An all-solid-state lithium metal battery interface protection layer and its preparation method and application

Abstract

The present invention provides an all-solid-state lithium metal battery interface protection layer, a preparation method and application thereof, belonging to the technical field of negative electrode materials in all-solid-state battery systems. The interface protection layer has a single-layer structure or a multi-layer structure; the single-layer structure is composed of Li6PS5Cl and conductive carbon, and the mass ratio of the Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5; or the single-layer structure is composed of Li6PS5Cl and a lithium-philic element M, and the mass ratio of the Li6PS5Cl to the lithium-philic element M is 75:25; the multi-layer structure is formed by stacking several interface layers, the interface layers are composed of Li6PS5Cl and conductive carbon, and the mass ratio of the Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5; and in the several interface layers, the content of the conductive carbon increases layer by layer. The interface protection layer has gradient conductivity, which effectively induces uniform deposition of lithium while ensuring the internal ion and electron transmission of the all-solid-state lithium metal battery, thereby improving the cycle stability and safety of the all-solid-state lithium metal battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative electrode materials in all-solid-state battery systems, and in particular relates to an all-solid-state lithium metal battery interface protection layer and a preparation method and application thereof. Background Art

[0002] Since the advent of commercial lithium-ion batteries in the 1990s, they have had a profound impact on our society over the past 30 years. However, the energy density of commercial batteries is currently limited to about 300 Wh kg. -1 , and cannot fully meet the ever-increasing energy storage needs of contemporary society in terms of consumer electronics, electric vehicle endurance, etc. The use of metallic lithium negative electrodes is critical to significantly improving the energy density of batteries. Due to some inherent problems of lithium metal batteries, the lithium delithiation / lithiation efficiency (Coulomb efficiency) of lithium metal during the cycle process is reduced. The main reasons are the growth of lithium dendrites during the cycle, side reactions between the electrolyte and the electrode, and the generation of dead lithium, which greatly reduces the cycle stability and safety of all-solid-state lithium metal batteries, and seriously hinders the widespread application of all-solid-state lithium metal batteries. Summary of the Invention

[0003] In order to solve the problems of poor cycle stability and safety of existing all-solid-state lithium metal batteries, the present invention provides an all-solid-state lithium metal battery interface protection layer, which has gradient conductivity. While ensuring the internal ion and electron transmission of the all-solid-state lithium metal battery, it effectively induces the uniform deposition of lithium, thereby improving the cycle stability and safety of the all-solid-state lithium metal battery.

[0004] The present invention also provides a preparation method and application of an all-solid-state lithium metal battery interface protection layer.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides an interface protection layer for an all-solid-state lithium metal battery, wherein the interface protection layer is a single-layer structure or a multi-layer structure;

[0007] The single-layer structure is composed of Li6PS5Cl and conductive carbon, and the mass ratio of Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5;

[0008] Alternatively, the single-layer structure is composed of Li6PS5Cl and a lithium-philic element M, and the mass ratio of Li6PS5Cl to the lithium-philic element M is 75:25;

[0009] The multilayer structure is formed by stacking several interface layers, wherein the interface layer is composed of Li6PS5Cl and conductive carbon, and the mass ratio of Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5;

[0010] In the several interface layers, the content of the conductive carbon increases layer by layer.

[0011] Optionally, the thickness of the interface protection layer is 5 to 200 μm.

[0012] Optionally, the conductive carbon includes at least one of graphite, Super P, carbon nanotubes, carbon black and Ketjen black;

[0013] The lithium-philic element M is at least one of Cu, Zn, Mg, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn.

[0014] Based on the same inventive concept, the present invention provides a method for preparing an interface protective layer for an all-solid-state lithium metal battery, the preparation method comprising:

[0015] The solid electrolyte Li6PS5Cl and the conductive carbon are mixed and ground under an inert atmosphere to obtain a mixture A, wherein the mass ratio of the Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5;

[0016] Alternatively, the solid electrolyte Li6PS5Cl and the lithium-philic element M are mixed in a mass ratio of 75:25 under an inert atmosphere and then ground to obtain a mixture B;

[0017] coating or depositing the mixture A or the mixture B on a substrate surface to obtain a single-layer structure;

[0018] Alternatively, a plurality of the mixtures A having different conductive carbon contents are coated or deposited layer by layer on the substrate surface in order of increasing conductive carbon content to obtain a multilayer structure.

[0019] Furthermore, the particle size of the particles in the mixture A is 1 to 5 μm;

[0020] The particle size of the particles in the mixture B is 1 to 5 μm;

[0021] The conductive carbon comprises at least one of graphite, Super P, carbon nanotubes, carbon black and Ketjen black;

[0022] The lithium-philic element M is at least one of Cu, Zn, Mg, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn.

