An iodine-based argyrodite phase solid-state electrolyte with high ionic conductivity and interface stability and a preparation method thereof

Abstract

This invention relates to an iodine-based silver-sulfur germanium mineral-phase solid electrolyte and its preparation method, possessing both high ionic conductivity and interfacial stability, belonging to the field of solid electrolyte technology. The electrolyte is an iodine-based silver-sulfur germanium mineral-phase solid electrolyte Li6PS5I doped with M, Sb, and O elements. The chemical formula of the electrolyte is Li. 6+ a M a Sb b P 1‑a‑b S 5‑c O c I and M are one or more of Si, Ge, and Sn, with 0.1≤a≤0.3, 0.5≤b≤0.65, and 0.1≤c≤0.2. M and Sb elements occupy the P sites of the iodine-based silver-germanium sulfide solid electrolyte Li6PS5I, while oxygen occupies the S sites. The electrolyte is obtained through wet ball milling, pressing, sintering, and quenching. This process improves the ionic conductivity of the iodine-based silver-germanium sulfide solid electrolyte, while also enhancing its interfacial compatibility and cycle stability with lithium metal.

Description

Technical Field

[0001] This invention relates to an iodine-based sulfosilver germanium mineral phase solid electrolyte with both high ionic conductivity and interfacial stability, and its preparation method, belonging to the field of solid electrolyte technology. Background Technology

[0002] Traditional liquid lithium-ion batteries are limited by their flammable and volatile organic electrolyte systems, facing unavoidable risks of thermal runaway and leakage, and their energy density is constantly approaching its theoretical limit. In contrast, all-solid-state batteries using solid electrolytes have advantages in safety, energy density, and wide temperature range operation, and are widely recognized as the mainstream technology for next-generation high-energy-density power batteries. Among them, iodine-based silver sulfide germanium ore electrolyte (general formula Li6PS5I) is considered a highly promising candidate material for commercialization due to its economical and controllable synthesis route and good compatibility with lithium metal anodes.

[0003] Despite the significant potential of iodine-based silver-germanium sulfide phase electrolytes, compared to chloride-based (Li6PS5Cl) and bromine-based (Li6PS5Br) electrolytes, iodine-based electrolytes, while theoretically exhibiting better electrochemical stability for metallic lithium, typically exhibit extremely low measured room-temperature ionic conductivity (<10). -2 mS cm -1 While introducing large-radius cations at P-sites can disrupt the order of the anion sublattice and improve lithium-ion mobility, the relevant components are more prone to reduction reactions under strong lithium-metal reducing environments, leading to electron permeation and exacerbating local lithium deposition. Under long-term cycling or high current density conditions, the coupling of electron permeation and ion migration promotes preferential lithium growth at grain boundaries or defects, increasing the risk of dendrite penetration and "soft short circuits."

[0004] Furthermore, improper control of element doping amount and synthesis process during electrolyte doping can easily lead to problems such as uneven distribution of doping elements, local enrichment, impurity phase formation and grain boundary weakening, which in turn affect the electrochemical stability and cycle life of the electrolyte. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an iodine-based silver-germanium ore phase solid electrolyte with both high ionic conductivity and interfacial stability, and a method for preparing the same.

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

[0007] An iodine-based silver-germanium sulfide phase solid electrolyte exhibiting both high ionic conductivity and interfacial stability is proposed. The electrolyte is a solid electrolyte Li₆PS₅I doped with M, Sb, and O elements. The chemical formula of the electrolyte is Li₂. 6+ a Ma Sb b P 1-a-b S 5-c O c I and M are one or more of Si, Ge and Sn, with 0.1≤a≤0.3, 0.5≤b≤0.65, and 0.1≤c≤0.2; M and Sb elements occupy the P sites of the iodine-based silver-germanium sulfide mineral phase solid electrolyte Li6PS5I, and oxygen element occupies the S sites; the electrolyte is obtained by wet ball milling, pressing, sintering and quenching.

[0008] Preferably, 0.15≤a≤0.20, 0.55≤b≤0.60, and 0.12≤c≤0.18.

