Composite solid electrolyte membrane, preparation method thereof and all-solid-state lithium metal battery

Abstract

The invention discloses a composite solid-state electrolyte membrane, a preparation method thereof and an all-solid-state lithium metal battery. The composite solid-state electrolyte membrane comprises a solid-state electrolyte layer, the interface modification layer is formed on at least one surface of the solid electrolyte layer and comprises a coated oxide solid electrolyte; the coated oxide solid electrolyte comprises a substrate, and a coating layer is formed on the surface of the substrate; the substrate is an oxide solid electrolyte, and the coating layer is prepared from (a) pure metal, or carbide, nitride or oxide thereof; or (b) a carbon material. According to the composite solid electrolyte membrane, a three-dimensional ion / electron transmission channel is constructed on the surface of the solid electrolyte layer, so that the interface ion / electron transmission efficiency can be optimized, the interface impedance can be reduced, the generation of lithium dendrites can be inhibited, and excellent interface stability can be provided.

Description

Technical Field

[0001] The present application belongs to the field of solid electrolyte technology, and specifically relates to a composite solid electrolyte membrane and a preparation method thereof, and also relates to an all-solid-state lithium metal battery containing the composite solid electrolyte membrane. Background Art

[0002] All-solid-state lithium metal batteries are primarily composed of lithium-containing cathode materials, lithium metal anodes, and solid-state electrolytes. They offer advantages such as high energy density, high safety, and long cycle life. However, all-solid-state lithium metal batteries currently suffer from the following issues: ① High interfacial impedance: Poor physical contact between the solid electrolyte and the lithium metal anode results in low interfacial lithium ion transport efficiency; ② Lithium dendrite growth: Interfacial defects can easily cause lithium dendrites to penetrate the electrolyte layer, posing a safety hazard; ③ Poor chemical stability: High-ionic conductivity solid electrolytes are either sulfide or halide systems, both of which are unstable to lithium metal.

[0003] One of the current solutions to the problems existing in all-solid-state lithium metal batteries is to introduce a modification layer or buffer layer on the surface of the solid electrolyte to inhibit side reactions and improve lithium ion transmission. However, these current modification layers or buffer layers are all two-dimensional planar modifications or modifications. Specifically, since the bond between lithium metal and the solid electrolyte is a surface-to-surface contact, and the solid surface cannot be completely flat, there will be a large number of interface gaps, which will affect the transmission of interface materials. The modification layer or buffer layer will only compensate for the material transmission between the surfaces to a certain extent, but it will also limit the interface transmission efficiency. Summary of the Invention

[0004] In view of this, the primary purpose of the present application is to provide a composite solid electrolyte membrane, which optimizes the interface ion / electron transmission efficiency, reduces the interface impedance, inhibits the formation of lithium dendrites, and provides excellent interface stability by constructing a three-dimensional ion / electron transmission channel on the surface of the solid electrolyte layer.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] One aspect of the present application discloses a composite solid electrolyte membrane, comprising:

[0007] solid electrolyte layer;

[0008] and an interface modification layer formed on at least one surface of the solid electrolyte layer, the interface modification layer comprising a coated oxide solid electrolyte;

[0009] The coated oxide solid electrolyte comprises a substrate, and a coating layer is formed on the surface of the substrate; the substrate is an oxide solid electrolyte, and the coating layer is:

[0010] (a) pure metals, or their carbides, nitrides, or oxides;

[0011] or (b) carbon materials.

[0012] In the present application, a coating is formed on the surface of an oxide solid electrolyte to obtain a nanopowder of a coated oxide solid electrolyte, which is then formed into a film on the surface of the solid electrolyte layer. The oxide solid electrolyte powder is constructed between the faces to provide a higher ion conductivity at the interface, and the coating on the surface is simultaneously in situ lithiated, providing a higher electronic conduction and a relatively weaker ion conduction. The interface modification layer is formed by stacking multiple layers of nanopowder, and the coating layers are interconnected to form a wide range of three-dimensional material transmission channels. The three-dimensional interface modification layer can not only better regulate the distribution of the nanopowder so that it is evenly distributed, but also better play the ion conduction of the oxide solid electrolyte and the electronic conductivity of the coating layer. The interface material transfer efficiency and interface stability are improved, and the growth of lithium dendrites is suppressed.