[0023] Furthermore, coating or depositing the mixture A or the mixture B on the surface of a substrate to obtain a single-layer structure specifically includes:

[0024] The mixture A or the mixture B is coated on the surface of the substrate, and then a pressure of 300 to 500 MPa is applied to obtain a single-layer structure;

[0025] Alternatively, the mixture A or the mixture B is attached to the surface of a substrate by atomic layer deposition to obtain a single-layer structure;

[0026] The method of coating or depositing the plurality of mixtures A having different conductive carbon contents on the substrate surface layer by layer in ascending order of conductive carbon contents to obtain a multilayer structure specifically includes:

[0027] The mixtures A having different conductive carbon contents are coated layer by layer on the substrate surface according to the conductive carbon content from low to high, and then a pressure of 300 to 500 MPa is applied to obtain a multilayer structure;

[0028] Alternatively, a plurality of the mixtures A having different conductive carbon contents are deposited layer by layer on the substrate surface in order of increasing conductive carbon content to obtain a multilayer structure.

[0029] Based on the same inventive concept, the present invention provides an electrolyte-gradient conductive interface protection layer-lithium metal structure, wherein the electrolyte-gradient conductive interface protection layer-lithium metal structure comprises an electrolyte sheet, a lithium foil and the above-mentioned all-solid-state lithium metal battery interface protection layer;

[0030] The electrolyte sheet and the lithium foil are respectively attached to both sides of the interface protection layer;

[0031] When the interface protection layer is a multi-layer structure, the side of the multi-layer structure with a high conductive carbon content is in contact with the lithium foil.

[0032] Based on the same inventive concept, the present invention provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure, the preparation method comprising:

[0033] The solid electrolyte Li6PS5Cl and the conductive carbon are mixed and ground under an inert atmosphere to obtain a mixture A, wherein the mass ratio of the Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5;

[0034] Alternatively, the solid electrolyte Li6PS5Cl and the lithium-philic element M are mixed in a mass ratio of 75:25 under an inert atmosphere and then ground to obtain a mixture B;

[0035] The solid electrolyte Li6PS5Cl is pressed into an electrolyte sheet in a battery mold;

[0036] coating or depositing the mixture A on one or both sides of the electrolyte sheet, and laminating the sheet with lithium foil under pressure to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0037] Alternatively, a plurality of the mixtures A having different conductive carbon contents are coated or deposited layer by layer on one or both sides of the electrolyte sheet according to the conductive carbon content from low to high, and then pressed and laminated with lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0038] Alternatively, the mixture B is coated or deposited on one or both sides of the electrolyte sheet, pressed and laminated with lithium foil, and then allowed to stand at 60±1° C. for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0039] Furthermore, the particle size of the particles in the mixture A is 1 to 5 μm;

[0040] The particle size of the particles in the mixture B is 1 to 5 μm;

[0041] The thickness of the electrolyte sheet is 800 to 900 μm;

[0042] The conductive carbon comprises at least one of graphite, Super P, carbon nanotubes, carbon black and Ketjen black;

[0043] The lithium-philic element M is at least one of Cu, Zn, Mg, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn.

[0044] Furthermore, the mixture A is coated or deposited on one or both sides of the electrolyte sheet, and pressed and laminated with lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure, which specifically includes:

[0045] The mixture A is coated or deposited on one side or both sides of the electrolyte sheet, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to laminate the electrolyte sheet with lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0046] The method comprises coating or depositing a plurality of mixtures A having different conductive carbon contents on one side or both sides of the electrolyte sheet layer by layer according to the conductive carbon contents from low to high, and laminating the mixtures with lithium foil under pressure to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0047] The mixtures A with different conductive carbon contents are coated or deposited layer by layer on one or both sides of the electrolyte sheet according to the conductive carbon content from low to high, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to the lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0048] The mixture B is coated or deposited on one side or both sides of the electrolyte sheet, pressed and laminated with lithium foil, and then allowed to stand at 60±1° C. for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure, specifically comprising:

[0049] The mixture B is coated or deposited on one or both sides of the electrolyte sheet, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to laminate it with lithium foil, and then the mixture is allowed to stand at 60±1°C for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0050] Based on the same inventive concept, the present invention provides an electrolyte-gradient conductive interface protection layer structure, which includes an electrolyte sheet and the above-mentioned all-solid-state lithium metal battery interface protection layer;

[0051] The interface protection layer is attached to one side of the electrolyte sheet;

[0052] When the interface protection layer is a multi-layer structure, the side of the multi-layer structure with a low conductive carbon content is in contact with the electrolyte sheet.

[0053] Based on the same inventive concept, the present invention provides an application of an all-solid-state lithium metal battery interface protection layer in the preparation of an all-solid-state lithium metal battery.

