Solid-state electrolyte, method for preparing the same, and solid-state battery

Abstract

This invention belongs to the field of battery technology and discloses a solid electrolyte, its preparation method, and a solid battery. The solid electrolyte is formed by in-situ polymerization of a precursor solution containing an alkali metal salt and polymerizable monomers. The polymerizable monomers include a first monomer and a second monomer. The first monomer includes a cyclic sulfone compound, and the second monomer includes a fluorinated propylene ester compound. This invention utilizes the ultra-high dielectric constant of the cyclic sulfone group to significantly promote the dissociation of lithium salt in the polymer matrix, greatly improving ionic conductivity. Simultaneously, the strong electron-withdrawing effect of the fluorinated side chain lowers the HOMO energy level of the polymer, enabling the electrolyte to withstand oxidation voltages above 5.0V. Furthermore, a stable interface film rich in LiF is generated in-situ at the negative electrode interface, thereby significantly improving the cycle stability and rate performance of the battery under high voltage.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a solid electrolyte, its preparation method, and a solid battery. Background Technology

[0002] As the global energy structure shifts towards clean energy, developing rechargeable lithium-based batteries that combine high energy density and high safety has become crucial. Battery material systems are evolving in tandem towards high voltage and high capacity. Positive electrodes include nickel-rich layered oxides, lithium-rich manganese-based materials, and high-voltage polyanionic compounds, while negative electrodes are developing towards silicon-carbon composites and lithium metal anodes. However, the electrochemical stability window of traditional liquid electrolytes (mainly organic carbonates) is typically below 4.3V (vs. Li / Li). + Furthermore, liquid electrolytes pose safety hazards such as flammability and leakage, severely hindering the realization of high-voltage battery systems. Replacing liquid electrolytes with solid electrolytes is considered an important way to improve battery energy density and safety.

[0003] Among various solid-state electrolytes, polymer electrolytes have become one of the most promising options for practical application due to their excellent film-forming properties, machinability, and interfacial contact potential with electrodes. Currently, mainstream polymer electrolyte systems, such as polyethers (represented by PEO), while having flexible chains that facilitate ion transport, suffer from poor high-voltage resistance due to the easy oxidation and decomposition of their ether oxygen bonds above approximately 3.9V, coupled with low room-temperature ionic conductivity, typically requiring high-temperature operation. To improve voltage resistance, polyester / polyacrylate electrolytes can increase the oxidation potential to above 4.3V by introducing strong electron-withdrawing groups such as fluorine-containing groups and carbonyl groups. However, such modifications often lead to a decrease in the polymer dielectric constant and reduced chain mobility, resulting in difficulties in lithium salt dissociation and insufficient carrier concentration, significantly deteriorating ionic conductivity. Although some progress has been made through copolymerization, crosslinking, and the addition of plasticizers, existing polymer electrolytes still generally face challenges of insufficient ionic conductivity and poor long-term stability under high-voltage conditions, limiting the overall electrochemical performance and safety of batteries.

[0004] Currently, high-performance solid-state polymer electrolytes face two major challenges that affect the safe application of high-energy-density lithium-based batteries. First, at the level of materials chemistry and synthesis, it is necessary to overcome the challenges of developing high-dielectric-constant functional monomers, such as 3-cyclobutene sulfone (BdS, ε...). rThe challenges of effectively utilizing BdS (>40) are significant. Due to its extremely high polarity, BdS can theoretically significantly promote lithium salt dissociation, making it an ideal building block for improving bulk ionic conductivity. However, the large steric hindrance of its intracyclic double bonds makes conventional free radical homopolymerization difficult, and it is prone to irreversible reverse Cheletropic reactions under thermal conditions, decomposing into small molecules such as sulfur dioxide and butadiene. This prevents the monomer from stably embedding into the polymer network, hindering the transformation of its excellent theoretical properties into practical materials. Secondly, regarding electrochemical interface stability, the interfacial failure problem on both sides of the high-voltage cathode and the highly active lithium metal anode needs to be addressed simultaneously. On the cathode side, existing polymer electrolytes are prone to continuous oxidative decomposition at voltages exceeding 4.3V, making it difficult to form a dense, stable, and highly ionicly conductive cathode electrolyte interface (CEI) film in situ, resulting in a surge in interfacial impedance and rapid capacity decay. On the negative electrode side, uneven lithium-ion flow and continuous interfacial side reactions can easily induce lithium dendrite growth and cause repeated cracking and reconstruction of the solid electrolyte interface (SEI) structure. This not only accelerates the irreversible consumption of lithium and electrolyte, but also brings serious safety hazards.

