A cobalt and bismuth double-doped solid-state electrolyte, and a preparation method and application thereof

Abstract

The application belongs to the technical field of solid electrolyte, and particularly relates to a cobalt and bismuth double-doped solid electrolyte as well as a preparation method and application thereof. The preparation method of the cobalt and bismuth double-doped solid electrolyte comprises the following steps: (1) uniformly mixing LiNO3, NH4H2PO4 and water to obtain solution A; dissolving Ti(OC4H9)4 in a citric acid solution, adding a catalyst, heating, and uniformly stirring to obtain solution B; (2) adding solution A into solution B dropwise; after the dropwise addition is completed, adjusting pH, adding a dispersing agent, and stirring to obtain a precursor solution; (3) heating, drying and calcining the precursor solution. The cobalt and bismuth double-doped solid electrolyte can improve the macroscopic ionic conductivity by synergistically optimizing the microcosmic bulk phase and interface phase ion transmission.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, specifically relating to a cobalt and bismuth co-doped solid electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium titanium aluminum phosphate (Li 1.4 Al 0.4 Ti 1.6 (PO4)3 (LATP) is a typical NASICON-type inorganic solid electrolyte. With its three-dimensional open crystal framework structure, it has high intrinsic lithium-ion conductivity, a wide electrochemical stability window, and good chemical stability, making it an electrolyte material with great application potential in all-solid-state lithium batteries.

[0003] Pure-phase LATP has several inherent defects that limit its large-scale application in solid-state batteries. First, polycrystalline LATP has a large number of grain boundaries and high grain boundary impedance, which significantly reduces the overall lithium-ion conduction efficiency of the material, and the room-temperature ionic conductivity is difficult to meet the requirements of practical applications. Second, the ion migration channels inside the LATP lattice are narrow, and the lithium-ion transport steric hindrance is large, so the ion dynamics performance needs to be further improved. At the same time, LATP has poor mechanical toughness and high brittleness, making it difficult to effectively suppress lithium dendrite growth and penetration, and short-circuit problems are prone to occur during battery cycling.

[0004] To overcome the limitations of existing technologies, it is urgent to develop a modification scheme that can simultaneously optimize crystal structure, ion transport properties and interface stability.

[0005] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a cobalt and bismuth co-doped solid electrolyte, its preparation method and application, so as to help solve or improve at least one of the problems of high grain boundary impedance, limited lithium-ion transport capacity and poor interface stability of traditional LATP solid electrolytes.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a cobalt and bismuth co-doped solid electrolyte, comprising the following steps: (1) mixing LiNO3, , Mix NH4H2PO4 with water to obtain solution A; then mix Ti(OC4H9)4 and... Dissolve in citric acid solution according to stoichiometric ratio, add ammonia as catalyst, heat and stir evenly to obtain solution B; (2) Add solution A dropwise to solution B and stir to mix evenly; after the dropwise addition is completed, adjust pH to 7, add dispersant, and stir to obtain precursor solution; (3) Heat the precursor solution to obtain wet gel, dry the wet gel to obtain dry gel, and calcine the dry gel to obtain the cobalt and bismuth doped solid electrolyte LATP-CoBi.

[0008] Preferably, in the cobalt and bismuth co-doped solid electrolyte LATP-CoBi, the stoichiometric ratio of Li, Al, Ti, Co and Bi is 1.4:(0.4-x):1.2:0.4:x; where x = 0.01-0.04.

[0009] Preferably, in step (3), the calcination temperature is 750-900℃ and the calcination time is 3.8-4.2h.

[0010] Preferably, in step (3), the heating temperature is 75-85℃, the heating time is 14-16h, and the heating is continuously stirred during the heating process; the drying temperature is 100-130℃, and the drying time is 3-6h.

[0011] Preferably, in step (1), after adding ammonia water, the mixture is heated at 65-75°C for 0.8-1.2 hours; in step (2), the dispersant is ethylene glycol.

[0012] The present invention also provides a cobalt and bismuth co-doped solid electrolyte, which adopts the following technical solution: a cobalt and bismuth co-doped solid electrolyte, wherein the cobalt and bismuth co-doped solid electrolyte is prepared by the method described above.

[0013] The present invention also provides a method for preparing a solid electrolyte membrane, which adopts the following technical solution: A method for preparing a solid electrolyte membrane, further comprising the following steps: I. Mixing polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide and solvent uniformly to obtain solution C; II. Mixing and stirring the cobalt and bismuth co-doped solid electrolyte as described above with solution C to obtain a composite slurry; III. Placing the composite slurry in a mold and drying it to obtain the solid electrolyte membrane.

[0014] Preferably, the mass ratio of polyethylene oxide to the cobalt and bismuth co-doped solid electrolyte is 1:(0.5-1); the mass of lithium bis(trifluoromethanesulfonyl)imide is 7%-7.5% of the polyethylene oxide; in step I, the solvent is acetonitrile, and the mixture is uniformly mixed under continuous stirring at 50-60°C for 3-5 hours; in step II, the mixing and stirring time is 5-6 hours; in step III, the drying temperature is 70-80°C, the drying time is 12-18 hours, and after drying, the solvent is slowly evaporated at room temperature for 12-14 hours; the thickness of the solid electrolyte membrane is 300-500 μm.

[0015] The present invention also provides a solid electrolyte membrane, which adopts the following technical solution: a solid electrolyte membrane, wherein the solid electrolyte membrane is prepared by the method described above.

[0016] The present invention also provides a solid-state battery, which adopts the following technical solution: a solid-state battery, wherein the solid-state battery adopts a cobalt and bismuth dual-doped solid electrolyte as described above; or, the solid-state battery adopts a solid electrolyte membrane as described above.

[0017] Beneficial effects: (1) In the cobalt and bismuth co-doped solid electrolyte (LATP-CoBi) of the present invention, Bi 3+ Successful entry into the crystal lattice and induction of lattice volume increase resulted in good lattice control, leading to regular powder particle morphology and uniform size. Cobalt and bismuth co-doping induced stronger lattice distortion and Li site environment differentiation, enhancing Li... + Mobility; in the cobalt and bismuth co-doped solid electrolyte of the present invention, Co is in the form of Co 2+ / Co 3+ Mixed valence state, Bi with Bi 3+ Valence states exist, and lattice charge balance is maintained through valence state compensation (i.e., the cobalt and bismuth co-doped solid electrolyte of the present invention can optimize the microscopic LATP bulk phase). Furthermore, the cobalt and bismuth co-doped solid electrolyte of the present invention also helps to reduce the crystallinity of PEO (i.e., the cobalt and bismuth co-doped solid electrolyte of the present invention can optimize the PEO interface phase), thereby reducing Li... + Transport resistance in PEO. In summary, the cobalt and bismuth co-doped solid electrolyte of the present invention can improve macroscopic ionic conductivity by synergistically optimizing ion transport in the microscopic bulk phase (LATP) and interfacial phase (PEO).

