A sulfide solid electrolyte and an all-solid-state lithium battery

Abstract

This application relates to the field of electrochemical technology, and provides a sulfide solid electrolyte and an all-solid-state lithium battery. The chemical formula of the sulfide solid electrolyte is Li. 7‑2x‑y PM x S 6‑x‑y O x Cl 0.7y Br 0.3y M is at least one of Ca, Mg, and Cu, with 0.01≤x≤0.3, 0.5≤y≤2, and 0.008≤x / y≤0.24. The molar ratio of M to O is 1:1, and the molar ratio of Cl to Br is 7:3. The grain boundary resistance of the sulfide solid electrolyte at 25°C is 20Ω to 100Ω. Through the above settings, the sulfide solid electrolyte of this application achieves both high ionic conductivity and good air stability while also exhibiting low grain boundary resistance. Furthermore, the application of the sulfide solid electrolyte of this application in all-solid-state lithium batteries can improve the electrochemical performance of all-solid-state lithium batteries.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a sulfide solid electrolyte and an all-solid-state lithium battery. Background Technology

[0002] Against the backdrop of continuous development in all-solid-state lithium battery technology, sulfide solid electrolytes have attracted widespread attention due to their high lithium-ion conductivity and excellent processing performance. Among them, lithium-phosphorus-sulfur-chloride sulfide electrolytes, as typical sulfide-silver-germanium mineral structure materials, have been widely used in the research and development of high-performance solid-state batteries.

[0003] However, lithium-phosphorus-sulfur-chloride sulfide electrolytes still face the problem of high grain boundary impedance, limiting their overall ionic conductivity in practical devices. Although these sulfide solid electrolyte materials have high lithium-ion conductivity in bulk, the grain boundary regions formed between particles often hinder lithium-ion migration due to structural discontinuities, defect enrichment, or secondary phase precipitation, resulting in significant interfacial impedance. Existing technologies mainly focus on indirectly improving the grain boundary environment through sintering temperature, compaction processes, or particle size optimization, but research on directly controlling the bulk material to reduce grain boundary impedance remains limited. Furthermore, lithium-phosphorus-sulfur-chloride sulfide solid electrolytes are highly susceptible to decomposition in air, generating harmful gases such as hydrogen sulfide upon contact with moisture or oxygen, accompanied by structural damage and a significant decrease in electrochemical performance. This air stability defect greatly limits the reliability of sulfide solid electrolytes in industrial production, storage, transportation, and practical applications.

[0004] Therefore, there is an urgent need to develop a novel sulfide electrolyte material with low grain boundary impedance, high overall ionic conductivity, and good air stability, so as to improve the electrochemical performance of all-solid-state lithium batteries. Summary of the Invention

[0005] The purpose of this application is to provide a sulfide solid electrolyte and an all-solid-state lithium battery, which maintains the high ionic conductivity and good air stability of the sulfide solid electrolyte while reducing its grain boundary impedance, thereby improving the electrochemical performance of the all-solid-state lithium battery. The specific technical solution is as follows:

[0006] The first aspect of this application provides a sulfide solid electrolyte with the chemical formula Li. 7-2x-y PM x S 6-x- y O x Cl 0.7y Br 0.3yM is at least one of Ca, Mg and Cu, 0.01≤x≤0.3, 0.5≤y≤2, 0.008≤x / y≤0.24, the molar ratio of M to O is 1:1, and the molar ratio of Cl to Br is 7:3; the grain boundary resistance of the sulfide solid electrolyte at 25°C is 20Ω to 100Ω.

[0007] In one embodiment of this application, 0.02≤x≤0.1, 1.25≤y≤1.75.

[0008] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-2x-y PCa x S 6-x- y O x Cl 0.7y Br 0.3y , 0.02≤x≤0.1, 1.25≤y≤1.5.

[0009] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-2x-y PMg x S 6-x- y O x Cl 0.7y Br 0.3y , 0.03≤x≤0.07, 1.25≤y≤1.5.

[0010] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-2x-y PCu x S 6-x- y O x Cl 0.7y Br 0.3y , 0.05≤x≤0.1, 1.5≤y≤1.75.

[0011] In one embodiment of this application, the sulfide solid electrolyte is Li 5.65 PCa 0.05 S 4.7 O 0.05 Cl 0.87 5Br 0.375 Li 5.71 PCa 0.02 S 4.73 O 0.02 Cl 0.875 Br 0.375 Li 5.55 PCa 0.1 S 4.65 O0.1 Cl 0.875 Br 0.375 Li 5.4 PCa 0.0 5S 4.45 O 0.05 Cl 1.05 Br 0.45 Li 5.65 PMg 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 Li 5.4 PCu 0.05 S 4.45 O 0.05 Cl 1.05 Br 0.45 .

[0012] In one embodiment of this application, the cell parameters of the sulfide solid electrolyte satisfy: a=b=c=9.85~10Å.

[0013] In one embodiment of this application, the particle size of the sulfide solid electrolyte satisfies: 0.5µm < D50 < 3µm, 6.5µm < D90 < 9µm.

[0014] In one embodiment of this application, the ionic conductivity of the sulfide solid electrolyte is >5 mS / cm.

[0015] The second aspect of this application provides an all-solid-state lithium battery, which includes a positive electrode, a negative electrode, and a sulfide solid electrolyte as described in the first aspect of this application.

