Low-melting-point iodide-modified lithium composite LATP solid electrolyte, and preparation method and application thereof
By loading low-melting-point iodides onto the LATP surface and reacting them with lithium metal to generate lithium alloys and lithium iodide, the problems of poor interfacial wettability and lithium dendrite growth in LATP solid electrolytes are solved, achieving efficient interfacial bonding and battery cycle stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG HAIHUA CO LTD
- Filing Date
- 2026-07-02
- Publication Date
- 2026-07-31
AI Technical Summary
Existing LATP solid electrolytes in lithium batteries suffer from poor interfacial wettability, high interfacial impedance, and easy reduction side reactions of Ti4+ leading to crystal structure destruction and lithium dendrite growth, which affect the cycle stability of lithium batteries.
A method for preparing lithium composite LATP solid electrolyte modified with low-melting-point iodide is adopted. By loading low-melting-point iodide on the surface of LATP and reacting it with lithium metal, lithium alloy and lithium iodide are generated, which strengthens the interfacial bonding, optimizes ion transport, and inhibits lithium dendrite growth.
It significantly reduces interface impedance, improves interface bonding strength, inhibits lithium dendrite growth, ensures battery cycle stability, and meets the needs of large-scale mass production.
Smart Images
Figure CN122494784A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery solid electrolyte technology, and in particular to a low-melting-point iodide-modified lithium composite LATP solid electrolyte, its preparation method, and its application. Background Technology
[0002] Solid-state lithium batteries, due to their high safety and high energy density, have become one of the core development directions of next-generation energy storage technology. Among them, LATP (lithium aluminum titanium phosphate), as a typical oxide solid electrolyte for solid-state lithium batteries, has high room temperature ionic conductivity and chemical stability, and is one of the important candidate materials for solid-state battery electrolytes.
[0003] However, existing LATP solid electrolytes still face the following key technical bottlenecks in practical applications: Firstly, the surface chemistry of LATP solid electrolyte is relatively inert, resulting in extremely poor interfacial wettability with molten lithium. This leads to a large number of voids at the interface, hindering ion transport and causing a sharp increase in interfacial impedance.
[0004] Secondly, when LATP solid electrolyte comes into direct contact with lithium metal, Ti oxidation is likely to occur. 4+ Reduced to Ti 3+ The side reactions can directly destroy the crystal structure of LATP.
[0005] Third, lithium dendrites are easily formed during the lithium metal deposition / stripping process. The continuous growth of lithium dendrites can pierce the electrolyte, causing the battery to short-circuit and fail, making it difficult for the cycle stability of lithium batteries to meet the usage requirements.
[0006] Based on this, a method for modifying the interface of LATP solid electrolytes is provided, which features a simple process flow, good process stability, and low processing cost. This method effectively solves the problems of poor interfacial wettability, high interfacial impedance, and Ti content issues present in existing LATP solid electrolytes. 4+ The problem of easy reduction side reactions leading to crystal structure damage and lithium dendrite growth is the key to promoting the industrialization of lithium metal batteries. Summary of the Invention
[0007] To address the technical problems existing in the prior art, this invention provides a method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte. Through a simple process flow, good process stability, and low processing cost, the method effectively solves the problems of poor interfacial wettability, high interfacial impedance, and Ti... 4+ It is prone to reduction side reactions, which can lead to crystal structure damage and lithium dendrite growth.
[0008] The present invention also provides a low-melting-point iodide-modified lithium composite LATP solid electrolyte prepared by the aforementioned method.
[0009] The present invention also provides the application of the low-melting-point iodide-modified lithium composite LATP solid electrolyte.
[0010] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte includes the following steps: Step S01: Drop-coat the organic solution of low-melting-point iodide onto the surface of LATP solid electrolyte sheet, and dry it to obtain LATP solid electrolyte sheet with iodide-modified layer on surface; Step S02: In an inert atmosphere, heat the LATP solid electrolyte sheet with an iodide-modified layer on its surface to 220-250°C and keep it at that temperature; then place lithium metal on the surface of the iodide-modified layer and continue to keep it at 220-250°C until the lithium metal is completely melted and spread on the surface of the iodide-modified layer, thus obtaining a low-melting-point iodide-modified lithium composite LATP solid electrolyte.
[0011] Preferably, in step S01, the melting point of the low-melting-point iodide is below 250°C.
[0012] Preferably, in step S01, the low-melting-point iodide is one of the following: antimony triiodide, tin tetraiodide, or gallium triiodide.
[0013] Preferably, in step S01, the concentration of the low-melting-point iodide in the organic solution of the low-melting-point iodide is 0.01-0.05 mol / L.