[0018] (2) The solid electrolyte membrane (PEO-LATP-CoBi) of the present invention has a uniform surface, maintains good thermal stability and certain ductility, and can effectively suppress lithium dendrite puncture.

[0019] (3) Based on the adjustment of crystal structure and thermal stability, the solid electrolyte membrane of the present invention has achieved the improvement of ionic conductivity, electrochemical stability window, lithium ion transference number and full battery cycle performance of LATP-based solid electrolyte membrane, showing a more balanced comprehensive performance advantage, and providing a feasible synergistic modification technology route for electrolyte design of high energy density lithium metal solid batteries.

[0020] (4) The electrochemical stability window of the solid electrolyte membrane of the present invention can be widened to 5.22V, and its high voltage oxidation resistance is enhanced; the lithium ion transference number (LTL) The efficiency can reach 0.9632, indicating good interface stability. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, 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 undue limitation of the invention. Wherein: Figure 1 LATP-Co 0.4 Bi 0.01 LATP-Co 0.4 Bi 0.02 LATP-Co 0.4 Bi 0.03 LATP-Co 0.4 Bi 0.04 and LATP-Co 0.4 XRD patterns of Bi0; the left image is the complete XRD pattern, and the right image is a magnified view of a portion of the left image.

[0022] Figure 2 LATP-Co 0.4 Bi 0.03 Microscopic morphology and elemental distribution analysis diagrams; where (a) is a SEM image, (b) is a surface scan of Al, (c) is a surface scan of Ti, (d) is a surface scan of Co, and (e) is a surface scan of Bi.

[0023] Figure 3 For LATP, LATP-Co 0.2 LATP-Co 0.4 Bi0 and LATP-Co 0.6 SEM images; where (a) is the SEM image of LATP, and (b) is the SEM image of LATP-Co. 0.2 SEM images, (c) showing LATP-Co 0.4 SEM image of Bi0, (d) is LATP-Co 0.6 SEM image.

[0024] Figure 4 LATP-Co0.4 Bi 0.03 XPS fine spectra; where (a) is the total spectrum, (b) is the O 1s spectrum, (c) is the Al 2p spectrum, (d) is the Co 2p spectrum, (e) is the Ti 2p spectrum, and (f) is the Bi 4f spectrum.

[0025] Figure 5 These are solid-state nuclear magnetic resonance spectra; where (a) is the LATP spectrum. 7 Li solid-state NMR spectrum, (b) is LATP-Co 0.4 Bi 0.03 of 7 Li solid-state nuclear magnetic resonance spectrum.

[0026] Figure 6 PEO-LATP-Co 0.4 Bi 0.03 SEM images, surface scans, and optical photographs of solid electrolyte membranes; where (a) is a surface SEM image, (b) is a surface scan of Ti in (a), (c) is a surface scan of Co in (a), (d) is a surface scan of Bi in (a), (e) is a cross-sectional SEM image, (f) is a surface scan of Ti in (e), (g) is a surface scan of Co in (e), (h) is a surface scan of Bi in (e), and (i) is a PEO-LATP-Co... 0.4 Bi 0.03 Optical photograph of a solid electrolyte membrane.

[0027] Figure 7 For PEO-LATP, PEO-LATP-Co 0.4 Bi0 and PEO-LATP-Co 0.4 Bi 0.03 DSC curves of three solid electrolyte membranes.

[0028] Figure 8 PEO-LATP-Co 0.4 Bi0, PEO-LATP-Co 0.4 Bi 0.01 ,PEO-LATP-Co 0.4 Bi 0.02 ,PEO-LATP-Co 0.4 Bi 0.03 and PEO-LATP-Co 0.4 Bi 0.04 The results of the electrochemical impedance and ionic conductivity tests are shown in the figure; where (a) is the electrochemical impedance test result figure and (b) is the ionic conductivity test result figure.

[0029] Figure 9The figures show the LSV comparison and CV curves; where (a) is the PEO-LATP-Co... 0.4 Bi0, PEO-LATP-Sn 0.3 PEO-LATP and PEO-LATP-Co 0.4 Bi 0.03 LSV comparison diagram, (b) is PEO-LATP-Co 0.4 Bi 0.03 The CV curve.

[0030] Figure 10 The graph shows the IT (polarization) curves and the electrochemical impedance spectroscopy before and after IT; where (a) is the PEO-LATP-Co... 0.4 Bi 0.02 The IT curve, (b) is the PEO-LATP-Co 0.4 Bi 0.03 The IT curve, (c) is the PEO-LATP-Co 0.4 Bi 0.02 Electrochemical impedance spectroscopy comparison before and after IT, (d) is PEO-LATP-Co 0.4 Bi 0.03 Comparison of electrochemical impedance before and after IT.

[0031] Figure 11 PEO-LATP-Co 0.4 Bi 0.03 Figure showing the cycle performance test results of the solid electrolyte membrane.

[0032] Figure 12 PEO-LATP-Co 0.4 Bi 0.03 A schematic diagram of the crystal structure of a solid electrolyte membrane and a schematic diagram of Li transport at different sites; wherein, (a) is a schematic diagram of the crystal structure and (b) is a schematic diagram of Li transport at different sites. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0034] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0035] To address at least one of the problems of high grain boundary impedance, limited lithium-ion transport capacity, and poor interface stability in traditional LATP solid electrolytes, this invention provides a method for preparing a cobalt and bismuth co-doped solid electrolyte.

[0036] The method for preparing a cobalt and bismuth co-doped solid electrolyte according to an embodiment of the present invention includes the following steps: (1) mixing LiNO3, , Mix NH4H2PO4 with water to obtain solution A; then mix Ti(OC4H9)4 and... Dissolve in citric acid solution according to stoichiometric ratio, add ammonia as catalyst, heat and stir evenly (this step helps to fully dissolve tetrabutyl titanate; avoids hydrolysis of tetrabutyl titanate; the reaction is more uniform, and the high temperature promotes the reaction of tetrabutyl titanate and citric acid to generate titanium citrate), to obtain solution B; (2) add solution A dropwise to solution B, stir and mix evenly; after the dropwise addition is completed, adjust the pH to 7, add dispersant, stir to obtain precursor solution; (3) heat the precursor solution to obtain wet gel, dry the wet gel to obtain dry gel, calcine the dry gel to obtain cobalt and bismuth doped solid electrolyte LATP-CoBi.

