery described uses aluminum-plastic film as the battery shell material. The specifications of the soft-pack battery obtained after encapsulation are: thickness 5mm × width 80mm × length 120mm (excluding tabs).

[0025] [Example 1] This embodiment provides a Li || LFP soft-pack all-solid-state battery, which is prepared through the following steps: Step S1: Under inert gas protection, the polymerizable monomer, crosslinking agent, electrolyte salt and initiator are mixed and homogenized to obtain a precursor solution; Step S2: Following the liquid lithium battery assembly method, in an argon-protected glove box, place the separator between the LiFePO4 positive electrode and the lithium metal negative electrode, inject the precursor solution, and then let it stand in a vacuum environment for 48 hours to ensure that the electrode pores are fully wetted. Then, use aluminum film encapsulation technology to encapsulate the soft pack battery. Step S3: The packaged battery is placed in a dual-temperature-controlled hot press with independent temperature control on both sides for asymmetric thermal curing. Specifically, the dual-temperature-controlled hot press simultaneously heat-cures the precursor solution in contact with the lithium anode side and the precursor solution in contact with the cathode side. The heat curing temperature on the lithium anode side (i.e., T...) high The temperature is set to 110℃, and the thermosetting temperature on the positive electrode side (i.e., T) is... low The temperature was set at 60℃, the pressure was maintained at 0.5MPa, the reaction was carried out for 3 hours, and finally the mixture was naturally cooled to room temperature to obtain a Li ||LFP soft-pack all-solid-state battery.

[0026] In this embodiment, the polymerizable monomer is polyethylene glycol diacrylate (PEGDA), the crosslinking agent is trimethylolpropane triacrylate (TMPTA), the initiator is benzoyl peroxide (BPO), and the electrolyte salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Based on the total mass of the polymerizable monomer, crosslinking agent, and initiator, the content of the polymerizable monomer is 80 wt%, the content of the crosslinking agent is 19.5 wt%, and the content of the initiator is 0.5 wt%. The amount of electrolyte salt added satisfies: [EO]:[Li + The molar ratio is 16:1.

[0027] [Example 2] This embodiment provides a Li || LFP soft-pack all-solid-state battery, which is prepared through the following steps: Step S1: Under inert gas protection, the polymerizable monomer, crosslinking agent, electrolyte salt and initiator are mixed and homogenized to obtain a precursor solution; Step S2: Following the liquid lithium battery assembly method, in an argon-protected glove box, place the separator between the LiFePO4 positive electrode and the lithium metal negative electrode, inject the precursor solution, and then let it stand in a vacuum environment for 48 hours to ensure that the electrode pores are fully wetted. Then, use aluminum film encapsulation technology to encapsulate the soft pack battery. Step S3: The packaged battery is placed in a dual-temperature-controlled hot press with independent temperature control on both sides for asymmetric thermal curing. Specifically, the dual-temperature-controlled hot press simultaneously heat-cures the precursor solution in contact with the lithium anode side and the precursor solution in contact with the cathode side. The heat curing temperature on the lithium anode side (i.e., T...) high The temperature is set to 80℃, which is the thermosetting temperature on the positive electrode side (i.e., T). low The temperature was set at 40℃, the pressure was maintained at 0.5MPa, the reaction was carried out for 3 hours, and finally the mixture was naturally cooled to room temperature to obtain a Li ||LFP soft-pack all-solid-state battery.

[0028] In this embodiment, the polymerizable monomer is polyethylene glycol dimethacrylate (PEGDMA), the crosslinking agent is pentaerythritol tetraacrylate (PETEA), the initiator is azobisisobutyronitrile (AIBN), and the electrolyte salt is lithium bisfluorosulfonyl imide (LiFSI). Based on the total mass of the polymerizable monomer, crosslinking agent, and initiator, the content of the polymerizable monomer is 68 wt%, the content of the crosslinking agent is 30 wt%, and the content of the initiator is 2 wt%. The amount of electrolyte salt added satisfies: [EO]:[Li + The molar ratio is 10:1.

