A halide composite solid electrolyte membrane and a preparation method thereof, and a solid-state battery

Abstract

This invention discloses a halide composite solid electrolyte membrane, its preparation method, and a solid-state battery. The preparation method involves dissolving a polymer in an organic solvent and electrospinning it to obtain a polymer skeleton with a porous fiber structure. A halide electrolyte dispersion is then cast into the skeleton and dried to obtain a first composite electrolyte membrane. A second composite electrolyte membrane is obtained through hot pressing. Finally, a gel electrolyte solution composed of monomers, initiators, lithium salts, and plasticizers is sprayed onto the membrane surface and cured under ultraviolet light to obtain the halide composite solid electrolyte membrane. This invention effectively solves the problems of halide electrolytes being difficult to form films independently, poor air stability, and poor compatibility with metallic lithium anodes. The resulting electrolyte membrane has controllable thickness, is dense and uniform, and the assembled solid-state battery exhibits excellent cycle performance.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, specifically to a method for preparing a halide composite solid electrolyte membrane, the halide composite solid electrolyte membrane obtained by the method, and a solid-state battery comprising the halide composite solid electrolyte membrane. Background Technology

[0002] With the rapid development of new energy vehicles and large-scale energy storage systems, increasingly higher demands are being placed on the energy density and safety performance of secondary batteries. Traditional liquid lithium-ion batteries, limited by the flammability and electrochemical stability window of organic electrolytes, struggle to balance high energy density and high safety, posing safety hazards such as thermal runaway. All-solid-state batteries, using solid electrolytes instead of organic liquid electrolytes, fundamentally eliminate the risks of electrolyte leakage and combustion, and are expected to be compatible with lithium metal anodes and high-voltage cathode materials, thus being regarded as an important development direction for next-generation high-energy-density energy storage technology.

[0003] Solid-state electrolytes are the core component of all-solid-state batteries, and currently mainly include four categories: polymers, oxides, sulfides, and halides. Polymer solid-state electrolytes have good flexibility, but low room-temperature ionic conductivity and narrow thermal and electrochemical stability windows; oxide solid-state electrolytes have excellent chemical and electrochemical stability, but the materials are rigid, difficult to process and mold, and have high production costs; sulfide solid-state electrolytes have high ionic conductivity, but poor oxidation stability, are extremely sensitive to environmental humidity, and have poor compatibility with cathode materials.

[0004] Halide solid electrolytes exhibit a relatively balanced overall performance in terms of electrochemical oxidation stability, ionic conductivity, and mechanical deformability, with relatively low material and processing costs, making them one of the important candidate materials for promoting the commercialization of all-solid-state batteries. However, it is difficult to form halide solid electrolyte films on their own, making it hard to obtain films with uniform thickness and good mechanical properties. In addition, halide solid electrolytes are sensitive to air humidity, are prone to hydrolysis or side reactions that lead to a decrease in ionic conductivity, and have poor interfacial compatibility with lithium metal anodes, making them susceptible to interfacial side reactions and failure during cycling.

[0005] In summary, existing halide solid electrolytes still suffer from poor film-forming properties, insufficient air stability, and poor compatibility with lithium metal anodes in practical applications, which restricts their practical use in all-solid-state batteries. How to prepare electrolyte films with controllable thickness, dense and uniform structure, good mechanical properties, and good air stability and anode compatibility, while retaining the advantages of high ionic conductivity and wide electrochemical window of halide solid electrolytes, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a method for preparing a halide composite solid electrolyte membrane, a halide composite solid electrolyte membrane obtained by the method, and a solid battery comprising the halide composite solid electrolyte membrane. The specific technical solution is as follows.

