LiTFSI coated Li6PS5Cl composite material for all-solid-state lithium metal battery and preparation method of LiTFSI coated Li6PS5Cl composite material

Abstract

The invention belongs to the technical field of lithium metal batteries, and particularly relates to a LiTFSI coated Li6PS5Cl composite material for an all-solid-state lithium metal battery and a preparation method of the LiTFSI coated Li6PS5Cl composite material. According to the invention, LiTFSI is uniformly coated on the surfaces of Li6PS5Cl particles through a high-energy ball milling method to form a stable organic-inorganic composite interface layer, so that the interface stability of an electrolyte and an electrode is remarkably improved, the growth and side reaction of lithium dendrites are inhibited, the capacity retention rate of the prepared total battery reaches 86.6% after 300 times of circulation at 0.5 C, and the cycle life of a symmetrical battery exceeds 5000 hours. The method is simple in process, low in cost and suitable for large-scale production of all-solid-state lithium batteries with high energy density and long service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium metal batteries, and specifically relates to a Li6PS5Cl composite material coated with LiTFSI for all-solid-state lithium metal batteries and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] With the continuous growth of global energy demand, lithium batteries, as a highly efficient energy storage technology, have been widely used in electric vehicles, renewable energy storage, and consumer electronics. However, existing liquid lithium batteries have safety risks such as electrolyte leakage and fire, which has prompted the development of solid-state lithium batteries. Sulfide solid electrolytes have been widely studied due to their good ionic conductivity, high electrochemical stability, and high energy density, and are considered to be an ideal choice for achieving high-performance all-solid-state lithium batteries. However, sulfide solid electrolytes still face the following key issues, the resolution of which directly affects their feasibility in practical applications.

[0004] (1) The ionic conductivity of sulfide solid electrolytes is still affected by factors such as material thickness and synthesis process. At present, the thickness of most sulfide solid electrolytes is between 0.5 and 1 mm. In order to balance ionic conductivity and electronic conductivity, the proportion of active substances in the positive electrode material is often low, resulting in a relatively low energy density of sulfide all-solid-state lithium batteries, which restricts their application in the field of high energy density batteries. Solving this problem requires improving the ionic conductivity of the electrolyte or improving the energy density by improving the battery design.

[0005] (2) There is a problem of solid-solid contact between the sulfide solid electrolyte and the positive electrode material, which is mainly reflected in the poor interface contact between the electrolyte and the positive electrode. During the charge and discharge process of the battery, the lithium ion transmission channel at the interface is narrow, which easily generates a large interface impedance and affects the cycle stability of the battery. In addition, due to the difference in electrochemical potential energy between the sulfide electrolyte and the positive electrode material, a space charge layer may be generated at the interface, further exacerbating the interface instability. To solve this problem, it is necessary to improve the contact between the electrolyte and the electrode material, reduce the interface impedance, and improve the overall performance of the battery.

[0006] (3) Lithium metal anodes, as the negative electrode material for all-solid-state lithium batteries, have extremely high theoretical capacity. However, they are prone to forming lithium dendrites during use, leading to internal short circuits in the battery and seriously affecting battery safety. In particular, the interfacial stability between the sulfide solid electrolyte and lithium metal is poor, and lithium dendrites may grow at the grain boundaries of the electrolyte and further penetrate the electrolyte, causing battery failure.

[0007] While existing technologies can partially improve interface properties through surface coating or doping, they suffer from complex processes, unstable interface layers, and reduced ionic conductivity. Therefore, effectively inhibiting the growth of lithium dendrites and ensuring the stability of the lithium anode-electrolyte interface remains a key challenge in current sulfide solid-state battery research. Summary of the Invention

[0008] To address the above issues, the present invention provides a LiTFSI-coated Li6PS5Cl composite material for all-solid-state lithium metal batteries and a preparation method thereof. The present invention utilizes high-energy ball milling to coat lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on the surface of a Li6PS5Cl (LPSCl) electrolyte, forming an organic-inorganic interface layer such as LiF. This interface layer not only effectively improves the contact between the electrolyte and the positive electrode and lithium negative electrode, reducing interfacial impedance, but also inhibits the formation of lithium dendrites, thereby improving the overall stability and safety of the battery. Furthermore, full-cell assembly and electrochemical testing demonstrate the effectiveness of the coated LPSCl electrolyte in all-solid-state lithium batteries.

