A composite electrolyte membrane for solid-state batteries and a method for preparing the same

Abstract

The application discloses a composite electrolyte film for a solid-state battery and a preparation method thereof, and belongs to the technical field of composite electrolyte films for solid-state batteries. The composite electrolyte film comprises, in sequence along the thickness direction, a positive electrode side matching layer, a gradient main conduction layer and a negative electrode side cross-linking stable interface layer, wherein the gradient main conduction layer is composed of a second film layer and a third film layer, both of which contain a polymer matrix composed of triacetate cellulose and polyvinylidene hexafluoropropylene, modified garnet type inorganic electrolyte particles and lithium salt, and the content of the modified garnet type inorganic electrolyte particles and the lithium salt in the third film layer is higher than that in the second film layer; a transition connection area containing part of the modified garnet type inorganic electrolyte particles is arranged between the third film layer and a fourth film layer. The composite electrolyte film is beneficial to improving the stability of the positive and negative electrode interfaces, improving the continuity of ion transmission in the film body, and giving consideration to high-temperature dimensional stability and cycle use safety.

Description

Technical Field

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

[0002] With the development of high-energy-density secondary batteries, replacing traditional liquid electrolytes with solid-state electrolytes has become an important direction for improving battery safety and energy density. Existing solid-state electrolytes mainly include inorganic solid-state electrolytes, polymer solid-state electrolytes, and composite solid-state electrolytes. Among them, polymer solid-state electrolytes have advantages such as good film-forming properties, high flexibility, and good interfacial contact, while garnet-type inorganic electrolytes have high room-temperature ionic conductivity and good electrochemical stability. Combining the two is beneficial for balancing ion transport and mechanical properties. CN121149390B points out that polymer solid-state electrolytes have good processability, interfacial contact, flexibility, and mechanical strength, but commonly used polymer systems still have insufficient high-temperature strength under high-rate charge-discharge and high-temperature conditions. CN120473556A further points out that although the combination of garnet-type LLZTO and polymers is beneficial for enhancing chain segment movement and promoting lithium salt dissociation, the inadequate compatibility between the inorganic phase and the polymer matrix easily leads to particle agglomeration, reduced interfacial contact area, and reduced lithium-ion transport channels.

[0003] Chinese patent CN121149390B discloses a composite solid electrolyte membrane, its preparation method, and its application. The membrane comprises a first layer, a second layer, and a third layer stacked sequentially. Both the first and second layers contain a polymer, a solid electrolyte, and a lithium salt, with the second layer having a higher content of solid electrolyte and lithium salt than the first layer. The third layer is an interface layer, and the polymer is formed from cellulose triacetate and polyvinylidene fluoride hexafluoropropylene. This design improves high-temperature resistance and ion transport performance by setting a double-layer gradient main membrane and a single-sided interface layer. However, this invention mainly focuses on the gradient transport within the membrane and the stability of the single-sided interface. Its ability to simultaneously address the high-voltage interface on the positive electrode side and the deposition / stripping interface on the negative electrode side remains limited. Furthermore, it lacks further targeted design to address the interfacial continuity and dispersion uniformity of garnet-type inorganic particles in the polymer matrix.

[0004] Chinese patent CN120473556A discloses a modified composite solid electrolyte, its preparation method, and its application. This method uses polyethylene oxide as a matrix, in which garnet-type Li₂ is dispersed. 6.4 La3Zr 1.4 Ta 0.6 O 12Nanoparticles were introduced, and amphiphilic block copolymers were incorporated between the inorganic electrolyte and the polymer matrix to improve the compatibility of the inorganic-organic interface, inhibit LLZTO particle aggregation, and form multi-channel lithium-ion transport. However, this invention mainly addresses the particle dispersion and interface compatibility issues in monolayer composite solid electrolyte systems. It still falls short in terms of the partitioned construction of the composite electrolyte membrane in the thickness direction, the synergistic consideration of the different interface requirements on both sides of the positive and negative electrodes, and the overall improvement of the membrane's thermal stability and interface stability.

[0005] Therefore, how to provide a composite electrolyte membrane for solid-state batteries and its preparation method to solve or overcome the technical problems in existing composite solid-state electrolyte membranes, such as the difficulty in simultaneously addressing the positive and negative electrode interfaces, insufficient continuity of ion transport within the membrane, and the tendency of garnet-type inorganic particles to agglomerate, leading to increased interfacial impedance, and to improve interface stability, ion transport performance, and high-temperature safety, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the problems of existing composite solid electrolyte membranes, such as the lack of effective partitioning in the thickness direction, difficulty in synergistically improving the stability of the positive and negative electrode interfaces, and insufficient dispersion and interfacial continuity of inorganic electrolyte particles in the polymer matrix, this invention provides a composite electrolyte membrane for solid-state batteries and its preparation method.

[0007] In a first aspect, the present invention provides a composite electrolyte membrane for solid-state batteries, comprising a first membrane layer, a second membrane layer, a third membrane layer and a fourth membrane layer stacked sequentially along the thickness direction; The first film layer is a positive electrode side matching layer with a thickness of 1-5 μm. The first film layer includes a polyether polymer, a lithium salt, and a positive electrode side stabilizing component.

[0008] The second and third membrane layers are gradient main conductive layers. Both the second and third membrane layers include a polymer matrix, modified garnet-type inorganic electrolyte particles, and lithium salt. Based on the total mass of the second membrane layer, the modified garnet-type inorganic electrolyte particles account for 12-25%, and the lithium salt accounts for 8-18%. Based on the total mass of the third membrane layer, the modified garnet-type inorganic electrolyte particles account for 26-45%, and the lithium salt accounts for 20-35%. The fourth film layer is a cross-linked stable interface layer on the negative electrode side with a thickness of 1-8 μm. The fourth film layer includes a cross-linked polymer network formed by polymerizing polyether polymerizable monomers, zwitterionic monomers and boron-containing cross-linked monomers, as well as lithium salt. A transition connection region with a thickness of 0.5-5 μm is provided between the third membrane layer and the fourth membrane layer, and the transition connection region contains partially modified garnet-type inorganic electrolyte particles embedded in the fourth membrane layer; The polymer matrix is ​​composed of cellulose triacetate and polyvinylidene fluoride-hexafluoropropylene, and based on the total mass of the second or third film layer, cellulose triacetate accounts for 5-15%, polyvinylidene fluoride-hexafluoropropylene accounts for 15-35%, and the balance is other necessary additives.