[0014] Preferably, in step S01, the loading of low-melting-point iodide on the surface of the LATP solid electrolyte sheet is controlled to be (1.76-4.43)×10. -6 mol / cm 2 .
[0015] Preferably, in step S02, the mass ratio of lithium metal added to LATP solid electrolyte sheet is 1-1.6:100.
[0016] Preferably, in step S02, the holding time after heating the LATP solid electrolyte sheet with the iodide-modified layer on its surface to 220-250°C is 20-40 minutes.
[0017] Preferably, in step S02, after placing lithium metal on the surface of the iodide-modified layer, the holding time at 220-250°C is 20-40 minutes.
[0018] A low-melting-point iodide-modified lithium composite LATP solid electrolyte was prepared using the aforementioned preparation method.
[0019] Application of the aforementioned low-melting-point iodide-modified lithium composite LATP solid electrolyte in the preparation of lithium metal symmetric batteries or lithium metal full batteries.
[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Alloy-reinforced interface bonding lays a solid foundation for stable contact: The low-melting-point iodides used in this invention, including antimony triiodide, tin tetraiodide, and gallium triiodide, all possess excellent lithiophilic properties. When coated onto the LATP surface, they undergo a mild interfacial reaction with molten lithium to generate lithium-antimony, lithium-tin, and lithium-gallium alloys. These alloys can directly act at the interface between LATP and lithium metal, strengthening the interfacial bond through chemical bonding and preventing interfacial delamination caused by volume deformation during cycling. Simultaneously, the alloy's ductility buffers the mechanical stress during lithium deposition / delamination, inhibiting electrolyte crack formation and providing a structurally stable interfacial foundation for subsequent ion transport and long-term cycling. 2) Iodides and their product LiI optimize ion transport and significantly reduce interfacial impedance: This invention optimizes ion transport using iodides and their product LiI, significantly reducing interfacial impedance. On one hand, lithium iodide (LiI), formed by the reaction of iodides with molten lithium, possesses an extremely low lithium-ion diffusion barrier and exhibits superior ionic conductivity compared to most halide electrolytes. It can serve as a "bridge" for ion transport, efficiently connecting the ion transport paths of LATP and lithium metal, thus solving the problem of ion transport obstruction caused by porosity and grain boundary defects at traditional interfaces. On the other hand, LiI actively fills the tiny gaps and interfacial gaps on the LATP surface, while simultaneously helping the iodide-modified layer maintain structural coherence, reducing interfacial resistance during lithium-ion migration. Furthermore, LiI can optimize and reconstruct the unreasonable lattice structure of the LATP surface, introducing glassy phase components, expanding lithium-ion transport channels, further reducing the overall impedance of the symmetrical cell, and improving ion transport efficiency.
[0021] 3) The synergistic effect of iodides and alloys inhibits lithium dendrite growth and ensures cycle safety: The iodide-formed modification layer used in this invention can uniformly disperse the interfacial current density and reduce lithium dendrite nucleation sites. It forms a synergistic protective system with the alloy generated from the reaction of molten lithium and LiI: the alloy, through its ductility, buffers interfacial volume deformation, preventing localized stress concentration that could induce lithium dendrite growth; LiI guides uniform lithium ion deposition, preventing localized aggregation that could lead to rapid dendrite growth. Furthermore, the resulting interfacial layer possesses mechanical buffering capabilities, physically preventing dendrites from penetrating the LATP (lithium atomized phospholipid). Both maintain structural stability during lithium stripping. LiI can also self-repair damaged interfaces through ion migration, ensuring long-term cycling safety. Simultaneously, this modification layer, along with the alloy and LiI, constitutes a SEI-like stable protective film, physically isolating LATP from lithium metal and suppressing Ti through the stable lattice of LiI.4+ The reduction of side reactions prevents electrolyte structure collapse and lithium loss, and the protective film is reversibly repairable. In addition, the moisture-proof properties of the iodide-modified layer and the enhanced resistance of LiI to water erosion of LATP significantly improve the performance stability of the electrolyte in large-scale preparation and use, making it suitable for mass production requirements and facilitating the large-scale application of lithium metal batteries.
[0022] 4) The advantages of low melting point and low-temperature reaction, while taking into account process feasibility and interface compatibility: The antimony triiodide, tin tetraiodide, and gallium triiodide used in this invention are all low-melting-point iodides, enabling the LATP surface modification and lithium metal composite process to be completed at a low temperature of 220-250℃. Compared with the traditional high-temperature sintering modification process, this has significant advantages: First, the low-temperature environment can avoid lattice distortion or component volatilization of LATP due to high temperature, ensuring the ionic conductivity and structural integrity of the electrolyte itself; second, the low-temperature reaction conditions are mild, avoiding excessive lithium metal loss or violent side reactions with LATP, while reducing equipment energy consumption and process complexity, adapting to the needs of large-scale mass production; third, low-melting-point iodides are easily soluble in conventional organic solvents, and uniform loading can be achieved through a simple drop-coating method, solving the problems of uneven coating and cumbersome process of traditional modification layers, further improving production efficiency and product consistency. Attached Figure Description
[0023] Figure 1 The image shows the XRD pattern of the LATP solid electrolyte sheet with a surface-loaded antimony iodide modified layer obtained in Example 1.
