A sandwich structure polymer-based solid electrolyte and its preparation method and application

Abstract

The present invention provides a sandwich-structured polymer-based solid electrolyte, its preparation method, and application, comprising a first solid electrolyte layer, a second solid electrolyte layer, and a third solid electrolyte layer located between the first and second solid electrolyte layers; the content of the inorganic filler in the third solid electrolyte layer is higher than that in the first solid electrolyte layer; the content of the inorganic filler in the third solid electrolyte layer is higher than that in the second solid electrolyte layer; the inorganic filler in the third solid electrolyte layer comprises a first inorganic filler and a second inorganic filler, the particle size of the first inorganic filler being smaller than that of the second inorganic filler. The present invention helps to improve mechanical properties, effectively alleviate the problem of lithium dendrites, and help improve cycle performance and interface issues.

Description

Technical Field

[0001] The present invention relates to a sandwich structure polymer-based solid electrolyte and a preparation method and application thereof, belonging to the technical field of solid electrolytes. Background Art

[0002] Quality and safety issues have recently become prominent in the new energy industry. For example, South Korea's energy storage power plants have repeatedly experienced fires and explosions, leading to stagnation and restructuring of the industry. Fires at energy storage power plants in the United States have also had a significant impact on American society and industry. Liquid electrolytes, 80% of which are flammable organic solvents, pose serious safety risks to batteries (such as lithium-ion batteries). Solid-state batteries, on the other hand, lack free electrolytes and offer significant safety advantages and potential, making them a necessary step forward in battery development.

[0003] The core of solid-state batteries is the solid electrolyte. Among solid-state electrolytes, polymer solid electrolytes and oxide solid electrolytes have the advantages of good flexibility, excellent interface contact and high ionic conductivity, respectively, and have good application prospects. However, the low conductivity of polymer solid electrolytes and the fragility of oxide solid electrolytes limit their application. The preparation of composite solid electrolytes by combining polymer solid electrolytes and oxide solid electrolytes has become a new direction in the research of solid-state electrolytes. However, this composite solid electrolyte still has the problem of difficult to control thickness. The flexibility, mechanical properties and conductivity of the single-layer polymer / oxide composite solid electrolyte cannot meet the requirements at the same time, which further affects the electrical properties of the solid-state battery, such as interface contact and cycle life.

[0004] Therefore, there is an urgent need to develop a solid electrolyte that can help improve performance such as interface contact and cycle life. Summary of the Invention

[0005] The present invention provides a sandwich structure polymer-based solid electrolyte and its preparation method and application, which has high mechanical properties, effectively improves the lithium dendrite problem, and helps to improve cycle performance and interface problems.

[0006] The present invention provides a sandwich-structured polymer-based solid electrolyte, comprising a first solid electrolyte layer, a second solid electrolyte layer, and a third solid electrolyte layer located between the first and second solid electrolyte layers; the content of the inorganic filler in the third solid electrolyte layer is higher than the content of the inorganic filler in the first solid electrolyte layer; the content of the inorganic filler in the third solid electrolyte layer is higher than the content of the inorganic filler in the second solid electrolyte layer; the inorganic filler in the third solid electrolyte layer comprises a first inorganic filler and a second inorganic filler, and the particle size of the first inorganic filler is smaller than the particle size of the second inorganic filler.

[0007] Optionally, the ratio of the particle size of the first inorganic filler to the particle size of the second inorganic filler is 1:(1-1000), and the ratio of the particle size of the first inorganic filler to the particle size of the second inorganic filler is not 1.

[0008] Optionally, the particle size of the first inorganic filler is 10 to 500 nm, and the particle size of the second inorganic filler is 1 to 10 μm.

[0009] Optionally, the mass ratio of the first inorganic filler to the second inorganic filler is (1-2):(2-10).

[0010] Optionally, the first solid electrolyte layer includes 40% to 100% of the first polymer, 0% to 60% of the inorganic filler, and 1% to 10% of the first lithium salt in terms of mass percentage; the second solid electrolyte layer includes 40% to 100% of the third polymer, 0% to 60% of the inorganic filler, and 1% to 10% of the third lithium salt in terms of mass percentage; the third solid electrolyte layer includes 25% to 100% of the second polymer, 0% to 75% of the inorganic filler, and 1% to 10% of the second lithium salt in terms of mass percentage.

[0011] Optionally, the inorganic filler includes one or more of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium lanthanum zirconium titanium oxide, aluminum oxide, silicon oxide, hafnium oxide, and barium titanate; and / or, the first inorganic filler and the second inorganic filler each independently include one or more of aluminum oxide, silicon oxide, hafnium oxide, and barium titanate.

[0012] The present invention also provides a method for preparing the sandwich structure polymer-based solid electrolyte as described above, comprising: mixing a first polymer, an inorganic filler, a first lithium salt and a first solvent, and performing a first grinding to obtain a first solid electrolyte slurry; coating the first solid electrolyte slurry on a substrate, and performing a first drying to obtain a first solid electrolyte layer; mixing a second polymer, an inorganic filler, a second lithium salt and a second solvent, and performing a second grinding to obtain a second solid electrolyte slurry; coating the second solid electrolyte slurry on a substrate, and performing a second drying to obtain a second solid electrolyte layer; mixing a third polymer, the first inorganic filler, the second inorganic filler, a third lithium salt and a third solvent; Mixing to obtain a third solid electrolyte slurry; coating the third solid electrolyte slurry on a substrate, and after a third drying, obtaining the third solid electrolyte layer; the sum of the added amounts of the first inorganic filler and the second inorganic filler is higher than the added amount of the inorganic filler in the first solid electrolyte layer, and the sum of the added amounts of the first inorganic filler and the second inorganic filler is higher than the added amount of the inorganic filler in the second solid electrolyte layer; stacking the first solid electrolyte layer, the third solid electrolyte layer, and the second solid electrolyte layer in sequence, and pressing them at 80-120 MPa and 160-200° C. to obtain the sandwich structure polymer-based solid electrolyte.