[0009] This invention constructs a partitioned composite structure along the thickness direction, consisting of a matching layer on the positive electrode side, a main conductive layer, and a stable interface on the negative electrode side. This allows the composite electrolyte membrane to perform different mass transfer and stabilization functions at different interface locations. The first membrane layer is arranged on the positive electrode side, forming a contact region with more moderate composition and properties between the high-voltage positive electrode and the intermediate main conductive layer. This helps to reduce the impedance increase caused by local side reactions on the positive electrode side and uneven interface contact. The second and third membrane layers employ a gradient distribution of modified garnet-type inorganic electrolyte particles and lithium salts. The third membrane layer, closer to the negative electrode side, has a further increased content of inorganic lithium-conducting phase and lithium salt, creating a continuous lithium-conducting environment from low to high along the membrane thickness direction. This mitigates the problems of abrupt ion pathway changes, insufficient local transport, and concentration polarization concentration in traditional uniform membrane layers. Simultaneously, the polymer matrix composed of cellulose triacetate and polyvinylidene fluoride-hexafluoropropylene balances the membrane layer's heat resistance and flexible contact capabilities, allowing the inorganic lithium-conducting phase to maintain good dispersion while co-constructing a stable composite conductive network with the polymer phase. The fourth membrane layer is located on the negative electrode side and is continuously connected to the third membrane layer through a transition connection region. This allows some of the modified garnet-type inorganic electrolyte particles in the main conductive layer to extend to the interface region on the negative electrode side. This helps to mitigate abrupt changes in interlayer properties, stabilize the ion flux distribution on the negative electrode side, and reduce the risk of continuous growth in interface impedance and uneven local deposition. As a result, it helps to simultaneously improve the interface stability, ion transport performance, and high-temperature safety of the composite electrolyte membrane.

[0010] Preferably, the other necessary additives are at least one of dispersants, plasticizers, and leveling agents.

[0011] Preferably, the mass fractions of the modified garnet-type inorganic electrolyte particles and the lithium salt in the third membrane layer are 1.5-3 times that of the corresponding components in the second membrane layer.

[0012] By further increasing the content of inorganic lithium-conducting phase and lithium salt in the third film layer, a higher density of ion transport nodes and a more abundant source of migratable lithium ions can be formed in the region near the negative electrode, thereby establishing a more defined and continuous gradient lithium-conducting environment between the second and third film layers. This gradient relationship helps to mitigate the local polarization caused by abrupt changes in transport capacity along the film thickness direction, allowing for a smoother transport transition of lithium ions from the positive to the negative electrode side. On the other hand, the higher content of inorganic lithium-conducting phase and lithium salt near the negative electrode side helps to enhance the ion supply capacity near the interface, reducing the tendency for local ion depletion and uneven deposition on the negative electrode side, thus helping to balance the continuity of conduction within the film and the stability of the negative electrode side interface.

[0013] Preferably, the garnet-type inorganic electrolyte particles are selected from Li7La3Zr2O 12 Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li 6.4 La3Zr 1.4 Nb 0.6 O 12 Li 6.25 Al 0.25 La3Zr2O 12 and Li 6.25 Ga 0.25 La3Zr2O 12 At least one of the following, wherein the particle size D50 of the garnet-type inorganic electrolyte particles is 100-800 nm.

[0014] Preferably, the modified garnet-type inorganic electrolyte particles include garnet-type inorganic electrolyte particles and an ion-directing shell coating their surface. The thickness of the ion-directing shell is 5-60 nm, and the mass of the ion-directing shell is 0.5-8% of the mass of the garnet-type inorganic electrolyte particles. The ion-directing shell includes silane anchoring segments and polymeric segments containing lithium sulfonyl imide groups, and the silane anchoring segments are connected to the surface of the garnet-type inorganic electrolyte particles.

[0015] After adopting the above-mentioned modified garnet-type inorganic electrolyte particles, the interface between the garnet-type inorganic electrolyte particles and the polymer matrix is ​​transformed from a single inorganic contact interface into a composite interface with transition characteristics. This helps to reduce the tendency of particles to agglomerate during film preparation and subsequent use, and improves the dispersion uniformity and interfacial bonding stability of the inorganic lithium-conducting phase in the film. At the same time, the ion-directing shell on the particle surface can provide a more continuous ion migration transition region between the inorganic phase and the polymer phase, making the transport of lithium ions around the particles and near the phase interface smoother, thereby reducing interfacial transport resistance and improving the continuity of the lithium-conducting network inside the film.

[0016] Preferably, the positive electrode side stabilizing component in the first membrane layer is selected from at least one of 3,4,9,10-perylenetetracarboxylic dianhydride, triphenyl phosphate, triethyl phosphate, and trimethyl phosphate.

[0017] Preferably, the polyether polymer in the first film layer is selected from at least one of polyethylene oxide, polyethylene glycol diacrylate, and polyethylene glycol methyl ether acrylate; and the polyether polymerizable monomer in the fourth film layer is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate, and polypropylene glycol diacrylate.

[0018] Preferably, the zwitterionic monomer is selected from at least one of sulfobetaine methacrylate, carboxybetaine methacrylate and phosphorylcholine methacrylate, and the boron-containing crosslinking monomer is an acrylate monomer containing boron ester groups.

[0019] Secondly, the present invention also provides a method for preparing the composite electrolyte membrane for solid-state batteries, comprising the following steps: S1. Garnet-type inorganic electrolyte particles are reacted with a silane coupling agent containing hydrolyzable alkoxysilane groups and carbon-carbon double bonds to obtain pretreated particles; then the pretreated particles are grafted with a vinyl monomer containing lithium sulfonylimide groups to obtain modified garnet-type inorganic electrolyte particles. S2. Cellulose triacetate, polyvinylidene fluoride-hexafluoropropylene, lithium salt, the modified garnet-type inorganic electrolyte particles and solvent are respectively formulated into a second slurry and a third slurry, and respectively cast and dried to obtain the second film layer and the third film layer. S3. After stacking the second film layer and the third film layer, hot press and anneal to obtain an intermediate laminated film; S4. A positive electrode precursor liquid containing polyether polymer, lithium salt and positive electrode side stabilizing component is coated onto the side of the second film layer away from the third film layer and cured to obtain the first film layer. S5. A negative electrode-side precursor liquid containing polyether polymerizable monomers, zwitterionic monomers, boron-containing crosslinking monomers, lithium salts and initiators is coated onto the side of the third film layer away from the second film layer and cured, so that the negative electrode-side precursor liquid wets the surface of the third film layer and coats part of the modified garnet-type inorganic electrolyte particles on the surface of the third film layer, forming a transition connection region after curing, thus obtaining the fourth film layer.

