Coating material, method for manufacturing laminated electrolyte, and solid-state battery

Abstract

The application discloses a coating material, a preparation method of a laminated electrolyte and a solid-state battery. The coating material comprises 0.1-30 wt.% of a conductive agent, 0.1-30 wt.% of a binder, 0.01-30 wt.% of a coupling agent and the rest is solvent. The preparation method of the laminated electrolyte comprises the following steps: step one, preparing an organic electrolyte film, an inorganic electrolyte film, a conductive agent, a binder and a coupling agent; step two, stirring the binder, the conductive agent and the coupling agent in the solvent to obtain a mixed glue solution; step three, uniformly coating the mixed glue solution on the upper and lower sides of the inorganic electrolyte film; and step four, stacking the organic electrolyte film, the inorganic electrolyte film coated with the mixed glue solution and the organic electrolyte film and pressing to obtain the laminated electrolyte. The solid-state battery comprises a positive electrode layer, the laminated electrolyte layer and a negative electrode layer which are stacked in sequence. The application can effectively solve the problems of poor adhesion of the inorganic electrolyte film and the organic electrolyte film, interface gap caused by deformation and poor adhesion of the organic matter and the inorganic matter.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, specifically to a coating material, a method for preparing a layered electrolyte, and a solid-state battery. Background Technology

[0002] Compared to liquid lithium-ion batteries, solid-state batteries offer higher energy density, a wider electrochemical window, greater volume flexibility, and better high-temperature battery safety, making them a potential future direction for battery technology development. However, current solid-state batteries still suffer from a series of problems, including poor electrode / solid electrolyte membrane interface stability, high interfacial impedance, and non-uniform lithium-ion deposition leading to dendrite growth and poor electrochemical performance during long-cycle operation. Therefore, the selection of solid electrolytes in solid-state batteries must consider preventing Li dendrite growth, reducing side reactions, and improving the interface.

[0003] Solid-state electrolytes fall into two main categories: inorganic electrolytes and solid polymer electrolytes. Inorganic electrolytes have high elastic modulus and high room-temperature ionic conductivity. Polymer electrolytes, on the other hand, have low room-temperature ionic conductivity, and solid polymer electrolytes also have relatively low elastic modulus and poor mechanical properties, thus failing to completely prevent lithium dendrite growth; however, they are ductile and flexible, ensuring good contact between the electrolyte and the positive and negative electrodes. Therefore, a composite electrolyte approach is considered to combine the advantages of both inorganic and solid polymer electrolytes. However, in actual fabrication, interface problems inherent in solid-state batteries must be addressed: poor solid-solid contact between the positive and negative electrode materials and the inorganic electrolyte, and the difference in conductivity and contact issues between the polymer and inorganic electrolytes. Especially during charge-discharge cycles, the evolution of the interfacial phase leads to changes in stress / strain, causing crack formation and propagation, interfacial delamination, and a reduction in the overall physical connectivity between particles and components, thus deteriorating interfacial characteristics and battery performance. These interface problems have become a bottleneck restricting the development of solid-state batteries; therefore, optimizing the interface is of great significance for the market application of all-solid-state batteries.

[0004] In organic-inorganic layered composite electrolytes, organic and inorganic materials are stacked in layers, and the interaction between these layers can effectively improve the interface problems of all-solid-state batteries. However, layered composite electrolytes increase the number of interfaces, and the interfacial impedance between different phases cannot be ignored. Furthermore, the flexible electrode / electrolyte interface is mainly characterized by weak physical interactions, and volume changes during cycling can easily damage the interfacial structure. The key to solving these problems with layered composite electrolytes is to explore a substance that can chemically interact with both organic and inorganic materials simultaneously, without increasing the interfacial resistance, and in conjunction with flexible physical interactions to achieve the joint regulation of multiple interfaces, including electrode / electrolyte and organic / inorganic electrolyte interfaces.

[0005] Chinese patent application number 202210540232.0, entitled "Integrated All-Solid-State Battery Based on Ceramic-Based Electrolyte Sheet and its Preparation Method," discloses a technical solution comprising: a positive electrode current collector layer, a composite positive electrode layer, a ceramic-based electrolyte sheet, a composite negative electrode layer, and a negative electrode current collector layer; the composite positive electrode layer is composed of a positive electrode active material, a conductive agent, and a plastic colloidal polymer; the ceramic-based electrolyte sheet is composed of an oxide electrolyte and a plastic colloidal polymer; and the composite negative electrode layer is composed of a negative electrode active material, a conductive agent, and a plastic colloidal polymer; the integrated all-solid-state battery cell is formed by hot pressing at a temperature below 300°C. While this solution can achieve seamless interconnection between different layers, it does not fully consider the potential for volume changes in materials during cycling that could damage the interface structure, resulting in gaps at the junctions of the inorganic electrolyte and the plastic colloidal polymer, and at the positive and negative electrodes, affecting contact. Furthermore, this process requires heating and hot pressing, increasing the number of steps and the cost.

