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. 7‑4x‑y PM x S 6‑2x‑y O 2x X y M is at least one of the variable-valence rare earth elements Ce, Eu, Pr, and Sm, and X is at least one of the halogens, with 0.005 ≤ x ≤ 0.3 and 0.5 ≤ y ≤ 2. The molar ratio of M to O is 1:2. This application improves the structural stability of the sulfide solid electrolyte under complex electrochemical environments by doping the Li site with the variable-valence rare earth element M and the S site with O, and by controlling the molar ratio of M to O to 1:2. This helps to suppress its chemical degradation behavior during cycling, and also improves the air stability and ionic conductivity of the sulfide solid electrolyte, thereby improving the cycle life and reliability of the all-solid-state lithium battery.

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] Sulfide solid electrolytes are considered a core material for next-generation all-solid-state lithium batteries due to their excellent ionic conductivity and flexible mechanical properties. However, during long-term charge-discharge cycles, sulfide solid electrolytes are susceptible to interfacial side reactions, structural degradation, and fluctuations in the electrochemical redox environment, leading to material instability, increased interfacial impedance, and ultimately limiting battery life and cycle stability. Particularly under high-voltage or high-current-density operating conditions, the sulfur component in the electrolyte is prone to oxidation or migration, forming a non-lithium-ion conductive secondary phase, significantly deteriorating the performance of all-solid-state lithium batteries. Furthermore, sulfide solid electrolytes decompose readily 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 deficiency severely limits the reliability of sulfide solid electrolytes in industrial production, storage, transportation, and practical applications.

[0003] Therefore, improving the structural stability of sulfide solid electrolytes under complex electrochemical environments, inhibiting their chemical degradation during cycling, and simultaneously improving the air stability of sulfide solid electrolytes are key issues that urgently need to be addressed to enhance the lifespan and reliability of all-solid-state lithium batteries. Summary of the Invention

[0004] The purpose of this application is to provide a sulfide solid electrolyte and an all-solid-state lithium battery to improve the structural stability of the sulfide solid electrolyte under complex electrochemical environments, suppress its chemical degradation during cycling, and simultaneously improve the air stability and ionic conductivity of the sulfide solid electrolyte, thereby enhancing the cycle life and reliability of the all-solid-state lithium battery. The specific technical solution is as follows:

[0005] The first aspect of this application provides a sulfide solid electrolyte with the chemical formula Li. 7-4x-y PM x S 6-2x- y O 2x X y M is at least one of the variable-valence rare earth elements Ce, Eu, Pr and Sm, X is at least one of the halogens, 0.005≤x≤0.3, 0.5≤y≤2, and the molar ratio of M to O is 1:2.

[0006] In one embodiment of this application, 0.02≤x≤0.15, 1.25≤y≤1.75.

[0007] In one embodiment of this application, X is at least one of Cl, Br, and I.

[0008] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x-y PM x S 6-2x- y O 2x X' 0.7y X'' 0.3y X' or X'' is independently Cl, Br or I, and X' is different from X''.

[0009] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x-y PM x S 6-2x- y O 2x Cl 0.7y Br 0.3y .

[0010] In one embodiment of this application, the sulfide solid electrolyte is Li 5.55 PCe 0.05 S 4.65 O 0.1 Cl 0.87 5Br 0.375 Li 5.67 PCe 0.02 S 4.71 O 0.04 Cl 0.875 Br 0.375 Li 5.05 PCe 0.05 S 4.15 O 0.1 Cl 1.225 Br 0.525 Li 5.55 PEu 0.0 5S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.55 PPr 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.55 PSm 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 .

[0011] In one embodiment of this application, the cell parameters of the sulfide solid electrolyte satisfy: a=b=c=9.85~10Å.

[0012] In one embodiment of this application, the particle size of the sulfide solid electrolyte satisfies: 0.5µm < D50 < 4µm, 7µm < D90 < 10µm.

[0013] In one embodiment of this application, the ionic conductivity of the sulfide solid electrolyte is >5 mS / cm.

[0014] 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.

