A method for improving the stability of LATP solid electrolyte on Li anode plates and its application

Abstract

This invention discloses a method and its application for improving the stability of LATP solid electrolyte on a Li anode sheet. The technical solution includes the following steps: S1. Preparing a LABTP solid electrolyte sheet by using at least boron oxide (B2O3) as the doping source of the LATP solid electrolyte; S2. Placing a high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE) with high ionic conductivity at room temperature, low charge transfer impedance with the lithium anode, and low charge transfer impedance with LABTP between the LABTP solid electrolyte sheet prepared in S1 and the metallic Li anode sheet. The advantages are as follows: By using boron oxide (B2O3) to dope the LATP solid electrolyte, a LABTP solid electrolyte sheet with high hardness, high density, high lithium-ion conductivity, and low electronic conductivity is formed.

Description

Technical Field

[0001] This invention relates to a method for improving the stability of LATP solid electrolyte on Li anode sheets. Background Technology

[0002] Traditional lithium-ion batteries use organic liquid electrolytes, which suffer from problems such as volatility, leakage, decomposition / deactivation under extreme high / low temperature environments, and easy dendrite puncture of the separator by the negative electrode surface. Furthermore, their compatibility with high-voltage positive electrodes and high-energy-density Li negative electrodes significantly limits their application. Solid electrolytes, compared to liquid electrolytes, offer advantages such as low volatility, near-zero flowability, high mechanical properties, and high stability. All-solid-state batteries using solid electrolytes not only possess excellent safety but also maintain normal operation over a wider temperature range. Replacing organic liquid electrolytes with solid electrolytes in all-solid-state lithium-ion batteries not only solves battery safety issues but also promises to address the low energy density of traditional lithium-ion batteries, aligning with the development direction of chemical power source energy storage technology.

[0003] Among solid-state electrolytes, NASICON (sodium fast ion conductor), an oxide solid-state electrolyte with high environmental stability, exhibits high ionic conductivity (approaching 0.1 mS / cm or higher). Lithium aluminum phosphate (LATP) in particular possesses advantages such as high environmental stability (to water and air), ease of synthesis, low cost, and high ionic conductivity (approaching 1 mS / cm), making it a promising solid-state electrolyte with the potential for large-scale industrial production. However, due to its low reduction potential at the negative electrode (-3.04 V, relative to the standard hydrogen electrode), severe side reactions occur at the contact between LATP and Li. The tetravalent titanium ions are reduced to trivalent ions, not only destroying the structure of LATP but also generating reaction products that create significant interfacial impedance, affecting lithium ion transport.

[0004] To address the aforementioned issues, ethylene oxide (PEO)-based polymer solid electrolyte buffer (SPE) layers are traditionally used as the interfacial layer for LATP electrolytes to solve these problems. However, current ethylene oxide polymer solid electrolyte buffer (SPE) layers still have the following drawbacks:

[0005] 1. It has low ionic conductivity at room temperature and needs to operate at 60°C or higher.

[0006] 2. Adding some plasticizers such as succinate (SN) can improve its room temperature ionic conductivity, but SN is prone to side reactions when in contact with the Li anode, and there is a large charge transfer resistance between SPE and LATP after the addition of SN.

[0007] 3. The ethylene oxide polymer solid electrolyte buffer layer (SPE) also has a large charge transfer resistance with the lithium anode. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method and application for improving the stability of LATP solid electrolyte on Li negative electrode.

[0009] To solve the above problems, the technical solution adopted by the present invention includes the following steps:

[0010] S1. At least boron oxide (B2O3) is used as the doping source for LATP solid electrolyte to prepare LABTP solid electrolyte sheet;

[0011] S2. A high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE) with high ionic conductivity at room temperature, low charge transfer impedance with the lithium anode, and low charge transfer impedance with LABTP is placed between the LABTP solid electrolyte sheet prepared in S1 and the metal Li anode sheet.