[0009] A method for preparing an iodine-based silver-germanium sulfide phase solid electrolyte with both high ionic conductivity and interfacial stability, as described in this invention, includes the following steps:

[0010] (1) In an inert atmosphere, weigh the raw materials Li2S, LiI, Sb2S3, P2S5, S, Li2O and M elemental raw materials according to the stoichiometric ratio. The M elemental raw material is MS2 or elemental M. After mixing the raw materials evenly, add a non-polar organic solvent for wet ball milling, and then vacuum dry to remove the solvent to obtain the precursor powder. (2) In an inert atmosphere, the precursor powder is pressed into a blank and sintered in a closed state. After sintering, it is immediately quenched to cool the sample instantaneously from the sintering temperature, thus obtaining an iodine-based silver-germanium ore phase solid electrolyte with both high ionic conductivity and interfacial stability.

[0011] Preferably, in step (1), the inert gas is argon or helium.

[0012] Preferably, in step (1), the non-polar organic solvent is one or more of p-xylene, n-heptane, and n-hexane.

[0013] Preferably, in step (1), the liquid-to-solid ratio of the wet ball milling is 1.0~2.0 mL g. -1 .

[0014] Preferably, in step (1), the rotation speed of the wet ball mill is 550~600 rpm and the time is 15~20 h.

[0015] Preferably, in step (1), the ball-to-material ratio of wet ball milling is (15~25):1.

[0016] Preferably, in step (2), the heating rate during sintering is 3~8 °C min. -1 .

[0017] Preferably, in step (2), the pressing pressure is 350~650 MPa and the pressing time is 2~3 min.

[0018] Preferably, in step (2), sintering includes a low-temperature sintering stage and a high-temperature sintering stage; the temperature of the low-temperature sintering stage is 200~300 °C and the holding time is 4~6 h, and the temperature of the high-temperature sintering stage is 450~550 °C and the holding time is 4~8 h.

[0019] Preferably, in step (2), the quenching process involves rapidly placing the solid electrolyte after sintering into a high thermal conductivity metal heat dissipation mold pre-cooled to -20~0 °C, so that the electrolyte rapidly cools from the sintering temperature to room temperature. More preferably, the pre-cooling temperature is -10~0 °C, and the mold material is copper or oxygen-free copper.

[0020] An all-solid-state lithium metal battery, the battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode; the material of the solid electrolyte layer comprises the iodine-based silver-germanium sulfide phase solid electrolyte described in this invention, which combines high ionic conductivity and interfacial stability.

[0021] A method for preparing an all-solid-state lithium metal battery, the method comprising the following steps: (a) In an inert atmosphere, the positive electrode active material, the solid electrolyte and the conductive agent described in this invention are ground and mixed until they are evenly dispersed to obtain composite positive electrode powder.

[0022] (b) In a solid-state battery mold, the solid electrolyte powder described in this invention is weighed and spread evenly, and pressure is applied to press it into a sheet; then, the composite positive electrode powder obtained in step (a) is evenly spread on one side of the solid electrolyte layer, pressure is applied for the first time to press it, and finally, a lithium indium alloy sheet is added to the other side of the solid electrolyte layer, pressure is applied for the second time to press it for encapsulation, and an all-solid-state lithium metal battery is obtained.

[0023] Preferably, in step (a), the inert gas is argon or helium.

[0024] Preferably, in step (a), the positive electrode active material is selected from LiNi. 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 One of O2 and LiCoO2.

[0025] Preferably, in step (a), the conductive agent is selected from one or more of acetylene black, Ketjen black, carbon nanotubes, or vapor-grown carbon fibers.

[0026] Preferably, in step (a), the mass ratio of the positive electrode active material, the solid electrolyte, and the conductive agent is 70~80:15~25:2~5.

[0027] Preferably, in step (b), the pressure of pressing the solid electrolyte is 250~400 MPa.

[0028] Preferably, in step (b), the first applied pressure is 350~450 MPa.

[0029] Preferably, in step (b), the second applied pressure is 50~200 MPa.

[0030] Beneficial effects In this invention, M and Sb elements jointly perform synergistic substitution at P sites to enhance the host lattice perturbation, regulate the local coordination environment, and improve Li. + Migration conditions are used to improve the bulk ion transport performance of the material. The M element is used to introduce additional Li. + And by adjusting the lattice space, it promotes the growth of Li + Sb is used to further enhance structural perturbation and disorder tendencies, but the amount of Sb introduced needs to be controlled within an appropriate range. When the Sb doping amount is too low, its regulatory effect on the host lattice is limited and it is difficult to significantly improve the ion migration conditions. When the Sb doping amount is too high, it is easy to exceed the stable solid solution capacity of the host lattice, which can lead to local enrichment, phase segregation or precipitation of secondary phases during sintering and cooling.

