A multilayer sulfide solid electrolyte structure, a preparation method and applications

Abstract

This invention relates to the field of solid-state battery fabrication technology, and particularly to a multilayer sulfide solid electrolyte structure, its preparation method, and its application. The structure is a sandwich structure, comprising a first electrolyte layer, an electrolyte-S layer, and a second electrolyte layer stacked sequentially. The electrolyte-S layer contains electrolyte and sulfur, with the sulfur content ranging from 5 wt% to 25 wt%. This invention proposes a "point-defense reactive armor" dendrite protection strategy: during battery cycling, lithium dendrites grow from the electrolyte side and then penetrate the electrolyte-S layer. Sulfur in the electrolyte-S layer is distributed in particulate form. When the tip of a lithium dendrite encounters sulfur in the electrolyte-S layer, it reacts with lithium to generate lithium sulfide, which has passivating properties, thereby preventing the dendrite from continuing to grow. This solves the problem of lithium dendrite growth in sulfide solid electrolytes in the prior art.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery fabrication technology, specifically to a multilayer sulfide solid electrolyte structure, its preparation method, and its application. Background Technology

[0002] With the transformation of the global energy structure and the rapid development of industries such as electronic devices and electric vehicles, next-generation energy storage technologies with high energy density and high safety have become a core goal pursued by the scientific and industrial communities. Among numerous candidate solutions, all-solid-state lithium batteries are considered a key path to achieving a revolutionary breakthrough in battery safety because they fundamentally eliminate the flammable and leaky organic liquid electrolytes found in traditional lithium-ion batteries. They are expected to meet the stringent requirements of future long-range electric vehicles, large-scale energy storage systems, and high-end portable electronic devices for energy storage media. In the construction of all-solid-state batteries, the solid electrolyte, as the core component for transporting lithium ions and separating the positive and negative electrodes, directly determines the overall efficiency of the battery. Among the main solid electrolyte systems such as oxides, polymers, halides, and sulfides, sulfide solid electrolytes stand out due to their ultra-high lithium-ion conductivity, becoming the core material for preparing high-energy-density solid-state batteries.

[0003] However, most sulfide solid electrolytes are unstable when in contact with metallic lithium, exhibiting significant spontaneous reaction driving forces. This intrinsic thermodynamic instability triggers continuous, dynamic, and complex interfacial side reactions during actual battery cycling due to repeated lithium-ion deposition and dissolution. The products of these side reactions are often a series of complex interfacial phases with non-uniform ion / electron conductivity. This unstable interfacial environment induces the continuous growth of lithium dendrites. During charging, lithium ions tend to preferentially reduce to metallic lithium at certain interfacial defects, grain boundaries, or electron percolation channels, forming local protrusions, i.e., lithium dendrites. Once lithium dendrites germinate, their sharp tips further distort the local electric field, exacerbating the non-uniform flux of lithium ions and leading to accelerated dendrite growth. The growth of lithium dendrites is catastrophic for solid-state batteries. Unlike dendrites in liquid electrolytes, which can be dissolved and regenerated, in solid electrolytes, lithium dendrite growth is a typical destructive physical penetration process. Metallic lithium deposition is accompanied by huge volume changes and generates significant mechanical stress. When local stress exceeds the fracture strength of the sulfide electrolyte material or is released along weak points such as grain boundaries, microcracks will be induced and propagated. Newly deposited lithium metal will then rapidly fill these newly formed crack spaces, making the crack tips new lithium deposition fronts. This cycle continues, allowing lithium dendrites to continuously split and extend within the solid electrolyte like wedges. Eventually, the dendrites may penetrate the entire electrolyte membrane layer, directly connecting to the positive and negative electrodes of the battery, causing an internal short circuit. The enormous heat released during a short circuit is difficult to dissipate quickly in the closed system of a solid-state battery, which lacks liquid convection cooling, easily leading to thermal runaway and serious safety accidents such as battery fires and explosions. Therefore, the lithium dendrite penetration problem not only severely restricts the cycle life and coulombic efficiency of all-solid-state batteries based on sulfide electrolytes and lithium metal anodes, but also seriously threatens battery safety, becoming a key bottleneck that must be overcome for solid-state battery technology to achieve large-scale commercial application.