[0024] Figure 2 This is a cross-sectional SEM image of the LATP solid electrolyte sheet with a surface-loaded antimony iodide modified layer obtained in Example 1.
[0025] Figure 3 This is a mapping image of the LATP solid electrolyte sheet with a surface-loaded antimony iodide modified layer obtained in Example 1.
[0026] Figure 4 Impedance diagrams of the low-melting-point iodide-modified lithium composite LATP solid electrolyte of Example 1 and the antimony acetate-modified lithium composite LATP solid electrolyte of Comparative Example 1.
[0027] Figure 5 The lithium symmetric battery performance diagrams are for the low-melting-point iodide-modified lithium composite LATP solid electrolyte of Example 1 and the antimony acetate-modified lithium composite LATP solid electrolyte of Comparative Example 1.
[0028] Figure 6 The graph shows the cycle performance of solid lithium metal full cells using the low-melting-point iodide-modified lithium composite LATP solid electrolyte of Example 1 and the antimony acetate-modified lithium composite LATP solid electrolyte of Comparative Example 1. Detailed Implementation
[0029] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0030] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0031] In a first aspect, embodiments of the present invention provide a method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte, comprising the following steps: Step S01: Using the drop-coating method, an organic solution of low-melting-point iodide is drop-coated onto the surface of the LATP solid electrolyte sheet, and then dried to obtain an LATP solid electrolyte sheet with an iodide-modified layer on the surface. Step S02: In an inert atmosphere, heat the LATP solid electrolyte sheet with an iodide-modified layer on its surface to 220-250°C and keep it at that temperature; then place lithium metal on the surface of the iodide-modified layer and continue to keep it at 220-250°C until the lithium metal is completely melted and spread on the surface of the iodide-modified layer, thus obtaining a low-melting-point iodide-modified lithium composite LATP solid electrolyte.
[0032] In this embodiment of the invention, during the subsequent preparation of the lithium metal symmetric battery, in step S01, an organic solution of low-melting-point iodide is drop-coated onto one side of the LATP solid electrolyte sheet and dried. Then, using the same method, the organic solution of low-melting-point iodide is drop-coated onto the other side of the LATP solid electrolyte sheet and dried, resulting in an LATP solid electrolyte sheet with iodide-modified layers on both sides. In step S02, using the same method, lithium metal is completely melted and spread onto the iodide-modified layers on the surfaces of the LATP solid electrolyte sheets on each side, resulting in an LATP solid electrolyte with low-melting-point iodide-modified lithium on both sides.
[0033] In this embodiment of the invention, during the subsequent preparation of the solid-state lithium metal battery, in step S01, an organic solution of low-melting-point iodide is drop-coated onto one side of the LATP solid electrolyte sheet and dried to obtain an LATP solid electrolyte sheet with an iodide-modified layer on one side. In step S02, lithium metal is completely melted and spread onto the surface of the iodide-modified layer to obtain an LATP solid electrolyte with low-melting-point iodide-modified lithium on one side.
[0034] The preparation method of the low-melting-point iodide-modified lithium composite LATP solid electrolyte of this invention directly modifies the electrolyte, enabling one-step integrated molding of the electrolyte and the metal anode. It utilizes an alloy phase and lithium iodide to bond the electrolyte and the metal anode into a single unit. Simultaneously, the alloy and lithium iodide formed at the electrolyte-lithium metal interface enhance the interfacial bonding performance between the electrolyte and lithium metal phases, further improving the cycle stability of the battery. Specifically, leveraging the lithiophilic properties of low-melting-point iodides, after being coated onto the LATP surface, a mild interfacial reaction occurs with molten lithium to generate a lithium alloy. This alloy can directly act at the LATP-lithium metal interface, strengthening the interfacial bonding strength through chemical bonding and preventing interfacial delamination caused by volume deformation during cycling. Simultaneously, the ductility of the alloy itself buffers the mechanical stress during lithium deposition / delamination, inhibiting electrolyte crack formation and providing a structurally stable interfacial foundation for subsequent ion transport and long-term cycling. Furthermore, the iodide and its product LiI further optimize ion transport and significantly reduce interfacial impedance. Moreover, the synergistic effect of the iodide and alloy inhibits lithium dendrite growth, ensuring cycle safety. The aforementioned technical methods work together synergistically to effectively solve the problems of poor interfacial wettability, high interfacial impedance, and Ti in existing LATP solid electrolytes. 4+ It is prone to reduction side reactions, which can lead to crystal structure damage and lithium dendrite growth.