[0013] Optionally, during the first grinding process, the first grinding process is performed at a rotation speed of 80 to 120 rpm for 8 to 12 minutes, then at a rotation speed of 480 to 520 rpm for 18 to 22 minutes, and finally at a rotation speed of 780 to 820 rpm for 38 to 42 minutes; and / or, the first solid electrolyte slurry is coated on the substrate, and after the first drying, the process of obtaining the first solid electrolyte layer includes: removing bubbles in the first solid electrolyte slurry, coating 8 to 12 mL of the first solid electrolyte slurry after removing bubbles on a plane area of ​​380 to 420 cm 2 The first solid electrolyte layer is obtained after the first drying at 58-62°C on the substrate; and / or, during the second grinding process, the first grinding is performed at a rotation speed of 80-120rpm for 8-12min, then at a rotation speed of 480-520rpm for 18-22min, and finally at a rotation speed of 780-820rpm for 38-42min; and / or, the second solid electrolyte slurry is coated on the substrate, and after the second drying, the second solid electrolyte layer is obtained, which comprises: removing bubbles in the second solid electrolyte slurry, and then coating 8-12mL of the second solid electrolyte slurry after removing bubbles on a plane area of ​​380-420cm 2The second solid electrolyte layer is obtained after the second drying at 58-62° C. on the substrate; and / or the third solid electrolyte slurry is coated on the substrate, and after the third drying, the third solid electrolyte layer is obtained, the process comprising: removing bubbles in the third solid electrolyte slurry, coating 8-12 mL of the third solid electrolyte slurry after removing bubbles on a plane area of ​​380-420 cm 2 The substrate is coated with a film and dried for the second time at 58-62° C. to obtain the third solid electrolyte layer.

[0014] Optionally, the first polymer, the second polymer, and the third polymer each independently include one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer, and polyvinylidene fluoride-trifluoroethylene copolymer; and / or the first lithium salt, the second lithium salt, and the third lithium salt each independently include one or more of lithium bis(trifluoromethanesulfonyl)imide and lithium hexafluorophosphate.

[0015] The present invention also provides a solid-state battery, comprising the sandwich structure polymer-based solid electrolyte as described above or the sandwich structure polymer-based solid electrolyte obtained according to the preparation method as described above.

[0016] The present invention provides a sandwich-structured polymer-based solid electrolyte, a preparation method thereof, and an application thereof, which have high mechanical properties and high density, effectively improving the problem of lithium dendrites, and have controllable thickness, low thermal shrinkage, and high ionic conductivity, effectively solving interface problems and improving cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : is the discharge energy retention rate curve of the solid-state battery of Example 1;

[0018] Figure 2 : is the discharge energy retention rate curve of the solid-state battery of Example 2;

[0019] Figure 3 : is the discharge energy retention rate curve of the solid-state battery of Example 3;

[0020] Figure 4 1 is the discharge energy retention rate curve of the solid-state battery of Comparative Example 1;

[0021] Figure 5 2 is the discharge energy retention rate curve of the solid-state battery of Comparative Example 2;

[0022] Figure 6 3 is the discharge energy retention rate curve of the solid-state battery of Comparative Example 3;

[0023] Figure 7 Schematic diagram of the structure of a sandwich-structured polymer-based solid electrolyte in some embodiments. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0025] An embodiment of the present invention provides a sandwich-structured polymer-based solid electrolyte, comprising a first solid electrolyte layer, a second solid electrolyte layer, and a third solid electrolyte layer located between the first and second solid electrolyte layers; the content of the inorganic filler in the third solid electrolyte layer is higher than the content of the inorganic filler in the first solid electrolyte layer; the content of the inorganic filler in the third solid electrolyte layer is higher than the content of the inorganic filler in the second solid electrolyte layer; the inorganic filler in the third solid electrolyte layer comprises a first inorganic filler and a second inorganic filler, and the particle size of the first inorganic filler is smaller than the particle size of the second inorganic filler.

[0026] According to the inventor's research and analysis: the third solid electrolyte layer of the sandwich structure polymer-based solid electrolyte contains more inorganic fillers, that is, the middle solid electrolyte layer contains more inorganic fillers, which helps to enhance the mechanical properties of the sandwich structure polymer-based solid electrolyte and inhibit lithium dendrites from piercing the electrolyte, while the first solid electrolyte layer and the second solid electrolyte layer contain less inorganic fillers, that is, the solid electrolyte layers on both sides contain less inorganic fillers, which helps to improve the interface contact problem between the solid electrolyte and the positive and negative electrodes; in addition, the third solid electrolyte layer (middle layer) includes two inorganic fillers with different particle sizes (first filler and second filler), and the inorganic filler with small particle size can fill the gaps of the inorganic filler with large particle size, reducing the probability of lithium dendrites piercing from the gaps, and can further enhance the mechanical properties of the solid electrolyte, prevent lithium dendrites from penetrating the solid electrolyte, thereby preventing short circuits and improving cycle performance.

[0027] Therefore, the sandwich structure polymer-based solid electrolyte provided by the embodiment of the present invention has high mechanical properties, which effectively improves the lithium dendrite problem and helps to improve the cycle performance and interface problems.

[0028] The ratio of the particle size of the first inorganic filler to the particle size of the second inorganic filler may be 1:(1-1000), and the ratio of the particle size of the first inorganic filler to the particle size of the second inorganic filler is not 1.

[0029] Furthermore, the particle size ratio of the first filler to the second filler can be (1-50): (100-1000), for example, 1:100, 10:200, 15:400, 20:500:40:700, 1:1000. The inorganic filler with a small particle size can better fill the gaps of the inorganic filler with a large particle size, thereby reducing the probability of lithium dendrites piercing through the gaps. It can also further enhance the mechanical properties of the solid electrolyte, prevent lithium dendrites from penetrating the solid electrolyte, thereby preventing short circuits and improving cycle performance.