[0031] Building upon the synergistic doping of P-sites, this invention further introduces oxygen (O) to partially substitute S-sites. The introduction of O helps form local structural units with stronger bond energy, improving lattice framework stability and electronic insulation properties. During cycling in contact with the lithium metal anode, it promotes the formation of an electronically insulating interfacial protective layer, reducing interfacial side reactions and suppressing lithium dendrite-induced uneven deposition. The amount of O doping is also controlled within an appropriate range; when the O doping amount is too low, it is difficult to fully exert its improving effects on interfacial stabilization and electron blocking; when the O doping amount is too high, it may damage the original ion transport network and increase the difficulty of phase formation. Therefore, this invention, through the synergistic control of Sb and O doping amounts, enables the material to achieve both high bulk ion transport capability and good lithium interface stability.

[0032] Since this invention relates to a multi-component synergistic doping system of M, Sb, and O, the components differ in particle size, reactivity, diffusion behavior, and solid solution capability. If only conventional preparation processes are used, localized overheating, powder agglomeration, and micro-region segregation can easily occur during the precursor mixing stage; incomplete reaction, uneven doping, and residual secondary phases can occur during the sintering stage; and redistribution of dopants, phase segregation, and reordering of anionic sublattices can occur during the cooling stage, thereby weakening the doping modification effect. To ensure that the structural design corresponding to the appropriate doping amount is realized and preserved, this invention further constructs a preparation process that matches the doping system.

[0033] Specifically, in the precursor preparation stage, this invention employs a wet ball milling process. By ball milling in the presence of a non-polar organic solvent, the wetting, dispersing, and heat transfer effects of the liquid medium are utilized to improve the dispersion uniformity of the M source, Sb source, and O source in the precursor, and to reduce the localized instantaneous high temperature and powder agglomeration phenomena in dry ball milling. This provides a foundation for the uniform solid solution of each dopant element during the subsequent sintering process.

[0034] In the sintering stage, this invention employs a stepwise sintering process. Stepwise sintering includes a low-temperature sintering stage and a high-temperature sintering stage. The low-temperature stage promotes the initial reaction of the precursor and the formation of a relatively uniform pre-phase state, while the high-temperature stage further completes the formation of the target silver-germanium sulfide phase and the diffusion and solid solution of M, Sb, and O elements to the lattice sites. Through stepwise sintering, the risks of local segregation, unreacted residues, and secondary phase precipitation in the multi-component doped system can be reduced, ensuring that the target structure corresponding to the appropriate Sb and O doping levels is fully established in the high-temperature stage.

[0035] After sintering, the present invention further employs a quenching treatment. This quenching treatment is used to rapidly lock in the favorable structural state jointly induced by appropriate Sb and O doping amounts at high temperatures, suppress the reordering caused by anion sublattice relaxation during natural cooling, and reduce the risk of local enrichment, phase segregation, and impurity phase reprecipitation caused by dopant diffusion and segregation. In other words, the Sb doping amount determines the degree of lattice perturbation and disordered structure establishment at high temperatures, the O doping amount determines local structural stability and interface control capability, while the quenching treatment is used to preserve the favorable high-temperature structure and interface control foundation established by the appropriate doping amounts, allowing the modification effect of multi-doped materials to be stably maintained at room temperature. Attached Figure Description

[0036] Figure 1 The XRD test patterns of Examples 1-3 and Comparative Example 3 of the present invention are compared.

[0037] Figure 2 The electrochemical impedance spectroscopy (EIS) spectra of Examples 1-3 of the present invention at a temperature of 30 °C are shown.

[0038] Figure 3 This is the limiting current diagram for Example 3.

[0039] Figure 4 The graph shows the cycle performance test results of the full cell assembled in Example 1 at a 1 C rate. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments.