[0004] Constructing artificial interface protective layers is one of the most widely studied strategies, the core idea of ​​which is to insert a thin, stable intermediate layer between the lithium metal anode and the sulfide electrolyte. This intermediate layer aims to achieve multiple functions: physically isolating lithium from direct contact with the electrolyte and preventing thermodynamically driven side reactions; chemically, it is itself stable for lithium or can form a kinetically stable passivation layer; functionally, it needs to ensure the rapid passage of lithium ions while blocking electron conduction. To this end, researchers have explored a wide variety of interface layer materials, including but not limited to some lithium-stable oxides (such as Li₂O, LiAlO₂), nitrides (such as Li₃N), halides (such as LiF, LiI) or their complexes, as well as gradient interface structures generated by methods such as vapor deposition, solution coating, and in-situ reactions. These methods have improved interface stability to some extent and enhanced the initial cycle performance of the battery. However, artificial interface layer strategies often face the problem of failure under long-term cycling. Under repeated volume changes and stress, brittle interface layers are prone to cracking and failure; extremely thin interface layers may not be able to completely cover the rough lithium surface, leaving defect channels; more importantly, most interface layer designs are based on the concept of "passive defense," that is, attempting to establish a perfect barrier before lithium deposition. Once lithium dendrites germinate and begin to grow under or outside the barrier due to local uneven current density, interface defects, or cyclic aging, these static, passive interface layers often lack the ability to actively "cope with" and "eliminate" the invading dendrites, and ultimately cannot escape the fate of being penetrated. Summary of the Invention

[0005] To address the problem of lithium dendrite growth in sulfide solid electrolytes in existing technologies, this invention provides a multilayer sulfide solid electrolyte structure, preparation method, and application.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a multilayer sulfide solid electrolyte structure, which is a sandwich structure comprising a first electrolyte layer, an electrolyte-S layer, and a second electrolyte layer connected in sequence. The electrolyte-S layer includes electrolyte and sulfur, and the proportion of sulfur in the electrolyte-S layer is 5wt%-25wt%. The electrolyte refers to a sulfide solid electrolyte with lithium, phosphorus, sulfur, and chlorine as the main components.

[0007] Optionally, the proportion of S in the electrolyte-S layer is 10wt%-15wt%.

[0008] Optionally, the mass ratio of the first electrolyte layer, the electrolyte-S layer, and the second electrolyte layer is 1:(3-5):1.

[0009] This invention also provides a method for preparing a multilayer sulfide solid electrolyte structure, comprising: Electrolyte powder and sulfur powder are mixed and ground for more than 0.5 hours to obtain mixed powder; First electrolyte powder, mixed powder, and second electrolyte powder are sequentially added to the mold and compacted to form a sandwich structure including a first electrolyte layer, an electrolyte-S layer, and a second electrolyte layer, thereby obtaining a multi-layer sulfide solid electrolyte structure; wherein, the proportion of S in the electrolyte-S layer is 5wt%-25wt%.

[0010] Optionally, the mold is an Al2O3 ceramic mold.

[0011] Optionally, the compaction pressure is 100-140 MPa.

[0012] Optionally, both the first electrolyte powder and the second electrolyte powder are Li 5.5 PS 4.5 Cl 1.5 Or Li6PS5Br.

[0013] A symmetrical battery includes a positive electrode, a negative electrode, and the aforementioned multilayer sulfide solid electrolyte structure, wherein the positive electrode and the negative electrode are located on opposite sides of the multilayer sulfide solid electrolyte structure, and both the positive electrode and the negative electrode are made of lithium.