[0016] The beneficial effects of this application are:

[0017] This application provides a sulfide solid electrolyte and an all-solid-state lithium battery. The chemical formula of the sulfide solid electrolyte is Li. 7-2x-y PM x S 6-x-y O x Cl 0.7y Br 0.3yM is at least one of Ca, Mg, and Cu, with 0.01≤x≤0.3, 0.5≤y≤2, and 0.008≤x / y≤0.24. The molar ratio of M to O is 1:1, and the molar ratio of Cl to Br is 7:3. The grain boundary resistance of the sulfide solid electrolyte of this application is 20Ω to 100Ω at 25°C. Through the above settings, the sulfide solid electrolyte of this application achieves low grain boundary resistance while maintaining high ionic conductivity and good air stability. Furthermore, the sulfide solid electrolyte of this application can improve the electrochemical performance of all-solid-state lithium batteries when applied to them.

[0018] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0020] Figure 1 The sulfide solid electrolyte (Li) prepared in Example 1 5.65 PCa 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 X-ray diffraction pattern of )

[0021] Figure 2 The sulfide solid electrolyte (Li) prepared in Example 10 5.65 PMg 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 X-ray diffraction pattern of )

[0022] Figure 3 The sulfide solid electrolyte (Li) prepared in Example 11 5.4 PCu 0.05 S 4.45 O 0.05 Cl 1.05 Br 0.45 X-ray diffraction pattern of ). Detailed Implementation

[0023] The technical solutions of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0024] The first aspect of this application provides a sulfide solid electrolyte with the chemical formula Li. 7-2x-y PM x S 6-x- y O x Cl 0.7y Br 0.3y M is at least one of Ca, Mg, and Cu, with 0.01≤x≤0.3, 0.5≤y≤2, and 0.008≤x / y≤0.24. The molar ratio of M to O is 1:1, and the molar ratio of Cl to Br is 7:3. The grain boundary resistance of the sulfide solid electrolyte at 25°C is 20Ω to 100Ω. Preferably, 0.02≤x≤0.1 and 1.25≤y≤1.75. For example, x can be 0.01, 0.02, 0.05, 0.07, 0.1, 0.15, 0.2, 0.25, 0.3, or any range of two values ​​therein; y can be 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, or any range of two values ​​therein; and the value of x / y can be 0.008, 0.01, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.20, 0.22, 0.24, or any range of two values ​​therein. The grain boundary resistance of the sulfide solid electrolyte provided in this application at 25°C can be 20Ω, 25Ω, 30Ω, 35Ω, 40Ω, 45Ω, 50Ω, 55Ω, 60Ω, 65Ω, 70Ω, 75Ω, 80Ω, 85Ω. Ω, 90Ω, 95Ω, 100Ω, or a range consisting of any two of these values.

[0025] The sulfide solid electrolyte of this application, in the Li-based silver-germanium sulfide LPSC solid electrolyte... + Ca-doped at site 2+ Mg 2+ and Cu 2+ At least one of them, in S 2- O-doped at position 0 2- By adjusting the molar ratio of M to O to 1:1 and the molar ratio of Cl to Br to 7:3, while simultaneously controlling 0.01≤x≤0.3, 0.5≤y≤2, and 0.008≤x / y≤0.24, the grain boundary impedance of the sulfide solid electrolyte was reduced while maintaining high ionic conductivity and good air stability. Specifically, Li +Ca-doped at site 2+ Mg 2+ Cu 2+ This can reduce the formation of lithium-ion vacancies and decrease the number of highly reactive defects, thereby slowing down the degradation rate of the material and further enhancing the interfacial chemical stability. Meanwhile, Ca... 2+ (1.00Å), Mg 2+ (0.76Å) and Cu 2+ Larger radius Li substitution at (0.73 Å) + After reaching (0.6 Å), local lattice expansion and distortion occur, widening the lithium-ion migration channels and directly enhancing the diffusion capacity of lithium ions. 2- Replace S 2- Subsequently, the oxide matrix exhibits higher chemical inertness and resistance to moisture / oxygen erosion, a characteristic that significantly improves the material's air stability. Meanwhile, O... 2- In Li + The introduction of this material near the site can suppress the reaction between the interface and moisture or oxygen in the air, forming a protective effect similar to a passivation layer, and significantly improving the chemical stability of the material in air. Meanwhile, in the Li-based LPSC solid electrolyte of silver-germanium sulfide, [further details about the Li-based LPSC solid electrolyte are needed for accurate translation]. + Ca-doped at site 2+ Mg 2+ and Cu 2+ At least one of them, in S 2- O-doped at position 0 2- It can also create a localized alkaline environment inside, reducing... The probability of diffusion and acid degradation reactions is reduced, decreasing the material's reactivity in air and further enhancing its chemical stability, allowing it to maintain low conductivity decay even in environments with high relative humidity. Furthermore, the molar ratio of M to O is maintained at 1:1 to achieve charge balance and defect compensation within the crystal structure. This equimolar doping strategy not only suppresses structural distortion but also helps form stable MO local structural units, enhancing lattice order. Further, co-doping with Cl and Br at a 7:3 molar ratio creates a local polarization modulation effect in the crystal boundary region. It exhibits a strong electron enrichment effect, which can promote lithium-ion migration at grain boundaries; and The larger radius, after doping, induces local strain, which is beneficial for grain boundary passivation and improved polarization symmetry. A fixed Cl:Br molar ratio maintains crystal structure integrity while reducing charge inhomogeneity at grain boundaries, further reducing the impedance caused by the space charge layer. This achieves a reduction in sulfide solid electrolyte grain boundary impedance while maintaining high ionic conductivity and good air stability, thereby improving the electrochemical performance of all-solid-state lithium batteries. Furthermore, the numerical ranges of x and y within the scope of this application control Li... + Position and S2- The doping amount of different elements can easily adjust the crystal structure and electronic structure of the material, thereby improving the material's air stability and ionic conductivity. When x is less than the range of this application, i.e., x < 0.01, the doping amount is too low and cannot achieve the purpose of modification. When x is greater than the range of this application, i.e., x > 0.3, the doping amount is too high, which will destroy the material's own crystal structure, destroy the lithium-ion transport channels, and at the same time, there are impurities that cannot be doped into the crystal lattice, causing the material's conductivity to drop rapidly. When y is less than the range of this application, i.e., y < 0.5, the halogen content is too low, and the material's ionic conductivity will drop significantly. When y is greater than the range of this application, i.e., y > 2, the halogen content is too high, which will also destroy the material's crystal structure and cause the material's ionic conductivity to drop significantly. Furthermore, by limiting the x / y ratio to the range of 0.008 to 0.24, it is possible to introduce an appropriate amount of defects to optimize the lithium-ion migration channels while ensuring crystal stability. If x / y deviates from this range, it may lead to excessive enrichment of MO bonds or unbalanced defect density in the local crystal, thereby inducing grain boundary stress concentration and causing an increase in grain boundary impedance.