[0030] In some embodiments, the particle size of the first inorganic filler is 10 to 500 nm, for example, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm or a range consisting of any two thereof, and the second inorganic filler is 1 to 10 μm, for example, 1 μm, 5 μm, 8 μm, 10 μm or a range consisting of any two thereof. Inorganic fillers with small particle sizes can better fill the gaps of inorganic fillers with large particle sizes, reduce the probability of lithium dendrites piercing through the gaps, and further enhance the mechanics of the solid electrolyte, prevent lithium dendrites from penetrating the solid electrolyte, thereby preventing short circuits and improving cycle performance.

[0031] The mass ratio of the first inorganic filler to the second inorganic filler can be (1-2): (2-10), for example, 1:1, 1:2, 1:5, 1:10 or a range consisting of any two of them. The inorganic filler with a small particle size can better fill the gaps of the inorganic filler with a large particle size, reduce the probability of lithium dendrites piercing through the gaps, and further enhance the mechanics of the solid electrolyte, preventing lithium dendrites from penetrating the solid electrolyte, thereby preventing short circuits and improving cycle performance.

[0032] In some embodiments, the first solid electrolyte layer includes, by weight, 40% to 100% of the first polymer, 0% to 60% of the inorganic filler, and 1% to 10% of the first lithium salt.

[0033] The above-mentioned first polymer may include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer (P(VDF-TrFE-CTFE)), and polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)). In specific implementation, the same polymer as the binder in the electrode plate (such as the positive electrode plate) can be selected to help improve the interface contact problem and improve the ionic conductivity. Among them, P(VDF-TrFE-CTFE) has a high dielectric constant, provides a lithium ion percolation channel, improves ionic conductivity, and has strong mechanical properties, inhibits lithium dendrite puncture, and helps improve cycle performance.

[0034] The inorganic filler in the first solid electrolyte layer is hereinafter referred to as the third inorganic filler, and the third inorganic filler may include one or more of lithium aluminum titanium phosphide oxide (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), and lithium lanthanum zirconium titanium oxide (LLZTO).

[0035] The first lithium salt may include one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium hexafluorophosphate.

[0036] Furthermore, in the first lithium salt, the mass ratio of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to lithium hexafluorophosphate can be 10:(3-4), for example, 10:3, 10:3.2, 10:3.5, 10:4 or a range consisting of any two thereof.

[0037] In some embodiments, the second solid electrolyte layer includes, by weight, 40% to 100% of the second polymer, 0% to 60% of the inorganic filler, and 1% to 10% of the second lithium salt.

[0038] The above-mentioned second polymer may include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer (P(VDF-TrFE-CTFE)), and polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)). In specific implementation, a polymer that combines well with the electrode pole piece (such as the negative electrode pole piece) can be selected to help improve the interface contact problem and improve the ionic conductivity. Among them, P(VDF-TrFE-CTFE) has a high dielectric constant, provides a lithium ion percolation channel, improves ionic conductivity, and has strong mechanical properties, inhibits lithium dendrite puncture, and helps improve cycle performance.

[0039] The inorganic filler in the second solid electrolyte layer is hereinafter referred to as a fourth inorganic filler. The fourth inorganic filler may include one or more of aluminum oxide, silicon oxide, and hafnium oxide.

[0040] The second lithium salt may include one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium hexafluorophosphate.

[0041] Furthermore, in the second lithium salt, the mass ratio of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to lithium hexafluorophosphate can be 10:(3-4), for example, 10:3, 10:3.2, 10:3.5, 10:4 or a range consisting of any two thereof.

[0042] In some embodiments, the third solid electrolyte layer includes, by mass percentage, 25% to 100% of a third polymer, 0% to 75% of an inorganic filler (including a first inorganic filler and a second inorganic filler), and 1% to 10% of a third lithium salt.

[0043] The third polymer may include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer (P(VDF-TrFE-CTFE)), and polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)). P(VDF-TrFE-CTFE) has a high dielectric constant, provides a lithium ion percolation channel, improves ionic conductivity, and has strong mechanical properties, inhibits lithium dendrite penetration, and helps improve cycle performance.

[0044] The first inorganic filler and the second inorganic filler each independently include one or more of aluminum oxide (Al2O3), silicon oxide, and hafnium oxide.

[0045] The third lithium salt may include one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium hexafluorophosphate.

[0046] Furthermore, in the second lithium salt, the mass ratio of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to lithium hexafluorophosphate can be 10:(3-4), for example, 10:3, 10:3.2, 10:3.5, 10:4 or a range consisting of any two thereof.

[0047] Figure 7 Schematic diagram of the structure of a sandwich-structured polymer-based solid electrolyte in some embodiments.

[0048] An embodiment of the present invention also provides a method for preparing the above-mentioned sandwich structure polymer-based solid electrolyte, comprising: mixing a first polymer, an inorganic filler, a first lithium salt and a first solvent, and obtaining a first solid electrolyte slurry after a first grinding; coating the first solid electrolyte slurry on a substrate, and obtaining a first solid electrolyte layer after a first drying; mixing a second polymer, an inorganic filler, a second lithium salt and a second solvent, and obtaining a second solid electrolyte slurry after a second grinding; coating the second solid electrolyte slurry on a substrate, and obtaining a second solid electrolyte layer after a second drying; mixing a third polymer, a first inorganic filler, a second inorganic filler, A third lithium salt and a third solvent are mixed to obtain a third solid electrolyte slurry; the third solid electrolyte slurry is coated on a substrate, and after a third drying, a third solid electrolyte layer is obtained; the sum of the added amounts of the first inorganic filler and the second inorganic filler is higher than the added amount of the inorganic filler in the first solid electrolyte layer, and the sum of the added amounts of the first inorganic filler and the second inorganic filler is higher than the added amount of the inorganic filler in the second solid electrolyte layer; the first solid electrolyte layer, the third solid electrolyte layer, and the second solid electrolyte layer are stacked in sequence and pressed at 80-120 MPa and 160-200° C. to obtain a sandwich structure polymer-based solid electrolyte.

