Sulfide solid electrolyte and preparation method and application thereof

Abstract

The invention provides a sulfide solid electrolyte as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing raw materials, an organic amine dissolution promoter and a solvent in an inert atmosphere, and drying to obtain a precursor; and performing three-stage heat treatment on the precursor in an inert atmosphere to obtain the sulfide solid electrolyte. According to the invention, the organic amine is introduced as a dissolution promoter to induce two main raw materials of the sulfide solid electrolyte, namely lithium sulfide and phosphorus pentasulfide, to be completely dissolved in the solvent, so that the reaction is complete, and the sulfide solid electrolyte can be synthesized through a simple one-step wet reaction; moreover, the three-stage heat treatment can reduce energy consumption while simplifying the preparation process of the solid electrolyte and remarkably improve the purity and electrochemical performance of the product, is a preparation method of the sulfide solid electrolyte, which is high in discharge rate and suitable for large-scale production, and can remarkably improve the ionic conductivity of the sulfide solid electrolyte and reduce the production cost of the sulfide solid electrolyte. And the cycle performance of the battery using the electrolyte is improved.

Description

Technical Field

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

[0002] Secondary batteries are crucial for energy conversion and storage. With global industrialization and the widespread application of computers, higher demands are being placed on batteries. All-solid-state batteries utilize non-flammable, high-temperature resistant, non-corrosive, and non-volatile solid electrolytes (such as sulfide solid electrolytes) as lithium-ion transport channels, solving problems like electrolyte leakage and thermal runaway in traditional lithium-ion batteries and avoiding safety hazards. Furthermore, since no electrolyte is needed and lithium metal can be used as the negative electrode, the battery's weight is effectively reduced. Therefore, solid-state batteries possess extremely high potential energy density and are gradually becoming a potential alternative to traditional lithium-ion batteries as an important component of next-generation energy storage technology. Compared to liquid lithium-ion batteries, all-solid-state batteries not only have significant advantages in energy density but also exhibit higher performance potential in safety, cycle life, and operating temperature range. However, currently, solid-state batteries are mainly limited by the extreme difficulty of industrializing solid electrolytes, and large-scale mass production remains a considerable distance away.

[0003] Currently, the preparation of sulfide solid electrolytes mainly relies on the traditional solid-phase method. Although it can yield pure materials, this method suffers from drawbacks such as high energy consumption, long processing time, high cost, and difficulty in large-scale production. In contrast, the liquid-phase method has attracted widespread attention from researchers due to its simple, rapid process and ease of large-scale production. The liquid-phase method uses organic solvents as a medium to synthesize sulfide solid electrolytes with smaller particles. The process is simple and time-saving, making it more suitable for large-scale production. However, it is limited by the limited solubility of the two main raw materials, lithium sulfide (Li₂S) and phosphorus pentasulfide (P₂S₅), in organic solvents. Currently, sulfide solid electrolytes obtained by the liquid-phase method are impure, have low ionic conductivity, and involve complex steps. For example, Chinese patent application CN114455613B discloses a method for preparing sulfide electrolytes, sulfide electrolytes, and their applications, which requires six steps to obtain the precursor solution. This involves numerous steps, a complex process, and repeated drying, resulting in high energy consumption.

[0004] Although the liquid-phase method theoretically offers a more economical and efficient preparation route, in practice, it still faces technical obstacles such as low solubility of raw materials, complex synthesis steps, and high energy consumption and cost. These issues limit the performance improvement of sulfide solid electrolyte materials and the commercialization of all-solid-state batteries. There is an urgent need to develop new preparation methods to simplify processes, reduce costs, and simultaneously improve the purity and ionic conductivity of solid electrolytes. Summary of the Invention

[0005] The main objective of this invention is to provide a sulfide solid electrolyte, its preparation method, and its application, in order to solve the problems of complex preparation processes, low ionic conductivity of products, poor cycle stability, and unsuitability for large-scale production of sulfide solid electrolytes in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a sulfide solid electrolyte is provided, comprising the following steps: Step S1, mixing raw materials, an organic amine co-solvent, and a solvent under an inert atmosphere, and drying to obtain a precursor; the raw materials include Li2S raw materials, P2S5 raw materials, and optional doped raw materials; Step S2, subjecting the precursor to a three-stage heat treatment under an inert atmosphere to obtain a sulfide solid electrolyte; the three-stage heat treatment includes a first-stage heat treatment, a second-stage heat treatment, and a cooling stage performed sequentially; the first-stage heat treatment includes: heating to 100-250°C at a rate of 1-10°C / min and holding at that temperature for 0.5-24 h; the second-stage heat treatment includes: heating to 120-800°C at a rate of 5-15°C / min and holding at that temperature for 2-6 h.

