Lithium Salt-Free Composite Solid Electrolyte Membrane and Method for Producing the Same

Abstract

The present application provides a lithium salt-free composite solid electrolyte membrane and a method for manufacturing the same. The components of the lithium salt-free composite solid electrolyte membrane are a micro-nano-order garnet solid electrolyte and a polymer. Here, the weight ratio of the micro-nano-order garnet-type solid electrolyte to the polymer is (60 to 100):(5 to 40), and the particle size of the micro-nano-order garnet-type solid electrolyte is 100 nm to 2 μm. The present application further provides a method for manufacturing the lithium salt-free composite solid electrolyte membrane. Based on the present application, the form and thickness of the manufactured lithium salt-free composite solid electrolyte membrane can be controlled, there is no need to add a lithium salt, there is no need to create an anhydrous and inert atmosphere, the production cost is significantly reduced, which is advantageous for mass production.

Description

Technical Field

[0001] This application belongs to the field of energy storage technologies. Specifically, this application relates to a lithium-salt-free composite solid electrolyte membrane and a method for manufacturing the same. Cross-reference to Related Applications This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on June 14, 2022, with an application number of 202210669774.8 and an invention title of "Lithium-Salt-Free Composite Solid Electrolyte Membrane and Method for Manufacturing the Same", and all of its content is incorporated into this application by reference.

Background Art

[0002] Lithium-ion batteries are widely applied in energy storage systems, new energy vehicles, and consumer electronic products, and the requirements for their safety are also increasing with the expansion of application scenarios. In conventional liquid electrolytes, the battery may short-circuit due to mechanical abuse or electrical abuse, release heat, cause thermal abuse, and ultimately the flammable electrolyte may burn and even explode. By using solid electrolytes, such situations can be avoided, and the safety of the battery can be significantly improved.

[0003] Solid electrolytes can be classified into polymer electrolytes, inorganic electrolytes, and organic-inorganic composite electrolytes according to their composition. Inorganic electrolytes have high ionic conductivity at room temperature, strong thermal stability, and excellent mechanical properties. However, due to their high mechanical strength, they are difficult to process, and the interface contact between the inorganic electrolyte and the electrode is poor, and high interfacial impedance is likely to occur, resulting in weak electrochemical performance. The ionic conductivity of polymer electrolytes is low, but they have strong ductility, are easy to form films, have good contact with the electrode interface, are easier to mold, and can be mass-produced. Since the polymer itself does not have lithium-ion conductivity, it needs to be combined with a lithium salt, and lithium ions (Li + ) are transmitted depending on the segmental motion in the amorphous region of the polymer.

[0004] To combine the advantages of polymer electrolytes and inorganic electrolytes, the two are usually compounded to form an organic-inorganic composite electrolyte. Inorganic solid electrolytes can currently achieve a high ionic conductivity of 10 -3 S / cm at room temperature, which is almost the same as that of liquid electrolytes. Garnet-type solid electrolytes (LLZO) and sulfide solid electrolytes are two of the most common inorganic ceramic electrolytes. Garnet-type solid electrolytes are typical inorganic ceramic electrolytes, relatively stable against water and oxygen in the air, and advantageous for fabrication. Also, LLZO has stable electrochemical properties when contacting ordinary solvents and is likely to form a composite electrolyte when compounded with polymers. Since the polymer itself does not contain lithium ions, current research usually additionally adds lithium salts such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to the substrate, but lithium salts are expensive and there are problems leading to an increase in cost. Also, since lithium salts react with water, it is necessary to compound them in an inert gas atmosphere. Therefore, adding lithium salts increases the fabrication cost and difficulty of the composite electrolyte.

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present application is to provide a lithium salt-free composite solid electrolyte membrane and a method for fabricating the same to solve to some extent the problems that the fabrication cost of conventional solid electrolyte membranes is high and the fabrication process is complicated.

Means for Solving the Problems

[0006] The present application adopts the following technical solutions.

[0007] One aspect of the embodiment of the present application provides a lithium salt-free composite solid electrolyte membrane. The components of the lithium salt-free composite solid electrolyte membrane are a garnet solid electrolyte and a polymer in the micro-nano order. Here, the weight ratio of the garnet-type solid electrolyte in the micro-nano order to the polymer is (60-100):(5-40), and the particle size of the garnet-type solid electrolyte in the micro-nano order is 100 nm to 2 μm.