[0007] A method for preparing a halide composite solid electrolyte membrane includes the following steps: S1: The polymer is dissolved in an organic solvent and stirred at high speed to form a uniform spinning solution. Then, a polymer skeleton is prepared by electrospinning. The polymer skeleton has a porous fiber structure. S2: Disperse the halide electrolyte in an organic solvent to obtain a dispersion, cast the dispersion onto the polymer backbone, and dry to obtain a first composite electrolyte membrane; S3: The first composite electrolyte membrane is hot-pressed at a temperature of 100-200°C and a pressure of 10-50MPa to obtain the second composite electrolyte membrane; S4: Mix monomers, initiators, lithium salts and plasticizers evenly to prepare a gel electrolyte, and spray the gel electrolyte onto the surface of the second composite electrolyte membrane to obtain a third composite electrolyte membrane; S5: The third composite electrolyte membrane is cured under ultraviolet light to obtain a halide composite solid electrolyte membrane.

[0008] In the above preparation method, a polymer skeleton with a porous fiber structure is constructed by electrospinning technology, which provides a continuous and uniform bearing space for the halide electrolyte, effectively overcoming the inherent defect that halide electrolytes are difficult to form films on their own. The halide electrolyte is cast into the pores of the polymer skeleton, and then hot-pressed to make full contact and densify the polymer skeleton and halide electrolyte, which can significantly reduce the internal porosity and interfacial impedance of the composite electrolyte membrane and establish a continuous ion transport channel. Furthermore, a gel electrolyte is sprayed on the membrane surface and cured in situ by ultraviolet light, so that the gel electrolyte layer uniformly covers the surface of the halide electrolyte membrane. This not only isolates the halide electrolyte from the erosion of air moisture, but also improves the contact state between the electrolyte membrane and the electrode interface. The polymer network formed by in-situ polymerization fills the spaces between the halide electrolyte particles, further improving the mechanical properties of the electrolyte membrane.

[0009] Further, the polymer mentioned in step S1 is selected from one or more of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile, and polyvinylidene fluoride. All of these polymers possess good spinnability and chemical stability, and after electrospinning, they can form a continuous and uniform porous fiber structure, providing a stable supporting framework for halide electrolytes.

[0010] Further, the halide electrolyte in step S2 is selected from one or more of lithium yttrium bromide electrolyte, lithium indium chloride electrolyte, lithium indium bromide electrolyte, and lithium zirconium chloride electrolyte; the organic solvent in S2 is selected from one or more of anhydrous acetonitrile, N,N-dimethylformamide, toluene, and dibutyl ether. The aforementioned halide electrolytes themselves possess high ionic conductivity and a wide electrochemical stability window. The listed organic solvents have good dispersing ability for the halide electrolytes and do not damage their structure, which is beneficial for forming a uniform halide electrolyte distribution within the polymer backbone.

[0011] Furthermore, the mass ratio of polymer to halide electrolyte in the first composite electrolyte membrane is 1:1 to 1:5. Within this mass ratio range, the polymer fiber skeleton can provide sufficient load-bearing strength for the halide electrolyte and ensure sufficient halide electrolyte loading to establish continuous ion transport channels, thereby balancing the mechanical properties and ionic conductivity of the electrolyte membrane.

[0012] Further, the hot-pressing time in step S3 is 0.5–3 hours; the monomer in S4 is selected from one or more of butyl acrylate, polyethylene glycol diacrylate, methyl methacrylate, trifluoroethyl methacrylate, and pentaerythritol triacrylate. The initiator in step S4 is selected from one or more of azobisisobutyronitrile, benzophenone, thioxanthones, and diimidazole. Under the hot-pressing conditions, the contact between the polymer backbone and the halide electrolyte is sufficient without destroying the crystal structure of the halide electrolyte; the listed monomers and initiator can rapidly undergo in-situ polymerization after ultraviolet light irradiation to form a uniform and dense polymer network.

[0013] Further, the lithium salt in step S4 is selected from one or more of lithium bis(trifluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, and lithium dioxalate borate; the plasticizer in step S4 is selected from one or more of succinic anion, glutaronitrile, imidazole ionic liquids, piperidine ionic liquids, pyrrole ionic liquids, and pyridine ionic liquids. The listed lithium salts exhibit good solubility and dissociation ability in the gel electrolyte, and the listed plasticizers can effectively reduce the glass transition temperature of the gel electrolyte and increase its room temperature ionic conductivity, further improving the interfacial contact and ion transport performance of the electrolyte membrane.