[0054] Based on the same inventive concept, the present invention provides an application of an electrolyte-gradient conductive interface protection layer-lithium metal structure in the preparation of an all-solid-state lithium metal battery.

[0055] Based on the same inventive concept, the present invention also provides an application of an electrolyte-gradient conductive interface protection layer structure in the preparation of an all-solid-state lithium metal battery.

[0056] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0057] 1. The present invention provides an interface protection layer for an all-solid-state lithium metal battery. The interface protection layer is obtained by mixing a solid electrolyte with conductive carbon or a lithium-philic element M and uniformly dispersing them, and then coating and pressurizing them to obtain an interface protection layer with gradient conductivity. The interface protection layer of a single-layer or multi-layer structure can achieve gradient conductivity and can be used as an intermediate layer between the solid electrolyte and the lithium metal negative electrode. The lithium-philic element M can spontaneously diffuse toward the lithium metal side at high temperature to achieve the same purpose, thereby realizing the construction of an interface protection layer between the solid electrolyte and the lithium metal. There is a certain conductivity difference between the conductive carbon and the electrolyte and the lithium metal, and it is mainly used to achieve electric field homogenization. The interface protection layer can not only reduce the local current density and induce uniform lithium deposition, but also improve the adhesion of the lithium deposition layer to the negative electrode, forming a solid electrolyte interface layer with good mechanical properties and uniform flux, effectively inhibiting side reactions between the deposited lithium and the electrolyte, and thereby improving the cycle stability and safety of the all-solid-state lithium metal battery.

[0058] 2. The present invention provides an electrolyte-gradient conductive interface protection layer-lithium metal structure. By uniformly mixing and dispersing the electrolyte with conductive carbon / lithiophilic element M, an interface layer with gradient conductive properties is obtained, and an electrolyte-gradient conductive interface protection layer-lithium metal / lithium-free negative electrode structure is constructed to take into account both structural stability and high electrochemical properties. Among them, the electrolyte Li6PS5Cl has the characteristics of lithiophobicity and electrochemical inertness, and has ultra-high stability during the lithium insertion / deinsertion process. The difference in electronic conductivity of the interface layer constructed by electrolyte + conductive carbon / lithiophilic element M not only ensures electron transmission, but also can effectively induce the uniform nucleation process of metallic lithium on the interface layer, ultimately improving battery performance.

[0059] 3. The present invention provides an electrolyte-gradient conductive interface protection layer-lithium metal structure. The electrolyte Li6PS5Cl in this structure has high electrochemical performance and structural stability. While achieving rapid ion migration, it maintains a highly stable skeleton structure. The conductive interface layer with different gradients can effectively induce a uniform lithium deposition process while ensuring its internal ion and electron transmission, ultimately achieving the purpose of rapid diffusion of lithium ions to the negative electrode side and uniform deposition. In addition, the solid electrolyte and lithium metal of the present invention both have a high lithium ion diffusion coefficient and a high lithium ion transport capacity, which helps to improve the uniform diffusion of lithium ions into the interface layer in terms of kinetic characteristics, thereby achieving more uniform metal lithium deposition and ultimately improving battery performance.

[0060] 4. The present invention provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure. This method can simply and effectively inhibit the growth of lithium dendrites by constructing an interface protection layer intermediate layer with certain gradient conductive properties between the solid electrolyte and the lithium metal negative electrode side. The process of the present invention is simple and easy to industrially apply. The design of the electrolyte-gradient conductive interface protection layer-lithium metal / lithium-free negative electrode structure takes into account the structural stability and high electrochemical performance when subsequently applied to batteries, meeting commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0062] Figure 1 This is a schematic diagram of the all-solid-state battery electrolyte-gradient conductive interface protection layer-lithium metal / lithium-free negative electrode structure of the present invention.

[0063] Figure 2 These are the SEM and EDS images of the cross-section of the all-solid-state battery electrolyte-gradient conductive interface protection layer-lithium metal structure of Example 1.

[0064] Figure 3 2 is a comparison chart of the battery cycle performance of Example 1 and Comparative Example 1.

[0065] Figure 4 The figure is a comparison of the battery cycle performance of Example 2 and Comparative Example 1.

[0066] Figure 5 3 is a comparison chart of the battery cycle performance of Example 3 and Comparative Example 1.

[0067] Reference numerals: 1-electrolyte, 2-gradient conductive interface protection layer, 3-lithium metal / lithium-free negative electrode. DETAILED DESCRIPTION

[0068] The present invention will be described in detail below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific embodiments and examples are for illustrating the present invention, rather than for limiting the present invention.

[0069] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the event of any conflict, the present specification shall take precedence.