[0008] The lithium salt-free composite solid electrolyte membrane of the embodiment of the present application is composed of a garnet solid electrolyte and a polymer, and there is no need to add a lithium salt, which can reduce the demand for an inert atmosphere and reduce the manufacturing cost. In addition, the particle size of the garnet solid electrolyte of the embodiment of the present application is small, which is advantageous for sufficient mixing with the polymer, and can guarantee mechanical properties such as the uniformity and toughness of the lithium salt-free composite solid electrolyte membrane.

[0009] In some embodiments, the weight ratio of the garnet-type solid electrolyte in the micro-nano order to the polymer is preferably (70-90):(10-30), and the particle size of the garnet-type solid electrolyte in the micro-nano order is preferably 100 nm to 1 μm.

[0010] In some embodiments, the polymer is one or a combination of two or more of polyethylene oxide, polyvinylidene fluoride, or polyvinylidene fluoride-hexafluoropropylene, and is preferably polyethylene oxide.

[0011] Another aspect of the embodiment of the present application further provides a method for manufacturing the above lithium salt-free composite solid electrolyte membrane, including the following steps. (1) Grind the garnet solid electrolyte with a wet ball mill and dry it by vacuum rotary evaporation to obtain a garnet solid electrolyte in the micro-nano order. (2) Mix the garnet solid electrolyte in the micro-nano order and the polymer in a solvent to obtain a colloidal solution. (3) Apply the colloidal solution and dry it to obtain a lithium salt-free composite solid electrolyte membrane.

[0012] In the method for preparing the lithium salt-free composite solid electrolyte membrane of the examples of this application, since the garnet-type solid electrolyte is ground by a wet ball mill and dried by vacuum rotary evaporation, compared with static drying in a normal vacuum oven, vacuum rotary evaporation drying can retain the small-sized particles after grinding to the maximum extent, and the size is uniform, can be sufficiently mixed with the polymer, the manufacturing method is simple and easy to operate, and is advantageous for mass production.

[0013] In some examples, in step (2), the mixing of the micronano-order garnet-type solid electrolyte and the polymer is carried out in an air atmosphere, the mixing temperature is 25 to 80 °C, and the mixing time is 1 to 10 h.

[0014] In some examples, in step (1), the rotation speed of the wet ball mill grinding is 100 to 500 r / min, the ball mill grinding time is 1 to 20 h, and the solvent used for the wet ball mill grinding is isopropanol. The vacuum rotary evaporation temperature is 40 to 60 °C, and the rotation speed is 100 to 300 r / min.

[0015] In some examples, in step (2), the solvent is one or a mixture of acetonitrile and dimethyl sulfoxide.

[0016] In some examples, in step (1), the garnet-type solid electrolyte is prepared by a method including the following steps: mixing a lithium source, a lanthanum source, a zirconium source, and an oxygen source in a certain proportion, pressing them into a sheet, and firing them in a pure oxygen atmosphere at 900 to 1300 °C to obtain a garnet-type solid electrolyte.

[0017] Yet another aspect of the embodiments of the present application provides an application of the above lithium salt-free composite solid electrolyte membrane in a solid battery, where the lithium salt-free composite solid electrolyte membrane is used as an electrolyte membrane of the solid battery, and here, the thickness of the lithium salt-free composite solid electrolyte membrane is 10 to 400 μm.

Advantages of the Invention

[0018] The present application has the following advantages and beneficial effects.

[0019] The lithium salt-free composite solid electrolyte membrane of the embodiments of the present application is composed of a garnet-type solid electrolyte in the micronano order and a polymer, and there is no need to add a lithium salt. Here, the garnet-type solid electrolyte in the micronano order increases the ionic conductivity and ensures the ionic conductivity of the lithium salt-free composite solid electrolyte membrane. The introduction of the polymer enhances the ductility and processability of the lithium salt-free composite solid electrolyte membrane, eliminating the need to add a lithium salt and reducing the manufacturing cost and difficulty of the solid electrolyte membrane.

[0020] The manufacturing method of the lithium salt-free composite solid electrolyte membrane of the embodiments of the present application is simple. The mixing of the garnet-type solid electrolyte in the micronano order and the polymer can be carried out in air, eliminating the need for an anhydrous and inert atmosphere to guarantee the quality of the lithium salt, enhancing the availability in actual production, and having an advantage in mass production.

