Sulfide solid electrolyte suitable for low temperature and preparation method thereof

Abstract

The invention discloses a sulfide solid electrolyte suitable for low temperature and a preparation method thereof. The method comprises the following steps: weighing raw materials according to a stoichiometric ratio, drying and grinding; carrying out ball milling treatment on the mixed material precursor; performing one-way pressing by using a tablet press to obtain a cold-pressed mixed precursor tablet; transferring the cold-pressed mixed precursor sheet into a quartz tube, vacuumizing, injecting inert gas, and sealing; performing heat treatment; the quartz glass tube filled with the cold-pressed mixed precursor sheet is put into a quenching medium to be cooled, the cooling rate is larger than 100 DEG C / min, and the cooling time is 10-30 min; and after cooling, taking out the solid electrolyte sample, and grinding. The sulfide solid electrolyte prepared by the embodiment of the invention can realize excellent ionic conductivity of about 5 mS.cm <-1 > in a low-temperature environment of-15 DEG C, effectively alleviates the bottleneck of low ionic migration rate at low temperature, and reduces the accumulation of lithium ions on the surface of a negative electrode, thereby reducing the precipitation risk of lithium dendrites in the charging process of a lithium battery and reducing the potential safety hazard of low-temperature charging.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and more particularly to a sulfide solid electrolyte suitable for low temperatures and its preparation method. Background Technology

[0002] In recent years, all-solid-state lithium-ion batteries (ASSLBs) have replaced traditional liquid electrolytes with solid electrolytes (SEs). This effectively suppresses lithium dendrite growth and prevents it from penetrating the electrolyte layer and causing internal short circuits, thereby completely eliminating safety hazards such as spontaneous combustion and explosion. This addresses the problem of battery thermal runaway at its root and significantly improves the intrinsic safety level of the battery. Simultaneously, all-solid-state lithium-ion batteries can break through the application limitations of high-voltage cathode materials, promoting the practical application of high-energy-density cathode material systems such as LMR, NCM, and high-voltage LiCoO2. Therefore, all-solid-state lithium-ion batteries have become a next-generation core energy storage solution in fields such as electric vehicles, combining high energy density, high safety, and adaptability to extreme environments.

[0003] However, all-solid-state batteries suffer from significant electrochemical performance degradation at low temperatures. The core reason for this is the sharp decrease in the ionic conductivity of the solid electrolyte as the temperature decreases, leading to a decline in the electrochemical performance of Li. + Slow migration kinetics. Excellent low-temperature ionic conductivity not only ensures the stability of Li in solid electrolytes... + Rapid transport at grain / grain boundaries reduces migration activation energy, alleviates ion transport resistance at low temperatures, and effectively reduces charge transfer impedance at the electrode / electrolyte interface, improving kinetic losses caused by poor solid-solid interface contact. This facilitates the transport of Li within the electrode bulk phase. + Diffusion provides ample channels for ion migration.

[0004] It is evident that the low-temperature ionic conductivity of solid-state electrolytes directly affects core performance indicators of all-solid-state batteries, such as low-temperature capacity decay and rate performance. Therefore, improving the low-temperature ionic conductivity of solid-state electrolytes is a crucial technical issue that urgently needs to be addressed to ensure the normal application of all-solid-state batteries in low-temperature environments, providing core support for the practical application of all-solid-state batteries in extreme low-temperature scenarios.

[0005] In low-temperature applications, sulfide solid electrolytes exhibit significant advantages over many other types. They not only possess high room-temperature Li-carbon conductivity, but also... + Electrical conductivity, and Li + The transport number is close to 1, and the contribution of ionic conductivity is almost entirely due to Li. +Migration occurs without interference from other ion migrations. Simultaneously, sulfide solid electrolytes possess excellent mechanical flexibility and interfacial contact properties. This characteristic effectively buffers the volume deformation of the lithium metal anode during battery cycling, maintaining stable contact at the electrode / electrolyte interface and further ensuring continuous ion transport during battery cycling. With these multiple performance advantages, sulfide solid electrolytes have become a solid electrolyte material system with great application potential at low temperatures.

[0006] Currently, the modification of the low-temperature ionic conductivity of sulfide solid electrolytes mainly revolves around two core directions: "improving room temperature ionic conductivity" and "reducing activation energy". Specifically, it can be subdivided into four technical paths: nano-processing, new preparation processes, new electrolyte development, and element doping modification.

[0007] Nanoparticle processing is a technique that uses processes such as ball milling, sol-gel, and spray drying to prepare sulfide electrolytes into nanoscale particles or to modify their surfaces at the nanoscale. Its core principle is to shorten the path of ions across grain boundaries by nanoparticles, while simultaneously reducing grain boundary defects, thereby lowering grain boundary impedance. However, this technology has significant limitations: nanoparticles have a large specific surface area, making them prone to side reactions with air or electrode materials, requiring additional surface coating with materials such as LiPO3; and the nanoscale preparation process is complex and energy-intensive, making it difficult to meet the cost and efficiency requirements of large-scale mass production.

[0008] Novel preparation processes have been developed to control the microstructure and density of sulfide solid electrolytes, with hot isostatic pressing (HIP) being the most widely used. This process applies a high pressure of 600–800 MPa to promote tight bonding of electrolyte particles, significantly increasing density and reducing grain boundary porosity, thereby lowering ion transport resistance. However, this technology requires highly precise equipment, and the purchase and maintenance costs of high-pressure equipment are high. Furthermore, process parameters such as temperature, pressure, and holding time are sensitive to electrolyte performance; even small fluctuations can cause significant differences in product performance.

[0009] The development of novel electrolytes aims to break through the limitations of lithium-sulfur silver-germanium mineral-type and Li... 10 GeP2S 12 Overcoming the structural limitations of mainstream sulfide electrolytes, efforts are being made to develop electrolyte systems with novel crystal structures or compositions. For example, the recently reported Li-Si-S system, specifically the Li7Si2S7I (LSSI) series of electrolytes, utilizes a novel Li-Si-S structure to construct a more efficient Li-Si-S electrolyte. + The transport channel exhibits potential high ionic conductivity. However, the development of this new system faces two major challenges: firstly, the stability of the new structure, and secondly, the Li... +The transport mechanism needs to be verified through multi-dimensional characterization such as X-ray diffraction (XRD) and nuclear magnetic resonance (NMR), which has a long development cycle and consumes a lot of resources. On the other hand, from laboratory synthesis to meeting the interface stability, mechanical performance and other indicators required for the practical application of batteries, long-term process iteration and performance optimization are still needed.