[0029] [Example 3] This embodiment provides a Li || LFP soft-pack all-solid-state battery, which is prepared through the following steps: Step S1: Under inert gas protection, the polymerizable monomer, crosslinking agent, electrolyte salt and initiator are mixed and homogenized to obtain a precursor solution; Step S2: Following the liquid lithium battery assembly method, in an argon-protected glove box, place the separator between the LiFePO4 positive electrode and the lithium metal negative electrode, inject the precursor solution, and then let it stand in a vacuum environment for 48 hours to ensure that the electrode pores are fully wetted. Then, use aluminum film encapsulation technology to encapsulate the soft pack battery. Step S3: The packaged battery is placed in a dual-temperature-controlled hot press with independent temperature control on both sides for asymmetric thermal curing. Specifically, the dual-temperature-controlled hot press simultaneously heat-cures the precursor solution in contact with the lithium anode side and the precursor solution in contact with the cathode side. The heat curing temperature on the lithium anode side (i.e., T...) high The temperature is set to 130℃, which is the thermosetting temperature on the positive electrode side (i.e., T). low The temperature was set at 70°C, the pressure was maintained at 0.5 MPa, the reaction was carried out for 3 hours, and finally the mixture was naturally cooled to room temperature to obtain a Li ||LFP soft-pack all-solid-state battery.

[0030] In this embodiment, the polymerizable monomer is polyethylene glycol methyl ether methacrylate, the crosslinking agent is ethoxylated bisphenol A diacrylate (BPA-DA), the initiator is azobisisoheptanenitrile (ABVN), and the electrolyte salt is lithium difluorooxalate borate (LiODFB). Based on the total mass of the polymerizable monomer, crosslinking agent, and initiator, the content of the polymerizable monomer is 94.9 wt%, the content of the crosslinking agent is 5 wt%, and the content of the initiator is 0.1 wt%. The amount of electrolyte salt added satisfies: [EO]:[Li + The molar ratio is 20:1.

[0031] [Comparative Example 3] Comparative Examples 1-8 all provide a Li|| LFP soft-pack all-solid-state battery. The only difference between the preparation method of the Li|| LFP soft-pack all-solid-state battery provided in Comparative Examples 1-8 and the preparation method of the Li|| LFP soft-pack all-solid-state battery in Example 1 is that the thermal curing temperature on the lithium negative electrode side and the thermal curing temperature on the positive electrode side are set differently in step S3, as shown in Table 1.

[0032] Table 1

[0033] [Comparison Test] The Li || LFP pouch-type solid-state batteries provided in Examples 1-3 and the Li || LFP pouch-type solid-state batteries provided in Comparative Examples 1-8 were subjected to the following comparative tests at room temperature.

[0034] (1) Room temperature ionic conductivity test: The solid battery was sandwiched between two stainless steel pads and AC impedance was tested using a Chenhua CHI660D electrochemical workstation at a frequency of 1MHz-0.1Hz.

[0035] (2) Charge-discharge cycle performance test: The charge-discharge voltage range of the solid-state battery is 2.5-3.8V, the charge-discharge current is 0.5C, and the charge-discharge cycle is 500 cycles. The discharge capacity of the first cycle and the discharge capacity of the 500th cycle are recorded, and the capacity retention rate is calculated.

[0036] (3) Nanoindentation test: Disassemble the solid battery to obtain the solid electrolyte, fix the solid electrolyte on the sample stage, set the test parameters such as maximum load, loading rate and holding time, and slowly contact the sample surface with the indenter and apply the load.

[0037] The test results are shown in Table 2. It should be noted that during the charge-discharge cycle performance test, the solid-state batteries provided by Comparative Examples 2-4 and Comparative Example 6 both experienced a sudden voltage drop (micro-short circuit) between the 80th and 100th cycles of the charge-discharge cycle. Upon dissection, it was found that lithium dendrites pierced the electrolyte.

[0038] According to the test results in Table 2, it can be seen that during the preparation of the solid-state batteries provided in Examples 1-3, the thermal curing temperature on the lithium anode side is relatively high. At this high temperature, the initiator decomposes extremely quickly, the free radical concentration explodes instantaneously, and a rapid and highly dense cross-linking reaction occurs, forming a hard "anti-dendritic shell layer." The thermal curing temperature on the cathode side is relatively low. At the lower temperature, the reaction is stable, and the polymer chains have sufficient time to spread and arrange, forming a "highly conductive core layer" with low cross-linking degree and high free volume. Furthermore, it is necessary to strictly control the thermal curing temperature and temperature difference on both sides to simultaneously achieve: significantly reducing interfacial impedance, increasing room temperature ionic conductivity, and significantly improving the charge-discharge cycle performance of the solid-state battery.