[0021] In the embodiments of the present application, the particle size of the garnet-type solid electrolyte obtained by wet ball milling is small and it is dried by vacuum rotary evaporation. Therefore, compared with static drying in an ordinary vacuum oven, the vacuum rotary evaporation method can retain the garnet-type solid electrolyte particles with a small size and uniform size and morphology obtained by wet ball milling, which is beneficial for sufficient mixing with the polymer and can ensure the integrity and toughness of the lithium salt-free composite solid electrolyte membrane.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0023] Hereinafter, the examples of the present application will be described in detail. The above examples are illustrative and are used for the description of the present application and do not limit the present application.

[0024] One aspect of the example of the present application provides a lithium salt-free composite solid electrolyte membrane. The components of the lithium salt-free composite solid electrolyte membrane are garnet solid electrolyte and polymer in the micronano order. Here, the weight ratio of the garnet-type solid electrolyte and polymer in the micronano order is (60-100):(5-40), and the particle size of the garnet-type solid electrolyte in the micronano order is 100 nm - 2 μm.

[0025] The lithium salt-free composite solid electrolyte membrane of the example of the present application is composed of a garnet-type solid electrolyte and a polymer, and there is no need to add a lithium salt, which can reduce the demand for an inert atmosphere and reduce the manufacturing cost. In addition, the particle size of the garnet-type solid electrolyte in the example of the present application is small, which is advantageous for sufficient mixing with the polymer, and can guarantee mechanical properties such as the uniformity and toughness of the lithium salt-free composite solid electrolyte membrane.

[0026] In some embodiments, the weight ratio of the garnet-type solid electrolyte in the micro-nano order to the polymer is preferably (70-90):(10-30), and the particle size of the garnet-type solid electrolyte in the micro-nano order is preferably 100 nm to 1 μm. By adjusting the ratio of the garnet-type solid electrolyte in the micro-nano order to the polymer within an appropriate range, on the premise of ensuring high conductivity, the composite solid electrolyte membrane can be made to have a certain toughness.

[0027] In some embodiments, the polymer is one or a combination of two or more of polyethylene oxide, polyvinylidene fluoride, or polyvinylidene fluoride-hexafluoropropylene, and is preferably polyethylene oxide.

[0028] Another aspect of the embodiments of the present application further provides a method for preparing the above lithium salt-free composite solid electrolyte membrane, including the following steps. (1) Grind the garnet-type solid electrolyte with a wet ball mill and dry it by vacuum rotary evaporation to obtain a garnet-type solid electrolyte in the micro-nano order. (2) Mix the garnet-type solid electrolyte in the micro-nano order and the polymer in a solvent to obtain a colloidal solution. (3) Apply the colloidal solution and dry it to obtain a lithium salt-free composite solid electrolyte membrane.

[0029] In the method for preparing the lithium salt-free composite solid electrolyte membrane of the embodiments of the present application, since the garnet-type solid electrolyte is ground with a wet ball mill and dried by vacuum rotary evaporation, compared with static drying in a normal vacuum oven, vacuum rotary evaporation drying can retain the small-sized particles after grinding to the maximum extent, and has a uniform size, can be sufficiently mixed with the polymer, has a simple manufacturing method and is easy to operate, which is advantageous for mass production.

[0030] In some embodiments, in step (2), the mixing of the garnet-type solid electrolyte in the micronano order and the polymer is carried out in an air atmosphere, without the need to control an anhydrous and inert atmosphere, and there is an advantage in mass production. Here, the mixing temperature is 25 to 80 °C, and the mixing time is 1 to 10 h.

[0031] In some embodiments, in step (1), the rotation speed of the wet ball mill grinding is 100 to 500 r / min, the ball mill grinding time is 1 to 10 h, the solvent used for the wet ball mill grinding is isopropanol, the vacuum rotary evaporation temperature is 40 to 60 °C, and the rotation speed is 10 to 300 r / min.

[0032] In some embodiments, in step (2), the solvent is one kind or a mixture of acetonitrile and dimethyl sulfoxide.

[0033] In some embodiments, in step (1), the garnet-type solid electrolyte is prepared by a method including the following steps: mixing a lithium source, a lanthanum source, a zirconium source, and an oxygen source in a certain proportion, pressing them into a sheet, and firing them in a pure oxygen atmosphere at 900 to 1300 °C to obtain the garnet-type solid electrolyte.