[0012] The method for improving the stability of LATP solid electrolyte on Li anode sheets is characterized by:

[0013] In S1, press Li. 1.3 Al 0.3-x B x Ti 1.7 (PO4)3 precursor compounds are weighed separately for lithium source, aluminum source, titanium source, phosphorus source, and dopant source, with the dopant source being 20-50% of the aluminum source. The lithium source compound is used in excess of 5-20% wt, x = 0.05 to 0.15. The lithium source compound is selected from one or more of LiOH, Li2CO3, CH3COOLi, and LiNO3. The aluminum source compound is selected from Al2O3, Al(OH)3, Al2(CO3)3, and C9H 21 One or more of the AlO3 compounds; the titanium source compound selected is C. 16 H 36 One or more of O4Ti and Ti(C3H7O)4; the phosphorus source is one or more of H3PO4, NH4H2PO4, and (NH4)2HPO4; the dopant source is boron oxide (B2O3).

[0014] The method for improving the stability of LATP solid electrolyte on Li anode sheets is characterized by further comprising the following steps:

[0015] S11. Mix the lithium source, aluminum source, titanium source, phosphorus source, dopant source and isopropanol in a mass ratio of 1:1 to 1:2;

[0016] S12. The mixture obtained in S11 is ground, dried, and screened to obtain LABTP solid electrolyte powder with a particle size of 400 to 600 nm, wherein the drying temperature is 60℃ to 100℃ and the drying time is 12h to 24h.

[0017] S13. The LABTP solid electrolyte powder obtained in S12 is calcined. The first step is to raise the temperature at a rate of 1 to 5 °C / min; raise the temperature to 350 °C or 500 °C and hold for 5 h; the second step is to raise the temperature at a rate of 1 to 5 °C / min; raise the temperature to 650 °C or 1100 °C and hold for 7 to 15 h; the cooling rate is controlled at 1 to 5 °C / min.

[0018] S14. The LABTP solid electrolyte that has been calcined in S13 is further ground, dried and screened to obtain LABTP solid electrolyte powder with a particle size of 400 to 600 nm, wherein the drying time is 12 h to 24 h and the drying temperature is 60 ° C to 100 ° C.

[0019] S15. Press the LABTP solid electrolyte powder obtained in S14 into electrolyte sheets, and then sinter them. The sintering conditions are: heating rate of 1 to 5℃ / min; heating to 650℃ or 800℃ and holding for 7 to 15 hours; cooling rate controlled at 1 to 5℃ / min to obtain dense LABTP solid electrolyte sheets.

[0020] The method for improving the stability of LATP solid electrolyte on Li anode sheets is characterized by further comprising the following steps:

[0021] S16. The LABTP solid electrolyte sheet obtained in S15 is polished sequentially on sandpaper of 280 grit, 1500 grit, 3000 grit and 5000 grit to obtain a smooth and dense LABTP solid electrolyte sheet.

[0022] The method for improving the stability of LATP solid electrolyte on Li anode sheets is characterized by:

[0023] In S2, the cyclic high-concentration lithium salt oxyethylene polymer solid electrolyte buffer layer (SPE) is composed of ethylene oxide (PEO), succinic anionyl (SN), trimethylol diethyl ether (G3), lithium bis(trifluoromethanesulfonyl)imide (LTFSI), fluoroethylene carbonate (FEC), and lithium nitrate (LiNO3).

[0024] The method for improving the stability of LATP solid electrolyte on Li anode sheets is characterized by further comprising the following steps:

[0025] S21. Weigh the required raw materials according to the molar ratio of ethylene oxide (PEO): butadienenitrile (SN): trimethylol diethyl ether (G3): lithium bis(trifluoromethanesulfonyl imide) (LTFSI) of 8:4:x:1+x, wherein the content of X is 1 to 4; then weigh lithium nitrate (LiNO3) and fluoroethylene carbonate (FEC) at 1 to 3% and 15 to 20% of the total mass, respectively.

[0026] S22. Add acetonitrile (AN) solvent at 6-10 times the total volume and stir until homogeneous to prepare SPE solution.