[0020] Preferably, in step S3, the hot pressing temperature is 110-130℃, the hot pressing pressure is 6-15MPa, the hot pressing time is 2-10min, the annealing temperature is 130-170℃, and the annealing time is 0.5-3h; the curing in steps S4 and S5 is UV curing or heat curing, and after curing, it is vacuum dried at 40-80℃ for 2-12h.

[0021] Thirdly, the present invention also provides a solid-state battery, comprising a positive electrode, a negative electrode, and the aforementioned composite electrolyte membrane.

[0022] The composite electrolyte membrane for solid-state batteries and its preparation method provided by this invention have at least the following beneficial effects: (1) This invention constructs a positive electrode matching layer, a gradient main conduction layer, and a negative electrode cross-linked stable interface layer sequentially along the thickness direction, and sets a transition connection region on the negative electrode side, so that the composite electrolyte membrane forms a partitioned synergistic structure at the high voltage interface on the positive electrode side, the ion transport region inside the membrane, and the deposition and stripping interface on the negative electrode side. Among them, the positive electrode matching layer helps to mitigate the interface contact difference between the positive electrode and the main conduction layer and reduce local side reactions under high voltage conditions. The second and third membrane layers form a continuous lithium-conducting environment through the gradient distribution of modified garnet-type inorganic electrolyte particles and lithium salt, which helps to reduce the transport abrupt change and concentration polarization in the thickness direction. The negative electrode cross-linked stable interface layer and the transition connection region between it and the third membrane layer help to stabilize the ion flux distribution on the negative electrode side, reduce the interface impedance growth and local deposition unevenness, thereby achieving simultaneous improvement of interface stability, ion transport performance and high temperature safety.

[0023] (2) In the preferred embodiment, the mass fraction of modified garnet-type inorganic electrolyte particles and lithium salt in the third membrane layer is 1.5-3 times that of the corresponding components in the second membrane layer. This is beneficial for forming a higher density of ion transport nodes and a more sufficient supply of lithium ions in the region near the negative electrode side, further enhancing the lithium conduction continuity of the gradient main conduction layer. At the same time, the use of modified garnet-type inorganic electrolyte particles, including garnet-type inorganic electrolyte particles and ion-directing shell layers, can form a more stable composite interface between the inorganic phase and the polymer phase, reduce particle agglomeration and improve the uniformity of interface dispersion. In addition, the silane anchoring segments and the polymer segments containing lithium sulfonyl imide groups in the shell layer are beneficial for building a more continuous ion migration transition region around the particles, thereby taking into account the dispersion stability, interface matching and lithium conduction efficiency of the inorganic lithium conduction phase. Furthermore, the introduction of the positive electrode side stabilizing component, zwitterionic monomer and boron-containing crosslinking monomer is also beneficial for improving the interface stability on the positive electrode side and the interface stabilization capability on the negative electrode side, respectively, so that the composite electrolyte membrane maintains good working stability at both interfaces.

[0024] (3) The preparation method of the present invention involves surface pretreatment and graft polymerization modification of garnet-type inorganic electrolyte particles, followed by the preparation of gradient main conductive layers and hot pressing and annealing. Subsequently, a matching layer on the positive electrode side and a cross-linked stable interface layer on the negative electrode side are constructed on both sides, which can conveniently realize the synergistic construction of multilayer structure, composition gradient and transition connection region. The preparation process is clear in layers and the parameters are easy to control, which is conducive to improving the bonding stability between each film layer and the overall structural integrity, reducing the problems of interlayer delamination, interface abruptness and local defect accumulation, thereby facilitating the acquisition of a composite electrolyte membrane with good film-forming properties, interface stability and lithium conduction performance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the composite electrolyte membrane in an embodiment of the present invention; Figure 2 This is a graph showing the ionic conductivity data at 25°C for embodiments and comparative examples of the present invention; Figure 3 This is a graph showing lithium-ion transport number data for embodiments and comparative examples of the present invention; Figure 4 This is a graph showing the heat shrinkage rate at 150°C for embodiments and comparative examples of the present invention; Figure 5 The critical current density data diagrams for embodiments and comparative examples of the present invention are shown. Figure 6 This is a graph showing the 200-week capacity retention rate data for embodiments and comparative examples of the present invention.

[0026] Explanation of reference numerals in the attached figures: 1. First membrane layer; 2. Second membrane layer; 3. Third membrane layer; 4. Transition connection region; 5. Fourth membrane layer. Detailed Implementation

[0027] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0029] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0030] like Figure 1 As shown, the present invention provides a composite electrolyte membrane, specifically comprising: (1) First membrane layer 1. The first membrane layer 1 is disposed on the side of the composite electrolyte membrane near the positive electrode, serving as the positive electrode-side matching layer, with a thickness of 1-5 μm. The first membrane layer 1 is mainly used to construct an interface transition region with relatively mild composition and properties between the high-voltage positive electrode and the intermediate main conductive layer, so as to reduce the increase in interface impedance caused by local side reactions and uneven solid-solid contact on the positive electrode side. The first membrane layer 1 includes a polyether polymer, a lithium salt, and a positive electrode-side stabilizing component, wherein the polyether polymer can be polyethylene oxide, and the positive electrode-side stabilizing component can be used to improve the interface stability on the positive electrode side and suppress adverse reactions under high voltage conditions.

[0031] In one preferred embodiment, the positive electrode side stabilizing component in the first membrane layer 1 is selected from at least one of 3,4,9,10-perylenetetracarboxylic dianhydride, triphenyl phosphate, triethyl phosphate, and trimethyl phosphate.

[0032] In one preferred embodiment, the polyether phase in the first film layer 1 may also be formed by curing at least one of polyethylene glycol diacrylate and polyethylene glycol methyl ether acrylate, thereby improving the bonding stability between the layer and the underlying main conductive layer while maintaining the lithium-conducting characteristics of the polyether.

[0033] In a more preferred embodiment, the lithium salt in the first film layer 1 is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalateborate, so as to balance the ion supply on the positive electrode side and the interface stability.