[0037] In a preferred embodiment of the method for preparing the cobalt and bismuth co-doped solid electrolyte of the present invention, the stoichiometric ratio of Li, Al, Ti, Co and Bi in the cobalt and bismuth co-doped solid electrolyte LATP-CoBi is 1.4:(0.4-x):1.2:0.4:x; where x=0.01-0.04.

[0038] Preferably, x = 0.03.

[0039] In a preferred embodiment of the method for preparing the cobalt and bismuth co-doped solid electrolyte of the present invention, in step (3), the calcination temperature is 750-900℃ (e.g., 750℃, 800℃, 850℃ or 900℃), and the calcination time is 3.8-4.2h (e.g., 3.8h, 3.9h, 4.0h, 4.1h or 4.2h). If the calcination temperature is too high or the calcination time is too long, lithium volatilization will occur, resulting in product loss or the formation of impurity phases; if the calcination temperature is too low, incomplete combustion will also generate impurity phases.

[0040] In a preferred embodiment of the method for preparing the cobalt and bismuth co-doped solid electrolyte of the present invention, in step (3), the heating temperature is 75-85℃ (e.g., 75℃, 78℃, 80℃, 82℃ or 85℃), the heating time is 14-16h (e.g., 14h, 14.5h, 15h, 15.5h or 16h), and stirring is carried out continuously during the heating process; the drying temperature is 100-130℃ (e.g., 100℃, 110℃, 120℃ or 130℃), and the drying time is 3-6h (e.g., 3h, 4h, 5h or 6h). If the heating time is too short, it is difficult to form a gel; if the heating time is too long, the fluidity is poor and it is difficult to peel off.

[0041] In a preferred embodiment of the method for preparing the cobalt and bismuth co-doped solid electrolyte of the present invention, in step (1), after adding ammonia water, the mixture is heated at 65-75°C (e.g., 65°C, 68°C, 70°C, 72°C or 75°C) for 0.8-1.2h (e.g., 0.8h, 0.9h, 1.0h, 1.1h or 1.2h); in step (2), the dispersant is ethylene glycol.

[0042] The present invention also proposes a cobalt and bismuth co-doped solid electrolyte, which is prepared by the method described above in the embodiments of the present invention.

[0043] The present invention also proposes a method for preparing a solid electrolyte membrane. The method for preparing a solid electrolyte membrane according to an embodiment of the present invention further includes the following steps: I. Mixing polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide and solvent evenly to obtain solution C; II. Mixing and stirring the cobalt and bismuth co-doped solid electrolyte as described above with solution C to obtain a composite slurry; III. Placing the composite slurry in a mold and drying it to obtain a solid electrolyte membrane.

[0044] In a preferred embodiment of the method for preparing the solid electrolyte membrane of the present invention, the mass ratio of polyethylene oxide to the cobalt and bismuth co-doped solid electrolyte is 1:(0.5-1) (e.g., 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1), and the mass of lithium bis(trifluoromethanesulfonyl)imide is 7%-7.5% of the polyethylene oxide (e.g., 7%, 7.1%, 7.2%, 7.3%, 7.4% or 7.5%). In step I, the solvent is acetonitrile, and the mixture is continuously stirred at 50-60°C (e.g., 50°C, 52°C, 54°C, 56°C, 58°C or 60°C) for 3-5 hours (e.g., 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1). The mixture is homogenized under conditions such as 3h, 4h, or 5h; in step II, the mixing and stirring time is 5-6h (e.g., 5h, 5.5h, or 6h); in step III, the drying temperature is 70-80℃ (e.g., 70℃, 72℃, 74℃, 76℃, 78℃, or 80℃), and the drying time is 12-18h (e.g., 12h, 13h, 14h, 15h, 16h, 17h, or 18h), and after drying, the solvent is slowly evaporated at room temperature for 12-14h (e.g., 12h, 13h, or 14h); the thickness of the solid electrolyte membrane is 300-500μm.

[0045] The present invention also proposes a solid electrolyte membrane, which is prepared by the method described above in the embodiments of the present invention.

[0046] The present invention also proposes a solid-state battery, wherein the solid-state battery of the present invention uses a cobalt and bismuth dual-doped solid electrolyte as described above; or, the solid-state battery uses a solid electrolyte membrane as described above.

[0047] The cobalt and bismuth co-doped solid electrolyte of the present invention, its preparation method, and its application are described in detail below through specific embodiments.

[0048] The sources of the main raw materials used in the following embodiments are shown in Table 1 below: Table 1

[0049] Example 1 The cobalt and bismuth co-doped solid electrolyte of this invention is prepared by the sol-gel method, including the following steps: (1) Add 1.36g LiNO3 and 1.77g 1.485g 4.401g of NH4H2PO4 was mixed thoroughly with 100mL of deionized water to obtain solution A; 5.21g of Ti(OC4H9)4 and 0.186g of... Dissolve in 7 mL of 50 wt% citric acid solution, add 1 mL of ammonia water as a catalyst, heat at 70 °C for 1 h while stirring until homogeneous (heating helps promote the reaction of tetrabutyl titanate and citric acid to form titanium citrate), to obtain solution B; in this solution, excess LiNO3 is added to compensate for the Li precipitate reaction during calcination. + Lithium loss due to volatilization (the amounts of all other raw materials are weighed according to stoichiometric ratios).

[0050] (2) Slowly add solution A to solution B using a peristaltic pump and stir continuously to make it evenly mixed; after the addition is complete, adjust the pH of the mixed solution to 7 with ammonia water, add 10 mL of ethylene glycol as a dispersant (which helps to improve the particle fineness of the cobalt and bismuth doped solid electrolyte obtained by subsequent calcination), and continue stirring for 1 h to obtain a white LATP precursor solution.

[0051] (3) The precursor solution was heated (heated to 80℃ and stirred for 15h) to obtain a wet gel. The wet gel was dried (placed in a drying oven and dried at 130℃ for 4h) to obtain a dry gel. The dry gel was placed in an alumina crucible, compacted, and calcined in a muffle furnace at 800℃ for 4h. After cooling, it was ball-milled through a 300-mesh sieve to obtain the cobalt and bismuth co-doped solid electrolyte LATP-Co of this embodiment. 0.4 Bi 0.03 (i.e., Li) 1.4 Al 0.37 Bi 0.03 Ti 1.2 Co 0.4 (PO4)3).