[0034] Another aspect of the embodiment of the present application provides an application of the above lithium salt-free composite solid electrolyte membrane in a solid battery. The above lithium salt-free composite solid electrolyte membrane is used as an electrolyte membrane of the solid battery. Here, the thickness of the lithium salt-free composite solid electrolyte membrane is 10 to 400 μm.

[0035] Hereinafter, the lithium salt-free composite solid electrolyte membrane of the present application and its manufacturing method will be described in more detail through specific examples.

Example

[0036] Example 1 A method for manufacturing a lithium salt-free solid electrolyte membrane, including the following steps. (1) The garnet-type solid electrolyte (LLZO) was pulverized by a wet ball mill, and then the garnet-type solid electrolyte pulverized at a rotation speed of 40 r / min under a temperature condition of 50 °C was dried by vacuum rotary evaporation to obtain a garnet-type solid electrolyte in the micro-nano order, and its particle size was about 1 μm. (2) Polyethylene oxide (PEO) was previously dissolved in acetonitrile, and the micro-nano order garnet-type solid electrolyte obtained from step (1) was added to a mixed solution of polyethylene oxide and acetonitrile (where the weight ratio of the micro-nano order garnet-type solid electrolyte to polyethylene oxide is 75:25). Then, magnetic stirring was carried out at 25 °C and a rotation speed of 200 r / min for 3 h to obtain a colloidal solution. (3) The above colloidal solution was applied to the surface of a glass plate using a scraper, and the coating thickness was 300 μm. After coating, the glass plate was placed in a vacuum oven and dried at 60 °C for 12 h to obtain a lithium salt-free composite solid electrolyte membrane.

[0037] Figure 2 is an optical photograph of the lithium salt-free composite solid electrolyte membrane of this example. According to the results, the lithium salt-free composite solid electrolyte membrane prepared in this example has a complete structure and certain toughness.

[0038] Figure 3 is an SEM image of the lithium salt-free composite solid electrolyte membrane of this example. According to the results, microscopically, the garnet-type solid electrolyte membrane is uniformly dispersed in the polyethylene oxide matrix.

[0039] Figure 4 is an EIS spectrum of the lithium salt-free composite solid electrolyte membrane of this example. As can be seen from Figure 4, the ionic conductivity of the lithium salt-free composite solid electrolyte membrane prepared in this example can reach 1.14×10 -4 S / cm, and there is a high possibility of practical application.

Example

[0040] Example 2 A method for preparing a lithium salt-free solid electrolyte membrane, comprising the following steps. (1) After grinding garnet-type solid electrolyte (LLZO) with a wet ball mill, the garnet-type solid electrolyte ground at a rotation speed of 40 r / min under a temperature condition of 50 °C is dried by vacuum rotary evaporation to obtain a garnet-type solid electrolyte in the micro-nano order, and its particle size is about 1 μm. (2) Polyethylene oxide (PEO) is dissolved in acetonitrile in advance, and the micro-nano order garnet-type solid electrolyte obtained from step (1) is added to a mixed solution of polyethylene oxide and acetonitrile (here, the weight ratio of the micro-nano order garnet-type solid electrolyte to polyethylene oxide is 70:30). Then, magnetic stirring is carried out at 25 °C and a rotation speed of 200 r / min for 3 h to obtain a colloidal solution. (3) The above colloidal solution is applied to the surface of a glass plate using a scraper, the coating thickness is 300 μm. After coating, the glass plate is placed in a vacuum oven and dried at 60 °C for 12 h to obtain a lithium salt-free composite solid electrolyte membrane.

Example

[0041] Example 3 A method for preparing a lithium salt-free solid electrolyte membrane, comprising the following steps. (1) After grinding garnet-type solid electrolyte (LLZO) with a wet ball mill, the garnet-type solid electrolyte ground at a rotation speed of 40 r / min under a temperature condition of 50 °C is dried by vacuum rotary evaporation to obtain a garnet-type solid electrolyte in the micro-nano order, and its particle size is about 1 μm. (2) Polyethylene oxide (PEO) is dissolved in acetonitrile in advance, and the micro-nano order garnet-type solid electrolyte obtained from step (1) is added to a mixed solution of polyethylene oxide and acetonitrile (here, the weight ratio of the micro-nano order garnet-type solid electrolyte to polyethylene oxide is 70:30). Then, magnetic stirring is carried out at 25 °C and a rotation speed of 200 r / min for 3 h to obtain a colloidal solution. (3) Use a scraper to apply the above colloidal solution onto the surface of a glass plate. The coating thickness is 400 μm. After coating, place the glass plate in a vacuum oven and dry it at 60 °C for 12 h to obtain a lithium salt-free composite solid electrolyte membrane.