[0034] (2) Second film layer 2. The second film layer 2 is disposed between the first film layer 1 and the third film layer 3. It is a gradient main conductive layer near the positive electrode and mainly serves to connect with the first film layer 1, provide flexible support, and provide a primary lithium conduction pathway. The second film layer 2 includes a polymer matrix, modified garnet-type inorganic electrolyte particles, and lithium salt. Based on the total mass of the second film layer 2, the modified garnet-type inorganic electrolyte particles account for 12-25%, and the lithium salt accounts for 8-18%. The polymer matrix is ​​composed of cellulose triacetate and polyvinylidene fluoride-hexafluoropropylene. Based on the total mass of the second film layer 2, cellulose triacetate accounts for 5-15%, polyvinylidene fluoride-hexafluoropropylene accounts for 15-35%, and the remainder is other necessary additives. The other necessary additives are mainly auxiliary components used for dispersion, leveling, plasticizing, and film formation. Their total amount is preferably such that it does not damage the continuity of the film layer and the construction of the lithium conduction network. In one preferred embodiment, the garnet-type inorganic electrolyte particles are selected from Li7La3Zr2O. 12 Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li 6.4 La3Zr 1.4 Nb 0.6 O 12 Li6.25 Al 0.25 La3Zr2O 12 And Li 6.25 Ga 0.25 La3Zr2O 12 At least one of them, wherein the median particle size D50 is 100-800 nm.

[0035] In one preferred embodiment, the modified garnet-type inorganic electrolyte particles include garnet-type inorganic electrolyte particles and an ion-guiding shell coating the surface thereof. The thickness of the ion-guiding shell is 5-60 nm, and the mass of the ion-guiding shell is 0.5-8% of the mass of the garnet-type inorganic electrolyte particles.

[0036] In a more preferred embodiment, the ion-directing shell includes silane anchoring segments and polymeric segments containing lithium sulfonyl imide groups, wherein the silane anchoring segments are connected to the surface of garnet-type inorganic electrolyte particles to improve the bonding stability between the shell and the inorganic particles and to construct an interface transition region on the particle surface that is conducive to lithium ion migration.

[0037] (3) Third film layer 3. The third film layer 3 is disposed between the second film layer 2 and the fourth film layer 5. It is a gradient main conductive layer near the negative electrode side and mainly undertakes the role of constructing the dominant lithium pathway inside the film and transitioning lithium to the negative electrode side. The third film layer 3 also includes a polymer matrix, modified garnet-type inorganic electrolyte particles and lithium salt; based on the total mass of the third film layer 3, the modified garnet-type inorganic electrolyte particles account for 26-45% and the lithium salt accounts for 20-35%. The polymer matrix is ​​also composed of cellulose triacetate and polyvinylidene fluoride-hexafluoropropylene. Based on the total mass of the third film layer 3, cellulose triacetate accounts for 5-15%, polyvinylidene fluoride-hexafluoropropylene accounts for 15-35%, and the remainder is other necessary additives. Compared with the second film layer 2, the content of inorganic lithium-conducting phase and lithium salt in the third film layer 3 is further increased to form a higher lithium-conducting density region near the negative electrode side.

[0038] In one preferred embodiment, the mass fractions of modified garnet-type inorganic electrolyte particles and lithium salt in the third film layer 3 are 1.5-3 times that of the corresponding components in the second film layer 2, thereby creating a more defined gradient lithium-conducting environment in the film thickness direction.

[0039] In a more preferred embodiment, the second film layer 2 and the third film layer 3 use the same type of garnet-type inorganic electrolyte particles and the same type of polymer matrix. The gradient main conductive layer is constructed only by the difference in the content of inorganic lithium-conducting phase and lithium salt, so as to alleviate the interface discontinuity problem caused by the abrupt change in the material system between the layers.

[0040] (4) Fourth membrane layer 5. The fourth membrane layer 5 is disposed on the side of the composite electrolyte membrane near the negative electrode and is a cross-linked stable interface layer on the negative electrode side, with a thickness of 1-8 μm. The fourth membrane layer 5 includes a cross-linked polymer network formed by polymerizing polyether polymerizable monomers, zwitterionic monomers and boron-containing cross-linking monomers, as well as lithium salt. This layer is mainly used to improve the wetting and contact state of the negative electrode side interface, stabilize the ion flux distribution on the negative electrode side, and reduce the tendency of continuous increase in the interface impedance and uneven local deposition on the negative electrode side.

[0041] In one more preferred embodiment, the fourth film layer 5 is composed of polyethylene glycol diacrylate, sulfobetaine methacrylate, tris(2-acryloyloxyethyl)borate, and lithium bis(fluorosulfonyl)imide. Polyethylene glycol diacrylate, as a polyether polymerizable monomer, has the general structural formula CH2=CH-COO-(CH2CH2O). n -OCO-CH=CH2, where n is the repeating number of the polyethylene glycol segment; sulfobetaine methacrylate, as an amphoteric monomer, has the structural formula CH2=C(CH3)COOCH2CH2N+(CH3)2CH2CH2CH2SO3−; tris(2-acryloyloxyethyl)boronic acid ester, as a boron-containing crosslinking monomer, has the structural formula B(OCH2CH2OCOCH=CH2)3; lithium bis(fluorosulfonyl)imide, as a lithium salt, has the chemical formula LiN(SO2F)2.

[0042] In a further embodiment, the fourth film layer 5 can be formed by the polymerization reaction of the aforementioned polyethylene glycol diacrylate, sulfobetaine methacrylate, and tris(2-acryloyloxyethyl)boronic acid ester under the action of an initiator to form a cross-linked polymer network, and lithium bis(fluorosulfonyl)imide is dispersed in the cross-linked polymer network, thereby constituting a cross-linked stable interface layer on the negative electrode side. Specifically, polyethylene glycol diacrylate provides polyether segments and cross-linkable double bonds, sulfobetaine methacrylate introduces an amphoteric structure, and tris(2-acryloyloxyethyl)boronic acid ester introduces boron-containing cross-linking nodes. Together, these three components form a negative electrode side polymer network structure with a certain degree of flexibility and interfacial stability.

[0043] (5) Transition Connection Region 4. A transition connection region 4 is provided between the third film layer 3 and the fourth film layer 5. The thickness of the transition connection region 4 is 0.5-5 μm, and it contains some modified garnet-type inorganic electrolyte particles embedded in the fourth film layer 5. The transition connection region 4 is mainly used to form a continuous transition in composition and structure between the third film layer 3 and the fourth film layer 5, and to reduce the interface abrupt change when transitioning from the main conductive layer to the negative electrode side stable interface layer. By allowing some of the modified garnet-type inorganic electrolyte particles in the third film layer 3 to extend into the fourth film layer 5, a certain inorganic lithium conduction node can be retained in the starting region of the fourth film layer 5, thereby improving the bonding stability and ion migration continuity between the third film layer 3 and the fourth film layer 5.

[0044] In one preferred embodiment, the transition connection region 4 is formed by wetting and coating the surface of the third film layer 3 with the precursor liquid of the fourth film layer 5.