[0014] A full battery includes a negative electrode, an NCM811 composite positive electrode, and the aforementioned multilayer sulfide solid electrolyte structure. The negative electrode and the composite positive electrode are located on opposite sides of the multilayer sulfide solid electrolyte structure. The negative electrode is made of lithium metal. The NCM811 composite positive electrode includes NCM811 coated with LiNbO3, LPSC, and VGCF, with a mass ratio of 70:27:3.

[0015] The above-mentioned multilayer sulfide solid electrolyte structure is used in solid-state batteries.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a multilayer sulfide solid electrolyte structure. This structure, through a sandwich-structured composite electrolyte design, combines the synergistic effect of the electrolyte layer and the electrolyte-S layer to propose a "point-defense reactive armor" dendrite protection strategy. Specifically, it utilizes an electrolyte that is relatively stable to lithium metal as the outermost layer, and a sulfur-added electrolyte-S layer as the middle layer to construct an electrolyte-electrolyte + S-electrolyte sandwich composite electrolyte. During battery cycling, due to partial reactions between the electrolyte and lithium metal, and non-uniform lithium deposition on the negative electrode side, lithium dendrites begin to grow from the lithium metal negative electrode side. After the lithium dendrites grow from the negative electrode and penetrate the first electrolyte layer, they enter the electrolyte-S layer, at which point the "point-defense reactive armor" is activated. The "A" mechanism involves the reaction of sulfur dendrite tips upon contact with sulfur due to the dispersed distribution of sulfur particles: Li + S → Li2S. The generated Li2S is a material with extremely low ionic and electronic conductivity, which can form a passivation layer. At the same time, the sulfur particles consume the active lithium at the dendrite tips, thereby passivating the dendrite tips and inhibiting further dendrite growth. This multilayer sulfide solid electrolyte structure, through the effects of "active chemical blocking," "point defense design," and multilayer synergistic reinforcement, fundamentally solves the problem of lithium dendrite growth in sulfide solid electrolytes in existing technologies. It provides a key technological breakthrough for the commercialization of sulfide all-solid-state batteries, and is especially suitable for fields with stringent safety and lifespan requirements, such as electric vehicles and energy storage.

[0017] This invention also provides a method for preparing a multilayer sulfide solid electrolyte structure. This method utilizes a step-by-step mixing and molding process to prepare an electrolyte-electrolyte + S-electrolyte sandwich structure solid electrolyte. The electrolyte and S powder are mixed and ground for at least 0.5 hours to ensure uniform sulfur particle size. Then, by sequentially layering a first electrolyte layer, a mixed powder (electrolyte-S layer), and a second electrolyte layer, the sulfur particles are confined to the intermediate layer, forming a diffusely distributed "reactive armor." This gives the prepared multilayer sulfide solid electrolyte structure highly efficient dendrite protection, fundamentally inhibiting dendrite growth and significantly improving battery life and safety. The entire preparation process requires no complex equipment or processes, has low investment and production costs, and is more suitable for low-cost, large-scale production, providing a feasible solution for the industrialization of sulfide all-solid-state batteries.

[0018] The application of the aforementioned multilayer sulfide solid electrolyte structure in solid-state batteries includes symmetrical batteries and full cells with the aforementioned multilayer sulfide solid electrolyte, which have better cycle stability, safety and rate performance, and are especially suitable for high energy density solid-state batteries, electric vehicle fast charging systems and energy storage fields. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a multilayer sulfide solid electrolyte structure according to the present invention.

[0020] Figure 2 This is a diagram illustrating the mechanism of dendrite growth suppression in a multilayer sulfide solid electrolyte structure according to the present invention; wherein, a is a dendrite growth mechanism diagram with only an electrolyte layer, b is a dendrite growth mechanism diagram with only an electrolyte-S layer, and c is a dendrite growth mechanism diagram of the sandwich structure of the multilayer sulfide solid electrolyte of the present invention.

[0021] Figure 3 The graph shows the initial coulombic efficiency comparison between the full cells Cu / LPSC-S / LCO and Cu / LPSC-SML / LCO.