[0007] By applying the technical solution of this invention, an organic amine is introduced as a co-solvent to induce the complete dissolution of the two main raw materials of sulfide solid electrolyte, namely lithium sulfide and phosphorus pentasulfide, in the solvent, thereby ensuring complete reaction. The sulfide solid electrolyte can be synthesized through a simple one-step wet reaction. Furthermore, the three-stage heat treatment simplifies the preparation process of solid electrolytes while reducing energy consumption and significantly improving the purity and electrochemical performance of the product. This helps ensure the controllability and repeatability of the entire preparation process, effectively solving the problems of unstable product quality and unsuitability for large-scale production in traditional methods. The preparation method of this invention is simple, low-cost, and produces high phase purity. It is a high-yield method suitable for large-scale production of sulfide solid electrolytes, significantly improving the ionic conductivity of sulfide solid electrolytes, and significantly enhancing the cycle performance of batteries using this electrolyte.

[0008] Furthermore, the organic amine co-solvent is selected from one or more of triethylamine, butylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, dodecylamine, pyridine, and N,N-dimethylaniline; and / or the amount of organic amine co-solvent added accounts for 1-5% of the weight of the raw material. The organic amine selected in this invention can effectively destroy the crystal structure of Li2S and P2S5 by virtue of its strong coordination and acid-base adjustment capabilities, transforming them into molecular-level homogeneous soluble complex intermediates.

[0009] Furthermore, the doping raw materials include one or more of GeS2, SiS2, SnS2, Sb2S3, LiCl, LiBr, LiI, Li2O, Se, and S; and / or the solvent includes one or more of tetrahydrofuran, acetonitrile, ethyl acetate, N-methylpyrrolidone, dimethyl sulfoxide, and methyl ethyl ketone; and / or the amount of solvent added accounts for 1-50% of the weight of the raw materials. The above-mentioned doping raw materials can introduce additional ionic and electronic conduction pathways, enhancing the electrochemical performance and thermal stability of the material. The introduction of specific types of auxiliary solvents can further enhance the solubility of the entire system, providing better rheological properties and laying the foundation for obtaining defect-free dense electrolytes.

[0010] Further, in step S1, the inert atmosphere includes one or more of argon, nitrogen, and helium; and / or the mixing method includes one or more of stirring mixing, shear mixing, ball milling mixing, twin-screw extrusion mixing, and degassing mixing; and / or the mixing time is 8–24 h; and / or the drying method includes one or more of vacuum drying, vacuum filtration, hot air drying, and spray drying. The above mixing conditions are beneficial for promoting uniform dispersion of raw materials and ensuring the full progress of the chemical reaction, further reducing phase impurities caused by insufficient local reaction. Optimization of drying conditions helps to thoroughly remove solvents and volatile impurities, obtaining a denser and more uniform sulfide solid electrolyte structure.

[0011] Furthermore, in step S2, the cooling stage includes: cooling to 20–30°C in the furnace, or cooling to 20–30°C at a rate of 1–5°C / min. These conditions help reduce material defects and crystal structure damage caused by thermal stress, thereby improving the integrity and performance consistency of the material.

[0012] Furthermore, the temperature of the first-stage heat treatment is lower than that of the second-stage heat treatment, with a difference of 80–460 °C. This progressive heat treatment process is more conducive to simplifying the preparation process, improving the controllability of the reaction, reducing energy consumption, and facilitating the large-scale production of sulfide solid electrolytes.

[0013] Furthermore, the time for the first stage heat treatment is greater than or equal to the time for the second stage heat treatment, with a difference of 0–8 hours. The aforementioned temperature and time differences conform to the thermodynamic laws governing the synthesis of sulfide solid electrolyte materials, contributing to the formation of a uniform, high-purity solid electrolyte phase, thereby significantly improving its ionic conductivity.

[0014] According to another aspect of the present invention, a sulfide solid electrolyte is provided, which is obtained by the preparation method described above, and has excellent electrochemical performance and chemical stability, and can meet the high requirements of solid-state batteries for electrolyte materials.

[0015] Furthermore, the chemical formula of the sulfide solid electrolyte is (100-xy)Li₂S·xP₂S₅·yM m N n Wherein, 0 < x < 100, 0 ≤ y < 100, 0 < x + y < 100, 0 ≤ m < 4, 0 ≤ n < 6, M is selected from one or more of Li, Ge, Si, Sn, and Sb, and N is selected from one or more of Se, O, Cl, Br, and I. These elements can adjust the ionic conductivity and electrochemical stability of the material, achieving superior electrochemical performance.