[0015] The beneficial effects of this application are:

[0016] This application provides a sulfide solid electrolyte and an all-solid-state lithium battery. The sulfide solid electrolyte has the chemical formula Li. 7-4x-y PM x S 6-2x-y O 2x X y M is at least one of the variable-valence rare earth elements Ce, Eu, Pr, and Sm, and X is at least one of the halogens, with 0.005 ≤ x ≤ 0.3 and 0.5 ≤ y ≤ 2. The molar ratio of M to O is 1:2. Doping the Li site with the variable-valence rare earth element M and the S site with O in the sulfide solid electrolyte, and controlling the molar ratio of M to O to 1:2, improves the structural stability of the sulfide solid electrolyte under complex electrochemical environments, which helps to suppress its chemical degradation behavior during cycling. It also improves the air stability and ionic conductivity of the sulfide solid electrolyte, thereby enhancing the cycle life and reliability of the all-solid-state lithium battery.

[0017] 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

[0018] 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.

[0019] Figure 1 The sulfide solid electrolyte (Li) prepared in Example 1 5.55 PCe 0.05 S 4.65 O 0.1 Cl 0.875 Br0.375 X-ray diffraction pattern of )

[0020] Figure 2 The sulfide solid electrolyte (Li) prepared in Example 9 5.55 PEu 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 X-ray diffraction pattern of )

[0021] Figure 3 The sulfide solid electrolyte (Li) prepared in Example 10 5.55 PPr 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 X-ray diffraction pattern of )

[0022] Figure 4 The sulfide solid electrolyte (Li) prepared in Example 11 5.55 PSm 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 X-ray diffraction pattern of )

[0023] Figure 5 The sulfide solid electrolyte (Li) prepared for Comparative Example 5 5.75 PS 4.75 Cl 0.875 Br 0.375 X-ray diffraction pattern of ). Detailed Implementation

[0024] 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.

[0025] The first aspect of this application provides a sulfide solid electrolyte with the chemical formula Li. 7-4x-y PM x S 6-2x- y O 2x X yM is at least one of the variable-valence rare earth elements Ce, Eu, Pr, and Sm, and X is at least one of the halogens. The molar ratio of M to O is 1:2, provided that 0.005 ≤ x ≤ 0.3 and 0.5 ≤ y ≤ 2. Preferably, 0.02 ≤ x ≤ 0.15 and 1.25 ≤ y ≤ 1.75. For example, x can be 0.005, 0.02, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, or any range of two values ​​therein, and y can be 0.5, 1, 1.25, 1.5, 1.75, 2, or any range of two values ​​therein.

[0026] This application involves doping the Li site of a sulfide solid electrolyte with at least one of the variable-valence rare earth elements Ce, Eu, Pr, and Sm, and doping the S site with oxygen. Specifically, the rare earth element cations and oxygen anions participate in an ex-situ substitution reaction within the crystal structure, partially replacing lithium sites (Li) in the crystal lattice. + ) and sulfur sites (S 2- This allows for the introduction of stable components with redox buffering capabilities while maintaining the stability of the crystal structure. Rare earth cations have larger radii and higher valence states, thus replacing Li. + After placement, lithium-deficient regions and local charge rearrangements can be induced in the crystal, which helps optimize the lithium-ion migration path, suppress the accumulation of structural stress caused by local lithium richness or lithium deficiency, and thus improve structural integrity. O in rare earth oxides 2- Ion partial substitution of S 2- Following the doping site, the bonding ability between Li-O, PO, and MO can be enhanced, improving the chemical stability of the crystal framework and effectively reducing sulfur migration or oxidation during battery cycling, thus delaying structural degradation. Furthermore, doping with variable-valence rare earth elements possesses excellent reversible redox properties, dynamically absorbing or releasing electrons during battery charging and discharging, thereby forming an electron buffer within the material. This buffer balances electrochemical environment fluctuations, suppresses interfacial side reactions, and delays structural degradation. This mechanism helps stabilize the potential gradient at the electrolyte / electrode interface, maintaining interfacial integrity during long-term cycling. Through the synergistic effect of these multiple mechanisms, the sulfide solid electrolyte material provided in this application exhibits superior structural stability and interfacial compatibility during long-term cycling, significantly extending the lifespan of all-solid-state lithium batteries, and is particularly suitable for all-solid-state lithium battery systems operating under high-voltage conditions.