[0035] Preferably, in step S01, the melting point of the low-melting-point iodide is below 250°C; more preferably, the low-melting-point iodide is one of the following: antimony triiodide, tin tetraiodide, or gallium triiodide.
[0036] Preferably, in step S01, the organic solvent used in the organic solution of the low-melting-point iodide is acetonitrile or N,N-dimethylformamide.
[0037] Preferably, in step S01, the concentration of the low-melting-point iodide in the organic solution of the low-melting-point iodide is 0.01-0.05 mol / L.
[0038] Preferably, in step S01, the loading of low-melting-point iodide on the surface of the LATP solid electrolyte sheet is controlled to be (1.76-4.43)×10. -6 mol / cm 2 .
[0039] Preferably, in step S02, the mass ratio of lithium metal added to LATP solid electrolyte sheet is 1-1.6:100.
[0040] Preferably, in step S02, the LATP solid electrolyte sheet with the iodide-modified layer loaded on its surface is heated to 220-250°C and held at that temperature for 20-40 minutes; after placing lithium metal on the surface of the iodide-modified layer, the temperature is held at 220-250°C for 20-40 minutes.
[0041] Secondly, embodiments of the present invention provide a low-melting-point iodide-modified lithium composite LATP solid electrolyte prepared by the aforementioned method.
[0042] Thirdly, embodiments of the present invention also provide the application of the low-melting-point iodide-modified lithium composite LATP solid electrolyte in the preparation of lithium metal symmetric batteries or lithium metal full batteries.
[0043] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with some specific embodiments.
[0044] Example 1 This embodiment provides a method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte, the specific steps of which are as follows: (1) Weigh antimony triiodide (SbI3, melting point about 170℃) powder and add it to anhydrous acetonitrile. Stir and disperse evenly at room temperature to obtain an antimony triiodide solution with a concentration of 0.01 mol / L. Then, use a pipette to take 200 μL of antimony triiodide solution and pipette along the LATP solid electrolyte sheet (diameter 12 mm, effective area 1.130 cm²). 2 The electrolyte tablets are coated with a 1.0 mm thick layer of antimony triiodide (TTI) by slow and uniform drop-coating from the edge to the center, with the surface polished and the mass controlled by polishing to ensure that the solution evenly covers the surface of the electrolyte tablets without local liquid accumulation. After the drop-coating is completed, the electrolyte tablets are placed in a desiccator and left to dry at room temperature for 24 hours to obtain LATP solid electrolyte tablets with a surface-loaded antimony triiodide modified layer.
[0045] (2) In an argon atmosphere glove box, place the LATP solid electrolyte sheet with antimony triiodide modified layer on the surface prepared in step (1) in a stainless steel crucible with smooth inner wall, ensuring that the electrolyte sheet is in close contact with the bottom of the crucible; place the crucible on a programmed heating stage, set the heating rate to 5℃ / min, heat to 220℃, and hold at that temperature for 30min; then, weigh 4.5mg of lithium metal sheet and place it in the central area of the antimony triiodide modified layer; continue to hold at 220℃ for 40min, during which time the lithium metal is completely melted and evenly spread on the entire surface of the modified layer through the glove box observation window, ensuring that there are no local agglomerates or unwetted areas; after the melting is completed, cool to room temperature to obtain an LATP solid electrolyte with low melting point iodide modified lithium on one side surface, i.e., low melting point iodide modified lithium composite LATP solid electrolyte.
[0046] This embodiment also provides a low-melting-point iodide-modified lithium composite LATP solid electrolyte prepared by the aforementioned method. The XRD and SEM images of this LATP solid electrolyte sheet with an iodide-modified surface are shown below. Figure 1 , Figure 2 As shown, through Figure 1 and Figure 2 We can see the successful modification of the antimony triiodide layer without destroying the structure of the LATP solid electrolyte itself; at the same time, from Figure 3 The mapping diagram of the LATP solid electrolyte sheet with a surface-loaded iodide-modified layer shows an enriched layer of Sb and I, which indirectly proves the existence of the antimony triiodide layer.
[0047] Furthermore, using the same method as steps (1) and (2) above, low-melting-point iodide-modified lithium is coated on the other side of the LATP solid electrolyte with low-melting-point iodide-modified lithium on one side, to obtain an LATP solid electrolyte with low-melting-point iodide-modified lithium coated on both sides.
