Lithium metal negative electrode for solid-state lithium metal battery and preparation method and application thereof

Abstract

The application belongs to the technical field of solid-state lithium metal batteries, and relates to modification of a lithium metal negative electrode of a solid-state lithium metal battery, in particular to a lithium metal negative electrode for a solid-state lithium metal battery and a preparation method and application thereof. The preparation method is as follows: the surface of a lithium metal sheet is changed from bright to matte by grinding and brushing, P2S5 powder is scattered on the surface of the lithium metal sheet after grinding and brushing, the P2S5 powder is rubbed to uniformly coat the surface of the lithium metal sheet after grinding and brushing, the excess P2S5 powder is removed, the P2S5 powder on the surface of the lithium metal sheet after grinding and brushing is rolled flat by using a force of 1.5-2.0 N, and then the reaction is allowed to stand for 10-24 hours, and the lithium metal negative electrode is obtained; the whole preparation process is carried out in an argon atmosphere. The application not only effectively hinders the contact between a solid-state electrolyte and lithium metal, improves the interface stability, effectively inhibits the formation of lithium dendrites, ensures the cycle stability, but also can improve the energy density of the solid-state lithium metal battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state lithium metal batteries, and relates to modification of a lithium metal negative electrode of a solid-state lithium metal battery, in particular to a lithium metal negative electrode for a solid-state lithium metal battery and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission or a recognition that the information forms part of the prior art that is already known in any country in the world.

[0003] Solid-state electrolytes are the core of all-solid-state lithium battery technology, which can be divided into two categories: polymer solid-state electrolytes and inorganic solid-state electrolytes. Inorganic solid-state electrolytes can be divided into oxide-based, sulfide-based and halide-based. Among these solid-state electrolyte materials, the Li6PS5Cl (LPSCl) electrolyte in sulfide electrolyte has the advantages of high ionic conductivity, good mechanical deformation ability, and easy synthesis. The LPSCl self-supporting film with polytetrafluoroethylene as the binder has extremely high ionic conductivity, which provides the possibility to improve the power density and energy density of all-solid-state lithium batteries. During the contact between the LPSCl thin film and the Li metal, the electrolyte is easily reduced by lithium metal and decomposes, resulting in an increase in interfacial impedance and a decrease in battery cycle stability. Moreover, electrons tend to gather at the grain boundaries, and lithium dendrites usually form and grow at the grain boundaries of sulfide electrolytes, eventually breaking through the electrolyte and causing battery short circuits. In addition, polytetrafluoroethylene can react with lithium metal to form conductive carbon.

[0004] The introduction of a polymer buffer layer between the solid-state electrolyte and the lithium metal can effectively alleviate the interface problem. However, the introduction of this additional buffer layer will form two new interfaces, namely the interface between the buffer layer and the solid-state electrolyte and the interface between the buffer layer and the lithium metal negative electrode. Due to the introduction of the interface buffer layer, it is difficult to accurately control the thickness of the interface layer. Therefore, the corresponding interface resistance and space charge effect problems occur. The passivated surface formed by immersing lithium metal in an organic solvent improves the stability of the lithium negative electrode. However, the toxic organic solvent will pollute the environment. SUMMARY

[0005] In order to solve the problems of the prior art, the purpose of the present application is to provide a lithium metal negative electrode for a solid-state lithium metal battery and a preparation method and application thereof. The present application not only effectively prevents the contact between the solid-state electrolyte and the lithium metal, improves the interface stability, and effectively inhibits the formation of lithium dendrites to ensure the cycle stability, but also improves the energy density of the solid-state lithium metal battery. At the same time, the preparation method of the present application can avoid the use of toxic organic solvents, and the preparation method is simple and can realize green and large-scale production.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] On one hand, a method for preparing a lithium metal anode for solid-state lithium metal batteries involves grinding the surface of a lithium metal sheet from glossy to matte, sprinkling P2S5 powder onto the surface of the ground lithium metal sheet, rubbing the P2S5 powder to evenly coat the surface of the ground lithium metal sheet, removing excess P2S5 powder, flattening the P2S5 powder on the surface of the ground lithium metal sheet with a force of 1.5~2.0N, and then allowing it to stand for 10~24 hours to react, thus obtaining the anode. The entire preparation process is carried out in an argon atmosphere.