[0026] In solid-state electrolyte materials, grain boundary structure is one of the key factors affecting lithium-ion conductivity. Grain boundary impedance typically originates from defect enrichment, polarization accumulation, and structural distortion at the grain interface, exhibiting high locality and complexity. Its magnitude depends not only on the overall material composition but also on various microscopic factors such as the spatial distribution of elements at the grain boundaries, the type of defects at the grain boundaries, and the influence of doping on the crystal stress field. Ionic conductivity, on the other hand, reflects the overall lithium-ion migration capacity of the material and is a combined value of intra-grain conductivity and grain boundary conductivity. In contrast, ionic conductivity reflects the average lithium-ion migration capacity throughout the material and is often considered a macroscopic comprehensive indicator. Although ionic conductivity can indirectly reflect the overall conductivity of a material, in systems with complex grain boundary structures and sophisticated doping strategies, even if different materials exhibit similar conductivity, structural differences in their grain boundary regions can still lead to significantly different impedance behaviors. Therefore, similar ionic conductivity does not necessarily mean that grain boundary impedance is at the same level.

[0027] When the ionic conductivity levels are basically the same, the advantages of sulfide solid electrolytes with lower grain boundary impedance are: (1) First, the reduction of grain boundary impedance helps to reduce interfacial polarization and space charge layer effect, and improve the interfacial stability during ion migration, which is especially suitable for all-solid-state battery systems under high-rate charge and discharge conditions. (2) Second, lower grain boundary impedance can significantly reduce the interfacial decay rate of materials during long-term cycling, thereby improving the consistency and cycle life of the battery. (3) In practical applications, grain boundary impedance is one of the key factors limiting the compaction performance and electrode matching performance of electrolytes. Lower grain boundary impedance means that the electrolyte can still maintain excellent overall ion channel connectivity under relatively low density or small particle size conditions, which is beneficial to large-scale preparation and process tolerance.

[0028] In summary, the solid electrolyte material obtained by this invention within the aforementioned elemental ratio window exhibits a stable cell structure, sufficient passivation of grain boundary defects, and continuous ion migration channels, demonstrating excellent electrochemical performance. At room temperature, its grain boundary impedance is below 100Ω, and its ionic conductivity reaches [value missing]. above.

[0029] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-2x-y PCa x S 6-x- y O x Cl 0.7y Br 0.3y 0.02 ≤ x ≤ 0.1, 1.25 ≤ y ≤ 1.5. For example, x can be 0.02, 0.05, 0.07, 0.1, or any range of two of these values, and y can be 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or any range of two of these values. In the Li-silver-germanium LPSC solid electrolyte... + Ca-doped at site 2+ In S 2- O-doped at position 0 2- Furthermore, the values ​​of x and y are within the ranges mentioned above, which can further improve the air stability and ionic conductivity of sulfide solid electrolytes and reduce grain boundary impedance, thereby further improving the electrochemical performance of all-solid-state lithium batteries.

[0030] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-2x-y PMg x S 6-x- y O x Cl 0.7y Br 0.3y0.03 ≤ x ≤ 0.07, 1.25 ≤ y ≤ 1.5. For example, x can be 0.03, 0.05, 0.07, or any range of two of these values, and y can be 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or any range of two of these values. In the Li-silver sulfide germanium LPSC solid electrolyte... + Mg-doped site 2+ In S 2- O-doped at position 0 2- Furthermore, the values ​​of x and y are within the ranges mentioned above, which can further improve the air stability and ionic conductivity of sulfide solid electrolytes and reduce grain boundary impedance, thereby further improving the electrochemical performance of all-solid-state lithium batteries.