[0052] The solid electrolyte membrane in this embodiment is prepared by solution casting, including the following steps: I. Dissolve 1.8g of polyethylene oxide (PEO, Mw=600000) and 0.13g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in acetonitrile and stir continuously at 50°C for 4h to obtain a homogeneous and transparent PEO-LiTFSI solution, denoted as solution C. II. Take the 1.36g LATP-Co obtained above. 0.4 Bi 0.03 Slowly add to solution C and stir continuously for 6 hours to ensure that the inorganic powder is uniformly dispersed in the polymer matrix without obvious agglomeration, forming a stable composite slurry; III. Pour the composite slurry evenly into the glass culture dish mold, and control the casting thickness by controlling the volume of the composite slurry; transfer it to an 80℃ vacuum drying oven and continue drying for 12 hours, then slowly evaporate the solvent at room temperature for 14 hours to completely remove the residual solvent, and obtain a solid electrolyte membrane with certain flexibility and mechanical strength (the membrane thickness is controlled at about 300-500μm). Cut it into 16mm diameter round slices with a slicer and store it in a glove box.

[0053] The solid electrolyte membrane in this embodiment is designated as PEO-LATP-Co. 0.4 Bi 0.03 .

[0054] Example 2 The only difference between this embodiment and Embodiment 1 is that: The dosage was 0.062g; all other aspects remained the same as in Example 1.

[0055] The cobalt- and bismuth-doped solid electrolyte in this embodiment is denoted as LATP-Co. 0.4 Bi 0.01 (i.e., Li) 1.4 Al 0.39 Bi 0.01 Ti 1.2 Co 0.4 (PO4)3).

[0056] The solid electrolyte membrane in this embodiment is designated as PEO-LATP-Co. 0.4 Bi 0.01 .

[0057] Example 3 The only difference between this embodiment and Embodiment 1 is that: The dosage was 0.124g; all other aspects remained the same as in Example 1.

[0058] The cobalt- and bismuth-doped solid electrolyte in this embodiment is denoted as LATP-Co. 0.4 Bi 0.02 (i.e., Li) 1.4 Al 0.38 Bi 0.02 Ti 1.2 Co 0.4 (PO4)3).

[0059] The solid electrolyte membrane in this embodiment is designated as PEO-LATP-Co. 0.4 Bi 0.02 .

[0060] Example 4 The only difference between this embodiment and Embodiment 1 is that: The dosage was 0.248g; all other aspects remained the same as in Example 1.

[0061] The cobalt- and bismuth-doped solid electrolyte in this embodiment is denoted as LATP-Co. 0.4 Bi 0.04 (i.e., Li) 1.4 Al 0.36 Bi 0.04 Ti 1.2 Co 0.4 (PO4)3).

[0062] The solid electrolyte membrane in this embodiment is designated as PEO-LATP-Co. 0.4 Bi 0.04 .

[0063] Comparative Example 1 The only difference between this comparative example and Example 1 is that solution B in step (1) does not contain... (Adding to solution A) corresponding stoichiometric ratio ); and in solution A The dosages were set to 0.743g, 1.485g and 2.228g respectively, and the dosage of Ti(OC4H9)4 was adjusted accordingly; all other aspects remained the same as in Example 1.

[0064] The solid electrolyte in this comparative example is denoted as LATP-Co. 0.2 LATP-Co 0.4 Bi0, LATP-Co 0.6 (i.e., Li) 1.4 Al 0.4 Ti 1.4 Co 0.2 (PO4)3, Li 1.4 Al 0.4 Ti 1.2 Co 0.4 (PO4)3, Li 1.4 Al 0.4 Ti1Co 0.6 (PO4)3).

[0065] Accordingly, the solid electrolyte membrane of this comparative example is designated as PEO-LATP-Co. 0.2 ,PEO-LATP-Co 0.4 Bi0, PEO-LATP-Co 0.6 .

[0066] Comparative Example 2 The only difference between this comparative example and Example 1 is that solution A does not contain... And solution B does not contain (Adding to solution A) corresponding stoichiometric ratio Adding to solution B The corresponding stoichiometric ratio of Ti(OC4H9)4); all other values ​​remain the same as in Example 1.

[0067] The solid electrolyte in this comparative example is denoted as LATP (i.e., Li). 1.4 Al 0.4 Ti 1.6 (PO4)3).

[0068] The solid electrolyte membrane used in this comparative example is denoted as PEO-LATP.

[0069] Comparative Example 3 Li in this comparative example 1.4 Al 0.4 Ti 1.6-x Sn x (PO4)(LATP-Sn x Preparation of solid electrolyte powder: The only difference between the preparation of solution A and that of Example 1 is that: (omitted) ; The preparation of solution B differs from that in Example 1 only in that: Ti(OC4H9)4 is added to a 50% citric acid solution, 2 mL of ammonia is added as a catalyst, and the mixture is heated at 70°C for 1 hour with thorough stirring until homogeneous. Then, stannous chloride solutions with different stoichiometric ratios (x = 0.1, 0.3, 0.5; corresponding stannous chloride masses are 0.289 g, 0.839 g, and 1.351 g, respectively) are added and denoted as solution B. The remaining steps are the same as in Example 1.

[0070] The solid electrolytes prepared in this comparative example are denoted as LATP-Sn. 0.1 LATP-Sn 0.3 LATP-Sn 0.6 ; Solid electrolyte membranes were prepared using the same method as in Example 1. The solid electrolyte membranes prepared in this comparative example are denoted as PEO-LATP-Sn sequentially. 0.1 PEO-LATP-Sn 0.3 PEO-LATP-Sn 0.6 .