[0005] Therefore, it is urgent to design and construct a novel solid polymer electrolyte system that can simultaneously overcome the two major bottlenecks of material synthesis and interface stability, while taking into account high voltage resistance (>4.5V), high room temperature ionic conductivity, and intrinsic interface stability. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a solid electrolyte, a method for preparing the same, and a solid battery. The solid electrolyte can simultaneously achieve high voltage tolerance and high ion transport efficiency, thereby improving the energy density and intrinsic safety of the battery.

[0007] To solve the above-mentioned technical problems, a first aspect of the present invention provides a solid electrolyte, which is formed by in-situ polymerization of a precursor solution, wherein the precursor solution contains an alkali metal salt and a polymerization monomer, the polymerization monomer includes a first monomer and a second monomer, the first monomer includes a cyclic sulfone compound, and the second monomer includes a fluorinated propylene ester compound.

[0008] Specifically, the solid electrolyte of the present invention comprises a polymer matrix and an alkali metal salt (such as a lithium salt), wherein: the polymer matrix is ​​formed by in-situ polymerization of a first monomer cyclic sulfone compound and a second monomer fluorinated acrylate compound, which can significantly improve the cycle stability and rate performance of the battery under high voltage. On the one hand, the cyclic sulfone compound has an ultra-high dielectric constant (ε). r>40), its highly polar sulfone group (-SO2-) can effectively shield the electrostatic attraction between lithium ions and anions, promote the dissociation of lithium salt in the polymer matrix, and construct a highly efficient lithium ion transport channel, thereby significantly improving the bulk ionic conductivity while maintaining high voltage stability. On the other hand, the highly active fluorinated acrylate free radical acts as an "initiation engine," forcibly opening the inert double bonds within the ring of cyclic sulfone compounds through a specific copolymerization strategy, stably chemically bonding them to the polymer backbone. This not only overcomes the kinetic barrier of monomer polymerization and avoids its thermal decomposition, but also significantly reduces the highest occupied molecular orbital (HOMO) energy level of the polymer by utilizing the strong electron-withdrawing effect of the fluorinated side chain, enabling the electrolyte to withstand oxidation voltages above 5.0V and achieve high voltage resistance. Furthermore, the LiF-rich solid electrolyte interphase (SEI / CEI) film generated by the in-situ reduction of fluorinated acrylate compounds at the electrode interface has high interfacial energy and low ion diffusion barrier, which can effectively suppress lithium dendrite growth and prevent the active material from dissolving or undergoing side reactions under high pressure, thereby achieving a dual improvement in material synthesis stability and interfacial kinetics.

[0009] In some embodiments of the present invention, the cyclic sulfone compound is a sulfone monomer having a five-membered ring internal double bond structure, preferably 3-cyclobutene sulfone and its derivatives.

[0010] In some embodiments of the present invention, the cyclic sulfone compound has a structural formula selected from at least one of formulas S-1 to S-8: .

[0011] In some embodiments of the present invention, the fluorinated propylene ester compound is an acrylate or methacrylate with fluorinated side chain, preferably 2,2,2-trifluoroethyl acrylate and its derivatives, used to adjust the mechanical strength and ionic conductivity of the solid electrolyte.

[0012] In some embodiments of the present invention, the fluoropropylene ester compound has a structural formula selected from at least one of formulas F-1 to F-8: .

[0013] In some embodiments of the present invention, the alkali metal salt includes a lithium salt, wherein the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, lithium difluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, and lithium trifluoromethanesulfonate.

[0014] In some embodiments of the present invention, the concentration of the alkali metal salt in the precursor solution is 0.2-1.5 mol / L; preferably, the concentration of the alkali metal salt is 0.8-1.2 mol / L.