[0010] Elemental doping modification is currently the most widely used, most effective, and most thoroughly researched technical approach. It boasts significant advantages such as multi-dimensional performance synergistic optimization, strong process adaptability, and controllable cost, and has accumulated a wealth of industrialization-related achievements. This technology mainly includes two categories: ordinary doping and high-entropy (HE) doping. Ordinary doping involves introducing one or two heterogeneous elements (such as Cl) into the sulfide electrolyte lattice. - / Br - Replace S 2- ), by optimizing Li + Migration pathways modify conductivity; high-entropy doping involves the synergistic introduction of three or more elements (such as the Li-Sb-S-Cl-Br system) to reduce Li conductivity by constructing a lattice disorder state. + The migration barrier can be improved, and other properties of the electrolyte can be optimized in a synergistic way.

[0011] However, current research on elemental doping modification mainly focuses on static crystal structure parameters (such as lattice constant, atomic occupancy, and crystal symmetry), while generally neglecting the role of lattice dynamics in Li. + Its core role in migration regulation has not yet been fully explored. Especially in the field of high-entropy materials, the understanding of its structure-property relationship is still relatively lacking, and the design of element combinations mostly relies on empirical exploration—usually only regulating structural stability through composition locking or geometric tolerance factors, lacking theoretical guidance at the level of lattice dynamics.

[0012] In fact, lattice vibration characteristics directly affect the ion migration barrier of solid electrolytes, and existing static control strategies have brought the reduction of activation energy close to the bottleneck. Excessive activation energy will directly cause a significant decrease in low-temperature ionic conductivity.

[0013] In summary, there is an urgent need to establish a new strategy based on lattice dynamics control to achieve excellent low-temperature ionic conductivity by simultaneously optimizing the room-temperature ionic conductivity of sulfide solid electrolytes and reducing their activation energy.

[0014] It should be noted that this section is intended to provide background or context for the technical solutions of this disclosure as set forth in the claims. The description herein does not constitute an admission that it is prior art simply because it is included in this section. Summary of the Invention

[0015] The purpose of this invention is to provide a sulfide solid electrolyte suitable for low temperatures and a method for preparing the same, thereby overcoming at least to some extent one or more problems caused by the limitations and defects of related technologies.

[0016] This invention first provides a sulfide solid electrolyte suitable for low temperatures, wherein the sulfide solid electrolyte includes the following two types: Type 1: High-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte, wherein the chemical formula of the high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte is: Li θ X α Y β M γ N λ Wherein, X is any one or more of Ge, Si, and Sn, and Y is any one or more of P, Sb, As, Bi, and Nb; X and Y contain one or more of Sn, Sb, Bi, and Nb; M is any one or more of S, O, and Se, and N is any one or more of F, Cl, Br, and I; M and N contain one or more of Se, Br, and I; and the chemical formula of the high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte satisfies the following conditions: θ+4α+5β-2γ-λ=0, 9.5≤θ<10.4, 1≤α≤2, 10.5≤γ≤12, γ+λ=12; Type 2: High-entropy lithium-silver-germanium ore type solid electrolyte, wherein the chemical formula of the high-entropy lithium-silver-germanium ore type solid electrolyte is: Li θ X α Y β M γ N λ Wherein, X is any one or more of Ge, Si, and Sn, and Y is any one or more of P, Sb, As, Bi, and Nb; X and Y contain one or more of Sn, Sb, Bi, and Nb; M is any one or more of S, O, and Se, and N is any one or more of F, Cl, Br, and I; M and N contain one or more of Se, Br, and I; and the chemical formula of the high-entropy lithium-sulfur silver-germanium ore type solid electrolyte satisfies the following conditions: θ+4α+5β-2γ-λ=0, 5.3≤θ<7.5, 0≤α≤0.8, 4.3≤γ≤6, γ+λ=6.

[0017] In this invention, the high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte comprises: Li 9.54 [Si 0.6 Ge 0.4 ] 1.74 [P 0.8 Sb 0.2 ] 1.44 S 11.1 Se 0.6 Cl0.3 and Li 9.54 [Si 0.7 Sn 0.3 ] 1.74 P 1.44 S 11.4 Se 0.6 The high-entropy lithium-silver-germanium ore-type solid electrolyte comprises: Li 6.2 [Si 0.6 Sn 0.4 ] 0.2 PS4Se 0.5 Cl 0.7 Br 0.8 and Li 6.6 Si 0.4 Sn 0.2 Sb 0.4 S5I.

[0018] The present invention further provides a method for preparing a sulfide solid electrolyte suitable for low temperatures, comprising the following steps: S1. Weigh the raw materials according to the stoichiometric ratio of the sulfide solid electrolyte, dry and grind them to obtain the mixed precursor. S2, the mixture precursor is ball-milled, and after ball milling, the mixture precursor is separated and ground again; S3, Weigh the mixed precursor after further grinding, and use a tablet press to perform unidirectional compression to obtain cold-pressed mixed precursor tablets. S4. The cold-pressed mixed precursor sheet is transferred into a quartz glass tube and vacuumed. Inert gas is injected into the quartz glass tube and then sealed. S5, heat-treat the quartz glass tube containing the cold-pressed mixing precursor sheet; S6. Place the quartz glass tube containing the cold-pressed mixed precursor sheet into the quenching medium for cooling treatment. The cooling rate is >100℃ / min and the cooling time is 10-30 min. After cooling, take out the solid electrolyte sample and grind it again.

[0019] In this invention, in S1, the raw material includes one or more of Se, LiBr and LiI, and contains one or more of Sb2S3, SnS2, Bi2S3 and NbS2.

[0020] In this invention, the grinding time in S1 is 15-30 min.

