A ceramic-based composite solid electrolyte membrane and its preparation and application

Abstract

The present invention belongs to the field of solid-state battery materials, and specifically relates to a method for preparing a ceramic-based composite solid electrolyte membrane, comprising pressing a raw material comprising a ceramic solid electrolyte material and a pore-forming agent to obtain a green block, which is then subjected to a multi-stage heat treatment to obtain a porous ceramic block; the multi-stage heat treatment process includes a first heat treatment process at 30-1500°C and a second heat treatment process at 700-1500°C; the raw material contains 15-50wt.% of the pore-forming agent; the porous ceramic block is immersed in a polymer solution and dried to obtain a composite ceramic block; the composite ceramic block is cut to obtain the ceramic-based composite solid electrolyte membrane. The present invention also includes materials obtained by the preparation method and their application in solid-state batteries. The method of the present invention can produce high-performance ultra-thin solid electrolytes.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage materials, and in particular relates to the field of solid-state battery electrolyte materials. Background Art

[0002] At present, the extensive use of non-clean energy such as fossil fuels has caused serious pollution problems. The development and effective utilization of green renewable energy and environmental protection have become issues of common concern to the world.

[0003] Lithium-ion secondary batteries are widely used in consumer electronic products due to their many advantages, such as high energy density, long cycle life, low self-discharge, no memory effect, wide operating temperature range and low cost. Traditional liquid batteries face serious safety issues due to electrolyte leakage, combustion and even explosion. In recent years, solid-state batteries based on solid electrolytes have gradually become a research hotspot. The non-flammability and high stability of solid electrolytes have greatly improved the safety issues of batteries. However, a single solid electrolyte cannot meet the various requirements of lithium battery applications, which seriously hinders the development of high-energy-density lithium batteries. Therefore, it is urgent to design a solid-state lithium battery based on a composite solid electrolyte. Through a simple and feasible process, a composite electrolyte that meets multiple performance requirements such as high conductivity, wide electrochemical window, resistance to lithium dendrites, and high mechanical strength can be prepared and applied to solid-state batteries, thereby improving the energy density, cyclability and practical operability of solid-state batteries. Currently, composite electrolyte membrane preparation processes include solution spraying, tape casting, and solution casting. While solution spraying can form a continuous skeleton, its membrane formation typically involves coating, sintering, and finally filling with polymer fillers. This method, when used to prepare ultra-thin electrolyte membranes, is prone to curling during the sintering process, resulting in low processing efficiency, low yield, and poor workability. Summary of the Invention

[0004] In response to the problems of unsatisfactory processing performance and electrochemical performance of existing solid-state battery electrolytes, the first purpose of the present invention is to provide a method for preparing an ultra-thin ceramic-based composite solid electrolyte membrane (also referred to as solid electrolyte in the present invention), aiming to obtain a material with excellent flexibility, processing performance and electrochemical properties.

[0005] The second object of the present invention is to provide a ceramic-based composite solid electrolyte membrane prepared by the preparation method.

[0006] The third object of the present invention is to provide an application of the ceramic-based composite solid electrolyte membrane in a battery.

[0007] The fourth object of the present invention is to provide a solid-state battery equipped with the ceramic-based composite solid electrolyte membrane.

[0008] For ceramic solid electrolytes, the main method in the industry is to pre-form a thin film and then bake it. The ceramic membrane solid electrolyte membrane obtained by this process has an unsatisfactory morphology and unsatisfactory electrochemical performance. In response to this problem, the inventors previously tried to use ceramic block cutting to prepare ultra-thin solid electrolyte membranes. However, studies have found that for batteries to have solid electrolytes, they require a certain pore structure. However, the presence of the pore structure will significantly increase the difficulty of thin slice cutting. Not only that, for the battery field, ultra-thin materials can theoretically obtain better electrochemical performance. However, the difficulty of ultra-thin cutting, especially ultra-thin slices with a moderate pore structure, will be further increased. For example, blocks with pore structures are very prone to powdering, structural collapse, large brittle slices, and unsatisfactory electrochemical performance in the process of being cut into ultra-thin slices suitable for batteries. In response to the technical difficulties faced in preparing ultra-thin solid electrolytes by block slicing, the present invention provides the following improvement scheme:

[0009] A method for preparing a ceramic-based composite solid electrolyte membrane comprises pressing raw materials comprising a ceramic solid electrolyte material and a pore-forming agent into a green block, followed by multi-stage heat treatment to obtain a porous ceramic block. The multi-stage heat treatment process comprises a first heat treatment process at 30-1500°C and a second heat treatment process at 700-1500°C. The raw materials contain 15-50% pore-forming agent by weight.