[0049] According to the inventor's research and analysis: by adding more inorganic fillers to the third solid electrolyte layer (middle layer) of the sandwich structure polymer-based solid electrolyte, it is helpful to enhance the mechanical properties of the sandwich structure polymer-based solid electrolyte and inhibit lithium dendrites from piercing the electrolyte, while adding less inorganic fillers to the first solid electrolyte layer and the second solid electrolyte layer (two side layers), that is, the solid electrolyte layers on both sides contain less inorganic fillers, which helps to improve the interface contact problem between the solid electrolyte and the positive and negative electrodes and improve the ionic conductivity; the third solid electrolyte layer (middle layer) includes two inorganic fillers of different particle sizes (first filler and second filler), and the inorganic filler with a small particle size can fill the gaps of the inorganic filler with a large particle size, thereby reducing the probability of lithium dendrites piercing through the gaps, and can also Further enhance the mechanical properties of the solid electrolyte, prevent lithium dendrites from penetrating the solid electrolyte, thereby preventing short circuits and improving cycle performance (cycle life). In addition, the above-mentioned preparation method obtains three electrolyte layers by coating (solution casting or pouring), and then stacks and presses the three electrolyte layers (folding and hot pressing). By regulating the coating amount and the content of polymer (organic polymer) and inorganic filler, a sandwich structure polymer-based solid electrolyte (organic-inorganic hybrid polymer electrolyte or film) with a thickness of 5 to 50 μm can be obtained, which is convenient for regulating the thickness of the sandwich structure polymer-based solid electrolyte and further reducing the thickness of the sandwich structure polymer-based solid electrolyte, thereby solving the problem of difficult control of the thickness of the solid electrolyte and the interface problem at the same time.

[0050] In some embodiments, the first solvent includes N-methylpyrrolidone and / or dimethylformamide (DMF) or dimethylacetamide (DMAc).

[0051] In some embodiments, during the first grinding process, the rotation speed can be firstly 80-120 rpm, for example, 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm or any two thereof, for grinding for 8-12 min, for example, 8 min, 9 min, 10 min, 11 min, 12 min or any two thereof, and then the rotation speed can be 480-520 rpm, for example, 480 rpm, 490 rpm, 500 rpm, 510 rpm, 520 rpm or any two thereof, for grinding for 18-22 min, for example, 18 min, 19 min, 20 min, 21 min. in, 22min or a range consisting of any two thereof, and finally grinding at a rotation speed of 780-820rpm, such as 780rpm, 790rpm, 800rpm, 810rpm, 820rpm or a range consisting of any two thereof, for 38-42min, such as 38min, 39min, 40min, 41min, 42min or a range consisting of any two thereof. Grinding at a lower rotation speed first helps to disperse the material, and then grinding at a higher rotation speed further refines the material to obtain a viscous first solid electrolyte slurry, which helps to improve the mechanical properties of the sandwich structure polymer-based solid electrolyte, improve interface problems and cycle performance.

[0052] In specific implementation, the weighed first polymer, inorganic filler (called the third inorganic filler), and first lithium salt can be added to the ball mill, and then a certain volume of the first solvent can be taken using a pipette and added to the ball mill for the above-mentioned first grinding to obtain the first solid electrolyte slurry.

[0053] The energy density of most solid-state electrolytes is lower than expected, mainly due to the excessive thickness and weight of the solid-state electrolytes. Existing polymer electrolyte preparation methods mainly use casting and coating methods. However, these two methods make it difficult to accurately control the thickness of the polymer electrolyte (membrane). Some polymer electrolytes are too thin, resulting in poor mechanical properties, causing lithium dendrites to pierce and affecting the cycle life of the battery. Thicker polymer electrolytes (membranes) increase the shuttle path of lithium ions and significantly reduce ionic conductivity, resulting in the inability to cycle the battery at room temperature, and also increasing the weight and cost of the battery.

[0054] In some embodiments, the first solid electrolyte slurry is coated on the substrate, and after the first drying, the process of obtaining the first solid electrolyte layer includes: removing bubbles in the first solid electrolyte slurry, coating 8 to 12 mL of the first solid electrolyte slurry after the bubbles are removed on a surface with a plane area of ​​380 to 420 cm 2 After the first drying at 58-62°C, a first solid electrolyte layer is obtained. For example, the volume of the first solid electrolyte slurry after the bubbles are removed can be 8 mL, 9 mL, 10 mL, 11 mL, 12 mL, or any two thereof, and the plane area of ​​the substrate can be 380 cm 2 、390cm 2 , 400cm 2 、410cm 2 , 420cm 2 The first drying temperature can be 58° C., 60° C., 62° C., or any two thereof. Adjusting the coating amount helps flexibly adjust the thickness of the first solid electrolyte layer, thereby adjusting the sandwich structure polymer-based solid electrolyte.

[0055] In specific implementation, a vacuum filter can be used to filter the first solid electrolyte slurry at least twice, and the filtration time for each time can be 20±5 minutes to remove bubbles in the first solid electrolyte slurry. Then, a certain volume of the first solid electrolyte slurry after the bubbles are removed can be measured using a measuring cylinder (or sucked with a rubber-tipped dropper), and poured onto the substrate. After the first solid electrolyte slurry automatically extends to the entire substrate, it is placed in a vacuum oven for first drying to obtain a first solid electrolyte layer.

[0056] In some embodiments, the second solvent includes N-methylpyrrolidone and / or dimethylformamide, dimethylacetamide (DMAc).

[0057] In some embodiments, during the second grinding process, the rotation speed is first 80-120 rpm, such as 80 rpm, 90 rpm, 100 rpm, 110 rpm, 120 rpm or any two thereof, for grinding for 8-12 min, such as 8 min, 9 min, 10 min, 11 min, 12 min or any two thereof, and then the rotation speed is 480-520 rpm, such as 480 rpm, 490 rpm, 500 rpm, 510 rpm, 520 rpm or any two thereof, for grinding for 18-22 min, such as 18 min, 19 min, 20 min, 21 min. in, 22min or a range consisting of any two thereof, and finally grinding at a rotation speed of 780-820rpm, such as 780rpm, 790rpm, 800rpm, 810rpm, 820rpm or a range consisting of any two thereof, for 38-42min, such as 38min, 39min, 40min, 41min, 42min or a range consisting of any two thereof. Grinding at a lower rotation speed first helps to disperse the material, and then grinding at a higher rotation speed further refines the material to obtain a viscous second solid electrolyte slurry, which helps to improve the mechanical properties of the sandwich structure polymer-based solid electrolyte, improve interface problems and cycle performance.