[0041] Example 1 (1) In an argon atmosphere, S, Li2S, LiI, GeS2, Sb2S3, P2S5, and Li2O in a stoichiometric ratio of 1.2:4.9:2.0:0.4:0.6:0.2:0.3 were ground and mixed evenly, and then placed in a ball mill jar. Anhydrous p-xylene was added as the organic grinding medium, and the liquid-to-solid ratio was 1.5 mL g. -1 The ball-to-powder ratio was 20:1. After complete sealing, the mixture was wet-milled at 550 rpm for 20 h. After milling, the resulting slurry was thoroughly dried under vacuum at 120 °C to completely remove the organic solvent, resulting in a homogeneous precursor powder. This powder was then pressed into a green preform under a pressure of 400 MPa and transferred to a muffle furnace for sintering at 5 °C for 1 min. -1 The temperature was increased to 250 °C for low-temperature sintering for 4 hours, followed by a further increase of 5 °C for 1 minute. -1 The temperature was increased to 550°C for high-temperature sintering for 5 hours. After sintering, the solid electrolyte was quickly removed and placed in a pre-cooled, thick oxygen-free copper heat sink mold for quenching, allowing the sample to be instantly cooled from a high temperature to room temperature, yielding Li. 6.2 Ge 0.2 Sb 0.6 P 0.2 S 4.85 O 0.15 I-Iodine-based thiosilver-germanium mineral phase electrolyte.

[0042] (2) In an argon atmosphere, weigh 100 mg of the electrolyte powder obtained in step (1) and place it in a solid battery mold. Press it with 400 MPa for 3 min to form an electrolyte layer. Attach the cut lithium sheet to both sides of the electrolyte and press it with 50 MPa for 1 min to obtain a lithium-lithium symmetric battery for testing the limiting current density and the long-cycle stability of the lithium-lithium symmetric battery.

[0043] (3) In an argon atmosphere, positive electrode active material LiNi with a mass ratio of 80:15:5 is placed. 0.8 Mn 0.1 Co 0.1O2. The solid electrolyte obtained in step (1) and the vapor-grown carbon fiber are ground and mixed evenly to obtain composite cathode powder. 100mg of solid electrolyte powder is weighed and spread evenly in a solid battery mold, and pressed at 300 MPa for 3 min to form an electrolyte layer. Composite cathode powder is spread evenly on one side of the electrolyte layer and pressed at 400 MPa for 3 min. The cut lithium sheet is attached to the other side of the electrolyte and pressed at 150 MPa for 1 min to obtain an all-solid-state battery.

[0044] Example 2 In this embodiment, the stoichiometric ratio of S, Li2S, LiI, Si, Sb2S3, P2S5, and Li2O in step (1) is 2.0:4.9:2.0:0.4:0.6:0.2:0.3, and the rest is the same as in Example 1, to obtain Li 6.2 Si 0.2 Sb 0.6 P 0.2 S 4.85 O 0.15 I-Iodine-based thiosilver-germanium mineral phase electrolyte.

[0045] Example 3 In this embodiment, the stoichiometric ratio of S, Li2S, LiI, SnS2, Sb2S3, P2S5, and Li2O in step (1) is 1.2:4.9:2.0:0.4:0.6:0.2:0.3, and the rest is the same as in Example 1, to obtain Li 6.2 Sn 0.2 Sb 0.6 P 0.2 S 4.85 O 0.15 I-Iodine-based thiosilver-germanium mineral phase electrolyte.

[0046] Comparative Example 1 This comparative example illustrates the low ionic conductivity and poor interfacial stability of iodine-based silver-germanium sulfide phase solid electrolytes without group IV metal M and antimony or oxygen multi-doped phases.

[0047] The iodine-based silver-germanium sulfide mineral phase solid electrolyte of this comparative example was prepared by the following method: (1) Under an argon atmosphere, Li₂S, LiI, and P₂S₅ in a stoichiometric ratio of 5:2:1 were ground and mixed evenly, and then placed in a ball mill jar. Anhydrous p-xylene was added as the organic grinding medium, and the liquid-to-solid ratio was 1.5 mL g. -1 The ball-to-material ratio was 20:1. After being completely sealed, the mixture was wet-milled at 550 rpm for 20 h. After milling, the resulting slurry was thoroughly dried under vacuum at 120 °C to completely remove the organic solvent, resulting in a precursor powder with uniform composition.

