Preparation method of porous solid electrolyte and its application

Abstract

The present invention discloses a method for preparing a porous solid electrolyte and its application, belonging to the field of electrochemical technology. A MOF material and solid electrolyte powder are uniformly mixed in an inert solvent, and the inert solvent is evaporated to obtain a mixed powder A; the mixed powder A is spread on the solid electrolyte powder and pressed to form a green body; and the green body is sintered to form a porous solid electrolyte with multiple holes on one side. The present invention uses an organic shell in the MOF material as a pore-forming agent. After the mixed powder A and the solid electrolyte powder are pressed and sintered, the metal core of the MOF material is converted into a metal element or a corresponding metal oxide, which adheres to the surface of the formed pores to form a three-dimensional network structure. The metal core of the MOF material in the obtained porous solid electrolyte can directly serve as a seed to induce an alkali metal negative electrode to recombine with the alkali metal negative electrode, without the need for additional complex processes to surface treat the three-dimensional network structure. The preparation efficiency is high and the cost is low.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical technology, and more specifically, relates to a preparation method of a porous solid electrolyte and an application thereof. Background Art

[0002] Lithium-ion batteries are a low-cost, long-life, high-efficiency rechargeable battery technology that is widely used in mobile phones, laptops, electric vehicles, and large-scale energy storage systems. However, their energy density and safety can no longer meet the needs of electric vehicles for long driving range and high safety. In contrast, solid-state alkali metal batteries use high-capacity, low-voltage alkali metals as negative electrodes, which are expected to significantly increase battery energy density. At the same time, solid-state alkali metal batteries replace flammable organic electrolytes with non-flammable solid electrolytes, which can fundamentally solve battery safety issues. For solid electrolytes, compared with planar solid electrolytes, porous solid electrolytes can improve the utilization rate of active materials in the alkali metal negative electrode and achieve stable cycling of solid-state batteries at high current density and surface capacity. Therefore, it is of great significance to study a method for preparing porous solid electrolytes.

[0003] Existing methods for preparing porous solid-state electrolytes often involve creating pores using a pore-forming agent to form a three-dimensional network structure. This network is then surface-treated to increase its affinity for alkali metal anodes, thereby facilitating subsequent composite bonding with the alkali metal anode. However, this entire process requires two steps, and the surface treatment of the three-dimensional network structure often requires complex techniques such as magnetron sputtering and atomic layer deposition, resulting in low production efficiency and high costs. Summary of the Invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a method for preparing a porous solid electrolyte and its application, the purpose of which is to provide a low-cost and high-efficiency method for preparing a porous solid electrolyte.

[0005] In order to achieve the above objectives, in a first aspect, the present invention provides a method for preparing a porous solid electrolyte, comprising:

[0006] The MOF material and the solid electrolyte powder are uniformly mixed in an inert solvent, and the inert solvent is evaporated to obtain a mixed powder A;

[0007] The mixed powder A is spread on the solid electrolyte powder and pressed to form a green body; the green body is sintered to obtain a porous solid electrolyte with porous one side.

[0008] More preferably, the MOF material is a network metal organic framework material, a zeolite imidazole framework material, a Levahill framework material or a pore channel framework material.

[0009] Further preferably, the solid electrolyte powder is garnet-type oxide, β″-alumina, NASICON-type solid electrolyte powder, argyrodite-type solid electrolyte powder, alkali metal nitride or LiPON-type solid electrolyte powder.

[0010] Further preferably, the mass ratio of the MOF material and the solid electrolyte powder mixed in the inert solvent is 1:1 to 1:5.

[0011] More preferably, the sintering temperature is 500°C to 1700°C.

[0012] In a second aspect, the present invention provides a porous solid electrolyte prepared by the method for preparing the porous solid electrolyte provided in the first aspect of the present invention.

[0013] In a third aspect, the present invention provides a method for preparing a solid-state alkali metal battery negative electrode, comprising:

[0014] The porous side of the porous solid electrolyte is brought into contact with a molten alkali metal material, thereby inducing the molten alkali metal material to fill the pores in the porous solid electrolyte, thereby forming a composite solid alkali metal battery negative electrode in which the solid electrolyte and the alkali metal material permeate each other;

[0015] The porous solid electrolyte is the porous solid electrolyte provided in the second aspect of the present invention.

[0016] More preferably, the temperature of the alkali metal material in a molten state is 150°C to 500°C.

[0017] In a fourth aspect, the present invention provides a porous solid electrolyte negative electrode, which is prepared using the method for preparing a solid alkali metal battery negative electrode provided by the third aspect of the present invention.