[0045] In a more preferred embodiment, the distribution of modified garnet-type inorganic electrolyte particles in the transition connection region 4 gradually decreases from the third film layer 3 to the fourth film layer 5, in order to further mitigate the abrupt interface change.

[0046] The present invention also provides a method for preparing the above-mentioned composite electrolyte membrane for solid-state batteries, specifically including the following steps: S1. Preparation of modified garnet-type inorganic electrolyte particles: Garnet-type inorganic electrolyte particles were dispersed in an organic solvent, followed by the addition of a surface-modifying agent to initiate a surface reaction. The reaction temperature was controlled at 50-90℃, and the reaction time was 2-8 hours to introduce anchoring sites on the particle surface for further reaction. After the reaction, the particles were filtered, washed, and dried to obtain pretreated particles. The pretreated particles were then added to a polymerization reaction system for graft polymerization, with the polymerization temperature controlled at 60-85℃ and the polymerization time controlled at 4-12 hours. After the reaction, the particles were washed, separated, and vacuum dried to obtain modified garnet-type inorganic electrolyte particles.

[0047] In one preferred embodiment, the dispersion treatment employs a combination of ultrasonic dispersion and mechanical stirring, with ultrasonic time ranging from 10 to 60 minutes and mechanical stirring time ranging from 0.5 to 2 hours.

[0048] In a more preferred embodiment, the vacuum drying temperature is 50-90°C and the drying time is 6-24 hours.

[0049] Preparation of S2, second film layer 2 and third film layer 3: The components used to form the second film layer 2 and the third film layer 3 were separately prepared into a second slurry and a third slurry. The slurries were mixed uniformly using stirring and high-shear dispersion methods. The stirring temperature was 50-80℃, the stirring time was 4-8 hours, the high-shear dispersion speed was 3000-12000 rpm, and the dispersion time was 0.5-2 hours. Subsequently, degassing treatment was performed on each slurry for 10-60 minutes. The degassed second and third slurries were then cast into films with a wet film thickness controlled at 20-100 μm. After casting, the films were pre-dried at 60-100℃ for 2-12 hours to obtain the second film layer 2 and the third film layer 3.

[0050] In one preferred embodiment, the casting method is either blade casting or slot coating.

[0051] In a more preferred embodiment, vacuum drying is performed after pre-drying to further reduce the residual solvent content.

[0052] S3, Formation of the intermediate laminate.

[0053] The second film layer 2 and the third film layer 3 are stacked in a predetermined direction and then hot-pressed to ensure tight adhesion between the two layers and reduce interlayer porosity. The hot-pressing temperature is 110-130℃, the hot-pressing pressure is 6-15MPa, and the hot-pressing time is 2-10min. After hot-pressing, annealing is performed at 130-170℃ for 0.5-3h to improve the structural stability and interlayer bonding strength of the intermediate laminated film.

[0054] In one preferred embodiment, the film layer is pre-aligned and lightly pressed before hot pressing to reduce misalignment during the hot pressing process.

[0055] In a more preferred embodiment, the intermediate laminate is vacuum dried after annealing at a temperature of 40-100°C for 2-24 hours.

[0056] S4. Construction of the first membrane layer 1.

[0057] The precursor solution on the positive electrode side is coated onto the side of the second film layer 2 away from the third film layer 3, and then cured to form the first film layer 1. The coating method is blade coating, spray coating, slot coating, or spin coating, and the coating thickness is controlled to be 1-10 μm. The curing method is ultraviolet curing or thermal curing; wherein the ultraviolet curing time is 10s-10min, the thermal curing temperature is 50-120℃, and the thermal curing time is 5min-6h. After curing, it is vacuum dried at 40-80℃ for 2-12h to obtain the first film layer 1.

[0058] In one preferred embodiment, the actual thickness of the first film layer 1 after curing is controlled to be 1-5 μm.

[0059] In a more preferred embodiment, the surface of the intermediate laminate is subjected to dust removal or surface activation treatment before coating to improve the bonding stability between the first film layer 1 and the second film layer 2.

[0060] Construction of S5, fourth membrane layer 5 and transition connection region 4.

[0061] The precursor solution on the negative electrode side is coated onto the side of the third film layer 3 away from the second film layer 2, and the wetting depth of the precursor solution on the surface of the third film layer 3 is controlled to coat part of the modified garnet-type inorganic electrolyte particles on the surface of the third film layer 3. Subsequently, it is cured to form the fourth film layer 5 and the transition connection region 4 located between the third film layer 3 and the fourth film layer 5. The coating method is blade coating, spray coating, slot coating, or spin coating, and the coating thickness is controlled to be 1-15 μm. The curing method is UV curing or thermal curing, wherein the UV curing time is 10s-10min, the thermal curing temperature is 50-120℃, and the thermal curing time is 5min-6h. After curing, it is vacuum dried at 40-80℃ for 2-12h to obtain the fourth film layer 5, and a transition connection region 4 with a thickness of 0.5-5 μm is formed between it and the third film layer 3.

[0062] In one preferred embodiment, the wetting time of the precursor liquid on the negative electrode side is 10s-30min to control the formation range of the transition connection region 4.

[0063] In a more preferred embodiment, by adjusting the viscosity of the precursor liquid, the coating amount and the curing start time, the transition connection zone 4 is mainly confined to the surface area of ​​the third film layer 3, so as to avoid excessive penetration and affect the main structure of the third film layer 3.

[0064] Example 1

[0065] The following materials are used in this embodiment: The raw materials used to prepare modified garnet-type inorganic electrolyte particles include: Li 6.4 La3Zr 1.4 Ta 0.6 O 12 5.00g of granules, 0.15g of methacryloyloxypropyltrimethoxysilane, 0.18g of vinyl monomer containing lithium sulfonylimide group, and 0.01g of azobisisobutyronitrile.

[0066] The raw materials used to prepare the first film layer include: 0.75 g of polyethylene glycol diacrylate, 0.30 g of LiTFSI, 0.15 g of 3,4,9,10-perylenetetracarboxylic dianhydride, and 0.03 g of photoinitiator.

[0067] The raw materials used to prepare the second membrane layer include: 0.80 g of cellulose triacetate, 2.20 g of polyvinylidene fluoride-hexafluoropropylene, 1.80 g of modified garnet-type inorganic electrolyte particles, 1.20 g of LiTFSI, 3.20 g of succinic acid, and 0.80 g of fluoroethylene carbonate.