[0048] (2) The solid electrolyte obtained in step (1) is pressed under a pressure of 400 MPa to obtain a preform, which is then transferred to a muffle furnace and sintered in a sealed state at 5 °C for 1 minute. -1 The temperature was increased to 250 °C for low-temperature sintering for 4 hours, followed by a further increase of 5 °C for 1 minute. -1 The temperature was increased to 550 °C for high-temperature sintering for 5 hours. After the high-temperature sintering was completed, the solid electrolyte was quickly removed and placed in a pre-cooled thick oxygen-free copper heat dissipation mold for quenching treatment, so that the sample was instantly cooled from the high temperature state to room temperature to obtain Li6PS5I sulfur silver germanium mineral phase electrolyte.

[0049] Comparative Example 2 This comparative example illustrates the instability of the lithium metal interface in an oxygen-free iodine-based sulfosilver-germanium mineral phase solid electrolyte.

[0050] The iodine-based silver-germanium sulfide mineral phase solid electrolyte of this comparative example was prepared by the following method: (1) In an argon atmosphere, S, Li2S, LiI, GeS2, Sb2S3, and P2S5 in a stoichiometric ratio of 0.6:2.6:1.0:0.2:0.3:0.1 were ground and mixed evenly in a ball mill jar, and anhydrous p-xylene was added as the organic grinding medium. The liquid-to-solid ratio was 1.5 mL g. -1 The ball-to-material ratio was 20:1. After being completely sealed, the mixture was wet-milled at 550 rpm for 20 h. After milling, the resulting slurry was thoroughly dried under vacuum at 120 °C to completely remove the organic solvent, resulting in a solid electrolyte precursor powder with uniform composition.

[0051] (2) The solid electrolyte obtained in step (1) is cold-pressed at a pressure of 400 MPa to obtain a preform, which is then transferred to a muffle furnace and sintered in a sealed state at 5 °C min. -1 The temperature was increased to 250 °C for low-temperature sintering for 4 hours, followed by a further increase of 5 °C for 1 minute. -1 The temperature was increased to 550 °C for high-temperature sintering for 5 hours. After high-temperature sintering, the solid electrolyte was quickly removed and placed in a pre-cooled thick oxygen-free copper heat sink mold for quenching, allowing the sample to be instantly cooled from a high-temperature state to room temperature, yielding Li. 6.2 Ge 0.2 Sb 0.6 P 0.2 S5I iodine-based sulfur silver germanium mineral phase electrolyte.

[0052] Comparative Example 3 This comparative example illustrates the occurrence of impurity phases and phase segregation in iodine-based silver-germanium ore phase solid electrolytes during wet ball milling, stepwise sintering, and quenching processes.

[0053] The iodine-based silver-germanium sulfide mineral phase solid electrolyte of this comparative example was prepared by the following method: (1) In an argon atmosphere, the raw materials were weighed according to the stoichiometric ratio of Example 1, ground and mixed evenly, and then placed in a ball mill jar with a ball-to-material ratio of 20:1. After being completely sealed, the raw materials were ball milled at a speed of 550 rpm for 20 h to obtain the precursor powder.

[0054] (2) The solid electrolyte obtained in step (1) is pressed under a pressure of 400 MPa to obtain a preform, which is then transferred to a muffle furnace and sintered in a sealed state at 5 °C for 1 minute. -1 The temperature was increased to 550 °C for sintering, and the high-temperature sintering time was 5 h. After cooling to room temperature, the mixture was ground into powder to obtain Li. 6.2 Ge 0.2 Sb 0.6 P 0.2 S 4.85 O 0.15 I-Iodine-based thiosilver-germanium mineral phase electrolyte.

[0055] Performance testing: 1. XRD Test The solid electrolyte powders obtained in Examples 1-3 and Comparative Example 3 were thoroughly ground and mixed evenly before being characterized by XRD. The scanning range was set to 2θ = 10°-70°.

[0056] 2. Electrochemical AC impedance spectroscopy test The sulfide electrolytes prepared in Examples 1-3 were subjected to impedance testing, with a test range of 0.1 Hz to 1 MHz and a test temperature of 30 °C.

[0057] 3. Long-cycle testing of lithium-ion symmetric batteries In an argon atmosphere, 150 mg of solid electrolyte powder from Examples 1-3 and Comparative Examples 1-3 was weighed and spread evenly in a solid-state battery mold. The mixture was pressed at 400 MPa for 3 min to form an electrolyte layer. Cut lithium sheets were then attached to both sides of the electrolyte layer, and the mixture was pressed at 50 MPa for 1 min to obtain a lithium-lithium symmetric battery. Long-cycle testing of the electrolyte was then conducted, with the cycle current density set at 0.5 mA cm⁻¹. -2 The charging capacity is 0.5 mAh cm⁻¹ -2 .