[0071] Experimental Example I. Structural and Chemical State Characterization: 1. Crystal structure and phase composition analysis: LATP-Co with different Bi doping levels 0.4 Bi x(x=0.01, 0.02, 0.03, 0.04) and LATP-Co 0.4 The XRD pattern of Bi0 is as follows: Figure 1 As shown; Depend on Figure 1 It can be seen that: LATP-Co 0.4 Bi0 (Comparative Example 1) and LATP-Co with different Bi doping levels 0.4 Bi x (LATP-Co 0.4 Bi 0.01 LATP-Co 0.4 Bi 0.02 LATP-Co 0.4 Bi 0.03 LATP-Co 0.4 Bi 0.04 The XRD pattern of the powder sample matched the LATP standard PDF card, conforming to the typical NASICON-type crystal structure characteristics, and no obvious impurity phase diffraction peaks were observed. The Co and Bi co-doped sample (LATP-Co) 0.4 Bi x The original LATP basic crystal structure was maintained. In the magnified view of the diffraction angle in the 24°-25° region, as the stoichiometric coefficient of Bi doping increases, the characteristic diffraction peak at 24.3° gradually shifts to lower angles. This is determined by Bragg's diffraction law, and the reason is that the large-radius Bi... 3+ (Ionic radius 103 pm) Upon entering the LATP lattice, it induces lattice expansion, forming a homogeneous solid solution; LATP-Co 0.4 Bi 0.03 The sample showed a significant shift in peak position and a relatively sharp peak shape, indicating that moderate Bi doping can effectively alter lattice parameters without affecting crystallization, thus benefiting Li. + Migration; LATP-Co 0.4 Bi 0.04 The peak shape of the sample is broadened to a certain extent, and the crystallinity is reduced, which may be due to the accumulation of lattice stress or the increase of local disorder caused by excessive Bi doping.

[0072] 2. Microscopic morphology and elemental distribution analysis: LATP-Co 0.4 Bi 0.03 The microstructure and elemental surface scans of the powder are as follows: Figure 2 As shown; where (a) is the SEM image, (b) is the surface scan of Al element, (c) is the surface scan of Ti element, (d) is the surface scan of Co element, and (e) is the surface scan of Bi element.

[0073] from Figure 2 LATP-Co can be observed in (a). 0.4Bi 0.03 The powder exhibits a cubic polyhedral morphology with a uniform particle size distribution (1-3 μm) and no particle agglomeration. Overall, the particle size distribution is relatively better than that of the undoped (LATP) and single-doped Co samples (LATP-Co). 0.2 LATP-Co 0.4 Bi0, LATP-Co 0.6 The particles are more regular and have a more uniform size distribution (LATP, LATP-Co). 0.2 LATP-Co 0.4 Bi0 and LATP-Co 0.6 The SEM images are as follows: Figure 3 (as shown in (a), (b), (c) and (d)).

[0074] LATP-Co 0.4 Bi 0.03 Elemental surface scan of the particles (( Figure 2 (b)-(e) show that Al, Ti, Co, and Bi elements are uniformly distributed in the particles, with no element segregation or enrichment at the interface. This confirms that Bi and Co elements are co-doped and successfully introduced into the LATP lattice in an ionic state and dispersed at the atomic level, which can ensure the uniformity of ion conduction paths in the composite electrolyte on a macroscopic scale.

[0075] 3. Surface chemical state and elemental valence state analysis: LATP-Co 0.4 Bi 0.03 The fine XPS spectrum of the sample is as follows Figure 4 As shown. Among them, Figure 4 (a) is the total spectrum; O 1s spectrum ( Figure 4 (b) can be fitted with two peaks: lattice oxygen (531.5 eV) and adsorbed oxygen (532.8 eV), indicating that a small amount of adsorbed oxygen exists on the sample surface, while the main body remains a stable lattice oxygen environment. Al 2p spectrum ( Figure 4 (c) exhibits a single characteristic peak, corresponding to Al 3+ The typical chemical state of Al, compared with Co doping, shows a shift in the characteristic peaks of Al, confirming that although most of Al retains its +3 valence after double doping, some may still be replaced by Bi; this experimental result confirms that Bi doping replaces Al sites rather than replacing Ti sites together with Co. Ti 2p spectrum ( Figure 4 (e) can be fitted as (458.8eV) and Two peaks (464.5 eV) correspond to Ti. 4+ The characteristic spin orbital splitting indicates that Ti retains its +4 valence even after double doping. Co 2p spectrum ( Figure 4 (d) can be fitted to Co2+ With Co 3+ The mixed valence state is consistent with the results of Co single doping, which verifies that Bi doping into Al sites does not change the lattice environment of Ti. Bi 4f spectrum ( Figure 4 (f) can be fitted as (164.2 eV) and Two peaks (158.9 eV) correspond to Bi. 3+ The characteristic chemical state of Bi confirms that Bi enters the LATP lattice in the +3 valence form, maintaining the lattice charge balance through the valence state compensation mechanism, while inducing stronger lattice distortion.

[0076] 4. Solid-state nuclear magnetic resonance (NMR) analysis: Solid-state nuclear magnetic resonance spectrum as shown Figure 5 As shown; where (a) is LATP Solid-state NMR spectrum, (b) is LATP-Co 0.4 Bi 0.03 powder Solid-state nuclear magnetic resonance spectrum.

[0077] LATP and LATP-Co 0.4 Bi 0.03 powder Solid-state NMR spectroscopy results can be fitted using MestReNova software to Li1 (low energy field, representing high-symmetry Li sites in the lattice) and Li2 (high energy field, representing Li sites in defect or distortion environments). Different Li sites correspond to the easily movable Li2 and the Li1, which requires a larger activation energy to move. In the pure LATP sample (Comparative Example 2), the Li2 component is relatively low, indicating that most Li sites have high symmetry and weak lattice distortion; in LATP-Co... 0.4 Bi 0.03 The significantly increased proportion of Li2 component in the sample indicates that the co-doping of Co and Bi led to stronger lattice distortion and Li site environment differentiation, thereby promoting Li... + The local disorder and mobility of the ions provide a structural basis for improving ionic conductivity.

[0078] The above characterization techniques, including XRD, NMR, SEM-EDS, and XPS, systematically analyzed the regulatory mechanism of Co and Bi dual doping on the microstructure and chemical state of LATP solid electrolyte. Compared with the Co single-doped system, Co and Bi dual doping achieves stronger lattice control and Li site differentiation while maintaining structural stability. Moreover, the mechanism of dual doping differs from that of Co single doping; Bi substitutes Al sites to excite mobile active Li sites, thereby achieving the goal of macroscopically improving the ionic conductivity of the electrolyte.

[0079] II. Effects of Co and Bi co-doping on the properties and structure of LATP solid electrolyte membranes: 1. Macroscopic morphology and appearance characteristics: PEO-LATP-Co 0.4 Bi 0.03 Optical photographs of solid electrolyte membranes, such as Figure 6 As shown in (i); in the figure, PEO-LATP-Co 0.4 Bi 0.03 The uniform color, smooth surface, and light purple appearance of the solid electrolyte membrane are due to the presence of Co, which directly confirms the successful introduction of Co into the composite electrolyte structure and also reflects the macroscopic characteristics of the inorganic filler LATP-Co. 0.4 Bi 0.03 The electrolyte membrane is uniformly dispersed in the PEO polymer matrix without phase separation or particle agglomeration, thus meeting the basic requirements for macroscopic uniformity of the electrolyte membrane in solid-state battery assembly.