[0070] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0071] The technical principles of the present invention are as follows:

[0072] The present invention provides an interface protection layer for an all-solid-state lithium metal battery, wherein the interface protection layer is a single-layer structure or a multi-layer structure;

[0073] The single-layer structure is composed of Li6PS5Cl and conductive carbon, and the mass ratio of Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5;

[0074] Alternatively, the single-layer structure is composed of Li6PS5Cl and a lithium-philic element M, and the mass ratio of Li6PS5Cl to the lithium-philic element M is 75:25;

[0075] The multilayer structure is formed by stacking several interface layers, wherein the interface layer is composed of Li6PS5Cl and conductive carbon, and the mass ratio of Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5;

[0076] In the several interface layers, the content of the conductive carbon increases layer by layer.

[0077] In the present invention, the mass ratio of Li6PS5Cl to conductive carbon is selected from 99.5:0.5, 99:1, 97:3 and 95:5, which has the advantage of effectively changing the electronic conduction of the interface layer without affecting the ion conduction; the mass ratio of Li6PS5Cl to the lithium-philic element M is 75:25, which can effectively change the electronic conduction of the interface layer without affecting the ion conduction.

[0078] Optionally, the thickness of the interface protection layer is 5 to 200 μm.

[0079] In the present invention, the thickness of the interface protection layer is 5 to 200 μm, which has the advantage of reducing the impact on ion transmission.

[0080] In the present invention, the addition of conductive carbon and lithium-philic element M mainly plays the role of changing the conductivity of the interface layer, constructing a gradient conductive interface, thereby homogenizing the interface electric field, achieving the purpose of uniform lithium deposition and inhibiting the deposition and growth of lithium dendrites.

[0081] Optionally, the conductive carbon includes at least one of graphite, Super P, carbon nanotubes, carbon black and Ketjen black;

[0082] The lithium-philic element M is at least one of Cu, Zn, Mg, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn.

[0083] Based on the same inventive concept, the present invention provides an electrolyte-gradient conductive interface protection layer-lithium metal structure, wherein the electrolyte-gradient conductive interface protection layer-lithium metal structure comprises an electrolyte sheet, a lithium foil and the above-mentioned all-solid-state lithium metal battery interface protection layer;

[0084] The electrolyte sheet and the lithium foil are respectively attached to both sides of the interface protection layer;

[0085] When the interface protection layer is a multi-layer structure, the side of the multi-layer structure with a high conductive carbon content is in contact with the lithium foil.

[0086] In the present invention, the advantage of laminating the side with a high conductive carbon content in the multilayer structure with the lithium foil is that a gradient conductive interface is effectively formed, thereby reducing interface impedance.

[0087] Based on the same inventive concept, the present invention provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure, the preparation method comprising:

[0088] The solid electrolyte Li6PS5Cl and the conductive carbon are mixed and ground under an inert atmosphere to obtain a mixture A, wherein the mass ratio of the Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5;

[0089] Alternatively, the solid electrolyte Li6PS5Cl and the lithium-philic element M are mixed in a mass ratio of 75:25 under an inert atmosphere and then ground to obtain a mixture B;

[0090] The solid electrolyte Li6PS5Cl is pressed into an electrolyte sheet in a battery mold;

[0091] coating or depositing the mixture A on one or both sides of the electrolyte sheet, and laminating the sheet with lithium foil under pressure to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0092] Alternatively, a plurality of the mixtures A having different conductive carbon contents are coated or deposited layer by layer on one or both sides of the electrolyte sheet according to the conductive carbon content from low to high, and then pressed and laminated with lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0093] Alternatively, the mixture B is coated or deposited on one or both sides of the electrolyte sheet, pressed and laminated with lithium foil, and then allowed to stand at 60±1° C. for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0094] In the present invention, the mixture B is coated or deposited on one or both sides of the electrolyte sheet, laminated with the lithium foil after pressurization, and then left to stand at 60±1°C for 12±0.5 h. The advantage is that the lithium-philic metal M can effectively and spontaneously migrate to the lithium metal, forming a conductive gradient difference.

[0095] Furthermore, the particle size of the particles in the mixture A is 1 to 5 μm;

[0096] The particle size of the particles in the mixture B is 1 to 5 μm;

[0097] The thickness of the electrolyte sheet is 800 to 900 μm;

[0098] The conductive carbon comprises at least one of graphite, Super P, carbon nanotubes, carbon black and Ketjen black;

[0099] The lithium-philic element M is at least one of Cu, Zn, Mg, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn.

[0100] In the present invention, the particle size of the mixture A and B is 1 to 5 μm, which has the advantage of effectively increasing the density of the electrolyte and interface layer material particles and improving the ion transport of the material.