[0058] In specific implementation, the weighed second polymer, inorganic filler (fourth inorganic filler), and second lithium salt can be added to the ball mill first, and then a certain volume of the second solvent can be taken by a pipette and added to the ball mill for the above-mentioned second grinding to obtain the second solid electrolyte slurry.

[0059] In some embodiments, the second solid electrolyte slurry is coated on the substrate, and after the first drying, the process of obtaining the first solid electrolyte layer includes: removing bubbles in the second solid electrolyte slurry, coating 8 to 12 mL of the second solid electrolyte slurry after the bubbles are removed on a surface with a plane area of ​​380 to 420 cm 2 After a second drying at 58-62°C on a substrate, a second solid electrolyte layer is obtained. For example, the volume of the second solid electrolyte slurry after degassing can be 8 mL, 9 mL, 10 mL, 11 mL, 12 mL, or a range consisting of any two thereof, and the plane area of ​​the substrate can be 380 cm 2 、390cm 2 , 400cm 2 、410cm 2 , 420cm 2 The second drying temperature can be 58° C., 60° C., 62° C., or a range consisting of any two thereof. By adjusting the coating amount, it is helpful to flexibly adjust the thickness of the second solid electrolyte layer, thereby adjusting the sandwich structure polymer-based solid electrolyte.

[0060] In specific implementation, the second solid electrolyte slurry can be filtered at least twice using a vacuum filter, and the filtration time for each time can be 20±5 minutes to remove bubbles in the second solid electrolyte slurry. Then, a certain volume of the second solid electrolyte slurry after the bubbles are removed can be measured using a measuring cylinder and poured onto the substrate. After the second solid electrolyte slurry automatically extends to the entire substrate, it is placed in a vacuum oven for a second drying to obtain a second solid electrolyte layer.

[0061] In some embodiments, the third solvent includes N-methylpyrrolidone and / or dimethylformamide, dimethylacetamide (DMAc).

[0062] In the process of mixing the third polymer, the first inorganic filler, the second inorganic filler, the third lithium salt and the third solvent to obtain the third solid electrolyte slurry, the mixed material can be stirred to mix uniformly. For example, the mixed material can be placed in a glass bottle and stirred using a constant temperature magnetic stirrer to obtain a viscous third solid electrolyte slurry, wherein the stirring temperature can be 48 to 52°C, for example, 48°C, 50°C, 52°C or a range consisting of any two thereof.

[0063] In some embodiments, the third solid electrolyte slurry is coated on a substrate, and after the third drying, a process of obtaining a third solid electrolyte layer comprises: removing bubbles from the third solid electrolyte slurry, coating 8 to 12 mL of the third solid electrolyte slurry after removing bubbles on a substrate with a plane area of ​​380 to 420 cm 2 After a second drying at 58-62°C on a substrate, a third solid electrolyte layer is obtained. For example, the volume of the third solid electrolyte slurry after removing bubbles can be 8 mL, 9 mL, 10 mL, 11 mL, 12 mL, or a range consisting of any two thereof, and the plane area of ​​the substrate can be 380 cm 2 、390cm 2 , 400cm 2 、410cm 2 , 420cm 2 The third drying temperature can be 58°C, 60°C, 62°C, or any two thereof. Adjusting the coating amount helps flexibly adjust the thickness of the third solid electrolyte layer, thereby adjusting the sandwich structure polymer-based solid electrolyte.

[0064] In specific implementation, the third solid electrolyte slurry can be filtered at least twice using a vacuum filter, and the filtration time for each filtration can be 20±5 minutes to remove bubbles in the third solid electrolyte slurry. Then, a certain volume of the third solid electrolyte slurry after the bubbles are removed can be measured using a measuring cylinder and poured onto the substrate. After the third solid electrolyte slurry automatically extends to the entire substrate, it is placed in a vacuum oven for a third drying to obtain a third solid electrolyte layer.

[0065] In some embodiments, the substrate comprises a glass plate, such as an ultra-flat glass plate with a length and width of 20±1 cm.

[0066] For example, the pressure during the pressing process may be 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, or a range consisting of any two thereof, and the temperature during the pressing process may be 160° C., 170° C., 180° C., 190° C., 200° C., or a range consisting of any two thereof. This facilitates flexible control of the thickness of the sandwich-structured polymer-based solid electrolyte.

[0067] In specific implementation, the first solid electrolyte layer, the third solid electrolyte layer, and the second solid electrolyte layer can be stacked in sequence in a special mold and pressed at 80-120 MPa and 160-200°C for 40-50 minutes, for example, 40 minutes, 45 minutes, 50 minutes or a range consisting of any two of them. After cooling, a sandwich structure polymer-based solid electrolyte is obtained.

[0068] The above-mentioned special mold can be made of manganese steel, which has the characteristic of small deformation. The special mold can be divided into three parts: a square base, a square frame, and a square cover. The square cover has a groove, and the height of the groove can be 15 to 50 μm.

[0069] An embodiment of the present invention further provides a solid-state battery, comprising the above-mentioned sandwich-structured polymer-based solid-state electrolyte or the sandwich-structured polymer-based solid-state electrolyte obtained according to the above-mentioned preparation method.

[0070] In specific implementation, the above-mentioned solid-state battery can be a semi-solid-state battery, a quasi-solid-state battery, or an all-solid-state battery, such as a semi-solid-state lithium-ion battery, a semi-solid-state sodium-ion battery, a quasi-solid-state lithium-ion battery, a quasi-solid-state sodium-ion battery, an all-solid-state lithium-ion battery, or an all-solid-state sodium-ion battery.

