A sulfide solid-state electrolyte and a method for preparing the same

Abstract

This invention discloses a sulfide solid electrolyte comprising a substrate and co-doped elements, including M and N, where M≠N and M and N are transition metals or main group elements with different valence states. M is used to replace cation sites in the substrate, and N is used to replace anion sites in the substrate. M and N have a co-doping combination relationship, replacing either cation or anion sites. Based on this, the invention also discloses a method for preparing the above material. The invention has the following technical advantages: the material bulk effectively prevents the initiation and penetration of Na dendrites. The heterovalent co-doping strategy is precisely designed to ensure that while enhancing mechanical stiffness, the ion transport mechanism is not impaired, maintaining a high level of superionic conductivity. This avoids the use of complex and expensive external composite materials or multilayer interface coatings to enhance mechanical properties in ASSSIBs, simplifying the manufacturing process and reducing manufacturing costs.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state sodium battery technology, and more specifically, to a sulfide solid electrolyte and its preparation method. Background Technology

[0002] Sodium-ion batteries (SIBs) are considered a viable solution for next-generation large-scale energy storage systems due to the abundance and sustainability of sodium resources. All-solid-state sodium batteries (ASSSIBs) use solid electrolytes, which are expected to solve the safety hazards of traditional liquid electrolytes and achieve higher energy density.

[0003] Sulfide-based solid electrolytes (SSEs), such as the Na3PS4 system, are advantageous due to their high room temperature Na content. + It has attracted widespread attention due to its high ionic conductivity and good processability. To further improve the ionic conductivity σ, existing techniques typically employ heterovalent ion doping (e.g., with Cl-). - Alternatively, Se anion doping of S, or Sb cation doping of P, can be used to modulate the lattice structure and introduce defects (Na). + Vacancies or gaps can increase carrier concentration and ion transport efficiency.

[0004] Challenges to the commercialization of all-solid-state sodium batteries: (1) Insufficient mechanical stiffness and risk of dendrite penetration: ASSSIBs must possess superior mechanical properties. However, in order to achieve high Na... + Ionic conductivity, Na in the lattice of SSEs + The bonds between ions and anions are typically weak, resulting in insufficient mechanical strength and elastic modulus of the material. When used in conjunction with a Na metal anode at high current densities, SSEs are easily penetrated by sodium dendrites, leading to internal short circuits and catastrophic failures.

[0005] (2) The inherent contradiction of functional optimization strategies: In the existing technology, the defect doping strategy aimed at improving ionic conductivity often leads to a further decline in the mechanical properties of the material, resulting in a performance trade-off. On the other hand, enhancing mechanical strength through composite materials usually sacrifices the high ionic conductivity of the sulfide matrix.

[0006] In summary, the pressing issue in this field is how to achieve a synergistic enhancement of high mechanical stiffness and superionic conductivity in the material bulk of sulfide solid electrolytes through atomic-scale design, thereby effectively resisting Na dendrite penetration and ensuring the long-term stable operation of ASSSIBs without relying on complex composite structures. Summary of the Invention

[0007] The main objective of this invention is to provide a sulfide solid electrolyte material with dual enhancement functions. Through precise heterovalent co-doping and lattice dynamics control, it significantly improves the elastic modulus and mechanical stiffness of the material while maintaining superionic conductivity, so as to effectively resist Na dendrite penetration and thus be applied in high-safety, long-cycle all-solid-state sodium batteries.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned material.

[0009] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows: Technical terms involved in this invention: Sodium-ion batteries (SIBs) All-solid-state sodium batteries (ASSSIBs) Sulfide-based solid electrolytes (SSEs) Solid electrolytes (SSE) Plasma sintering (SPS) Critical current density (CCD) Na3V2(PO4)3 (NVP) The sulfide solid electrolyte of this invention:

[0010] The core lies in achieving mechanical stiffness and Na+ in the bulk lattice of Na3PS4 or Na3SbS4 sulfide solid electrolytes (SSEs) through a heterovalent co-doping strategy. + The synergistic enhancement of superionic conductivity fundamentally improves the electrolyte's resistance to sodium dendrite penetration.