[0031] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-2x-y PCu x S 6-x- y O x Cl 0.7y Br 0.3y 0.05 ≤ x ≤ 0.1, 1.5 ≤ y ≤ 1.75. For example, x can be 0.05, 0.07, 0.1, or any two of these values, and y can be 1.5, 1.65, 1.7, 1.75, or any two of these values. In the Li-silver ore LPSC solid electrolyte... + Cu-doped site 2+ In S 2- O-doped at position 0 2- Furthermore, the values ​​of x and y are within the ranges mentioned above, which can further improve the air stability and ionic conductivity of sulfide solid electrolytes and reduce grain boundary impedance, thereby further improving the electrochemical performance of all-solid-state lithium batteries.

[0032] In one embodiment of this application, the sulfide solid electrolyte is Li 5.65 PCa 0.05 S 4.7 O 0.05 Cl 0.87 5Br 0.375 Li 5.71 PCa 0.02 S 4.73 O 0.02 Cl 0.875 Br 0.375 Li 5.55 PCa 0.1 S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.4 PCa0.0 5S 4.45 O 0.05 Cl 1.05 Br 0.45 Li 5.65 PMg 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 Li 5.4 PCu 0.05 S 4.45 O 0.05 Cl 1.05 Br 0.45 The above-mentioned sulfide solid electrolytes offer higher air stability, ionic conductivity, and lower grain boundary impedance.

[0033] In one embodiment of this application, the cell parameters of the sulfide solid electrolyte satisfy: a=b=c=9.85~10 Å. Rietveld fitting calculations using X-ray diffraction patterns revealed that within the doping ratio range defined in this invention (0.01≤x≤0.3, 0.5≤y≤2, 0.008≤x / y≤0.24), the cell parameter a of the obtained material stably remains in the range of 9.85~10.00 Å, exhibiting a significant lattice expansion trend. This cell expansion demonstrates, on the one hand, the crystal structure reconstruction caused by MO co-doping, and on the other hand, facilitates the expansion of lithium-ion migration channels and reduces stress concentration at grain boundary defects, forming an important structural basis for achieving low grain boundary impedance.

[0034] In one embodiment of this application, the particle size of the sulfide solid electrolyte satisfies the following conditions: 0.5µm < D50 < 3µm, 6.5µm < D90 < 9µm. The particle size of the sulfide solid electrolyte in this application falls within the above range, resulting in good processability.

[0035] In one embodiment of this application, the ionic conductivity of the sulfide solid electrolyte is >5 mS / cm. Preferably, the ionic conductivity of the sulfide solid electrolyte is >5.5 mS / cm; more preferably, the ionic conductivity of the sulfide solid electrolyte is >6 mS / cm; even more preferably, the ionic conductivity of the sulfide solid electrolyte is >7 mS / cm. The sulfide solid electrolyte of this application has low grain boundary resistance and high ionic conductivity, which can improve the electrochemical performance of all-solid-state lithium batteries when applied to them.

[0036] This application does not impose any particular limitation on the preparation method of sulfide solid electrolyte, as long as it can achieve the purpose of this application. For example, the preparation method of sulfide solid electrolyte may include: mixing raw materials and solvent under an inert atmosphere to obtain a suspension; drying the suspension by vacuum distillation to obtain a solid electrolyte precursor mixture; and sintering the solid electrolyte precursor mixture to obtain the sulfide solid electrolyte.

[0037] This application does not specifically limit the types of raw materials and solvents, as long as they can achieve the purpose of this application. For example, the raw materials can be Li₂S, P₂S₅, LiCl, LiBr and basic oxides (e.g., CaO, MgO, CuO), and the solvents can be n-hexane, benzene, toluene, cyclohexane, n-pentane, cyclopentane, and dimethyl carbonate. Because Ca... 2+ Mg 2+ Cu 2+ It is a divalent cation, replacing the monovalent cation. This can introduce charge imbalance, therefore, it is necessary to appropriately reduce the amount of charge in the raw material design. The amount of [specific substance] used is adjusted to maintain overall charge balance and crystal structure stability. For example, while keeping the P and S compositions constant, [the amount of P and S used is reduced]. Increasing the proportion of Ca, Mg, or Cu sources can guide the Ca... 2+ Mg 2+ or Cu 2+ Prioritize entry into lithium sites without disrupting them. Frame unit.

[0038] This application does not impose any particular limitation on the amount of raw materials and solvents added, as long as the purpose of this application is achieved. For example, the mass ratio of raw materials to solvent is 1:1 to 3. This application does not impose any particular limitation on the method of vacuum distillation drying, as long as the purpose of this application is achieved. For example, the vacuum distillation drying temperature is 40℃ to 60℃, and the vacuum degree is -0.09 MPa to -0.10 MPa. This application does not impose any particular limitation on the sintering method, as long as the purpose of this application is achieved. For example, a tubular furnace programmed heating method is used, first heating at 150 to 300℃ for 2 to 4 hours, then heating at 500 to 600℃ for 4 to 6 hours for sintering to obtain a sulfide solid electrolyte.

[0039] The second aspect of this application provides an all-solid-state lithium battery, which includes a positive electrode, a negative electrode, and a sulfide solid electrolyte as described in the first aspect of this application.