[0048] Example 2 This embodiment provides a method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte, the specific steps of which are as follows: (1) Weigh tin tetraiodide (SnI4, melting point approximately 237℃), add it to N,N-dimethylformamide (DMF), and stir to disperse evenly at room temperature to obtain a tin tetraiodide solution with a concentration of 0.02 mol / L; then use a pipette to take 150 μL of tin tetraiodide solution and pipette along the LATP solid electrolyte sheet (diameter 12 mm, effective area 1.130 cm²). 2The electrolyte tablets are coated with a 1.0 mm thick layer and the surface is polished. The coating is slow and uniform from the edge to the center by polishing to ensure that the solution evenly covers the surface of the electrolyte tablets without local liquid accumulation. After coating, the electrolyte tablets are placed in a desiccator and dried at room temperature for 24 hours to obtain LATP solid electrolyte tablets with a tin tetraiodide modified layer on the surface.
[0049] (2) In an argon atmosphere glove box, the LATP solid electrolyte sheet with a tin tetraiodide modified layer on the surface prepared in step (1) is placed stably in a stainless steel crucible with a smooth inner wall, ensuring that the electrolyte sheet is in close contact with the bottom of the crucible; the crucible is placed on a programmed heating stage, the heating rate is set to 5℃ / min, the temperature is raised to 250℃, and held at that temperature for 30min; then, 4.0mg of lithium metal sheet is weighed and placed in the central area of the tin tetraiodide modified layer; the temperature is kept at 250℃ for 20min, during which time the lithium metal is completely melted and evenly spread on the entire surface of the modified layer is confirmed through the glove box observation window, ensuring that there are no local agglomerations or unwetted areas; after the melting is completed, the temperature is cooled to room temperature to obtain an LATP solid electrolyte with low-melting-point iodide modified lithium on one side of the surface, namely, low-melting-point iodide modified lithium composite LATP solid electrolyte.
[0050] This embodiment also provides a low-melting-point iodide-modified lithium composite LATP solid electrolyte prepared by the aforementioned method.
[0051] Furthermore, using the same method as steps (1) and (2) above, low-melting-point iodide-modified lithium is coated on the other side of the LATP solid electrolyte with low-melting-point iodide-modified lithium on one side, to obtain an LATP solid electrolyte with low-melting-point iodide-modified lithium coated on both sides.
[0052] Example 3 This embodiment provides a method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte, the specific steps of which are as follows: (1) Weigh gallium triiodide (GaI3, melting point 212℃) powder, add it to anhydrous acetonitrile, and disperse it evenly by stirring at room temperature to obtain a gallium triiodide solution with a concentration of 0.02 mol / L; then use a pipette to take 200 μL of the gallium triiodide solution and pipette it along the LATP solid electrolyte sheet (diameter 12 mm, effective area 1.130 cm²). 2 The electrolyte sheet has a thickness of 1.0 mm and is polished. The mass is controlled by polishing to 292±2 mg. The electrolyte is slowly and evenly dripped from the edge to the center to ensure that the solution evenly covers the surface of the electrolyte sheet without local liquid accumulation. After the dripping is completed, the electrolyte sheet is placed in a desiccator and dried at room temperature for 24 hours to obtain a LATP solid electrolyte sheet with a gallium triiodide modified layer on the surface.
[0053] (2) In an argon atmosphere glove box, the LATP solid electrolyte sheet with a gallium triiodide modified layer on the surface prepared in step (1) is placed stably in a stainless steel crucible with a smooth inner wall to ensure that the electrolyte sheet is in close contact with the bottom of the crucible; the crucible is placed on a programmed heating stage, the heating rate is set to 5℃ / min, the temperature is raised to 230℃, and held at the temperature for 30min; then, 3.0mg of lithium metal sheet is weighed and placed in the central area of the gallium triiodide modified layer; the temperature is maintained at 230℃ for 30min, during which time the lithium metal is completely melted and evenly spread on the entire surface of the modified layer through the observation window of the glove box to ensure that there are no local agglomerations or unwetted areas; after the melting is completed, it is cooled to room temperature to obtain an LATP solid electrolyte with low melting point iodide modified lithium on one side of the surface, namely, low melting point iodide modified lithium composite LATP solid electrolyte.
[0054] This embodiment also provides a low-melting-point iodide-modified lithium composite LATP solid electrolyte prepared by the aforementioned method.
[0055] Furthermore, using the same method as steps (1) and (2) above, low-melting-point iodide-modified lithium is coated on the other side of the LATP solid electrolyte with low-melting-point iodide-modified lithium on one side, to obtain an LATP solid electrolyte with low-melting-point iodide-modified lithium coated on both sides.