[0014] Furthermore, the mass ratio of the gel electrolyte to the halide electrolyte in the third composite electrolyte membrane is 1:1 to 1:3. This ratio range ensures effective coverage and protection of the halide electrolyte membrane surface by the gel electrolyte layer, while avoiding excessive gel components that would dilute the ion transport contribution of the halide electrolyte.

[0015] Furthermore, the UV curing time in step S5 is 3–8 min; the thickness of the halide composite solid electrolyte membrane is 10–50 μm. During the curing time, the monomers in the gel electrolyte can fully polymerize to form a stable cross-linked network; the thickness range is beneficial for reducing the overall impedance of the electrolyte membrane and ensuring that the electrolyte membrane has sufficient mechanical strength to withstand the stress during battery assembly and cycling.

[0016] This invention also provides a halide composite solid electrolyte membrane, which is prepared by the method described above. This halide composite solid electrolyte membrane combines the high ionic conductivity and wide electrochemical window of halide electrolytes, the good mechanical properties of the polymer backbone, and the excellent interfacial compatibility and air stability of the gel electrolyte layer.

[0017] Furthermore, the ionic conductivity of the halide composite solid electrolyte membrane at 25°C is not less than 1×10⁻⁶. -3 The S / cm ratio, electrochemical stability window of not less than 5.0V, and tensile strength of not less than 23MPa are among the performance indicators that enable it to be matched with high-voltage cathode materials and lithium metal anodes, thereby improving the energy density and cycle stability of solid-state batteries.

[0018] The present invention also provides a solid-state battery, comprising a positive electrode, a negative electrode, and a halide composite solid electrolyte membrane as described above. The halide composite solid electrolyte membrane is disposed between the positive electrode and the negative electrode, and the gel electrolyte is disposed on both sides of the halide composite solid electrolyte membrane. During battery assembly, the gel electrolyte can further wet the interface between the electrode and the electrolyte membrane, significantly improving interface contact and reducing interface impedance.

[0019] Furthermore, the positive electrode sheet is formed by mixing positive electrode material, binder polyvinylidene fluoride, and conductive agent Super-P in an N-methylpyrrolidone solvent at a mass ratio of (80-95):(2-10):(2-10) to form a positive electrode slurry. This slurry is coated onto aluminum foil and vacuum dried at 60-100°C for 12-36 hours, followed by roll pressing. The negative electrode is a lithium metal negative electrode. The amount of gel electrolyte added to each side of the halide composite solid electrolyte membrane is 2-10 μL. After battery assembly, it is cured at 40-80°C for 1-6 hours. Solid-state batteries assembled within the above parameter range can achieve good interfacial contact and stable cycle operation.

[0020] Preferably, the positive electrode sheet is formed by mixing positive electrode material, binder polyvinylidene fluoride, and conductive agent Super-P in an N-methylpyrrolidone solvent at a mass ratio of 90:5:5 to form a positive electrode slurry. The positive electrode slurry is coated onto aluminum foil and dried under vacuum at 80°C for 24 hours, then rolled to obtain the final product. The negative electrode is a lithium metal negative electrode. The amount of gel electrolyte added to each side of the halide composite solid electrolyte membrane is 5 μL. After battery assembly, it is heated and cured at 60°C for 3 hours. Under these conditions, the solid-state battery exhibits good interfacial contact and can achieve stable cycle operation.

[0021] Compared with the prior art, the present invention has the following beneficial effects: Firstly, this invention uses a polymer skeleton with a porous fiber structure obtained by electrospinning as a carrier matrix, and uniformly fills the pores of the polymer skeleton with halide electrolyte and densifies it by hot pressing. This effectively overcomes the inherent defect that halide electrolyte is difficult to form a film on its own. The resulting composite electrolyte film has controllable thickness, dense structure, good uniformity, and the preparation process has good compatibility with existing lithium battery production lines.