[0040] This application does not impose any particular limitations on the positive and negative electrodes in an all-solid-state lithium battery, as long as they achieve the purpose of this application. For example, the positive electrode includes a positive electrode active material, a sulfide solid electrolyte, and conductive carbon. The positive electrode active material can be a ternary positive electrode such as NCM523, NCM622, NCM712, NCM811, or NCM90, or it can be lithium iron phosphate or lithium manganese iron phosphate (LiMn). x Fe 1-x PO4, LiCoO2 materials, lithium-rich manganese-based materials (aLi2MnO3•(1-a)LiMO2) (0≤a≤1, M is at least one of Ni, Co or Mn), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 Materials such as O4, etc., the sulfide solid electrolyte is the electrolyte in this application, and the conductive carbon can be superconducting carbon black (Super P) or carbon black; the mass ratio of the positive electrode active material, the sulfide solid electrolyte, and the conductive carbon can be 60~80%:10~35%:3~10%. The negative electrode includes lithium indium alloy, lithium metal, graphite, and silicon carbon. Preferably, the all-solid-state lithium battery also includes a current collector disposed on the positive electrode material side; the current collector can be carbon-coated aluminum foil or pure aluminum foil.

[0041] This application does not impose any particular limitation on the preparation method of all-solid-state lithium batteries, as long as it can achieve the purpose of this application. For example, the preparation method of all-solid-state lithium batteries includes: mixing positive electrode active material, sulfide solid electrolyte and conductive carbon to obtain composite positive electrode powder; loading the sulfide solid electrolyte into a solid battery mold for a first pressing to obtain an electrolyte layer; adding the composite positive electrode powder to one side of the electrolyte layer for a second pressing to obtain a positive electrode; adding the negative electrode material to the other side of the electrolyte layer for a third pressing to obtain an all-solid-state lithium battery.

[0042] The sulfide solid electrolyte of this application has high ionic conductivity, high air stability and low grain boundary impedance, and thus the all-solid-state lithium battery including the sulfide solid electrolyte of this application has excellent electrochemical performance.

[0043] Example

[0044] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0045] Test methods and equipment:

[0046] Ionic conductivity testing and grain boundary impedance testing

[0047] In an argon-filled glove box, 100 mg of sulfide solid electrolyte powder was weighed and placed in a mold battery (Wuhan Chuangneng CN-01) with stainless steel sheets with a diameter of 9 mm at both ends. The battery was then pressurized to 200 MPa and the electrolyte sheet thickness was 1 mm. The mold battery was then used for AC impedance spectroscopy testing.

[0048] In an argon-filled glove box, 110 mg of sulfide solid electrolyte powder was weighed and placed in a mold battery (Wuhan Chuangneng CN-01) with stainless steel sheets with a diameter of 9 mm at both ends. The battery was then pressurized to 300 MPa and the electrolyte sheet thickness was 1 mm. The mold battery was then used for AC impedance spectroscopy testing.

[0049] Electrochemical impedance spectroscopy (EIS) was used to determine the electrolyte impedance at 25°C. On an electrochemical workstation (ChenHua, CHI630E), a DC polarization voltage of 1V was applied to measure the impedance, with an amplitude of 50mV and a frequency range of 1Hz to 10MHz. The ionic conductivity of the electrolyte material was calculated using the following formula:

[0050]

[0051] Where σ is the ionic conductivity, in units of σ / σ. L represents the thickness of the electrolyte sheet, in cm; R represents the electrolyte resistance, in units of... S represents the effective contact area between the stainless steel sheet and the electrolyte powder, in cm². 2 .

[0052] To further distinguish between bulk phase and grain boundary contributions, an equivalent circuit was fitted to the Nyquist diagram, using a series R... b -CPE b (body phase) and R gb -CPE gb (Grain boundary) unit, where R b -CPE b and R gb -CPE gb These correspond to bulk resistance and grain boundary resistance, respectively, with CPE being a constant-phase element. Grain boundary impedance R gb Obtained through fitting in the mid-frequency region.

[0053] Air stability test

[0054] Air stability is primarily described by the retention rate of the ionic conductivity of sulfide solid electrolytes when exposed to air.

[0055] Ion conductivity retention rate test: The ionic conductivity of the sulfide solid electrolyte was tested using the above-described ionic conductivity test method and recorded as the conductivity before exposure. Then, at a dew point temperature of -40℃, the sulfide solid electrolyte was directly exposed to air, and the sulfide solid electrolyte was recovered after 12 hours, 24 hours, and 48 hours, respectively. The ionic conductivity was then tested using the above-described ionic conductivity test method and recorded as the conductivity after exposure. Conductivity retention rate = Conductivity after exposure / Conductivity before exposure × 100%.

[0056] X-ray powder diffraction test

[0057] X-ray powder diffraction (XRD) was used to analyze the crystal structure of the samples. A Bruker D8 Advance diffractometer equipped with Cu Kα radiation (λ = 1.5406 Å) as the light source was employed. The test parameters were set as follows: tube voltage 40 kV, tube current 40 mA, scanning range 2θ = 5°–90°, scanning step size 0.02°, and scanning rate 5° / min. The samples were uniformly dispersed in powder form on a glass slide without a diffraction background, and compaction was performed to reduce the influence of interparticle voids on the diffraction results.

