Inorganic solid electrolyte interface modification method and application thereof

Abstract

This invention provides a method for modifying the interface of an inorganic solid electrolyte and its application, belonging to the field of lithium battery application technology. This modification method involves preparing a uniformly dispersed mixed solution of polyethylene oxide, lithium salt, and filler, and using this mixed solution to modify the surface of the inorganic solid electrolyte, thereby obtaining a lithium-stable inorganic solid electrolyte. The addition of filler lowers the lithium-ion transport barrier in the modified layer, increasing its lithium-ion conductivity; it also effectively increases the Young's modulus of the interface modification layer, enhancing its ability to suppress lithium dendrite growth; and it lowers the surface potential to mitigate the space charge layer effect, promoting uniform lithium-ion deposition. Under the combined effect of these factors, the lithium stability of the inorganic solid electrolyte is significantly improved. The inorganic solid electrolyte modified by the interface modification method provided by this invention exhibits higher limiting current density and cycle life, demonstrating better interface stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery application technology, specifically relating to an inorganic solid electrolyte interface modification method and its application. Background Technology

[0002] In recent years, due to the low safety and low energy density of liquid lithium-ion batteries, all-solid-state lithium batteries, which use solid electrolytes and lithium metal as the negative electrode, have received widespread attention due to their high safety and high energy density. Inorganic solid electrolytes, as solid electrolyte materials with high mechanical strength, high ionic conductivity, and a wide electrochemical window, have great application potential compared to other solid electrolytes. However, due to the extremely low electrochemical potential of lithium metal negative electrodes, currently used inorganic solid electrolyte materials are reduced by lithium metal upon contact, leading to interfacial instability. Furthermore, the contact interface between inorganic solid electrolytes and lithium metal is a solid-solid contact, which is an insufficient contact. This insufficient contact leads to severe interfacial polarization. These problems seriously affect the performance of all-solid-state lithium batteries and limit the application of inorganic solid electrolytes. Summary of the Invention

[0003] The purpose of this invention is to address the above-mentioned shortcomings of the prior art by providing an inorganic solid electrolyte interface modification method and its application.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: The first objective of this invention is to provide a method for preparing an inorganic solid electrolyte, comprising the following steps: Step S1: Weigh out polyethylene oxide, lithium salt and filler in appropriate proportions, disperse the raw materials in a solvent, and mix the raw materials evenly by heating and stirring; the filler includes lithium zirconium iron phosphate or lithium zirconium phosphate. Step S2: The mixed solution prepared in step S1 is applied to the surface of the inorganic solid electrolyte by drop coating, spray coating or spin coating. Step S3: The solvent in the modified layer of the modified inorganic solid electrolyte obtained in step S2 is removed by heating and drying, thereby obtaining an inorganic solid electrolyte that is stable to the lithium metal anode.

[0005] Furthermore, the molecular weight of the polyethylene oxide is 5,000 to 1,000,000.

[0006] Furthermore, the lithium salt to polyethylene oxide lithium-oxygen ratio is 1:(8~20).

[0007] Furthermore, the lithium salt is any one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonate)imine, lithium perchlorate, and lithium tetrafluoroborate.

[0008] Furthermore, the mass ratio of the functional filler to the polyethylene oxide is 1:(0.5~5).

[0009] Furthermore, the inorganic solid electrolyte body includes any one of lithium titanium aluminum phosphate inorganic solid electrolyte, NASICON-type solid electrolyte having the same structure as lithium titanium aluminum phosphate, lithium lanthanum zirconate inorganic solid electrolyte, and garnet-type solid electrolyte having the same structure as lithium lanthanum zirconate.

[0010] Furthermore, in step S1, the solvent is any one of acetonitrile, anisole, chloroform, dichloroethane, and dimethylformamide.

[0011] Furthermore, in step S2, the thickness of the coating on the surface of the inorganic solid electrolyte is 10~60μm.

[0012] Furthermore, in step S3, the drying temperature is 50~120℃.

[0013] A second objective of this invention is to provide an inorganic solid electrolyte with an interface modification layer on its surface, characterized in that it is prepared using the aforementioned inorganic solid electrolyte interface modification method.

[0014] A third objective of this invention is to provide the application of the aforementioned inorganic solid electrolyte with an interface modification layer on its surface in an all-solid-state battery, wherein the interface modification layer is located between the negative electrode and the inorganic solid electrolyte layer.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention provides a method for modifying the interface of an inorganic solid electrolyte, comprising: S1, weighing polyethylene oxide, lithium salt and filler in appropriate proportions, dispersing the raw materials in a solvent, and mixing the raw materials uniformly by heating and stirring; the functional filler includes lithium zirconium iron phosphate or lithium zirconium phosphate; S2, attaching the mixed solution prepared in S1 to the surface of the inorganic solid electrolyte body by drop coating, spraying or spin coating; S3, removing the solvent in the modified layer of the modified inorganic solid electrolyte obtained in S2 by heating and drying, thereby obtaining an inorganic solid electrolyte with stability to lithium metal. By using an interface modification material composed of polyethylene oxide, lithium salt and filler to modify the interface between the inorganic solid electrolyte body and the lithium metal anode, the direct contact between the inorganic solid electrolyte body and the lithium metal anode is isolated, thereby inhibiting the degradation of the inorganic solid electrolyte body, enhancing the lithium ion transport capacity of the polymer matrix, and reducing the interface impedance.