[0011] The sulfide solid electrolyte comprises a substrate material, preferably based on a Na3PS4 or Na3SbS4 system. The cation sites (P) are replaced by heterovalent co-doped elements M and N (M≠N and M and N are transition metals or main group elements with different valence states). 5+ or Sb 5+ ) or anion site (S 2- ) Obtained through modification.

[0012] This material, optimized through co-doping, aims to enhance short-range interactions within the sulfide lattice framework, thereby improving its elastic modulus and mechanical stiffness and effectively resisting the vertical growth of Na dendrites. Simultaneously, this material must maintain super-Na dendrites at room temperature. + Ionic conductivity (preferably σ greater than 10) -3 S·cm -1 ).

[0013] The co-doped elements M and N are selected from elements that can effectively adjust defect structures, increase Na+ ion concentration, and enhance lattice strength, wherein: (1) Cation site P 5+ or Sb 5+ Alternative: The preferred cationic element M is selected from Sn. 4+ 、Ge 4+ Si 4+ W 6+ As 5+ At least two.

[0014] (2) Anion site S 2- Alternative: The preferred anionic element N is selected from halogens (Cl). - F - I - ,Br - ) or Se 2- At least two.

[0015] (3) Co-doping combination: Preferred co-doping combinations include cation-cation (e.g., Sn) 4+ and W 6+ Co-doped P 5+ (position) or cation-anion (such as Sn) 4+ Replace P 5+ Meanwhile, Cl - Replace S 2- )system.

[0016] The co-doping can induce the formation of highly disordered amorphous or high-density glass-ceramic phases in the material, which helps to reduce grain boundary resistance and improve mechanical and chemical durability.

[0017] The preparation method of the sulfide solid electrolyte with dual enhancement function described in this invention:

[0018] The preparation of the material must employ a synthesis method capable of achieving uniform doping and high density to ensure the synergistic realization of mechanical properties and ion conductivity. The specific steps are as follows: S1: Precise metering and precursor mixing

[0019] 1. Precursor Selection: The precursors are precisely selected from Na2S, P2S5 (Sb2S3), and corresponding doping sources (e.g., SnS2, GeS2, WO3, As2S5, NaCl, NaI, or Se powder). The doping ratio and element combination must ensure that the material maintains charge neutrality in the crystal structure.

[0020] 2. Environmental control: All weighing, mixing and handling steps must be carried out in a strictly inert atmosphere (e.g., Ar atmosphere) or high vacuum environment to avoid degradation of sulfide precursors or products by moisture in the environment.

[0021] S2: Directional synthesis of materials (achieving uniform doping)

[0022] 1. Mechanochemical ball milling method: It is preferable to ball mill the precursor mixture for a long time (10-12 hours) at 500-600 rpm in a high-energy ball mill to obtain a highly uniform doping distribution and promote the disordering of the material.

[0023] 2. Heat Treatment / Annealing: The ball-milled product is heat-treated to promote the formation of the target phase structure with high ionic conductivity. This heat treatment is typically performed at relatively low temperatures of 270–450°C and must be completed within a vacuum quartz tube or under an inert atmosphere to ensure material purity and structural stability. Alternatively, melt quenching can be used. In this case, the cooling rate must be precisely controlled to obtain the desired amorphous glassy or glass-ceramic phase, which is crucial for the material's mechanical durability.