[0016] According to another aspect of the present invention, a solid-state battery is provided, comprising the sulfide solid electrolyte described above, which has ultra-high energy density and excellent cycle performance. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] As described in the background section of this invention, existing technologies suffer from complex preparation processes, low ionic conductivity of the products, and poor cycle stability, making them unsuitable for large-scale production. To address these issues, in a typical embodiment of this invention, a method for preparing a sulfide solid electrolyte is provided, comprising the following steps: Step S1, mixing raw materials, an organic amine co-solvent, and a solvent under an inert atmosphere, followed by drying to obtain a precursor; the raw materials include Li2S raw materials, P2S5 raw materials, and optional doping raw materials; Step S2, subjecting the precursor to a three-stage heat treatment under an inert atmosphere to obtain a sulfide solid electrolyte; the three-stage heat treatment includes a first-stage heat treatment, a second-stage heat treatment, and a cooling stage performed sequentially; the first-stage heat treatment includes heating to 100–250°C at a rate of 1–10°C / min and holding at that temperature for 0.5–24 h; the second-stage heat treatment includes heating to 120–800°C at a rate of 5–15°C / min and holding at that temperature for 2–6 h.

[0019] In this invention, Li2S raw material, P2S5 raw material, optional doping raw material, organic amine co-solvent, and solvent are first mixed under an inert atmosphere. During this process, organic amine is introduced as a co-solvent, and its coordination ability, acid-base regulation ability and solvation effect are utilized to induce the two main raw materials of sulfide solid electrolyte, namely lithium sulfide and phosphorus pentasulfide, to completely dissolve in the solvent. Subsequently, the solvent and excess organic amine are further removed by drying and heat treatment to obtain the precursor.

[0020] Specifically, organic amine molecules (such as ethylenediamine, diethylenetriamine, etc.) all contain nitrogen atoms with lone pairs of electrons, and Li in Li₂S +It has a strong electron-deficient property and will form a Lewis acid-base coordination with the lone pair electrons on the nitrogen atom of the amine group to form soluble [Li(amine)]. n The ion complex cation effectively disrupts the ionic lattice of Li₂S, thus reducing the concentration of Li₂S in the ion crystal. + "Pull" into the solution, S 2- It is also released. Furthermore, P2S5 in solution hydrolyzes or reacts with sulfide ions to form acidic intermediates such as thiophosphoric acid (H3PS4). These acidic protons (H... + If not neutralized in time, it will react with S. 2- The combination generates gaseous H2S, which escapes, leading to sulfur loss and stoichiometry imbalance, and causing neutral thiophosphate ions to precipitate due to their low solubility. Organic amines, as organic bases, can rapidly capture these protons, forming stable ammonium salts (R-NH3). + This maintains the reaction system in a stable alkaline environment, which not only inhibits the formation of H2S but also ensures that the thiophosphate ion exists as a soluble thiophosphate anion (such as [PS4]). 3- It exists in the form of )

[0021] The various ions generated in the above process, including [Li (amine)] n [+] cationic complex and [PS4] 3- Anions such as Li₂S and P₂S₅ are strongly solvated by organic amine molecules through polar interactions and spatial encirclement, thereby greatly improving the kinetic stability of these ions and preventing them from colliding and combining to form insoluble intermediate precipitates such as Li₃PS₄ (alumina-germanium sulfide) or thio-LiSiCON (a solid electrolyte). In summary, organic amines disrupt the reactant structure through coordination, maintain the reaction environment by neutralizing acidic byproducts, and stabilize the dissolved products through solvation. These three actions work synergistically to successfully dissolve Li₂S and P₂S₅ completely, transforming them into a homogeneous liquid reaction system at the molecular / ionic level.

[0022] After obtaining the precursor, it is heat-treated under an inert atmosphere. In the first stage, a low-temperature, long-duration heat treatment is performed with a gentle rate of increase to gradually remove residual solvents and volatile impurities, stabilize the material structure, and reduce internal stress and cracks caused by rapid heating. In the second stage, the temperature is rapidly increased to the target temperature for a short-duration high-temperature heat treatment to promote the crystallization of the sulfide solid electrolyte, optimize the lattice arrangement, and improve the connectivity of ion migration pathways, thereby significantly increasing ionic conductivity. Finally, the material is cooled to room temperature to reduce material defects caused by thermal stress and improve the integrity and performance consistency of the material. These heat treatment conditions simplify the preparation process of the solid electrolyte, reduce energy consumption, and significantly improve the purity and electrochemical performance of the product, making large-scale production possible. The stepwise heat treatment process also helps ensure the controllability and repeatability of the entire preparation process, effectively solving the problems of unstable product quality and unsuitability for large-scale production in traditional methods.

[0023] In particular, this invention introduces a single organic amine as a co-solvent followed by stepwise heat treatment. Compared to the conventionally used ethylenediamine-ethylenedithiol (EDA-EDT solvent), this method resolves the contradiction between high organic residues and low ionic conductivity in solution methods. Organic amines can assist in the complete dissolution of Li₂S and P₂S₅; however, the strong coordination between organic amines and lithium ions makes them difficult to remove. If only a single heat treatment is performed, the violent and rapid liquid-phase removal process can lead to the pyrolysis and carbonization of residual amine molecules, forming electronic conductive pathways and reducing the electrochemical stability of the electrolyte. Furthermore, rapid liquid-phase evaporation can cause numerous cracks and pores in the film layer, compromising the structural density. Therefore, this invention employs a specific stepwise heat treatment procedure to thoroughly purify organic residues while better controlling the crystallization process. Ultimately, this reduces material costs and allows for the synthesis of sulfide solid electrolytes through a simple one-step wet reaction.