[0080] 2. Analysis of microstructure and elemental distribution uniformity: PEO-LATP-Co 0.4 Bi 0.03 SEM and surface scan images of solid electrolyte membranes are as follows: Figure 6 As shown in (a)-(h); where (a) is a surface SEM image, (b) is a surface scan of the Ti element in Figure (a), (c) is a surface scan of the Co element in Figure (a), (d) is a surface scan of the Bi element in Figure (a), (e) is a cross-sectional SEM image, (f) is a surface scan of the Ti element in Figure (e), (g) is a surface scan of the Co element in Figure (e), and (h) is a surface scan of the Bi element in Figure (e).

[0081] From the perspective of surface morphology ( Figure 6 (a) The surface of the solid electrolyte membrane is dense without pores. A small number of wrinkles and protrusions in the PEO film formation are normal. LATP-Co 0.4 Bi 0.03 The powder is uniformly dispersed at the nanoscale within the PEO polymer matrix, together forming a continuous and defect-free microstructure. Cross-sectional morphology ( Figure 6 (e) It exhibits a dense structure with a thickness of approximately 300 μm and no obvious pores or cracks. The polymer matrix (PEO) and inorganic filler (LATP-Co) are combined. 0.4 Bi 0.03 The tightly bonded structure, without interfacial delamination, effectively suppresses lithium dendrite penetration, enhancing the battery's applicability. Elemental surface scans show that Ti, Co, and Bi exhibit uniform dotted distributions on both the surface and cross-section of the solid electrolyte membrane, with no obvious enrichment or agglomeration regions. Ti, in particular, acts as a key element in LATP-Co...0.4 Bi 0.03 The main elements are shown throughout the region, reflecting the inorganic filler (LATP-Co). 0.4 Bi 0.03 The global dispersion of Co and Bi elements in the polymer matrix; the distribution of Co and Bi elements coincides with that of Ti elements, confirming the presence of dual dopants in LATP-Co. 0.4 Bi 0.03 No separation occurred; instead, it followed LATP-Co. 0.4 Bi 0.03 The filler is uniformly dispersed in the PEO matrix, demonstrating that the dual-doped powder prepared by the sol-gel method (the method of this invention) has excellent compatibility with the PEO polymer matrix, which is beneficial to Li + A continuous transport channel is formed in the solid electrolyte membrane.

[0082] 3. Analysis of thermal properties and crystallization behavior regulation: The effects of Co and Bi co-doping on the crystallization behavior of PEO can be analyzed by examining the changes in melting temperature (Tm) and melting peak morphology. Figure 7 For PEO-LATP, PEO-LATP-Co 0.4 Bi0 and PEO-LATP-Co 0.4 Bi 0.03 DSC curves of three solid electrolyte membranes. The figure shows that the Tm of the undoped PEO-LATP solid electrolyte membrane is 60.0℃; the Tm of the Co-doped PEO-LATP-Co membrane is... 0.4 The Tm of the BiO solid electrolyte membrane decreased to 56.1℃; however, after the introduction of Bi, the Tm of the PEO-LATP-Co membrane decreased. 0.4 Bi 0.03 The Tm of the solid electrolyte membrane further decreased to 50.8℃, and the intensity of the melting peak was significantly weakened and the peak shape tended to be broadened.

[0083] The continuous decrease in melting temperature and the weakening of the melting peak intensity are due to the inhibitory effect of Co and Bi co-doping on the crystallization behavior of PEO. The core mechanism lies in: LATP-Co... 0.4 Bi 0.03 As physical crosslinking points, they form stronger interactions with PEO molecular chains, disrupting the regular arrangement of PEO molecular chains and reducing their crystallinity. This reduction in crystallinity increases the proportion of amorphous regions in PEO, enhances the mobility of polymer chain segments, and thus optimizes Li₂ under room temperature conditions. + Transport dynamics in polymer matrix. Figure 7In the study, no obvious thermal decomposition peaks were observed in any of the three solid electrolyte membranes, indicating that the co-doping of Co and Bi did not reduce the thermal stability of the solid electrolyte. Its melting behavior remained within the normal operating temperature range of the solid battery, thus balancing thermal stability and ion transport performance.

[0084] In other words, Co and Bi dual doping, while ensuring good film-forming properties, microstructure uniformity and thermal stability of the solid electrolyte membrane, optimizes the ion transport environment of the polymer matrix by suppressing PEO crystallization. Combined with the adjustment of the LATP lattice structure by Co and Bi dual doping mentioned above, performance improvement is achieved from two aspects: modification of the inorganic filler lattice and control of polymer matrix crystallization.

[0085] III. Electrochemical Performance Testing: 1. Electrochemical impedance and ionic conductivity: PEO-LATP-Co 0.4 Bi0, PEO-LATP-Co 0.4 Bi 0.01 ,PEO-LATP-Co 0.4 Bi 0.02 ,PEO-LATP-Co 0.4 Bi 0.03 and PEO-LATP-Co 0.4 Bi 0.04 The electrochemical impedance and ionic conductivity test results are as follows: Figure 8 As shown ( Figure 8 The abbreviations are LATP-Co in sequence. 0.4 Bi0, LATP-Co 0.4 Bi 0.01 LATP-Co 0.4 Bi 0.02 LATP-Co 0.4 Bi 0.03 and LATP-Co 0.4 Bi 0.04 (a) shows the electrochemical impedance spectroscopy results, and (b) shows the ionic conductivity results.

[0086] Figure 8 In (a), PEO-LATP-Co with different Bi doping amounts 0.4 Bi x The solid electrolyte membrane samples (x=0, 0.01, 0.02, 0.03, 0.04) all exhibited typical characteristics of a high-frequency semicircle (representing bulk impedance) and a low-frequency oblique line (representing ion diffusion). As the Bi doping concentration increased, the diameter of the high-frequency semicircle first decreased and then increased; among them, PEO-LATP-Co... 0.4 Bi 0.03The sample has the smallest semicircular diameter because it has the lowest bulk impedance; excessive Bi doping (x=0.04) may cause the semicircular diameter to increase again, and the impedance to increase.