[0024] S3: Consolidation and densification (enhancing mechanical stiffness)

[0025] Spark plasma sintering (SPS) or cold pressing under high pressure (300MPa~400MPa) is preferred. SPS technology utilizes pressure and current to achieve rapid densification at relatively low temperatures, effectively avoiding component volatilization or phase decomposition that may occur during traditional high-temperature sintering. After high-pressure densification, porosity and grain boundaries are eliminated, improving the material's macroscopic hardness and mechanical stiffness. This treatment should ideally result in a relative density >98%.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The sulfide solid electrolyte of the present invention achieves the synergistic enhancement of ionic conductivity and mechanical stiffness in the bulk material, resulting in the following significant technical and beneficial effects: 1. Fundamentally solves the dendrite penetration problem: The material itself possesses higher elastic modulus and mechanical stiffness, effectively preventing the initiation and penetration of Na dendrites. This will directly increase the critical current density (CCD) of the battery, enabling ASSSIBs to be applied in high-power, high-rate charge and discharge scenarios.

[0028] 2. Significantly extended battery cycle life: By eliminating internal short circuits and electrolyte failure caused by dendrites and ensuring stable contact at the interface (because the stiffer SSE is more resistant to stress), the cycle life of all-solid-state sodium batteries is significantly extended.

[0029] 3. Maintain high Na + Ion transport efficiency: The heterovalent co-doping strategy is precisely designed to ensure that while enhancing mechanical stiffness, the ion transport mechanism of SSE is not compromised, maintaining the superionic conductivity level and guaranteeing the high-performance output of the battery.

[0030] 4. Simplified battery assembly and reduced costs: This solution is a single-material bulk optimization, which avoids the use of complex and expensive external composite materials or multi-layer interface coatings in ASSSIBs to enhance mechanical properties, thus simplifying the manufacturing process and reducing overall manufacturing costs.

[0031] The invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0032] Figure 1 This is a SEM image of Example 1; Figure 2 This is the SEM image of Comparative Example 1. Detailed Implementation

[0033] The present invention will be further explained and described below through specific embodiments. It should be understood that the purpose of the following embodiments is to make the technical solution of the present invention clearer and easier to understand, and does not limit the scope of protection of the claims.

[0034] The present invention will be further described below through specific embodiments.

[0035] Test methods To ensure consistent evaluation standards, the material properties and battery performance of all embodiments and comparative examples were tested using the following methods: (1) Ionic conductivity (σ) test: The bulk resistance (Rb) is calculated by impedance spectrum fitting and calculated according to the formula σ = L / (Rb×S) (L is the electrolyte thickness and S is the electrode contact area).

[0036] (2) Mechanical performance test: Nanoindentation technology was used, with a loading rate of 5mN / s, a maximum load of 50mN, and a holding time of 10s. The elastic modulus (E) and Vickers hardness (HV) were calculated through the load-displacement curve.

[0037] (3) Critical Current Density (CCD) Test: A symmetrical battery (Na / SSE / Na) was assembled with Na metal as the counter / reference electrode, electrolyte as the separator, and Na3V2(PO4)3 (NVP) as the positive electrode. A constant current charge-discharge mode was used, starting from 0.1 mA / cm². 2 The current density is gradually increased. When the voltage drop is greater than 0.5V, the corresponding current density is the CCD.

[0038] (4) Full cell cycle performance test: Assemble a full cell (NVP / SSE / Na), with a voltage window of 2.5~3.8V and a current density of 0.1C. Test the discharge specific capacity and capacity retention rate after 50 cycles (capacity retention rate = 50th discharge capacity / 1st discharge capacity × 100%).

[0039] Comparison of preparation steps and data between the examples and comparative examples Example 1: Na3PS4 (Sn 4+ +W 6+ Co-doped P 5+ Bit)