[0071] It is conceivable that the solid-state battery of the embodiment of the present invention includes a negative electrode sheet and a positive electrode sheet in addition to the above-mentioned sandwich structure polymer-based solid electrolyte.

[0072] The embodiments of the present invention are not strictly limited to the negative electrode active material in the negative electrode sheet, and can be at least one of the negative electrode active materials commonly used in lithium-ion batteries, such as graphite, hard carbon, soft carbon, silver-carbon mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon oxide, silicon-carbon negative electrode), tin-based negative electrode materials (mainly including tin, tin alloy), etc.

[0073] The embodiments of the present invention are not strictly limited to the negative electrode active material in the positive electrode sheet. The negative electrode active material can be any common positive electrode active material currently used in lithium-ion batteries, such as at least one composite oxide of lithium and a metal selected from the group consisting of cobalt, manganese, nickel, and combinations thereof. Specifically, the negative electrode active material can be at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate (LFP), lithium nickel manganese oxide, and lithium-rich manganese-based materials.

[0074] When preparing solid-state batteries, the positive electrode sheet, sandwich-structured polymer-based solid electrolyte and negative electrode sheet are stacked, pressed and packed in an aluminum soft package. Gel electrolyte can be optionally added for in-situ curing to complete the preparation of the solid-state battery.

[0075] The present invention is described in more detail below through specific embodiments.

[0076] Some of the raw materials in the examples are from the following sources:

[0077] Polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer (P(VDF-TrFE-CTFE)), polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)): purchased from Aucma.

[0078] Example 1

[0079] This embodiment provides a method for preparing a sandwich structure polymer-based solid electrolyte, comprising:

[0080] 2.5 g of P(VDF-TrFE-CTFE), 2.5 g of LATP, and 0.25 g of LiTFSI were added to a ball mill, 50 mL of DMF was measured with a pipette, added to the ball mill, and mixed, and then ball-milled at rotation speeds of 100 rpm, 500 rpm, and 800 rpm for 10 min, 20 min, and 40 min, respectively, to obtain a first solid electrolyte slurry; the first solid electrolyte slurry was filtered twice using a vacuum filter, each filtration time being 20 min to remove bubbles in the first solid electrolyte slurry; 10 mL of the first solid electrolyte slurry after bubble removal was measured with a measuring cylinder and coated on an ultra-flat glass plate with a length and width of 20 cm. After the solution automatically extended to the entire ultra-flat glass plate, it was placed in a vacuum oven and dried at 60° C. to obtain a first solid electrolyte layer;

[0081] 2.5 g of P(VDF-TrFE-CTFE), 2.5 g of Al2O3, and 0.25 g of LiTFSI were added to a ball mill, 50 mL of DMF was measured with a pipette and added to the ball mill, and then ball milled at rotation speeds of 100 rpm, 500 rpm, and 800 rpm for 10 min, 20 min, and 40 min, respectively, to obtain a second solid electrolyte slurry; the second solid electrolyte slurry was filtered twice using a vacuum filter, each filtration time being 20 min to remove bubbles in the second solid electrolyte slurry; 10 mL of the second solid electrolyte slurry after bubble removal was measured with a measuring cylinder and coated on an ultra-flat glass plate with a length and width of 20 cm. After the solution automatically extended to the entire ultra-flat glass plate, it was placed in a vacuum oven and dried at 60° C. to obtain a second solid electrolyte layer;

[0082] 2.5 g of P(VDF-TrFE-CTFE), 2.5 g of Al2O3 with a particle size of 300 nm, 2.5 g of Al2O3 with a particle size of 5000 nm, and 0.25 g of LiTFSI were added to a glass bottle, 50 mL of DMF was measured with a pipette and added to the glass bottle after mixing, and then magnetically stirred at a constant temperature of 50 ° C to obtain a third solid electrolyte slurry; the third solid electrolyte slurry was filtered twice using a vacuum filter, each filtration time was 20 min to remove bubbles in the second solid electrolyte slurry; 10 mL of the second solid electrolyte slurry after removing bubbles was measured with a measuring cylinder and coated on an ultra-flat glass plate with a length and width of 20 cm. After the solution automatically extended to the entire ultra-flat glass sheet, it was placed in a vacuum oven and dried at 60 ° C to obtain a third solid electrolyte layer;

[0083] The first solid electrolyte layer, the third solid electrolyte layer, and the second solid electrolyte layer were stacked in sequence and pressed at 100 MPa and 180°C for 45 minutes to obtain a sandwich structure polymer-based solid electrolyte (P(VDF-TrFE-CTFE) / LATP / LiTFSI composite solid electrolyte membrane).

[0084] The sandwich structure polymer-based solid electrolytes of Examples 2 to 3 and Comparative Examples 1 to 3 were prepared by referring to the process of Example 1. Comparative Example 4 is a commercial separator purchased from Shenzhen Xingyuan Materials Technology Co., Ltd.

[0085] Parameters such as the types of components in each solid electrolyte layer of each embodiment and comparative example and the mass percentage (content) of each component in each layer are summarized in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] Test Example 1

[0090] 1. The following parameters were tested for the above examples and comparative examples:

[0091] 1) Thickness of the sandwich-structured polymer-based solid electrolyte and the first, second, and third solid electrolyte layers: A film thickness meter was used to test the thickness of the sandwich-structured polymer-based solid electrolyte or the separated first, second, and third solid electrolyte layers. The specific results are shown in Tables 2 and 3.

[0092] 2) Needle Puncture Strength of Sandwich Structure Polymer-Based Solid-State Electrolyte and First, Second, and Third Solid-State Electrolyte Layers: First, a specimen with a diameter of 100 mm (including the sandwich structure polymer-based solid-state electrolyte, the separated first, second, or third solid-state electrolyte layers) was prepared. The specimen was uniform in thickness and free of wrinkles, folds, stains, or other obvious defects. The 90° peel strength test was then performed at a rate of (50 ± 5) mm / min. -1 The puncture strength value was obtained by pricking at a speed of 100 nm. Each group of samples included 5 test pieces, and the arithmetic average of these 5 test pieces was used to obtain the final test result of the puncture strength. The specific results are shown in Tables 2 and 3.