[0015] In some embodiments of the present invention, the precursor solution further contains an auxiliary agent, which includes at least one of a plasticizer, an initiator, and a crosslinking agent.

[0016] In some embodiments of the present invention, the plasticizer is selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene carbonate, propanesulfonate lactone, trimethyl phosphate, trifluoromethyl ethylene carbonate, ethoxy(pentafluoro)cyclotriphosphazene, vinyl sulfate, methanedisulfonate, p-toluenesulfonyl isocyanate, dimethyldimethoxysilane, N,N-dimethylformamide, perfluorohexanone, and triethyl phosphate, and is used to enhance the stability of the electrolyte and the electrolyte / interface.

[0017] In some embodiments of the present invention, the initiator may be a commonly used initiator in the art, such as azobisisobutyronitrile (AIBN).

[0018] In some embodiments of the present invention, the crosslinking agent may be a commonly used crosslinking agent in the art, such as polyethylene glycol diacrylate (PEGDA, Mw=400).

[0019] In some embodiments of the present invention, the volume ratio of the first monomer, the second monomer and the plasticizer is (1-80):(1-80):(1-70).

[0020] In some embodiments of the present invention, the volume ratio of the first monomer, the second monomer and the plasticizer is (3-70):(3-70):(3-60).

[0021] In some embodiments of the present invention, the volume ratio of the first monomer, the second monomer and the plasticizer is (35-70):(35-70):(30-60).

[0022] In some embodiments of the present invention, the crosslinking agent is used in an amount of 0.1-10% of the total mass of the precursor solution.

[0023] In some embodiments of the present invention, the crosslinking agent is used in an amount of 2-8% of the total mass of the precursor solution.

[0024] In some embodiments of the present invention, the amount of the initiator is 0.1-1% of the total mass of the precursor solution.

[0025] In some embodiments of the present invention, the amount of the initiator is 0.1-0.5% of the total mass of the precursor solution.

[0026] A second aspect of the present invention provides a method for preparing the solid electrolyte described in the first aspect of the present invention, comprising the following steps: The raw material components for preparing the precursor solution are mixed, heated, and polymerized in situ to obtain the solid electrolyte.

[0027] In some embodiments of the present invention, the heating temperature is 40-80°C and the heating time is 1-48 hours.

[0028] In some embodiments of the present invention, the heating temperature is 50-70°C and the heating time is 1-30 hours.

[0029] In some embodiments of the present invention, the method for preparing the solid electrolyte includes the following steps: (1) Mix the first monomer, the second monomer and the plasticizer with the alkali metal salt respectively to prepare solution A, solution B and solution C; (2) After mixing the solutions A, B and C, a crosslinking agent and an initiator are added and stirred to obtain a precursor solution of a solid electrolyte; (3) The precursor solution is heated to carry out in-situ polymerization to obtain the solid electrolyte.

[0030] In some embodiments of the present invention, steps (1) and (2) are both performed under an inert atmosphere.

[0031] In some embodiments of the present invention, the inert atmosphere is an atmosphere filled with argon gas, wherein H2O < 0.01 ppm and O2 < 0.01 ppm.

[0032] Specifically, the solid electrolyte of this invention is prepared using an in-situ thermally initiated free radical copolymerization process, utilizing highly active fluorinated acrylate free radicals to initiate inert cyclic sulfone monomers for in-situ copolymerization and curing. Simultaneously, a group dissolution strategy is employed, where the first monomer, the second monomer, and the plasticizer are first mixed with the alkali metal salt separately to address the issues of uneven dissolution and dispersion.

[0033] A third aspect of the present invention provides a solid-state battery comprising the solid electrolyte described in the first aspect of the present invention, or comprising a solid electrolyte prepared by the preparation method described in the second aspect of the present invention.