[0013] Another aspect of the present application discloses a method for preparing a composite solid electrolyte membrane, comprising the following steps:

[0014] providing a solid electrolyte layer;

[0015] forming a coating layer on the surface of the oxide solid electrolyte to obtain a coated oxide solid electrolyte;

[0016] A coated oxide solid electrolyte is formed on the surface of the solid electrolyte layer to prepare a composite solid electrolyte membrane.

[0017] Another aspect of the present application provides an all-solid-state lithium metal battery, comprising a positive electrode and a negative electrode, and also containing the composite solid-state electrolyte membrane.

[0018] Beneficial effects of this application:

[0019] This application uses an oxide solid electrolyte as a matrix, forms a coating layer on its surface, and forms a nanostructured coated oxide solid electrolyte. The nanostructured oxide stacking is used to form a three-dimensional interface bonding effect. The oxide solid electrolyte has a certain ion transmission efficiency and can provide a fast ion / electron transmission channel. The coating layer formed on the surface of the oxide solid electrolyte can undergo an in-situ lithiation reaction and become an ion / electron conductor, further enhancing the ion / electron conduction between lithium metal and the solid electrolyte. In addition, the nano-stacked layer can form a continuous network structure in the interface modification layer, thereby constructing a three-dimensional ion / electron transmission channel and improving the interface material transmission efficiency.

[0020] In addition, in this application, the nano-coated oxide solid electrolyte is used as an interface modification layer, which can achieve good compatibility with lithium metal, isolate lithium metal from the solid electrolyte, inhibit interfacial reactions, and stabilize the interface; and a three-dimensional continuous ion-electron conduction can be formed between the nano-coated oxide solid electrolyte and the lithium metal, so that the lithium metal can be uniformly deposited at the interface, which can avoid the formation of lithium dendrites caused by excessive local current density due to uneven ion conduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The electrochemical impedance spectroscopy (EIS) test results of the composite solid electrolyte membrane in Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the embodiments of the present application. The technical solutions in the embodiments described below are exemplary and are only possible technical implementations of the present application, not all possible implementations. Those skilled in the art can fully combine the embodiments of the present application to obtain other embodiments without creative work, and these embodiments are also within the scope of protection of the present application.

[0023] The first aspect of the present application provides a composite solid electrolyte membrane, comprising a solid electrolyte layer; and an interface modification layer formed on at least one surface of the solid electrolyte layer, the interface modification layer comprising a coated oxide solid electrolyte; wherein the coated oxide solid electrolyte comprises a substrate, and a coating layer is formed on the surface of the substrate; the substrate is an oxide solid electrolyte, and the coating layer is (a) a pure metal, or its carbide, or its nitride, or its oxide; or (b) a carbon material.

[0024] The present application constructs a three-dimensional interface modification layer on the surface of the solid electrolyte layer, and the interface modification layer is formed by a nano-scale coated oxide solid electrolyte. The oxide solid electrolyte itself has a certain ion transmission efficiency and can form an ion transmission channel between the lithium metal electrode and the solid electrolyte layer; at the same time, a coating layer composed of pure metal, carbide, nitride, oxide or carbon material is coated on its surface. The coating layer can undergo in-situ lithiation reaction and become a lithium ion / electron conductor, thereby enhancing the ion transmission and electron transmission between the lithium metal and the solid electrolyte. More importantly, by stacking nano-sized powders, coordinating the in-situ lithiation of the surface coating layer and the lithium metal, a continuous network structure is formed in the interface modification layer, constructing a three-dimensional ion / electron transmission channel.

[0025] In the present application, the solid electrolyte layer can be a common solid electrolyte material in the art without special restrictions. In some examples, the material of the solid electrolyte layer is a halide electrolyte or a sulfide electrolyte.

[0026] As an example, the composition of the halide electrolyte is Li3MB6, wherein M is any one of Y, Zr, In, Sc, Ta or La or a combination of at least two thereof, and B is selected from any one of Cl, Br or I or a combination of at least two thereof.

[0027] As an example, the composition of the sulfide electrolyte may be Li (6-x) PS (5-x) X (1+x) (X=Cl, Br, I, 0≤x≤0.6, for example, it can be 0, 0.2, 0.4, 0.5 or 0.6, etc.), it can also be xLi2S·(1-x)P2S5 (0.2≤x≤0.8, for example, it can be 0.2, 0.3 or 0.5), or it can be any one of Li3PS4 or a combination of at least two.