[0018] In a fifth aspect, the present invention provides a solid-state alkali metal battery, the negative electrode of which is the porous solid electrolyte negative electrode provided by the fourth aspect of the present invention.

[0019] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0020] 1. The present invention provides a method for preparing a porous solid electrolyte, comprising uniformly mixing a MOF material and a solid electrolyte powder in an inert solvent, and evaporating the inert solvent to obtain a mixed powder A; spreading the mixed powder A on the solid electrolyte powder and pressing it to form a green body; and sintering the green body so that the mixed powder A forms a strong bond with the high-density solid electrolyte powder, thereby forming a porous solid electrolyte with multiple holes on one side. The present invention utilizes the organic shell in the MOF material as a pore-forming agent. After the mixed powder A and the solid electrolyte powder are pressed and sintered, the metal core of the MOF material is converted into a metal element or a corresponding metal oxide, which adheres to the surface of the formed pores to form a three-dimensional network structure. The metal core of the MOF material in the resulting porous solid electrolyte can directly serve as a seed to induce the alkali metal negative electrode to recombine with it, eliminating the need for additional complex processes to surface-treat the three-dimensional network structure. This results in high preparation efficiency and low cost.

[0021] 2. The preparation method of the porous solid electrolyte provided by the present invention and the prepared porous solid electrolyte with a three-dimensional network structure can solve the problems of low negative electrode ion migration depth, only alkali metal near the interface having electrochemical activity, and poor interface wettability when the solid electrolyte with a planar structure is combined with an alkali metal negative electrode. It can significantly improve the ion migration efficiency in the negative electrode, reduce the charge transfer energy barrier, improve the utilization rate of the active material of the alkali metal negative electrode, and realize stable circulation of solid-state batteries at high current density and surface capacity.

[0022] 3. The present invention provides a method for preparing a negative electrode of a solid-state alkali metal battery. By using the metal core of the MOF material as a seed to induce the alkali metal material to composite with the porous side of a porous solid electrolyte, the metal core in the MOF material can form a single substance or oxide under high temperature conditions, which serves as a nucleation center to induce the alkali metal material to fill the pores of the porous solid electrolyte, thereby increasing the active area of ​​the electrochemical reaction and improving the charge transfer rate. The entire process is simple, the preparation efficiency is high, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of a method for preparing a porous solid electrolyte provided by the present invention;

[0024] Figure 2 Schematic diagram of the morphology of the Ag-MOF material obtained in an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the SEM morphology of porous LLZTO loaded with Ag nanoparticles provided in an embodiment of the present invention;

[0026] Figure 4 Critical current density diagram of porous LLZTO prepared with different mass ratios of solid electrolyte powder and pore-forming agent provided in an embodiment of the present invention;

[0027] Figure 5 Schematic diagram of the SEM morphology of the porous LLZTO after the molten Li metal material provided in an embodiment of the present invention is filled;

[0028] Figure 6 The lithium symmetric battery assembled from the obtained solid-state Li metal battery negative electrode provided in the embodiment of the present invention is 1mA cm -2 The cycle performance diagram below;

[0029] Figure 7 A rate performance diagram of a lithium iron phosphate full battery assembled from the obtained solid-state Li metal battery negative electrode provided in an embodiment of the present invention;

[0030] Figure 8 The present invention provides a charge and discharge curve of a lithium iron phosphate full battery assembled from the obtained solid-state Li metal battery negative electrode at different rates. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] In order to achieve the above objectives, in a first aspect, the present invention provides a method for preparing a porous solid electrolyte, such as Figure 1 As shown, including:

[0033] The MOF (metal organic framework) material and the solid electrolyte powder are uniformly mixed in an inert solvent, and the inert solvent is evaporated to obtain a mixed powder A;

[0034] The mixed powder A is spread on the solid electrolyte powder and pressed to form a green body; the green body is sintered to obtain a porous solid electrolyte with porous one side.

[0035] It should be noted that after sintering, the metal core of the MOF material is transformed into a single metal or the corresponding metal oxide, which adheres to the surface of the porous solid electrolyte framework. The organic shell in the MOF material can act as a pore-forming agent, regulating the size, number, and distribution of pores in the porous solid electrolyte and constructing a network structure. The network-like porous solid electrolyte can significantly improve the ion migration efficiency in the negative electrode, reduce the charge transfer energy barrier, and improve the utilization rate of the negative electrode active material.