[0027] To further ensure the controllability and functionality of the doping effect, this application limits the molar ratio of rare earth element M to oxygen element O to 1:2, that is, each rare earth metal ion corresponds to two oxygen ions, thereby forming a stable doping effect in the material. or Type-dependent coordination structural unit. This proportional limitation effectively avoids [the following issues]. Excessive introduction of rare earth elements can lead to lattice expansion, formation of crystalline impurities, or disorder of anion sites. It also prevents the isolated existence of rare earth ions without stable coordination, which could induce a decrease in conductivity or accumulation of structural defects. Under this molar ratio, the formed rare earth-oxygen structure is not only stably embedded in the electrolyte lattice but also possesses a highly ordered local structure. This helps improve lattice rigidity and bonding energy, enhancing the resistance of sulfide solid electrolyte materials to external thermal disturbances and electrochemical stresses, thereby strengthening their structural stability. Furthermore, limiting the molar ratio of M to O to 1:2 ensures that rare earth element M forms a complete electron buffer structure in the lattice. During charging and discharging, it can absorb excess electrons through its reversible redox behavior, suppressing charge accumulation caused by interfacial side reactions, thus delaying interfacial aging and maintaining interfacial electrochemical stability. In contrast, if the molar ratio of M to O is unbalanced, it may cause rare earth enrichment, interfering with the lattice structure, or lead to instability of the buffer structure due to insufficient oxygen content, thereby weakening the overall performance of the material.

[0028] Furthermore, when rare earth ions replace Li + At that time, because the ionic radius of rare earth ions is greater than that of Li... + This leads to significant expansion and distortion of the local lattice, which increases the diffusion path of lithium ions and may form wider ion migration channels in local regions, thereby lowering the diffusion barrier of lithium ions and directly improving ionic conductivity. Furthermore, rare earth elements doped at Li sites have a significant impact on interfacial and air stability. Doping with rare earth elements can reduce the vacancy concentration at lithium sites, thereby reducing the chemical activity of the solid electrolyte when in contact with air and inhibiting decomposition reactions. Simultaneously, the variable valence properties of rare earth elements allow them to form a stable passivation layer in the interfacial region, reducing the sensitivity of sulfides to oxygen and water in the air, further reducing side reactions with air or electrode materials, thus slowing down oxidative degradation and improving stability. In addition, rare earth ions have variable oxidation states, which can reduce the adsorption and reactivity of moisture in the material through the introduction of oxygen vacancies, thereby further improving its stability in humid environments. This local regulation mechanism not only enhances the ion migration ability of the electrolyte but also significantly improves its interfacial and environmental stability.

[0029] Therefore, this application dops the Li site with variable-valence rare earth element M and the S site with element O in the sulfide solid electrolyte, and controls the molar ratio of element M to element O to be 1:2, which improves the structural stability of the sulfide electrolyte under complex electrochemical environment, helps to suppress its chemical degradation behavior during cycling, and also improves the air stability and ionic conductivity of the sulfide solid electrolyte, thereby improving the cycle life and reliability of the all-solid-state lithium battery.

[0030] When x is less than the range of this application, i.e., x < 0.005, 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 crystal structure of the material itself, destroy the lithium-ion transport channel, and at the same time, there are impurities that cannot be doped into the crystal lattice, causing the ionic conductivity of the material to drop rapidly. When y is less than the range of this application, i.e., y < 0.5, the halogen content is too low, causing the ionic conductivity of the material to 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 crystal structure of the material, causing the ionic conductivity of the material to drop significantly.

[0031] In one embodiment of this application, X is at least one of Cl, Br, and I.

[0032] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x-y PM x S 6-2x- y O 2x X' 0.7y X'' 0.3y X' or X'' is independently Cl, Br, or I, and X' is different from X''. By introducing two halogens into the sulfide solid electrolyte and controlling the molar ratio of the two halogens to 7:3, the coexistence of the two halogens can optimize the bonding state between grains during sintering, reduce stress concentration and defect formation at grain boundaries, and thus reduce grain boundary impedance. The synergistic effect of the two halogens can form a denser and more uniform grain interface, which helps to suppress interfacial reactions and improve the continuity of the overall ion conduction path.