[0034] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) The solid electrolyte of the present invention introduces cyclic sulfone compounds with ultra-high dielectric constant (such as 3-cyclobutene sulfone and its derivatives), and utilizes its highly polar sulfone group (-SO2-) to effectively shield alkali metal ions (such as Li) +The electrostatic attraction between the ions and anions creates a highly efficient lithium-ion transport channel; at the same time, combined with the strong electron-withdrawing fluorine effect of fluorinated propylene esters (such as 2,2,2-trifluoroethyl acrylate and its derivatives), the highest occupied molecular orbital (HOMO) energy level of the polymer is significantly reduced, thus achieving high voltage resistance while maintaining excellent ionic conductivity.

[0035] (2) This invention utilizes highly active fluorinated acrylate free radicals as an "initiation engine" to forcibly open the inert double bonds of cyclic sulfone compounds through a copolymerization strategy, and stably chemically bond them to the polymer backbone, thus successfully overcoming the kinetic barrier of monomer polymerization and avoiding monomer decomposition and phase separation problems.

[0036] (3) The present invention adopts an in-situ thermosetting process, in which the liquid precursor can fully wet the porous structure of the electrode before polymerization, and form a continuous and dense ion transport interface after curing. At the same time, the solid electrolyte interphase (SEI) film rich in LiF generated by the in-situ reduction of cyclic sulfone compounds on the negative electrode side has high interfacial energy and low ion diffusion barrier, which can effectively suppress lithium dendrite growth; at the same time, a high-voltage resistant CEI film is formed on the positive electrode side to prevent the active material from dissolving or undergoing side reactions under high voltage.

[0037] (4) The solid electrolyte preparation method of the present invention does not require expensive extrusion equipment or complex solvent treatment processes. The low-viscosity monomer precursor used can be directly injected into the battery casing using existing liquid injection equipment, and then solidification can be completed by simple heating. This "liquid injection-thermal polymerization" process not only significantly reduces manufacturing costs, but also retains the efficient production process of traditional liquid batteries, and has great potential for large-scale application. Attached Figure Description

[0038] Figure 1 Fourier transform infrared (FTIR) spectrum of the solid electrolyte prepared in Example 1 of this invention. Figure 2 The results of linear sweep voltammetry tests are shown for the Li||Al asymmetric battery assembled based on the solid electrolyte prepared in Example 1 of this invention. Figure 3 The results are Tafel polarization tests of the Li||Li symmetric battery assembled based on the solid electrolyte prepared in Example 1 of this invention. Figure 4 The results are from long-cycle testing of the Li||NCM811 full cell assembled based on the solid electrolyte prepared in Example 1 of this invention. Figure 5 The results are from long-cycle tests of the Li||NCM811 full cell assembled based on the solid electrolyte prepared in Example 2 of this invention. Figure 6The results are from long-cycle testing of the Li||NCM811 full cell assembled based on the solid electrolyte prepared in Example 3 of this invention. Figure 7 The results are from long-cycle tests of the Li||NCM811 full cell assembled based on the solid electrolyte prepared in Example 4 of this invention. Figure 8 The results are from long-cycle tests of the Li||NCM811 full cell assembled using the solid electrolyte prepared in Comparative Example 2 of this invention. Detailed Implementation

[0039] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0040] Example 1 A solid electrolyte is obtained by in-situ polymerization of a precursor solution, wherein the precursor solution contains a first monomer, a second monomer, a lithium salt, a plasticizer, a crosslinking agent, and an initiator. Wherein: The first monomer is 3-cyclobutene sulfone (BdS), with the structural formula shown in S-1; The second monomer is 2,2,2-trifluoroethyl acrylate (TFEA), with the structural formula shown in F-1; The lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFS); The plasticizer is fluoroethylene carbonate (FEC). The crosslinking agent is polyethylene glycol diacrylate (PEGDA, Mw=400). The initiator is azobisisobutyronitrile (AIBN).

[0041] The volume ratio of the first monomer, the second monomer, and the plasticizer is 35:35:30. The solubility of lithium salt in the precursor solution is 1 mol / L. The amounts of crosslinking agent and initiator account for 5% and 0.1% of the total mass of the precursor solution, respectively.