[0036] In an optional embodiment, the MOF material can be: reticulated metal organic framework materials (IRMOFs), zeolite imidazole framework materials (ZIFs), Levahill framework materials (MILs), pore channel framework materials (PCNs), etc.

[0037] In an alternative embodiment, a solvothermal method can be used to prepare MOF materials: nitrate is dissolved in anhydrous methanol to obtain solution A; 2-aminoterephthalic acid is dissolved in dimethylformamide (DMF) to obtain solution B; solution B is then mixed with solution A and subjected to a hydrothermal reaction to synthesize the corresponding MOF material. Nitrates are preferably AgNO3, Zn(NO3)2, Fe(NO3)3, CuNO3, Mg(NO3)2, Al(NO3)3, Sn(NO3)4, Pb(NO3)2, etc., to synthesize MOF materials with different metal cores.

[0038] In an optional embodiment, the solid electrolyte powder is preferably a solid electrolyte powder that is chemically stable with alkali metals, such as garnet-type oxide, β″-alumina, NASICON-type solid electrolyte powder, argyrodite-type solid electrolyte powder, alkali metal nitride, and LiPON-type solid electrolyte powder.

[0039] In an optional embodiment, the mass ratio of the MOF material and the solid electrolyte powder mixed in the inert solvent is 1:1 to 1:5.

[0040] In an optional embodiment, the sintering temperature is 500°C to 1700°C.

[0041] In an alternative embodiment, the inert solvent may be isopropyl alcohol, n-heptane, toluene, benzene, xylene, carbon disulfide, or the like.

[0042] In order to further illustrate the preparation method of the porous solid electrolyte provided by the present invention, the following is a detailed description with reference to specific examples:

[0043] This embodiment provides a porous garnet solid electrolyte (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , LLZTO) preparation method, specifically comprising the following process:

[0044] Preparation of MOF materials:

[0045] In this example, taking AgNO3 as nitrate as an example, 1 mmol of AgNO3 was dissolved in 50 mL of anhydrous methanol to obtain solution A; 1 mmol of 2-aminoterephthalic acid was dissolved in 10 mL of DMF solution to obtain solution B; then solution B was slowly added dropwise to solution A using a syringe pump. Subsequently, the mixture was transferred to a 100 mL stainless steel reactor with a Teflon lining, sealed, and heated at 120°C for 12 hours. The precipitate was collected by centrifugation, washed alternately with DMF and ethanol three times, and dried in a vacuum oven at 60°C overnight to obtain an Ag-MOF material, such as Figure 2 shown.

[0046] Preparation of porous solid electrolytes:

[0047] The MOF material and solid electrolyte powder are mixed and stirred uniformly in an inert solvent, and the inert solvent is evaporated to obtain mixed powder A. Solid electrolyte powder B and mixed powder A are sequentially added to a tableting mold and pressed to obtain a green body, which is sintered at a high temperature to obtain a porous solid electrolyte.

[0048] In this embodiment, Ag-MOF material and solid electrolyte powder LLZTO are mixed and stirred in a n-heptane solvent at a mass ratio of 1:2, and the solvent is evaporated to obtain mixed powder A. 0.1g of LLZTO powder and 0.05g of mixed powder A are sequentially added to a tableting mold, and tablets are pressed at 300MPa to obtain a green blank. The green blank is sintered at 1250°C for 20 minutes to obtain porous LLZTO. The organic shell of Ag-MOF decomposes at high temperature, leaving pores, which helps to construct a porous LLZTO network. The Ag metal core forms a single Ag particle loaded on the surface of the porous LLZTO, such as Figure 3 shown.

[0049] In addition, the present invention also compares the performance of porous LLZTO prepared by solid electrolyte powder LLZTO and MOF material (pore forming agent) with different mass ratios through different embodiments, and obtains the following results as shown in Table 1 and Figure 4 The results shown in Table 1 are the critical current density data of porous LLZTO prepared with different mass ratios of solid electrolyte powder and pore-forming agent provided in the embodiment of the present invention, as well as the critical current density data when the pore-forming agent is replaced by Sn-MOF; Figure 4 The critical current density diagram of porous LLZTO prepared with different mass ratios of solid electrolyte powder and pore-forming agent. Figure 4 It can be seen that compared with the control example without pore-forming agent, the performance of the examples with pore-forming agent is improved. When the mass ratio of solid electrolyte powder to MOF material is 2:1, the critical current density is the highest, reaching 1.2 mA cm -2, indicating that the porous LLZTO has the strongest ability to inhibit dendrite growth under this condition. In addition, when Ag-MOF is replaced by Sn-MOF, the critical current density of the prepared porous LLZTO can still be increased to 0.9 mA cm -2 , indicating that this type of method is universal.