[0022] Secondly, the present invention forms a continuous gel electrolyte protective layer on the surface of the halide electrolyte membrane by spraying gel electrolyte and curing it in situ with ultraviolet light. This can effectively block the side reactions between environmental moisture and halide electrolyte, significantly improve the air stability of the composite electrolyte membrane in actual production environments such as drying rooms, and the prepared electrolyte membrane can still maintain a high ionic conductivity after being placed in a low dew point environment for 24 hours.

[0023] Third, the gel electrolyte layer formed by the present invention is located between the halide electrolyte membrane and the lithium metal anode, which can avoid direct contact between the halide electrolyte and the lithium metal anode, alleviate the side reactions of the halide electrolyte on the lithium metal anode, improve the interfacial contact state between the electrolyte membrane and the electrode, reduce the interfacial impedance, and thus significantly improve the cycle stability and electrochemical performance of the solid-state battery.

[0024] Fourth, the halide composite solid electrolyte membrane prepared by this invention has a room temperature ionic conductivity of not less than 1×10⁻⁶. -3 With an S / cm, an electrochemical stability window of not less than 5.0V, and a tensile strength of not less than 23MPa, it can be matched with high-voltage cathode materials and lithium metal anodes. Furthermore, the preparation process is simple, the process parameters are easy to control, and the production cost is relatively low, showing good prospects for industrial scale-up and industrial application.

[0025] Fifth, the preparation method of the halide composite solid electrolyte membrane described in this invention has a relatively simple process flow, is convenient to operate, and takes less time. It also has no special restrictions on the types of positive and negative electrode materials, and can be adapted to various existing lithium battery positive and negative electrode systems. This is conducive to reducing the manufacturing cost of solid batteries and improving production efficiency, and is of great significance to promoting the industrial application of solid batteries. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the preparation method of the halide composite solid electrolyte membrane of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. The following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. All reagents and raw materials used are commercially available chemically pure or higher specifications.

[0028] Example 1 The preparation method of the halide composite solid electrolyte membrane in this embodiment includes the following steps: 2g of polyacrylonitrile powder was dissolved in toluene and stirred at high speed for 6 hours at room temperature to prepare a homogeneous spinning solution. The resulting spinning solution was added to an electrospinning apparatus and spun at 15kV to obtain a polymer skeleton. 4g of lithium yttrium bromine electrolyte was weighed and dispersed in anhydrous toluene to obtain a dispersion. The dispersion was cast onto the surface of the polymer skeleton, and the solvent was evaporated under a dry atmosphere to obtain a first composite electrolyte membrane. The first composite electrolyte membrane was placed in a hot press and hot-pressed at 150℃ and 20MPa for 1 hour to obtain a second composite electrolyte membrane. 1g of polyethylene glycol diacrylate monomer, 0.5g of lithium bis(trifluorosulfonyl)imide, 1g of succinic anionyl nitrile, and 20mg of azobisisobutyronitrile were mixed evenly to obtain a gel electrolyte. The gel electrolyte was uniformly sprayed onto the surface of the second composite electrolyte membrane to obtain a third composite electrolyte membrane. The third composite electrolyte membrane was cured under ultraviolet light for 5 minutes to obtain a halide composite solid electrolyte membrane with a thickness of approximately 30μm.

[0029] The solid-state battery fabrication method of this embodiment includes the following steps: The positive electrode material NCM811, binder polyvinylidene fluoride, and conductive agent Super-P were added to N-methylpyrrolidone solvent at a mass ratio of 90:5:5 and dispersed evenly using a planetary stirrer to obtain a positive electrode slurry. The positive electrode slurry was coated onto an aluminum foil current collector and vacuum dried at 80°C for 24 hours to remove residual solvent. After rolling, it was cut to obtain a positive electrode sheet. The above positive electrode sheet, halide composite solid electrolyte membrane, and lithium metal negative electrode were stacked sequentially, and 5 μL of the gel electrolyte prepared in this embodiment was dropped onto each side of the halide composite solid electrolyte membrane to assemble a 2032 type button battery. The assembled battery was heated and cured at 60°C for 3 hours to obtain a solid-state battery.