[0058] The XRD data were processed and analyzed using Jade software. First, the raw data was imported into the software, and background subtraction and signal optimization were performed. The peak search function automatically identified the diffraction peak positions, and a Gaussian function was selected for peak shape fitting. Parameters were adjusted to ensure the fitted curve matched the experimental data. After fitting, the software directly output the peak area I of the diffraction peaks.

[0059] Calculation of the ratio of impurity peak to main peak in XRD after 24 hours of exposure: The sulfide solid electrolyte was directly exposed to air for 24 hours at a dew point temperature of -40℃. The sulfide solid electrolyte was recovered, and the peak areas of the impurity peak and the main peak were tested using the above method, and the ratio between the two was calculated.

[0060] Unit cell parameter analysis: XRD data were processed and analyzed using Jade software. First, the raw data was imported into the software, and after background subtraction and signal optimization, it was exported as a text file. The text file was then imported into the refinement software FullProf. An initial model was established based on the known crystal structure of the sample, and preliminary unit cell parameters and space group were input. Instrument parameters such as zero-point offset and sample displacement were adjusted to complete the initial fitting.

[0061] During the refinement process, peak shape parameters (such as peak width and peak shape factor), background functions, cell parameters (a, b, c, α, β, γ), and atomic positions and occupancy are gradually optimized to achieve final convergence of the fit. The fitting results are evaluated based on the goodness of fit Chi2, while the residual spectrum is used to determine the quality of the fit. Once the refinement results converge (Chi2 < 3), the cell parameters a, b, and c can be obtained from the software's output text.

[0062] Particle size distribution testing

[0063] The surface morphology and particle size distribution of the sulfide solid electrolyte were observed using a Zeiss Sigma 300 scanning electron microscope (SEM). The microscope was fixed on the sample stage, which was placed in a vacuum chamber. The accelerating voltage, beam current, and working distance of the SEM were adjusted to optimize the imaging effect. Surface morphology information was acquired using a secondary electron detector. The particle size of the sulfide solid electrolyte in the SEM images was measured and statistically analyzed using ImageJ software to obtain its particle size distribution.

[0064] Electrochemical performance testing

[0065] Electrochemical performance testing mainly involves assembling a solid-state battery with a sulfide solid electrolyte and a layered high-nickel NCM811 ternary cathode material.

[0066] Preparation of all-solid-state battery: (1) Preparation of positive electrode material: NCM811 positive electrode active material, sulfide solid electrolyte of this application and conductive carbon (Super P) are mixed in a mass ratio of 75:20:5 and ground in a mortar for 30 minutes to obtain composite positive electrode powder; (2) Negative electrode material: lithium indium alloy (lithium content is 30wt%); (3) Sulfide solid electrolyte: sulfide solid electrolyte of this application is used; (4) Assembly of all-solid-state battery: In a glove box filled with argon, 100mg of sulfide solid electrolyte is first weighed and added to a solid battery mold with an inner diameter of 10mm, and pressure is applied to 300Mpa and held for 1 minute to obtain an electrolyte layer; 10mg of composite positive electrode powder is added to one side of the electrolyte layer, covered with 15µm aluminum foil, and pressure is applied to 100Mpa and held for 1 minute to obtain a positive electrode; then 100µm lithium indium alloy negative electrode material is added to the other side, and 50 After applying a slight pressure of MPa, the mold is assembled to obtain an assembled all-solid-state lithium-ion battery. After verifying its airtightness, it is taken out of the glove box and transferred to the battery testing system for electrochemical charge-discharge cycle testing.

[0067] Charge / discharge testing: The charge / discharge performance of the battery was tested using the LAND battery testing system at a constant temperature of 25°C. Constant current charge / discharge testing directly reflects the electrochemical performance of the active materials in the battery and is an important means of evaluating the practical application potential of materials. In the test, the current density is based on the material mass, and the specific capacity corresponding to 1C is defined as... 0.2C is During the 0.2C rate cycling process, the battery is first charged from 2.6V to a preset cutoff voltage (3.9V, 4.0V, 4.1V, 4.2V, 4.3V, or 4.4V) using a constant current. The highest voltage at which the battery can operate stably is selected as the cutoff voltage. Then, it is discharged at a constant current of 0.2C to 2.6V. The entire process is completed in constant current mode. The capacity retention rate (first-time effect) of the all-solid-state lithium-ion battery during the first charge-discharge process at 0.2C, the capacity retention rate after 200 cycles during the 0.2C charge-discharge cycle, and the number of cycles when the discharge capacity drops sharply (in this application, a sudden and rapid drop in discharge capacity refers to a sharp decrease in discharge capacity) are recorded.

[0068] The specific capacity during the first charge and discharge cycle of a battery is used to calculate the first discharge efficiency (first efficiency), which is calculated as follows: First efficiency = First discharge capacity / First charge capacity × 100%. This indicator can be used to assess the capacity loss caused by irreversible reactions (such as electrolyte decomposition or solid electrolyte interfacial film formation) that occur in the material during the first cycle.

[0069] Capacity retention rate after 200 cycles = (200th discharge capacity / first discharge capacity) × 100%.