[0009] Specifically, the present invention adopts the following technical solutions:

[0010] In a first aspect of the present invention, a LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery is provided, wherein the composite material comprises Li6PS5Cl particles and a LiTFSI layer uniformly coated on the surface thereof, wherein the mass ratio of the LiTFSI to the Li6PS5Cl is 0.5 to 2:100;

[0011] The LiTFSI layer is partially decomposed after high-energy ball milling to form an organic-inorganic composite interface layer containing LiF.

[0012] Preferably, the organic-inorganic composite interface layer contains Li-F, Li-N and CF bonds, and the thickness of the interface layer is 85 to 105 nm.

[0013] Preferably, the particle size of the composite material is in the range of 5 to 10 μm, which is smaller than the particle size of the original Li6PS5Cl particles.

[0014] Preferably, the ionic conductivity of the composite material is (8-9.6)×10 -4 S cm-1 .

[0015] In a second aspect of the present invention, a method for preparing the above-mentioned LiTFSI-coated Li6PS5Cl composite material for all-solid-state lithium metal batteries is provided, specifically comprising: mixing Li6PS5Cl powder with LiTFSI and performing high-energy ball milling to obtain a Li6PS5Cl composite material (LiTFSI@LPSCl) uniformly coated with LiTFSI.

[0016] Preferably, the high-energy ball milling is carried out in an inert atmosphere, and zirconium oxide balls are selected for the ball milling process, with a ball diameter of 8 to 10 mm and a ball-to-material ratio of 40:1 to 1.5.

[0017] Preferably, the process parameters of the high-energy ball milling include: a ball milling speed of 400 to 600 rpm; and a ball milling time of 10 to 20 h.

[0018] The third aspect of the present invention provides an application of the LiTFSI-coated Li6PS5Cl composite material for all-solid-state lithium metal batteries described in the first aspect in a solid-state battery.

[0019] A fourth aspect of the present invention provides an all-solid-state lithium metal battery, comprising the LiTFSI-coated Li6PS5Cl composite material for the all-solid-state lithium metal battery described in the first aspect as a solid electrolyte layer.

[0020] Preferably, the all-solid-state lithium metal battery further comprises a high-nickel layered oxide as a positive electrode material and a lithium-indium alloy (Li-In) as a negative electrode material.

[0021] Preferably, the high nickel layered oxide positive electrode material is LiNi coated with lithium niobate. 0.8 Co 0.1 Mn 0.1 One of O2 (LNO@NCM811), lithium iron phosphate, NCM622, and lithium cobalt oxide.

[0022] Preferably, the capacity retention rate of the all-solid-state lithium metal battery after 300 cycles at a 0.5C rate is ≥86%.

[0023] The beneficial effects of one or more of the above technical solutions are as follows:

[0024] (1) The LiTFSI-coated Li6PS5Cl composite material for all-solid-state lithium metal batteries prepared by the high-energy ball milling method of the present invention has improved interface stability: LiTFSI decomposes to generate inorganic components such as LiF during the ball milling process, forming a stable SEI layer, inhibiting the growth of lithium dendrites and reducing interface side reactions;

[0025] Cycle life extension: Li / LiTFSI@LPSCl / Li symmetric battery at 0.1 mA cm -2 The overpotential increase is less than 10% when the cycle exceeds 5000 hours;

[0026] High capacity retention: The capacity retention of the full battery (LNO@NCM811 / LiTFSI@LPSCl / Li-In) is ≥86% after 300 cycles at 0.5C.