[0008] This invention utilizes the reduction reaction between lithium metal and P2S5 to synthesize a protective layer on the lithium metal surface using a solvent-free brush plating method. This effectively hinders contact between the solid electrolyte and lithium metal, improving interfacial stability. Since the solid electrolyte is non-deformable, and P2S5 is granular and easily forms pores after reacting with the lithium metal sheet surface, studies have found that lithium dendrites easily form in these pores, affecting cycle stability. Therefore, this invention uses a rolling process to flatten the P2S5 powder, avoiding pore formation and allowing for better adhesion to the solid electrolyte. Further research shows that the rolling force should be appropriate; too little force results in poor flattening and compromises cycle stability, while too much force causes deformation of the lithium metal sheet, affecting electrochemical performance. Therefore, this invention uses a force of 1.5~2.0N to flatten the P2S5 powder, ensuring both electrochemical performance and cycle stability.

[0009] On the other hand, a lithium metal anode for solid-state lithium metal batteries is obtained by the above-described preparation method.

[0010] Thirdly, the application of the aforementioned lithium metal anode for solid-state lithium metal batteries in the preparation of solid-state lithium metal batteries.

[0011] Fourthly, a solid-state lithium metal battery includes the aforementioned lithium metal anode, LPSCl solid electrolyte, and cathode, wherein the modified surface of the lithium metal anode is in contact with the LPSCl solid electrolyte.

[0012] The beneficial effects of this invention are as follows:

[0013] This invention utilizes P2S5 to form a protective layer on the surface of lithium metal via solvent-free brush plating, and flattens the P2S5 powder by applying a force of 1.5~2.0N. Studies have shown that the lithium metal anode prepared by this method not only effectively hinders the contact between the solid electrolyte and lithium metal, improving interface stability, but also effectively suppresses the formation of lithium dendrites, ensuring cycle stability, and can improve the energy density of solid lithium metal batteries.

[0014] Experiments have shown that the lithium metal anode for solid-state lithium metal batteries provided by this invention, combined with the LPSCl thin film prepared by hot rolling process, forms a symmetrical battery at 0.1 mA cm⁻¹. -2 It can cycle stably for over 500 hours at current density; the formed full cell can provide 155.7 mA hg at 0.5 C rate. -1 The discharge specific capacity retains 75.5% after 400 charge-discharge cycles. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 The following are morphological and structural characterization images of P2S5@Li prepared according to embodiments of the present invention: (a) schematic diagram of the process for preparing P2S5@Li for all-solid-state lithium batteries using a solvent-free method; (b) cross-sectional morphology of Li metal; (c) cross-sectional morphology of Li metal after brushing treatment; (d) cross-sectional morphology of P2S5@Li; (e) surface morphology of P2S5@Li; and (f) EDS energy dispersive spectroscopy results of P2S5@Li.

[0017] Figure 2 The structural spectra of P2S5@Li prepared for embodiments of the present invention are shown in the following figures: (a) Raman spectrum of lithium metal, (b) Raman spectrum of P2S5, (c) Raman spectrum of P2S5@Li, and (d) XRD patterns of lithium metal and P2S5@Li.

[0018] Figure 3 The following are XPS fine spectra of P2S5 particles and P2S5@Li in embodiments of the present invention: (a) Li 1s spectrum of P2S5 particles, (b) Li 1s spectrum of P2S5@Li, (c) P 2p spectrum of P2S5 particles, (d) P 2p spectrum of P2S5@Li, (e) S2p spectrum of P2S5 particles, and (f) S 2p spectrum of P2S5@Li.

[0019] Figure 4 The figures show the electrochemical performance characterization of the batteries according to embodiments of the present invention. (a) Li / LPSCl film / Li and P2S5@Li / LPSCl film / P2S5@Li at 0.1 mA cm⁻¹ -2 Voltage distribution over cycle time, (b) and (c) Nyquist plots of symmetrical cells under different cycles, (d) Nyquist plots of P2S5@Li / LPSCl thin film / P2S5@Li symmetrical cells at different temperatures, (e) Activation energy of symmetrical cells;

[0020] Figure 5 The Nyquist plots of the Li / LPSCl thin film / Li-pair battery in this embodiment of the invention are shown in (a) different cycles and (b) 11 cycles.

[0021] Figure 6 The critical current density diagrams for the battery in this embodiment of the invention are shown in (a) Li / LPSCl film / Li, (b) P2S5@Li / LPSCl film / P2S5@Li, (c) is a magnified region of (a), and (d) is a magnified region of (b).