[0028] In some specific examples of this application, the halide electrolyte is Li3InCl6, and the sulfide electrolyte is Li 5.5 PS 4.5 X 1.5 .

[0029] It will be understood that there is no particular limitation on the thickness of the solid electrolyte layer in the present application, and the conventional thickness in the art can be adopted. In some examples, the thickness of the solid electrolyte layer is 10 to 100 μm, for example, it can be any thickness of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 95 μm, 100 μm, or any range between two of them.

[0030] In some examples, the thickness of the interface modification layer is 0.5-5 μm, for example, any thickness of 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any range therebetween.

[0031] In the present application, the interface modification layer can be formed on at least one surface of the solid electrolyte layer. Specifically, the solid electrolyte layer has two surfaces opposite to each other in the thickness direction, and the interface modification layer can be formed on at least one of the two surfaces. In some preferred examples of the present application, the interface modification layer is formed on the surface of the negative electrode side of the solid electrolyte layer.

[0032] In the present application, the interface modification layer is formed by a coated oxide solid electrolyte, the matrix of the coated oxide solid electrolyte is an oxide solid electrolyte, and a coating layer is formed on the surface of the matrix.

[0033] In some examples, the oxide solid electrolyte includes any one of a garnet-type solid electrolyte, a perovskite-type solid electrolyte, a NASICON-type solid electrolyte, and a LiPON-type solid electrolyte, preferably a garnet-type solid electrolyte. In some specific examples, the garnet-type solid electrolyte can be, for example, lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), lithium titanium zirconium oxide (LZTO), lithium lanthanum titanium zirconium oxide (LLZTO), etc., but is not limited thereto. As an example, the particle size of the oxide solid electrolyte is 20 to 200 nm, for example, 20 nm, 40 nm, 50 nm, 80 nm, 100 nm, 110 nm, 120 nm, 150 nm, 170 nm, 200 nm, or any range between the two.

[0034] In the present application, the coating layer is pure metal N, N carbide, N nitride, N oxide, or carbon material. N is one or a combination of two or more of Al, Zn, Si, Mg, Sn, Zr, Ti, and W. These coating layer materials can be in-situ lithiated, thereby enhancing ion / electron transport, and interconnecting the coating layers in the interface modification layer, cooperating with the oxide solid electrolyte in the matrix to construct a three-dimensional network, thereby improving ion / electron conduction.

[0035] In some examples, the coating layer is N oxide, and the oxide is one or a composite of two or more of Al2O3, ZnO, SiO2, MgO, SnO2, ZrO2, TiO2, and WO3.

[0036] In other examples, the coating layer is a carbon material, and the carbon material is one or a composite of two or more of graphite, acetylene black, graphene, and carbon black.

[0037] In the present application, the thickness of the coating layer is nanometer scale. As an example, the thickness of the coating layer is 5 to 30 nm, for example, it can be 5 nm, 7 nm, 10 nm, 11 nm, 15 nm, 18 nm, 20 nm, 25 nm, 30 nm or any range value therebetween.

[0038] The second aspect of the present application discloses a method for preparing the composite solid electrolyte membrane, comprising the following steps:

[0039] providing a solid electrolyte layer;

[0040] forming a coating layer on the surface of the oxide solid electrolyte to obtain a coated oxide solid electrolyte;

[0041] A coated oxide solid electrolyte is formed on the surface of the solid electrolyte layer to prepare a composite solid electrolyte membrane.

[0042] There are no special requirements for the method of obtaining the coated oxide solid electrolyte, and it can be prepared by methods well known in the art such as liquid phase method and solid phase method.

[0043] As an example, the coating layer is a metal oxide, and its formation process is as follows: the oxide solid electrolyte is dispersed in a metal precursor solution, and after drying through sol-gel or direct heating, high-temperature heat treatment is performed to form a coating layer on the surface of the oxide solid electrolyte. The metal precursor solution is formed by dispersing a metal precursor, typically a metal salt, in a solvent (such as water, ethanol, etc.).

[0044] As an example, the coating layer is a carbon material, and its formation process is: using a ball milling process, grinding the carbon material grinding medium and the oxide solid electrolyte, and in-situ coating the carbon layer on the surface of the oxide solid electrolyte.