[0006] Chinese patent application number 202210169455.0, entitled "A Composite Solid Electrolyte Membrane and Its Preparation Method," discloses a technical solution: the composite solid electrolyte membrane is prepared by uniformly dispersing a polymer in an organic solvent, then adding and uniformly dispersing an inorganic oxide, and finally adding a lithium salt and stirring until uniformly mixed to obtain a composite electrolyte slurry. This composite electrolyte slurry is then coated onto a porous support material with high porosity and dried to obtain a high-mechanical-strength, ultra-thin composite solid electrolyte membrane. While this method can prepare an electrolyte that combines inorganic and polymer components, it does not fully consider whether the mixed electrolyte can simultaneously leverage the advantages of both inorganic and polymer electrolytes to compensate for their respective shortcomings. The introduction of a porous support material also adds extra processes, steps, and costs.

[0007] In summary, existing methods for improving solid-state battery interfaces have the following problems:

[0008] 1. Polymer electrolytes alone cannot effectively solve the problems of low conductivity and low elastic modulus, while inorganic electrolytes alone cannot effectively solve the problems of poor adhesion and gaps caused by deformation at the interface.

[0009] 2. Simply mixing inorganic materials with polymer electrolytes cannot significantly highlight the advantages of either solid electrolyte or compensate for their defects, and the adhesion between the organic and inorganic materials in the electrolyte layer is also unstable.

[0010] 3. Currently, the lamination method cannot solve the problems of adhesion, conductivity, and interfacial resistance between the inorganic electrolyte layer and the polymer electrolyte layer. Summary of the Invention

[0011] The purpose of this invention is to provide a coating material, a method for preparing a layered electrolyte, and a solid-state battery, which can effectively solve the problems of poor adhesion between inorganic and organic electrolyte membranes, gaps at the interface caused by deformation, and poor adhesion between organic and inorganic materials.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A coating material comprising, by weight percentage, 0.1 to 30 wt.% of a conductive agent, 0.1 to 30 wt.% of a binder, 0.01 to 30 wt.% of a coupling agent, with the balance being a solvent.

[0014] Furthermore, the conductive agent is at least one of graphene, SP, and CNTs.

[0015] Furthermore, the adhesive is at least one of CMC, PVDF, PEFE, and PVA.

[0016] Furthermore, the coupling agent is at least one of KH-550, A151, A171, and A172.

[0017] Furthermore, the solvent is at least one selected from acetonitrile, NMP, toluene, and anisole.

[0018] A method for preparing a stacked electrolyte includes the following steps:

[0019] Step 1: Prepare organic electrolyte membrane and inorganic electrolyte membrane, and weigh the conductive agent, binder and coupling agent according to the composition ratio of the coating material described in this invention;

[0020] Step 2: In an environment with a water and oxygen content ≤0.1ppm, add the adhesive to the solvent and stir evenly for 0.1-2 hours; then add the conductive agent to the solvent and stir evenly for 0.1-2 hours; finally add the coupling agent to the solvent and stir evenly for 0.1-2 hours to obtain a mixed adhesive solution.

[0021] Step 3: Evenly coat the upper and lower sides of the inorganic electrolyte membrane with the mixed adhesive solution;

[0022] Step four: Stack the organic electrolyte membrane, the inorganic electrolyte membrane coated with the mixed adhesive solution, and the organic electrolyte membrane together and pressurize them to obtain a stacked electrolyte.

[0023] Furthermore, the organic electrolyte membrane is made of a mixture of PEO and lithium salt, with a weight ratio of PEO to lithium salt of 12:1.

[0024] Furthermore, the inorganic electrolyte membrane is made of at least one of LLZTO, LATP, or LLZAO.

[0025] A solid-state battery includes a positive electrode layer, an electrolyte layer, and a negative electrode layer stacked sequentially, wherein the electrolyte layer is a stacked electrolyte prepared by the method for preparing the stacked electrolyte described in this invention.