[0030] Example 2 The example is basically the same as Example 1, except that the halide electrolyte in S2 is replaced with lithium indium chloride electrolyte.

[0031] Example 3 It is basically the same as Example 1, except that the monomer in S4 is replaced with pentaerythritol triacrylate.

[0032] Example 4 The example is basically the same as Example 1, except that the plasticizer succinate in S4 is replaced with the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0033] Example 5 It is basically the same as Example 1, except that the polymer in S1 is replaced with polyethylene oxide and the solvent is adjusted to acetonitrile.

[0034] Example 6 The example is basically the same as Example 1, except that the polymer in S1 is replaced with polyvinylidene fluoride-hexafluoropropylene, and the solvent is adjusted accordingly to N,N-dimethylformamide.

[0035] Example 7 The process is basically the same as in Example 1, except that: the ratio of polyacrylonitrile to lithium yttrium bromide electrolyte is adjusted to 2g:2g; the hot pressing conditions in S3 are adjusted to 100℃, 10MPa, and 0.5h; the gel electrolyte formulation in S4 is adjusted to 0.8g polyethylene glycol diacrylate monomer, 0.4g lithium bis(trifluorosulfonyl)imide, 0.78g succinic anionyl nitrile, and 16mg azobisisobutyronitrile; and the UV curing time in step S5 is adjusted to 3min; the thickness of the halide composite solid electrolyte membrane is approximately 10μm. During battery preparation, the mass ratio of positive electrode material, binder polyvinylidene fluoride, and conductive agent Super-P is adjusted to 85:8:7; the positive electrode slurry is vacuum dried at 60℃ for 36h; the amount of gel electrolyte added to both sides of the electrolyte membrane is adjusted to 2μL each; and the battery is cured at 40℃ for 6h after assembly.

[0036] Example 8 The process is basically the same as in Example 1, except that: the ratio of polyacrylonitrile to lithium yttrium bromide electrolyte is adjusted to 2g:10g; the hot-pressing conditions in S3 are adjusted to 200℃, 50MPa, and 3h; the gel electrolyte formulation in S4 is adjusted to 1.3g polyethylene glycol diacrylate monomer, 0.7g lithium bis(trifluorosulfonyl)imide, 1.3g succinic anionyl nitrile, and 30mg azobisisobutyronitrile; and the UV curing time in step S5 is adjusted to 8min; the thickness of the halide composite solid electrolyte membrane is approximately 50μm. During battery preparation, the mass ratio of positive electrode material, binder polyvinylidene fluoride, and conductive agent Super-P is adjusted to 95:2:3; the positive electrode slurry is vacuum dried at 100℃ for 12h; the amount of gel electrolyte added to both sides of the electrolyte membrane is adjusted to 10μL each; and the battery is cured at 80℃ for 1h after assembly.

[0037] Example 9 The results are basically the same as in Example 1, except that: in S2, the halide electrolyte is replaced with lithium zirconium chloride electrolyte; and in S3, the hot pressing conditions are adjusted to 175°C, 35MPa, and 2h.

[0038] Example 10 The example is basically the same as Example 1, except that the lithium salt in S4 is replaced with lithium bis(fluorosulfonyl)imide and the initiator is replaced with benzophenone.

[0039] Example 11 The process is basically the same as in Example 1, except that: in S1, the polymer is replaced with polymethyl methacrylate and the solvent is adjusted accordingly to dibutyl ether; in S2, the halide electrolyte is replaced with lithium indium bromide electrolyte; in S4, the monomer is replaced with methyl methacrylate, the initiator is replaced with thioxanthone, the lithium salt is replaced with lithium difluorooxalate borate, and the plasticizer is replaced with glutaronitrile.