[0093] 3) Thermal shrinkage of sandwich structure polymer-based solid electrolyte (solid electrolyte): Cut a 10cm×10cm square solid electrolyte sample, lay it flat and sandwich it between two transparent and clean glass plates, then place the glass plates in a blast drying oven that has reached the set temperature and bake for 1 hour. After baking, cool the glass plates to room temperature, and observe and measure the morphological changes of the square solid electrolyte samples; wherein, the test temperature point (the set temperature of the above-mentioned blast drying oven) is 120°C, and the baking time is 1 hour; the calculation formula of the thermal shrinkage rate S is: S / %=(S0-S1) / S0×100%, in which S is the thermal shrinkage rate; S0 is the area of ​​the square solid electrolyte sample cut before heat treatment (baking), and S1 is the area of ​​the square solid electrolyte sample after heat treatment (baking), and the unit is mm 2 ; Specific results are shown in Table 3;

[0094] 4) Ionic conductivity of the sandwich structure polymer-based solid electrolyte and the first solid electrolyte layer, second solid electrolyte layer, and third solid electrolyte layer products: The ionic conductivity is measured by electrochemical impedance spectroscopy (EIS) and then calculated using the formula. The specific test method is as follows: assemble SS (circular stainless steel sheet) / polymer electrolyte / SS blocking battery in a glove box. The test temperature is 25°C. The temperature must be kept constant for more than 2 hours before the test. The test frequency is 1MHz-0.1Hz and the amplitude voltage is 3mV. Use Autolab Rui The test was carried out using a Shiwanhua electrochemical workstation. The measured graph was a semicircle and a straight line with a slope of about 45°. The real impedance value of the intersection of the semicircle and the straight line is the bulk resistance Rb of the electrolyte membrane. The ionic conductivity can be calculated using the following formula: σ = L / (Rb*S), where: σ is the ionic conductivity of the test sample (such as a sandwich-structured polymer-based solid electrolyte membrane), in S / cm; L is the thickness of the test sample, in cm; Rb is the bulk resistance of the test sample, in Ω; and S is the area of ​​the test sample, in cm. 2 ; Specific results are shown in Table 2 and Table 3;

[0095] 5) Porosity of the sandwich-structured polymer-based solid electrolyte and the first, second, and third solid electrolyte layers: Porosity was measured using a surface area analyzer (Quantavi, USA, Nova 1200e) using nitrogen. The results are shown in Tables 2 and 3.

[0096] 2. Test results

[0097] Table 2 Thickness, puncture strength, ionic conductivity, and porosity of the first solid electrolyte layer, the second solid electrolyte layer, and the third solid electrolyte layer

[0098]

[0099]

[0100] Table 3 Thickness, ionic conductivity, density, and thermal shrinkage of sandwich structure polymer-based solid electrolytes

[0101]

[0102] Data Analysis:

[0103] From the analysis of Table 2 and Table 3, it can be seen that the sandwich structure polymer-based solid electrolyte of the embodiment of the present invention has a higher needle puncture strength and a lower thermal shrinkage rate.

[0104] Test Example 2

[0105] The sandwich-structured polymer-based solid electrolytes and the positive and negative electrode sheets in all the embodiments and comparative examples were stacked, pressed and packed in an aluminum soft pack, and gel additives were added for in-situ curing to form a solid-state battery. The gel additives were purchased from Sinopharm Group. The specific process included the assembly of the battery core, including stacking, packaging, liquid injection and formation steps, and finally formed a complete soft-pack battery.

[0106] Among them, the preparation process of the positive electrode sheet and the negative electrode sheet is as follows:

[0107] Positive electrode sheet preparation: The lithium iron phosphate positive electrode material is uniformly mixed with the conductive agent carbon black and the binder polyvinylidene fluoride to form a slurry with good electrical conductivity and adhesion. The prepared slurry is coated on the aluminum foil current collector, usually using a coater. The coated aluminum foil is dried to remove the solvent and solidify the solid components in the slurry to obtain a dried positive electrode sheet. The dried positive electrode sheet is compacted through a roller pressing process to increase the volume energy density of the battery to obtain the positive electrode sheet.

[0108] Preparation of negative electrode sheet: The graphite negative electrode material is mixed evenly with the conductive agent carbon black and the binder polyvinylidene fluoride to form a negative electrode slurry; the negative electrode slurry is coated on the copper foil current collector, and after drying and rolling, the negative electrode sheet is obtained.

[0109] The cycle performance of the above solid-state battery was tested:

[0110] The capacity retention rate of each solid-state battery obtained was tested. The specific test method was as follows: place it at 45°C for 5 hours, charge it to 3.65V at a constant power of 1P, let it stand for 15 minutes, then discharge it to 2.50V at a constant power of 1P, let it stand for 15 minutes, repeat this charge and discharge cycle 500 times, and measure the discharge energy Q1 at the first cycle and the discharge energy Q at the 500th cycle. 500 , calculate the discharge energy retention rate Q after 500 cycles according to the following formula: capacity retention rate Q = Q 500 / Q1*100%.

[0111] Cycle life: The battery cycle life is evaluated using the capacity decay rate method. The battery is charged and discharged under normal conditions. The number of charge and discharge cycles when its capacity drops to 80% or less of the rated capacity is the cycle life. In addition, the battery's capacity loss rate in each charge and discharge cycle is calculated and a capacity decay curve is drawn to evaluate the battery's decay rate and remaining life.