[0022] Figure 4 This is a schematic diagram of the preparation method of a multilayer sulfide solid electrolyte structure according to the present invention.

[0023] Figure 5 The image shows a comparison of the electrolyte and electrolyte-S (mixed powder) prepared in Example 1 of this invention; where a is the electrolyte powder and b is the electrolyte-S powder.

[0024] Figure 6 The image shows the microstructure of the multilayer sulfide solid electrolyte prepared in Example 1 of this invention; where a is a cross-sectional SEM image of the multilayer sulfide solid electrolyte structure and b is the S element energy dispersive spectroscopy image corresponding to a.

[0025] Figure 7 The images show the corresponding CCD columnar comparison diagrams of the multilayer sulfide solid electrolyte structures prepared in Examples 1-5 and the comparative examples of this invention.

[0026] Figure 8 These are time-fixed CCD test curves comparing the multilayer sulfide solid electrolyte structures prepared in Examples 1-5 and the comparative examples of the present invention; wherein, a is the time-fixed CCD test curve of the multilayer sulfide solid electrolyte structure prepared in Comparative Example 1, b is the time-fixed CCD test curve of the multilayer sulfide solid electrolyte structure prepared in Example 1, c is the time-fixed CCD test curve of the multilayer sulfide solid electrolyte structure prepared in Example 2, d is the time-fixed CCD test curve of the multilayer sulfide solid electrolyte structure prepared in Example 3, e is the time-fixed CCD test curve of the multilayer sulfide solid electrolyte structure prepared in Example 4, and f is the time-fixed CCD test curve of the multilayer sulfide solid electrolyte structure prepared in Example 5.

[0027] Figure 9 This is a comparison curve of the multilayer sulfide solid electrolyte structure prepared in Example 3 of the present invention and the capacity-fixed CCD prepared in Comparative Example 1.

[0028] Figure 10 A symmetric battery incorporating the multilayer sulfide solid electrolyte structure prepared in Example 3 of this invention was tested at a current density of 0.5 mA cm⁻¹. -2 and 0.5 mAh cm -2 Capacity cycle stability test chart.

[0029] Figure 11 This is a comparison chart of the full-cell performance of the multilayer sulfide solid electrolyte structures prepared according to Example 3 and the comparative example of the present invention.

[0030] Wherein, 1-first electrolyte layer, 2-electrolyte-S layer, 3-second electrolyte layer. Detailed Implementation

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0033] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0035] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0038] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0039] As is well known, sulfide solid electrolytes, with their ultra-high ionic conductivity, have become a core material for constructing high-energy-density solid-state batteries. However, their thermodynamic instability with metallic lithium can trigger continuous interfacial side reactions, leading to lithium dendrite growth. These dendrites may penetrate the electrolyte and ultimately cause a short circuit. Therefore, solving the problem of lithium dendrite growth in sulfide solid electrolytes is crucial for their successful commercialization.

[0040] From the perspective of extending battery cycle life, blocking the penetration of lithium dendrites into the electrolyte is equally crucial. However, the mechanism by which lithium dendrites penetrate the electrolyte remains a significant gap in current research. The growth of lithium dendrites in solid electrolytes is a destructive penetration process, accompanied by stress release and crack propagation. Once cracks form, lithium dendrites rapidly propagate along these fracture paths, similar to the mechanism by which projectiles penetrate armor. Applying the mechanism of reactive armor systems, which control explosive reactions to defend against incoming threats, to addressing the problem of lithium dendrite growth would fundamentally solve the comprehensive problems, including battery performance and safety, caused by lithium dendrite penetration.

[0041] To achieve the above effects, the selection of additives needs to be screened, and the following two conditions must be met: first, they must be able to react with lithium dendrites; second, the products generated must be able to block further penetration of lithium dendrites (ionic insulation and electronic insulation).