[0056] Example 4 This embodiment provides a method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte, the specific steps of which are as follows: (1) Weigh antimony triiodide (SbI3, melting point about 170℃) powder, add it to anhydrous acetonitrile, and stir and disperse it evenly at room temperature to obtain an antimony triiodide solution with a concentration of 0.05 mol / L; then use a pipette to take 100 μL of antimony triiodide solution and pipette it along the LATP solid electrolyte sheet (diameter 12 mm, effective area 1.130 cm²). 2 The electrolyte tablets are coated with a 1.0 mm thick layer of antimony triiodide (TTI) by slow and uniform drop-coating from the edge to the center, with the surface polished and the mass controlled by polishing to ensure that the solution evenly covers the surface of the electrolyte tablets without local liquid accumulation. After the drop-coating is completed, the electrolyte tablets are placed in a desiccator and left to dry at room temperature for 24 hours to obtain LATP solid electrolyte tablets with a surface-loaded antimony triiodide modified layer.
[0057] (2) In an argon atmosphere glove box, place the LATP solid electrolyte sheet with antimony triiodide modified layer prepared in step (1) into a stainless steel crucible with a smooth inner wall, ensuring that the electrolyte sheet is in close contact with the bottom of the crucible; place the crucible on a programmed heating stage, set the heating rate to 5℃ / min, heat to 220℃, and hold at that temperature for 30min; then, weigh 4.5mg of lithium metal sheet and place it in the central area of the antimony triiodide modified layer; keep at 220℃ for 35min, during which time the lithium metal is completely melted and evenly spread on the entire surface of the modified layer through the glove box observation window, ensuring that there are no local agglomerations or unwetted areas; after the heat preservation and melting are completed, cool to room temperature to obtain an LATP solid electrolyte with low melting point iodide modified lithium on one side surface, namely, low melting point iodide modified lithium composite LATP solid electrolyte.
[0058] This embodiment also provides a low-melting-point iodide-modified lithium composite LATP solid electrolyte prepared by the aforementioned method.
[0059] Furthermore, using the same method as steps (1) and (2) above, low-melting-point iodide-modified lithium is coated on the other side of the LATP solid electrolyte with low-melting-point iodide-modified lithium on one side, to obtain an LATP solid electrolyte with low-melting-point iodide-modified lithium coated on both sides.
[0060] Comparative Example 1 This comparative example uses the technical solution of Example 1, except that the low-melting-point iodide is replaced with antimony acetate. The specific steps are as follows: (1) Weigh antimony acetate (C6H9O6Sb, melting point about 131℃) powder, add it to DMF, and stir and disperse it evenly at room temperature to obtain an antimony acetate solution with a concentration of 0.01 mol / L; then use a pipette to take 200 μL of antimony acetate solution and pipette it along the LATP solid electrolyte sheet (diameter 12 mm, effective area 1.130 cm²). 2 The electrolyte tablets were coated with a 1.0 mm thick material. The surface was polished and the quality was controlled by grinding (292±2 mg). The solution was slowly and evenly dripped from the edge to the center to ensure that the solution evenly covered the surface of the electrolyte tablets without local liquid accumulation. After the coating was completed, the electrolyte tablets were placed in a desiccator and dried at room temperature for 24 hours to obtain LATP solid electrolyte tablets with a surface-loaded antimony acetate modified layer.
[0061] (2) In an argon atmosphere glove box, the LATP solid electrolyte sheet with antimony acetate modification layer prepared in step (1) was placed in a stainless steel crucible with a smooth inner wall, ensuring that the electrolyte sheet was in close contact with the bottom of the crucible; the crucible was placed on a programmed heating stage, the heating rate was set to 5℃ / min, the temperature was raised to 220℃, and held at that temperature for 30min; then, 4.5mg of lithium metal sheet was weighed and placed in the central area of the antimony acetate modification layer; the temperature was maintained at 220℃ for 35min, during which time the lithium metal was completely melted and evenly spread on the entire surface of the modification layer through the glove box observation window, ensuring that there were no local agglomerations or unwetted areas; after the melting was completed, the temperature was cooled to room temperature to obtain the antimony acetate modified lithium composite LATP solid electrolyte of Comparative Example 1.
[0062] Furthermore, using the same method as steps (1) and (2) above, antimony-modified lithium acetate is coated on the other side of the LATP solid electrolyte with antimony-modified lithium acetate on one side, to obtain an LATP solid electrolyte with antimony-modified lithium acetate coated on both sides.