[0040] Example 12 The process is basically the same as in Example 1, except that: in S1, the polymer is replaced with polyvinylidene fluoride and the solvent is adjusted accordingly to N,N-dimethylformamide; in S4, the monomer is replaced with a mixture of butyl acrylate and trifluoroethyl methacrylate in a mass ratio of 1:1, the initiator is replaced with diimidazole, and the lithium salt is replaced with lithium dioxalatoborate.

[0041] Comparative Example 1 The process is basically the same as in Example 1, except that lithium yttrium bromine electrolyte is not added during the film-making process. Instead, the gel electrolyte is directly sprayed onto the surface of the polymer skeleton obtained by electrospinning, and then cured by ultraviolet light to obtain the electrolyte membrane.

[0042] Comparative Example 2 The process is basically the same as in Example 1, except that: no gel electrolyte was prepared, and the first composite electrolyte membrane was directly used as an electrolyte membrane after being hot-pressed at 150°C and 20MPa for 1 hour. No gel electrolyte was added to either side during battery assembly.

[0043] Comparative Example 3 It is basically the same as Example 1, except that the hot pressing conditions in S3 are adjusted to 80°C, 5MPa, and 0.3h, while the other steps are the same.

[0044] Performance testing The electrolyte membranes and corresponding solid-state batteries prepared in Examples 1-12 and Comparative Examples 1-3 were subjected to the following performance tests.

[0045] 1. Ionic conductivity test: The electrolyte membrane to be tested was cut into circular pieces with a diameter of 16 mm and assembled into a symmetrical blocked battery of stainless steel sheet | electrolyte membrane | stainless steel sheet. The AC impedance spectrum was measured using an electrochemical workstation at 25℃, with a frequency range of 10 Hz. 6 ~0.1Hz, disturbance voltage 5mV. Ionic conductivity is calculated using the following formula: In the formula, σ is the ionic conductivity, L is the electrolyte membrane thickness, R is the bulk impedance obtained by impedance spectrum fitting, and S is the effective contact area between the electrolyte membrane and the stainless steel sheet.

[0046] 2. Air stability test: The electrolyte membrane to be tested was placed in a dry room with a dew point of -40℃ for 24 hours. Then, its ionic conductivity was measured again according to the above method and compared with the initial ionic conductivity to characterize the air stability.

[0047] 3. Electrochemical window test: Assemble a button cell with a stainless steel sheet, electrolyte membrane, and lithium metal structure, and perform linear scan voltammetry on an electrochemical workstation. The scan rate is 1 mV / s, and the voltage scan range is 1 to 6 V. The starting potential at which the current rises significantly is used as the criterion for determining the electrochemical stability window.

[0048] 4. Tensile strength test: Cut the electrolyte membrane to be tested into a strip-shaped sample with a width of 20 mm and a length of 150 mm. Set the initial distance between the clamps of the electronic tensile testing machine to 100 mm. Clamp and fix both ends of the sample in sequence to ensure that the sample and the clamp are in the same vertical direction and there is no obvious pre-stretching. Stretch at a rate of 50 mm / min until the sample breaks. Test each group of samples in parallel three times and take the average value.

[0049] 5. Cycle Capacity Retention Test: The assembled solid-state battery was subjected to a constant current charge-discharge test at 25℃. The charging regime was as follows: constant current charging at 0.2C to 4.2V, then constant voltage charging until the current dropped to 0.01C, followed by a 30-minute rest period. The discharging regime was as follows: constant current discharging at 0.2C to 2.5V, followed by a 30-minute rest period. This cycle was repeated 100 times, and the discharge specific capacity of the first and 100th cycles was recorded. The capacity retention rate was calculated using the following formula: In the formula, η is the capacity retention rate over 100 cycles. The discharge specific capacity at the 100th cycle. This represents the discharge specific capacity during the first cycle.

[0050] The performance test data of each group of electrolyte membranes are shown in Table 1, and the corresponding performance test data of solid-state batteries are shown in Table 2.