[0022] Figure 7 The figure shows the stability test results of the P2S5@Li / LPSCl film / P2S5@Li on the battery according to an embodiment of the present invention. (a) P2S5@Li / LPSCl film / P2S5@Li at 0.2 mA cm⁻¹ -2 (a) Voltage distribution during the next cycle time; (b) Schematic diagram of the stripping / electroplating behavior of the lithium metal anode; (c) Schematic diagram of the stripping / electroplating behavior of the P2S5@Li anode.

[0023] Figure 8 The figures show the electrochemical performance test results of the all-solid-state battery according to an embodiment of the present invention: (a) a schematic diagram of the all-solid-state battery assembly; (b) the cycling performance of Li / LPSCl film / LNO@NCM811 and P2S5@Li / LPSCl film / LNO@NCM811 at a current density of 0.1 C; (c) the charge-discharge curve of the Li / LPSCl film / LNO@NCM811 battery at 0.1 C; (d) the rate performance of Li and P2S5@Li at ASSLBs from 0.1 to 5 C; (e) the charge-discharge curve; and (f) and (g) the electrochemical performance of P2S5@Li / LPSCl film / LNO@NCM811 at 0.05 mV s⁻¹. -1 CV curves at different scan rates, (h) linear fitting of oxidation peak, (i) cycling performance of P2S5@Li / LPSCl film / LNO@NCM811 at 0.5C;

[0024] Figure 9 The figures show the electrochemical performance test results of the all-solid-state batteries before and after modification in this embodiment of the invention. (a) Cycling performance of Li / LPSCl film / LNO@NCM811 at 0.1C, (b) Charge-discharge curve of Li / LPSCl film / LNO@NCM811 battery at 0.1C, (c) Charge-discharge curve of unmodified battery in rate performance test, and (d) Cycling performance of Li / LPSCl film / LNO@NCM811 at 0.05 mV s⁻¹. -1CV curves at different scan rates for Li / LPSCl thin film / LNO@NCM811;

[0025] Figure 10 XPS spectra of the P2S5@Li / LPSCl films / LNO@NCM811 after cycling in this embodiment of the invention: (a) fine spectrum of P 2p, (b) fine spectrum of S 2p, (c) fine spectrum of Cl 2p, and (d) fine spectrum of F 1s. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] 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 scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. 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.

[0028] Given that existing lithium metal anodes for solid-state lithium metal batteries suffer from poor interfacial and cycle stability, and that their preparation methods require the use of toxic organic solvents, this invention proposes a lithium metal anode for solid-state lithium metal batteries, along with its preparation method and applications.

[0029] In a typical embodiment of the present invention, a method for preparing a lithium metal anode for a solid-state lithium metal battery is provided. The surface of a lithium metal sheet is brushed from glossy to matte. P2S5 powder is sprinkled on the brushed lithium metal sheet surface, and then the P2S5 powder is rubbed to make the P2S5 powder evenly spread on the brushed lithium metal sheet surface. Excess P2S5 powder is removed, and the P2S5 powder on the brushed lithium metal sheet surface is flattened with a force of 1.5~2.0N. Then, the reaction is allowed to stand for 10~24 hours to obtain the anode. The entire preparation process is carried out in an argon atmosphere.

[0030] In some embodiments, the thickness of the lithium metal sheet is 150~250 μm.

[0031] In some embodiments, the friction of P2S5 powder is carried out continuously in one direction, such as circumferentially.

[0032] In some embodiments, the moisture and oxygen content in the argon atmosphere during the preparation process is maintained below 0.01 ppm.

[0033] Another embodiment of the present invention provides a lithium metal anode for solid-state lithium metal batteries, obtained by the above preparation method.

[0034] A third embodiment of the present invention provides an application of the above-mentioned lithium metal anode for solid-state lithium metal batteries in the preparation of solid-state lithium metal batteries.

[0035] A fourth embodiment of the present invention provides a solid-state lithium metal battery, comprising the above-mentioned lithium metal anode, LPSCl solid electrolyte and positive electrode for solid-state lithium metal battery, wherein the modified surface of the lithium metal anode for solid-state lithium metal battery is in contact with the LPSCl solid electrolyte.

[0036] In some embodiments, polytetrafluoroethylene (PTFE) is used as a binder in the LPSCl solid electrolyte. The binder accounts for 3-7‰ of the total mass of the LPSCl solid electrolyte.