[0042] Based on the above analysis, this application proposes a strategy of adding sulfur to the interlayer of an electrolyte-type sulfide solid electrolyte to solve the problem of lithium dendrite penetration while preventing direct contact between sulfur and the lithium anode. Sulfur is dispersed in particulate form within the interlayer structure. This design not only effectively prevents the formation of an insulating pure sulfur layer but also forms a sulfur-containing interlayer. When lithium dendrites grow into the interlayer structure, their tips come into contact with sulfur and generate lithium sulfide. This reaction passivates the dendrite tips, thereby inhibiting further dendrite growth. The sulfur-containing layer, as a functional layer, effectively blocks lithium dendrite penetration, significantly extending the battery's lifespan. The specific solution is as follows: See Figure 1 This invention provides a multilayer sulfide solid electrolyte structure, which is a sandwich structure comprising a first electrolyte layer 1, an electrolyte-S layer 2, and a second electrolyte layer 3 connected sequentially. The electrolyte-S layer 2 contains electrolyte and sulfur (S), with the S content in the electrolyte-S layer 2 ranging from 5 wt% to 25 wt%. Preferably, the mass ratio of the first electrolyte layer 1, the electrolyte-S layer 2, and the second electrolyte layer 3 is 1:(3-5):1.

[0043] See Figure 2 , Figure 2 In case a, pure electrolyte, due to its low critical current density, cannot effectively suppress the penetration process of lithium dendrites. Lithium dendrites will grow from the negative electrode side, disrupting the interface between the electrolyte and the lithium negative electrode, and eventually penetrating the entire battery, causing a short circuit. For example... Figure 2 As shown in b, the entire sulfur-containing layer is uniformly added to the entire electrolyte, i.e., no sandwich structure design is used. Although the lithium dendrites penetrating into the electrolyte react with sulfur, and the penetration process is blocked, the active sulfur particles will directly contact the metallic lithium near the lithium metal anode. This direct contact between sulfur and lithium will inevitably lead to the loss of active lithium and the damage to the anode interface layer, causing instability in the overall battery structure (see details). Figure 3 (Comparison of coulombic efficiency of lithium-free anode batteries). In the traditional lithium battery field, sulfur is usually used as a positive electrode material. In this design, sulfur is added to the solid electrolyte for the first time to suppress the growth of lithium dendrites. This is one of the material advantages of this design. To solve the problem of sulfur corroding the lithium anode, we adopted a sandwich structure design, that is, using an electrolyte that is relatively stable to lithium metal as the outermost layer, and using a sulfur-added electrolyte-S layer as the middle layer to construct an electrolyte-electrolyte + S-electrolyte sandwich composite electrolyte, which is called the electrolyte-SML design. Figure 2As shown in Figure c, during battery cycling, due to partial reactions between the electrolyte and lithium metal, as well as the non-uniform deposition of lithium on the negative electrode side, lithium dendrites begin to grow from the lithium metal negative electrode side and quickly penetrate the outermost layer of the electrolyte into the sulfur-containing electrolyte-S intermediate layer. This process is dominated by lithium dendrite penetration of the electrolyte layer. The penetration and growth of lithium dendrites in the electrolyte intermediate layer is an electrochemically driven process, with a very high local current density at the tip of the lithium dendrite. When the tip of the lithium dendrite encounters sulfur particles in the electrolyte-S, the active sulfur particles and the newly grown lithium dendrite react: Li + S → Li₂S. Lithium sulfide is a material with extremely low ionic and electronic conductivity, and the growth of lithium dendrites depends on the ionic and electronic conductivity characteristics of the surrounding materials. Therefore, the formation of lithium sulfide effectively blocks the continuous growth of lithium dendrites. In this way, the penetration process of lithium dendrites through the sulfur-containing interlayer is blocked, preventing them from extending further. This resolves the short-circuit problem caused by lithium dendrite growth. The electrolyte-S layer 2 acts like reactive armor, perfectly blocking the penetration process of lithium dendrites. We call this design a "point-defense reactive armor" dendrite protection strategy. Point defense refers to the fact that sulfur is dispersed in the electrolyte interlayer in the form of particles, thus maintaining the electrolyte's excellent ionic conductivity.