[0063] Comparative Example 2 This comparative example uses the technical solution of Example 1, except that the low-melting-point iodide is replaced with lithium iodide. The specific steps are as follows: (1) Weigh lithium iodide (LiI, melting point about 450℃) powder, add it to anhydrous acetonitrile, and stir and disperse it evenly at room temperature to obtain a lithium iodide solution with a concentration of 0.01 mol / L; then use a pipette to take 200 μL of lithium iodide solution and pipette it along the LATP solid electrolyte sheet (diameter 12 mm, effective area 1.130 cm²). 2 The electrolyte sheet has a thickness of 1.0 mm and its surface is polished. The mass is controlled by polishing (292±2 mg). The electrolyte is slowly and evenly dripped from the edge to the center to ensure that the solution evenly covers the surface of the electrolyte sheet without local liquid accumulation. After the dripping is completed, the electrolyte sheet is placed in a desiccator and dried at room temperature for 24 hours to obtain a LATP solid electrolyte sheet with a lithium iodide modified layer on the surface.
[0064] (2) In an argon atmosphere glove box, the LATP solid electrolyte sheet with lithium iodide modified layer prepared in step (1) was placed in a stainless steel crucible with a smooth inner wall, ensuring that the electrolyte sheet was in close contact with the bottom of the crucible; the crucible was placed on a programmed heating stage, the heating rate was set to 5℃ / min, the temperature was raised to 220℃, and held at that temperature for 30min; then, 4.5mg of lithium metal sheet was weighed and placed in the central area of the lithium iodide modified layer; the temperature was maintained at 220℃ for 35min, during which time the lithium metal was completely melted and evenly spread on the entire surface of the modified layer through the glove box observation window, ensuring that there were no local agglomerations or unwetted areas; after the melting was completed, the temperature was cooled to room temperature to obtain the lithium iodide modified lithium composite LATP solid electrolyte of Comparative Example 2.
[0065] Furthermore, using the same method as steps (1) and (2) above, lithium iodide-modified lithium is coated on the other side of the LATP solid electrolyte with lithium iodide-modified lithium on one side, to obtain LATP solid electrolyte with lithium iodide-modified lithium coated on both sides.
[0066] Lithium metal symmetric batteries were assembled and tested using the two-sided composite LATP solid electrolytes of Examples 1-4 and Comparative Examples 1-2, respectively, and lithium metal full batteries were assembled and tested using the single-sided composite LATP solid electrolytes of Examples 1-4 and Comparative Examples 1-2, respectively. Specifically: (1) Symmetrical battery assembly: In an argon glove box (oxygen content < 0.01 ppm, water content < 0.01 ppm), a double-sided composite LATP solid electrolyte sheet was loaded into a Swagelok apparatus and tightened to obtain a symmetrical cell. Its impedance and symmetrical cell cycle performance (charge / discharge conditions: 0.5 mAh / cm²) were tested using an electrochemical workstation and a Newway battery testing system. 2 ).
[0067] (2) Full battery assembly: The ternary lithium positive electrode sheet was cut into discs suitable for button batteries and vacuum dried at 120℃ for 8 hours to remove water. Then, the discs were stacked in the following order: button battery positive electrode shell, electrolyte-wetted ternary lithium positive electrode sheet, single-sided composite LATP solid electrolyte sheet, spring sheet, and negative electrode cap. The cells were then sealed using a button battery sealing machine at 8MPa pressure for 15 seconds to obtain a full battery. For testing, the cells were first allowed to stand for 8 hours to allow for full interface wetting. The internal resistance at 1kHz was measured using AC impedance spectroscopy. Charge-discharge tests (0.5C) were conducted at room temperature, with a charge-discharge voltage range of 2.8-4.3V. The electrolyte composition was 1.0M LiPF6, and the solvent was ethylene carbonate EC: methyl ethyl carbonate EMC: dimethyl carbonate DMC = 3:5:2 (volume ratio).
[0068] The specific test results are shown in the table below:
[0069] As can be seen from the data in the table, Examples 1-4 of the present invention, which modify LATP with antimony triiodide, tin tetraiodide or gallium triiodide, show significant advantages in terms of interface performance and cycle stability compared with Comparative Examples 1-2.
[0070] Combination Figure 4 As shown, the interface impedance data indicates that Example 1 has an interface impedance of 155Ω, while Comparative Example 1 has an interface impedance of 251Ω. The other examples are also significantly superior to the comparative example. This difference stems primarily from the presence of antimony and tin in the low-melting-point iodides. 、Gallium's excellent lithiophilic properties allow it to undergo a mild interfacial reaction with molten lithium, forming corresponding lithium alloys and lithium iodide (LiI). On one hand, the lithium alloy strengthens the interfacial bond between LATP and lithium metal through chemical bonding, while its ductility buffers volume deformation and prevents interfacial delamination. On the other hand, the lithiophilic interface formed by the reaction transforms the original inert surface of LATP into a continuous lithiophilic interface, changing the "point contact" between molten lithium and LATP into a uniform and continuous surface contact, eliminating interfacial voids, and laying the structural foundation for low impedance transmission and long-term cycling stability.