[0026] Furthermore, the positive electrode layer comprises, by weight percentage, 60-99 wt.% of positive electrode active material, 0.5-20 wt.% of conductive agent and 0.5-20 wt.% of binder, wherein the conductive agent is at least one of graphene, graphite, SP, and CNTs, and the binder is at least one of PVDF, PTFE, and PVA;

[0027] The negative electrode layer is a lithium sheet.

[0028] In this context, SP stands for conductive carbon black, CNTs for carbon nanotubes, CMC for carboxymethyl cellulose, PVDF for polyvinylidene fluoride, PTFE for polytetrafluoroethylene, PVA for polyvinyl alcohol, NMP for N-methylpyrrolidone, and PEO for polyethylene oxide.

[0029] The beneficial effects of this invention are as follows: This invention effectively bonds an inorganic electrolyte membrane and an organic electrolyte membrane (i.e., a polymer electrolyte membrane) together using a specific coating material, effectively solving problems such as poor adhesion, gaps at the interface due to deformation, and poor bonding between organic and inorganic materials. It also improves the conductivity and interfacial resistance issues between different types of electrolytes. After solving these problems, the stacked solid electrolyte simultaneously achieves better contact between the polymer electrolyte membrane and the positive and negative electrodes, while maintaining the high elastic modulus and high conductivity of the inorganic electrolyte membrane, effectively preventing lithium dendrite growth. This results in a solid composite electrolyte that combines the advantages of both inorganic and polymer electrolytes. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the solid-state battery described in this invention.

[0031] In the figure, 1—positive electrode layer, 2—electrolyte layer, 21—organic electrolyte membrane, 22—inorganic electrolyte membrane, 23—mixed solution, and 3—negative electrode layer. Detailed Implementation

[0032] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0033] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0034] A coating material comprising, by weight percentage, 0.1 to 30 wt.% of a conductive agent, 0.1 to 30 wt.% of a binder, 0.01 to 30 wt.% of a coupling agent, with the balance being a solvent.

[0035] The conductive agent is at least one of graphene, SP, and CNTs. The binder is at least one of CMC, PVDF, PEFE, and PVA. The coupling agent is at least one of KH-550, A151, A171, and A172. The solvent is at least one of acetonitrile, NMP, toluene, and anisole.

[0036] A method for preparing a stacked electrolyte includes the following steps:

[0037] Step 1: Prepare organic electrolyte membrane and inorganic electrolyte membrane, and weigh the conductive agent, binder and coupling agent according to the composition ratio of the coating material described in this invention;

[0038] Step 2: In an environment with a water and oxygen content ≤0.1ppm, add the adhesive to the solvent and stir evenly for 0.1-2 hours; then add the conductive agent to the solvent and stir evenly for 0.1-2 hours; finally add the coupling agent to the solvent and stir evenly for 0.1-2 hours to obtain a mixed adhesive solution.

[0039] Step 3: Evenly coat the upper and lower sides of the inorganic electrolyte membrane with the mixed adhesive solution;

[0040] Step four: Stack the organic electrolyte membrane, the inorganic electrolyte membrane coated with the mixed adhesive solution, and the organic electrolyte membrane together and pressurize them to obtain a stacked electrolyte.

[0041] The organic electrolyte membrane is a mixture of PEO and lithium salt, with a weight ratio of PEO to lithium salt of 12:1. The preparation of the organic electrolyte membrane involves dissolving PEO and lithium salt in acetonitrile and hot-stirring for 1–2 hours. In a glove box (ensuring an oxygen- and moisture-free environment with water and oxygen content ≤0.1 ppm), the resulting solution is cast through a mold and the solvent is evaporated to obtain the PEO organic electrolyte membrane.

[0042] The inorganic electrolyte membrane is made of at least one of LLZTO, LATP, or LLZAO, and is pressed into an inorganic electrolyte membrane with a certain thickness and diameter.

[0043] See Figure 1 The solid-state battery shown includes a positive electrode layer 1, an electrolyte layer 2, and a negative electrode layer 3 stacked sequentially. The electrolyte layer 2 is a stacked electrolyte layer prepared by the method of the present invention, namely, it includes an organic electrolyte membrane 21, an inorganic electrolyte membrane 22 coated with a mixed adhesive solution 23, and an organic electrolyte membrane 21 stacked sequentially. The positive electrode layer 1 includes, by weight percentage, 60-99 wt.% of positive electrode active material, 0.5-20 wt.% of conductive agent, and 0.5-20 wt.% of binder. The positive electrode material is NGA, the conductive agent is at least one of graphene, graphite, SP, and CNTs, and the binder is at least one of PVDF, PTFE, and PVA. The negative electrode layer is a lithium sheet.