[0010] soaking the porous ceramic block in a polymer solution and drying it to obtain a composite ceramic block;

[0011] The composite ceramic block is cut to obtain the ceramic-based composite solid electrolyte membrane.

[0012] The present invention proposes for the first time the idea of ​​using 3D dense porous ceramic block slices to prepare solid electrolytes, and further finds that by using a pore-forming agent in conjunction with the multi-stage heat treatment process to jointly construct a porous ceramic block, and then impregnating the porous ceramic block with the polymer before slicing, it can effectively overcome the problem that the porous block is easily pulverized during the ultra-thin cutting stage and it is difficult to obtain ultra-thin slices suitable for solid electrolytes, which is conducive to the preparation of a solid electrolyte membrane with excellent processing performance, an excellent dense skeleton and 3D through-pores, and excellent electrochemical performance. The present invention has found that the preparation method is simple, and the solid electrolyte obtained has multiple properties such as high conductivity, a wide electrochemical window, resistance to lithium dendrites, and flexibility, which can effectively improve the energy density, cyclability and practical operability of solid-state batteries.

[0013] In the present invention, the combination of the preparation of the porous ceramic block with the assistance of a pore former and the cutting process after polymer impregnation is the key to synergistically achieving the preparation of ultrathin slices and improving the processing performance and electrochemical properties of the obtained solid ceramic electrolyte.

[0014] In the present invention, the ceramic solid electrolyte material can be a material known to those skilled in the art of solid electrolytes, such as a lithium-containing ceramic solid electrolyte material; preferably, at least one of a lithium oxide solid electrolyte and a lithium sulfide solid electrolyte;

[0015] Preferably, the lithium oxide solid electrolyte is Li x La y TiO3, Li a Al b M1 2-b P3O g Or Li c La d M2 e Zr f O g One or more of, wherein 0.1<x<1, 0<y<1, 0.1<a<2, 0<b<2, 5<c<8, 1.5<d<4, 0.1<e<2, 0<f<2, 10<g<13, M1 is selected from one or more of Ge and Ti, and M2 is selected from one or more of Nb, Ta, Ga, and Al;

[0016] Preferably, the lithium sulfide solid electrolyte is one or more of LiPSX (X = Cl, Br, I), LiSiPSX (X = Cl, Br, I), LiGPS, and LiPS;

[0017] The particle size of the ceramic solid electrolyte material is less than or equal to 2 μm, more preferably 0.05 to 1.5 μm. The particle size of the present invention may be a D50 particle size.

[0018] The present invention has found that the key to constructing a 3D porous ceramic block and balancing the density of the block skeleton with the 3D pore structure is to facilitate the subsequent slicing and preparation of solid-state ceramic electrolytes with high processing performance and electrochemical performance. To this end, the present invention has found that combining ceramic particles with a pore-forming agent, and under the combined control of the required sintering mechanism and the amount of pore-forming agent, can unexpectedly achieve synergy, capable of constructing a dense skeleton and a 3D porous structure, which is conducive to the preparation of solid-state ceramic electrolytes with high electrochemical performance.

[0019] In the present invention, the pore-forming agent is one or more of polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), polystyrene (PS), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyethylene oxide (PEO), PEO block copolymers, polyethylene glycol (PEG), cellulose, starch, urea, carbon powder, sodium chloride, sulfur powder, naphthalene, zinc powder, and ammonium bicarbonate; starch is preferred. The present invention unexpectedly discovered that using starch as a pore-forming agent can achieve a superior synergistic effect in the process system of the present invention, unexpectedly facilitating the cutting of thin sheets suitable for batteries and improving their electrochemical performance.

[0020] In the present invention, under the combined control of the selection and content of the pore-forming agent, it is beneficial to the subsequent cutting of thin sheets suitable for batteries and to the performance of the obtained cut electrolyte.

[0021] Preferably, the weight content of the pore-forming agent in the raw materials is 15-45 wt.%, more preferably 15-40 wt.%, and most preferably 30-35 wt.%.