[0027] (2) The present invention utilizes the partial decomposition of LiTFSI during high-energy ball milling to generate an organic-inorganic composite interface layer containing LiF (containing Li-F, Li-N, and CF bonds). This interface layer can significantly improve the interfacial stability between the electrolyte and the electrode, inhibit lithium dendrite growth and side reactions, and has better effects than wet milling and LiDFOB modification systems:

[0028] After decomposition, LiDFOB (lithium difluorooxalatoborate) may form an interfacial layer containing boron compounds and a small amount of LiF. Boron-based compounds (such as LiBO2) have low ionic conductivity, and the interfacial layer formed may not be as dense and stable as LiF, which will lead to: increased interfacial impedance: the boron-based interfacial layer has a greater barrier to lithium ion transport, and the boron-based compound's ability to inhibit dendrites is weakened;

[0029] In the wet grinding process, LiTFSI is coated in the form of a solution, with a low degree of decomposition, mainly forming an organic coating layer. The amount of inorganic components (such as LiF) generated is small, which will lead to insufficient density of the interface layer, weak mechanical strength, and reduced ability to inhibit dendrites. In addition, residual solvent (xylene) may increase the risk of interfacial side reactions and reduce long-term stability.

[0030] (3) The present invention takes into account both particle size control and interface modification through one-step dry ball milling, which is low-cost and easy to mass-produce, providing a reliable technical path for the commercialization of high-energy-density, long-life all-solid-state lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 SEM images of the composite materials prepared in Examples 1 to 3 of the present invention and unmodified LPSCl;

[0032] Figure 2 This is the EDS spectrum of the composite material prepared in Example 2 of the present invention;

[0033] Figure 3 The X-ray diffraction pattern (XRD) of the composite material prepared in Example 2 of the present invention;

[0034] Figure 4 This is an X-ray photoelectron spectroscopy (XPS) of the composite material prepared in Example 2 of the present invention;

[0035] Figure 5 EIS graphs of the blocked batteries assembled in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0036] Figure 6 Nyquist plots of symmetrical batteries assembled in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0037] Figure 7 Symmetrical cells assembled from Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 were tested at 0.1 mA cm -2 Voltage distribution diagram of the lower cycle time;

[0038] Figure 8 Graphs showing critical current densities of symmetrical batteries assembled in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0039] Figure 9 The charge and discharge curves of the all-solid-state lithium metal batteries assembled in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 at 0.5C are shown;

[0040] Figure 10 The cycle performance diagram of the all-solid-state lithium metal batteries assembled in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 at 0.5C;

[0041] Figure 11 The all-solid-state lithium metal batteries assembled in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 were tested at 0.05 mV s -1 The CV curve diagram below. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0043] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0044] Example 1: This example provides a LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery, comprising the following steps:

[0045] 1 g of LPSCl powder was mixed with 0.005 g of LiTFSI and ball-milled at 500 rpm for 15 h under argon protection to obtain LiTFSI@LPSCl composite material (LiTFSI0.5@LPSCl).

[0046] Example 2: This example provides a LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery, comprising the following steps:

[0047] 1 g of LPSCl powder was mixed with 0.01 g of LiTFSI and ball-milled at 500 rpm for 15 h under argon protection to obtain LiTFSI@LPSCl composite material (LiTFSI@LPSCl).

[0048] Example 3: This example provides a LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery, comprising the following steps:

[0049] 1 g of LPSCl powder was mixed with 0.02 g of LiTFSI and ball milled at 500 rpm for 15 h under argon protection to obtain LiTFSI@LPSCl composite material (LiTFSI2@LPSCl).

[0050] Example 4: This example performs structural characterization tests on the composite materials prepared in Examples 1 to 3.

[0051] like Figure 1 As shown, Figure 1 Figures a through d show SEM images (scale: 10 μm) of LPSCl, LiTFSI0.5@LPSCl, LiTFSI@LPSCl, and LiTFSI2@LPSCl, respectively. The images show that the particle size of LiTFSI@LPSCl samples at all ratios is smaller than that of the original LPSCl. This can be attributed to the high-energy ball milling during the synthesis process, which breaks up the electrolyte particles. The SEM images also show that the particle size of the coated samples decreases as the LiTFSI ratio increases.

[0052] like Figure 2 As shown, the high-magnification morphology characterization and EDS spectrum results of the LiTFSI@LPSCl particles prepared in Example 2 show that the elements of S, N, and F are evenly distributed, which also verifies that the LiTFSI coating is successful and uniform.