[0101] Furthermore, the mixture A is coated or deposited on one or both sides of the electrolyte sheet, and pressed and laminated with lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure, which specifically includes:

[0102] The mixture A is coated or deposited on one side or both sides of the electrolyte sheet, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to laminate the electrolyte sheet with lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0103] The method comprises coating or depositing a plurality of mixtures A having different conductive carbon contents on one side or both sides of the electrolyte sheet layer by layer according to the conductive carbon contents from low to high, and laminating the mixtures with lithium foil under pressure to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0104] The mixtures A with different conductive carbon contents are coated or deposited layer by layer on one or both sides of the electrolyte sheet according to the conductive carbon content from low to high, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to the lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure;

[0105] The mixture B is coated or deposited on one side or both sides of the electrolyte sheet, pressed and laminated with lithium foil, and then allowed to stand at 60±1° C. for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure, specifically comprising:

[0106] The mixture B is coated or deposited on one or both sides of the electrolyte sheet, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to laminate it with lithium foil, and then the mixture is allowed to stand at 60±1°C for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0107] In the present invention, applying a pressure of 5 to 10 MPa has the advantage of reducing the interfacial impedance and improving the contact between the lithium metal and the interface layer. Too low a pressure may easily lead to poor contact between the lithium metal and the interface layer.

[0108] In the present invention, the solid electrolyte Li6PS5Cl can be other solid electrolytes with relatively high lithium ion diffusion coefficient and electrochemical stability with lithium metal.

[0109] Based on the same inventive concept, the present invention provides an electrolyte-gradient conductive interface protection layer structure, which includes an electrolyte sheet and the above-mentioned all-solid-state lithium metal battery interface protection layer;

[0110] The interface protection layer is attached to one side of the electrolyte sheet;

[0111] When the interface protection layer is a multi-layer structure, the side of the multi-layer structure with a low conductive carbon content is in contact with the electrolyte sheet.

[0112] In the present invention, the electrolyte-gradient conductive interface protection layer structure is also called the electrolyte-gradient conductive interface protection layer-lithium-free negative electrode structure, which can reduce the use of lithium metal and allow lithium to be directly deposited on one side of the current collector, further inhibiting the growth of lithium dendrites.

[0113] The following will describe in detail an all-solid-state lithium metal battery interface protection layer, its preparation method, and application in combination with examples and experimental data.

[0114] Example 1

[0115] This embodiment provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure:

[0116] Step 1: The solid electrolyte Li6PS5Cl and Super P are mixed in an agate mortar / ball mill at a mass ratio of 99:1 under an Ar atmosphere, and are fully ground for 30 minutes to make them uniform. The particle size of the obtained mixture is 1 to 5 μm.

[0117] Step 2: Li6PS5Cl is pressed into a thin sheet (i.e., an electrolyte sheet with a thickness of 800 μm) in a battery mold. The mixture in step 1 is then added to one side of the sheet and pressurized (500 MPa) to obtain a 40 μm thick interface layer. Finally, lithium foil is attached to this side and pressurized to 10 MPa to improve the contact, thus obtaining an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0118] Battery assembly: Based on the above structure, the positive electrode LiNi is added to the other side of the electrolyte sheet Li6PS5Cl 0.89 Co 0.06 Mn 0.05 O2 is assembled into an all-solid-state battery; alternatively, the same electrolyte-gradient conductive interface protection layer-lithium metal structure is constructed on the other side of the electrolyte sheet, that is, a lithium metal symmetric battery is assembled.

[0119] Comparative Example 1

[0120] Li6PS5Cl is used as electrolyte and LiNi 0.89 Co 0.06 Mn 0.05 O2 is used as the positive electrode and lithium foil is used as the negative electrode to assemble full batteries and lithium symmetrical batteries.

[0121] Example 2

[0122] This embodiment provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure:

[0123] Step 1: Solid electrolyte Li6PS5Cl and Super P were mixed in an agate mortar / ball mill at a mass ratio of 99.5:0.5 and 97:3, respectively, under an Ar atmosphere, and fully ground for 30 minutes to homogenize the mixture. The particle size of the obtained mixture was 1 to 5 μm.

[0124] Step 2: Li6PS5Cl is pressed into a thin sheet with a thickness of 800 μm in a battery mold. A mixture with a mass ratio of 99.5-0.5% in step 1 is coated on one side of the thin sheet and pressurized (300 MPa) to obtain a 20 μm thick coating. Subsequently, a mixture with a mass ratio of 97-3% is coated and pressurized (500 MPa) to obtain a 20 μm thick coating, resulting in an interface layer with a total thickness of 40 μm. Finally, lithium foil is attached and pressurized at 10 MPa to improve contact, thereby obtaining an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0125] Battery assembly: Based on the above structure, the positive electrode LiNi is added to the other side of the electrolyte sheet Li6PS5Cl 0.89 Co 0.06 Mn 0.05O2 is assembled into an all-solid-state lithium metal battery, or the same electrolyte-gradient conductive interface protection layer-lithium metal structure is constructed on the other side of the electrolyte sheet, that is, assembled into a lithium metal symmetric battery.