[0021] In this invention, in S2, the ball-to-material ratio of the ball mill is 2:1-1:1, the ball milling bead size is 2-8 mm, and the ball milling is carried out at a high-energy speed of 200-1000 rpm for 5-30 h. A pulse-type frequency conversion mode is adopted, and the direction is changed every 5-15 min of grinding.

[0022] In this invention, in step S3, a pressure of 100-400 MPa is applied to the tablet press for unidirectional compression, and the pressure holding time is 2-10 min. Each compression produces 40-80 mg of the mixed precursor, and multiple compressions are performed to obtain multiple cold-pressed mixed precursor tablets.

[0023] In this invention, in step S5, the heat treatment process includes: heating to 440℃-570℃ at a rate of 2-10℃ / min and holding at that temperature for 5-15 hours.

[0024] The technical solution provided by this invention may include the following beneficial effects: This invention discloses a sulfide solid electrolyte suitable for low temperatures and its preparation method. The prepared sulfide solid electrolyte can achieve approximately 5 mS·cm at a low temperature of -15℃. -1 Its excellent ionic conductivity effectively alleviates the bottleneck of low ion migration rate at low temperatures, reduces the accumulation of lithium ions on the negative electrode surface, thereby reducing the risk of lithium dendrite precipitation during lithium battery charging and reducing safety hazards during low-temperature charging. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0026] Figure 1 A flowchart illustrating the low-temperature sulfide solid electrolyte and its preparation method in this invention is shown. Figure 2 The following analysis illustrates the effect of lattice softening-configurational entropy compensation on the reduction of phonon frequencies in LGPS-type electrolytes in this invention (based on phonon density of states characterization): (a) Unmodified Li 10 GeP2S 12 (b) Br-Nb synergistic incorporation of high-entropy LGPS; (c) I-Sb synergistic incorporation of high-entropy LGPS; (d) Se-Sn synergistic incorporation of high-entropy LGPS; Figure 3 This invention demonstrates the regulatory effect of lattice softening-configurational entropy compensation on the lithium-ion migration barrier (using Argyrodite-type electrolyte as an example, based on the migration barrier calculation and analysis using transition state theory). Figure 4 This invention demonstrates the long-cycle performance of the all-solid-state lithium battery at -15°C with a 3C rate: (a) Lattice softening-configurational entropy compensation modified high-entropy LGPS type solid electrolyte and unmodified Li10 GeP2S 12 (b) Lattice softening-configuration entropy compensation modified high-entropy Argyrodite type solid electrolyte with unmodified Li6PS5Cl. Detailed Implementation

[0027] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0028] Furthermore, the accompanying drawings are merely illustrative diagrams of embodiments of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0029] This example embodiment first provides a sulfide solid electrolyte suitable for low temperatures, which includes the following two types: Type 1: High-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte, wherein the chemical formula of the high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte is: Li θ X α Y β M γ N λ Wherein, X is any one or more of Ge, Si, and Sn, and Y is any one or more of P, Sb, As, Bi, and Nb; X and Y contain one or more of Sn, Sb, Bi, and Nb; M is any one or more of S, O, and Se, and N is any one or more of F, Cl, Br, and I; M and N contain one or more of Se, Br, and I; and the chemical formula of the high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte satisfies the following conditions: θ+4α+5β-2γ-λ=0, 9.5≤θ<10.4, 1≤α≤2, 10.5≤γ≤12, γ+λ=12; Type 2: High-entropy lithium-silver-germanium ore type solid electrolyte, wherein the chemical formula of the high-entropy lithium-silver-germanium ore type solid electrolyte is: Li θ X α Y β M γ N λWherein, X is any one or more of Ge, Si, and Sn, and Y is any one or more of P, Sb, As, Bi, and Nb; X and Y contain one or more of Sn, Sb, Bi, and Nb; M is any one or more of S, O, and Se, and N is any one or more of F, Cl, Br, and I; M and N contain one or more of Se, Br, and I; and the chemical formula of the high-entropy lithium-sulfur silver-germanium ore type solid electrolyte satisfies the following conditions: θ+4α+5β-2γ-λ=0, 5.3≤θ<7.5, 0≤α≤0.8, 4.3≤γ≤6, γ+λ=6.

[0030] The sulfide solid electrolyte in this embodiment, suitable for low temperatures, can achieve ~5 mS·cm at a low temperature of -15°C. -1 The excellent ionic conductivity effectively alleviates the bottleneck of low ion migration rate at low temperatures, reduces the accumulation of lithium ions on the negative electrode surface, thereby reducing the risk of lithium dendrite precipitation during lithium battery charging and mitigating safety hazards during low-temperature charging. This invention is expected to provide strong technical support for electric vehicles to achieve stable long-term range in low-temperature scenarios such as winter and high altitudes.

[0031] This example embodiment further provides a method for preparing a sulfide solid electrolyte suitable for low temperatures, comprising the following steps: S1. Weigh the raw materials according to the stoichiometric ratio of the sulfide solid electrolyte, dry and grind them to obtain the mixed precursor.

[0032] The raw materials include one or more of Se, LiBr, and LiI, and contain one or more of Sb₂S₃, SnS₂, Bi₂S₃, and NbS₂. The total weight of the raw materials is 400-800 mg, and the purity of all raw materials is not less than 99.9%. Before grinding, the raw materials are placed in a glove box and vacuum dried at 50-80℃ for 8-14 h, with a water content of <0.1 ppm and an oxygen content of <0.1 ppm in the glove box. Then, the dried raw materials are added to an agate mortar and ground and mixed for 15-30 min, with continuous stirring during the grinding process to ensure that there is no obvious agglomeration of the material.

[0033] S2, the precursor of the mixture is ball-milled, and after the ball milling is completed, the precursor of the mixture is separated and ground again.