[0053] like Figure 3 As shown in FIG5 , X-ray diffraction (XRD) analysis shows that compared with the original LPSCl, no additional diffraction peaks are observed in the LiTFSI@LPSCl prepared in Example 2. The peaks of LiTFSI@LPSCl and LPSCl are roughly the same, with additional F1s and N 1s peaks, which also verifies the success of the LiTFSI@LPSCl coating.

[0054] like Figure 4As shown, X-ray photoelectron spectroscopy (XPS) further analyzed the changes after LPSCl and LiTFSI coating. The C1s spectrum showed that compared with the original LPSCl particles, the LiTFSI@LPSCl prepared in Example 2 had peaks at 285.8eV and 292.8eV, which can be attributed to -CF3 and CS signals, respectively. These peaks are mainly related to LiTFSI.

[0055] S2p analysis showed that the S2p signal was mainly composed of PS4 before and after high-energy ball milling. 3- The signal (161.3 eV) and the signal (160.3 eV) of Li2S are composed of the same signal, and there is no significant change, which proves the stability of LPSCl during the ball milling process. 3- In addition to the Li2S and S2p signals, new S2p double peaks were observed, located at 166.7eV and 168.8eV, corresponding to SO3 2- and SO4 2- These additional S2p peaks are attributed to -SO2CF3 in LiTFSI.

[0056] Analysis of the F1s results also revealed strong organic fluoride signals in LiTFSI@LPSCl. Weaker Li-F signals were also observed, originating from LiTFSI itself and its decomposition products. No F signals were detected in the original LPSCl. These results demonstrate that the high-energy ball milling method for coating LiTFSI successfully achieved uniform coating of LPSCl.

[0057] Comparative Example 1:

[0058] The difference between this comparative example and Example 2 is that in this comparative example, only the type of lithium salt is changed. Specifically, 0.01 g of lithium difluorooxalatoborate (LiDFOB) is used to synthesize the LiDFOB@LPSCl composite material by high-energy ball milling; the contents of other components and the preparation method are consistent with those in Example 2.

[0059] Comparative Example 2:

[0060] This comparative example differs from Example 2 in that the composite material was prepared using a traditional wet milling method. The specific preparation method is as follows: xylene was used as the wet milling medium to reduce the particle size of the LPSC. Simultaneously, a 1 wt% LiTFSI-IBB solution was added. Under argon protection, the mixture was ball-milled at 500 rpm for 15 hours to uniformly coat the refined LPSC surface with LiTFSI. After coating, the composite material was vacuum-dried at 60°C for 24 hours (under a high-purity argon atmosphere) to obtain LiTFSI@LPSCl prepared by the wet milling method.

[0061] Experimental Example 1: This example assembled and tested the performance of the blocked battery using unmodified LPSCl, Examples 1 to 3, and Comparative Examples 1 to 2.

[0062] Experimental procedure: 150 mg of unmodified LPSCl, the materials prepared in Examples 1-3, and Comparative Examples 1-2 were weighed separately. Two indium sheets with a diameter of 8 mm and a thickness of 0.1 mm were used to prepare a symmetrical blocked cell. The blocked cell was then electrochemically tested using an electrochemical workstation.

[0063] like Figure 5 As shown in Figure 2, the electrochemical impedance spectroscopy (EIS) results show that the ionic conductivity of the original LPSCl is 7.9×10 -3 Scm -1 The ionic conductivity of the composite materials prepared in Example 1 decreases with the increase of LiTFSI dosage. The decrease in ionic conductivity is associated with the decrease in crystallinity. Specifically, the ionic conductivity of LiTFSI0.5@LPSCl, LiTFSI@LPSCl, and LiTFSI2@LPSCl are 9.58×10 -4 , 8.39×10 -4 and 8.14×10 -4 S cm -1 , while the ionic conductivity of LiDFOB itself in Comparative Example 1 is lower than that of LiTFSI, and the ionic conductivity of its decomposition products (such as LiBO2) is even worse, so the ionic conductivity is less than 7×10 -4 S cm -1 In Comparative Example 2, the composite material prepared by wet grinding was found to have residual solvent that hindered ion transport, and the uneven coating layer increased the interfacial impedance, thus reducing the ionic conductivity to 7-7.5×10 -4 S cm -1 , which is significantly lower than the material prepared in the examples.