[0016] (2) The interface modification method provided by the present invention modifies the surface of the inorganic solid electrolyte by preparing a uniformly dispersed mixed solution, thereby obtaining a uniform and tightly bonded modified layer and effectively improving interfacial contact. The addition of filler reduces the lithium-ion transport barrier in the modified layer, increasing its lithium-ion conductivity. Simultaneously, the addition of functional filler effectively increases the Young's modulus of the interface modified layer, enhancing its ability to suppress lithium dendrite growth. It also reduces the surface potential to mitigate the space charge layer effect, further promoting lithium-ion deposition. Furthermore, the contact between the functional filler and the lithium metal anode can generate an interface layer rich in lithium phosphide and lithium zirconate in situ, improving interface stability.

[0017] (3) The present invention provides an inorganic solid electrolyte with an interface modification layer on its surface, which can effectively improve the interfacial instability of the inorganic solid electrolyte. The limiting current density and cycle life of the modified inorganic solid electrolyte are significantly improved. The degradation of the inorganic solid electrolyte when in contact with the lithium metal anode is effectively suppressed.

[0018] (4) The preparation method provided by the present invention is simple, low in cost, suitable for industrial production, and has great application potential. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the inorganic solid electrolyte with an interface modification layer on its surface, as shown in the present invention. Figure 2 This is a cross-sectional SEM image of the modified inorganic solid electrolyte sheet obtained in Example 1 of the present invention; Figure 3 The image shows the XRD pattern of the modified inorganic solid electrolyte sheet obtained in Example 1 of this invention. Figure 4 The modified inorganic solid electrolyte sheet prepared in Example 1 of this invention, the unmodified inorganic solid electrolyte sheet, and the modified inorganic solid electrolyte sheet prepared in Comparative Example 1 were compared at 0.20 mA cm⁻¹. -2 Comparison of battery long-cycle test results under current density; Figure 5 This is a cross-sectional SEM image of the modified inorganic solid electrolyte sheet obtained in Example 1 of the present invention after 1300 hours of battery cycling. Figure 6 This is a cross-sectional SEM image of the unmodified inorganic solid electrolyte sheet in Embodiment 1 of the present invention after battery failure; Figure 7a The results are from first-principles calculations of the lithium-ion migration barrier in Example 1. Figure 7b The results are first-principles calculations of the migration barrier of lithium ions in Comparative Example 1. Figure 8 The results of Young's modulus tests for the modified layers in Embodiment 1 and Comparative Example 1 of the present invention; Figure 9 The results are the surface potential test results of the modified layer in Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] like Figure 1 The diagram shown is a schematic diagram of the inorganic solid electrolyte with an interface modification layer on its surface according to the present invention. The interface modification layer is located between the negative electrode and the inorganic solid electrolyte layer.

[0022] Example 1 (1) Weigh 0.27g of polyethylene oxide (M w = 600000), 0.09g of lithium imine bis(trifluoromethanesulfonate) and 0.24g of lithium zirconium iron phosphate (Li 1.05 Fe 0.05 Zr 1.95 (PO4)3), the weighed raw material was dissolved in 7 mL of anhydrous acetonitrile solution and stirred at 60 °C for 24 h to obtain a homogeneous modified solution.

[0023] (2) Take 50 μL of the modification solution and add it dropwise to lithium titanium aluminum phosphate (Li 1.4 Al 0.4 Ti 1.6 (PO4)3) Inorganic solid electrolyte surface.

[0024] (3) The modified lithium titanium aluminum phosphate solution was placed in an oven at 60°C and dried for 4 hours, and then placed in a vacuum oven at 60°C and dried under vacuum for 12 hours to obtain the modified lithium titanium aluminum phosphate inorganic solid electrolyte.

[0025] like Figure 2 The image shown is a cross-sectional SEM image of the modified inorganic solid electrolyte sheet. The interface modification layer constructed in Example 1 can firmly cover the surface of the electrolyte sheet. There are no pores between the modification layer and the electrolyte. The thickness of the modification layer is 27.8 μm.

[0026] like Figure 3The image shows the XRD pattern of the modified inorganic solid electrolyte sheet. Its phase composition exhibits characteristic peaks of LATP (lithium aluminum titanium phosphate) and LZP (lithium zirconium phosphate), as well as broad polymer peaks, with no other impurity peaks. This indicates that no reaction occurred between the modified layer and LATP, preventing phase degradation.