[0044] Example 1: A solid-state battery includes a positive electrode layer, an electrolyte layer, and a negative electrode layer stacked sequentially. The positive electrode layer comprises, by weight percentage, 82 wt.% NGA (positive electrode active material), 13 wt.% SP (conductive agent), and 5 wt.% PVDF (binder). The electrolyte layer comprises, in sequence, an organic electrolyte membrane, an inorganic electrolyte membrane coated with a mixed adhesive solution, and another organic electrolyte membrane. The preparation of the electrolyte layer specifically includes the following steps:

[0045] Step 1: Prepare organic and inorganic electrolyte membranes. Weigh the conductive agent, binder, and coupling agent according to the component ratio of the coating material described in this invention. The organic electrolyte membrane is a mixture of PEO and lithium salt, with a weight ratio of PEO to lithium salt of 12:1. The organic electrolyte membrane is prepared by dissolving PEO and lithium salt in acetonitrile and hot-stirring for 1-2 hours. In a glove box (ensuring an oxygen-free and moisture-free environment with water and oxygen content ≤0.1ppm), the resulting solution is cast through a mold and the solvent evaporated to obtain the PEO organic electrolyte membrane. The conductive agent is graphene, the binder is PVDF, the coupling agent is A151, and the solvent is acetonitrile.

[0046] Step two: In a glove box (ensuring an oxygen- and moisture-free environment with water and oxygen content ≤0.1ppm), add 1.5g of PVDF to 100mL of acetonitrile and stir evenly for 0.5h. Then add 1.5g of graphene and stir evenly for 1.5h. Finally, add 10μL of A151 coupling agent and stir evenly for 1h to obtain a mixed adhesive solution.

[0047] Step 3: Apply the mixed adhesive solution evenly to the upper and lower sides of the inorganic electrolyte membrane.

[0048] Step four: Stack the organic electrolyte membrane, the inorganic electrolyte membrane coated with the mixed adhesive solution, and the organic electrolyte membrane together and pressurize them to obtain a stacked electrolyte.

[0049] Example 2, a solid-state battery, differs from Example 1 in the preparation of the mixed solution: In a glove box (ensuring an oxygen- and moisture-free environment with water and oxygen content ≤0.1ppm), 2g of PVDF was added to 100mL of acetonitrile and stirred uniformly for 0.5h. Then, 2g of graphene was added and stirred uniformly for 1.5h. Finally, 10μL of KH-550 coupling agent was added and stirred uniformly for 1h to obtain the mixed solution. The rest is the same as in Example 1.

[0050] Example 3: A solid-state battery, differing from Example 1 in the preparation of the mixed solution: In a glove box (ensuring an oxygen- and moisture-free environment with water and oxygen content ≤0.1ppm), 1.5g of PVDF was added to 100mL of acetonitrile and stirred uniformly for 1 hour. Then, 2g of graphene was added and stirred uniformly for 2 hours. Finally, 20μL of A151 coupling agent was added and stirred uniformly for 1.5 hours to obtain the mixed solution. The rest is the same as in Example 1.

[0051] According to Example 1, a solid-state battery includes a positive electrode layer, an electrolyte layer, and a negative electrode layer stacked sequentially. The positive electrode layer comprises, by weight percentage, 82 wt.% NGA (positive electrode active material), 13 wt.% SP (conductive agent), and 5 wt.% PVDF (binder). The electrolyte layer is an organic electrolyte membrane, which is a mixture of PEO and lithium salt in a weight ratio of 12:1. The organic electrolyte membrane is prepared by dissolving PEO and lithium salt in acetonitrile and hot-stirring for 1–2 hours. In a glove box (ensuring an oxygen- and moisture-free environment with water and oxygen content ≤0.1 ppm), the resulting solution is cast through a mold and the solvent is evaporated to obtain the PEO organic electrolyte membrane.