[0126] Example 3

[0127] This embodiment provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure:

[0128] Step 1: Solid electrolyte Li6PS5Cl and Mg are mixed in an agate mortar / ball mill at a mass ratio of 75:25 under an Ar atmosphere, and fully ground for 30 minutes to make them uniform. The particle size of the obtained mixture is 1 to 5 μm.

[0129] Step 2: Li6PS5Cl is pressed into a thin sheet with a thickness of 800 μm in a battery mold. The mixture in step 1 is then added to one side of the sheet and pressurized (500 MPa). Finally, lithium foil is attached to this side and pressurized at 10 MPa at 60 °C for 12 hours to obtain a 30 μm thick interface layer, that is, an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0130] Battery assembly: Based on the above structure, the positive electrode LiNi is added to the other side of the electrolyte sheet Li6PS5Cl 0.89 Co 0.06 Mn 0.05 O2 is assembled into an all-solid-state lithium metal battery, or the same electrolyte-gradient conductive interface protection layer-lithium metal structure is constructed on the other side of the electrolyte sheet Li6PS5Cl, that is, a lithium metal symmetric battery is assembled.

[0131] Example 4

[0132] This embodiment provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure:

[0133] Step 1: Solid electrolyte Li6PS5Cl and Super P were mixed in an agate mortar / ball mill at a mass ratio of 99.5:0.5 and 97:3, respectively, under an Ar atmosphere, and fully ground for 30 minutes to homogenize the mixture. The particle size of the obtained mixture was 1 to 5 μm.

[0134] Step 2: Li6PS5Cl is pressed into a thin sheet with a thickness of 800 μm in a battery mold. Subsequently, the mixtures with a mass ratio of 99.5:0.5 and 97:3 in step 1 are added to the atomic layer deposition equipment and deposited on one side of the thin sheet, respectively, with a thickness of 20 μm, to obtain an interface layer with a total thickness of 40 μm. Finally, lithium foil is attached to this side and pressurized to 10 MPa to improve the contact, thereby obtaining an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0135] Battery assembly: Based on the above structure, the positive electrode LiNi is added to the other side of the electrolyte sheet Li6PS5Cl 0.89 Co 0.06 Mn 0.05 O2 is assembled into an all-solid-state lithium metal battery, or the same electrolyte-gradient conductive interface protection layer-lithium metal structure is constructed on the other side of the electrolyte sheet Li6PS5Cl, that is, a lithium metal symmetric battery is assembled.

[0136] Example 5

[0137] This embodiment provides a method for preparing an electrolyte-gradient conductive interface protection layer-lithium metal structure:

[0138] Step 1: Solid electrolyte Li6PS5Cl and Mg are mixed in an agate mortar / ball mill at a mass ratio of 75:25 under an Ar atmosphere, and fully ground for 30 minutes to make them uniform. The particle size of the obtained mixture is 1 to 5 μm.

[0139] Step 2: Li6PS5Cl is pressed into a thin sheet with a thickness of 800 μm in a battery mold. The mixture in step 1 is then added to one side of the thin sheet in an atomic layer deposition device and deposited. Finally, lithium foil is attached to this side and pressurized at 10 MPa at 60°C and allowed to stand for 12 hours to obtain a 30 μm interface layer, thus obtaining an electrolyte-gradient conductive interface protection layer-lithium metal structure.

[0140] Battery assembly: Based on the above structure, a positive electrode LiNi is added to the other side of the electrolyte Li6PS5Cl 0.89 Co 0.06 Mn 0.05 O2 is assembled into an all-solid-state lithium metal battery, or the same electrolyte-gradient conductive interface protection layer-lithium metal structure is constructed on the other side of the electrolyte sheet Li6PS5Cl, that is, a lithium metal symmetric battery is assembled.

[0141] Figure 1 This is a schematic diagram of the all-solid-state lithium metal battery electrolyte-gradient conductive interface protection layer-lithium metal / lithium-free negative electrode structure of the present invention. An interface layer with certain conductive properties is added between the electrolyte and the lithium metal negative electrode. Due to the lithium-repellent and electrochemically inert characteristics of the electrolyte itself, it has ultra-high stability during the deintercalation and extraction of metallic lithium and can maintain the integrity of the skeleton. Due to the difference in electronic conductivity of the interface layer, it not only ensures electron transmission, but also can effectively induce the uniform nucleation process of metallic lithium on the interface layer.