[0070] Example 1

[0071] In an Ar atmosphere, Li₂S, P₂S₅, LiCl, LiBr, and the basic oxide CaO were weighed in a molar ratio of 2.2: 0.5: 0.875: 0.375: 0.05. 1 kg of the raw material was mixed with 1 kg of n-hexane to obtain a suspension. The suspension was then subjected to vacuum distillation at 40°C and a vacuum of -0.098 MPa to obtain a solid electrolyte precursor mixture. In an Ar atmosphere, using a tubular furnace with programmed heating, the obtained solid electrolyte precursor mixture was first heated at 200°C for 3 hours, then at 550°C for 5 hours to obtain a sulfide solid electrolyte (Li₂S₅). 5.65 PCa 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 Its X-ray diffraction pattern is as follows: Figure 1 As shown.

[0072] Examples 2 to 9

[0073] Except for adjusting the molar ratio of the raw materials to obtain sulfide solid electrolytes with different chemical formulas as shown in Table 1, the remaining steps are the same as in Example 1.

[0074] Example 10

[0075] In addition to replacing "basic oxide CaO" with "basic oxide MgO", a sulfide solid electrolyte (Li) is obtained. 5.6 5PMg 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 Except for the step described in Example 1, the remaining steps are the same. Its X-ray diffraction pattern is as follows: Figure 2 As shown.

[0076] Example 11

[0077] In addition to replacing "basic oxide CaO" with "basic oxide CuO" and adjusting the molar ratio of the raw materials, a sulfide solid electrolyte (Li) was obtained. 5.4 PCu 0.05 S 4.45 O 0.05 Cl 1.05 Br 0.45 Except for the X-ray diffraction pattern, the remaining steps are the same as in Example 1. Its X-ray diffraction pattern is as follows: Figure 3 As shown.

[0078] Example 12

[0079] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, basic oxide CaO, and basic oxide MgO in a molar ratio of 2.2: 0.5: 0.875: 0.375: 0.025: 0.025", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr, basic oxide CaO, and basic oxide MgO) is obtained. 5.65 PCa 0.02 5Mg 0.025 S 4.7 O 0.05 Cl 0.875 Br 0.375 Except for the steps in Example 1, the remaining steps are the same.

[0080] Example 13

[0081] The sulfide solid electrolyte is the same as in Example 1, and the positive electrode active material used for electrochemical performance testing is Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2, with graphite as the negative electrode material, and the remaining electrochemical performance testing steps are the same as the above testing methods.

[0082] Example 14

[0083] The sulfide solid electrolyte is the same as in Example 1, and the positive electrode active material used for electrochemical performance testing is LiFe. 0.5 Mn 0.5 PO4, with silicon-carbon as the negative electrode material, and the remaining electrochemical performance testing procedures are the same as those described above.

[0084] Comparative Examples 1 to 6

[0085] Except for adjusting the molar ratio of the raw materials to obtain sulfide solid electrolytes with different chemical formulas as shown in Table 1, the remaining steps are the same as in Example 1.

[0086] Comparative Example 7

[0087] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr and basic oxide CaO in a molar ratio of 2.2: 0.5: 0.625: 0.625: 0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr and basic oxide CaO) is obtained. 5.65 PCa 0.05 S 4.7 O 0.05 Cl 0.625 Br 0.625 Except for the steps in Example 1, the remaining steps are the same.

[0088] Comparative Example 8

[0089] By replacing the raw materials with a molar ratio of Li₂S, P₂S₅, LiCl, and LiBr of 2.25: 0.5: 0.875: 0.375, a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, and LiBr) was obtained. 5.75 PS 4.75 Cl 0.875 Br 0.375 Except for the steps in Example 1, the remaining steps are the same.

[0090] Comparative Example 9

[0091] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, and CaS in a molar ratio of 2.2: 0.5: 0.875: 0.375: 0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr, and CaS) is obtained. 5.65 PCa 0.05 S 4.75 Cl 0.875 Br 0.375 Except for the steps in Example 1, the remaining steps are the same.

[0092] Comparative Example 10

[0093] Besides adjusting the molar ratio of the raw materials, a sulfide solid electrolyte (Li) is obtained. 5.73 PCa 0.01 S 4.75 Cl 0.875 Br 0.375 Except for ), the remaining steps are the same as those in Comparative Example 9.

[0094] Comparative Example 11

[0095] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, P₂O₅ in a molar ratio of 2.25: 0.48: 0.875: 0.375: 0.02", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr, P₂O₅) is obtained. 5.75 PS 4.65 O 0.1 Cl 0.875 Br 0.375 Except for the steps in Example 1, the remaining steps are the same.

[0096] Comparative Example 12

[0097] Besides adjusting the molar ratio of the raw materials, a sulfide solid electrolyte (Li) is obtained. 5.75 PS 4.73 O 0.02 Cl 0.875 Br 0.375 Except for ), the rest are the same as Comparative Example 11.

[0098] Comparative Example 13

[0099] Besides adjusting the molar ratio of the raw materials, a sulfide solid electrolyte (Li) is obtained. 5.3 Ca 0.05 PS 4.35 O 0.05 Cl 1.4 Br 0.2 Except for ), the rest is the same as in Example 1.

[0100] Comparative Example 14

[0101] Besides adjusting the molar ratio of the raw materials, a sulfide solid electrolyte (Li) is obtained. 5.3 Mg 0.05 PS 4.35 O 0.05 Cl 1.4 Br 0.2 Except for ), the rest is the same as in Example 10.