[0037] In some embodiments, the LPSCl solid electrolyte is an LPSCl thin film with a thickness of 40~80 μm.

[0038] In one or more embodiments, the LPSCl film is prepared by a hot rolling process. Specifically, the temperature of the hot rolling process is 70~80 °C.

[0039] In some embodiments, the active material of the positive electrode is LiNbO3@LiNi. 0.8 Co 0.1 Mn 0.1 O2.

[0040] To enable those skilled in the art to better 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 and comparative examples.

[0041] Example

[0042] Preparation of P2S5@Li anode

[0043] First, the lithium foil (200 μm) was gently rubbed with a brush until the surface became matte. P2S5 powder was refined through grinding and ball milling. Then, 20 mg of fine P2S5 powder was sprinkled onto the treated lithium surface. The metal surface was pressed with gloved fingers and rubbed continuously in one direction for 5 minutes to ensure the P2S5 powder was evenly applied to the entire lithium surface. Excess P2S5 powder was then removed. The P2S5@Li sample was placed between two layers of polyimide film (Mylar, PPI Adhesive Products Ltd., 100 μm) and rolled using a roller press (Hohsen Corp., HSAM-615H) (applying a force of 2.0 N) until the P2S5@Li sample reached a thickness of 150 μm, ensuring a uniform P2S2@Li layer. The modified lithium metal was ready for use after reacting in a glove box for 12 hours. In a comparative experiment, the lithium metal was rubbed in the same manner without the addition of powder. All of the above steps were carried out in an argon-filled glove box, where the moisture and oxygen content was kept below 0.01 ppm.

[0044] LPSCl solid electrolyte films were prepared using a hot rolling process. Li6PS5Cl powder was used as the solid electrolyte, and polytetrafluoroethylene (PTFE) was used as the binder. The LPSCl solid electrolyte powder was first sieved through a 200-mesh sieve and then placed into a 50 ml zirconium oxide container. The stoichiometric ratio of LPSCl to PTFE was 99.5:0.5. Then, 5 g of 3 mm diameter ball milling beads were used at a rotation speed of 200 rpm. -1 The mixture was ball-milled in a planetary ball mill for 1 hour. It was then rolled using a stainless steel cylindrical bar at 75°C until the desired thickness (50 μm) was achieved. The resulting material was then punched into pieces with an area of ​​0.785 cm². 2 The discs are used to assemble button cells. All the above steps are carried out in an argon-filled glove box, where the moisture and oxygen content is maintained below 0.01 ppm.

[0045] Assembly of P2S5@Li batteries

[0046] To assemble symmetrical batteries, a solid electrolyte film is sandwiched between two lithium sheets or modified P2S5@Li, each 6 mm in diameter and 0.1 mm thick. The sandwich structure is placed within a CR2025 coin cell and then pressed using a hydraulic press at 5 MPa. The entire process is performed in an argon-filled glove box, where water and oxygen levels are maintained below 0.01 ppm.

[0047] To assemble the full cell, a 7mm diameter composite positive electrode was attached to one side of the electrolyte membrane, and a 6mm diameter lithium metal or P2S5@Li electrode was attached to the other side. This cell was then placed inside a CR2025 coin cell, forming a sandwich structure. The cells were then pressed using a hydraulic press at 5.5 MPa. All of the above processes were performed in an argon-filled glove box, where water and oxygen content were maintained below 0.01 ppm.

[0048] Results and Discussion

[0049] like Figure 1 Figure a illustrates a schematic diagram of a solvent-free lithium metal surface modification method for all-solid-state batteries, where the surface is modified through scrubbing and rubbing. In a typical process, the surface of lithium metal (200 μm) is scrubbed in one direction with a brush until it becomes matte. Pretreated P2S5 powder is then sprinkled onto the brushed lithium metal surface and rubbed in one direction with gloved fingers. Finally, unreacted powder is removed from the surface with polyethylene. By forcing the P2S5 particles into contact with the lithium metal, a uniform solid coating is loaded onto the lithium metal surface through a spontaneous reduction reaction between the two. The morphology and elemental distribution of the P2S5@Li anode were investigated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Figure 1 b shows an optical photograph and SEM image of the original lithium metal surface. For example... Figure 1 As shown in Figure c, the brushed lithium metal surface exhibits an irregular serrated pattern. Contact with the ultrathin (50 μm) LPSCl film increases the risk of battery short circuits. Its poor surface density also increases the risk of more lithium ions being attracted and depositing to form lithium dendrites during cycling. Figure 1 As shown in Figure d, the surface density of Li metal modified with P2S5 coating is significantly improved. A very smooth and dense 7μm solid coating is uniformly applied to the irregularly serrated surface of the lithium metal, indicating improved contact between the lithium metal and the LPSCl film. Figure 1 As shown in Figure e, the lithium metal modified with P2S5 coating is covered by a large-area and continuous solid coating. When P2S5 particles rub against the lithium metal surface, the cavities on the lithium metal surface are filled by P2S5 particles and pressed against the surface, promoting a spontaneous solid-state reduction reaction. Simultaneously, P and S elements are uniformly distributed across the entire surface of the P2S5@Li anode. Figure 1 f). This means that P2S5@Li can suppress the growth of lithium dendrites caused by uneven lithium deposition.