[0068] The raw materials used to prepare the third membrane layer include: 0.80 g of cellulose triacetate, 2.00 g of polyvinylidene fluoride-hexafluoropropylene, 3.20 g of modified garnet-type inorganic electrolyte particles, 2.40 g of LiTFSI, 1.20 g of succinic acid, and 0.40 g of fluoroethylene carbonate.

[0069] The raw materials used to prepare the fourth film layer include: 0.72g of polyethylene glycol diacrylate, 0.32g of sulfobetaine methacrylate, 0.16g of acrylate monomers containing borate ester groups, 0.36g of LiFSI, and 0.04g of photoinitiator.

[0070] 2. Preparation method S1. Preparation of modified garnet-type inorganic electrolyte particles.

[0071] 5.00g Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The particles were added to 100 mL of anhydrous ethanol, ultrasonically dispersed for 20 min, and then mechanically stirred for 40 min. 0.15 g of methacryloyloxypropyltrimethoxysilane was added, and the mixture was reacted at 70 °C for 4 h. After the reaction, the mixture was filtered, washed three times with anhydrous ethanol, and vacuum dried at 80 °C for 10 h to obtain pretreated particles. The pretreated particles were then added to 60 mL of dimethylformamide, along with 0.18 g of a vinyl monomer containing a lithium sulfonylimide group and 0.01 g of azobisisobutyronitrile (AIBN), and reacted at 75 °C for 8 h under nitrogen protection. After the reaction, the mixture was filtered, washed, and vacuum dried at 80 °C for 12 h to obtain modified garnet-type inorganic electrolyte particles. The ion-directed shell thickness of these particles was controlled to be approximately 20 nm, and the shell mass was approximately 3.0% of the particle mass.

[0072] Preparation of S2, the second film layer and the third film layer.

[0073] The cellulose triacetate and polyvinylidene fluoride-hexafluoropropylene required for the second film layer were added to 18.00 g of NMP and stirred at 70 °C for 6 h to ensure complete dissolution. Modified garnet-type inorganic electrolyte particles were added and dispersed under high shear at 8000 rpm for 40 min. LiTFSI, succinate, and fluoroethylene carbonate were then added, and stirring was continued for 2 h. Vacuum degassing was performed for 20 min to obtain the second slurry. The second slurry was coated onto a PET release film with a wet film thickness of 150 μm, pre-dried at 80 °C for 4 h, and then vacuum dried at 70 °C for 8 h to obtain the second film layer.

[0074] The preparation method of the third slurry is the same, except that the raw material of the third film layer is added to 20.00g NMP to make the slurry; the third slurry is coated with a wet film thickness of 180μm, pre-dried at 80℃ for 4h, and then vacuum dried at 70℃ for 8h to obtain the third film layer.

[0075] S3, Formation of the intermediate laminate.

[0076] The second and third film layers were stacked in a predetermined direction, with the third film layer located near the negative electrode. The layers were hot-pressed at 120°C and 10 MPa for 5 minutes, followed by annealing at 150°C for 1 hour to obtain the intermediate laminated film. After annealing, the film was vacuum-dried at 80°C for 6 hours.

[0077] S4. Construction of the first membrane layer.

[0078] Polyethylene glycol diacrylate, LiTFSI, 3,4,9,10-perylenetetracarboxylic dianhydride, and a photoinitiator were added to 8.00 g of acetonitrile and stirred for 1 h to obtain the positive electrode precursor solution. The positive electrode precursor solution was coated onto the side of the second film layer away from the third film layer with a wet film thickness of 12 μm. It was cured under 365 nm ultraviolet light for 60 s and then vacuum dried at 60 °C for 4 h to obtain the first film layer with a dry film thickness of approximately 3 μm.

[0079] Construction of S5, the fourth membrane layer, and the transition connection region.

[0080] Polyethylene glycol diacrylate, sulfobetaine methacrylate, acrylate monomers containing borate ester groups, LiFSI, and a photoinitiator were added to 8.00 g of acetonitrile and stirred for 1 h to obtain the negative electrode side precursor solution. The negative electrode side precursor solution was coated onto the side of the third film layer away from the second film layer with a wet film thickness of 15 μm. It was allowed to stand for 90 s to wet the surface of the third film layer, then cured under 365 nm UV light for 90 s, and vacuum dried at 60 °C for 6 h to obtain the fourth film layer. During this process, the negative electrode side precursor solution coated part of the modified garnet-type inorganic electrolyte particles on the surface of the third film layer, forming a transition region of approximately 2 μm thickness between the third and fourth film layers.

[0081] Example 2

[0082] This embodiment differs from Embodiment 1 in that it employs a different gradient composition and a thinner ion-directing shell. Specifically, the amount of vinyl monomer containing lithium sulfonyl imide groups in S1 is changed to 0.06g, resulting in an ion-directing shell thickness of approximately 8nm and a shell mass of approximately 0.8% of the particle mass. The raw materials for the second membrane layer are changed to: 0.70g triacetate cellulose, 1.80g polyvinylidene fluoride-hexafluoropropylene, 1.20g modified garnet-type inorganic electrolyte particles, 0.80g LiTFSI, 4.80g succinate, and 0.70g fluoroethylene carbonate. The raw materials for the third membrane layer are changed to: 0.70g triacetate cellulose, 1.80g polyvinylidene fluoride-hexafluoropropylene, 2.60g modified garnet-type inorganic electrolyte particles, 2.00g LiTFSI, 2.30g succinate, and 0.60g fluoroethylene carbonate. All other components remain the same.

[0083] Example 3

[0084] This embodiment differs from Embodiment 1 in that it employs a different gradient composition and a thicker ion-directing shell. Specifically, in S1, the amount of methacryloyloxypropyltrimethoxysilane is changed to 0.25g, and the amount of vinyl monomer containing lithium sulfonylimide groups is changed to 0.32g. The resulting ion-directing shell is approximately 55nm thick, and its mass is approximately 6.5% of the particle mass. The raw materials for the second membrane layer are changed to: 0.60g of cellulose triacetate, 1.80g of polyvinylidene fluoride-hexafluoropropylene, 2.50g of modified garnet-type inorganic electrolyte particles, 1.80g of LiTFSI, 2.30g of succinic anion, and 1.00g of fluoroethylene carbonate. The raw materials for the third membrane layer are changed to: 0.50g of cellulose triacetate, 1.50g of polyvinylidene fluoride-hexafluoropropylene, 4.50g of modified garnet-type inorganic electrolyte particles, and 3.50g of LiTFSI. The rest remains the same.

[0085] Example 4

[0086] The difference between this embodiment and Embodiment 1 is that the garnet-type inorganic electrolyte particles are made of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Change to Li7La3Zr2O 12 The particle types in S1 are replaced accordingly, while the rest remain the same.