[0045] In the present application, there are no particular requirements for the film formation method of the coated oxide solid electrolyte on the surface of the solid electrolyte layer, and methods well known in the art can be used. In some preferred examples, the film formation method used is a casting method, which can easily form a uniform and thin interface modification layer.

[0046] The third aspect of the present application discloses an all-solid-state lithium metal battery, comprising a positive electrode and a negative electrode, and also containing the composite solid-state electrolyte membrane.

[0047] There are no special requirements for the positive electrode, and positive electrode materials well known in the art can be used.

[0048] The negative electrode is lithium metal or an alloy of lithium metal and other metals.

[0049] The following are specific embodiments of the present application. It should be noted that the following specific embodiments are only for illustrative purposes and do not limit the scope of the present application in any way.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0051] In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used are all commercially available.

[0052] Example 1

[0053] This embodiment provides a method for preparing a composite solid electrolyte membrane, and the specific steps are as follows:

[0054] 1. Preparation of Al2O3-coated Li7La3Zr2O by sol-gel method 12

[0055] Lithium nitrate, lanthanum nitrate and zirconium nitrate were prepared into a nitrate solution at a molar ratio of Li:La:Zr=7:3:2, wherein the concentration of lithium nitrate was 0.007M. After complexation with EDTA (0.008M) and spray drying, Li7La3Zr2O was obtained by sintering at 900℃ for 6h. 12 Nanoparticles (abbreviated as LLZO), with D50=150nm.

[0056] Li7La3Zr2O 12 The nanoparticles were dispersed in aluminum isopropoxide / ethanol solution (the concentration of aluminum isopropoxide was 0.1 M), hydrolyzed at 80 ° C for 12 h, and then annealed at 600 ° C for 2 h to prepare Al2O3-coated Li7La3Zr2O 12 , wherein the thickness of the Al2O3 layer is 5nm.

[0057] 2. Preparation of composite solid electrolyte membrane

[0058] Al2O3 coated Li7La3Zr2O 12 The particles and PVDF-HFP were mixed in a cyclohexane solution in a mass ratio of 9:1 (solid content of 55wt%), cast into a film on the surface of the halide electrolyte Li3InCl6, and vacuum dried at 60°C to obtain a composite solid electrolyte membrane, wherein the thickness of the interface modification layer was 3μm and the thickness of the halide electrolyte was 30μm.

[0059] This embodiment further provides an all-solid-state lithium metal battery assembled based on the above composite solid electrolyte membrane:

[0060] The composite solid electrolyte membrane and the lithium metal electrode with a thickness of 450 μm were assembled into Li / Al2O3-Li7La3Zr2O 12 / Li lithium metal symmetric battery, the lithium metal symmetric battery at 0.2mA / cm 2 There is no short circuit during the next 1000h cycle.

[0061] Comparative Example 1

[0062] This comparative example provides a solid electrolyte membrane, which differs from Example 1 in that no interface modification layer is provided on the surface of the solid electrolyte, namely, a halide electrolyte Li3InCl6 with a thickness of 30 μm.

[0063] Comparative Example 2

[0064] This comparative example provides a composite solid electrolyte membrane, which is similar to the embodiment 1 except that: Li7La3Zr2O 12 The particles are coated. 12 The particles were tape-casted onto the surface of the halide electrolyte Li3InCl6 in the same manner as in Example 1. The other process steps and conditions were the same as in Example 1.

[0065] Comparative Example 3

[0066] This comparative example provides a composite solid electrolyte membrane, similar to that of Example 1, except that Al2O3 (100 nm) was tape-cast onto the surface of the halide electrolyte Li3InCl6 in the same manner as in Example 1. All other process steps and conditions were the same as in Example 1.

[0067] Comparative Example 4

[0068] This comparative example provides a composite solid electrolyte membrane, which is similar to the embodiment 1 except that Al2O3 nanopowder and Li7La3Zr2O 12 The nanoparticles were simply blended in a mass ratio of 1:99 and then tape-casted onto the surface of the halide electrolyte Li3InCl6 in the same manner as in Example 1. Other process steps and conditions were the same as in Example 1.