[0050] The in-situ spontaneous reaction between lithium metal and P2S5 particles was detected by Raman spectroscopy. Figure 2 a and b are the Raman spectra of Li metal and P2S5 particles, respectively. Figure 2As shown in c, compared with the Raman peaks of P2S5 particles, the representative Raman peaks of P2S5@Li are absent, and the peaks located at 388.3, ​​402.2, and 417.8 cm⁻¹ are also present. -1 P2S6 4- P2S7 4- and PS4 3- The presence of the signal indicates that lithium metal, after undergoing the P2S5 scrubbing / friction process, has undergone a complete transformation into lithiation species, forming various anions. For example... Figure 2 As shown in d, the peak centered at 20 degrees belongs to the diffraction peak of the sealed transparent polymer. There are no obvious thiophosphate diffraction peaks in the figure, reflecting its amorphous characteristics. Compared with the crystalline structure, it is expected to play a significant role in regulating Li+ flux and alleviating lattice mismatch in the interface region.

[0051] X-ray photoelectron spectroscopy (XPS) analysis further confirmed that spontaneous reactions can occur between Li metal and P2S5 particles. Figure 3 a, Figure 3 c. Figure 3 e represents the fine XPS spectrum of P2S5 particles. The P 2p and S 2p spectra show that repeated washing and grinding processes lead to lithiation of the P2S5 powder, resulting in a shift in the binding energy of the P2S5 particles. These lithiations mainly include Li3PS4, Li4P2S7, and Li4P2S6, consistent with the Raman spectroscopy results. Figure 3 In b, the two Gaussian component peaks at 54.6 eV and 55.4 eV can be used to fit the XPS spectrum of Li 1s. The peak at 54.6 eV is related to the Li-S bond, and the peak at 55.4 eV is related to... Figure 1 The presence of the Li-O bond in b is related. Furthermore, the absence of a characteristic peak for lithium metal at 53.1 eV further confirms the presence of the in-situ LSP protective layer. (As...) Figure 3 As shown in d, six different bistates (PSP, P...) can be fitted. δ+ -S δ-X (and Li3P). The peak at 132.5 eV in the fine P2p spectrum can be attributed to the PSP bond. Furthermore, a pair of unique P2p peaks appear at 132.1 eV and 131.3 eV, which can be attributed to P... δ+ -S δ-X (Li3PS4X = 3 / 4, Li4P2S7 and Li4P2S6X = 2 / 3, P2S5X = 0), indicating the presence of PS4. 3- P2S7 4- and P2S6 4- Li3P, mainly composed of LPSs, is present at 128.1 eV. Similarly, the S 2p spectrum confirms the presence of P. δ+ -Sδ-X And the response peak of PSP ( Figure 2 d).

[0052] like Figure 4 As shown in Figure a, the Li / LPSCl thin film / Li symmetric cell operates at a current density of 0.1 mA cm⁻¹. -2 It exhibits a low overpotential of approximately 6 mV and short-circuit after 14 hours of cycling. During cycling, PTFE undergoes a defluorination reaction with the lithium metal surface, readily generating conductive carbon. sp 2 This process creates a poor mixed conductive interface, accelerating lithium dendrite formation. Lithium dendrites pierce the electrolyte connecting the positive and negative electrodes inside the battery, ultimately leading to an internal short circuit. The continuous conductive interface growth between lithium metal and electrolyte, along with dendrite growth, is prone to unstable and adverse reactions. Due to the low efficiency of lithium dendrite growth, it can potentially cause significant safety issues. The P2S5@Li / LPSCl thin film / P2S5@Li symmetric cell can achieve a speed of 0.1 mA cm⁻¹ at room temperature. -2 It provides a long cycle life of 500 hours with no significant voltage fluctuations. Therefore, the in-situ protective LPSs layer has good engineering performance, can prevent side reactions between lithium metal and PTFE, inhibit the growth of lithium dendrites, and help improve the efficiency of lithium-ion plating / stripping.