[0042] The preparation method of the above-mentioned solid electrolyte includes the following steps: (1) Mix the first monomer, the second monomer and the plasticizer with lithium salt respectively to prepare solutions A, B and C with a concentration of 1 mol / L respectively; (2) After mixing the solutions A, B and C prepared in step (1), add the crosslinking agent and the initiator, stir until a uniform and transparent solution is formed, and the precursor solution is obtained. (3) The precursor solution obtained in step (2) is placed in the battery casing and heated at 60°C for 8 hours to carry out in-situ polymerization to obtain the solid electrolyte of this embodiment.

[0043] Wherein: Steps (1) and (2) are both carried out in a glove box filled with argon gas, and the H2O in the glove box is less than 0.01 ppm and the O2 is less than 0.01 ppm.

[0044] Example 2 The only difference between Example 2 and Example 1 is that the second monomer is replaced with an equal amount of pentafluoroacrylate, the structural formula of which is shown in F-2.

[0045] Example 3 The only difference between Example 3 and Example 1 is that the second monomer is replaced with an equal amount of heptafluoroacrylate, the structural formula of which is shown in F-3.

[0046] Example 4 The only difference between Example 4 and Example 1 is that the first monomer is replaced with an equal amount of a cyclic sulfone compound with the structural formula shown in S-8.

[0047] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the precursor solution does not contain a second monomer.

[0048] The results showed that due to the huge steric hindrance of the first monomer BdS, its intracyclic double bond is difficult to undergo free radical homopolymerization under normal conditions; and the monomer is very prone to reverse Cheletropic reaction under thermal initiation conditions of 60℃, rapidly decomposing into small molecule gases such as sulfur dioxide and butadiene, which makes it impossible for the system to solidify into a film.

[0049] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the precursor solution does not contain the first monomer.

[0050] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that an equal amount of ethoxyethoxyethyl acrylate was used to replace the first monomer in Example 1 to prepare the precursor solution.

[0051] Performance testing 1. Structural Characterization The P(TFEA-BdS) solid electrolyte prepared in Example 1 was subjected to Fourier transform infrared spectroscopy (FTIR) testing, and the results are as follows: Figure 1 As shown in the spectrum, it can be clearly observed that at wavelengths of 1600-1650 cm⁻¹...-1 The nearby characteristic peaks completely disappeared; these are the characteristic absorption peaks of the C=C double bond. This indicates that after the precursor solution underwent a thermal initiation process, the double bonds in the TFEA and BdS monomers were completely opened and participated in the polymerization reaction. There were no residual monomers in the system, proving the successful construction of the copolymer network and the completeness of the "in-situ polymerization and curing" process.

[0052] 2. Electrochemical stability window testing In a glove box environment filled with high-purity argon (H2O < 0.01 ppm, O2 < 0.01 ppm), Li||Al asymmetric coin cells for testing the electrochemical stability window were assembled. First, a cut aluminum foil was placed as the working electrode in a vacuum-dried positive electrode shell base. Approximately half the amount of the solid electrolyte precursor solutions prepared in Example 1 and Comparative Example 2 were injected onto the surface of the aluminum foil using a liquid injection device. Subsequently, a vacuum-dried porous polyethylene (PE) membrane was covered, and the remaining precursor solution was injected over the membrane. A 450 μm thick, 15.6 cm high membrane was then placed. 2 Large lithium metal sheets were used as both counter and reference electrodes, followed by the sequential stacking of stainless steel gaskets, spring contacts, and negative electrode shells, and then sealed and pressed together using a battery packaging machine. The packaged batteries were then transferred to an oven for in-situ thermal polymerization and curing at 60°C for 8 hours to ensure complete opening of the monomer double bonds and the formation of a continuous, dense ion transport interface. Linear sweep voltammetry (LSV) was used for testing at a scan rate of 0.1 mV / s and a voltage range of 0-7 V. The increasing trend of current density with voltage was observed, and the results are as follows: Figure 2 As shown.