[0102] Comparative Example 15

[0103] In addition to replacing "basic oxide CaO" with "ZnO" and adjusting the molar ratio of the raw materials, a sulfide solid electrolyte (Li) was obtained. 5.3 Zn0.05 PS 4.35 O 0.05 Cl 1.4 Br 0.2 Except for the steps in Example 1, the remaining steps are the same.

[0104] The preparation parameters and performance parameters of the sulfide solid electrolytes of each embodiment and comparative example are shown in Tables 1 and 2, and the performance parameters of the all-solid-state batteries obtained therefrom are shown in Tables 3 and 4.

[0105] Table 1 Preparation parameters of sulfide solid electrolytes

[0106]

[0107] In Table 1, " / " indicates that there are no relevant parameters.

[0108] Table 2 Performance parameters of sulfide solid electrolytes

[0109]

[0110] Table 3 Performance parameters of all-solid-state batteries

[0111]

[0112] Table 4 Performance parameters of all-solid-state batteries of different systems

[0113]

[0114] As shown in Table 1, the cell parameters of the sulfide solid electrolyte of this application satisfy a=b=c=9.85~10Å; the particle size of the sulfide solid electrolyte satisfies 0.5µm<D50<3µm, 6.5µm<D90<9µm; as shown in Table 2, the sulfide solid electrolyte of this application has high ionic conductivity, good air stability and low grain boundary impedance. Its ionic conductivity is >5mS / cm, the conductivity retention rate is ≥82% after 12 hours of exposure at a dew point temperature of -40℃, the conductivity retention rate is ≥77% after 24 hours of exposure at a dew point temperature of -40℃, the conductivity retention rate is ≥70% after 48 hours of exposure at a dew point temperature of -40℃, the ratio of impurity peak to main peak is ≤0.18% after 24 hours of exposure at a dew point temperature of -40℃, and its grain boundary impedance is within 100Ω. As shown in Table 3, the sulfide solid electrolyte of this application, when applied to all-solid-state lithium batteries, can improve the initial discharge efficiency, cycle performance, and cutoff voltage of the all-solid-state lithium batteries. Its initial discharge efficiency is ≥80.4%, capacity retention after 200 cycles at 0.2C is ≥95.1%, the number of cycles at 0.2C is ≥331, and the cutoff voltage is ≥4.2V. As shown in Table 4, when the sulfide solid electrolyte of this application is applied to all-solid-state lithium batteries of different systems, the resulting all-solid-state lithium batteries exhibit high initial discharge efficiency, good cycle performance, and high cutoff voltage. In summary, the sulfide solid electrolyte of this application achieves improved electrochemical performance of all-solid-state lithium batteries by reducing grain boundary impedance while maintaining high ionic conductivity and good air stability.

[0115] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A sulfide solid electrolyte with the chemical formula Li 7-2x-y PM x S 6-x-y O x Cl 0.7y Br 0.3y M is at least one of Ca, Mg and Cu, 0.01≤x≤0.3, 0.5≤y≤2, 0.008≤x / y≤0.24, the molar ratio of M to O is 1:1, and the molar ratio of Cl to Br is 7:

3. The sulfide solid electrolyte has a grain boundary resistance of 20Ω to 100Ω at 25°C.

2. The sulfide solid electrolyte according to claim 1, wherein, 0.02≤x≤0.1, 1.25≤y≤1.

75.

3. The sulfide solid electrolyte according to claim 1, wherein, The chemical formula of the sulfide solid electrolyte is Li 7-2x-y PCa x S 6-x-y O x Cl 0.7y Br 0.3y , 0.02≤x≤0.1, 1.25≤y≤1.

5.

4. The sulfide solid electrolyte according to claim 1, wherein, The chemical formula of the sulfide solid electrolyte is Li 7-2x-y PMg x S 6-x-y O x Cl 0.7y Br 0.3y , 0.03≤x≤0.07, 1.25≤y≤1.

5.

5. The sulfide solid electrolyte according to claim 1, wherein, The chemical formula of the sulfide solid electrolyte is Li 7-2x-y PCu x S 6-x-y O x Cl 0.7y Br 0.3y , 0.05≤x≤0.1, 1.5≤y≤1.

75.

6. The sulfide solid electrolyte according to claim 1, wherein, The sulfide solid electrolyte is Li 5.65 PCa 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 Li 5.71 PCa 0.02 S 4.73 O 0.02 Cl 0.875 Br 0.375 Li 5.55 PCa 0.1 S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.4 PCa 0.05 S 4.45 O 0.05 Cl 1.05 Br 0.45 Li 5.65 PMg 0.05 S 4.7 O 0.05 Cl 0.875 Br 0.375 Li 5.4 PCu 0.05 S 4.4 5O 0.05 Cl 1.05 Br 0.45 .

7. The sulfide solid electrolyte according to claim 1, wherein, The cell parameters of the sulfide solid electrolyte satisfy: a=b=c=9.85~10Å.

8. The sulfide solid electrolyte according to claim 1, wherein, The particle size of the sulfide solid electrolyte satisfies the following conditions: 0.5µm < D50 < 3µm, 6.5µm < D90 < 9µm.

9. The sulfide solid electrolyte according to claim 1, wherein, The ionic conductivity of the sulfide solid electrolyte is >5 mS / cm.

10. An all-solid-state lithium battery, comprising a positive electrode, a negative electrode, and a sulfide solid electrolyte as described in any one of claims 1 to 9.

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