[0053] Further testing of the EIS of the Li-symmetric cell was conducted to reveal the interfacial dynamics evolution during discharge / charge cycling. The initial impedance of the Li / Li-symmetric cell was 124 Ω. ​​After 10 h of cycling, the resistance of the initial cell decreased, indicating that the reaction between Li metal and PTFE reduced the impedance. Figure 5 a) After 22 hours of cycling, the impedance value indicates a short circuit in the battery. Figure 5 b). Figure 4 b、 Figure 4 The P2S5@Li / P2S5@Li symmetric cell in section c exhibits minimal impedance change after 90 cycles. This further demonstrates that the in-situ LPS protective layer enhances interfacial stability, significantly improving the electrochemical performance of the symmetric cell. Figure 4 Figure d shows the Nyquist curves of the P2S5@Li / LPSCl film / P2S5@Li symmetric cell from 25°C to 75°C. The activation energy (Ea) was calculated according to Arrhenius (1-1) law, and the value at the P2S5@Li / LPSCl film / P2S5@Li interface was found to be 0.13 eV.

[0054] δ = A exp(-Ea / kt) (1-1)

[0055] in, δ Represents ionic conductivity. APre-exponential factor, Ea For activation energy, k Boltzmann's constant, t The low interface Ea can be attributed to the LPS protective layer formed by P2S5 and Li metal, as well as the high ionic conductivity and low energy barrier of Li metal in LPS, which are favorable for Li. + Rapid transfer via the interface.

[0056] Critical current density (CCD) is an important parameter characterizing the improved interface stability. To investigate the dendrite suppression capabilities of Li / LPSCl film / Li and P2S5@Li / LPSCl film / P2S5@Li, symmetrical cells were assembled to test the CCD before and after modification. The results are as follows: Figure 6 As shown, the CCD of the Li / LPSCl thin film / Li symmetric cell is only 0.2 mA cm⁻¹. -2 This is related to side reactions between the LPSCl film and lithium metal during cycling. Furthermore, the contact between PTFE and lithium metal increases the electronic conductivity of the LPSCl film, accelerating dendrite formation and leading to a short circuit in the battery. Figure 4 b and Figure 4 As shown in Figure d, the CCD performance of the P2S5@Li / LPSCl thin film / P2S5@Li symmetric cell was increased to 0.4 mA cm⁻¹ at room temperature. -2 .

[0057] Further testing was conducted on a P2S5@Li / LPSCl thin film / P2S5@Li symmetric cell at 0.2 mA cm⁻¹. -2 Stability under current density, such as Figure 7 As shown in Figure a, it can cycle stably for over 100 hours. To visually highlight the advantages of the in-situ SEI layer, a schematic diagram of the lithium deposition process of lithium metal and P2S5@Li anode is shown in Figure a. Figure 7 b、 Figure 7 As shown in Figure c, when the LPSCl film comes into contact with lithium metal, the inhomogeneity of the lithium metal surface leads to uneven lithium deposition. The PTFE in the LPSCl film reacts with the Li metal to produce conductive carbon, accelerating the formation of lithium dendrites. Unlike the unevenly deposited lithium metal, the P2S5@Li anode can uniformly deposit lithium metal at high current densities, significantly improving interface stability.