[0053] Depend on Figure 2 It can be seen that the current density of the Li||Al asymmetric battery assembled based on the solid electrolyte P(TFEA-BdS) prepared in Example 1 remained at an extremely low level before the voltage scan reached 5.5V, and only after exceeding this voltage did a significant oxidative decomposition current begin to appear. This indicates that the copolymer electrolyte has an extremely high electrochemical window (>5.0V), thanks to the strong electron-withdrawing fluorine effect of the TFEA side chain, which significantly reduces the HOMO energy level of the polymer. This result proves that the electrolyte can fully meet the requirements of high-nickel ternary (NCM811) and even higher voltage cathode materials, ensuring the cycle stability of the battery under high voltage conditions. In contrast, the Li||Al asymmetric battery assembled based on the solid electrolyte PTFEA prepared in Comparative Example 2 has a voltage withstand window of only about 4.3V.

[0054] Meanwhile, using the same testing method, linear sweep voltammetry tests were performed on the Li||Al asymmetric battery assembled based on the solid electrolyte prepared in Comparative Example 3. The results showed that the current density began to increase dramatically in the range of approximately 3.9-4.2 V, indicating that the ether oxygen group is highly susceptible to oxidative decomposition at high voltages. In contrast, the system of this invention maintained an extremely low current level until the voltage scan reached 5.5 V, demonstrating the deep optimization of the polymer HOMO energy level by the strong electron-withdrawing effect of the cyclic sulfone combined with F1, thus meeting the requirements of ultra-high voltage batteries.

[0055] 3. Interface dynamics testing In a high-purity argon glove box environment (H2O < 0.01 ppm, O2 < 0.01 ppm), a Li||Li symmetric coin cell was assembled to evaluate interfacial transport kinetics. First, a first 450 μm thick, 15.6 cm² coin cell was assembled. 2 A large lithium metal sheet was placed at the center of the battery casing base, and appropriate amounts of the solid electrolyte precursor solutions prepared in Example 1 and Comparative Example 2 were injected to ensure that the lithium metal surface was fully wetted by the liquid precursor. A PE separator was then placed, and after being fully wetted again by injecting the precursor solution, a second lithium metal sheet was stacked on top as a symmetrical electrode. The gasket, spring sheet, and negative electrode shell were then stacked and sealed. The sealed battery was subjected to an in-situ thermally initiated free radical copolymerization process at 60°C for 8 hours. The Tafel polarization test method was used to evaluate the lithium-ion transport kinetics at the interface, with a polarization potential range of ±0.1V (vs. open-circuit voltage). The results are as follows: Figure 3 As shown.

[0056] Depend on Figure 3 As can be seen from the fitting analysis of the linear region of the curve, the Li||Li symmetric battery assembled based on the solid electrolyte P(TFEA-BdS) prepared in Example 1 has a higher exchange current density. The higher exchange current density indicates a lower charge transfer barrier for lithium ions at the electrolyte-lithium metal interface and a faster reaction kinetic rate. This suggests that the high dielectric constant sulfone groups introduced into the electrolyte effectively promote the dissociation of lithium salts and increase the concentration of free lithium ions at the interface. This excellent interfacial kinetic characteristic helps induce uniform lithium ion deposition, fundamentally reducing local polarization and effectively suppressing the nucleation and growth of lithium dendrites. In contrast, the Li||Li symmetric battery assembled based on the solid electrolyte PTFEA prepared in Comparative Example 2 has an exchange current density of only 0.0497 mA / cm². 2 This demonstrates its inadequacy in lithium salt dissociation and interfacial transport kinetics. In contrast, the P(TFEA-BdS) copolymer system in Example 1, due to the introduction of highly polar cyclic sulfone groups, exhibited an exchange current density that soared to 0.399 mA / cm². 2 The performance has been greatly improved.

[0057] 4. Long-cycle performance testing The solid electrolytes prepared in Examples 1-4 and Comparative Example 2 were assembled into lithium-pair NCM811 full cells, respectively, and subjected to long-cycle testing at 0.3C / 0.5C charge-discharge at 30°C. The results are as follows: Figure 4-8 As shown in Table 1.

[0058] The assembly process of the Li||NCM811 full cell is as follows: (1) Preparation of positive electrode sheet Active material NCM811, conductive carbon black, and binder PVDF were mixed in a weight ratio of 90:5:5, and then added to NMP solvent and stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was then coated onto aluminum foil, and after pre-drying the positive electrode sheet, it was transferred to a vacuum oven for further drying, and then cut into positive electrode sheets for later use.