[0044] See Figure 3 To further demonstrate the advantages of the sandwich structure combined with S doping in the intermediate layer, a first comparison of coulombic efficiency was conducted on lithium-free full cells assembled under the same conditions. The results showed that both the first and second electrolyte layers were LPSC (Li-2000 LPSC). 5.5 PS 4.5 Cl 1.5 For example (in the figure, LPSC represents the electrolyte as Li). 5.5 PS 4.5 Cl 1.5 LPSC-S represents a full cell with a pure LPSC-S layer electrolyte, Cu / LPSC-S / LCO; LPSC-SML represents a full cell with a multilayer sulfide solid electrolyte structure of the sandwich structure of this invention, Cu / LPSC-SML / LCO), further demonstrating the excellent performance of the structure of this invention.

[0045] See Figure 4 The present invention also provides a method for preparing a multilayer sulfide solid electrolyte structure, comprising: S1: Mix and grind the electrolyte powder and S powder for more than 0.5 hours to obtain a mixed powder; S2: First electrolyte powder, mixed powder, and second electrolyte powder are sequentially added to the mold and compacted to form a sandwich structure including a first electrolyte layer 1, an electrolyte-S layer 2, and a second electrolyte layer 3, resulting in a multilayer sulfide solid electrolyte structure; wherein, the S content in the electrolyte-S layer 2 is 5wt%-25wt%; the mold is an Al2O3 ceramic mold; the compaction pressure is 100-140 MPa. Both the first and second electrolyte powders are Li. 5.5 PS 4.5 Cl 1.5 Or Li6PS5Br.

[0046] The present invention provides a symmetrical battery, including a positive electrode, a negative electrode and the above-mentioned multilayer sulfide solid electrolyte structure, wherein the positive electrode and the negative electrode are located on both sides of the multilayer sulfide solid electrolyte structure, and both the positive electrode and the negative electrode are made of lithium.

[0047] A full battery includes a negative electrode, an NCM811 composite positive electrode, and the aforementioned multilayer sulfide solid electrolyte structure. The negative electrode and the composite positive electrode are located on opposite sides of the multilayer sulfide solid electrolyte structure. The negative electrode is made of lithium metal. The NCM811 composite positive electrode includes NCM811 coated with LiNbO3, LPSC, and VGCF, with a mass ratio of 70:27:3.

[0048] The aforementioned multilayer sulfide solid electrolytes are used in solid-state batteries. Solid-state batteries with the aforementioned multilayer sulfide solid electrolyte structure have better cycle stability, safety and rate performance, and are especially suitable for high energy density solid-state batteries, electric vehicle fast charging systems and energy storage fields.

[0049] Example 1 Electrolyte powder (Li) 5.5 PS 4.5 Cl 1.5 The electrolyte-S was manually mixed with S powder and ground for 1 hour to obtain a mixed powder (electrolyte-S) (see [link]). Figure 5 (See diagram for comparison of mixed powder and electrolyte powder). 20 mg of electrolyte powder, 80 mg of mixed powder (electrolyte-S), and 20 mg of electrolyte powder were sequentially placed into a 10 mm diameter Al₂O₃ ceramic mold and compacted to obtain a multilayer sulfide solid electrolyte structure, denoted as LPSC-SML. The S content in the mixed powder was 5 wt%. During powder spreading, before adding the next batch of powder, the powder inside the mold was ensured to be intact. Subsequently, stainless steel electrode posts were placed at the top and bottom of the mold, and the multilayer sulfide solid electrolyte structure (LPSC-SML) was formed under a pressure of 120 MPa.

[0050] See Figure 6 SEM testing and energy dispersive spectroscopy analysis were performed on the multilayer sulfide solid electrolyte structure prepared in this embodiment, and it was found that a multilayer sulfide solid electrolyte structure with a sulfur-containing sandwich structure in the middle layer was successfully prepared.