[0027] S23. The SPE solution prepared in S22 is evenly distributed on both sides of the polypropylene film (PP);

[0028] S24. Lay the polypropylene (PP) film coated with SPE solution flat and let it dry to prepare the SPE film;

[0029] S25. Place the SPE film prepared in S24 between the LABTP solid electrolyte sheet and the metallic Li anode sheet.

[0030] The method for improving the stability of LATP solid electrolyte on Li anode sheet is characterized in that: the water oxygen value in the above steps is <0.1ppm.

[0031] An all-solid-state lithium metal battery, characterized in that it comprises a LABTP solid electrolyte sheet prepared by any of the methods described above, and a high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE).

[0032] The advantages of the method for improving the stability of LATP solid electrolyte to Li anode sheet according to the present invention are as follows: LATP solid electrolyte is doped with boron oxide (B2O3) to form a LABTP solid electrolyte sheet with high hardness, high density, high lithium-ion conductivity, and low electronic conductivity; by introducing a self-supporting, high-concentration lithium salt ethylene oxide (PEO)-based polymer solid electrolyte buffer layer (SPE) with high ionic conductivity and low charge transfer impedance at room temperature between the LABTP solid electrolyte sheet and the metal Li anode sheet, on the one hand, the LABTP solid electrolyte sheet is protected from being reduced by metal Li, and on the other hand, the contact between the electrolyte sheet and the anode is increased, the interfacial impedance is reduced, and the transport of lithium ions is increased.

[0033] The present invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0034] Figure 1 These are SEM cross-sectional images of the present invention before (LATP) and after (LABTP);

[0035] Figure 2 This is a schematic diagram illustrating the structural changes before and after the invention of the LABTP / SPE / Li single-sided cycle;

[0036] Figure 3 This is the electrochemical impedance spectroscopy of the SS / SPE / SS coin cell of the present invention;

[0037] Figure 4 This is the electrochemical impedance spectroscopy of the Li / SPE / Li symmetric battery of the present invention;

[0038] Figure 5 This is the electrochemical impedance spectroscopy of the Li / SPE1 / LABTP / SPE1 / Li symmetric cell of the present invention;

[0039] Figure 6 This is a test diagram of the critical current density of the Li / SPE1 / LABTP / SPE1 / Li symmetrical battery of the present invention.

[0040] Figure 7 These are the charge-discharge curves of the Li / SPE1 / LABTP / SPE1 / Li symmetrical battery of the present invention at different current densities. Detailed Implementation

[0041] Example 1:

[0042] The method for improving the stability of LATP solid electrolyte to Li anode sheet adopted in this invention includes the following steps:

[0043] I. Preparation process of LABTP solid electrolyte sheet

[0044] Step 1. Press Li 1.3 Al 0.3-x B x Ti 1.7 (PO4)3 stoichiometric ratio: weigh the precursor compounds of lithium source, aluminum source, titanium source, phosphorus source and doped source respectively, wherein the doped source is 35% of the Al source and the compound used for lithium source needs to be in excess by 15%wt, x=0.1.

[0045] Step 2. The lithium source compounds selected are: lithium hydroxide (LiOH), lithium carbonate (Li2CO3), and lithium acetate (CH3COOLi, LiNO3); the aluminum source compounds selected are: aluminum oxide (Al2O3), aluminum hydroxide (Al(OH)3), aluminum carbonate (Al2(CO3)3), and aluminum isopropoxide (C9H2O). 21 AlO3); the selected titanium source compound was: titanium tert-butoxide (C 16 H 36The compounds selected for the phosphorus source are: phosphoric acid (H3PO4), ammonium dihydrogen phosphate (NH4H2PO4), and diammonium hydrogen phosphate ((NH4)2HPO4); the selected boron source is: boron trioxide (B2O3).

[0046] Step 3. Mix the above raw materials and isopropanol at a mass ratio of 1:1.5.