[0034] Specifically, the obtained mixed precursor is placed in a ball mill jar made of zirconia or polytetrafluoroethylene, and zirconia grinding beads are added, controlling the ball-to-material ratio at 2:1-1:1. The grinding beads have a particle size of 2-8 mm, and can be single-size or a mixture of 2-4 mm / 5-8 mm grinding beads. The ball mill jar is placed in a planetary ball mill and ball-milled at 200-1000 rpm for 5-30 hours. A pulse-type frequency conversion mode is used, and the direction is changed every 5-15 minutes to avoid material accumulation. After ball milling, the ball mill jar is opened in the glove box, and the synthesized mixed precursor is separated from the grinding beads and ground again in a mortar for 15-30 minutes to make it homogenous.

[0035] S3, Weigh the re-ground mixture precursor and use a tablet press to perform unidirectional compression to obtain cold-pressed mixed precursor tablets.

[0036] Specifically, weigh 40-80 mg of the mixed precursor and pour it into a 10 mm diameter polyetheretherketone (PEEK) or alumina mold. Place the mold on a tablet press and apply a pressure of 100-400 MPa for unidirectional compression. Hold the pressure for 2-10 minutes to obtain a cold-pressed mixed precursor tablet. Repeat the above steps until all electrolyte powder is compressed into cold-pressed mixed precursor tablets.

[0037] S4. The cold-pressed mixed precursor sheet is transferred into a quartz glass tube, and a vacuum treatment is performed. Inert gas is injected into the quartz glass tube, and then it is sealed. The vacuum level needs to reach 1×10⁻⁶. -4 Pa-3×10 -4 Pa. Inert gas (one or more combinations of argon, helium, or nitrogen, with argon being the optimal choice) is introduced into the quartz tube until the internal pressure is close to atmospheric pressure to prevent electrolyte oxidation. The quartz tube is then heated using a flame gun at 3000℃-3500℃ to melt and seal the necking.

[0038] S5. The quartz glass tube containing the cold-pressed mixed precursor sheet is subjected to heat treatment. Specifically, the sealed quartz glass tube is placed in a muffle furnace for heat treatment, and the temperature is increased to 440℃-570℃ at a rate of 2-10℃ / min, and held at that temperature for 5-15 h.

[0039] S6. Place the quartz glass tube containing the cold-pressed mixed precursor sheet into a quenching medium for cooling at a rate >100℃ / min for 10-30 min. After cooling, remove the solid electrolyte sample and grind it again. The quenching medium can be liquid nitrogen, an ice-water mixture, or a dry ice-ethanol mixture, selected according to the cooling rate. The cooling rate can be 150℃ / min, 200℃ / min, etc., but is not limited to these. After cooling, remove the quartz glass tube, transfer it to a glove box for crushing, remove the internal solid electrolyte sample, and grind it again in a mortar for 15-30 min to ensure sample homogeneity.

[0040] This embodiment proposes a novel design approach based on lattice dynamics to control the elemental composition and doping ratio of sulfide solid electrolytes. Through the synergistic effect of lattice softening and configuration entropy compensation, a sulfide solid electrolyte with excellent low-temperature ionic conductivity is obtained. Specifically, this invention introduces one or more elements from Se, Br, and I into the sulfide solid electrolyte, utilizing the difference in polarizability between these elements and the original anions to induce optical phonon softening, thereby achieving Li… + Dynamic optimization of migration channels establishes a novel mechanism for phonon-ion coupling modification; simultaneously, the introduction of any one or more elements from Sb, Sn, Bi, and Nb induces configurational entropy gain to modulate Li. + Effective concentration, to compensate for the attenuation of the pre-exponential factor σ0 in the Arrhenius formula due to the Meyer-Neldel rule after lattice softening.

[0041] Compared to the static substitution effect of traditional doping, the novel "phonon-ion" coupling modification mechanism constructed in this invention can be applied to most sulfide solid electrolyte systems, simultaneously achieving an increase in room temperature ionic conductivity and a decrease in activation energy. This mechanism enables sulfide solid electrolytes to achieve approximately 5 mS·cm at a low temperature of -15℃. -1 The excellent ionic conductivity effectively alleviates the bottleneck of low ion migration rate at low temperatures, reduces the accumulation of lithium ions on the negative electrode surface, thereby reducing the risk of lithium dendrite precipitation during lithium battery charging and mitigating safety hazards during low-temperature charging. This invention is expected to provide strong technical support for electric vehicles to achieve stable long-term range in low-temperature scenarios such as winter and high altitudes.

[0042] The following are specific experimental examples and comparative examples to illustrate the preparation process and beneficial effects of the electrolyte of this application.

[0043] Experimental Example 1 (1) The raw materials Li2S, Ge, P, S, Se, SiS2, Sb2S3 and LiCl are combined to form the chemical formula Li 9.54 [Si 0.6 Ge 0.4 ]1.74 [P 0.8 Sb 0.2 ] 1.44 S 11.1 Se 0.6 Cl 0.3 A high-entropy LGPS type sulfide solid electrolyte. The total weight of the raw materials is 500 mg. The purity of all raw materials is not less than 99.9%.

[0044] (2) Place all raw materials in a glove box and vacuum dry them at 75°C for 10 h. The water content and oxygen content in the glove box are <0.1 ppm and <0.1 ppm, respectively.

[0045] (3) Add the dried raw materials to the agate mortar according to the stoichiometric ratio, grind and mix for 25 min, and stir continuously during the grinding process to ensure that the materials do not agglomerate significantly.

[0046] (4) Place the obtained mixed precursor in a zirconia ball mill jar, add zirconia ball milling beads, control the ball-to-material ratio to be 1.5:1, and select a mixed specification of 2 mm, 4 mm and 6 mm particle size for the ball milling beads.

[0047] (5) Place the ball mill jar in a planetary ball mill and ball mill at a speed of 550 rpm for 20 h. Use pulse frequency conversion mode and change the direction every 10 min to avoid material accumulation.

[0048] (6) After ball milling, open the ball mill jar in the glove box, separate the synthesized mixed precursor from the ball mill beads, and grind it again in the mortar for 25 minutes to make it uniform.

[0049] (7) Weigh 50 mg of the mixed precursor and pour it into a polyetheretherketone or alumina mold with a diameter of 10 mm. Place it on a tablet press and apply a pressure of 200 MPa for unidirectional compression. Hold the pressure for 3 min to obtain a cold-pressed mixed precursor tablet. Repeat the above steps until all electrolyte powders are compressed into cold-pressed mixed precursor tablets.