[0051] Example 2 Unlike Example 1, the proportion of S in the mixed powder is 10 wt%.

[0052] Example 3 Unlike Example 1, the proportion of S in the mixed powder is 15 wt%.

[0053] Example 4 Unlike Example 1, the proportion of S in the mixed powder is 20 wt%.

[0054] Example 5 Unlike Example 1, the proportion of S in the mixed powder is 25 wt%.

[0055] Comparative Example Unlike Example 1, the S content in the mixed powder is 0 wt%, denoted as LPSC.

[0056] See Figure 7 CCD comparison tests were performed on the multilayer sulfide solid electrolyte structures prepared in Examples 1-5 and the comparative example. The results showed that the CCD value of the multilayer sulfide solid electrolyte structure prepared in the comparative example was 2.0 mA cm⁻¹. -2 In Examples 1-5, the CCD values ​​were significantly improved due to the addition of the intermediate layer S. In Example 3, the optimal addition amount of S was 15wt%.

[0057] See Figure 8 The time-fixed CCD test curves of the multilayer sulfide solid electrolyte structures prepared in Examples 1-5 and the comparative examples of this invention further confirm that the optimal sulfur addition amount is 15 wt%, which is used for the subsequent preparation of LPSC-SML electrolytes. (The last sentence appears to be incomplete and possibly refers to a different topic.) -2 In the fixed lithium deposition test, the LPSC-SML prepared in this embodiment of the invention achieved 26.5 mA cm⁻¹. -2 The high CCD, while the LPSC in the comparative model barely reached 7.0 mA cm⁻¹. -2 .Replenish Figure 9The comparison of cycle life and corresponding current density for various electrolyte optimization strategies is shown, further demonstrating the significant effect of the multilayer sulfide solid electrolyte structure prepared in the embodiments of the present invention in enhancing the long-term cycle stability of sulfide solid batteries. The LPSC-SML electrolyte prepared in this invention exhibits excellent performance, reaching up to 26.5 mA cm⁻¹ in CCD testing. -2 It features a high-performance CCD sensor and a cumulative capacity of 105mAh.

[0058] To further determine the role of sulfur addition in improving long-term cycling stability, Li / LPSC / Li and Li / LPSC-SML / Li symmetric cells were assembled and tested at room temperature at 0.5 mA cm⁻¹. -2 The current density and 0.5 mAh cm⁻¹ -2 The capacity was subjected to cyclic testing. See the results below. Figure 10 The Li / LPSC-SML / Li cell achieved a long stable cycling duration of 4200 h, while the Li / LPSC / Li cell only achieved 210 h. The Li / LPSC-SML / Li symmetric cell was also assembled for use at higher current densities, achieving stable cycling at 0.5 mA cm⁻¹ at room temperature. 2 and 0.5 mAh cm 2 Stable cycling for over 5200 hours was achieved.

[0059] All-solid-state lithium batteries (ASSLBs) with Li as the negative electrode and LiNbO3-coated NCM811 as the cathode were assembled using the LPSC prepared in the comparative example and the LPSC-SML electrolyte prepared in Example 3. The batteries were tested at 3C (5.60 mA cm⁻¹). -2 The battery's cycle performance was tested at a rate of [missing information], and the results were [missing information]. Figure 11 As shown, the Li / electrolyte-SML / LNO@811 battery (representing a full cell comprising a negative electrode, an NCM811 composite positive electrode, and the multilayer sulfide solid electrolyte structure prepared in Example 3) can stably cycle for over 400 cycles. In contrast, the Li / LPSC / LNO@811 battery has a cycle life of less than 200 cycles due to a soft short circuit and a significant decrease in coulombic efficiency. These results strongly demonstrate the effectiveness of sulfur addition, and these data powerfully indicate that adding sulfur to the intermediate layer of a solid sulfide electrolyte can effectively suppress lithium dendrite growth, thereby improving the performance of the corresponding battery.