[0033] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x-y PM x S 6-2x- y O 2x Cl 0.7y Br 0.3y The sulfide solid electrolyte of this application includes Cl and Br elements, and the molar ratio of Cl to B elements is controlled at 7:3. and The ionic radii differ ( The ionic radius is approximately 1.81 Å. The ionic radius is approximately 1.96 Å. At a 7:3 ratio, a larger radius can be appropriately introduced while ensuring that the crystal structure is not distorted. This helps alleviate internal stress in the crystal and maintain the stability of the face-centered cubic structure. However, if the Br content is too high, excessive lattice expansion will damage the Li. +Migration pathways; if the Br ratio is too low, the improvement in electrochemical performance is not significant. Studies have found that 7:3 is a balance point that takes into account both structural stability and functional optimization. Therefore, selecting the above-mentioned sulfide solid electrolyte can further improve the structural stability of the sulfide solid electrolyte under complex electrochemical environments, while also further improving the air stability and ionic conductivity of the sulfide solid electrolyte, thereby further improving the cycle life and reliability of all-solid-state lithium batteries.

[0034] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x- y PCe x S 6-2x-y O 2x Cl 0.7y Br 0.3y 0.02≤x≤0.15, 1.25≤y≤1.75. Doping Ce at the Li sites and oxygen at the S sites in the sulfide-germanium LPSC solid electrolyte, with x and y values ​​falling within the aforementioned ranges, can further improve the structural stability of the sulfide solid electrolyte under complex electrochemical environments. It also further enhances the air stability and ionic conductivity of the sulfide solid electrolyte, thereby further improving the cycle life and reliability of all-solid-state lithium batteries.

[0035] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x- y PEu x S 6-2x-y O 2x Cl 0.7y Br 0.3y 0.02≤x≤0.15, 1.25≤y≤1.75. Doping Eu at the Li sites and oxygen at the S sites in the silver-germanium sulfide LPSC solid electrolyte, with x and y values ​​falling within the aforementioned ranges, can further improve the structural stability of the sulfide solid electrolyte under complex electrochemical environments. It also further enhances the air stability and ionic conductivity of the sulfide solid electrolyte, thereby further improving the cycle life and reliability of all-solid-state lithium batteries.

[0036] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x- y PPr x S 6-2x-y O 2x Cl 0.7y Br 0.3y0.02≤x≤0.15, 1.25≤y≤1.75. Doping Pr at the Li sites and oxygen at the S sites in the sulfide-germanium LPSC solid electrolyte, with x and y values ​​falling within the aforementioned ranges, can further improve the structural stability of the sulfide solid electrolyte under complex electrochemical environments. It also further enhances the air stability and ionic conductivity of the sulfide solid electrolyte, thereby further improving the cycle life and reliability of all-solid-state lithium batteries.

[0037] In one embodiment of this application, the chemical formula of the sulfide solid electrolyte is Li. 7-4x- y PSm x S 6-2x-y O 2x Cl 0.7y Br 0.3y 0.02≤x≤0.15, 1.25≤y≤1.75. Doping Sm at the Li sites and oxygen at the S sites in the sulfide-germanium LPSC solid electrolyte, with x and y values ​​falling within the aforementioned ranges, can further improve the structural stability of the sulfide solid electrolyte under complex electrochemical environments. It also further enhances the air stability and ionic conductivity of the sulfide solid electrolyte, thereby further improving the cycle life and reliability of all-solid-state lithium batteries.

[0038] In one embodiment of this application, the sulfide solid electrolyte is Li 5.55 PCe 0.05 S 4.65 O 0.1 Cl 0.87 5Br 0.375 Li 5.67 PCe 0.02 S 4.71 O 0.04 Cl 0.875 Br 0.375 Li 5.05 PCe 0.05 S 4.15 O 0.1 Cl 1.225 Br 0.525 Li 5.55 PEu 0.0 5S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.55 PPr 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.55 PSm 0.05 S4.65 O 0.1 Cl 0.875 Br 0.375 The above-mentioned sulfide solid electrolytes exhibit higher ionic conductivity, air stability, and good structural stability.

[0039] In one embodiment of this application, the cell parameters of the sulfide solid electrolyte satisfy: a=b=c=9.85~10 Å. Since the cell parameters of the sulfide solid electrolyte of this application are within the above range, the lattice structure of the material itself can be well maintained, resulting in high ionic conductivity of the sulfide solid electrolyte.