[0050] Table 1

[0051] solid electrolyte pore-forming agent Mass ratio <![CDATA[Critical current density of symmetric battery (mA cm -2 )]]> Example 1 <![CDATA[Ii 6.4 La3Zr 1.4 Yes 0.6 Oh 12 ]]> Ag-MOF 1：1 0.5 Example 2 <![CDATA[Ii 6.4 La3Zr 1.4 Yes 0.6 Oh 12 ]]> Ag-MOF 2：1 1.2 Example 3 <![CDATA[Li 6.4 La3Zr 1.4 Yes 0.6 Oh 12 ]]> Ag-MOF 3：1 0.6 Example 4 <![CDATA[Li 6.4 La3Zr 1.4 Yes 0.6 Oh 12 ]]> Ag-MOF 5：1 0.3 Example 5 <![CDATA[Li 6.4 La3Zr 1.4 Yes 0.6 Oh 12 ]]> Ag-MOF 6：1 0.1 Example 6 <![CDATA[Li 6.4 La3Zr 1.4 Yes 0.6 oh 12 ]]> Sn-MOF 2：1 09 Comparative Example <![CDATA[Li 6.4 La3Zr 1.4 Yes 0.6 Oh 12 ]]> none 1：0 0.2

[0052] It should be noted that this embodiment only uses LLZTO as a representative of solid electrolyte powder for illustration. The performance of other solid electrolyte powders is similar to that of LLZTO and will not be described in detail here.

[0053] In a second aspect, the present invention provides a porous solid electrolyte prepared by the method for preparing the porous solid electrolyte provided in the first aspect of the present invention.

[0054] The related technical solution is the same as the method for preparing the porous solid electrolyte provided in the first aspect of the present invention, and will not be described in detail here.

[0055] In an optional embodiment, the temperature of the alkali metal material in a molten state is 150°C to 500°C.

[0056] It should be noted that the above-mentioned alkali metal material can be an alkali metal material such as Li, Na, K, Cs, etc.

[0057] It should be noted that after the porous side of the porous solid electrolyte comes into contact with the molten alkali metal material, the metal element or the corresponding metal oxide in the pores of the porous solid electrolyte undergoes an alloying reaction or a replacement reaction with the alkali metal material, inducing the molten alkali metal material to fill the pores in the porous solid electrolyte, forming a composite negative electrode in which the solid electrolyte and the alkali metal material interpenetrate, i.e., the solid-state alkali metal battery negative electrode. When the pores of the porous solid electrolyte contain a metal element, the metal element undergoes an alloying reaction with the alkali metal material; when the pores of the porous solid electrolyte contain a metal oxide, the metal oxide undergoes a replacement reaction with the alkali metal material, and may further undergo an alloying reaction.

[0058] The present invention uses the metal core of the MOF material as a seed to induce the alkali metal material to composite with the porous solid electrolyte. The metal core in the MOF material can form a single substance or oxide under high temperature conditions, serving as a nucleation center to induce the alkali metal material to fill the pores of the porous solid electrolyte, thereby increasing the active area of ​​the electrochemical reaction and improving the charge transfer rate.

[0059] To further illustrate the preparation method of the solid-state alkali metal battery negative electrode provided by the present invention, the following is a specific description using the LLZTO obtained in the above-mentioned porous solid electrolyte preparation method example as the porous solid electrolyte and Li metal as the alkali metal material as an example:

[0060] The porous side of the LLZTO obtained in the preparation method of the porous solid electrolyte is brought into contact with metallic lithium melted at 200°C to induce an alloying reaction, so that the molten lithium fills the pores in the porous LLZTO, forming a morphology in which the metallic lithium and the porous LLZTO network permeate each other, thereby obtaining a solid-state Li metal battery negative electrode, such as Figure 5 shown.

[0061] The lithium symmetric battery assembled from the obtained solid-state Li metal battery anode was tested at 1 mA cm -2 The cycle performance test was carried out under Figure 6 The cycling performance diagram shown in the figure shows that the lithium symmetric battery can be stably cycled for more than 950h with a polarization of 25mV, indicating that the porous LLZTO network can significantly promote the lithium ion conduction of the negative electrode, reduce the Li concentration gradient, and thus inhibit the formation of dendrites.