[0069] Comparative Example 5

[0070] This comparative example provides a composite solid electrolyte membrane, which is similar to the embodiment 1 in that the matrix Li7La3Zr2O in the coated oxide solid electrolyte is 12 The powder (D50 = 1 μm) was coated with an Al2O3 layer having a thickness of 5 nm. An interface modification layer was formed on the surface of the halide electrolyte Li3InCl6 by the method of Example 1. The other process steps and conditions were the same as those of Example 1.

[0071] Example 2

[0072] This embodiment provides a method for preparing a composite solid electrolyte membrane, and the specific steps are as follows:

[0073] 1. Preparation of ZnO-coated modified Li by solid phase method 6.55 La3Zr 1.5 Ta 0.5 O 12

[0074] Lithium hydroxide LiOH, lanthanum oxide La2O3, zirconium oxide ZrO2, and tantalum oxide Ta2O5 were prepared in a molar ratio of Li:La:Zr:Ta=6.55:3:1.5:0.5, mixed evenly by ball milling, and sintered at 800℃ for 6h and 1000℃ for 6h to obtain a pure phase sample; then, Li was obtained by ball milling and sand milling. 6.55 La3Zr 1.5 Ta 0.5 O 12 Nanoparticles (abbreviated as LLZTO), with D50=50nm.

[0075] Li 6.55 La3Zr 1.5 Ta 0.5 O 12 The nanoparticles were dispersed in zinc nitrate / ethanol solution (zinc nitrate concentration 0.1 M), heated at 80 °C with stirring until completely dry, and then annealed at 500 °C for 2 h to obtain ZnO-coated modified Li 6.55 La3Zr 1.5 Ta 0.5 O 12 , wherein the thickness of the ZnO layer is 5 nm.

[0076] 2. Preparation of composite solid electrolyte membrane

[0077] ZnO coated modified Li 6.55 La3Zr 1.5 Ta 0.5 O 12 Dispersed in toluene solution (solid content 55wt%), cast on sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 The surface was dried in vacuum at 60° C. to obtain a composite solid electrolyte membrane, wherein the thickness of the interface modification layer was 3 μm and the thickness of the sulfide electrolyte was 30 μm.

[0078] This embodiment further provides an all-solid-state lithium metal battery assembled based on the above composite solid electrolyte membrane:

[0079] The composite solid electrolyte membrane and the lithium metal electrode with a thickness of 450 μm were assembled into a Li / ZnO-Li 6.55 La3Zr 1.5 Ta 0.5 O 12 / Li lithium metal symmetric battery, the lithium metal symmetric battery at 0.3mA / cm 2 There is no short circuit during the next cycle of 1500h.

[0080] Example 3

[0081] This embodiment provides a method for preparing a composite solid electrolyte membrane, and the specific steps are as follows:

[0082] 1. Preparation of SiO2-coated Li7La3Zr2O by sol-gel method 12

[0083] Li7La3Zr2O with D50=150nm was prepared by referring to the method in Example 1. 12 Nanoparticles.

[0084] Li7La3Zr2O 12 The nanoparticles were dispersed in tetraethyl silicate / ethanol solution (tetraethyl silicate concentration 0.1 M), hydrolyzed at 80 ° C for 12 h, and then annealed at 600 ° C for 2 h to prepare SiO2-coated Li7La3Zr2O 12 , wherein the thickness of the SiO2 layer is 5nm.

[0085] 2. Preparation of composite solid electrolyte membrane

[0086] SiO2 coated Li7La3Zr2O 12 The particles and PVDF-HFP were mixed in a cyclohexane solution in a mass ratio of 9:1 (solid content of 55wt%), cast into a film on the surface of the halide electrolyte Li3InCl6, and vacuum dried at 60°C to obtain a composite solid electrolyte membrane, wherein the thickness of the interface modification layer was 3μm and the thickness of the halide electrolyte was 30μm.

[0087] This embodiment further provides an all-solid-state lithium metal battery assembled based on the above composite solid electrolyte membrane:

[0088] The composite solid electrolyte membrane and the lithium metal electrode with a thickness of 450 μm were assembled into Li / SiO2-Li7La3Zr2O 12 / Li lithium metal symmetric battery, the lithium metal symmetric battery at 0.2mA / cm 2 There is no short circuit during the next 1000h cycle.