[0142] Figure 2The SEM and EDS images of the cross-section of the all-solid-state lithium metal battery electrolyte-gradient conductive interface protection layer-lithium metal structure in Example 1 show that a uniformly distributed interface layer was successfully prepared, which helps to homogenize the electrolyte electric field and achieve the purpose of inhibiting the nucleation and growth of lithium dendrites. Figure 2 It can be seen that the C element is evenly distributed in the interface layer between the electrolyte and lithium metal, which indicates that the distribution of Super P in the interface layer is highly uniform. The successful preparation of a uniform and stable interface layer is conducive to the uniformity of the electric field and potential distribution in the interface layer, thereby inducing the uniform deposition of metallic lithium in the interface layer and achieving the goal of inhibiting the growth of dendrites inside the electrolyte.

[0143] Figure 3 The figure shows a comparison of the battery cycle performance of Example 1 and Comparative Example 1. After 200 h of cycling, the polarization voltage of the lithium symmetric battery of Example 1 is significantly lower than that of Comparative Example 1. The full battery assembled in Example 1 can achieve a discharge capacity of 111.5 mAh / g at 1 C, which is higher than that of Comparative Example 1, showing higher discharge capacity and cycling stability. It can be seen that compared with the comparative example, the electrolyte-gradient conductive interface protection layer-lithium metal structure constructed by the conductive interface protection layer in this embodiment has a certain promoting effect on the stabilization and improvement of the performance of the all-solid-state lithium metal battery.

[0144] Figure 4 This figure compares the cycling performance of the batteries of Example 2 and Comparative Example 1. After 200 h of cycling, the lithium symmetric battery of Example 1 maintains a stable and low polarization voltage. The assembled full battery still achieves a discharge capacity of 120 mAh / g at 1 C, demonstrating high cycling stability. This further illustrates the role of the gradient conductive interface protective layer in homogenizing the electric field and improving the battery's cycling stability.

[0145] Figure 5 The figure compares the battery cycling performance of Example 3 and Comparative Example 1. After 200 h of cycling, the polarization voltage of the lithium symmetric battery in Example 1 further decreases, and the initial discharge capacity of the assembled full battery at 1 C can reach 143 mAh / g. This demonstrates that Example 3 has a good optimization effect on the gradient conductive interface protective layer, playing a positive role in homogenizing the electric field and improving the battery's cycling stability.

[0146] It can be seen from the above embodiments that the present invention obtains an interface layer with gradient conductive properties by uniformly dispersing the electrolyte and the conductive carbon / lithium-philic metal, and constructs an electrolyte-gradient conductive interface protection layer-lithium metal / lithium-free negative electrode structure to take into account both structural stability and high electrochemical properties. Among them, the electrolyte has the characteristics of lithium repellency and electrochemical inertness, and has ultra-high stability in the process of lithium insertion / deinsertion; the difference in electronic conductivity of the interface layer of the conductive carbon / lithium-philic metal structure not only ensures electron transmission, but also can effectively induce the uniform nucleation process of metallic lithium on the interface layer, ultimately improving the battery performance. The process of the present invention is simple and easy to apply industrially, and the design of the electrolyte-gradient conductive interface protection layer-lithium metal / lithium-free negative electrode structure takes into account the structural stability and high electrochemical performance when subsequently applied to the battery.

[0147] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0148] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0149] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. An all-solid-state lithium metal battery interface protection layer, characterized in that: The interface protection layer is a single-layer structure, and the single-layer structure is a single-layer structure A or a single-layer structure B; The single-layer structure A is composed of Li6PS5Cl and conductive carbon, and the mass ratio of Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5; The single-layer structure B is composed of Li6PS5Cl and a lithium-philic element M, and the mass ratio of Li6PS5Cl to the lithium-philic element M is 75:25; The lithium-philic element M is at least one of Cu, Zn, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn; The single-layer structure A is prepared by the following method: Solid electrolyte Li6PS5Cl and conductive carbon are mixed and ground under an inert atmosphere to obtain a mixture A, the mixture A is coated or deposited on one or both sides of the solid electrolyte, and then pressed and laminated with lithium foil, and the obtained interface protective layer is the single-layer structure A; The single-layer structure B is prepared by the following method: The solid electrolyte Li6PS5Cl and the lithium-philic element M are mixed and ground under an inert atmosphere to obtain a mixture B. The mixture B is coated or deposited on one or both sides of the solid electrolyte, pressed and laminated with lithium foil, and then allowed to stand at 60±1°C for 12±0.5h. The resulting interface protective layer is the single-layer structure B.

2. The all-solid-state lithium metal battery interface protection layer according to claim 1, characterized in that: The thickness of the interface protection layer is 5 to 200 μm.

3. The all-solid-state lithium metal battery interface protection layer according to claim 1, characterized in that: The conductive carbon includes at least one of graphite, SuperP, carbon nanotubes, carbon black and Ketjen black.