[0024] The preparation method of this invention is simple and low in cost. It significantly improves the purity of the phase through the dissolution and coordination of organic amines and the gradient purification of stepwise heat treatment. It is a method for preparing sulfide solid electrolyte with high yield and suitable for large-scale production. It can significantly improve the ionic conductivity of sulfide solid electrolyte, and the cycle performance of the battery is also significantly improved when this electrolyte is used.

[0025] Considering the thermodynamics and crystal growth mechanism in the synthesis of sulfide solid electrolytes, for similar reasons, it is further preferred that the temperature of the first stage heat treatment is 100-200℃ and the time is 5-12h; and / or the temperature of the second stage heat treatment is 180-600℃ and the time is 3-6h.

[0026] In a preferred embodiment, the organic amine co-solvent is selected from one or more of triethylamine, butylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, dodecylamine, pyridine, and N,N-dimethylaniline; and / or the amount of organic amine co-solvent added accounts for 1-5% of the weight of the raw material, preferably 1-3%. The above-mentioned organic amine co-solvents have more suitable nucleophilic and basic characteristics, which can further enhance the solubility of Li₂S and P₂S₅ in non-aqueous solvents, forming a more stable solvated complex. This facilitates the simplification of preparation steps while promoting sufficient contact and reaction of the reactants, thereby obtaining a sulfide solid electrolyte with higher purity and more uniform structure, and significantly improving ionic conductivity. An appropriate amount of organic amine helps to accelerate the reaction process while playing a co-solvent role, reducing energy consumption, and controlling costs and residues, thus improving the economy and practicality of the preparation method and making it more suitable for large-scale industrial production.

[0027] To further improve the ionic conductivity of sulfide solid electrolytes, in a preferred embodiment, the doping material includes one or more of GeS2, SiS2, SnS2, Sb2S3, LiCl, LiBr, LiI, Li2O, Se, and S; and / or the solvent is an anhydrous organic solvent, preferably including one or more of tetrahydrofuran, acetonitrile, ethyl acetate, N-methylpyrrolidone, dimethyl sulfoxide, and methyl ethyl ketone; and / or the amount of solvent added accounts for 1-50% of the weight of the raw material, preferably 10-50%. The amount of doping material added can be adjusted according to the composition of the target electrolyte. The above-mentioned doping materials can enhance the electrochemical performance and thermal stability of the material by adjusting the chemical composition of the electrolyte and introducing additional ionic and electronic conduction pathways. The above-mentioned organic solvents have higher solubility and lower water content, which can further promote the uniform dispersion and efficient reaction of the raw materials, reduce hydrolysis side reactions, and improve the purity of the product. A suitable solvent can form a solution with better fluidity, which is conducive to the formation of a homogeneous mixture, further refines the product grains, and improves the conductivity.

[0028] The organic amine selected in this invention can effectively disrupt the crystal structure of Li₂S and P₂S₅ by virtue of its strong coordination and acid-base regulation capabilities, transforming them into molecular-level homogeneous soluble complex intermediates. Furthermore, the introduction of specific types of auxiliary solvents can further enhance the solubility of the entire system, providing better rheological properties and laying the foundation for obtaining a defect-free, dense electrolyte.

[0029] An inert atmosphere creates an oxygen-free and water-free environment, preventing oxidation or hydrolysis of sulfide raw materials during preparation. To further improve the purity and stability of the product, in a preferred embodiment, in step S1, the inert atmosphere includes one or more of argon, nitrogen, and helium; and / or the mixing method includes one or more of stirring, shearing, ball milling, twin-screw extrusion, and degassing; and / or the mixing time is 8–24 h; and / or the drying method includes one or more of vacuum drying, vacuum filtration, hot air drying, and spray drying; preferably, drying includes vacuum drying at 60–180 °C for 6–8 h. The above mixing conditions facilitate uniform dispersion of the raw materials and complete chemical reactions, further reducing impurities caused by insufficient local reactions. Optimization of drying conditions helps to thoroughly remove solvents and volatile impurities, reduce the impact of thermal stress, and obtain a denser and more uniform sulfide solid electrolyte structure, thereby further improving its ionic conductivity.

[0030] In a preferred embodiment, step S2 includes cooling in the furnace to 20–30°C, or cooling to 20–30°C at a rate of 1–5°C / min. After low-temperature long-time heat treatment and high-temperature short-time heat treatment, slow cooling in the furnace or controlled cooling rate allows the material to slowly drop to room temperature, which helps reduce material defects and crystal structure damage caused by thermal stress, and improves the integrity and performance consistency of the material.