[0050] (8) Transfer the cold-pressed mixed precursor sheet into a quartz glass tube, connect the quartz tube to a vacuum pump and continuously evacuate until the vacuum level inside the tube reaches 2×10⁻⁶. -4 Pa.

[0051] (9) Introduce inert argon gas into the quartz tube until the gas pressure inside the tube is close to atmospheric pressure to avoid electrolyte oxidation.

[0052] (10) The quartz tube is fired with a flame gun at 3000℃-3500℃ to melt and seal the neck of the quartz tube.

[0053] (11) The sealed quartz glass tube was placed in a muffle furnace for heat treatment, and the temperature was raised to 475°C at a rate of 4°C / min and held for 12 h.

[0054] (12) Immediately place the quartz tube that has completed the solid-phase reaction into the quenching medium. The cooling medium is liquid nitrogen, the cooling rate is >100℃ / min, and the cooling time is 20 min.

[0055] (13) After cooling, remove the quartz glass tube, transfer it to the glove box to break it, take out the solid electrolyte sample inside and grind it again in the mortar for 20 min to ensure that the sample is uniform.

[0056] Experiment Example 2 (1) The raw materials Li2S, SiS2, P, S, Se and SnS2 are combined to form the chemical formula Li 9.54 [Si 0.7 Sn 0.3 ] 1.74 P 1.44 S 11.4 Se 0.6 LGPS type sulfide solid electrolyte. The total weight of raw materials is 800 mg. The purity of all raw materials is not less than 99.9%.

[0057] (2) Place all raw materials in a glove box and vacuum dry them at 75°C for 14 h. The water content and oxygen content in the glove box are <0.1ppm and <0.1ppm, respectively.

[0058] (3) Add the dried raw materials to the agate mortar according to the chemical stoichiometric ratio, grind and mix for 20 min, and stir continuously during the grinding process to ensure that the materials do not agglomerate significantly.

[0059] (4) Place the obtained mixed precursor in a ball milling jar made of polytetrafluoroethylene, add zirconia grinding beads, control the ball-to-material ratio to be 1:1, and select grinding beads with a particle size of 4 mm, 6 mm and 8 mm.

[0060] (5) Place the ball mill jar in a planetary ball mill and ball mill at 1000 rpm for 8 hours. Use pulse frequency conversion mode and change the direction every 8 minutes of grinding to avoid material accumulation.

[0061] (6) After ball milling, open the ball mill jar in the glove box, separate the synthesized mixed precursor from the ball mill beads, and grind it again in the mortar for 30 minutes to make it uniform.

[0062] (7) Weigh 80 mg of the mixed precursor and pour it into a polyetheretherketone or alumina mold with a diameter of 10 mm. Place it on a tablet press and apply a pressure of 400 MPa for unidirectional compression. Hold the pressure for 6 min to obtain a cold-pressed mixed precursor tablet. Repeat the above steps until all electrolyte powders are compressed into cold-pressed mixed precursor tablets.

[0063] (8) Transfer the cold-pressed mixed precursor sheet into a quartz glass tube, connect the quartz tube to a vacuum pump and continuously evacuate until the vacuum level inside the tube reaches 1×10⁻⁶. -4 Pa.

[0064] (9) Introduce inert argon gas into the quartz tube until the gas pressure inside the tube is close to atmospheric pressure to avoid electrolyte oxidation.

[0065] (10) The quartz tube is fired with a flame gun at 3000℃-3500℃ to melt and seal the neck of the quartz tube.

[0066] (11) The sealed quartz glass tube was placed in a muffle furnace for heat treatment, and the temperature was raised to 440°C at a rate of 10°C / min and held for 7 h.

[0067] (12) Immediately place the quartz tube that has completed the solid-phase reaction into the quenching medium. The cooling medium is liquid nitrogen, the cooling rate is >100℃ / min, and the cooling time is 25 min.

[0068] (13) After cooling, remove the quartz glass tube, transfer it to the glove box to break it, take out the solid electrolyte sample inside and grind it again in the mortar for 30 min to ensure that the sample is uniform.

[0069] Experimental Example 3 (1) The raw materials Li2S, P, S, Se, SiS2, SnS2, LiCl and LiBr are combined to form the chemical formula Li 6.2 [Si 0.6 Sn 0.4 ] 0.2 PS4Se 0.5 Cl 0.7 Br 0.8 A high-entropy silver-germanium sulfide solid electrolyte. The total weight of the raw materials is 700 mg. The purity of all raw materials is not less than 99.9%.

[0070] (2) Place all raw materials in a glove box and vacuum dry them at 65°C for 12 h. The water content and oxygen content in the glove box are <0.1ppm and <0.1ppm, respectively.

[0071] (3) Add the dried raw materials to the agate mortar according to the chemical stoichiometric ratio, grind and mix for 15 min, and stir continuously during the grinding process to ensure that the materials do not agglomerate significantly.

[0072] (4) Place the obtained mixed precursor in a ball milling jar made of polytetrafluoroethylene, add zirconia grinding beads, control the ball-to-material ratio to be 2:1, and select grinding beads with a mixed size of 4 mm and 8 mm.

[0073] (5) Place the ball mill jar in a planetary ball mill and ball mill at 800 rpm for 10 hours. Use pulse frequency conversion mode and change the direction every 15 minutes of grinding to avoid material accumulation.

[0074] (6) After ball milling, open the ball mill jar in the glove box, separate the synthesized mixed precursor from the ball mill beads, and grind it again in the mortar for 30 minutes to make it uniform.

[0075] (7) Weigh 70 mg of the mixed precursor and pour it into a polyetheretherketone or alumina mold with a diameter of 10 mm. Place it on a tablet press and apply a pressure of 150 MPa for unidirectional compression. Hold the pressure for 10 min to obtain a cold-pressed mixed precursor tablet. Repeat the above steps until all electrolyte powders are compressed into cold-pressed mixed precursor tablets.