[0087] Combination Figure 8 (b) Quantitative calculation results of ionic conductivity, PEO-LATP-Co 0.4 Bi0, PEO-LATP-Co 0.4 Bi 0.01 ,PEO-LATP-Co 0.4 Bi 0.02 ,PEO-LATP-Co 0.4 Bi 0.03 ,PEO-LATP-Co 0.4 Bi 0.04 The room temperature ionic conductivity is 1.23 × 10⁻⁶. -4 S / cm, 3.35×10 -5 S / cm, 2.19×10 -5 S / cm, 1.49×10 -4 S / cm, 7.35×10 -5 S / cm. PEO-LATP-Co 0.4 Bi 0.03 The electrical conductivity is relatively high, compared to the Co single-doped system (PEO-LATP-Co). 0.4 Bi0) increased by 21.1% (the same method was used to compare PEO-LATP and PEO-LATP-Co). 0.2 ,PEO-LATP-Co 0.6 The conductivity was tested, and the results were 3.73 × 10⁻⁶. -5 S / cm, 6.91×10 -5 S / cm, 3.30×10 -5 S / cm), which is also superior to the Sn single-doped system (PEO-LATP-Sn measured using the same method). 0.1 PEO-LATP-Sn 0.3 PEO-LATP-Sn 0.5 The electrical conductivity is 3.98 × 10⁻⁶. -5 S / cm, 4.97×10 -5 S / cm, 2.59×10 -5 S / cm). This improvement is due to the synergistic effect of Co and Bi co-doping: on the one hand, Bi... 3+ Induced lattice expansion further facilitates On the other hand, the Co and Bi co-doped powders, acting as physical cross-linking points, effectively suppressed PEO crystallization, increased the proportion of amorphous regions and chain segment mobility in PEO, and together optimized the transport; Transport kinetics. Excessive Bi doping (x=0.04) may hinder Li transport due to the accumulation of granular stress and increased disorder. + Transmission causes a slight decrease in conductivity.

[0088] 2. Electrochemical stability window and reversibility: LSV comparison chart and CV curve as follows: Figure 9 As shown; where (a) is PEO-LATP-Co 0.4 Bi0, PEO-LATP-Sn 0.3 PEO-LATP and PEO-LATP-Co 0.4 Bi 0.03 LSV comparison diagram, (b) is PEO-LATP-Co 0.4 Bi 0.03 The CV curve.

[0089] LSV can be used to assess the electrochemical stability window of an electrolyte. Figure 9 (a) The limiting oxidation potential of PEO-LATP is 4.75 V, and the Co single-doped (PEO-LATP-Co) 0.4 Bi0) and Sn single doping (PEO-LATP-Sn) 0.3 The voltage was increased to 5.00V, while the Co and Bi dual-doped (PEO-LATP-Co) 0.4 Bi 0.03 The electrochemical window was further increased to 5.22V, which shows that double doping can effectively broaden the electrochemical stability window, enhance the oxidation resistance of the material itself, and make it suitable for high-voltage cathode materials.

[0090] Figure 9 In (b), the positions and intensities of the redox peaks in the first three cycles largely coincide, with the reduction peak potential at approximately 3.536-3.61 V and the oxidation peak potential at approximately 5.791-6.313 V. No significant new peaks were generated or their positions shifted, indicating that the PEO-LATP-Co... 0.4 Bi 0.03 Solid electrolyte membranes exhibit excellent electrochemical reversibility in the voltage range of 2.5-7.0V, with no irreversible side reactions occurring and good structural stability.

[0091] 3. Lithium-ion transference number and interface stability: Figure 10 The graph shows the IT (polarization) curves and the electrochemical impedance spectroscopy before and after IT; where (a) is the PEO-LATP-Co... 0.4 Bi0.02 The IT curve, (b) is the PEO-LATP-Co 0.4 Bi 0.03 The IT curve, (c) is the PEO-LATP-Co 0.4 Bi 0.02 Electrochemical impedance spectroscopy comparison before and after IT, (d) is PEO-LATP-Co 0.4 Bi 0.03 Comparison of electrochemical impedance before and after IT.

[0092] The lithium-ion transport number was calculated by analyzing the changes in electrochemical impedance and steady-state current before and after polarization. PEO-LATP-Co 0.4 Bi 0.02 of It is 0.7252; while PEO-LATP-Co 0.4 Bi 0.03 of The value was increased to 0.9632, which is significantly higher than that of traditional PEO-based electrolytes (typically...). <0.5), which is also superior to the Co single-doped system (PEO-LATP-Co). 0.4 Bi0; calculated using the same method as described above (0.9223) and Sn single-doped system (PEO-LATP-Sn) 0.3 ; Calculated using the same method as above (0.8905). Furthermore, PEO-LATP-Co 0.4 Bi 0.03 The impedance spectra before and after polarization showed only minor changes (less than those of PEO-LATP-Co). 0.4 Bi 0.02 LATP-Co 0.4 Bi0 and PEO-LATP-Sn 0.3 This demonstrates that the electrolyte-lithium metal interface exhibits excellent stability after Co and Bi co-doping, with no significant side reactions or interface deterioration occurring.

[0093] Co and Bi co-doping, while maintaining good structure and thermal stability, improves ionic conductivity, electrochemical stability window and lithium-ion transference number, effectively enhancing the system's performance and demonstrating a more balanced overall electrochemical performance advantage.

[0094] 4. Long-cycle stability and coulombic efficiency analysis: PEO-LATP-Co 0.4 Bi 0.03 Solid electrolyte membrane fabrication Half-cell cycle performance tested at 0.1C rate: Specifically, for the half-cell test, NCM811 was used as the positive electrode active material, acetylene black (SuperP) as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and aluminum foil as the current collector. NCM811, SuperP, and PVDF were weighed in a mass ratio of 8:1:1 and thoroughly mixed in N-methyl-2-pyrrolidone solvent. The resulting mixture was then coated onto a clean, flat aluminum foil and placed in an oven at 120°C for 12 hours. After drying, the electrode sheets were cut into 12mm diameter circular electrode pieces and weighed for later use. The amount of NCM811 active material was approximately 2.0 mg. The battery assembly sequence was: positive electrode shell / spring / pad / positive electrode material (NCM811) / small amount of electrolyte / composite solid electrolyte / Li sheet / negative electrode shell.

[0095] Test results are as follows Figure 11 As shown; Figure 11 The cycle performance curves include both charge / discharge specific capacity and coulombic efficiency. The battery's initial discharge specific capacity at 0.1C is 190 mAh / g. During cycling, the charge / discharge specific capacity gradually decreases, and after 300 cycles, the discharge specific capacity stabilizes at 115 mAh / g, with a capacity retention rate of 60.5%.