[0087] Example 5

[0088] The difference between this embodiment and Embodiment 1 is that the positive electrode stabilizing component in the first membrane layer is changed from 0.15g of 3,4,9,10-perylenetetracarboxylic dianhydride to 0.15g of triphenyl phosphate. All other components remain the same.

[0089] Example 6

[0090] The difference between this embodiment and Example 1 is that the monomer system in the fourth film layer is changed to 0.40g of polyethylene glycol methyl ether acrylate, 0.32g of polypropylene glycol diacrylate, 0.32g of carboxybetaine methacrylate, 0.16g of acrylate monomers containing borate ester groups, 0.36g of LiFSI, and 0.04g of photoinitiator. All other components remain the same.

[0091] Example 7

[0092] The difference between this embodiment and Embodiment 1 lies in the process parameters. Specifically, in S3, the hot-pressing temperature is changed to 110℃, the hot-pressing pressure to 6MPa, and the hot-pressing time to 2min; the annealing temperature is changed to 130℃, and the annealing time to 0.5h. In S4 and S5, the UV curing time is changed to 30s, and the vacuum drying conditions are changed to 40℃ and 2h. The rest remain the same.

[0093] Example 8

[0094] The difference between this embodiment and Embodiment 1 lies in the process parameters. Specifically, in S3, the hot-pressing temperature is changed to 130℃, the hot-pressing pressure to 15MPa, and the hot-pressing time to 10min; the annealing temperature is changed to 170℃, and the annealing time to 3h. In S4 and S5, the curing method is changed to thermosetting, with curing conditions of 100℃ and 2h, and vacuum drying conditions of 80℃ and 12h. The rest remain the same.

[0095] Comparative Example 1 The difference between this comparative example and Example 1 is that the first film layer is not provided. Specifically, S4 in Example 1 is omitted, while the rest remains the same.

[0096] Comparative Example 2 The difference between this comparative example and Example 1 is that no gradient difference is set between the second and third membrane layers. Specifically, the second and third membrane layers use the same raw material composition and preparation conditions as the second membrane layer in Example 1, with the rest remaining the same.

[0097] Comparative Example 3 The difference between this comparative example and Example 1 is that the garnet-type inorganic electrolyte particles are not surface modified. Specifically, the surface reaction and graft polymerization steps are omitted in S1, and unmodified Li is directly added to the second and third film layers, respectively. 6.4 La3Zr 1.4 Ta 0.6 O 12 The amount of granules added is the same as in Example 1, and everything else remains the same.

[0098] Comparative Example 4 The difference between this comparative example and Example 1 is that no transition connection region is formed. Specifically, in S5, the amount of acetonitrile in the negative electrode side precursor solution is reduced from 8.00g to 2.00g, and the coating is immediately cured under 365nm ultraviolet light for 10s to prevent significant wetting; the rest remains the same.

[0099] Test methods 1. Ionic conductivity (mS / cm): The electrochemical impedance spectroscopy was used to measure the conductivity by clamping the membrane sample between the blocking electrodes and measuring the electrochemical impedance spectrum at 25°C. The volume resistance was read and the ionic conductivity was calculated by combining the membrane thickness and effective area.

[0100] 2. Lithium-ion transference number: Measured using a combined potentiostatic polarization-AC impedance method. A Li|electrolyte membrane|Li symmetric cell was assembled, a small voltage bias was applied, and the changes in current and impedance before and after polarization were recorded. The lithium-ion transference number was then calculated.

[0101] 3. Heat shrinkage rate (%): Referring to GB / T36363, the film sample was cut into a fixed size, placed at 150℃ for 30 min, and the dimensional changes before and after heating were measured and the heat shrinkage rate was calculated.

[0102] 4. Critical current density (mA / cm²): Tested using the lithium-ion symmetric battery stepped current density method. A Li|electrolyte membrane|Li symmetric battery was assembled using the composite electrolyte membrane, starting from 0.25 mA / cm². 2 The current density is gradually increased, and the test is conducted under fixed areal capacity deposition / stripping conditions. The current density corresponding to the stage before the voltage drop or short circuit is recorded as the critical current density.

[0103] 5. Cycle capacity retention (%): Tested using the room temperature cycling method. At 25℃, the battery was charged to 4.2V using a constant current and constant voltage of 0.5C, with a cutoff current of 0.01C, and then discharged to 3.0V using 0.5C. The cycle capacity retention was calculated as the ratio of the discharge capacity at week 200 to the discharge capacity at week 1. This test procedure is consistent with the full-cell cycle evaluation approach used in the uploaded basic three-layer membrane patent.

[0104] Test Results The test results of Examples 1-8 and Comparative Examples 1-4 are shown in Table 1 and Figure 2-6 As shown:

[0105] As shown in Table 1, the ionic conductivity of Example 1 at 25°C was 0.52 mS / cm, the lithium-ion transference number was 0.63, the thermal shrinkage rate at 150°C was 3.9%, and the critical current density was 1.05 mA / cm. 2 The capacity retention rate after 200 cycles was 95.2%. Compared to Comparative Example 1, with only the first film layer removed, the cycle capacity retention rate of Example 1 increased from 89.8% to 95.2%, and the critical current density increased from 0.89 mA / cm². 2 Increased to 1.05 mA / cm 2This indicates that the first film layer is beneficial for improving the stability of the cathode side interface and enhancing long-cycle performance. Compared with Comparative Example 2, after eliminating the gradient difference between the second and third film layers, the ionic conductivity decreased from 0.52 mS / cm to 0.41 mS / cm, the lithium-ion transference number decreased from 0.63 to 0.51, and the 200-cycle capacity retention decreased from 95.2% to 88.6%, indicating that the gradient main conductive layer is beneficial for improving the continuity of ion transport in the film thickness direction and reducing polarization. Compared with Comparative Example 3, without surface modification of the garnet-type inorganic electrolyte particles, the ionic conductivity decreased from 0.52 mS / cm to 0.39 mS / cm, the lithium-ion transference number decreased from 0.63 to 0.46, and the critical current density decreased from 1.05 mA / cm. 2 It dropped to 0.68 mA / cm 2 This indicates that modified garnet-type inorganic electrolyte particles are beneficial for improving the interfacial continuity between the inorganic phase and the polymer matrix, as well as the lithium conduction efficiency. Compared with Comparative Example 4, without the formation of a transition region, the critical current density increased from 1.05 mA / cm². 2 It dropped to 0.76 mA / cm 2 The capacity retention rate decreased from 95.2% to 90.2% after 200 weeks, indicating that the transition region between the third and fourth membrane layers is beneficial for mitigating interface abrupt changes and stabilizing the ion flux distribution on the negative electrode side.