[0022] In the present invention, a binder may be added to the raw materials. Studies have shown that the use of an appropriate amount of binder is more conducive to synergistically improving the cutting of thin sheets suitable for batteries and enhancing electrochemical performance.

[0023] In the present invention, the binder is one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polypropylene (PP), atactic polypropylene (aPP), isotactic polypropylene (iPP), ethylene propylene rubber (EPR), ethylene pentene copolymer (EPC), polyisobutylene (RP3), styrene butadiene rubber (SBR), poly(ethylene-co-) l-octene) (PE-co-PO), poly(ethylene-co-methylenecyclopentene) (PE-co-PMCP), stereo block polypropylene, polypropylene polymethylpentene, polyethylene oxide (PEO), PEO block copolymer, silicone polymer and copolymer, polyvinyl butyral (PVB), poly(vinyl acetate) (PVAc), polyvinyl pyrrolidine (PVP), polyethylene glycol (PEG), poly(ethyl methacrylate) (PEMA), polyvinyl alcohol (PVA), acrylic polymer, a binder from a Paraloid series of resins, a binder from a Butvar series of resins, and a binder from a Mowital series of resins.

[0024] In the raw materials, the weight content of the binder is less than or equal to 20 wt.%, preferably 5-10 wt.%, and more preferably 5-6 wt.%.

[0025] In the present invention, the components can be mixed by existing means, for example, by dry ball milling, wet ball milling, air flow pulverization or stirring.

[0026] In the present invention, the raw materials are placed in the required mold and pressed to form a green body. In the present invention, the green body can be pressed into the required shape according to the requirements of battery assembly. For example, the green body can be pressed into a square block, a cylindrical block, etc. There are no special requirements for the size of the green body. For example, the green body block can be a rectangular parallelepiped with a length of 1-2500mm and a width of 1-2500mm; it can be an irregular body with a length of 1-2500mm, a width of 1-2500mm, and a height of 1-12500mm; or a cylinder with a diameter of 1-1250mm; the height of the block is 0.1-5000mm.

[0027] In the present invention, the pressing pressure is 10-500 MPa, preferably 100-350 MPa;

[0028] The present invention has found that, under the control of the pore-forming agent, the selectively added binder and the dosage, further combined with a multi-stage heat treatment mechanism, unexpected synergy can be achieved, which is beneficial for subsequent cutting to obtain an ultra-thin solid electrolyte with excellent electrochemical properties.

[0029] The sintering can be conventional sintering, hot pressing sintering or hot isostatic pressing sintering;

[0030] Preferably, the multi-stage heat treatment process is carried out in an atmosphere such as air or oxygen; or a non-reactive environment such as nitrogen or an inert gas such as argon.

[0031] Preferably, the heating rate during the first heat treatment is less than or equal to 20°C / min; more preferably, 1-10°C / min; and even more preferably, 1-5°C / min. Preferably, the temperature during the first heat treatment is 80-1100°C; even more preferably, 450-600°C; and most preferably, 550-600°C. Research has found that under this preferred process, subsequent cutting can further facilitate the production of a ceramic electrolyte suitable for battery applications while also achieving excellent electrochemical performance.

[0032] Preferably, the first heat treatment process lasts for 1-10 hours, more preferably 2-8 hours.

[0033] Preferably, the heating rate during the second heat treatment is 5-100°C / min; more preferably, 10-50°C / min, and even more preferably, 15-25°C / min. Preferably, the temperature of the second heat treatment is 1100-1200°C, and even more preferably, 1150-1200°C. Studies have found that under this preferred process, subsequent cutting can further facilitate the production of ceramic electrolytes suitable for batteries while also achieving excellent electrochemical performance.

[0034] Preferably, the second heat treatment process lasts for 1-20 hours, more preferably 4-10 hours.

[0035] Preferably, the porosity of the porous ceramic block is 10-90%, preferably 40-70%, and the density is 4.0-5.5 g / cm3;

[0036] The present invention has found that under the porous ceramic block preparation process, a dense ceramic skeleton and an electrochemically suitable 3D pore structure can be obtained. Further combined with the subsequent polymer solution impregnation and slicing process, an ultra-thin solid-state ceramic electrolyte with excellent electrochemical performance can be successfully achieved.