[0047] Step 4. Add the mixed raw materials and isopropanol into a ball mill for ball milling. The ball milling conditions are: ball-to-material ratio of 10:1; rotation speed of 400 rpm; and alternating forward and reverse rotation mode: 10 min forward, 10 min reverse, and 10 min interval in between. The total ball milling time is 30 h.

[0048] Step 5. Dry the ball-milled raw materials for 15 hours at a temperature of 80°C.

[0049] Step 6. Use a 400-mesh sieve to screen the dried raw materials.

[0050] Step 7. Place the sieved raw material into a dry pot for calcination. The dry pot should be either magnesium oxide or aluminum oxide.

[0051] Step 8. The calcination process and conditions are as follows: First step: heating rate is 3℃ / min; heat to 400℃ and hold for 5h; Second step: heating rate is 3℃ / min; heat to 650℃ or 1100℃ and hold for 7 to 15h; Cooling rate is controlled at 1 to 5℃ / min.

[0052] Step 9. Grind the calcined sample in an agate mortar for 45 minutes.

[0053] Step 10. Place the ground sample into a ball mill for ball milling. The ball milling conditions are: ball-to-material ratio of 5:1 to 20:1; rotation speed of 300 rpm to 600 rpm; and alternating forward and reverse rotation mode: 10 min forward, 10 min reverse, and 10 min interval in between. The total ball milling time is 30 h.

[0054] Step 11. Dry the ball-milled raw materials for 18 hours at a temperature of 80°C.

[0055] Step 12. Use a 400-mesh sieve to screen the dried raw material to obtain LABTP solid electrolyte powder with a particle size of about 400 to 600 nm.

[0056] Step 13. The prepared LABTP solid electrolyte powder is pressed into electrolyte sheets under a pressure of 400 MPa, and then sintered in a muffle furnace under the following conditions: heating rate of 35 °C / min; heating to 650 °C or 800 °C and holding for 7 to 15 hours; cooling rate controlled at 35 °C / min. This yields dense LABTP solid electrolyte sheets.

[0057] Step 14. The dense LABTP solid electrolyte sheet obtained by sintering is successively polished on 280-grit, 1500-grit, 3000-grit, and 5000-grit sandpaper to obtain a smooth and dense LABTP solid electrolyte sheet, hereinafter referred to as LABTP. Its cross-sectional morphology is as follows ( Figure 1 As shown in the figure, compared with undoped LATP, it has a more compact crystal structure and crystallinity, which can better resist the growth of lithium dendrites.

[0058] II. Preparation process of high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE):

[0059] Step 1. Weigh the required raw materials according to the molar ratio of ethylene oxide (PEO): succinate (SN): trimethylol diethyl ether (G3): lithium bis(trifluoromethanesulfonylimide) (LTFSI) of 8:4:x:1+x, where the content of X is 2.

[0060] Step 2. Weigh lithium nitrate (LiNO3) and fluoroethylene carbonate (FEC) at 23% and 17% of the total mass, respectively.

[0061] Step 3. Add acetonitrile (AN) solvent at 8 times the total volume.

[0062] Step 4. Place the prepared raw materials into a brown glass bottle (to prevent LiNO3 from decomposing in light), add a polytetrafluoroethylene stir bar, and place it on a magnetic stirrer to mix evenly. The stirring parameters are 450 r / min and 12 h to prepare the SPE solution.

[0063] Step 5. Take 100uL of the prepared SPE solution and drop it evenly onto the metal Li anode sheet. Then, attach the polypropylene film (PP) onto the metal Li anode sheet with the SPE solution. After one side of the polypropylene film (PP) is fully wetted, wet the other side of the film with the prepared SPE solution.

[0064] Step 6. Dry the metal Li anode sheet containing the SPE solution at room temperature for 12 hours until the acetonitrile (AN) solvent has completely evaporated.

[0065] Step 7. Attach the metal Li anode sheet prepared in Step 6 to the LABTP solid electrolyte sheet, that is, set a high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE) between the LABTP solid electrolyte sheet and the metal Li anode sheet, hereinafter referred to as SPE.