[0027] Example 2 (1) Weigh 0.27 g of polyethylene oxide, 0.05 g of lithium hexafluorophosphate and 0.24 g of lithium zirconium phosphate (LiZr2(PO4)3), dissolve the weighed raw materials in 10 mL of anhydrous acetonitrile solution, and stir at 60 °C for 24 h to obtain a uniformly mixed modified solution.

[0028] (2) Take 50 μL of the modification solution and add it dropwise to lithium lanthanum zirconate (Li7La3Zr2O). 12 Inorganic solid electrolyte surface.

[0029] (3) The modified lithium lanthanum zirconate solution was placed in an oven at 60°C and dried for 4 hours, and then placed in a vacuum oven at 60°C and dried under vacuum for 12 hours to obtain the modified lithium lanthanum zirconate inorganic solid electrolyte.

[0030] Example 3 (1) Weigh 0.27g of polyethylene oxide, 0.09g of lithium bis(trifluoromethanesulfonate)imide and 0.04g of lithium zirconium iron phosphate (Li 1.05 Fe 0.05 Zr 1.95 (PO4)3), the weighed raw material was dissolved in 7 mL of dimethylformamide solution and stirred at 60 °C for 24 h to obtain a uniformly mixed modified solution.

[0031] (2) Take 50 μL of the modification solution and drop it onto the surface of lithium zirconium phosphate (LiZr2(PO4)3) inorganic solid electrolyte.

[0032] (3) The lithium zirconium phosphate with the added modification solution was placed in an oven at 60°C and dried for 4 hours, and then placed in a vacuum oven at 60°C and vacuum dried for 12 hours to obtain the modified lithium zirconium phosphate inorganic solid electrolyte.

[0033] Comparative Example 1 (1) Weigh 0.27 g of polyethylene oxide and 0.09 g of lithium bis(trifluoromethanesulfonate)imide, dissolve the weighed raw materials in 7 mL of anhydrous acetonitrile solution, and stir at 60 °C for 24 h to obtain a uniformly mixed modified solution.

[0034] (2) Take 50 μL of the modification solution and add it dropwise to lithium titanium aluminum phosphate (Li 1.4 Al 0.4 Ti1.6 (PO4)3) Inorganic solid electrolyte surface.

[0035] (3) The modified lithium titanium aluminum phosphate solution was placed in an oven at 60°C and dried for 4 hours, and then placed in a vacuum oven at 60°C and dried under vacuum for 12 hours to obtain the modified lithium titanium aluminum phosphate inorganic solid electrolyte.

[0036] To better illustrate the excellent electrochemical performance of the inorganic solid electrolyte of the present invention, the applicant conducted the following research: 1. At 0.20 mA cm -2 Long-cycle testing of the battery at current density A CR2032 coin cell was assembled using a sandwich structure of lithium metal sheet-electrolyte sheet-lithium metal sheet, and a 0.20 mA cm⁻¹ electrolyte was used. -2 0.10 mA cm -2 The assembled battery was charged and discharged at 60 °C. After the test, the battery was disassembled and the changes in the electrolyte sheet after cycling were observed using SEM. Figure 4 This indicates that the battery assembled with the unmodified inorganic electrolyte sheet fails rapidly under these test conditions. The battery prepared in Comparative Example 1 fails after 1200 hours of cycling. However, the battery prepared in Example 1 does not show failure after 5000 hours of cycling. This demonstrates that the interface modification layer used in this invention can significantly improve the lithium interface stability of the inorganic solid electrolyte. Furthermore, from... Figure 5 The SEM images show that after 1300 hours of cycling, the electrolyte sheet prepared in Example 1 also exhibited a complete crystal structure, without any signs of degradation or failure. In contrast, Figure 6 The unmodified inorganic electrolyte exhibited numerous cracks and structural damage after 50 cycles. This further demonstrates the excellent interfacial protection provided by the interface modification layer reported in this invention for the inorganic electrolyte.

[0037] 2. The migration barrier of lithium ions The lithium-ion migration barrier of the PEO-modified layer in Comparative Example 1 and the PEO_LZP-modified layer in Example 1 was calculated using first-principles calculations. Figure 7a The calculation results show that the lithium ion migration barrier in the PEO interface modification layer in Comparative Example 1 is 0.95 eV. Figure 7b The results show that after adding the functional filler, the lithium-ion migration barrier in Example 1 is 0.63 eV, indicating that adding the functional filler can effectively reduce the lithium-ion migration barrier of the modified layer. The lithium-ion migration barrier reflects the ease with which lithium ions move within the material. The smaller lithium-ion migration barrier in Example 1 indicates that the interface modification material in Example 1 has higher lithium-ion conductivity and less interfacial polarization.