[0040] In one embodiment of this application, the particle size of the sulfide solid electrolyte satisfies the following conditions: 0.5µm < D50 < 4µm, 7µm < D90 < 10µm. The particle size of the sulfide solid electrolyte in this application falls within the above range, resulting in good processability.

[0041] 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 >6 mS / cm; more preferably, the ionic conductivity of the sulfide solid electrolyte is >7 mS / cm; and even more preferably, the ionic conductivity of the sulfide solid electrolyte is >8 mS / cm. The sulfide solid electrolyte of this application, while improving structural stability and air stability, also possesses high ionic conductivity, and its application in all-solid-state lithium batteries can improve the electrochemical performance of all-solid-state lithium batteries.

[0042] 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.

[0043] 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 rare earth oxides (e.g., CeO₂, PrO₂, Sm₂O₃, Eu₂O₃), and the solvents can be n-hexane, benzene, toluene, cyclohexane, n-pentane, cyclopentane, and dimethyl carbonate. Because the rare earth element M in this application substitutes for the monovalent... 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 rare earth oxides can guide rare earth element M to preferentially enter the lithium site without damaging it. Frame unit.

[0044] 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 tube furnace programmed heating method is used, first heating at 150 to 300℃ for 2 to 4 hours, and then heating at 500 to 600℃ for 4 to 6 hours for sintering.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The sulfide solid electrolyte of this application has good structural stability, high ionic conductivity and good air stability, and thus the all-solid-state lithium battery including the sulfide solid electrolyte of this application has excellent electrochemical performance.

[0049] Example

[0050] 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.

[0051] Test methods and equipment:

[0052] Ion conductivity test

[0053] 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.

[0054] 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.

[0055] Electrochemical impedance spectroscopy (EIS) was performed at 25°C. The impedance was measured using a 1V DC polarization voltage applied to an electrochemical workstation (ChenHua, CHI630E) 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:

[0056]

[0057] Where σ is the ionic conductivity, with units of S cm. –1L 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 .

[0058] Air stability test

[0059] Air stability is primarily described by the retention rate of the ionic conductivity of sulfide solid electrolytes when exposed to air.

[0060] 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%.

[0061] X-ray powder diffraction test

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Particle size distribution testing

[0068] 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.

[0069] Electrochemical performance testing

[0070] Electrochemical performance testing mainly involves assembling a solid-state battery with a sulfide solid electrolyte and a layered high-nickel NCM811 ternary cathode material.

[0071] 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 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 the pressure is increased 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 the pressure is increased to 100Mpa and held for 1 minute to obtain a positive electrode; then 100mg of composite positive electrode powder is added to the other side. µm lithium indium alloy anode material was used for mold assembly after a slight pressure of 50 MPa to obtain an assembled all-solid-state lithium-ion battery. After verifying the airtightness, the battery was taken out of the glove box and transferred to the battery testing system for electrochemical charge-discharge cycle testing.

[0072] Charge and discharge test: The charge and discharge performance of the battery is tested using the LAND battery testing system under a constant temperature of 25°C.

[0073] Constant current charge-discharge testing directly reflects the electrochemical performance of active materials in a battery and is an important means of evaluating the practical application potential of these 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, the battery is discharged to 2.6V using the same current. 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 of the all-solid-state lithium-ion battery when the discharge capacity drops sharply (in this application, a sudden and drastic drop in discharge capacity refers to a sudden and rapid decrease in discharge capacity) are recorded.

[0074] 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 evaluate 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.

[0075] Capacity retention rate after 200 cycles = (200th discharge capacity / first discharge capacity) × 100%.

[0076] Example 1

[0077] In an Ar atmosphere, raw materials of Li₂S, P₂S₅, LiCl, LiBr, and rare earth oxide CeO₂ in a molar ratio of 2.15:0.5:0.875:0.375:0.05 were weighed. 1 kg of the raw material was added to 1 kg of n-hexane and mixed to obtain a suspension. The suspension was dried by 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). 5.55 PCe 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 Its X-ray diffraction pattern is as follows: Figure 1 As shown.

[0078] Examples 2 to 8

[0079] 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.

[0080] Example 9

[0081] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, P₂O₅, S elemental and rare earth oxide Eu₂O₃ raw materials in a molar ratio of 2.15:0.495:0.875:0.375:0.005:0.025:0.025", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr, P₂O₅, S elemental and rare earth oxide Eu₂O₃) is obtained. 5.55 PEu 0.05 S 4.65 O 0.1 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.