[0089] Example 4

[0090] This embodiment provides a method for preparing a composite solid electrolyte membrane, and the specific steps are as follows:

[0091] 1. Preparation of MgO-coated Li7La3Zr2O by sol-gel method 12

[0092] Li7La3Zr2O with D50=150nm was prepared by referring to the method in Example 1. 12 Nanoparticles.

[0093] Li7La3Zr2O12 The nanoparticles were dispersed in a magnesium nitrate / ethanol solution (magnesium nitrate concentration 0.1 M), hydrolyzed at 80 °C for 12 h, and then annealed at 600 °C for 2 h to prepare MgO-coated Li7La3Zr2O 12 , wherein the thickness of the MgO layer is 5 nm.

[0094] 2. Preparation of composite solid electrolyte membrane

[0095] MgO coated Li7La3Zr2O 12 The particles and PVDF-HFP were mixed in a cyclohexane solution in a mass ratio of 9:1 (solid content of 55wt%), cast into a film on the surface of the halide electrolyte Li3InCl6, and vacuum dried at 60°C to obtain a composite solid electrolyte membrane, wherein the thickness of the interface modification layer was 3μm and the thickness of the halide electrolyte was 30μm.

[0096] This embodiment further provides an all-solid-state lithium metal battery assembled based on the above composite solid electrolyte membrane:

[0097] The composite solid electrolyte membrane and the lithium metal electrode with a thickness of 450 μm were assembled into Li / MgO-Li7La3Zr2O 12 / Li lithium metal symmetric battery, the lithium metal symmetric battery at 0.2mA / cm 2 There is no short circuit during the next 1000h cycle.

[0098] Example 5

[0099] This embodiment provides a method for preparing a composite solid electrolyte membrane, which is similar to the method of embodiment 1, except that: Li7La3Zr2O 12 The particle size D50 is 20 nm, and the thickness of the Al2O3 layer is 5 nm. The other process steps and condition parameters are the same as those in Example 1.

[0100] Example 6

[0101] This embodiment provides a method for preparing a composite solid electrolyte membrane, which is similar to the method of embodiment 1, except that: Li7La3Zr2O 12 The particle size D50 of the Al2O3 layer is 20 nm, the thickness of the Al2O3 layer is 5 nm, and the thickness of the interface modification layer is 5 μm. The other process steps and condition parameters are the same as those in Example 1.

[0102] Example 7

[0103] This embodiment provides a method for preparing a composite solid electrolyte membrane, which is similar to the method of embodiment 1, except that: Li7La3Zr2O 12The particle size D50 is 200 nm, and the thickness of the Al2O3 layer is 30 nm. The other process steps and condition parameters are the same as those in Example 1.

[0104] Example 8

[0105] This example provides a method for preparing a composite solid electrolyte membrane. The method is similar to that of Example 1, with the only differences being that the thickness of the Al2O3 coating layer in the coated oxide solid electrolyte is 30 nm, and the thickness of the interface modification layer is 1 μm. All other process steps and conditions are the same as those of Example 1.

[0106] Example 9

[0107] This example provides a method for preparing a composite solid electrolyte membrane. The method is similar to that of Example 1, with the only differences being that the thickness of the Al2O3 coating layer in the coated oxide solid electrolyte is 20 nm, and the thickness of the interface modification layer is 500 nm. All other process steps and conditions are the same as those of Example 1.

[0108] Example 10

[0109] This embodiment provides a method for preparing a composite solid electrolyte membrane, and the specific steps are as follows:

[0110] 1. Preparation of carbon-coated Li7La3Zr2O 12

[0111] Li7La3Zr2O with D50=150nm was obtained by referring to the method of Example 1 12 Nanoparticles.

[0112] Li7La3Zr2O 12 The nanoparticles and hard graphite balls were placed in a ball mill and milled at 500 rpm for 2 h to obtain carbon-coated Li7La3Zr2O 12 Powder, the thickness of the carbon coating is 20nm.

[0113] 2. Preparation of composite solid electrolyte membrane

[0114] Carbon-coated Li7La3Zr2O 12 The powder and PVDF-HFP were mixed in a cyclohexane solution in a mass ratio of 9:1 (solid content of 55wt%), cast into a film on the surface of the halide electrolyte Li3InCl6, and vacuum dried at 60°C to obtain a composite solid electrolyte membrane, wherein the thickness of the interface modification layer was 3μm and the thickness of the halide electrolyte was 30μm.