[0064] Experimental Example 2: In this example, unmodified LPSCl, Examples 1 to 3, and Comparative Examples 1 to 2 were used to assemble and perform lithium metal symmetrical batteries.

[0065] Experimental Procedure: 150 mg of unmodified LPSCl, the materials prepared in Examples 1-3, and Comparative Examples 1-2 were weighed, compacted, and sandwiched between two lithium sheets with a diameter of 6 mm and a thickness of 0.1 mm. This sandwich structure was then formed into a battery cell, which was then pressed using a hydraulic press at a pressure of 10 MPa. All of this was performed in an argon-filled glove box, where both water and oxygen contents were maintained below 0.01 ppm.

[0066] like Figure 6As shown, a symmetric Li / LiTFSI@LPSCl / Li battery system was assembled at 25°C. The performance of samples with different additive ratios was analyzed using impedance data presented in the Nyquist plot. From the perspective of electrochemical impedance, the impedance reflects the ease of charge transfer and ion transport within the battery. As a base material, LPSCl's impedance characteristics represent the inherent state of the battery system without additional components. The impedance values ​​of the three samples with different LiTFSI additions were similar. The 0.5% LiTFSI addition was too low, and the additive may not have fully optimized the compatibility of the electrode / electrolyte interface and effectively improved the ion conduction path. The sample with a 2% LiTFSI addition exhibited higher impedance than the sample with a 1% LiTFSI addition. This may be due to the excessive addition causing aggregation within the system, disrupting the relatively uniform ion conduction network, increasing ion transport resistance, and thus increasing charge transfer resistance. The sample with a 1% LiTFSI addition exhibited a more moderate impedance value in the Nyquist plot. This shows that at this ratio, the additive can effectively optimize the electrode / electrolyte interface, improve the ion conduction path, reduce the charge transfer resistance, and make the charge transfer and ion transport inside the battery smoother.

[0067] At the same time, combined with the symmetrical battery cycle performance graph, the above statement is also verified. 1% LiTFSI ratio performs best and is the ideal choice for this system. The specific test process is as follows:

[0068] At 0.1 mA cm -2 The symmetrical battery cycling performance was tested at a current density of 1.5 GHz. The LiTFSI@LPSCl prepared in Example 2 exhibited excellent cycling stability. Its crystallinity decreased due to high-energy ball milling, resulting in a decrease in ionic conductivity. Consequently, the initial overpotential (14 mV) was higher than the 4 mV of unmodified LPSCl. However, the overpotential increase in LiTFSI@LPSCl during symmetrical battery cycling was significantly smaller, and its overpotential rise rate was slower, indicating that the material has a stronger ability to suppress polarization and possesses higher cycling stability.

[0069] In comparison, although the unmodified LPSCl has a low initial overpotential, its overpotential shows a significant upward trend after long-term cycling, and a short circuit occurs after approximately 1500 hours, indicating its poor electrochemical stability during long-term use. The LiTFSI@LPSCl symmetric cell prepared in Example 2 of the present invention can be stably cycled for up to 5000 hours, demonstrating superior stability. The 0.5% and 2% samples prepared in Examples 1 and 3 can both be stably cycled for approximately 2000 hours. The materials prepared in Comparative Examples 1 and 2 have a short cycle life of less than 2000 hours due to decreased interfacial stability.

[0070] The results show that the LiTFSI@LPSCl prepared in Example 2 performs best and has excellent cycle stability (e.g. Figure 7 This demonstrates that the LiTFSI@LPSCl electrolyte not only excels in lithium stability but also offers significant advantages in cycling stability. The superior performance of LiTFSI@LPSCl can be attributed to its organic-inorganic layer structure formed after high-energy ball milling. This structure effectively optimizes the instability of the electrolyte-lithium electrode interface, allowing the battery to maintain low polarization even at high cycling frequencies, significantly extending its service life and reducing the risk of battery failure.