[0066] Note: The oxygen level in the water during the above steps is <0.1 ppm.

[0067] Functions of each component in the above SPE:

[0068] Ethylene oxide (PEO) serves as the framework and carrier of the buffer layer. On the one hand, it plays a role in conducting lithium ions; on the other hand, it interacts with the PP film to form a self-supporting scaffold, which can facilitate film formation and prevent lithium dendrite formation.

[0069] Trimethyl glycol diethyl ether (G3), as a plasticizer, combines with ethylene oxide (PEO) under the action of Li salt. This can change the aggregated phase structure of ethylene oxide (PEO) and generate more amorphous phases. It can weaken the binding ability of Li+ and TFSI-, generate more freely moving Li+, and dissolve a lot of LTFSI.

[0070] Succinate (SN), acting as a plasticizer, facilitates the full ionization of the LiTFSI salt, thus providing plasticization without significantly affecting the polymer's mechanical properties. Furthermore, it reduces side reactions within the system. Additionally, under the influence of the lithium salt, it bonds with ethylene oxide (PEO) groups. Therefore, this system is a three-phase miscible polymer of PEO-SN-G3.

[0071] Additionally: LTFSI is a conductive Li + The system uses lithium salts; FEC and LiNO3 are additives that can form a stable Li3N-LiF passivation layer in situ on the negative electrode side during cycling, improving the negative electrode stability. Furthermore, the contact between FEC and LATP leads to the defluorination of FEC, generating low-polymer VC (ethylene carbonate) and LiF, thus increasing the contact between LATP and the polymer side. PP serves as a scaffold in this system, providing mechanical stability.

[0072] The present invention addresses the problems of traditional SPEs through the following steps:

[0073] 1. Add an appropriate amount of succinate (SN) to improve the room temperature ionic conductivity.

[0074] 2. Add appropriate and suitable additives (fluoroethylene carbonate (FEC), lithium nitrate (LiNO3)) to stabilize the system interface;

[0075] 3. Increase the lithium salt concentration to increase the carrier concentration and reduce the charge transfer impedance at the interface;

[0076] 4. Find a substance that can dissociate high concentrations of lithium salt and will not react with the system (trimethyl glycol diethyl ether (G3) in the system).

[0077] The problem that this invention, SPE, can solve is:

[0078] 1. Due to the flexibility of the polymer, when this interface layer is used as a LATP interface modification, it can effectively avoid side reactions caused by the contact between LATP and the lithium anode; and it can also improve the contact and reduce the contact resistance of the anode interface.

[0079] 2. Traditional PEO polymers have very low ionic conductivity at room temperature, requiring temperatures of 60°C or higher to effectively conduct lithium ions. Therefore, when traditional PEO-based polymers are used as interfaces at room temperature, they can hinder lithium ion transport. Although studies have shown that adding SN can significantly increase the ionic conductivity of PEO polymers at room temperature, excessive SN can cause severe side reactions with the lithium anode, leading to increased interfacial impedance and poor cycle stability. Therefore, the SN content needs to be carefully controlled. Adding a small amount of G3 to the PEO+SN system can further improve the ionic conductivity, but since excessive G3 can also cause side reactions with the lithium anode, the G3 content also needs to be carefully controlled.

[0080] 3. The addition of FEC and LiNO3 can, on the one hand, form a stable Li3N-LiF protective layer on the lithium anode, improving the cycle stability of this interface; on the other hand, it can form a VC-LiF protective layer on the LATP side through low-temperature heating, improving contact with the solid electrolyte and forming a multilayer protective layer (such as...). Figure 2 (As shown).

[0081] 4. When traditional PEO-based polymers are used as interfacial modifications for LATP, the charge transfer resistance (Rct) at the PEO / LATP interface is relatively high. However, studies have found that increasing the lithium-ion concentration can reduce the charge transfer resistance at the PEO / LATP interface. Due to the strong interaction between G3 and lithium ions, the addition of G3 can dissolve more lithium salt than in the PEO+SN system, thereby significantly reducing the charge transfer resistance (Rct) at the PEO / LATP interface.