[0115] This embodiment further provides an all-solid-state lithium metal battery assembled based on the above composite solid electrolyte membrane:

[0116] The composite solid electrolyte membrane and the lithium metal electrode with a thickness of 450 μm were assembled into Li / C-Li7La3Zr2O 12 / Li lithium metal symmetric battery, the lithium metal symmetric battery at 0.15mA / cm 2 There is no short circuit during the next cycle of 800h.

[0117] Example 11

[0118] This embodiment provides a method for preparing a composite solid electrolyte membrane, and the specific steps are as follows:

[0119] 1. Preparation of carbon-coated Li 6.55 La3Zr 1.5 Ta 0.5 O 12

[0120] Li with D50=50nm was prepared by referring to the method of Example 2. 6.55 La3Zr 1.5 Ta 0.5 O 12 Nanoparticles.

[0121] Li 6.55 La3Zr 1.5 Ta 0.5 O 12 The carbon-coated Li 6.55 La3Zr 1.5 Ta 0.5 O 12 Powder, the thickness of the carbon coating is 20nm.

[0122] 2. Preparation of composite solid electrolyte membrane

[0123] Carbon-coated Li 6.55 La3Zr 1.5 Ta 0.5 O 12 The particles were dispersed in a toluene solution (solid content 55 wt%) and cast onto a sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 The surface was dried in vacuum at 60° C. to obtain a composite solid electrolyte membrane, wherein the thickness of the interface modification layer was 3 μm and the thickness of the sulfide electrolyte was 30 μm.

[0124] This embodiment further provides an all-solid-state lithium metal battery assembled based on the above composite solid electrolyte membrane:

[0125] The composite solid electrolyte membrane and the lithium metal electrode with a thickness of 450 μm were assembled into a Li / C-Li 6.55 La3Zr 1.5 Ta 0.5 O 12 / Li lithium metal symmetric battery, the lithium metal symmetric battery at 0.25mA / cm 2 There is no short circuit during the next cycle of 1200h.

[0126] Table 1 Composition of the composite solid electrolyte membrane in the examples and comparative examples

[0127]

[0128] Performance Testing

[0129] The composite solid electrolyte membranes in the examples and comparative examples were assembled into symmetrical button cells according to the following method:

[0130] The thickness of the lithium metal is 450 μm and the diameter is 15 mm; the diameter of the composite solid electrolyte membrane is 18 mm; the lithium metal, the composite solid electrolyte membrane (the interface modification layer is located on the negative electrode side), and the lithium metal are assembled in this order at a pressure of 15 MPa to obtain a button symmetrical battery.

[0131] 1. Interface impedance

[0132] The assembled symmetrical button cell was tested for AC impedance at room temperature (25°C) with a test frequency of 1MHz to 1Hz and an amplitude of 20mV. Figure 1 .

[0133] 2. Lithium dendrites

[0134] The lithium metal button symmetrical battery was subjected to constant current charge and discharge test, with the initial charge and discharge current of 0.1mA / cm 2 The charge and discharge time is 1h each. After one cycle of charge and discharge is completed, the current density increases by 0.1mA / cm 2 , until the polarization voltage of the lithium metal symmetric cell reaches zero, at which point the symmetric cell is considered to have an internal short circuit due to lithium dendrite growth. The current at the short circuit is the critical current density of the electrolyte. A higher critical current density indicates a more resistant solid electrolyte to lithium dendrite growth.

[0135] 3. Stability

[0136] The lithium metal button symmetrical battery was subjected to constant current charge and discharge test, and the charge and discharge current was constant at 0.2mA / cm 2 The charge and discharge time is 1 hour each. The polarization voltage of the lithium metal symmetric battery is observed. When the polarization voltage is greater than 0.2V, the interface is considered unstable and the battery cycle is terminated.