[0062] The rate performance of the lithium iron phosphate full battery assembled from the obtained solid-state Li metal battery negative electrode was tested, and the results were as follows: Figure 7 The rate performance diagram shown in the figure shows that at 0.1, 0.2, 0.5, 1.0 and 2.0C, the battery capacities are 155.9, 154.9, 149.2, 136.9 and 119 mAh g -1 When the rate returns to 0.1C, the discharge capacity can be restored to 153.8mAh g -1 , indicating that the porous LLZTO network provides a stable ion percolation pathway, increases the anode ion migration depth, improves the electrode reaction kinetics, and relieves the anode stress / strain, thus achieving excellent rate performance.

[0063] The charge and discharge performance of the lithium iron phosphate full battery assembled from the obtained solid-state Li metal battery negative electrode was tested at different rates, and the following results were obtained: Figure 8 The charge and discharge curve is shown in the figure; it can be seen from the figure that even at a high rate of 2C, the battery still maintains a stable voltage curve, indicating that the obtained solid-state Li metal battery negative electrode has high structural stability.

[0064] In a third aspect, the present invention provides a method for preparing a solid-state alkali metal battery negative electrode, comprising:

[0065] The porous side of the porous solid electrolyte is brought into contact with a molten alkali metal material, thereby inducing the molten alkali metal material to fill the pores in the porous solid electrolyte, thereby forming a composite solid alkali metal battery negative electrode in which the solid electrolyte and the alkali metal material permeate each other;

[0066] The porous solid electrolyte is the porous solid electrolyte provided in the second aspect of the present invention. The related technical solutions are the same as the porous solid electrolyte provided in the second aspect of the present invention, and are not described in detail here.

[0067] In a fourth aspect, the present invention provides a porous solid electrolyte negative electrode, which is prepared using the method for preparing a solid alkali metal battery negative electrode provided by the third aspect of the present invention.

[0068] The related technical solution is the same as the method for preparing the solid-state alkali metal battery negative electrode provided in the third aspect of the present invention, and will not be described in detail here.

[0069] In a fifth aspect, the present invention provides a solid-state alkali metal battery, the negative electrode of which is the porous solid electrolyte negative electrode provided by the fourth aspect of the present invention.

[0070] The relevant technical solution is the same as the porous solid electrolyte negative electrode provided in the fourth aspect of the present invention, and will not be described in detail here.

[0071] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a porous solid electrolyte, characterized in that: include: The MOF material and the solid electrolyte powder are uniformly mixed in an inert solvent, and the inert solvent is evaporated to obtain a mixed powder A; The mixed powder A is spread on the solid electrolyte powder and pressed to form a green body; the green body is sintered to obtain a porous solid electrolyte with porous one side.

2. The method for preparing a porous solid electrolyte according to claim 1, wherein: The MOF material is a mesh metal organic framework material, a zeolite imidazole framework material, a Levahill framework material or a pore channel framework material.

3. The method for preparing a porous solid electrolyte according to claim 1, wherein: The solid electrolyte powder is garnet-type oxide, β″-alumina, NASICON-type solid electrolyte powder, argyrodite-type solid electrolyte powder, alkali metal nitride or LiPON-type solid electrolyte powder.

4. The method for preparing a porous solid electrolyte according to any one of claims 1 to 3, characterized in that: The mass ratio of the MOF material and the solid electrolyte powder mixed in the inert solvent is 1:1 to 1:

5.

5. The method for preparing a porous solid electrolyte according to any one of claims 1 to 3, characterized in that: The sintering temperature is 500℃~1700℃.

6. A porous solid electrolyte, characterized in that The porous solid electrolyte is prepared by the preparation method of any one of claims 1 to 5.

7. A method for preparing a solid-state alkali metal battery negative electrode, characterized in that: include: The porous side of the porous solid electrolyte is brought into contact with a molten alkali metal material, thereby inducing the molten alkali metal material to fill the pores in the porous solid electrolyte, thereby forming a composite solid alkali metal battery negative electrode in which the solid electrolyte and the alkali metal material permeate each other; Wherein, the porous solid electrolyte is the porous solid electrolyte according to claim 6.

8. The method for preparing a solid-state alkali metal battery negative electrode according to claim 7, characterized in that: The temperature of the alkali metal material in the molten state is 150°C to 500°C.

9. A porous solid electrolyte negative electrode, characterized in that The solid-state alkali metal battery negative electrode is prepared by the preparation method of the solid-state alkali metal battery negative electrode according to claim 7 or 8.

10. A solid-state alkali metal battery, characterized in that: The negative electrode is the porous solid electrolyte negative electrode according to claim 9.

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