[0040] (1) Precursor metrology (target molar ratio: Na3P) 0.97 Sn 0.02 W 0.01 S4): In an Ar glove box, weigh Na2S (99.9%, 1.500g), P2S5 (99.9%, 1.215g), SnS2 (99.5%, 0.038g), and WO3 (99.5%, 0.012g), for a total mass of 3.0g. (2) Mechanochemical ball milling: The raw materials were loaded into an agate ball mill jar (ball-to-material ratio 10:1, φ5mm agate balls), sealed, and placed in a planetary ball mill. The jar was milled at 550 rpm for 11 hours, with a 10-minute pause every 3 hours for heat dissipation, to obtain a gray amorphous powder. (3) Heat treatment annealing: The ball-milled powder was transferred to a quartz tube, vacuumed and sealed, and placed in a muffle furnace. It was then held at 350℃ for 3 hours (heating rate 5℃ / min) and cooled to room temperature with the furnace to obtain glass-ceramic phase powder. (4) High-pressure densification: The powder was loaded into a φ10mm mold and sintered by spark plasma (SPS) at 320℃ and 360MPa for 5 minutes (heating rate 10℃ / min) to obtain an electrolyte sheet with a relative density of 98.5% (thickness 1.5mm). (5) Battery assembly and testing: The electrolyte sheet was cut to φ8mm and assembled into a CR2032 full cell with an NVP positive electrode (80% active material + 10% acetylene black + 10% PVDF) and a Na metal negative electrode. The cell was then encapsulated in an Ar glove box and its performance was tested.

[0041] Example 2: Na3PS4 (Ge 4+ +As 5+ Co-doped P 5+ Bit)

[0042] (1) Precursor metrology (target molar ratio: Na3P) 0.97 Ge 0.015 As 0.015 S4): In the Ar glove box, weigh Na2S (1.498g), P2S5 (1.182g), GeS2 (99.5%, 0.027g), and As2S5 (99.5%, 0.033g), for a total mass of 3.0g; (2) Mechanochemical ball milling: Agate ball mill jar (ball-to-material ratio 10:1), ball milling at 500 rpm for 12 hours (pausing for 10 minutes every 4 hours) to obtain light gray amorphous powder; (3) Heat treatment annealing: The quartz tube was vacuum sealed and held at 300℃ for 4 hours (heating rate 5℃ / min), then cooled with the furnace. (4) High-pressure densification: SPS sintering (300℃, 360MPa, 5min), relative density 98.2%, electrolyte sheet thickness 1.4mm; (5) Battery assembly and testing: Same as in Example 1.

[0043] Example 3: Na3PS4 (Sn 4+ +Cl - Co-doped P 5+ +S 2- Bit)

[0044] (1) Precursor metrology (target molar ratio: Na3P) 0.98 Sn 0.02 S 3.97 Cl 0.03 ): In the Ar glove box, weigh Na2S (1.485g), P2S5 (1.202g), SnS2 (0.038g), and NaCl (99.9%, 0.015g), for a total mass of 3.0g; (2) Mechanochemical ball milling: Agate ball mill jar (ball-to-material ratio 10:1), ball milling at 600 rpm for 10 hours (pausing for 10 minutes every 2 hours) to obtain dark gray amorphous powder; (3) Heat treatment annealing: The quartz tube was vacuum sealed and held at 400℃ for 2 hours (heating rate 8℃ / min), then cooled with the furnace. (4) High-pressure densification: SPS sintering (350℃, 360MPa, 5min), relative density 99.1%, electrolyte sheet thickness 1.6mm; (5) Battery assembly and testing: Same as in Example 1.

[0045] Example 4: Na3SbS4 (Si 4++W 6+ Co-doped Sb 5+ Bit)

[0046] (1) Precursor metrology (target molar ratio: Na3Sb) 0.97 Si 0.025 W 0.005 S4): In the Ar glove box, weigh Na2S (1.452g), Sb2S3 (99.9%, 1.428g), SiS2 (99.5%, 0.041g), and WO3 (0.002g), for a total mass of 3.0g; (2) Mechanochemical ball milling: Agate ball mill jar (ball-to-material ratio 10:1), ball milled at 550 rpm for 11 hours (pausing for 10 minutes every 3 hours) to obtain brown amorphous powder; (3) Heat treatment annealing: The quartz tube was vacuum sealed and held at 320℃ for 3 hours (heating rate 5℃ / min), then cooled with the furnace. (4) High-pressure densification: SPS sintering (330℃, 360MPa, 5min), relative density 98.3%, electrolyte sheet thickness 1.5mm; (5) Battery assembly and testing: Same as in Example 1.