[0082] The following experimental examples further illustrate the beneficial effects of the present invention:

[0083] Experiment 1. The SPE prepared above was used as a blocking electrode on both sides to assemble an SS / SPE / SS coin cell. The electrochemical impedance spectroscopy is shown in the figure below. Figure 3As shown, SPE1, SPE2, and SPE3 are SPEs with different concentrations of G3 added (EO:G3 molar ratios of 2:1, 4:1, and 6:1), and their ionic conductivities at room temperature are 0.96, 0.94, and 0.88 mS / cm, respectively. -2 They all have very high ionic conductivity.

[0084] Experiment 2. The SPE1, SPE2, and SPE3 prepared above were assembled into Li-SPE-Li symmetric cells, and their EIS impedance was measured. Figure 4 The electrochemical impedance spectroscopy (EIR) plots for the Li / SPE / Li symmetric cells show that the charge transfer impedance (Rct) at the SPE / lithium metal interface is very small. The Rct values ​​for SPE1, SPE2, and SPE3 are 35 Ω, 45 Ω, and 45 Ω, respectively.

[0085] Experiment 3. Assemble a Li / SPE / LABTP / SPE / Li symmetric cell and measure its EIS impedance. It was found that the Rct at the LABTP / SPE / lithium metal interface was also very small. Subtracting the Rct at the SPE / lithium metal interface yielded the interface impedance of LABTP / SPE. SPE1, with the highest ionic conductivity, was selected as the interface modification layer. Figure 5 The electrochemical impedance of Li / SPE1 / LABTP / SPE1 / Li was calculated, and the interfacial impedance on one side of LABTP / SPE was only 56Ω.

[0086] Experiment 4. Assemble a Li / SPE / LABTP / SPE / Li symmetric cell and measure its critical current density (CCD). Figure 6 The figure shows the CCD curves of a Li / SPE / LABTP / SPE / Li symmetric cell. It can be seen from the figure that its CCD has a high efficiency of 2.5 mA / cm². -2 The above demonstrates that it has good resistance to lithium dendrite formation even at high current densities.

[0087] Experiment 5. Assemble a Li / SPE / LABTP / SPE / Li symmetric cell and measure its cycle performance. Figure 7 The charge-discharge cycle curves of the Li / SPE / LABTP / SPE / Li symmetric cell at different current densities are shown at 0.5 mA / cm². -2 The modified interface exhibits stable cycling at a current density, and the polarization voltage does not increase significantly after more than 800 hours of cycling, indicating that the modified interface has good cycling stability for Li.

[0088] By substituting the compounds and process parameters in the examples according to the above method, the same beneficial effects can be achieved.

[0089] Example 2:

[0090] The all-solid-state lithium metal battery of the present invention uses the LABTP solid electrolyte sheet prepared in Example 1 as the solid electrolyte. A high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE) of Example 1 is disposed between the LABTP solid electrolyte sheet and the metal Li anode sheet. Other preparation processes of the all-solid-state lithium metal battery are known technologies and will not be described in detail here.