[0082] Example 10

[0083] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr and rare earth oxide PrO₂ in a molar ratio of 2.15:0.5:0.875:0.375:0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr and rare earth oxide PrO₂) was obtained. 5.55 PPr 0.05 S 4.65 O 0.1 Cl 0.875 Br0.375 Except for the step described in Example 1, the remaining steps are the same. Its X-ray diffraction pattern is as follows: Figure 3 As shown.

[0084] Example 11

[0085] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, P₂O₅, elemental S and rare earth oxide Sm₂O₃ in a molar ratio of 2.15:0.495:0.875:0.375:0.005:0.025:0.025", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr, P₂O₅, elemental S and rare earth oxide Sm₂O₃) is obtained. 5.55 PSm 0.05 S 4.65 O 0.1 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 4 As shown.

[0086] Example 12

[0087] By replacing the raw materials with "Li₂S, P₂S₅, LiBr, LiI and rare earth oxide CeO₂ in a molar ratio of 2.15:0.5:0.875:0.375:0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiBr, LiI and rare earth oxide CeO₂) was obtained. 5.55 PCe 0.05 S 4.65 O 0.1 Br 0.875 I 0.375 Except for the steps in Example 1, the remaining steps are the same.

[0088] Example 13

[0089] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiI and rare earth oxide CeO₂ in a molar ratio of 2.15:0.5:0.875:0.375:0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiI and rare earth oxide CeO₂) was obtained. 5.55 PCe 0.05 S 4.65 O 0.1 Cl 0.875 I 0.375 Except for the steps in Example 1, the remaining steps are the same.

[0090] Example 14

[0091] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, LiI and rare earth oxide CeO₂ in a molar ratio of 2.15:0.5:0.875:0.25:0.125:0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr, LiI and rare earth oxide CeO₂) was obtained. 5.55 PCe0.05 S 4.65 O 0.1 Cl 0.875 Br 0.25 I 0.125 Except for the steps in Example 1, the remaining steps are the same.

[0092] Example 15

[0093] By replacing the raw materials with "Li₂S, P₂S₅, LiCl and rare earth oxide CeO₂ in a molar ratio of 2.15:0.5:1.25:0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl and rare earth oxide CeO₂) was obtained. 5.55 PCe 0.05 S 4.65 O 0.1 Cl 1.25 Except for the steps in Example 1, the remaining steps are the same.

[0094] Example 16

[0095] Replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, rare earth oxides CeO₂, P₂O₅, elemental S and rare earth oxide Eu₂O₃ in a molar ratio of 2.15:0.4975:0.875:0.375:0.025:0.0025:0.0125:0.0125" yields a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr, rare earth oxides CeO₂, P₂O₅, elemental S and rare earth oxide Eu₂O₃) 5.55 PCe 0.025 Eu 0.025 S 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] Example 17

[0097] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr and rare earth oxide CeO₂ in a molar ratio of 2.15:0.5:0.625:0.625:0.05", a sulfide solid electrolyte (Li₂S, P₂S₅, LiCl, LiBr and rare earth oxide CeO₂) was obtained. 5.55 PCe 0.05 S 4.65 O 0.1 Cl 0.625 Br 0.625 Except for the steps in Example 1, the remaining steps are the same.

[0098] Example 18

[0099] 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 Mn0.54 O2, the negative electrode material is graphite, and the remaining electrochemical performance testing steps are the same as the above testing methods.

[0100] Example 19

[0101] 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.

[0102] Comparative Examples 1 to 4

[0103] 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.

[0104] Comparative Example 5

[0105] 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 step described in Example 1, the remaining steps are the same. Its X-ray diffraction pattern is as follows: Figure 5 As shown.

[0106] Comparative Example 6

[0107] By replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr, and CeS₂ in a molar ratio of 2.25: 0.5: 0.875: 0.375: 0.05", a sulfide solid electrolyte (Li₂S₅) is obtained. 5.75 PCe 0.05 S 4.75 Cl 0.875 Br 0.375 Except for the steps in Example 1, the remaining steps are the same.