[0096] The coulombic efficiency reached 98% in the first week of charge-discharge and remained stable in the 95%-100% range for the subsequent 300 cycles. This indicates that the Co and Bi dual-doped solid electrolyte membrane (PEO-LATP-Co) exhibits excellent performance. 0.4 Bi 0.03 It has good interfacial contact with the NCM811 positive electrode and the lithium metal negative electrode, which can avoid side reactions that may occur during battery cycling (such as the dissolution of positive electrode transition metal, lithium dendrite growth, etc.) and thus ensure the reversible cycling of the battery.

[0097] Undoped (PEO-LATP) and Co-doped (PEO-LATP-Co) 0.4 The performance test results of the Bi0 system half-cell at 0.1C are shown in Table 2 below: Table 2

[0098] Among them, PEO-LATP-Co 0.4 Bi 0.03 The half-cell of the system exhibited a discharge specific capacity of 179 mAh / g after 100 cycles at 0.1C, with a discharge specific capacity retention of 94.2%; Sn single-doped (PEO-LATP-Sn) 0.3 The initial discharge specific capacity of the half-cell of the system was 165 mAh / g when tested at 0.5C, the first-cycle coulombic efficiency was 98%, and the discharge specific capacity retention rate after 150 cycles was 57.6%.

[0099] Compared with undoped (PEO-LATP) and Sn-doped (PEO-LATP-Sn) 0.3 ) and Co single doping (PEO-LATP-Co) 0.4 Compared to the half-cell performance of the Bi0 system, The half-cell exhibits performance advantages such as longer cycle life, higher coulombic efficiency, and higher initial capacity. This is because the dual doping of Co and Bi effectively ensures... While achieving efficient transmission, it reduces interface transmission resistance, effectively delaying the accumulation of interface impedance and capacity decay during cycling.

[0100] IV. Mechanism Analysis: Figure 12 PEO-LATP-Co 0.4 Bi 0.03 A schematic diagram of the crystal structure of a solid electrolyte membrane and a schematic diagram of Li transport at different sites; wherein, (a) is a schematic diagram of the crystal structure and (b) is a schematic diagram of Li transport at different sites.

[0101] like Figure 12 As shown in (a), Co and Bi are respectively incorporated into Ti of LATP. 4+ Al 3+ Following the doping site, the lattice size at the corresponding MO6 octahedron increases, causing a certain degree of lattice distortion. XRD results show that the grain size increases macroscopically after doping. Microscopically, the co-doping of Co and Bi widens the intergranular gaps, thereby broadening the Li... + This channel improves ionic conductivity.

[0102] like Figure 12 As shown in (b) Intergranular motion includes movement between different grain layers and transport within the same grain layer, as shown in the figure. From the migration path, it can be seen that, theoretically Intralayer motion and The inter-layer motion migration path is the shortest, the required migration energy is the smallest, and it is convenient. Transportation. Based on the above NMR test results ( Figure 5 It can be seen that in LATP-Co 0.4 Bi 0.03 The Li2 component had the highest proportion in the samples relative to the undoped (LATP) samples, thus promoting [the development of the sample] to some extent. The migration of ions increases ionic conductivity. In addition, combining the above and the above... Figure 7 DSC analysis showed that the co-doping of Co and Bi simultaneously reduced the crystallinity of PEO, thereby reducing... The transport resistance in PEO, and the two work together to improve macroscopic ionic conductivity by optimizing ion transport in the microscopic bulk phase (LATP) and the interfacial phase (PEO).

[0103] 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 method for preparing a cobalt and bismuth co-doped solid electrolyte, characterized in that, Includes the following steps: (1) LiNO3, , Mix NH4H2PO4 with water to obtain solution A; then mix Ti(OC4H9)4 and... Dissolved in citric acid solution, ammonia water was added as a catalyst, and the mixture was heated and stirred until homogeneous to obtain solution B; (2) Add solution A dropwise to solution B and stir to mix evenly; after the addition is complete, adjust the pH to 7, add dispersant, and stir to obtain precursor solution; (3) The precursor solution is heated to obtain a wet gel, the wet gel is dried to obtain a dry gel, and the dry gel is calcined to obtain the cobalt and bismuth doped solid electrolyte LATP-CoBi. In the cobalt and bismuth co-doped solid electrolyte LATP-CoBi, the stoichiometric ratio of Li, Al, Ti, Co, and Bi is 1.4:(0.4-x):1.2:0.4:x; where x = 0.01-0.

04. In step (1), after adding ammonia water, heat at 70°C for 1 hour; In step (2), the dispersant is ethylene glycol; In step (3), the heating temperature is 80℃ and the heating time is 15h, with continuous stirring during the heating process; the drying temperature is 130℃ and the drying time is 4h; the calcination temperature is 800℃ and the calcination time is 4h.

2. A cobalt and bismuth co-doped solid electrolyte, characterized in that, The cobalt and bismuth co-doped solid electrolyte is prepared using the method described in claim 1; In this process, Bi was incorporated into Al, replacing its position.

3. A method for preparing a solid electrolyte membrane, characterized in that, Includes the following steps: I. Mix polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide and solvent evenly to obtain solution C; II. Mix and stir the cobalt and bismuth dual-doped solid electrolyte as described in claim 2 with the solution C to obtain a composite slurry; III. Place the composite slurry in a mold and dry it to obtain the solid electrolyte membrane; The mass ratio of polyethylene oxide to the cobalt and bismuth co-doped solid electrolyte is 1:(0.5-1); the mass of lithium bis(trifluoromethanesulfonyl)imide is 7%-7.5% of the polyethylene oxide. In step I, the solvent is acetonitrile, and the mixture is homogeneous under continuous stirring at 50-60℃ for 3-5 hours. In step II, the mixing and stirring time is 5-6 hours; In step III, the drying temperature is 70-80℃ and the drying time is 12-18h. After drying, the solvent is slowly evaporated at room temperature for 12-14h. The thickness of the solid electrolyte membrane is 300-500 μm.

4. A solid electrolyte membrane, characterized in that, The solid electrolyte membrane is prepared using the method described in claim 3.

5. A solid-state battery, characterized in that, The solid-state battery uses a cobalt and bismuth dual-doped solid electrolyte as described in claim 2; or, the solid-state battery uses a solid electrolyte membrane as described in claim 4.

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