[0052] Comparative Example 2, a solid-state battery includes a positive electrode layer, an electrolyte layer, and a negative electrode layer stacked sequentially. The positive electrode layer comprises, by weight percentage, 82 wt.% NGA (positive electrode active material), 13 wt.% SP (conductive agent), and 5 wt.% PVDF (binder). The electrolyte layer comprises, in sequence, an organic electrolyte membrane, an inorganic electrolyte membrane, and another organic electrolyte membrane. The organic electrolyte membrane is a mixture of PEO and lithium salt, with a PEO to lithium salt weight ratio of 12:1. The organic electrolyte membrane is prepared by dissolving PEO and lithium salt in acetonitrile and hot-stirring for 1-2 hours. In a glove box (ensuring an oxygen-free and moisture-free environment with water and oxygen content ≤0.1 ppm), the resulting solution is cast through a mold and the solvent evaporated to obtain the PEO organic electrolyte membrane. The inorganic electrolyte membrane is made of at least one of LLZTO, LATP, or LLZAO, and is pressed into an inorganic electrolyte membrane of a specific thickness and diameter.

[0053] The solid-state batteries of Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 were subjected to performance tests, and the results are shown in Table 1.

[0054] Table 1. Performance test results of Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2.

[0055] Group Number of cycles Capacity retention rate / % <![CDATA[Electrolyte membrane conductivity / S×cm -1 > Example 1 80 86.8 <![CDATA[5.54×10 -4 ]]> Example 2 80 88,1 <![CDATA[5.89×10 -4 ]]> Example 3 80 86.4 <![CDATA[5.52×10 -4 ]]> Compare with Example 1 80 66.2 <![CDATA[3.86×10 -4 ]]> Compare with Example 2 80 56.7 <![CDATA[1.24×10 -4 ]]>

[0056] By comparing the results of the examples and control examples in Table 1, two points can be observed: First, the organic and inorganic electrolyte membranes are laminated together, which improves the conductivity; second, the coating method significantly improves the conductivity of the laminated composite electrolyte and significantly enhances the cycle life of the prepared solid-state battery. In summary, by coating the inorganic electrolyte membrane in the laminated composite electrolyte membrane with a special adhesive, the interfacial performance of the laminated composite electrolyte in solid-state batteries can be improved, thereby enhancing the electrical performance of the solid-state battery.

[0057] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for producing a laminated electrolyte, characterized by, The method comprises the following steps: Step one, prepare an organic electrolyte film and an inorganic electrolyte film, and weigh a conductive agent, a binder and a coupling agent according to the component proportion of a coating material; the coating material comprises 0.1-30wt.% of the conductive agent, 0.1-30wt.% of the binder and 0.01-30wt.% of the coupling agent, and the rest is a solvent; Step two, in an environment with a water oxygen content of ≤0.1ppm, add the binder into the solvent and uniformly stir for 0.1-2h; then add the conductive agent into the solvent and uniformly stir for 0.1-2h; finally add the coupling agent into the solvent and uniformly stir for 0.1-2h to obtain a mixed glue solution; Step three, uniformly coat the mixed glue solution on the upper and lower sides of the inorganic electrolyte film; Step four, stack the organic electrolyte film, the inorganic electrolyte film coated with the mixed glue solution and the organic electrolyte film, and pressurize to obtain a laminated electrolyte.

2. The method for producing a laminated electrolyte according to claim 1, characterized by: The conductive agent is at least one of graphene, SP and CNTs.

3. The method for producing a laminated electrolyte according to claim 1 or 2, characterized by: The binder is at least one of CMC, PVDF, PEFE and PVA.

4. The method for producing a laminated electrolyte according to claim 1 or 2, characterized by: The coupling agent is at least one of KH-550, A151, A171 and A172.

5. The method for producing a laminated electrolyte according to claim 1 or 2, characterized by: The solvent is at least one of acetonitrile, NMP, toluene and anisole.

6. The method of claim 1, wherein: The material of the organic electrolyte film is a mixture of PEO and lithium salt, and the weight ratio of the PEO to the lithium salt is 12:

1.

7. The method of claim 1, wherein: The material of the inorganic electrolyte film is at least one of LLZTO, LATP and LLZAO.

8. A solid state battery, characterized by: The battery comprises a positive electrode layer, an electrolyte layer and a negative electrode layer stacked in sequence, and the electrolyte layer is the laminated electrolyte layer prepared by the method for preparing a laminated electrolyte according to any one of claims 1-7.

9. The solid-state battery of claim 8, wherein: The positive electrode layer comprises 60-99wt.% of a positive electrode active material, 0.5-20wt.% of a conductive agent and 0.5-20wt.% of a binder, the conductive agent is at least one of graphene, graphite, SP and CNTs, and the binder is at least one of PVDF, PTFE and PVA; The negative electrode layer is a lithium sheet.

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