[0076] (8) Transfer the cold-pressed mixed precursor sheet into a quartz glass tube, connect the quartz tube to a vacuum pump and continuously evacuate until the vacuum level inside the tube reaches 3×10⁻⁶. -4 Pa.

[0077] (9) Introduce inert argon gas into the quartz tube until the gas pressure inside the tube is close to atmospheric pressure to avoid electrolyte oxidation.

[0078] (10) The quartz tube is fired with a flame gun at 3000℃-3500℃ to melt and seal the neck of the quartz tube.

[0079] (11) The sealed quartz glass tube was placed in a muffle furnace for heat treatment, and the temperature was increased to 550°C at a rate of 5°C / min and held for 8 hours.

[0080] (12) Immediately place the quartz tube that has completed the solid-phase reaction into the quenching medium. The cooling medium is an ice-water mixture, the cooling rate is >100℃ / min, and the cooling time is 10 min.

[0081] (13) After cooling, remove the quartz glass tube, transfer it to the glove box to break it, take out the solid electrolyte sample inside and grind it again in the mortar for 15 min to ensure that the sample is uniform.

[0082] Experiment Example 4 (1) Take raw materials Li2S, S, SiS2, SbS2, SnS2, and LiI and combine them with the chemical formula Li 6.6 Si0.4 Sn 0.2 Sb 0.4 S5I is a lithium-sulfur silver-germanium ore type sulfide solid electrolyte. The total weight of the raw materials is 600 mg. The purity of all raw materials is not less than 99.9%.

[0083] (2) Place all raw materials in a glove box and vacuum dry them at 80°C for 8 hours. The water content and oxygen content in the glove box should be <0.1ppm and <0.1ppm, respectively.

[0084] (3) Add the dried raw materials to the agate mortar according to the stoichiometric ratio, grind and mix for 30 min, and stir continuously during the grinding process to ensure that the materials do not agglomerate significantly.

[0085] (4) Place the obtained mixed precursor in a zirconia ball milling jar, add zirconia ball milling beads, add zirconia ball milling beads with a single particle size of 4 mm, and control the ball-to-material ratio to be 1:1.

[0086] (5) Place the ball mill jar in a planetary ball mill and ball mill at a speed of 650 rpm for 12 hours. Use a pulse frequency conversion mode and change the direction every 5 minutes of grinding to avoid material accumulation.

[0087] (6) After ball milling, open the ball mill jar in the glove box, separate the synthesized mixed precursor from the ball mill beads, and grind it again in the mortar for 15 min to make it uniform.

[0088] (7) Weigh 60 mg of the mixed precursor and pour it into a polyetheretherketone or alumina mold with a diameter of 10 mm. Place it on a tablet press and apply a pressure of 300 MPa for unidirectional compression. Hold the pressure for 3 min to obtain a cold-pressed mixed precursor tablet. Repeat the above steps until all electrolyte powders are compressed into cold-pressed mixed precursor tablets.

[0089] (8) Transfer the cold-pressed mixed precursor sheet into a quartz glass tube, connect the quartz tube to a vacuum pump and continuously evacuate until the vacuum level inside the tube reaches 2.5 × 10⁻⁶. -4 Pa.

[0090] (9) Introduce an inert mixture of argon and helium into the quartz tube until the pressure inside the tube is close to atmospheric pressure to avoid electrolyte oxidation.

[0091] (10) The quartz tube is fired with a flame gun at 3000℃-3500℃ to melt and seal the neck of the quartz tube.

[0092] (11) The sealed quartz glass tube was placed in a muffle furnace for heat treatment, and the temperature was raised to 535°C at a rate of 10°C / min and held for 15 h.

[0093] (12) Immediately place the quartz tube that has completed the solid-phase reaction into the quenching medium. The cooling medium is a dry ice-ethanol mixture, the cooling rate is >100℃ / min, and the cooling time is 30 min.

[0094] (13) After cooling, remove the quartz glass tube, transfer it to the glove box to break it, take out the solid electrolyte sample inside and grind it again in the mortar for 30 min to ensure that the sample is uniform.

[0095] Comparative Example 1 Comparative Example 1 is the same as Experimental Example 1, except that the solid electrolyte prepared is an LGPS type sulfide electrolyte Li. 9.54 [Si 0.6 Ge 0.4 ] 1.74 P 1.44 S 11.7 Cl 0.3 The raw materials do not contain SbS2 or Se.

[0096] Comparative Example 2 Comparative Example 2 is the same as Experimental Example 2, except that the solid electrolyte prepared is an LGPS type sulfide electrolyte Li. 9.54 Si 1.74 P 1.44 S 12 The raw materials do not contain SnS2 or Se.

[0097] Comparative Example 3 Comparative Example 3 is the same as Experimental Example 3, except that the solid electrolyte prepared is a lithium sulfide-germanium ore type sulfide electrolyte Li. 6.2 Si 0.2 PS 4.5 Cl 1.5 The raw materials do not contain SbS2, Se, or LiBr.

[0098] Comparative Example 4 Comparative Example 4 is the same as Experimental Example 4, except that the solid electrolyte prepared is a lithium sulfide-germanium ore type sulfide electrolyte Li. 6.4 Si 0.4 S5Cl, the raw materials do not contain SbS2 and SnS2; the raw material LiI is replaced with LiCl.

[0099] Table 1 summarizes the activation energy data of high-entropy LGPS type sulfide solid electrolytes after doping with different elements. As shown in Table 1, the activation energy of the system does not change significantly after the doping of Sb, Sn, Bi, and Nb; however, the activation energy of high-entropy LGPS is significantly reduced by the doping of Se, Br, and I through the lattice softening effect, reaching the level of Li. + Transmission provides an energy advantage.

[0100] Table 1: Summary of Activation Energy for Lattice Softening-Configuration Entropy Compensation Modified High-Entropy LGPS Electrolytes (Unit: eV)

[0101] Table 2 summarizes the room temperature (25℃) ionic conductivity data of high-entropy LGPS type sulfide solid electrolytes after different element doping. As shown in Table 2, Se, Br, and I doping has no significant effect on improving room temperature ionic conductivity; while the incorporation of heterogeneous elements such as Sb, Sn, Bi, and Nb can effectively optimize Li through configuration entropy-induced effects. + The transport channel compensates for the attenuation of the pre-exponential factor σ0 in the Arrhenius formula due to the Meyer-Neldel rule after lattice softening, thus significantly improving the room-temperature ion conductivity of the material.