[0031] To further progressively optimize the material structure and achieve the transition from impurity removal to perfect crystallization, in a preferred embodiment, the temperature of the first-stage heat treatment is < the temperature of the second-stage heat treatment, with a difference of 80–460°C; and / or the time of the first-stage heat treatment is ≥ the time of the second-stage heat treatment, with a difference of 0–8 hours. Longer treatment at lower temperatures gently removes residual solvents and reduces structural defects caused by abrupt material changes; the subsequent short-term high-temperature treatment accelerates the crystallization of the sulfide solid electrolyte, improves lattice quality, and increases ionic conductivity pathways. The aforementioned temperature and time differences conform to the thermodynamic laws of sulfide solid electrolyte material synthesis, contributing to the formation of a uniform, high-purity solid electrolyte phase, thereby significantly improving its ionic conductivity. Simultaneously, the progressive heat treatment process simplifies the preparation process, improves reaction controllability, reduces energy consumption, and facilitates the large-scale production of sulfide solid electrolytes.

[0032] In another typical embodiment of the present invention, a sulfide solid electrolyte is also provided, obtained using the preparation method described above. Through optimized preparation processes, the sulfide solid electrolyte material of the present invention exhibits excellent electrochemical performance and chemical stability, meeting the high requirements of solid-state batteries for electrolyte materials. It also significantly improves the energy density and cycle performance of solid-state batteries, achieving safer and more efficient energy storage and conversion.

[0033] In a preferred embodiment, the chemical formula of the sulfide solid electrolyte is (100-xy)Li₂S·xP₂S₅·yM. m N n Wherein, 0 < x < 100, 0 ≤ y < 100, 0 < x + y < 100, 0 ≤ m < 4, 0 ≤ n < 6, M is selected from one or more of Li, Ge, Si, Sn, and Sb, and N is selected from one or more of Se, O, Cl, Br, and I. By adjusting the values ​​of x, y, m, and n, or by changing the elemental types of M and N, sulfide solid electrolytes with different properties can be flexibly prepared. By doping with M and N elements, the ionic conductivity and electrochemical stability of the material can be adjusted to achieve better electrochemical performance, thereby effectively improving the performance and safety of solid-state batteries and meeting the needs of different battery applications.

[0034] For similar reasons, the sulfide solid electrolyte further preferably includes Li6PS5Cl, Li 10 GeP2S 12 Li7P2S8I, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li7P2S8I 0.5 Br 0.5 Li 10 SnP2S 12 Li3PSbS3Cl, Li6PS 4.5 Se 0.3 O 0.2 One or more of Cl.

[0035] In another typical embodiment of the present invention, a solid-state battery is also provided, comprising the sulfide solid electrolyte described above. By using the sulfide solid electrolyte as a lithium-ion transport channel, the resulting solid-state battery can solve the problems of electrolyte leakage and thermal runaway in traditional lithium-ion batteries, improve battery safety and stability, and has ultra-high energy density (based on the sulfide solid electrolyte) and excellent cycle performance (based on the preparation method of the present invention). It is a high-power and high-energy-density solid-state battery that can meet the needs of different application scenarios.

[0036] Typical, but not limiting, amounts of organic amine co-solvents added are 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any two of these values, based on the weight of the raw material.

[0037] Typical, but not limiting, first-stage heat treatment includes: heating at a rate of 1℃ / min, 2℃ / min, 5℃ / min, 8℃ / min, 10℃ / min or any two of these values ​​to 100℃, 120℃, 150℃, 180℃, 200℃, 220℃, 250℃ or any two of these values, and holding at this temperature for 0.5h, 1h, 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h or any two of these values.

[0038] Typical, but not limiting, second-stage heat treatment includes: heating at a rate of 5℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 15℃ / min or any two of these values ​​to 120℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃ or any two of these values, and holding at this temperature for 2h, 3h, 4h, 5h, 6h or any two of these values.

[0039] Typically, but not limitingly, the temperature of the first stage heat treatment is less than the temperature of the second stage heat treatment, with the difference being a range of 80℃, 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 460℃, or any two of these values.

[0040] Typically, but not limitingly, the time of the first stage heat treatment is greater than or equal to the time of the second stage heat treatment, with the difference being a range of 0h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, or any two of these values.

[0041] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0042] Example 1

[0043] Step S1: Mix Li2S:P2S5:LiCl in a molar ratio of 5:1:2, add triethylamine (1% of the total weight of the raw materials) as a co-solvent and tetrahydrofuran (50% of the total weight of the raw materials) as a solvent, and ball mill the mixture for 12 h under argon protection; then vacuum dry the mixture at 60 °C for 6 h to obtain the precursor.

[0044] In step S2, the precursor is first heated to 150°C at 5°C / min and held for 12 hours in argon atmosphere, then heated to 450°C at 5°C / min and held for 4 hours, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li6PS5Cl.