[0042] In this application, terms such as "one embodiment", "several embodiments", "illustration", "specific illustration", or "several illustrations" indicate that the specific features, structures, materials, or characteristics described in the above embodiments or illustrations are included in at least one embodiment or illustration of this application. In this specification, the schematic expressions of the above terms do not necessarily target the same embodiment or illustration. Furthermore, the specific features, structures, materials, or characteristics described here can be combined in a suitable manner in one or more embodiments or illustrations. Moreover, when there is no contradiction, those skilled in the art can combine and combine the features of different embodiments or illustrations described in this specification.

[0043] As described above, the embodiments of this application have been shown and described. However, the above embodiments are illustrative and do not limit this application. Those skilled in the art can make changes, modifications, substitutions, and deformations to the above embodiments within the scope of this application.

Claims

1. A lithium salt-free composite solid electrolyte membrane, wherein the components of the lithium salt-free composite solid electrolyte membrane are a garnet solid electrolyte and a polymer in the micronano order, wherein the weight ratio of the garnet-type solid electrolyte in the micronano order to the polymer is (60-100):(5-40), and the particle size of the garnet-type solid electrolyte in the micronano order is 100 nm to 2 μm, the lithium salt-free composite solid electrolyte membrane.

2. The weight ratio of the garnet-type solid electrolyte in the micronano order to the polymer is (70-90):(10-30), and the particle size of the garnet-type solid electrolyte in the micronano order is 100 nm to 1 μm, the lithium salt-free composite solid electrolyte membrane according to Claim 1.

3. The polymer is one or a combination of two or more of polyethylene oxide, polyvinylidene fluoride, or polyvinylidene fluoride-hexafluoropropylene, the lithium salt-free composite solid electrolyte membrane according to Claim 1.

4. A method for producing the lithium salt-free composite solid electrolyte membrane according to any one of Claims 1 to 3, comprising the following steps: (1) Grinding a garnet-type solid electrolyte with a wet ball mill and drying it by vacuum rotary evaporation to obtain a garnet-type solid electrolyte in the micronano order; (2) Mixing the garnet-type solid electrolyte in the micronano order and the polymer in a solvent to obtain a colloidal solution; (3) Coating the colloidal solution and drying it to obtain a lithium salt-free composite solid electrolyte membrane, the method for producing the lithium salt-free composite solid electrolyte membrane.

5. In step (2), the mixing of the garnet-type solid electrolyte in the micronano order and the polymer is carried out in an air atmosphere, the mixing temperature is 25-80°C, and the mixing time is 1-10 h, the method for producing the lithium salt-free composite solid electrolyte membrane according to Claim 4.

6. In step (1), the rotation speed of the wet ball mill grinding is 100-500 r / min, and the ball mill grinding time is 1-20 h, the method for producing the lithium salt-free composite solid electrolyte membrane according to Claim 4.

7. In step (1), the vacuum rotary evaporation temperature is 40-60°C, and the rotation speed is 100-300 r / min, the method for producing the lithium salt-free composite solid electrolyte membrane according to Claim 4.

8. The method for producing a lithium salt-free composite solid electrolyte membrane according to claim 4, wherein in step (2), the solvent is one kind or a mixture of acetonitrile and dimethyl sulfoxide.

9. The method for producing a lithium salt-free composite solid electrolyte membrane according to claim 4, wherein in step (1), the garnet-type solid electrolyte is produced by a method including the following steps: a lithium source, a lanthanum source, a zirconium source, and an oxygen source are mixed in a certain proportion and pressed into a sheet, and then fired in a pure oxygen atmosphere at 900 to 1300 °C to obtain a garnet-type solid electrolyte.

10. An application in a solid battery of the lithium salt-free composite solid electrolyte membrane according to any one of claims 1 to 3, wherein the lithium salt-free composite solid electrolyte membrane is used as an electrolyte membrane of the solid battery, The application in a solid battery of the lithium salt-free composite solid electrolyte membrane, wherein the thickness of the lithium salt-free composite solid electrolyte membrane is 10 to 400 μm.

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