[0051] Table 1. Electrolyte Membrane Performance Test Results Table 2 Solid-state battery performance test results Test Result Analysis As can be seen from Examples 1 to 12, the halide composite solid electrolyte membranes prepared by the method described in this invention have room temperature ionic conductivity above 1.8 mS / cm, and remain above 1.5 mS / cm after being placed in a drying room for 24 hours. The electrochemical stability window is not lower than 5.0 V, the tensile strength is not lower than 23.8 MPa, and the capacity retention rate of the assembled solid batteries after 100 cycles is higher than 82%, demonstrating excellent and stable comprehensive performance.

[0052] A comparison of Examples 1 with Examples 2, 9, and 11 shows that different halide electrolytes, such as lithium yttrium bromide, lithium indium chloride, lithium zirconium chloride, and lithium indium bromide, can form stable composite systems with the polymer backbone and gel electrolyte, with the lithium yttrium bromide system exhibiting relatively high ionic conductivity. A comparison of Examples 1 with Examples 5, 6, 11, and 12 shows that polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, and polyvinylidene fluoride can all be used as backbone polymers, and the resulting electrolyte membranes show minimal differences in their properties, indicating that the process described in this invention has good adaptability to different types of backbone polymers.

[0053] A comparison of Examples 1 with Examples 3, 10, 11, and 12 shows that the electrolyte membranes prepared by using different monomers such as polyethylene glycol diacrylate, pentaerythritol triacrylate, methyl methacrylate, butyl acrylate, and a mixture of trifluoroethyl methacrylate, combined with different initiators such as azobisisobutyronitrile, benzophenone, thioxanthone, and diimidazole, and different lithium salts such as lithium bis(trifluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, and lithium dioxalate borate all exhibit good ionic conductivity and electrochemical stability. This further demonstrates that the formulation of the gel electrolyte of the present invention has a wide range of adjustable properties.

[0054] Comparing Examples 1, 7, and 8, it can be seen that when the ratio of polyacrylonitrile to lithium yttrium bromide electrolyte is 2g:2g, the hot-pressing temperature is 100℃, the pressure is 10MPa, the hot-pressing time is 0.5h, the UV curing time is 3min, and the electrolyte membrane thickness is 10μm (Example 7), the ionic conductivity of the prepared electrolyte membrane is 1.86mS / cm and the tensile strength is 24.1MPa. When the above parameters are adjusted to 2g:10g, 200℃, 50MPa, 3h, 8min, and 50μm respectively (Example 8), the ionic conductivity of the prepared electrolyte membrane increases to 2.48mS / cm, the tensile strength increases to 26.7MPa, and the battery capacity retention rate after 100 cycles increases from 83.2% to 89.8%. The above results indicate that the synergistic adjustment of hot-pressing temperature, pressure, time, the ratio of polymer to halide electrolyte, UV curing time, and electrolyte membrane thickness has a significant impact on the densification degree and ion transport path of the composite electrolyte membrane. Under the process parameters described in this invention, halide composite solid electrolyte membranes with good electrochemical and mechanical properties can be obtained.

[0055] Comparing Example 1 with Comparative Example 1, it can be seen that without the introduction of a halide electrolyte, the ionic conductivity of the resulting electrolyte membrane significantly decreased to 0.66 mS / cm, and the electrochemical window also decreased from 5.2 V to 4.5 V, indicating that the halide electrolyte plays a crucial role in improving the ion transport capacity and oxidative stability of the composite electrolyte membrane. Comparing Example 1 with Comparative Example 2, it can be seen that without the gel electrolyte layer, the ionic conductivity of the electrolyte membrane dropped sharply from 0.84 mS / cm to 0.16 mS / cm after being placed in a drying room for 24 hours, and the tensile strength was only 18.7 MPa. After 100 cycles, the capacity retention rate was only 57.9%, indicating that the gel electrolyte layer played an important role in blocking environmental moisture, improving interfacial contact, and maintaining mechanical integrity. Comparing Example 1 with Comparative Example 3, it can be seen that the composite electrolyte membrane had insufficient densification, and all electrochemical and mechanical properties decreased significantly. The above results demonstrate that by organically combining electrospinning, hot pressing, and in-situ photocuring processes, and by rationally controlling the formulation of each component and process parameters, this invention can prepare a halide composite solid electrolyte membrane with high ionic conductivity, a wide electrochemical window, good air stability, and excellent mechanical properties.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for preparing a halide composite solid electrolyte membrane, characterized in that, Includes the following steps: S1: Dissolve the polymer in an organic solvent, stir at high speed to form a uniform spinning solution, and then prepare a polymer skeleton with a porous fiber structure by electrospinning. S2: Disperse the halide electrolyte in an organic solvent to obtain a dispersion, cast the dispersion onto the polymer backbone, and dry to obtain a first composite electrolyte membrane; S3: The first composite electrolyte membrane is hot-pressed to obtain the second composite electrolyte membrane; S4: Mix monomers, initiators, lithium salts and plasticizers evenly to prepare a gel electrolyte, and spray the gel electrolyte onto the surface of the second composite electrolyte membrane to obtain a third composite electrolyte membrane; S5: The third composite electrolyte membrane is cured under ultraviolet light to obtain a halide composite solid electrolyte membrane.