[0071] To further investigate the coating's effect on improving the stability of the lithium metal anode-electrolyte interface, a critical current density (CCD) test was performed. As an important indicator of interfacial stability, CCD effectively reflects the interfacial performance between the electrolyte and the lithium metal anode. To compare the dendrite suppression performance of the two symmetrical battery groups, Li / LPSCl / Li and Li / LiTFSI@LPSCl / Li, a critical current density test was performed.

[0072] like Figure 8 As shown in a, in the Li / LPSCl / Li symmetric battery system, its critical current density (CCD) is only 0.81 mA cm -2 In contrast, the Li / LiTFSI@LPSCl / Li symmetric battery using LiTFSI coated with LPSCl showed a CCD value of 1.01 mA cm under the same test conditions. -2 (like Figure 8 This data increase indicates that the LPSCl material modified with LiTFSI exhibits better performance in enhancing interface stability and inhibiting lithium dendrite growth; however, the materials prepared in Comparative Examples 1 and 2 have insufficient interface layer density, resulting in a CCD value drop to ≤0.8 mA cm -2 .

[0073] Therefore, the mechanism of action of the improvement effect of the materials prepared in the examples of the present application can be attributed to: through the high-energy ball milling process, LiTFSI forms a coating layer on the surface of the LPSCl particles, and generates inorganic composite layer structures such as LiF and LiN through interfacial reaction. These dense inorganic interface layers significantly optimize the contact characteristics between the lithium metal negative electrode and the sulfide electrolyte. On the one hand, they greatly reduce the amount of interfacial side reaction products generated, and on the other hand, they enhance the interfacial anti-polarization ability and structural stability. A more stable solid-solid interface can not only delay the initiation and growth of lithium dendrites, but also effectively reduce the risk of short circuits in the battery at high current density, ultimately achieving a dual improvement in battery safety and cycle life. Experimental Example 3: In this example, unmodified LPSCl, Examples 1 to 3 and Comparative Examples 1 to 2 were assembled and performance tested for all-solid-state lithium metal batteries.

[0074] Experimental Procedure: 150 mg of unmodified LPSCl, the materials prepared in Examples 1-3, and Comparative Examples 1-2 were weighed separately. After compaction, a 7 mm diameter composite cathode was attached to one side of the electrolyte, and 6 mm diameter lithium metal and 7 mm diameter indium metal were attached to the other side. The sandwich structure was placed in a battery mold and then pressed using a hydraulic press at a pressure of 7 MPa. All of the above processes were performed in an argon-filled glove box, with water and oxygen contents maintained below 0.01 ppm.

[0075] The test results show: Figure 9 The charge-discharge curves of LNO@NCM811 / LPSCl / Li-In and LNO@NCM811 / LiTFSI@LPSCl / Li-In batteries from 1 to 300 cycles at 30°C and 0.5C rate are shown. These curves reflect the performance of the battery at a specific temperature and charge-discharge rate. During the constant current charging phase, the current remains constant while the voltage gradually increases; during the constant voltage charging phase, the voltage remains constant while the current gradually decreases; and during the hysteresis charging phase, the current further decreases until the battery is fully charged. The LiTFSI@LPSCl material prepared in Example 1 has a smoother charge-discharge curve than the LPSCl material.

[0076] like Figure 10 As shown in the figure, the cycling performance test results of LNO@NCM811 / LPSCl / Li-In and LNO@NCM811 / LiTFSI@LPSCl / Li-In batteries at 0.5C show that the LiTFSI-coated LPSCl electrolyte exhibits better stability during long-term cycling. At 0.5C rate, the LiTFSI@LPSCl battery has a higher first-cycle discharge capacity of 144.7 mAh g -1After 300 cycles, the LiTFSI1@LPSCl battery maintained a capacity retention rate of 86.6%. This is due to the use of a lithium-indium alloy in the negative electrode, which, to a certain extent, demonstrates that it effectively reduces side reactions at the electrolyte-positive electrode interface, thereby improving the battery's cycling stability. In contrast, the unmodified LPSCl battery exhibited a significant capacity decay (59.3% after 300 cycles), and the battery was prone to high overpotentials and capacity decline after long-term cycling. Due to decreased interfacial stability, the full-cell capacity retention rate of Comparative Example 1 was significantly reduced, while Comparative Example 2 experienced accelerated capacity decay due to intensified interfacial side reactions, resulting in lower specific capacities than the batteries in the Examples.