[0045] Example 2

[0046] Step S1: Mix Li2S:P2S5:GeS2 in a molar ratio of 5:1:1, add 2% of the total weight of the raw materials with butylamine as a co-solvent and 20% of the total weight of the raw materials with acetonitrile as a solvent, and stir and mix under argon protection for 8 hours; dry the mixture at 100°C with forced air for 6 hours to obtain the precursor.

[0047] In step S2, the precursor is first heated to 150℃ in argon at a rate of 5℃ / min and held for 12 hours, then heated to 480℃ at a rate of 10℃ / min and held for 5 hours. The mixture is then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li. 10 GeP2S 12 .

[0048] Example 3

[0049] Step S1: Mix Li2S:P2S5:LiI in a molar ratio of 3:1:1, add 2% ethylenediamine as a co-solvent and 30% ethyl acetate as a solvent, and mix by twin-screw extrusion for 24 h under argon protection; filter the mixture under reduced pressure for 1 h to obtain the precursor.

[0050] In step S2, the precursor is first heated to 100°C at 10°C / min and held for 8 hours in argon gas, then heated to 180°C at 15°C / min and held for 3 hours, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li7P2S8I.

[0051] Example 4

[0052] Step S1: Mix Li2S:SiS2:P2S5:LiCl in a molar ratio of 7.7:2.9:1.2:0.5, add diethylenetriamine (equivalent to 3% of the total weight of the raw materials) as a co-solvent and N-methylpyrrolidone (equivalent to 33% of the total weight of the raw materials) as a solvent, and shear and mix under argon protection for 12 h; dry the mixture under vacuum at 150 °C for 8 h to obtain the precursor.

[0053] In step S2, the precursor is first heated to 200℃ at 5℃ / min and held for 10h in argon atmosphere, then heated to 550℃ at 5℃ / min and held for 6h, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li. 9.54 Si 1.74 P 1.44 S11.7 Cl 0.3 .

[0054] Example 5

[0055] Step S1: Mix Li2S:P2S5:LiI:LiBr in a molar ratio of 3:1:0.5:0.5, add triethylenetetramine (3% of the total weight of raw materials) as a co-solvent and dimethyl sulfoxide (25% of the total weight of raw materials) as a solvent, and degas and mix for 10 h under argon protection; then vacuum dry the mixture at 180 °C for 8 h to obtain the precursor.

[0056] In step S2, the precursor is first heated to 200℃ at 5℃ / min and held for 10h in argon atmosphere, then heated to 600℃ at 10℃ / min and held for 5h, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li7P2S8I. 0.5 Br 0.5 .

[0057] Example 6

[0058] Step S1: Mix Li2S:SnS2:P2S5 in a molar ratio of 5:1:1, add dodecylamine (3% of the total weight of raw materials) as a co-solvent and methyl ethyl ketone (10% of the total weight of raw materials) as a solvent, and stir and mix under argon protection for 10 h; dry the mixture under vacuum at 80 °C for 8 h to obtain the precursor.

[0059] Step S2: The precursor is first heated to 100℃ in argon at 5℃ / min and held for 5h, then heated to 560℃ at 10℃ / min and held for 5h, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li. 10 SnP2S 12 .

[0060] Example 7

[0061] Step S1: Mix Li2S:P2S5:Sb2S3:LiCl:S in a molar ratio of 1:0.5:0.5:1:0.25, add pyridine (1% of the total weight of the raw materials) as a co-solvent and tetrahydrofuran (50% of the total weight of the raw materials) as a solvent, and ball mill the mixture for 12 h under argon protection; spray dry the mixture to obtain the precursor.

[0062] In step S2, the precursor is first heated to 150°C at 5°C / min and held for 12 hours in argon gas, then heated to 510°C at 10°C / min and held for 4 hours, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li3PSbS3Cl.

[0063] Example 8

[0064] Step S1: Mix Li2S:P2S5:LiCl:Se:Li2O in a molar ratio of 3:0.5:1:0.3:0.1, add N,N-dimethylaniline (1% of the total weight of raw materials) as a co-solvent and tetrahydrofuran (50% of the total weight of raw materials) as a solvent, and ball mill the mixture for 12 h under argon protection; then vacuum dry the mixture at 60 °C for 6 h to obtain the precursor.

[0065] In step S2, the precursor is first heated to 150℃ at 5℃ / min and held for 12h in argon atmosphere, then heated to 550℃ at 10℃ / min and held for 4h, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li6PS. 4.5 Se 0.3 O 0.2 Cl.

[0066] Example 9

[0067] The difference from Example 1 is that in step S1, Li2S:P2S5:LiCl is mixed in a molar ratio of 5:1:2, and triethylamine equivalent to 5% of the total weight of the raw materials is added as a co-solvent, and tetrahydrofuran equivalent to 1% of the total weight of the raw materials is added as a solvent. The mixture is ball-milled for 12 hours under argon protection. The mixture is then vacuum-dried at 60°C for 6 hours to obtain the precursor.