[0102] Table 2: Summary of Ionic Conductivity of High-Entropy LGPS Electrolytes Modified by Lattice Softening-Configuration Entropy Compensation at 25℃ (Unit: mS·cm) -1 )

[0103] Table 3 summarizes the ionic conductivity of high-entropy LGPS-type sulfide solid electrolytes at -15℃. The data in Table 3 show that the electrolyte samples prepared using the synergistic strategy of "lattice softening-configurational entropy compensation" exhibit significantly better low-temperature ionic conductivity than the two comparative sample groups: one group consists of high-entropy LGPS electrolytes without any control strategy, and the other group consists of modified samples using only a single lattice softening (Se / Br / I doping) or single configurational entropy compensation (Sb / Sn / Bi / Nb doping) strategy.

[0104] Table 3: Summary of Ionic Conductivity of High-Entropy LGPS Electrolytes Modified by Lattice Softening-Configuration Entropy Compensation at -15℃ (Unit: mS·cm) -1 )

[0105] Figure 2 (ad) presents three groups of high-entropy LGPS-type sulfide solid electrolytes prepared by a synergistic strategy of lattice softening-configurational entropy compensation, as well as unmodified Li 10 GeP2S 12 The results of the comparison of phonon density of states. From Figure 2 As can be seen, after synergistic modification, the phonon density of states of the LGPS-type electrolyte decreased from 7.8 THz to 6.8-7.3 THz, with a particularly significant lattice softening effect. Furthermore, the unmodified Li...10 GeP2S 12 A significant longitudinal optical-transverse optical (LO-TO) phonon branching effect appears in the high-frequency region. This phenomenon induces strong Coulomb polarization, which intensifies phonon scattering and compresses Li. + The migration channel ultimately led to Li + The migration barrier is increased. However, no LO-TO splitting was observed in any of the synergistically modified samples, thus providing a potential for Li... + Rapid transport provides a favorable lattice dynamics environment.

[0106] Figure 3 The study presented a lithium-sulfur silver-germanium ore-type sulfide electrolyte (Li6PS5Cl) and its Li after Sb-Se or Sn-I synergistic incorporation. + The migration barrier changes. Calculation results show that the Li in unco-doped Li6PS5Cl... + The migration barrier is 0.59 eV; however, after Sb-Se synergistic doping, its Li + The migration barrier was significantly reduced to 0.26 eV; after Sn-I synergistic doping, the barrier was further reduced to 0.24 eV. The core mechanism of this barrier reduction lies in the adoption of a synergistic strategy of "lattice softening-configurational entropy compensation," which induces lattice softening by controlling the polarizability difference between the dopant ions and the original anions, while simultaneously enhancing lattice disorder by increasing the system's configurational entropy. This synergistic effect enables Li... + Dynamic optimization of the migration path ultimately significantly reduced Li + Local high-energy potential barriers during migration.

[0107] Figure 4 (ab) presents two types of high-entropy sulfide solid electrolytes prepared at -15℃ using a synergistic strategy of lattice softening and configurational entropy compensation: LGPS type (HE-LGPS-Sn) 0.4 Se 0.6 Lithium-sulfur silver-germanium ore type (HE-Argyrodite-Sn) 0.4 Se 0.6 ), and the corresponding unmodified solid electrolytes (Li, respectively) 10 GeP2S 12 Comparison of the long-cycle charge-discharge performance of Li6PS5Cl at 3C high rate.

[0108] For the LGPS system, HE-LGPS-Sn 0.4 Se 0.6The base cell exhibited excellent low-temperature cycling stability, with an initial discharge capacity of 106.75 mAh / g, maintaining 79.50 mAh / g after 300 cycles, representing a capacity retention of 74.47%, and no significant capacity drop was observed throughout the cycle. In contrast, unmodified Li... 10 GeP2S 12 Its cycling performance degrades drastically. Its initial discharge capacity is only 78.52 mAh / g, and after 100 cycles, the capacity drops to 50.61 mAh / g (capacity retention rate of 64.45%). After continuing to cycle for about 150 cycles, it almost fails.

[0109] This pattern is also significant in the lithium-sulfur silver-germanium ore system. HE-Argyrodite-Sn 0.4 Se 0.6 The base battery had an initial discharge capacity of 110.22 mAh / g, and after 300 cycles, the remaining capacity was 83.99 mAh / g, with a capacity retention rate as high as 76.20%, and no obvious capacity decay inflection point was observed. In contrast, the unmodified Li6PS5Cl had an initial discharge capacity of 90.27 mAh / g, but the capacity dropped to 50.81 mAh / g after 100 cycles (capacity retention rate of 56.29%), and almost failed after about 150 cycles.

[0110] The above results confirm that unmodified Li 10 GeP2S 12 Li and Li6PS5Cl at low temperature + The inherent transmission lag is exacerbated by high-rate operation, further hindering Li's performance. + Transmission obstruction ultimately leads to battery failure; however, a solid-state electrolyte designed with lattice softening and configurational entropy compensation effectively alleviates the problem of Li-C at low temperatures and high rates. + The transmission bottleneck was overcome, demonstrating excellent long-term cycling stability and verifying the effectiveness of this strategy in improving the adaptability of solid electrolytes to extreme operating conditions.

[0111] In summary, the beneficial effects of the present invention include: (1) To address the limitations of traditional sulfide solid electrolyte modification strategies, which have narrow applicability and limited effectiveness, this invention pioneers a synergistic modification method of "lattice softening-configurational entropy compensation". This method is widely applicable to mainstream sulfide solid electrolyte systems such as LGPS type and lithium sulfide silver germanium mineral type, providing a universal modification technology framework with strong versatility and high scalability.

[0112] (2) A coupled regulation mechanism of lattice dynamics and ion migration was proposed, abandoning the traditional static lattice modification thinking and turning to dynamic lattice regulation. By precisely designing and regulating the polarizability difference of anion sites, the optical phonons are induced to undergo directional softening, thereby reducing the activation energy barrier of electrolyte ion migration from the root of dynamics.