[0106] In summary, the present invention achieves good overall performance in terms of ion transport performance, interface stability and high-temperature dimensional stability through the synergistic construction of the first membrane layer, the second membrane layer, the third membrane layer, the fourth membrane layer and the transition connection region.

[0107] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A composite electrolyte membrane for solid-state batteries, characterized in that, It includes a first film layer (1), a second film layer (2), a third film layer (3) and a fourth film layer (5) stacked sequentially along the thickness direction; The first film layer (1) is a positive electrode side matching layer with a thickness of 1-5 μm. The first film layer (1) includes a polyether polymer, a lithium salt and a positive electrode side stabilizing component. The second membrane layer (2) and the third membrane layer (3) are gradient main conductive layers. Both the second membrane layer (2) and the third membrane layer (3) include a polymer matrix, modified garnet-type inorganic electrolyte particles and lithium salt. Based on the total mass of the second membrane layer (2), the modified garnet-type inorganic electrolyte particles account for 12-25% and the lithium salt accounts for 8-18%. Based on the total mass of the third membrane layer (3), the modified garnet-type inorganic electrolyte particles account for 26-45% and the lithium salt accounts for 20-35%. The fourth film layer (5) is a cross-linked stable interface layer on the negative electrode side with a thickness of 1-8 μm. The fourth film layer (5) includes a cross-linked polymer network formed by polymerizing polyether polymerizable monomers, zwitterionic monomers and boron-containing cross-linked monomers, as well as lithium salt. A transition connection region (4) with a thickness of 0.5-5 μm is provided between the third membrane layer (3) and the fourth membrane layer (5), and the transition connection region (4) contains partially modified garnet-type inorganic electrolyte particles embedded in the fourth membrane layer (5); The polymer matrix is ​​composed of cellulose triacetate and polyvinylidene fluoride-hexafluoropropylene, and based on the total mass of the second film layer (2) or the third film layer (3), cellulose triacetate accounts for 5-15%, polyvinylidene fluoride-hexafluoropropylene accounts for 15-35%, and the remainder is other necessary additives.

2. The composite electrolyte membrane for solid-state batteries according to claim 1, characterized in that, The mass fractions of the modified garnet-type inorganic electrolyte particles and lithium salt in the third membrane layer (3) are 1.5-3 times that of the corresponding components in the second membrane layer (2).

3. The composite electrolyte membrane for solid-state batteries according to claim 1, characterized in that, The garnet-type inorganic electrolyte particles are selected from Li7La3Zr2O 12 Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li 6.4 La3Zr 1.4 Nb 0.6 O 12 Li 6.25 Al 0.25 La3Zr2O 12 and Li 6.25 Ga 0.25 La3Zr2O 12 At least one of the following, wherein the particle size D50 of the garnet-type inorganic electrolyte particles is 100-800 nm.

4. The composite electrolyte membrane for solid-state batteries according to claim 1, characterized in that, The modified garnet-type inorganic electrolyte particles include garnet-type inorganic electrolyte particles and an ion-directing shell coating their surface. The thickness of the ion-directing shell is 5-60 nm, and the mass of the ion-directing shell is 0.5-8% of the mass of the garnet-type inorganic electrolyte particles. The ion-directing shell includes silane anchoring segments and polymeric segments containing lithium sulfonyl imide groups, and the silane anchoring segments are connected to the surface of the garnet-type inorganic electrolyte particles.

5. The composite electrolyte membrane for solid-state batteries according to claim 1, characterized in that, The positive electrode side stabilizing component in the first membrane layer (1) is selected from at least one of 3,4,9,10-perylenetetracarboxylic dianhydride, triphenyl phosphate, triethyl phosphate and trimethyl phosphate.

6. The composite electrolyte membrane for solid-state batteries according to claim 1, characterized in that, The polyether polymer in the first film layer (1) is selected from at least one of polyethylene oxide, polyethylene glycol diacrylate and polyethylene glycol methyl ether acrylate; the polyether polymerizable monomer in the fourth film layer (5) is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate and polypropylene glycol diacrylate.

7. The composite electrolyte membrane for solid-state batteries according to claim 1, characterized in that, The zwitterionic monomer is selected from at least one of sulfobetaine methacrylate, carboxybetaine methacrylate and phosphorylcholine methacrylate, and the boron-containing crosslinking monomer is an acrylate monomer containing boron ester groups.

8. A method for preparing a composite electrolyte membrane for a solid-state battery according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Garnet-type inorganic electrolyte particles are reacted with a silane coupling agent containing hydrolyzable alkoxysilane groups and carbon-carbon double bonds to obtain pretreated particles; then the pretreated particles are grafted with a vinyl monomer containing lithium sulfonylimide groups to obtain modified garnet-type inorganic electrolyte particles. S2. Cellulose triacetate, polyvinylidene fluoride-hexafluoropropylene, lithium salt, the modified garnet-type inorganic electrolyte particles and solvent are respectively prepared into a second slurry and a third slurry, and respectively cast and dried to obtain a second film layer (2) and a third film layer (3). S3. After stacking the second film layer (2) and the third film layer (3), hot press and anneal to obtain an intermediate laminated film; S4. A positive electrode precursor liquid containing a polyether polymer, lithium salt and a positive electrode stabilizing component is coated onto the side of the second film layer (2) away from the third film layer (3) and cured to obtain a first film layer (1). S5. A negative electrode precursor liquid containing polyether polymerizable monomers, zwitterionic monomers, boron-containing crosslinking monomers, lithium salts and initiators is coated on the side of the third film layer (3) away from the second film layer (2) and cured, so that the negative electrode precursor liquid wets the surface of the third film layer (3) and coats part of the modified garnet-type inorganic electrolyte particles on the surface of the third film layer (3), forming a transition connection region (4) after curing, and obtaining the fourth film layer (5).

9. The preparation method according to claim 8, characterized in that, In step S3, the hot pressing temperature is 110-130℃, the hot pressing pressure is 6-15MPa, the hot pressing time is 2-10min, the annealing temperature is 130-170℃, and the annealing time is 0.5-3h; the curing in steps S4 and S5 is UV curing or heat curing, and after curing, it is vacuum dried at 40-80℃ for 2-12h.

10. A solid-state battery, characterized in that, It includes a positive electrode, a negative electrode, and the composite electrolyte membrane according to any one of claims 1-7.

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