[0108] Comparative Example 7

[0109] Besides adjusting the molar ratio of the raw materials, a sulfide solid electrolyte (Li) is obtained. 5.71 PCe 0.01 S 4.75 Cl 0.875 Br 0.375 Except for ), the remaining steps are the same as those in Comparative Example 6.

[0110] Comparative Example 8

[0111] 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.

[0112] Comparative Example 9

[0113] 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 8.

[0114] Comparative Example 10

[0115] In addition to replacing the raw materials with "Li₂S, P₂S₅, LiCl, LiBr and ZnO in a molar ratio of 1.85:0.5:1.4:0.2:0.05", a sulfide solid electrolyte Li₂S₅ was obtained. 5.3 Zn 0.05 PS 4.35 O 0.05 Cl 1.4 Br 0.2 Except for the steps, the rest are the same as in Example 1.

[0116] The preparation parameters and performance parameters of the sulfide solid electrolytes of each embodiment and comparative example are shown in Table 1, and the performance parameters of the all-solid-state batteries obtained therefrom are shown in Tables 2 and 3.

[0117] Table 1. Preparation and performance parameters of sulfide solid electrolytes

[0118]

[0119] In Table 1, " / " indicates that there are no relevant parameters.

[0120] Table 2 Performance parameters of all-solid-state batteries

[0121]

[0122] Table 3 Performance parameters of all-solid-state batteries of different systems

[0123]

[0124] 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<4µm, 7µm<D90<10µm; the sulfide solid electrolyte has high ionic conductivity and good air stability, with an ionic conductivity >5 mS / cm, a conductivity retention rate ≥85% after 12 hours of exposure at a dew point temperature of -40℃, a conductivity retention rate ≥79% after 24 hours of exposure at a dew point temperature of -40℃, a conductivity retention rate ≥70% after 48 hours of exposure at a dew point temperature of -40℃, and a ratio of impurity peak to main peak ≤0.17% after 24 hours of exposure at a dew point temperature of -40℃. As shown in Table 2, the sulfide solid electrolyte of this application, when used in 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 ≥80.5%, capacity retention after 200 cycles at 0.2C is ≥95.0%, the number of cycles at 0.2C is ≥329, and the cutoff voltage is ≥4.2V. As shown in Table 3, the sulfide solid electrolyte of this application, when used in different all-solid-state lithium battery systems, results in all-solid-state lithium batteries with high initial discharge efficiency, good cycle performance, and high cutoff voltage. In summary, the sulfide solid electrolyte of this application improves the structural stability of the sulfide electrolyte under complex electrochemical environments, while also improving its air stability and ionic conductivity, thereby enhancing the initial efficiency, cycle life, and operating voltage of all-solid-state lithium batteries. In other words, the sulfide solid electrolyte of this application can improve the electrochemical performance of all-solid-state lithium batteries.

[0125] 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 7-4x-y PM x S 6-2x-y O 2x X y M is at least one of the variable-valence rare earth elements Ce, Eu, Pr and Sm, X is at least one of the halogens, 0.005≤x≤0.3, 0.5≤y≤2, and the molar ratio of M to O is 1:

2.

2. The sulfide solid electrolyte according to claim 1, wherein, 0.02≤x≤0.15, 1.25≤y≤1.

75.

3. The sulfide solid electrolyte according to claim 1, wherein, X is at least one of Cl, Br, and I.

4. The sulfide solid electrolyte according to claim 1, wherein, The chemical formula of the sulfide solid electrolyte is Li 7-4x-y PM x S 6-2x-y O 2x X' 0.7y X'' 0.3y X' or X'' is independently Cl, Br or I, and X' is different from X'', with X' having a smaller ionic radius than X''.

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

6. The sulfide solid electrolyte according to claim 1, wherein, The sulfide solid electrolyte is Li 5.55 PCe 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.67 PCe 0.02 S 4.71 O 0.04 Cl 0.875 Br 0.375 Li 5.05 PCe 0.05 S 4.15 O 0.1 Cl 1.225 Br 0.525 Li 5.55 PEu 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.55 PPr 0.05 S 4.65 O 0.1 Cl 0.875 Br 0.375 Li 5.55 PSm 0.0 5S 4.65 O 0.1 Cl 0.875 Br 0.375 .

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 < 4µm, 7µm < D90 < 10µm.

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.

Images