[0071] Combination Figure 5 As shown, the initial overpotential of Example 1 was only 63 mV, lower than the 91 mV overpotential level of Comparative Example 1, and the other examples were also superior to the comparative example. The key to the lower overpotential of the examples lies in the crucial role of LiI generated by the iodide reaction as an "ion transport bridge": LiI itself has an extremely low lithium-ion diffusion barrier and excellent ionic conductivity, which not only efficiently connects the ion transport path between LATP and lithium metal, but also actively fills the tiny defects and interfacial gaps on the LATP surface, while introducing glass phase components to expand the lithium-ion transport channel, significantly reducing the interfacial resistance during ion migration. This technical advantage is directly reflected in the cycling stability: the examples all achieved a low overpotential of 0.5 mAh / cm². 2 Under the given conditions, the cycle time exceeded 1100 hours, and the capacity retention of the entire cell was greater than 88%. In contrast, Comparative Example 1 only had a cycle time of 223 hours. The core reason for this was the lack of LiI formation, which prevented effective dispersion of the interfacial current density, suppression of lithium dendrite nucleation and growth, and the lack of interfacial strengthening, leading to easy interfacial delamination and cracking during cycling. Comparative Example 2 had a cycle time of only 383 hours. Although LiI interface optimization was present, the ion transport optimization of LiI and the synergistic protective effect of the lithium alloy were not fully utilized, making it difficult to balance low impedance transport and long-term structural stability, ultimately limiting the cycle performance. Meanwhile, combined with... Figure 6 As can be seen from the charge-discharge cycle performance graph of the lithium metal full battery, when cycled 100 times at 0.5C, the capacity retention rate of Example 1 is significantly better than that of Comparative Example 1, demonstrating excellent charge-discharge cycle performance.
[0072] Unless otherwise stated, all percentages used in this invention are mass percentages.
[0073] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a low-melting-point iodide-modified lithium composite LATP solid electrolyte, characterized in that, Includes the following steps: Step S01: Drop-coat the organic solution of low-melting-point iodide onto the surface of LATP solid electrolyte sheet, and dry it to obtain LATP solid electrolyte sheet with iodide-modified layer on surface; Step S02: In an inert atmosphere, heat the LATP solid electrolyte sheet with an iodide-modified layer on its surface to 220-250°C and keep it at that temperature; then place lithium metal on the surface of the iodide-modified layer and continue to keep it at 220-250°C until the lithium metal is completely melted and spread on the surface of the iodide-modified layer, thus obtaining a low-melting-point iodide-modified lithium composite LATP solid electrolyte.
2. The method for preparing the low-melting-point iodide-modified lithium composite LATP solid electrolyte according to claim 1, characterized in that, In step S01, the melting point of the low-melting-point iodide is below 250°C.
3. The method for preparing the low-melting-point iodide-modified lithium composite LATP solid electrolyte according to claim 1, characterized in that, In step S01, the low-melting-point iodide is one of the following: antimony triiodide, tin tetraiodide, or gallium triiodide.
4. The method for preparing the low-melting-point iodide-modified lithium composite LATP solid electrolyte according to claim 1, characterized in that, In step S01, the concentration of the low-melting-point iodide in the organic solution is 0.01-0.05 mol / L.
5. The method for preparing the low-melting-point iodide-modified lithium composite LATP solid electrolyte according to claim 1, characterized in that, In step S01, the loading of low-melting-point iodide on the surface of the LATP solid electrolyte sheet is controlled to be (1.76-4.43)×10. -6 mol / cm 2 .
6. The method for preparing the low-melting-point iodide-modified lithium composite LATP solid electrolyte according to claim 1, characterized in that, In step S02, the mass ratio of lithium metal added to LATP solid electrolyte sheet is 1-1.6:
100.
7. The method for preparing the low-melting-point iodide-modified lithium composite LATP solid electrolyte according to claim 1, characterized in that, In step S02, the LATP solid electrolyte sheet with an iodide-modified surface is heated to 220-250°C and held for 20-40 minutes.
8. The method for preparing the low-melting-point iodide-modified lithium composite LATP solid electrolyte according to claim 1, characterized in that, In step S02, after placing lithium metal on the surface of the iodide-modified layer, the holding time at 220-250°C is 20-40 minutes.
9. A low-melting-point iodide-modified lithium composite LATP solid electrolyte, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. The application of the low-melting-point iodide-modified lithium composite LATP solid electrolyte as described in claim 9 in the preparation of lithium metal symmetric batteries or lithium metal full batteries.