[0047] Example 5: Na3SbS4 (Sn 4+ +Se 2- Co-doped Sb 5+ +S 2- Bit)

[0048] (1) Precursor metrology (target molar ratio: Na3Sb) 0.99 Sn 0.01 S 3.98 Se 0.02 ): In the Ar glove box, weigh Na2S (1.465g), Sb2S3 (1.442g), SnS2 (0.019g), and Se powder (99.5%, 0.014g), for a total mass of 3.0g. (2) Mechanochemical ball milling: Agate ball mill jar (ball-to-material ratio 10:1), ball milling at 500 rpm for 12 hours (pausing for 10 minutes every 4 hours) to obtain brownish-black amorphous powder; (3) Heat treatment annealing: The quartz tube was vacuum sealed and held at 270℃ for 4 hours (heating rate 3℃ / min), then cooled with the furnace. (4) High-pressure densification: Cold-pressed (holding pressure at 360MPa for 10min), relative density 98.0%, electrolyte sheet thickness 1.4mm; (5) Battery assembly and testing: Same as in Example 1.

[0049] Example 6: Na3PS4 (Ge 4+ +I - Co-doped P 5+ +S 2- Bit)

[0050] (1) Precursor metrology (target molar ratio: Na3P) 0.985 Ge 0.015 S 3.975 I 0.025 ): In the Ar glove box, weigh Na2S (1.480g), P2S5 (1.195g), GeS2 (0.027g), and NaI (99.9%, 0.038g), for a total mass of 3.0g; (2) Mechanochemical ball milling: Agate ball mill jar (ball-to-material ratio 10:1), ball milling at 600 rpm for 10 hours (pausing for 10 minutes every 2 hours) to obtain gray amorphous powder; (3) Heat treatment annealing: The quartz tube was vacuum sealed and held at 450℃ for 2 hours (heating rate 8℃ / min), then cooled with the furnace. (4) High-pressure densification: SPS sintering (340℃, 360MPa, 5min), relative density 98.8%, electrolyte sheet thickness 1.5mm; (5) Battery assembly and testing: Same as in Example 1.

[0051] Comparative Example 1: Pure Na3PS4 (undoped)

[0052] (1) Precursor metrology (target molar ratio: Na3PS4): In the Ar glove box, Na2S (1.512g) and P2S5 (1.488g) were weighed, with a total mass of 3.0g; (2) Mechanochemical ball milling: Agate ball milling jar (ball-to-material ratio 10:1), ball milling at 550 rpm for 11 hours (same parameters as in Example 1), yielded white amorphous powder; (3) Heat treatment annealing: The quartz tube was vacuum sealed and kept at 350°C for 3 hours (same parameters as in Example 1), then cooled with the furnace. (4) High-pressure densification: SPS sintering (320℃, 360MPa, 5min) (same parameters as in Example 1), relative density 98.4%, electrolyte sheet thickness 1.5mm; (5) Battery assembly and testing: Same as in Example 1.

[0053] Comparative Example 2: Na3PS4 (Sn 4+ Single-doped P 5+ Bit)

[0054] (1) Precursor metrology (target molar ratio: Na3P) 0.97 Sn 0.03 S4): In the Ar glove box, Na2S (1.498g), P2S5 (1.195g), and SnS2 (0.057g) were weighed, with a total mass of 3.0g; (2) Mechanochemical ball milling: Agate ball mill jar (ball-to-material ratio 10:1), ball milled at 550 rpm for 11 hours (same parameters as in Example 1), yielding gray amorphous powder; (3) Heat treatment annealing: The quartz tube was vacuum sealed and kept at 350°C for 3 hours (same parameters as in Example 1), then cooled with the furnace. (4) High-pressure densification: SPS sintering (320℃, 360MPa, 5min) (same parameters as in Example 1), relative density 98.3%, electrolyte sheet thickness 1.5mm; (5) Battery assembly and testing: Same as in Example 1.