[0060] Example 6 Unlike Example 1, the mass ratio of the first electrolyte layer 1, the electrolyte-S layer 2, and the second electrolyte layer (3) is 1:3:1.

[0061] Example 7 Unlike Example 1, the mass ratio of the first electrolyte layer 1, the electrolyte-S layer 2, and the second electrolyte layer (3) is 1:5:1.

[0062] Example 8 Unlike Example 1, the compaction pressure was 100 MPa.

[0063] Example 9 Unlike Example 1, the compaction pressure was 130 MPa.

[0064] Example 10 Unlike Example 1, the compaction pressure was 140 MPa.

[0065] Example 11 Unlike Example 1, the electrolyte powder used was Li6PS5Br.

[0066] The above description is merely a preferred embodiment of the present invention (in fact, in addition to elemental sulfur, other elements (such as Se, I2, P, etc.) or compounds that can react with lithium metal to form ionic conductor compounds may also have the effect of inhibiting lithium dendrite growth, improving battery cycle performance and critical current density when mixed into electrolyte powder in powder form as an intermediate layer). It is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A multilayer sulfide solid electrolyte structure, characterized in that, The multilayer sulfide solid electrolyte structure is a sandwich structure, including a first electrolyte layer (1), an electrolyte-S layer (2), and a second electrolyte layer (3) connected in sequence. The electrolyte-S layer (2) includes electrolyte and S, and the proportion of S in the electrolyte-S layer (2) is 5wt%-25wt%.

2. The multilayer sulfide solid electrolyte structure according to claim 1, characterized in that, The S content in the electrolyte-S layer (2) is 10wt%-15wt%.

3. The multilayer sulfide solid electrolyte structure according to claim 1, characterized in that, The mass ratio of the first electrolyte layer (1), the electrolyte-S layer (2), and the second electrolyte layer (3) is 1:(3-5):

1.

4. A method for preparing a multilayer sulfide solid electrolyte structure, characterized in that, include: Electrolyte powder and sulfur powder are mixed and ground for more than 0.5 hours to obtain mixed powder; First electrolyte powder, mixed powder and second electrolyte powder are added to the mold in sequence and compacted to form a sandwich structure including first electrolyte layer (1), electrolyte-S layer (2) and second electrolyte layer (3) to obtain a multi-layer sulfide solid electrolyte structure; wherein, the proportion of S in the electrolyte-S layer (2) is 5wt%-25wt%.

5. The method for preparing a multilayer sulfide solid electrolyte structure according to claim 4, characterized in that, The mold is an Al2O3 ceramic mold.

6. The method for preparing a multilayer sulfide solid electrolyte structure according to claim 4, characterized in that, The compaction pressure is 100-140 MPa.

7. The method for preparing a multilayer sulfide solid electrolyte structure according to claim 4, characterized in that, Both the first electrolyte powder and the second electrolyte powder are Li 5.5 PS 4.5 Cl 1.5 Or Li6PS5Br.

8. A symmetrical battery, characterized in that, The invention includes a positive electrode, a negative electrode, and a multilayer sulfide solid electrolyte structure as described in any one of claims 1-3, wherein the positive electrode and the negative electrode are located on opposite sides of the multilayer sulfide solid electrolyte structure, and both the positive electrode and the negative electrode are made of lithium.

9. A full battery, characterized in that, The device includes a negative electrode, an NCM811 composite positive electrode, and a multilayer sulfide solid electrolyte structure as described in any one of claims 1-3. The negative electrode and the composite positive electrode are located on opposite sides of the multilayer sulfide solid electrolyte structure, and the negative electrode is made of lithium metal. The 811 composite positive electrode includes NCM811 coated with LiNbO3, LPSC, and VGCF, and the mass ratio of LiNbO3 coated NCM811, LPSC, and VGCF is 70:27:

3.

10. The application of the multilayer sulfide solid electrolyte structure according to any one of claims 1-3 in solid-state batteries.

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