[0091] As stated above, this is not intended to limit the present invention in any way. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed structure and technical content to create equivalent embodiments without departing from the scope of the present invention. However, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for improving the stability of LATP solid electrolyte on Li anode sheets, characterized in that, Includes the following steps: S1. At least boron oxide (B2O3) is used as the doping source for LATP solid electrolyte to prepare LABTP solid electrolyte sheet; S2. A high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE) is placed between the LABTP solid electrolyte sheet prepared in S1 and the metal Li anode sheet. In S2, the high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE) is composed of ethylene oxide (PEO), succinate (SN), trimethylol diethyl ether (G3), lithium bis(trifluoromethanesulfonyl)imide (LTFSI), fluoroethylene carbonate (FEC), and lithium nitrate (LiNO3), and further includes the following steps: S21. Weigh the required raw materials according to the molar ratio of ethylene oxide (PEO): succinate (SN): trimethylol diethyl ether (G3): lithium bis(trifluoromethanesulfonyl imide) (LTFSI) of 8:4:x:1+x, wherein the content of X is 1 to 4; then weigh lithium nitrate (LiNO3) and fluoroethylene carbonate (FEC) at 1 to 3% and 15 to 20% of the total mass, respectively. S22. Add acetonitrile (AN) solvent at 6-10 times the total volume and stir until homogeneous to prepare SPE solution; S23. The SPE solution prepared in S22 is evenly distributed on both sides of the polypropylene film (PP); S24. Lay the polypropylene (PP) film coated with SPE solution flat and let it dry to prepare the SPE film; S25. Place the SPE film prepared in S24 between the LABTP solid electrolyte sheet and the metal Li anode sheet; In the above steps, the oxygen level in the water is <0.1 ppm.

2. The method for improving the stability of LATP solid electrolyte on Li anode plates according to claim 1, characterized in that: In S1, press Li. 1.3 Al 0.3-x B x Ti 1.7 (PO4)3 precursor compounds are weighed separately for lithium source, aluminum source, titanium source, phosphorus source, and dopant source, with the dopant source being 20-50% of the aluminum source. The lithium source compound is used in excess of 5-20% wt, x = 0.05 to 0.

15. The lithium source compound is selected from one or more of LiOH, Li2CO3, CH3COOLi, and LiNO3. The aluminum source compound is selected from Al2O3, Al(OH)3, Al2(CO3)3, and C9H 21 One or more of the AlO3 compounds; the titanium source compound selected is C. 16 H 36 One or more of O4Ti and Ti(C3H7O)4; the phosphorus source is one or more of H3PO4, NH4H2PO4, and (NH4)2HPO4; the dopant source is boron oxide (B2O3).

3. The method for improving the stability of LATP solid electrolyte on Li anode sheet according to claim 2, characterized in that, It also includes the following steps: S11. Mix lithium source, aluminum source, titanium source, phosphorus source, dopant source and isopropanol in a mass ratio of 1:1 to 1:2; S12. The mixture obtained in S11 is ground, dried and screened to obtain LABTP solid electrolyte powder with a particle size of 400 to 600 nm, wherein the drying temperature is 60°C to 100°C and the drying time is 12 h to 24 h. S13. The LABTP solid electrolyte powder obtained in S12 is calcined. The first step is to raise the temperature at a rate of 1 to 5 °C / min; raise the temperature to 350 °C to 500 °C and hold for 5 h; the second step is to raise the temperature at a rate of 1 to 5 °C / min; raise the temperature to 650 °C to 1100 °C and hold for 7 to 15 h; the cooling rate is controlled at 1 to 5 °C / min. S14. The LABTP solid electrolyte that has been calcined in S13 is further ground, dried and screened to obtain LABTP solid electrolyte powder with a particle size of 400 to 600 nm. The drying time is 12 h to 24 h and the drying temperature is 60 ° C to 100 ° C. S15. Press the LABTP solid electrolyte powder obtained in S14 into electrolyte sheets, and then sinter them. The sintering conditions are: heating rate of 1 to 5 °C / min; heating to 650 °C to 800 °C and holding for 7 to 15 h; cooling rate controlled at 1 to 5 °C / min to obtain dense LABTP solid electrolyte sheets.

4. The method for improving the stability of LATP solid electrolyte on Li anode sheet according to claim 3, characterized in that, It also includes the following steps: S16. The LABTP solid electrolyte sheet obtained in S15 is polished sequentially on sandpaper of 280 grit, 1500 grit, 3000 grit and 5000 grit to obtain a smooth and dense LABTP solid electrolyte sheet.

5. An all-solid-state lithium metal battery, characterized in that: It comprises a LABTP solid electrolyte sheet prepared by the method according to any one of claims 1-4 and a high-concentration lithium salt ethylene oxide polymer solid electrolyte buffer layer (SPE).

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