[0068] Example 10

[0069] The difference from Example 1 is that in step S2, the precursor is first heated to 100°C at 1°C / min and held for 24 hours in argon gas, then heated to 120°C at 5°C / min and held for 6 hours, and then cooled to room temperature at a rate of 1°C / min to obtain the sulfide solid electrolyte Li6PS5Cl.

[0070] Example 11

[0071] The difference from Example 1 is that in step S2, the precursor is first heated to 250°C at 10°C / min and held for 0.5h in argon gas, then heated to 800°C at 15°C / min and held for 2h, and then cooled to room temperature at a rate of 5°C / min to obtain the sulfide solid electrolyte Li6PS5Cl.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that no co-solvent was added in step S1.

[0074] Comparative Example 2

[0075] The difference from Example 2 is that no co-solvent was added in step S1.

[0076] Comparative Example 3

[0077] The difference from Example 3 is that no co-solvent was added in step S1.

[0078] Comparative Example 4

[0079] The difference from Example 4 is that no co-solvent was added in step S1.

[0080] Comparative Example 5

[0081] The difference from Example 5 is that no co-solvent was added in step S1.

[0082] Comparative Example 6

[0083] The difference from Example 6 is that no co-solvent was added in step S1.

[0084] Comparative Example 7

[0085] The difference from Example 7 is that no co-solvent was added in step S1.

[0086] Comparative Example 8

[0087] The difference from Example 8 is that no co-solvent was added in step S1.

[0088] Comparative Example 9

[0089] The difference from Example 1 is that ethylenediamine-ethylenedithiol (EDA-EDT) is used as a co-solvent in step S1; in step S2, the precursor is heated to 450°C in argon at 5°C / min and held for 12 hours, and then cooled to room temperature in the furnace.

[0090] Comparative Example 10

[0091] The difference from Example 1 is that in step S2, the precursor is heated to 150°C in argon at 5°C / min and held for 24 hours, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li6PS5Cl.

[0092] Comparative Example 11

[0093] The difference from Example 1 is that in step S2, the precursor is heated to 450°C in argon at 5°C / min and held for 8 hours, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li6PS5Cl.

[0094] Comparative Example 12

[0095] The difference from Example 1 is that in step S2, the precursor is first heated to 450°C at 2°C / min and held for 4 hours in argon gas, then cooled to 150°C at 5°C / min and held for 12 hours, and then cooled to room temperature in the furnace to obtain the sulfide solid electrolyte Li6PS5Cl.

[0096] Performance testing:

[0097] The electrolyte materials prepared in the above embodiments and comparative examples were subjected to ionic conductivity and electrochemical stability tests, and the results are shown in Table 1 and Table 2.

[0098] Ionic conductivity: Weigh 300 mg of the prepared sulfide solid electrolyte, cold-press it into a sheet, and use stainless steel as the blocking electrode for AC impedance testing. The Z′ value at the intersection of the straight line and the Z′ axis is taken as the total impedance R of the solid electrolyte, and the ionic conductivity is calculated accordingly. The total ionic conductivity is calculated using the conductivity calculation formula σ = L / (R*S), where L is the sample thickness, R is the total impedance, and S is the effective contact area between the sample and the electrode.

[0099] Electrochemical stability of lithium metal: A lithium-ion symmetric battery was assembled using lithium metal sheets as electrodes and a sulfide solid electrolyte as the solid electrolyte. Lithium dendrites are a core cause of short circuits, failures, and even fires in both liquid and solid-state batteries. Symmetric batteries allow for direct testing of whether lithium metal can uniformly deposit and dissolve during long-term cycling without forming dendrites that pierce the electrolyte. Therefore, they are used to investigate whether harmful side reactions occur at the interface between lithium metal and the electrolyte, further verifying the electrochemical stability of the electrolyte. The assembled lithium-ion symmetric battery was tested at 0.2 mA / cm². 2 The current density is 0.5 mAh / cm³. 2 Cyclic tests were conducted on the deposition capacity, recording the number of cycles in which reversible lithium deposition / dissolution cycles could be performed without battery failure. The more cycles, the better the electrochemical stability of the sulfide solid electrolyte.

[0100] Table 1

[0101]

[0102]

[0103] Table 2

[0104] / Ionic conductivity (mS / cm) Number of loops / revolutions Example 1 10 262 Example 9 7 189 Example 10 5.7 123 Example 11 6.3 166 Comparative Example 1 2.1 97 Comparative Example 9 4.8 106 Comparative Example 10 2.3 89 Comparative Example 11 5.5 112 Comparative Example 12 5.3 109

[0105] As can be seen, Comparative Examples 1 to 8, due to the absence of an organic amine co-solvent, resulted in low solubility of Li₂S and P₂S₅, incomplete reaction, and consequently, low ionic conductivity of the resulting solid electrolytes. Comparative Example 9, using ethylenediamine-ethylenedithiol as a composite co-solvent, suffered from incomplete removal of the electrolytes due to the use of EDA-EDT, which, while promoting dissolution, negatively impacted electrolyte performance, leading to a decrease in conductivity. Comparative Examples 10 to 12, failing to employ the three-stage heat treatment with specific temperature and time as described in this application, failed to obtain a dense and well-crystallized final product, resulting in poor electrical properties.