[0059] (2) Preparation of negative electrode sheet The aluminum foil was cut into electrode sheets and stored in a vacuum under low water and oxygen conditions for later use.

[0060] (3) Preparation of the diaphragm Cut the porous polyethylene film into diaphragms, vacuum dry for 6 hours, and set aside for later use.

[0061] (4) Battery assembly The positive electrode is placed in the battery case, and half of the solid electrolyte precursor solution prepared in Examples 1-4 and Comparative Example 2 is injected. The separator is then placed in, and the remaining half of the precursor solution is injected. The negative electrode, gasket, spring sheet and negative electrode shell are then placed in, and finally the battery is placed in the battery packaging machine for packaging.

[0062] Depend on Figure 4 It can be seen that after the first cycle of activation, the discharge capacity of the battery remains at a high level, and the coulombic efficiency remains close to 100%. With the increase of the number of cycles, the capacity retention rate is excellent, and no significant drop occurs. This indicates that a stable CEI film is formed on the positive electrode side of the electrolyte, and a tight solid-solid interface is constructed inside the battery, effectively suppressing the occurrence of side reactions and verifying the practicality of this system in high-voltage, high-energy-density batteries.

[0063] Table 1:

[0064] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A solid electrolyte, characterized in that, The solid electrolyte is formed by in-situ polymerization of its precursor solution, which contains an alkali metal salt and a polymerization monomer. The polymerization monomer includes a first monomer and a second monomer. The first monomer includes a cyclic sulfone compound, and the second monomer includes a fluorinated propylene ester compound.

2. The solid electrolyte according to claim 1, characterized in that, The structural formula of the cyclic sulfone compound is selected from at least one of formulas S-1 to S-8: ； The fluoropropylene ester compound has a structural formula selected from at least one of formulas F-1 to F-8: 。 3. The solid electrolyte according to claim 1, characterized in that, The alkali metal salt includes a lithium salt, which is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, lithium difluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, and lithium trifluoromethanesulfonate.

4. The solid electrolyte according to claim 1, characterized in that, In the precursor solution, the concentration of the alkali metal salt is 0.2-1.5 mol / L.

5. The solid electrolyte according to claim 1, characterized in that, The precursor solution also contains an auxiliary agent, which includes at least one of a plasticizer, an initiator, and a crosslinking agent. The plasticizer is selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene carbonate, propanesulfonate lactone, trimethyl phosphate, trifluoromethyl ethylene carbonate, ethoxy(pentafluoro)cyclotriphosphazene, vinyl sulfate, methanedisulfonate, p-toluenesulfonyl isocyanate, dimethyl dimethoxysilane, N,N-dimethylformamide, perfluorohexanone, and triethyl phosphate.

6. The solid electrolyte according to claim 5, characterized in that, The volume ratio of the first monomer, the second monomer and the plasticizer is (1-80):(1-80):(1-70).

7. The solid electrolyte according to claim 5, characterized in that, The crosslinking agent is used in an amount of 0.1-10% of the total mass of the precursor solution, and the initiator is used in an amount of 0.1-1% of the total mass of the precursor solution.

8. A method for preparing a solid electrolyte as described in any one of claims 1-7, characterized in that, Includes the following steps: The raw material components for preparing the precursor solution are mixed, heated, and polymerized in situ to obtain the solid electrolyte.

9. The preparation method according to claim 8, characterized in that, Includes the following steps: (1) Mix the first monomer, the second monomer and the plasticizer with the alkali metal salt respectively to prepare solution A, solution B and solution C; (2) After mixing the solutions A, B and C, a crosslinking agent and an initiator are added and stirred to obtain a precursor solution of a solid electrolyte; (3) The precursor solution is heated to carry out in-situ polymerization to obtain the solid electrolyte.

10. A solid-state battery, characterized in that, It includes the solid electrolyte as described in any one of claims 1-7, or the solid electrolyte prepared by the preparation method described in claim 8 or 9.

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