[0077] The results show that LiTFSI-coated LPSCl electrolyte not only improves the rate performance of the battery, but also significantly improves the long-cycle stability of the battery. In particular, with the cooperation of lithium-indium alloy negative electrode, the interface stability between the electrolyte and the positive electrode is significantly enhanced.

[0078] like Figure 11 As shown in the figure, under the test conditions of a scan rate of 0.05mV / s, the cyclic voltammetry (CV) curve characteristics of unmodified LPSCl and LiTFSI@LPSCl are displayed. By comparison, it can be seen that the LiTFSI@LPSCl system can still maintain a high current response intensity after multiple cycles, especially compared with the original LPSCl, its current change trend is more gentle. Although the current showed a certain attenuation after 5 cycles, the decrease of LiTFSI@LPSCl was significantly smaller than that of the unmodified sample. This phenomenon indicates that the introduction of LiTFSI effectively improved the electrochemical stability of the system. LiTFSI@LPSCl showed better electrochemical stability during the cycle. Although there was a certain degree of current attenuation, its attenuation amplitude was smaller than that of the original LPSCl, showing better cycle life and stability.

[0079] Overall, the high-energy ball milling process was used to coat LiTFSI on the surface of LPSCl particles, which effectively improved the interfacial stability between the electrolyte and the positive electrode, reduced the side reactions on the positive electrode side, and thus improved the long-cycle stability and high-rate performance of the battery.

[0080] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A LiTFSI-coated Li6PS5Cl composite material for all-solid-state lithium metal batteries, characterized in that: The composite material includes Li6PS5Cl particles and a LiTFSI layer uniformly coated on the surface thereof, wherein the mass ratio of the LiTFSI to the Li6PS5Cl is 0.5 to 2:100; The LiTFSI layer is partially decomposed after high-energy ball milling to form an organic-inorganic composite interface layer containing LiF.

2. The LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery according to claim 1, characterized in that The organic-inorganic composite interface layer contains Li-F, Li-N and CF bonds, and the thickness of the interface layer is 85-105 nm.

3. The LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery according to claim 1, characterized in that The particle size of the composite material ranges from 5 to 10 μm, which is smaller than the particle size of the original Li6PS5Cl particles.

4. The LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery according to claim 1, wherein The ionic conductivity of the composite material is (8-9.6)×10 -4 S cm -1 .

5. A method for preparing a LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery according to any one of claims 1 to 4, characterized in that: Specifically, Li6PS5Cl powder and LiTFSI are mixed and subjected to high-energy ball milling to obtain a Li6PS5Cl composite material uniformly coated with LiTFSI.

6. The preparation method according to claim 5, wherein The high-energy ball milling is carried out in an inert atmosphere. Zirconia balls are selected for the ball milling process. The ball diameter is 8 to 10 mm and the ball-to-material ratio is selected at 40:1 to 1.

5.

7. The preparation method according to claim 5, wherein The process parameters of the high-energy ball milling include: a ball milling speed of 400 to 600 rpm; and a ball milling time of 10 to 20 hours.

8. Use of the LiTFSI-coated Li6PS5Cl composite material for all-solid-state lithium metal batteries according to any one of claims 1 to 4 in solid-state batteries.

9. An all-solid-state lithium metal battery, characterized in that: The invention comprises the LiTFSI-coated Li6PS5Cl composite material for an all-solid-state lithium metal battery according to any one of claims 1 to 4 as a solid electrolyte layer.

10. The all-solid-state lithium metal battery according to claim 9, wherein The all-solid-state lithium metal battery further includes a high-nickel layered oxide as a positive electrode material and a lithium-indium alloy as a negative electrode material; Preferably, the high nickel layered oxide positive electrode material is LiNi coated with lithium niobate. 0.8 Co 0.1 Mn 0.1 One of O2, lithium iron phosphate, NCM622, and lithium cobalt oxide; Preferably, the capacity retention rate of the all-solid-state lithium metal battery after 300 cycles at a 0.5C rate is ≥86%.

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