[0106] As can be seen from the above, compared with the comparative example, the embodiments of the present invention introduce organic amines as a co-solvent to induce the complete dissolution of the two main raw materials of the sulfide solid electrolyte, namely lithium sulfide and phosphorus pentasulfide, in the solvent, thereby ensuring the complete reaction. The sulfide solid electrolyte can be synthesized through a simple one-step wet reaction. Furthermore, the three-stage heat treatment simplifies the preparation process of the solid electrolyte while reducing energy consumption and significantly improving the purity and electrochemical performance of the product. This helps ensure the controllability and repeatability of the entire preparation process, effectively solving the problems of unstable product quality and unsuitability for large-scale production in traditional methods. The preparation method of the present invention is simple in steps, low in cost, and produces high phase purity. It is a high-yield method suitable for large-scale production of sulfide solid electrolytes, which can significantly improve the ionic conductivity of the sulfide solid electrolyte, and the cycle performance of the battery is also significantly improved when this electrolyte is used.

[0107] Furthermore, it can be seen that the overall effect is better when all process parameters are within the preferred range of the present invention.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a sulfide solid electrolyte, characterized in that, Includes the following steps: Step S1: The raw materials, organic amine co-solvent, and solvent are mixed under an inert atmosphere and dried to obtain the precursor; the raw materials include Li2S raw materials, P2S5 raw materials, and optional doping raw materials; Step S2: The precursor is subjected to a three-stage heat treatment under the inert atmosphere to obtain the sulfide solid electrolyte. The three-stage heat treatment includes a first-stage heat treatment, a second-stage heat treatment, and a cooling section performed sequentially. The first stage of heat treatment includes: heating to 100-250°C at a rate of 1-10°C / min and holding at that temperature for 0.5-24 hours; The second stage of heat treatment includes: heating to 120-800°C at a rate of 5-15°C / min and holding at that temperature for 2-6 hours.

2. The method for preparing sulfide solid electrolyte according to claim 1, characterized in that, The organic amine co-solvent is selected from one or more of triethylamine, butylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, dodecylamine, pyridine, and N,N-dimethylaniline; and / or The amount of the organic amine co-solvent added accounts for 1 to 5% of the weight of the raw material.

3. The method for preparing a sulfide solid electrolyte according to claim 1 or 2, characterized in that, The doping material includes one or more of GeS2, SiS2, SnS2, Sb2S3, LiCl, LiBr, LiI, Li2O, Se, and S; and / or The solvent includes one or more of tetrahydrofuran, acetonitrile, ethyl acetate, N-methylpyrrolidone, dimethyl sulfoxide, and methyl ethyl ketone; and / or The amount of solvent added is 1 to 50% of the weight of the raw material.

4. The method for preparing a sulfide solid electrolyte according to claim 1 or 2, characterized in that, In step S1 The inert atmosphere includes one or more of argon, nitrogen, and helium; and / or The mixing method includes one or more of stirring mixing, shear mixing, ball milling mixing, twin-screw extrusion mixing, and degassing mixing; and / or the mixing time is 8–24 hours; and / or The drying method includes one or more of vacuum drying, vacuum filtration, hot air drying, and spray drying.

5. The method for preparing a sulfide solid electrolyte according to claim 1 or 2, characterized in that, In step S2, the cooling section includes: cooling to 20-30°C with the furnace, or cooling to 20-30°C at a rate of 1-5°C / min.

6. The method for preparing a sulfide solid electrolyte according to claim 1 or 2, characterized in that, The temperature of the first stage heat treatment is less than the temperature of the second stage heat treatment, with a difference of 80 to 460°C.

7. The method for preparing a sulfide solid electrolyte according to claim 1 or 2, characterized in that, The time for the first stage of heat treatment is greater than or equal to the time for the second stage of heat treatment, with a difference of 0 to 8 hours.

8. A sulfide solid electrolyte, characterized in that, It is obtained using the preparation method according to any one of claims 1 to 7.

9. The sulfide solid electrolyte according to claim 8, characterized in that, The chemical formula of the sulfide solid electrolyte is (100-xy)Li₂S·xP₂S₅·yM m N n Where 0 < x < 100, 0 ≤ y < 100, 0 < x + y < 100, 0 ≤ m < 4, 0 ≤ n < 6, M is selected from one or more of Li, Ge, Si, Sn and Sb, and N is selected from one or more of Se, O, Cl, Br and I.

10. A solid-state battery, characterized in that, Includes the sulfide solid electrolyte as described in claim 8 or 9.

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