[0055] Comparative Example 3: Na3PS4 + 5% Al2O3 (physical composite reinforcement)

[0056] (1) Precursor metrology (target composition: Na3PS4 + 5wt% Al2O3): In an Ar glove box, weigh 2.85 g of pure Na3PS4 powder (prepared according to the method of Comparative Example 1) and 0.15 g of Al2O3 nanopowder (99.9%, particle size 20 nm). (2) Mechanical mixing: Agate ball mill jar (ball-to-material ratio 10:1), ball milled at 550 rpm for 11 hours (same parameters as in Example 1), yielding a grayish-white mixed powder; (3) High-pressure densification: SPS sintering (320℃, 360MPa, 5min) (same parameters as in Example 1), relative density 97.8%, electrolyte sheet thickness 1.5mm (density slightly lower due to Al2O3 dispersion). (4) Battery assembly and testing: Same as in Example 1.

[0057]

[0058] Conclusion Analysis Based on the performance data of the above embodiments and comparative examples, the following conclusions can be drawn: (1) Co-doping strategy to achieve synergistic enhancement of electrical conductivity and mechanical properties

[0059] In Examples 1-6, through heterovalent co-doping (cation-cation or cation-anion), the ionic conductivity of all electrolytes (1.55~2.13×10⁻⁶) was improved. -3 S·cm -1 Both were significantly higher than pure Na3PS4 (Comparative Example 1, 0.82 × 10⁻⁶). - 3 S·cm -1 ) and a single-doped system (Comparative Example 2, 1.35 × 10 -3 S·cm -1 Meanwhile, the elastic modulus (28.9~35.8 GPa) and Vickers hardness (1.12~1.32 GPa) increased by 56%~93% compared to the pure system, proving that co-doping modulates lattice defects (increasing Na) + It improves ion transport and mechanical stiffness by eliminating vacancies and enhancing short-range bonding.

[0060] (2) Improved mechanical properties directly enhance dendrite resistance and cycling stability.

[0061] The critical current density of the embodiment (CCD = 1.05~1.38 mA·cm) -2 ) is pure Na3PS4 (0.45 mA·cm -2 The capacity of the battery was 2.3 to 3.1 times that of Comparative Example 3 (Sn), and the capacity retention rate after 50 cycles (89.7% to 94.2%) was significantly higher than that of Comparative Example 1 (75.2%) and Comparative Example 2 (82.6%), indicating that the enhanced mechanical stiffness effectively prevents Na dendrite penetration, reduces interface failure, and extends battery life. Example 3 (Sn) 4+ +Cl - Co-doped materials exhibit the best overall performance (σ=2.13×10⁻⁶) due to the synergistic effect of "cation defects regulating conductivity + anions enhancing lattice bonding". -3 S·cm -1(E=35.8GPa, capacity retention 94.2%).

[0062] (3) The bulk optimization is superior to the traditional composite reinforcement, balancing performance and cost.

[0063] Comparative Example 3 uses physically mixed Al2O3 to enhance mechanical properties (E=29.7GPa), but the ionic conductivity decreases to 0.58×10⁻⁶ due to the insulating properties of Al2O3. -3 S·cm -1 Furthermore, the total cell capacity (95.7 mAh / g) and retention rate (80.3%) were both lower than those of the previous example. This demonstrates that the "atomic-scale bulk co-doping" of this invention can enhance mechanical properties while maintaining high conductivity without relying on external composite structures, simplifying the preparation process, reducing costs, and better meeting the commercialization requirements of all-solid-state sodium batteries.

[0064] (4) The influence of system and process parameters on performance

[0065] a. Compared to the Na3SbS4 system (Examples 4 and 5), the Na3PS4 system (Examples 1-3 and 6) has better performance due to P 5 ⁺ Smaller ionic radius, Na in the crystal lattice + The transmission channel is smoother, and the conductivity is generally higher (1.55~2.13×10). -3 S·cm -1 vs 1.55~1.78×10 -3 S·cm -1 ); b. Increasing the ball milling speed (600 rpm, Examples 3 and 6) and increasing the heat treatment temperature (400~450℃, Examples 3 and 6) can promote the uniform distribution of dopants and the formation of the glass-ceramic phase, further improving electrical conductivity and mechanical properties.