[0058] The electrochemical performance of the P2S5@Li anode was further evaluated by assembling a coin cell. For example... Figure 8 As shown in Figure a, the LPSCl film serves as the solid electrolyte, and the LPSCl electrolyte particles and LNO@NCM811 (LiNbO3@LiNi) are used. 0.8 Co 0.1 Mn 0.1O2, reference: Xuelei Li, Liubing Jin, Dawei Song, Hongzhou Zhang, Xixi Shi, Zhenyu Wang, Lianqi Zhang, Lingyun Zhu, LiNbO3-coated LiNi 0.8 Co 0.1 Mn 0.1 O2cathode with highdischarge capacity and rate performance for all-solid-state lithium battery, Journal of Energy Chemistry, 40 (2020) 39–45) The mixture of particles is a composite cathode (preparation process: LiNbO3@LiNi 0.8 Co 0.1 Mn 0.1 O2 is the positive electrode material. LPSCl powder is the electrolyte, VGCF is the active material conductive agent, and PTFE is the binder. The stoichiometric mass ratio of the positive electrode material, electrolyte, active material conductive agent, and binder is 100:100:6:1, and the mixture is added to a 50 ml zirconium oxide container. The mixture is then ball-milled for 1.5 hours at 300 rpm. -1 The mixture was then hot-pressed at 80°C to form a homogeneous mixture, creating a composite positive electrode. A schematic diagram shows the configuration of lithium metal and P2S5@Li as the negative electrodes. In an all-solid-state lithium battery, the areal loading of the composite positive electrode is approximately 3 mg cm⁻¹ within a charge / discharge potential range of 2.7 ~ 4.3 V. -2 .like Figure 8 As shown in b, the first discharge specific capacities of the Li / LPSCl thin film / LNO@NCM811 and P2S5@Li / LPSCl thin film / LNO@NCM811 all-solid-state batteries at room temperature and 0.1 C are 197 and 177 mA hg, respectively. -1 After 150 cycles, the capacity remained at 81% of the initial capacity (P2S5@Li anode). Notably, except for the first charge-discharge cycle, the average coulombic yield of P2S5@Li as an anode battery exceeded 99.5%, indicating that the electrode reaction is highly reversible. Figure 8 As shown in Figure i, the performance of the all-solid-state lithium battery was tested at a high current density of 0.5 C. After 400 cycles, the capacity retention reached 75.5%, demonstrating good cycle stability and rate performance. The unmodified Li / LPSCl thin film / LNO@NCM811 battery, after 11 cycles, showed overcharging and significant fluctuations in the charging curve due to the formation and dissolution of tiny lithium dendrites and the lithium metal acting as the negative electrode. Figure 9d). The side effects are due to the poor suppression of lithium dendrites by the LPSCl film, severe reactions between the electrolyte and lithium metal, and the reaction of its PTFE with lithium metal, which readily accepts electrons and defluorinates to form sp. 2 Therefore, the coulombic efficiency of the original sample is very low ( Figure 9 a). Furthermore, at current densities of 0.1, 1.0, 3.0, and 5.0 C, the reversible discharge capacities of the P2S5@Li / LPSCl thin film / LNO@NCM811 battery were 195, 128, 59, and 33 mA hg, respectively. -1 When the current density decreases from 5.0 C to 0.1 C, the corresponding capacity can be restored to 186 mA hg. -1 Conversely, all-solid-state lithium batteries assembled from pristine Li metal exhibited lower reversible capacity at different rates and also experienced overcharging during cycling. Figure 9 c). For example Figure 8 As shown in Figure e, the constant current charge-discharge curves of the P2S5@Li / LPSCl thin film / LNO@NCM811 battery demonstrate its rate performance. Figure 8 As shown in f, the P2S5@Li / LPSCl thin film / @NCM811 cell was tested at a scan rate of 0.05 mV / s. -1 The peak voltage difference of the sample in the first four cycles (2.7-4.4 V) showed no significant change, indicating good reversibility of lithium-ion insertion / extraction. The CV curve of the unmodified battery showed a significant drift, indicating poor electrochemical performance. Figure 9 d). By measuring different scan rates (0.05~0.6 mV s) -1 The CV curve of the all-solid-state lithium battery is shown in the figure, providing a deeper understanding of Li + Storage behavior ( Figure 8 g). With increasing scan rate, the current intensity of the redox peak increased significantly. The lithium-ion diffusion coefficient was calculated according to the Randles-Sevcik equation (1-2), and the reaction kinetics of the redox process of the P2S5@Li / LPSCl thin film / LNO@NCM811 battery were studied.

[0059] Ip = (2.69 × 10⁵) n 3 / 2 AD Li 1 / 2 C Li ν 1 / 2 (1-2)

[0060] The absolute value of the slope of the fitted line for the P2S5@Li / LPSCl thin film / LNO@NCM811 cell demonstrates its excellent rate capability and cycle stability. The Li / LPSCl thin film / @NCM811 cell achieves a cycle stability of 0.4 mV s⁻¹. 1 Significant polarization and short-circuiting occur at low scan rates, making it impossible to calculate the Li+ mobility coefficient. Figure 9 e). The in-situ LPS protective layer effectively hinders the reaction between LPSCl films, thus the P2S5@Li / LPSCl film / LNO@NCM811 battery exhibits excellent electrochemical performance.