[0038] 3. Young's modulus test of modified layers of inorganic solid electrolytes The Young's modulus of the inorganic solid electrolyte modified layer was characterized using the AM-FM module of an atomic force microscope. Figure 8 The test results show that the average Young's modulus of the modified layer prepared in Comparative Example 1 is 311.51 MPa. The average Young's modulus of the modified layer prepared in Example 1 is 1.11 GPa. This indicates that the addition of functional fillers can significantly improve the Young's modulus of the interface modified layer. A higher Young's modulus reflects a stronger resistance to lithium dendrite penetration. Therefore, the addition of functional fillers can enhance the ability of the interface modified layer to resist lithium dendrite penetration.

[0039] 4. Surface potential test of the modified layer of inorganic solid electrolyte The Young's modulus of the inorganic solid electrolyte modified layer was characterized using the SKPM module of an atomic force microscope. Figure 9 The test results show that the average surface potential of the modified layer prepared in Comparative Example 1 is 395.25 mV. The average surface potential of the modified layer prepared in Example 1 is -75 mV. This indicates that the addition of functional fillers can significantly reduce the surface potential of the interface modified layer. A lower surface potential reflects a weaker space charge layer effect, which is more conducive to the uniform deposition of lithium ions. Therefore, the addition of functional fillers can reduce the resistance to lithium ion deposition and promote the uniform deposition of lithium ions.

[0040] Example 4 This embodiment provides an all-solid-state battery.

[0041] (1) Preparation of electrolyte sheets. The method reported in Example 1 was used to prepare double-sided modified electrolyte sheets. Plate.

[0042] (2) Preparation of the positive electrode sheet. LiFePO4, LiTFSI, PVDF and conductive carbon black were mixed in a ratio of 7: The solution was added to NMP solution in a 1:1:1 ratio and heated to mix thoroughly. The resulting slurry was then coated onto aluminum foil and dried in an oven. Further drying in a vacuum oven yielded the positive electrode sheet. The positive electrode sheet was then cut to the desired size.

[0043] (3) Assembly of all-solid-state batteries. Following a sandwich structure of lithium metal anode-electrolyte-cathode. Assemble all-solid-state batteries.

[0044] For any points not covered above, existing technologies shall apply.

[0045] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for modifying the interface of an inorganic solid electrolyte, characterized in that, Includes the following steps: S1. Weigh out polyethylene oxide, lithium salt and filler in appropriate proportions, disperse the raw materials in a solvent, and mix the raw materials evenly by heating and stirring; the filler includes lithium zirconium iron phosphate or lithium zirconium phosphate. S2. The mixed solution prepared in step S1 is applied to the surface of the inorganic solid electrolyte by drop coating, spray coating or spin coating. S3. The solvent in the modified inorganic solid electrolyte layer obtained in step S2 is removed by heating and drying, thereby obtaining the modified inorganic solid electrolyte.

2. The inorganic solid electrolyte interface modification method as described in claim 1, characterized in that, The molecular weight of the polyethylene oxide is 5,000 to 1,000,000.

3. The inorganic solid electrolyte interface modification method as described in claim 2, characterized in that, The mass ratio of the lithium salt to polyethylene oxide is 1:(8~20).

4. The inorganic solid electrolyte interface modification method as described in claim 3, characterized in that, The lithium salt is any one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonate)imine, lithium perchlorate, and lithium tetrafluoroborate.

5. The inorganic solid electrolyte interface modification method as described in claim 3, characterized in that, The mass ratio of the filler to the polyethylene oxide is 1:(0.5~5).

6. The inorganic solid electrolyte interface modification method as described in claim 1, characterized in that, In step S1, the solvent is any one of acetonitrile, anisole, chloroform, dichloroethane, and dimethylformamide.

7. The inorganic solid electrolyte interface modification method according to any one of claims 1-6, characterized in that, The inorganic solid electrolyte body includes any one of lithium titanium aluminum phosphate inorganic solid electrolyte, NASICON type solid electrolyte with the same structure as lithium titanium aluminum phosphate, lithium lanthanum zirconate inorganic solid electrolyte, and garnet type solid electrolyte with the same structure as lithium lanthanum zirconate.

8. The inorganic solid electrolyte interface modification method as described in claim 7, characterized in that, In step S2, the thickness of the coating on the surface of the inorganic solid electrolyte body is 10~60μm.

9. An inorganic solid electrolyte with an interface modification layer on its surface, characterized in that, It was prepared by the inorganic solid electrolyte interface modification method as described in any one of claims 1-8.

10. The application of the inorganic solid electrolyte with an interface modification layer on its surface as described in claim 9 in an all-solid-state battery, characterized in that, The interface modification layer is located between the negative electrode and the inorganic solid electrolyte layer.

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