[0058] 4. Limiting Current Density Test In an argon atmosphere, 150 mg of the solid electrolyte powder from Example 1 was weighed and spread evenly in a solid battery mold. The mixture was pressed at 400 MPa for 3 min to form an electrolyte layer. The cut lithium sheets were attached to both sides of the electrolyte and pressed at 50 MPa for 1 min to obtain the limiting current density of the lithium-lithium symmetric battery test.

[0059] 5. Full battery cycle performance test In an argon atmosphere, positive electrode active material LiNi with a mass ratio of 80:15:5 is... 0.8 Mn 0.1 Co 0.1 O2. The solid electrolyte obtained in Example 1 and the vapor-grown carbon fiber are ground and mixed evenly to obtain a composite cathode powder. 100 mg of solid electrolyte powder is weighed and spread evenly in a solid battery mold, and pressed at 300 MPa for 3 min to form an electrolyte layer. Composite cathode powder is spread evenly on one side of the electrolyte layer and pressed at 400 MPa for 3 min. A cut lithium sheet is attached to the other side of the electrolyte and pressed at 150 MPa for 1 min to obtain an all-solid-state battery. The full-cell cycle performance is tested at 30 °C and 1 C rate.

[0060] The ionic conductivity of the electrolyte materials obtained in the examples and comparative examples and the long-cycle test results of the lithium-lithium symmetric battery electrolytes are shown in Table 1.

[0061] Table 1

[0062] XRD test results are as follows Figure 1 As shown, the results indicate that the electrolytes of Examples 1-3 prepared by the method described in this invention have the same crystal structure as Li6PS5I standard card and are free of other impurities. However, the diffraction peaks of Comparative Example 3 show poor consistency with the characteristic peaks of the Li6PS5I standard card and exhibit obvious impurity peaks, indicating lower purity of the target phase. Furthermore, the characteristic peaks are broadened and their intensity decreases, indicating insufficient crystallinity and structural integrity. This is because Comparative Example 3 did not employ wet ball milling, stepwise sintering, and quenching treatment, resulting in uneven mixing of the multi-component precursors, insufficient sintering reaction, and structural reordering and local phase precipitation during cooling, making it difficult to form a stable target iodine-based silver-germanium sulfide phase electrolyte.

[0063] The evaluation of the stability of the lithium metal interface mainly includes limiting current density testing and long-cycle stability testing of lithium-lithium symmetric batteries. The test results are shown in Table 1 and... Figure 3The results showed that after introducing P-site synergistic substitution of group IV metals M (Si, Ge, Sn) and antimony, combined with S-site O substitution, Examples 1-3 all exhibited superior lithium metal interface stability. Specifically, the lithium-lithium symmetric batteries assembled in Examples 1, 2, and 3 achieved stable cycling times exceeding 1500 h, 1200 h, and 1600 h, respectively. In contrast, the symmetric batteries in Comparative Examples 1 and 2 only had cycling times of 29 h and 70 h, respectively. Furthermore, a comparison between Comparative Example 3 and Example 1 revealed that although both had the same chemical composition, Comparative Example 3 lacked wet ball milling, stepwise sintering, and quenching processes, resulting in significantly lower ionic conductivity and cycling stability compared to Example 1. This demonstrates the crucial role of the present invention's preparation process in component homogenization, suppression of impurity phases, and locking of disordered crystal phases. To verify the effectiveness of the electrolyte in practical applications, Example 1 was assembled into an all-solid-state lithium metal battery and subjected to cycling tests. The results are shown below. Figure 4 The initial discharge specific capacity at 1 C rate is 249.5 mAh g. 1 The capacity retention rate after 180 cycles was 87.2%.

[0064] Further comparison with Comparative Example 2 and Examples 1-3 reveals that partial substitution of the S site by O helps to induce a denser and more stable protective layer in situ at the lithium anode interface during cycling, thereby reducing interfacial side reactions and suppressing dendrite growth caused by uneven deposition, thus improving electrolyte cycling stability. Simultaneously, the synergistic substitution of the group IV metal M and antimony at the P site utilizes heterovalent substitution to introduce additional Li. + To increase carrier concentration, and on the other hand, to widen lithium-ion transport channels by utilizing the radius effect, thereby improving the intrinsic ionic conductivity of the electrolyte: the impedance test results of Examples 1-3 are as follows. Figure 2 As shown, the calculated room-temperature ionic conductivity of Examples 1-3 is 6.96-9.16 mS / cm. -1 The value was higher than 0.07 mS / cm in Comparative Example 1. -1 .