[0061] The composite positive electrode film, electrolyte film, and negative electrode are pressed into a sandwich structure during the battery sealing stage. Due to the stickiness of PTFE, it is impossible to observe the morphology of the lithium surface after cycling. This part uses XPS to characterize the sample after cycling. By comparing and analyzing the characterization before and after cycling, the influence of the SEI layer formed in situ by P2S5 and lithium metal on the electrochemical performance of the all-solid-state battery can be determined.

[0062] like Figure 10 As shown, the Raman spectrum of the P2S5@Li / LPSCl film / LNO@NCM811 after 100 cycles at a current density of 0.5 C indicates that the P, S, Cl, F and C elements in the LPSCl film have not undergone chemical changes, exhibiting a typical silver-germanium sulfide electrolyte. This is consistent with the XPS spectrum of the original LPSCl film, further confirming that the in-situ LPS protective layer has the ability to suppress side reactions.

[0063] A solvent-free SEI protective layer was prepared in situ using the spontaneous reaction of P2S5 with lithium metal. An LPS lithiation interface layer with high lithium dendrite suppression capability was synthesized using a solvent-free scrubbing / friction method. This SEI film acts as a bridge between the LPSCl film and Li metal, improving the Li... + The transport efficiency at the lithium metal sulfide electrolyte interface is improved, and the surface energy can be effectively tuned to reduce cycle polarization. Thanks to this lithiation interface layer, P2S5@Li / LPSCl thin film / P2S5@Li symmetric cells can achieve a speed of 0.1 mA cm⁻¹. -2 Stable cycling performance exceeding 500 hours at current density. Using high-nickel cathode material LNO@NCM811 as the cathode, the LNO@NCM811 / LPSCl thin film / P2S5@Li all-solid-state battery exhibits high specific capacity and excellent cycle stability, reaching 155 mAh g⁻¹ at 0.5 C. -1 The capacity retention rate was 75.5% after 400 cycles. This embodiment provides a promising design method for improving the interface between the lithium metal anode and the SSE, which is conducive to the practical application of high energy density sulfide solid electrolytes in all-solid-state lithium batteries.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A solid-state lithium metal battery, characterized in that, It includes a lithium metal anode, an LPSCl solid electrolyte, and a cathode for solid-state lithium metal batteries, wherein the modified surface of the lithium metal anode for solid-state lithium metal batteries is in contact with the LPSCl solid electrolyte. The active material for the positive electrode is LiNbO3@LiNi 0.8 Co 0.1 Mn 0.1 O2; Polytetrafluoroethylene is used as a binder in LPSCl solid electrolyte; the binder accounts for 3 to 7‰ of the total mass of LPSCl solid electrolyte. Preparation method of lithium metal anode for solid-state lithium metal batteries: The surface of the lithium metal sheet is polished from glossy to matte. P2S5 powder is sprinkled on the polished lithium metal sheet surface, and then the P2S5 powder is rubbed to make it evenly spread on the surface of the polished lithium metal sheet. Excess P2S5 powder is removed, and the P2S5 powder on the surface of the polished lithium metal sheet is flattened with a force of 1.5~2.0N. Then, the reaction is allowed to stand for 10~12 hours to obtain the final product. The entire preparation process is carried out in an argon atmosphere.

2. The solid-state lithium metal battery as described in claim 1, characterized in that, The thickness of the lithium metal sheet is 150~250μm.

3. The solid-state lithium metal battery as described in claim 1, characterized in that, friction... P2S5 powder is continuously precipitated in one direction.

4. The solid-state lithium metal battery as described in claim 1, characterized in that, During the preparation process, the content of moisture and oxygen in the argon atmosphere is kept below 0.01 ppm.

5. The solid-state lithium metal battery as described in claim 1, characterized in that, The LPSCl solid electrolyte is an LPSCl thin film with a thickness of 40~80 μm; LPSCl films are prepared by hot rolling process at a temperature of 70~80 °C.

6. A lithium metal anode for use in solid-state lithium metal batteries, characterized in that, The lithium metal anode in the solid-state lithium metal battery according to any one of claims 1 to 4.

7. The application of the lithium metal anode of claim 6 for a solid-state lithium metal battery in the preparation of a solid-state lithium metal battery.

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