4. A method for preparing an interface protective layer for an all-solid-state lithium metal battery according to any one of claims 1 to 3, characterized in that: The preparation method comprises: The solid electrolyte Li6PS5Cl and the conductive carbon are mixed and ground under an inert atmosphere to obtain a mixture A, wherein the mass ratio of the Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5; The mixture A is coated or deposited on one side or both sides of the solid electrolyte, and pressed and laminated with the lithium foil, so that the obtained interface protection layer is a single-layer structure A; Alternatively, the solid electrolyte Li6PS5Cl and the lithium-philic element M are mixed in a mass ratio of 75:25 under an inert atmosphere and then ground to obtain a mixture B; The mixture B is coated or deposited on one side or both sides of the solid electrolyte, pressed and laminated with lithium foil, and then allowed to stand at 60±1° C. for 12±0.5 h. The resulting interface protection layer is a single-layer structure B.

5. The method for preparing an interface protective layer for an all-solid-state lithium metal battery according to claim 4, characterized in that: The particle size of the particles in the mixture A is 1 to 5 μm; The particle size of the particles in the mixture B is 1 to 5 μm; The conductive carbon comprises at least one of graphite, SuperP, carbon nanotubes, carbon black and Ketjen black; The lithium-philic element M is at least one of Cu, Zn, Mg, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn.

6. An electrolyte-gradient conductive interface protection layer-lithium metal structure, characterized in that: The electrolyte-gradient conductive interface protection layer-lithium metal structure comprises an electrolyte sheet, a lithium foil and an all-solid-state lithium metal battery interface protection layer according to any one of claims 1 to 3; The electrolyte sheet and the lithium foil are respectively attached to both sides of the interface protection layer; The electrolyte-gradient conductive interface protection layer-lithium metal structure is prepared by the following method: The solid electrolyte Li6PS5Cl and the conductive carbon are mixed and ground under an inert atmosphere to obtain a mixture A, wherein the mass ratio of the Li6PS5Cl to the conductive carbon is any one of 99.5:0.5, 99:1, 97:3 and 95:5; Alternatively, the solid electrolyte Li6PS5Cl and the lithium-philic element M are mixed in a mass ratio of 75:25 under an inert atmosphere and then ground to obtain a mixture B; The solid electrolyte Li6PS5Cl is pressed into an electrolyte sheet in a battery mold; coating or depositing the mixture A on one or both sides of the electrolyte sheet, and laminating the sheet with lithium foil under pressure to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure; Alternatively, the mixture B is coated or deposited on one or both sides of the electrolyte sheet, pressed and laminated with lithium foil, and then allowed to stand at 60±1° C. for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

7. The electrolyte-gradient conductive interface protection layer-lithium metal structure according to claim 6, characterized in that: The particle size of the particles in the mixture A is 1 to 5 μm; The particle size of the particles in the mixture B is 1 to 5 μm; The thickness of the electrolyte sheet is 800 to 900 μm; The conductive carbon comprises at least one of graphite, SuperP, carbon nanotubes, carbon black and Ketjen black; The lithium-philic element M is at least one of Cu, Zn, Mg, Al, Sb, Ca, Ba, Ag, In, Bi, Ge, B and Sn.

8. The electrolyte-gradient conductive interface protection layer-lithium metal structure according to claim 6, characterized in that: The step of coating or depositing the mixture A on one side or both sides of the electrolyte sheet and laminating the electrolyte sheet with lithium foil under pressure to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure specifically includes: The mixture A is coated or deposited on one side or both sides of the electrolyte sheet, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to laminate the electrolyte sheet with lithium foil to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure; The mixture B is coated or deposited on one side or both sides of the electrolyte sheet, pressed and laminated with lithium foil, and then allowed to stand at 60±1° C. for 12±0.5 h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure, specifically comprising: The mixture B is coated or deposited on one or both sides of the electrolyte sheet, and then a pressure of 300-500 MPa is applied, and then a pressure of 5-10 MPa is applied to fit the lithium foil, and then the mixture is allowed to stand at 60±1°C for 12±0.5h to obtain an electrolyte-gradient conductive interface protection layer-lithium metal structure.

9. An electrolyte-gradient conductive interface protection layer structure, characterized in that: The electrolyte-gradient conductive interface protection layer structure comprises an electrolyte sheet and an all-solid-state lithium metal battery interface protection layer according to any one of claims 1 to 3; The interface protection layer is attached to one side of the electrolyte sheet.

10. Use of an all-solid-state lithium metal battery interface protection layer according to any one of claims 1 to 3 in the preparation of an all-solid-state lithium metal battery.

11. Use of the electrolyte-gradient conductive interface protection layer-lithium metal structure according to claim 6 in the preparation of an all-solid-state lithium metal battery.

12. Use of the electrolyte-gradient conductive interface protection layer structure according to claim 9 in the preparation of an all-solid-state lithium metal battery.

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