[0066] In summary, this patent provides a sulfide solid electrolyte material with dual enhancement functions through precise heterovalent co-doping and lattice dynamics control. While maintaining superionic conductivity, it significantly improves the elastic modulus and mechanical stiffness of the material to effectively resist Na dendrite penetration, thus enabling its application in high-safety, long-cycle all-solid-state sodium batteries.

[0067] This invention has been described by way of embodiments, but does not constitute a limitation thereof. Other variations of the disclosed embodiments, which are readily apparent to those skilled in the art, should fall within the scope of the claims of this invention, with reference to the description of this invention.

Claims

1. A sulfide solid electrolyte, characterized in that: It includes a substrate and co-doped elements, wherein the co-doped elements include M and N, wherein M ≠ N and M and N are transition metals or main group elements with different valence states, wherein M is used to replace the cation sites in the substrate, and N is used to replace the anion sites in the substrate, wherein M and N have a co-doping combination relationship, which is to replace the cation sites or anion sites.

2. The sulfide solid electrolyte according to claim 1, characterized in that: M is Sn 4+ 、Ge 4+ Si 4+ W 6+ 、or As 5+ At least two.

3. The sulfide solid electrolyte according to claim 1, characterized in that: The N is Cl - F - I - ,Br - 、 or Se 2- At least two.

4. The sulfide solid electrolyte according to claim 1, characterized in that: The co-doping combination of M and N is either a substitution of cation sites or a substitution of both cation and anion sites.

5. The sulfide solid electrolyte according to claim 1, characterized in that: The substrate is mainly composed of Na3PS4 or Na3SbS4 system.

6. The sulfide solid electrolyte according to claim 1, characterized in that: The Na of the sulfide solid electrolyte + The ionic conductivity σ is greater than 10. -3 S·cm -1 .

7. A method for preparing a sulfide solid electrolyte according to any one of claims 1-6, characterized in that: The steps include the following: S1: Precise metering and precursor mixing 1. Precursor selection: Na2S, P2S5 (Sb2S3) and corresponding doping sources are precisely selected as precursors; the doping ratio and element combination must ensure that the material maintains charge neutrality in the crystal structure; 2. Environmental control: All weighing, mixing and handling steps are carried out in an inert atmosphere or high vacuum environment to avoid degradation of sulfide precursors or products by moisture in the environment; S2: Directed Synthesis of Materials 1. Mechanochemical ball milling method: The precursor mixture is ball milled for a long time (10-12 hours) at 500-600 rpm in a high-energy ball mill to obtain a highly uniform doping distribution and promote the disordering of the material; 2. Heat Treatment / Annealing: The ball-milled product is heat-treated to promote the formation of the target phase structure with high ionic conductivity. The heat treatment is typically performed at relatively low temperatures of 270–450°C in a vacuum quartz tube or under an inert atmosphere to ensure material purity and structural stability. S3: Consolidation and densification Spark plasma sintering (SPS) or cold pressing under high pressure (300MPa~400MPa) is employed. SPS technology utilizes pressure and current to achieve rapid densification at relatively low temperatures, effectively avoiding component volatilization or phase decomposition that may occur in traditional high-temperature sintering. After high-pressure densification, the material eliminates pores and grain boundaries, improving the macroscopic hardness and mechanical stiffness of the material. The treatment should result in a relative density of >98%.

8. The preparation method according to claim 7, characterized in that: In step S1, the corresponding doping source is SnS2, GeS2, WO3, As2S5, NaCl, NaI, or Se powder.

9. The preparation method according to claim 7, characterized in that: In step S2, the heat treatment / annealing is performed using a melt quenching method, in which the cooling rate is precisely controlled to obtain the desired amorphous glass phase or glass-ceramic phase.

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