[0112] Table 4 Battery cycle performance

[0113]

[0114] Combine Figures 1-6As shown in Table 4, the sandwich structure polymer-based solid electrolyte provided by the embodiment of the present invention has good cycle stability.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sandwich structure polymer-based solid electrolyte, characterized in that: comprising a first solid electrolyte layer, a second solid electrolyte layer, and a third solid electrolyte layer located between the first solid electrolyte layer and the second solid electrolyte layer; The content of the inorganic filler in the third solid electrolyte layer is higher than the content of the inorganic filler in the first solid electrolyte layer; The content of the inorganic filler in the third solid electrolyte layer is higher than the content of the inorganic filler in the second solid electrolyte layer; The inorganic filler in the third solid electrolyte layer includes a first inorganic filler and a second inorganic filler, and the particle size of the first inorganic filler is smaller than the particle size of the second inorganic filler.

2. The sandwich structure polymer-based solid electrolyte according to claim 1, characterized in that: The ratio of the particle size of the first inorganic filler to the particle size of the second inorganic filler is 1:(1-1000), and the ratio of the particle size of the first inorganic filler to the particle size of the second inorganic filler is not 1.

3. The sandwich structure polymer-based solid electrolyte according to claim 2, characterized in that: The particle size of the first inorganic filler is 10 to 500 nm, and the particle size of the second inorganic filler is 1 to 10 μm.

4. The sandwich structure polymer-based solid electrolyte according to claim 3, characterized in that: The mass ratio of the first inorganic filler to the second inorganic filler is (1-2):(2-10).

5. The sandwich structure polymer-based solid electrolyte according to claim 1, characterized in that: The first solid electrolyte layer comprises, by weight percentage, 40% to 100% of a first polymer, 0% to 60% of the inorganic filler, and 1% to 10% of a first lithium salt; The second solid electrolyte layer comprises, by weight percentage, 40% to 100% of the third polymer, 0% to 60% of the inorganic filler, and 1% to 10% of the third lithium salt; The third solid electrolyte layer comprises, by weight percentage, 25-100% of the second polymer, 0-75% of the inorganic filler, and 1-10% of the second lithium salt.

6. The sandwich structure polymer-based solid electrolyte according to claim 1, characterized in that: The inorganic filler includes one or more of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium lanthanum zirconium titanium oxide, aluminum oxide, silicon oxide, hafnium oxide, and barium titanate; And / or, the first inorganic filler and the second inorganic filler each independently include one or more of aluminum oxide, silicon oxide, hafnium oxide, and barium titanate.

7. A method for preparing a sandwich structure polymer-based solid electrolyte according to any one of claims 1 to 6, characterized in that: include: Mixing a first polymer, an inorganic filler, a first lithium salt, and a first solvent, and performing a first grinding process to obtain a first solid electrolyte slurry; Applying the first solid electrolyte slurry on a substrate and performing a first drying process to obtain a first solid electrolyte layer; Mixing a second polymer, an inorganic filler, a second lithium salt, and a second solvent, and performing a second grinding to obtain a second solid electrolyte slurry; coating the second solid electrolyte slurry on a substrate, and performing a second drying to obtain a second solid electrolyte layer; mixing a third polymer, the first inorganic filler, the second inorganic filler, a third lithium salt, and a third solvent to obtain a third solid electrolyte slurry; coating the third solid electrolyte slurry on a substrate, and performing a third drying to obtain the third solid electrolyte layer; wherein the sum of the addition amount of the first inorganic filler and the second inorganic filler is greater than the addition amount of the inorganic filler in the first solid electrolyte layer, and the sum of the addition amount of the first inorganic filler and the second inorganic filler is greater than the addition amount of the inorganic filler in the second solid electrolyte layer; The first solid electrolyte layer, the third solid electrolyte layer, and the second solid electrolyte layer are stacked in sequence and pressed at 80-120 MPa and 160-200° C. to obtain the sandwich structure polymer-based solid electrolyte.

8. The preparation method according to claim 7, characterized in that During the first grinding process, the grinding speed is first 80-120 rpm for 8-12 minutes, then the grinding speed is 480-520 rpm for 18-22 minutes, and finally the grinding speed is 780-820 rpm for 38-42 minutes; And / or, the first solid electrolyte slurry is coated on the substrate, and after the first drying, the process of obtaining the first solid electrolyte layer includes: removing bubbles in the first solid electrolyte slurry, coating 8 to 12 mL of the first solid electrolyte slurry after removing bubbles on a surface with a plane area of ​​380 to 420 cm 2 on the substrate, performing a first drying at 58-62° C. to obtain the first solid electrolyte layer; And / or, during the second grinding process, the grinding is first performed at a rotation speed of 80-120 rpm for 8-12 min, then at a rotation speed of 480-520 rpm for 18-22 min, and finally at a rotation speed of 780-820 rpm for 38-42 min; And / or, the second solid electrolyte slurry is coated on the substrate, and after the second drying, the process of obtaining the second solid electrolyte layer includes: removing bubbles in the second solid electrolyte slurry, coating 8 to 12 mL of the second solid electrolyte slurry after removing bubbles on a plane area of ​​380 to 420 cm 2 on the substrate, performing a second drying at 58-62° C. to obtain the second solid electrolyte layer; And / or, the third solid electrolyte slurry is coated on the substrate, and after the third drying, the process of obtaining the third solid electrolyte layer comprises: removing bubbles in the third solid electrolyte slurry, coating 8 to 12 mL of the third solid electrolyte slurry after removing bubbles on a plane area of ​​380 to 420 cm 2 The substrate is coated with a film and dried for the second time at 58-62° C. to obtain the third solid electrolyte layer.

9. The preparation method according to claim 7, characterized in that The first polymer, the second polymer, and the third polymer each independently include one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer, and polyvinylidene fluoride-trifluoroethylene copolymer; And / or, the first lithium salt, the second lithium salt, and the third lithium salt each independently include one or more of lithium bis(trifluoromethanesulfonyl)imide and lithium hexafluorophosphate.

10. A solid-state battery, characterized in that: The invention comprises the sandwich structure polymer-based solid electrolyte according to any one of claims 1 to 6 or the sandwich structure polymer-based solid electrolyte obtained according to the preparation method according to any one of claims 7 to 9.

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