[0037] The polymer solution is an organic solution in which a polymer is dissolved;

[0038] Preferably, the polymer is one or more of polyethylene oxide (PEO), PEO block copolymer, PEO graft polymer, polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyethylene glycol (PEG), succinonitrile (SN), polyimide (PI), polystyrene (PS) and polypropylene (PP);

[0039] Preferably, the organic solvent in the polymer solution is an aprotic solvent, preferably at least one of acetonitrile, DMF, DME, NMP, toluene, tetrahydrofuran, DOL, chloroform, isopropanol, and ethanol;

[0040] Preferably, a conductive lithium salt is further added to the polymer solution, and the conductive lithium salt is one or more of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium perchlorate (LiClO4);

[0041] Preferably, the concentration of the polymer in the polymer solution is 1 to 30 wt%; more preferably 5 to 15 wt%.

[0042] Preferably, the weight ratio of the polymer to the conductive lithium salt is 1 to 10:1;

[0043] Preferably, the soaking process is carried out under negative pressure or positive pressure;

[0044] Preferably, the negative pressure is less than or equal to -0.1 mPa; the positive pressure is greater than or equal to 0.1 mPa.

[0045] In the present invention, ultra-thin slices can be successfully obtained through the porous block and polymer composite process, and not only that, good electrochemical performance can also be taken into account.

[0046] In the present invention, the block can be cut based on existing cutting equipment and processes, for example, by one or more of diamond wire cutting, laser cutting, and ion polishing.

[0047] Preferably, the thickness of the cut ceramic sheet is 5 μm-200 μm, more preferably 50-150 microns; the present invention can cut to obtain the ultra-thin solid electrolyte, and the material obtained by this preparation process has both excellent mechanical properties such as flexibility and excellent electrochemical properties.

[0048] Preferably, the cut ceramic sheets are surface treated to produce the ceramic-based composite solid electrolyte membrane. Studies have found that surface treatment of the cut membrane material can unexpectedly achieve synergy and help further improve the electrochemical performance of the cut solid electrolyte.

[0049] Preferably, the surface treatment method is one or more of magnetron sputtering, ion polishing, metallographic polishing, electrochemical deposition, plasma cleaning, atomic layer deposition and chemical vapor deposition.

[0050] A preferred solution of the present invention comprises the following steps:

[0051] (a) providing a ceramic powder comprising at least one lithium ion ceramic solid electrolyte component;

[0052] (b) mixing the ceramic powder and the binder in a non-reactive environment to obtain a mixture A; the mixing time in step (b) is 1-12 hours, preferably 2-6 hours;

[0053] (c) mixing mixture A with a pore-forming agent in a non-reactive environment to obtain mixture B; the mixing time in step (c) is 1-6 hours, preferably 1-3 hours.

[0054] (d) filling the mixture B into a mold in a non-reactive environment to obtain a ceramic green body, which is a block;

[0055] (e) heating the green body to 30-1500° C. at a rate of less than or equal to 20° C. / min, maintaining the temperature for a first calcination process, and then heating the green body to 700-1500° C. at a rate of 5-100° C. / min, maintaining the temperature for a second calcination process to obtain a bulk porous ceramic;

[0056] (f) immersing the bulk porous ceramic in a solution containing at least one polymer in a non-reactive environment and drying the solution to obtain a ceramic-based solid electrolyte composite bulk;

[0057] (g) The ceramic-based solid electrolyte composite block is cut in a non-reactive environment and subjected to surface treatment to obtain an ultrathin ceramic-based composite electrolyte membrane.

[0058] The present invention also provides a ceramic-based composite solid electrolyte membrane prepared by the preparation method.

[0059] In the present invention, thanks to the special preparation method, the solid electrolyte can be given special substances and microstructures, and can be given excellent electrochemical properties.

[0060] The present invention also provides an application of the ceramic-based composite solid electrolyte membrane prepared by the preparation method, which is used to prepare a solid-phase electrolyte for a battery;

[0061] Preferably, it is used to prepare a solid electrolyte for a lithium secondary battery;

[0062] Preferably, the lithium secondary battery is a lithium ion battery or a lithium metal battery.

[0063] The present invention also provides a lithium secondary solid-state battery, comprising the ceramic-based composite solid electrolyte membrane prepared by the preparation method.