[0065] The above embodiments demonstrate that by introducing the synergistic substitution of P-sites of Group IV metal M and Sb, and the partial substitution of S-sites of O into the iodine-based silver sulfide germanium ore electrolyte Li6PS5I, synergistic regulation of bulk ion transport performance and lithium interface stability is achieved. Furthermore, through wet ball milling, stepwise sintering, and quenching, the target structure and interface regulation effects corresponding to appropriate Sb and O doping amounts are ensured to be formed and stably retained, thereby improving the ionic conductivity of the iodine-based silver sulfide germanium ore type solid electrolyte, while simultaneously improving its interfacial compatibility and cycle stability with metallic lithium. Specifically: First, this invention enhances the lattice perturbation of iodine-based silver sulfide germanium ore by synergistic substitution of P-sites of Group IV metal M and Sb, improving the Li...+ Migration conditions are improved, thereby enhancing the bulk ion transport performance of the material. By controlling the doping amounts of M and Sb within appropriate ranges, insufficient doping can lead to limited modification, while excessive doping can cause local enrichment, secondary phase precipitation, and structural instability.

[0066] Second, the present invention further introduces O element to partially replace S site, which helps to enhance the stability of local lattice framework and electronic insulation properties, and promotes the formation of a more stable interface protective layer during battery cycling, thereby reducing interface side reactions and suppressing lithium dendrite-induced uneven deposition; by controlling the amount of O element doping, the ion transport network is avoided from being damaged or the phase formation difficulty is increased due to excessive O introduction.

[0067] Third, this invention does not simply increase the types of doping, but rather achieves a synergistic improvement in bulk ion transport performance and lithium interface stability by synergistically controlling the doping amounts of Sb and O elements. The former is mainly used to enhance bulk structure disturbance and ion migration, while the latter is mainly used to improve interface stability.

[0068] Fourth, the present invention employs a wet ball milling process, which improves the dispersion uniformity of M, Sb and O sources in the precursor and reduces the adverse effects of local overheating and powder agglomeration in traditional dry ball milling, thus providing a foundation for the uniform solid solution of subsequent doping elements and the stable formation of the target phase.

[0069] Fifth, the present invention employs a stepwise sintering process, which allows the multi-component doped system to undergo a gradual evolution process from pre-reaction to full phase formation and uniform solid solution. This helps to reduce the risks of local segregation, unreacted residues, and secondary phase precipitation, thereby ensuring that the structural design corresponding to the appropriate doping amount can be effectively realized.

[0070] Sixth, the present invention employs quenching treatment after sintering, which can quickly lock the favorable structural state jointly induced by appropriate Sb doping and O doping at high temperature, suppress the reordering of anionic sublattices during natural cooling and the local enrichment, phase segregation and re-precipitation of impurity phases caused by diffusion and segregation of dopants, thereby better preserving the modification effect of multi-component doping.

[0071] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. An iodine-based silver-germanium sulfide-phase solid electrolyte possessing both high ionic conductivity and interfacial stability, characterized in that: The electrolyte is an iodine-based silver-germanium sulfide-phase solid electrolyte Li6PS5I doped with M, Sb, and O elements. The chemical formula of the electrolyte is Li. 6+a M a Sb b P 1-a-b S 5-c O c I and M are one or more of Si, Ge and Sn, with 0.1≤a≤0.3, 0.5≤b≤0.65, and 0.1≤c≤0.2; M and Sb elements occupy the P sites of the iodine-based silver-germanium sulfide mineral phase solid electrolyte Li6PS5I, and oxygen element occupies the S sites; the electrolyte is obtained by wet ball milling, pressing, sintering and quenching.

2. The iodine-based silver-sulfur germanium mineral phase solid electrolyte with both high ionic conductivity and interfacial stability as described in claim 1, characterized in that: 0.15≤a≤0.20, 0.55≤b≤0.60, 0.12≤c≤0.

18.