2. The method for preparing a halide composite solid electrolyte membrane according to claim 1, characterized in that, In step S1, the polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile, and polyvinylidene fluoride.

3. The method for preparing a halide composite solid electrolyte membrane according to claim 1, characterized in that, In step S2, the halide electrolyte is selected from one or more of lithium yttrium bromide electrolyte, lithium indium chloride electrolyte, lithium indium bromide electrolyte, and lithium zirconium chloride electrolyte; The organic solvent is selected from one or more of anhydrous acetonitrile, N,N-dimethylformamide, toluene, and dibutyl ether.

4. The method for preparing a halide composite solid electrolyte membrane according to claim 1, 2, or 3, characterized in that, In step S3, the first composite electrolyte membrane is hot-pressed at a temperature of 100-200°C and a pressure of 10-50 MPa for a time of 0.5-3 hours.

5. The method for preparing a halide composite solid electrolyte membrane according to claim 1, 2, or 3, characterized in that, In step S4, the monomer is selected from one or more of butyl acrylate, polyethylene glycol diacrylate, methyl methacrylate, trifluoroethyl methacrylate, and pentaerythritol triacrylate. The initiator is selected from one or more of azobisisobutyronitrile, benzophenone, thioxanthones, and diimidazole; The lithium salt is selected from one or more of lithium bis(trifluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, and lithium dioxalate borate. The plasticizer is selected from one or more of succinic anion, glutaronitrile, imidazole ionic liquid, piperidine ionic liquid, pyrrole ionic liquid and pyridine ionic liquid.

6. The method for preparing a halide composite solid electrolyte membrane according to claim 1, 2, or 3, characterized in that, In step S5, the curing time under ultraviolet light is 3 to 8 minutes; the thickness of the halide composite solid electrolyte membrane is 10 to 50 μm.

7. The method for preparing a halide composite solid electrolyte membrane according to claim 1, 2, or 3, characterized in that, The mass ratio of polymer to halide electrolyte in the first composite electrolyte membrane is 1:1 to 1:5; the mass ratio of gel electrolyte to halide electrolyte in the third composite electrolyte membrane is 1:1 to 1:

3.

8. A halide composite solid electrolyte membrane, characterized in that, The halide composite solid electrolyte membrane is prepared by the preparation method described in any one of claims 1 to 7.

9. The halide composite solid electrolyte membrane according to claim 8, characterized in that, The halide composite solid electrolyte membrane has an ionic conductivity of not less than 1×10⁻⁶ at 25°C. -3 S / cm, electrochemical stability window not less than 5.0V, tensile strength not less than 23MPa.

10. A solid-state battery, characterized in that, It includes a positive electrode, a negative electrode, and a halide composite solid electrolyte membrane as described in claim 8 or 9, wherein the halide composite solid electrolyte membrane is disposed between the positive electrode and the negative electrode, and gel electrolyte is provided on both sides of the halide composite solid electrolyte membrane.

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