[0064] The basic components and construction method of the lithium secondary solid-state battery are the same as those of existing methods, and the main difference is that the ceramic-based composite solid electrolyte membrane prepared by the preparation method of the present invention is used as the solid electrolyte.

[0065] The battery of the present invention may have an operating voltage of 3-5V and may be a button cell or a soft pack cell.

[0066] Beneficial effects

[0067] The present invention proposes for the first time the idea of ​​preparing solid electrolytes by slicing 3D dense porous ceramic blocks, and further discovers that by using a pore-forming agent in combination with the multi-stage heat treatment process to jointly construct a porous ceramic block, and then impregnating the porous ceramic block with the polymer before slicing, the problem of easy pulverization of the porous block during the cutting stage and difficulty in obtaining ultra-thin slices suitable for solid electrolytes can be effectively overcome, which is conducive to the preparation of a solid electrolyte membrane with excellent processing performance, an excellent dense skeleton and 3D through-pores, and excellent electrochemical properties.

[0068] In the present invention, the combined control of the composition and content of the pore-forming agent, the mechanism of the two-stage heat treatment, and other processes can further synergistically benefit the preparation and electrochemical performance of battery-suitable thin sheets. Further surface post-treatment can help further improve the electrochemical performance of the resulting solid electrolyte.

[0069] In the present invention, thanks to the special preparation method, the solid electrolyte can be given special substances and microstructures, and can be given excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 is a SEM image of the porous ceramic of Example 1;

[0071] Figure 2 This is a picture of the porous ceramic of Example 1;

[0072] Figure 3 This is the EIS graph of the porous ceramic of Example 1 (porous skeleton only at 25°C)

[0073] Figure 4 This is the cycle diagram of Example 1 at 0.5C (25°C)

[0074] Figure 5 This is the lithium symmetric cycle diagram of Example 1 at a current density of 0.3 mA / cm2 (25°C)

[0075] Figure 6 This is a picture of the product prepared in Comparative Example 1;

[0076] Figure 7 This is a picture of the product obtained in Comparative Example 2;

[0077] Figure 8 This is a picture of the product obtained in Comparative Example 3;

[0078] Figure 9 This is a picture of the product obtained in Comparative Example 4;

[0079] Figure 10 Picture of the product obtained in Comparative Example 6 DETAILED DESCRIPTION

[0080] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention. In the examples of the present invention, unless otherwise specified, the means used are conventional means in the art and the reagents used can be obtained through conventional commercial channels.

[0081] Example 1

[0082] Lithium carbonate, tantalum oxide, lanthanum oxide, and zirconium oxide powders are prepared in a stoichiometric ratio of Li6.4La3Zr1.4Ta0.6O12, wherein lithium is in excess of 10 mol% relative to the stoichiometric ratio, to obtain a mixture A. Mixture A is ball-milled for 12 hours at a speed of 400 rpm using isopropyl alcohol as a solvent, and dried to obtain a mixture B. Mixture B is calcined at 800°C for 12 hours, ground and sieved to obtain a powder C with a particle size of d50=700 nm. Material C, a binder, and a pore-forming agent are mixed to obtain a mixture D. The binder is PVB, and the pore-forming agent is starch. In mixture D, the binder content is 5 wt%; the pore-forming agent content is 30 wt%.

[0083] The mixture D was poured into a mold (specifications: diameter 10 mm × 15 cm) and pressurized (300 MPa). In an air atmosphere, the temperature was first increased to 600°C at a rate of 1°C / min and kept at that temperature for 6 h (first stage heat treatment), and then increased to 1200°C at a rate of 20°C / min and kept at that temperature for 6 h (second stage heat treatment) to complete densification. A block-shaped dense porous embryo E was obtained with a porosity of 50% and a geometric density of 5.0 g / cm 3 ;

[0084] The green body E is immersed in a lithium polymer solution, wherein the lithium polymer solution is an acetonitrile solution containing polyethylene oxide (PEO) and LiTFSI, wherein the EO:Li ratio is 10:1 and the solid content of PEO is 10%. The green body E is then vacuum-infiltrated with the uniform solution and dried to obtain a block-shaped composite green body F.