[0039] As shown in Table 2, compared with the comparative example, the room temperature ionic conductivity and charge-discharge cycle performance of the all-solid-state battery in this application embodiment are significantly improved. This result indicates that, based on the in-situ polymerization preparation of all-solid-state batteries, during the heating polymerization and solidification process of the solid electrolyte precursor liquid, the temperature gradients on both sides guide the different monomer polymerization rates and degrees within different temperature gradients. By controlling T... high T low and (T) high -T low Although the numerical range of ) caused uneven solidification of the solid electrolyte, it was unexpectedly found that it could significantly improve the room temperature ionic conductivity and charge-discharge cycle performance of the solid battery at the same time.

[0040] Table 2

[0041] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a solid-state battery, characterized in that, The preparation method includes the following steps: The process of preparing a precursor solution by mixing polymerizable monomers, crosslinking agents, electrolyte salts and initiators under vacuum or protective gas atmosphere; The process of injecting the precursor solution into the porous support material between the positive and negative electrodes and assembling the battery; Simultaneously, the process involves high-temperature curing of the precursor solution in contact with the negative electrode side and low-temperature curing of the precursor solution in contact with the positive electrode side. The high-temperature curing temperature is T. high The temperature for low-temperature curing is T. low Simultaneously satisfying: 130℃≥T high ≥80℃, 70℃≥T low ≥40℃, temperature difference T high -T low ≥20℃.

2. The preparation method according to claim 1, characterized in that, The polymerizable monomer can be polymerized at a temperature greater than or equal to 40°C and less than or equal to 130°C by the initiator and thermal initiation, and the polymerizable monomer is liquid at room temperature.

3. The preparation method according to claim 2, characterized in that, The polymerizable monomer is selected from at least one of acrylate monomers, olefin double bond monomers, acrylamide monomers, and siloxane monomers.

4. The preparation method according to claim 1, characterized in that, The crosslinking agent is selected from at least one of trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethoxylated bisphenol A diacrylate, and trimethylolpropane trimethacrylate.

5. The preparation method according to claim 1, characterized in that, The initiator is selected from benzoyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, lauroyl peroxide, diisopropyl peroxide, dicyclohexyl peroxide, benzoyl tert-butyl peroxide, tert-butyl peroxyvalerate, methyl ethyl ketone peroxide, cyclohexanone peroxide, di-tert-butyl peroxide, dicumyl peroxide, cumene peroxide, cumene hydrogen peroxide, tert-butyl hydrogen peroxide, potassium tert-butoxide, and tert-butyl peroxide. At least one of lithium alkoxide, aluminum triisopropoxide, boron trifluoride ethyl ether, boron trifluoride butyl ether, phosphorus pentafluoride, aluminum trifluoride, aluminum trichloride, aluminum trifluoromethanesulfonate, silver perchlorate, bismuth trichloride, stannous octoate, stannous tetrachloride, zinc dichloride, titanium tetrachloride, titanium tetrabromide, beryllium dichloride, ferric trichloride, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalate borate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorooxalate borate, lithium powder, and sodium powder.

6. The preparation method according to claim 1, characterized in that, The electrolyte salt is a lithium salt or a sodium salt; The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxaborate, lithium difluorooxaborate, and lithium difluorophosphate. The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium di(oxalateborate), sodium di(fluorooxalateborate), and sodium difluorophosphate.

7. The preparation method according to claim 6, characterized in that, The electrolyte salt is a lithium salt, and the concentration of the lithium salt in the precursor solution satisfies: [EO]:[Li + The molar ratio is between 10:1 and 20:

1.

8. The preparation method according to claim 1, characterized in that, Based on the total mass of the polymerizable monomer, crosslinking agent, and initiator, the content of the polymerizable monomer is from 68 wt% to 94.9 wt%, the content of the crosslinking agent is from 5 wt% to 30 wt%, and the content of the initiator is from 0.1 wt% to 2 wt%.

9. A solid-state battery, characterized in that, The solid-state battery is prepared by the preparation method according to any one of claims 1-8, and the solid-state battery includes positive and negative electrodes and a solid electrolyte disposed between the positive and negative electrodes; The solid-state battery satisfies the following condition: the crosslinking density of the solid electrolyte is distributed in a gradient direction in the thickness direction, and the crosslinking density of the solid electrolyte near the negative electrode is higher than that near the positive electrode.

10. The solid-state battery according to claim 9, characterized in that, The solid-state battery is a lithium-ion secondary battery, a lithium metal secondary battery, a sodium-ion secondary battery, or a sodium metal secondary battery.

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