[0137] Table 2 Performance test results

[0138]

[0139] According to the table above, the interface impedance, resistance to lithium dendrite growth, and interface stability of the embodiment are better than those of the comparative example by introducing the nano-interface layer material. By comparing Example 1 with Example 5, it can be found that the higher the degree of nano-interface layer, the more conducive it is to three-dimensional ion and electron conduction, and the better the performance of the interface layer. In comparative example 1, there is no interface layer material. Due to the incompatibility between lithium metal and halide, side reactions will occur at the interface, resulting in a very large interface impedance. Figure 1 This can also be seen in the electrochemical impedance spectroscopy (EIS) test results. Example 1 and Comparative Example 2 reflect that when nano-LLZO is simply used as the interface layer, there is no transition layer between lithium metal and LLZO, and the interface impedance is relatively large, which greatly reduces the cycle life of the lithium metal symmetric battery. Comparative Example 3, which only uses Al2O3 as the interface layer, has a very large impedance at the interface because it is a non-lithium ion conductor. Example 1 and Comparative Example 4 illustrate that since Al2O3 is a non-ionic conductor, simple blending has very limited improvement on the ion / electron conduction effect. Comparative Example 5 illustrates that large micron-sized particles of LLZO are relatively hard, and the affinity between micron LLZO and lithium metal is poor, the solid-solid contact is obvious, and the ion transport is hindered, resulting in a very large interface impedance.

[0140] In summary, by introducing suitable interface layer materials between the solid electrolyte and lithium metal, the occurrence of interface side reactions can be effectively suppressed. By coating the oxide solid electrolyte and constructing a three-dimensional lithium-philic interface layer, the affinity between lithium metal and the oxide solid electrolyte can be greatly improved. At the same time, the transmission of lithium ions and electrons at the interface can be improved, the impedance between the lithium metal interface layers can be greatly reduced, and the growth of lithium dendrites can be suppressed, thereby ensuring that the lithium metal solid-state battery can be stably cycled under large currents.

[0141] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite solid electrolyte membrane, characterized in that: include: solid electrolyte layer; and an interface modification layer formed on at least one surface of the solid electrolyte layer, the interface modification layer comprising a coated oxide solid electrolyte; The coated oxide solid electrolyte comprises a substrate, and a coating layer is formed on the surface of the substrate; the substrate is an oxide solid electrolyte, and the coating layer is: (a) pure metals, or their carbides, nitrides, or oxides; or (b) carbon materials; Preferably, the thickness of the interface modification layer is 0.5 to 5 μm.

2. The composite solid electrolyte membrane according to claim 1, wherein The material of the solid electrolyte layer is a halide electrolyte or a sulfide electrolyte; And / or, the thickness of the solid electrolyte layer is 10 to 100 μm.

3. The composite solid electrolyte membrane according to claim 1, wherein The particle size of the oxide solid electrolyte is 20 to 200 nm; the thickness of the coating layer is 5 to 30 nm.

4. The composite solid electrolyte membrane according to claim 1, wherein The oxide solid electrolyte is a garnet-type oxide solid electrolyte.

5. The composite solid electrolyte membrane according to claim 1, wherein The coating layer is an oxide, and the oxide is one or a composite of two or more of Al2O3, ZnO, SiO2, MgO, SnO2, ZrO2, TiO2, and WO3.

6. The composite solid electrolyte membrane according to claim 1, wherein The coating layer is made of a carbon material, and the carbon material is one or a composite of two or more of graphite, acetylene black, graphene, and carbon black.

7. A method for preparing a composite solid electrolyte membrane according to any one of claims 1 to 6, characterized in that: The following steps are involved: providing a solid electrolyte layer; forming a coating layer on the surface of the oxide solid electrolyte to obtain a coated oxide solid electrolyte; forming a coated oxide solid electrolyte film on the surface of the solid electrolyte layer to prepare a composite solid electrolyte membrane; Preferably, the film forming method is a casting method.

8. The preparation method according to claim 7, wherein The coating layer is an oxide, and its formation process is: dispersing the oxide solid electrolyte in a metal precursor solution, drying it through sol-gel or direct heating, and then performing high-temperature heat treatment to form a coating layer on the surface of the oxide solid electrolyte.

9. The preparation method according to claim 7, wherein The coating layer is made of carbon material, and its forming process is: using a ball milling process, grinding the carbon material grinding medium with the oxide solid electrolyte, and in-situ coating the carbon layer on the surface of the oxide solid electrolyte.

10. An all-solid-state lithium metal battery, comprising a positive electrode and a negative electrode, characterized in that: It also contains the composite solid electrolyte membrane according to any one of claims 1 to 9.

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