[0113] (3) To address the problem that lattice softening in the Meyer-Neldel rule inevitably leads to the decay of the pre-exponential factor σ0 in the Arrhenius formula, this invention improves the Li-Neldel structure by introducing metal cations in a targeted manner, thereby increasing the configuration entropy without affecting the lattice softening effect. + Migrating networks improves Li + The effective concentration. This innovation achieves, for the first time, the synergistic optimization of ionic conductivity and activation energy, resolving the contradiction of "one increasing while the other decreases" between the two in traditional modification strategies.

[0114] (4) The high-entropy LGPS type sulfide solid electrolyte synthesized based on the lattice softening-configurational entropy compensation strategy exhibits approximately 5 mS·cm -1 Excellent low-temperature ionic conductivity. This type of electrolyte can alleviate the problem of Li at low temperatures. + The problem of low migration rate, reduce Li + The accumulation on the negative electrode surface reduces the risk of lithium dendrite precipitation, thereby mitigating the safety hazards of low-temperature charging of lithium solid-state batteries.

[0115] (5) A synergistic integration of simple doping and solid-state thermal reaction methods is adopted. The entire process has significant advantages such as simple operation and low preparation cost, effectively reducing the threshold for large-scale production and possessing high commercialization potential.

[0116] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A sulfide solid electrolyte suitable for low temperatures, characterized in that, The sulfide solid electrolyte includes the following two types: Type 1: High-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte, wherein the chemical formula of the high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte is: Li θ X α Y β M γ N λ Wherein, X is any one or more of Ge, Si, and Sn, and Y is any one or more of P, Sb, As, Bi, and Nb; X and Y contain one or more of Sn, Sb, Bi, and Nb; M is any one or more of S, O, and Se, and N is any one or more of F, Cl, Br, and I; M and N contain one or more of Se, Br, and I; and the chemical formula of the high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte satisfies the following conditions: θ+4α+5β-2γ-λ=0, 9.5≤θ<10.4, 1≤α≤2, 10.5≤γ≤12, γ+λ=12; Type 2: High-entropy lithium-silver-germanium ore type solid electrolyte, wherein the chemical formula of the high-entropy lithium-silver-germanium ore type solid electrolyte is: Li θ X α Y β M γ N λ Wherein, X is any one or more of Ge, Si, and Sn, and Y is any one or more of P, Sb, As, Bi, and Nb; X and Y contain one or more of Sn, Sb, Bi, and Nb; M is any one or more of S, O, and Se, and N is any one or more of F, Cl, Br, and I; M and N contain one or more of Se, Br, and I; and the chemical formula of the high-entropy lithium-sulfur silver-germanium ore type solid electrolyte satisfies the following conditions: θ+4α+5β-2γ-λ=0, 5.3≤θ<7.5, 0≤α≤0.8, 4.3≤γ≤6, γ+λ=6.

2. The sulfide solid electrolyte suitable for low temperatures according to claim 1, characterized in that, The high-entropy lithium-germanium-phosphorus-sulfur type solid electrolyte includes: Li 9.54 [Si 0.6 Ge 0.4 ] 1.74 [P 0.8 Sb 0.2 ] 1.44 S 11.1 Se 0.6 Cl 0.3 and Li 9.54 [Si 0.7 Sn 0.3 ] 1.74 P 1.44 S 11.4 Se 0.6 The high-entropy lithium-silver-germanium ore-type solid electrolyte comprises: Li 6.2 [Si 0.6 Sn 0.4 ] 0.2 PS4Se 0.5 Cl 0.7 Br 0.8 and Li 6.6 Si 0.4 Sn 0.2 Sb 0.4 S5I.

3. The method for preparing a sulfide solid electrolyte suitable for low temperatures as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Weigh the raw materials according to the stoichiometric ratio of the sulfide solid electrolyte, dry and grind them to obtain the mixed precursor. S2, the mixture precursor is ball-milled, and after ball milling, the mixture precursor is separated and ground again; S3, Weigh the mixed precursor after further grinding, and use a tablet press to perform unidirectional compression to obtain cold-pressed mixed precursor tablets. S4. The cold-pressed mixed precursor sheet is transferred into a quartz glass tube and vacuumed. Inert gas is injected into the quartz glass tube and then sealed. S5, heat-treat the quartz glass tube containing the cold-pressed mixing precursor sheet; S6. Place the quartz glass tube containing the cold-pressed mixed precursor sheet into the quenching medium for cooling treatment. The cooling rate is >100℃ / min and the cooling time is 10-30 min. After cooling, take out the solid electrolyte sample and grind it again.

4. The method for preparing a sulfide solid electrolyte suitable for low temperatures according to claim 3, characterized in that, In S1, the raw materials include one or more of Se, LiBr and LiI, and contain one or more of Sb2S3, SnS2, Bi2S3 and NbS2.

5. The method for preparing a low-temperature sulfide solid electrolyte according to claim 3, characterized in that, The grinding time in S1 is 15-30 min.

6. The method for preparing a low-temperature sulfide solid electrolyte according to claim 3, characterized in that, In S2, the ball-to-material ratio of the ball mill is 2:1-1:1, the ball milling bead size is 2-8 mm, and the high-energy ball milling is carried out at a speed of 200-1000 rpm for 5-30 hours. A pulse-type frequency conversion mode is adopted, and the direction is changed every 5-15 minutes of grinding.

7. The method for preparing a low-temperature sulfide solid electrolyte according to claim 3, characterized in that, In S3, a pressure of 100-400 MPa is applied to the tablet press for unidirectional compression, and the holding time is 2-10 min. Each compression produces 40-80 mg of the mixed precursor, and multiple compressions are performed to obtain multiple cold-pressed mixed precursor tablets.

8. The method for preparing a low-temperature sulfide solid electrolyte according to any one of claims 3 to 7, characterized in that, In S5, the heat treatment process includes: heating to 440℃-570℃ at a rate of 2-10℃ / min and holding at that temperature for 5-15 hours.

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