[0085] The thin films were cut to obtain regular circular sheets (specifications: diameter 12 mm × 100 μm (thickness)). After surface treatment in a nitrogen atmosphere, the thin films were cleaned with a plasma cleaner for 30 seconds. The curvature of the prepared electrolyte sheets was 45°, and the ionic conductivity was 3×10^ -4 S / cm. The SEM structure of the obtained ceramic solid electrolyte sheet is shown in Figure 1 ; See photos Figure 2 .

[0086] The single-crystal ternary NCM622 cathode sheet was transferred to an argon glove box and assembled into a CR2016 button cell using a metal lithium sheet as the anode and a composite electrolyte sheet as the electrolyte. The constant current charge and discharge performance was tested at room temperature (25°C) using a LAND battery test system (Wuhan Landian Electronics Co., Ltd.). The charge and discharge current density was 0.3 mA / cm2, and the charge and discharge cut-off voltage was 3-5.0 V relative to Li / Li.

[0087] Example 2

[0088] Compared to Example 1, the only difference is that in mixture D, the binder polyvinyl butyral (PVB) accounts for 10 wt% of substance C, and the pore-forming agent (starch) accounts for 40 wt% of substance C. The resulting solid electrolyte has a porosity of 65%, a geometric density of 4.5 g / cm³, a tortuosity of 50°, and an ionic conductivity of 1 × 10⁻¹⁴ S / cm. Electrochemical performance was measured according to the method of Example 1. The results are shown in Table 1.

[0089] Example 3

[0090] Compared to Example 1, the only difference is that the temperature of the second heat treatment is 1300°C. The resulting solid electrolyte sheet has a porosity of 70%, a geometric density of 4.0 g / cm³, a tortuosity of 57°, and an ionic conductivity of 5×10⁻⁵ S / cm. Electrochemical performance was measured according to the method of Example 1. The results are shown in Figure 1.

[0091] Example 4

[0092] Compared to Example 1, the only difference is that after compacting, Mixture D was first heated to 450°C at a rate of 2°C / min and held for 8 hours, and then heated to 1100°C at a rate of 5°C / min and held for 10 hours to complete densification. The resulting solid electrolyte sheet had a porosity of 63%, a geometric density of 4.8 g / cm3, a tortuosity of 48°, and an ionic conductivity of 2×10^-4 S / cm. Electrochemical performance was measured according to the method of Example 1. The results are shown in Figure 1.

[0093] Example 5

[0094] Compared to Example 1, the only difference is that the lithium polymer solution is a solution of polyvinylidene fluoride (PVDF) and LiTFSI dissolved in NMP, with a mass ratio of PVDF / LiTFSI of 1, and a PVDF solids content of 10%. The resulting solid electrolyte has a porosity of 50%, a geometric density of 5.0 g / cm³, a tortuosity of 40°, and an ionic conductivity of 2.5 × 10⁻¹⁴ S / cm. Electrochemical performance was measured according to the method of Example 1. The results are shown in Figure 1.

[0095] Example 6

[0096] Compared to Example 1, the only difference is that an equal weight of polymethyl methacrylate (PMMA) is used instead of starch as the pore-forming agent. Other parameters and operations are the same as in Example 1. The resulting solid electrolyte has a porosity of 40%, a geometric density of 4.5 g / cm³, a tortuosity of 40°, and an ionic conductivity of 9 × 10^-5 S / cm.

[0097] Example 7

[0098] Compared with Example 1, the only difference is that equal weights of PVA are used to replace PVB and starch, that is, the content of PVA in mixture D is 35 wt.%.

[0099] The final solid electrolyte has a porosity of 45%, a geometric density of 4.3g / cm3, a curvature of 45°, and an ionic conductivity of 8×10^-5 S / cm.

[0100] Example 8

[0101] Compared with Example 1, the only difference was that naphthalene was used instead of starch as the pore-forming agent, no binder was used, and the total amount of binder and pore-forming agent added was the same as that in Example 1. After compaction, Mixture D was heated to 60°C at a rate of 1°C / min and then to 1200°C at a rate of 20°C / min and then to 600°C for 6 hours under an argon atmosphere to complete densification. Other parameters and operations were the same as in Example 1. The resulting solid electrolyte had a porosity of 47%, a geometric density of 4.6 g / cm3, a tortuosity of 47°, and an ionic conductivity of 9.5×10^-5 S / cm.