3. A method for preparing an iodine-based silver-germanium sulfide-phase solid electrolyte with both high ionic conductivity and interfacial stability as described in claim 1 or 2, characterized in that: The method steps include: (1) In an inert atmosphere, weigh the raw materials Li2S, LiI, Sb2S3, P2S5, S, Li2O and M elemental raw materials according to the stoichiometric ratio. The M elemental raw material is MS2 or elemental M. After mixing the raw materials evenly, add a non-polar organic solvent for wet ball milling, and then vacuum dry to remove the solvent to obtain the precursor powder. (2) In an inert atmosphere, the precursor powder is pressed into a blank and sintered in a closed state. After sintering, it is immediately quenched to cool the sample instantaneously from the sintering temperature, thus obtaining an iodine-based silver-germanium ore phase solid electrolyte with both high ionic conductivity and interfacial stability.

4. The method for preparing an iodine-based silver-germanium sulfide-phase solid electrolyte with both high ionic conductivity and interfacial stability as described in claim 3, characterized in that: In step (1), the inert gas is argon or helium; Preferably, in step (1), the nonpolar organic solvent is one or more of p-xylene, n-heptane, and n-hexane; In step (1), the liquid-to-solid ratio of the wet ball milling is 1.0~2.0 mL g. -1 ; In step (1), the rotation speed of the wet ball mill is 550~600 rpm, and the time is 15~20 h; In step (1), the ball-to-material ratio in wet ball milling is (15~25):

1.

5. The method for preparing an iodine-based silver-germanium sulfide-phase solid electrolyte with both high ionic conductivity and interfacial stability as described in claim 3, characterized in that: In step (2), the heating rate during sintering is 3~8 °C min. -1 ; Preferably, in step (2), the pressing pressure is 350~650 MPa and the pressing time is 2~3 min; Preferably, in step (2), sintering includes a low-temperature sintering stage and a high-temperature sintering stage; the temperature of the low-temperature sintering stage is 200~300 °C and the holding time is 4~6 h, and the temperature of the high-temperature sintering stage is 450~550 °C and the holding time is 4~8 h.

6. The method for preparing an iodine-based silver-germanium sulfide-phase solid electrolyte with both high ionic conductivity and interfacial stability as described in claim 3, characterized in that: In step (2), the quenching process involves rapidly placing the solid electrolyte after sintering into a high thermal conductivity metal heat dissipation mold that has been pre-cooled to -20~0 °C, so that the electrolyte can be rapidly cooled from the sintering temperature to room temperature; preferably, the pre-cooling temperature is -10~0 °C, and the mold material is copper or oxygen-free copper.

7. An all-solid-state lithium metal battery, characterized in that: The battery comprises a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode; the material of the solid electrolyte layer comprises the iodine-based silver-germanium sulfide phase solid electrolyte as described in claim 1 or 2, which has both high ionic conductivity and interfacial stability.

8. A method for preparing an all-solid-state lithium metal battery according to claim 9, characterized in that: The method steps include: (a) In an inert atmosphere, the positive electrode active material, the solid electrolyte and the conductive agent described in this invention are ground and mixed until they are evenly dispersed to obtain composite positive electrode powder. (b) In a solid-state battery mold, the solid electrolyte powder described in this invention is weighed and spread evenly, and pressure is applied to press it into a sheet; then, the composite positive electrode powder obtained in step (a) is evenly spread on one side of the solid electrolyte layer, pressure is applied for the first time to press it, and finally, a lithium indium alloy sheet is added to the other side of the solid electrolyte layer, and pressure is applied for the second time to press it for encapsulation, thereby obtaining an all-solid-state lithium metal battery.

9. The method for preparing an all-solid-state lithium metal battery as described in claim 8, characterized in that: In step (a), the inert gas is argon or helium; Preferably, in step (a), the positive electrode active material is selected from LiNi. 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 One of O2 and LiCoO2; Preferably, in step (a), the conductive agent is selected from one or more of acetylene black, Ketjen black, carbon nanotubes and vapor-grown carbon fibers; Preferably, in step (a), the mass ratio of the positive electrode active material, the solid electrolyte, and the conductive agent is 70~80:15~25:2~5.

10. The method for preparing an all-solid-state lithium metal battery as described in claim 8, characterized in that: In step (b), the pressure for pressing the solid electrolyte is 250~400 MPa; Preferably, in step (b), the first applied pressure is 350~450 MPa; Preferably, in step (b), the second applied pressure is 50~200 MPa.

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