[0102] Example 9

[0103] Compared with Example 1, the only difference is that sulfur powder is used instead of starch as the pore-forming agent, and no binder is used. The total amount of binder and pore-forming agent added is the same as the total content of Example 1. After compaction, Mixture D is heated to 1100°C at a rate of 1°C / min for 3 hours and then to 1200°C at a rate of 20°C / min for 6 hours under an argon atmosphere to complete densification. Other parameters and operations are the same as those in Example 1. The resulting solid electrolyte has a porosity of 50%, a geometric density of 4.1 g / cm3, a tortuosity of 48°, and an ionic conductivity of 5.5×10^-5 S / cm.

[0104] Example 10

[0105] Compared with Example 1, the only difference is that no plasma cleaning machine is used for surface treatment. The performance is shown in Table 1.

[0106] Example 11

[0107] Compared with Example 1, the only difference is that PVB is not added to Mixture D, and the starch content therein is 35 wt.%; other operations, parameters and measurement methods are the same as in Example 1.

[0108] Comparative Example 1

[0109] Compared with Example 1, the only difference is that the pore former and binder are missing. The final solid electrolyte has a porosity of 5%, a geometric density of 5.3 g / cm3, and an ionic conductivity of 7×10^-4 S / cm. It cannot be cut into regular circular sheets (specifications: diameter 10 mm × 100 μm (thickness)). Figure 6 shown.

[0110] Comparative Example 2

[0111] Compared with Example 1, the only difference is that the starch pore-forming agent content in mixture D is 10 wt.%. The resulting solid electrolyte has a porosity of 15%, a geometric density of 5.1 g / cm3, and an ionic conductivity of 4 × 10^-4 S / cm. It can be cut into regular circular sheets (specifications: diameter 10 mm × 100 μm (thickness)), but the success rate is low and it is impossible to form a continuous three-dimensional structure. Figure 7 shown.

[0112] Comparative Example 3

[0113] Compared with Example 1, the only difference is that the solid electrolyte is formed by coating the film, and the steps are as follows: dissolving triethanolamine, electrolyte powder, polyvinyl butyral (PVP) and phenyl butyl phthalate (BBP) in a toluene solution with a total solid content of 20%, ball milling at 250 rpm for 12 h to obtain a uniform slurry, and coating the slurry on a PET plate with a coating of 150 μm by a doctor blade. However, this process cannot obtain a film of uniform thickness and cannot be peeled off. Figure 8 shown.

[0114] Comparative Example 4

[0115] Compared with Example 1, the only difference is that in the mixture D, no binder is used and only 70% of the pore-forming agent (starch) is added. The porous ceramic skeleton structure is basically collapsed, as shown in FIG. Figure 9 shown

[0116] Comparative Example 5:

[0117] Compared with Example 1, the only difference is that the sintered block was directly cut and then immersed in the lithium polymer solution. The results showed that the sintered block could not be cut into thin slices.

[0118] Comparative Example 6

[0119] Compared with Example 1, the only difference is that the first stage heat treatment is not performed. The obtained block-shaped dense porous embryo E is impure in phase and its structure is basically collapsed. Figure 10 shown.

[0120] It can be seen that by adopting the method of the present invention, the block can be successfully sliced ​​to obtain an ultra-thin solid electrolyte suitable for battery use. Without controlling the key means described in the present invention, it is difficult to successfully prepare the product and it is difficult to obtain stable battery application performance.

Claims

1. A method for preparing a ceramic-based composite solid electrolyte membrane, characterized in that: A raw material comprising a ceramic solid electrolyte material and a pore-forming agent is pressed into a shape to obtain a green block, which is then subjected to a multi-stage heat treatment to obtain a porous ceramic block; the multi-stage heat treatment process includes a first heat treatment process at 450-600° C. and a second heat treatment process at 1100-1200° C.; In the raw materials, the content of pore-forming agent is 15~45wt.%; The ceramic solid electrolyte material is at least one of a lithium oxide solid electrolyte and a lithium sulfide solid electrolyte; The pore-forming agent is starch; The porosity of porous ceramic blocks is 40-70%; soaking the porous ceramic block in a polymer solution and drying it to obtain a composite ceramic block; Cutting the composite ceramic block to obtain the ceramic-based composite solid electrolyte membrane; The thickness of the cut ceramic slices is 5μm~200μm.

2. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: Lithium oxide solid electrolyte is Li x La y TiO3, Li a Al b M1 2-b P3O g Or Li c La d M2 e Zr f O g One or more of, wherein 0.1<x<1, 0<y<1, 0.1<a<2, 0<b<2, 5<c<8, 1.5<d<4, 0.1<e<2, 0<f<2, 10<g<13, M1 is selected from one or more of Ge and Ti, and M2 is selected from one or more of Nb, Ta, Ga, and Al; The lithium sulfide solid electrolyte is one or more of LiPSX, LiSiPSX, LiGPS, and LiPS; X in LiPSX and LiSiPSX is Cl, Br or I.

3. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The particle size of the ceramic solid electrolyte material is less than or equal to 2 μm.

4. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 3, wherein: The particle size of the ceramic solid electrolyte material is 0.05-1.5 μm.

5. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: In the raw materials, the weight content of the pore-forming agent is 30-35wt.%.

6. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: A binder is also added to the raw materials; The binder is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polypropylene, ethylene propylene rubber, ethylene pentene copolymer, polyisobutylene, styrene butadiene rubber, poly(ethylene-co-methylene cyclopentene), polyethylene oxide, PEO block copolymer, silicone polymer, polyvinyl butyral, poly(vinyl acetate), polyvinyl pyrrolidine, poly(ethyl methacrylate), polyethylene glycol, polyvinyl alcohol, acrylic polymer, Paraloid series resin binder, Butylene series resin binder, and Mowit series resin binder.

7. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 6, wherein: In the raw materials, the weight content of the binder is less than or equal to 20wt.%.

8. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 7, wherein: In the raw materials, the weight content of the binder is 5-10wt.%.

9. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The pressing pressure is 10~500MPa.

10. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The atmosphere of the multi-stage heat treatment process is one or more of oxygen, argon, air, and dry air.

11. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The heating rate of the first heat treatment process is less than or equal to 20°C / min; The time of the first heat treatment process is 1~10h.

12. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 11, wherein: The heating rate of the first heat treatment process is 1~10℃ / min; The time of the first heat treatment process is 2~8h.

13. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The heating rate of the second heat treatment process is 5~100℃ / min; The temperature of the second heat treatment is 1150~1200℃; The second heat treatment process lasts for 1 to 20 hours.

14. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The porosity of porous ceramic blocks is 40-70%; Density is 4.0~5.5g / cm 3 .

15. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The polymer solution is an organic solution in which a polymer is dissolved; The polymer is one or more of polyethylene oxide, PEO block copolymer, PEO graft polymer, polymethyl methacrylate, polyacrylonitrile, polyimide, polyethylene glycol, polystyrene and polypropylene; The organic solvent in the polymer solution is at least one of acetonitrile, DMF, DME, NMP, toluene, tetrahydrofuran, DOL, chloroform, isopropanol, and ethanol; Conductive lithium salt is also added to the polymer solution; In the polymer solution, the concentration of the polymer is 1~30wt%; The weight ratio of the polymer to the conductive lithium salt is 1 to 10:

1.

16. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 15, wherein: The conductive lithium salt is one or more of lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium trifluoromethanesulfonate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate.

17. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The immersion process is carried out under negative pressure or positive pressure; The negative pressure is less than or equal to -0.1MPa; the positive pressure is greater than or equal to 0.1MPa.

18. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: The cutting method is one or more of diamond wire cutting, laser cutting and ion polishing.

19. The method for preparing a ceramic-based composite solid electrolyte membrane according to claim 1, wherein: performing surface treatment on the cut ceramic slices to obtain the ceramic-based composite solid electrolyte membrane; The surface treatment method is one or more of magnetron sputtering, ion polishing, metallographic polishing, electrochemical deposition, plasma cleaning, atomic layer deposition and chemical vapor deposition.

20. A ceramic-based composite solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 19.

21. An application of a ceramic-based composite solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 19, characterized in that: It is used to prepare solid-phase electrolytes for batteries.

22. The use according to claim 21, characterized in that It is used to prepare solid-phase electrolytes for lithium secondary batteries.

23. The use according to claim 22, characterized in that The lithium secondary battery is a lithium ion battery or a lithium metal battery.

24. A lithium secondary solid-state battery, characterized in that: A ceramic-based composite solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 19.

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