Selenide solid electrolyte, preparation method and solid-state battery

Abstract

The invention relates to a selenide solid-state electrolyte, a preparation method and a solid-state battery, the chemical general formula of the selenide solid-state electrolyte is Li7-yPSe6-yXy, 0 < = y < = 1.6, and X comprises at least one of Cl, Br, I and F. According to the selenide solid electrolyte disclosed by the invention, sulfur is completely replaced by selenium to obtain a higher ion migration channel, and the ionic conductivity of the prepared selenide solid electrolyte at room temperature is remarkably improved through the optimization effect of partial doping of bromine on the lithium vacancy concentration. After being exposed in a low-dew-point environment for a long time, the ionic conductivity attenuation rate is extremely low, the retention rate is high, the requirement on the production environment is greatly reduced, and the production cost is reduced.

Description

Technical Field

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

[0002] In recent years, all-solid-state batteries have been regarded as the ideal choice for next-generation lithium batteries due to their high safety and high energy density. Among them, the sulfide solid electrolyte Li6PS5X system has attracted widespread attention due to its extremely high ionic conductivity and good mechanical properties.

[0003] However, the Li6PS5Cl electrolyte exhibits insufficient oxidative stability to high-voltage cathode materials. When in direct contact with these materials, side reactions occur at the interface, leading to increased interfacial impedance and capacity decay. Furthermore, it is extremely sensitive to humidity; exposure to air causes rapid reaction with moisture, resulting in electrolyte structural damage and a sharp decrease in ionic conductivity. This places stringent requirements on production environment control, such as glove boxes, and increases manufacturing costs.

[0004] Based on the aforementioned shortcomings, researchers have attempted various methods such as elemental doping and interface modification, but with limited effectiveness or complex processes. Therefore, developing a novel solid-state electrolyte that combines high ionic conductivity, excellent atmospheric stability, and a wide electrochemical window, along with a simple and low-cost preparation process, has become a pressing technical challenge in this field. Summary of the Invention

[0005] To address the problems of poor interfacial stability, low environmental tolerance, complex improvement processes, and difficulty in achieving a comprehensive performance balance of high ionic conductivity, excellent atmospheric stability, and a wide electrochemical window in existing sulfide solid electrolytes.

[0006] On one hand, this application provides a selenide solid electrolyte, wherein the general chemical formula of the selenide solid electrolyte is Li. 7-y PSe 6-y X y Where 0≤y≤1.6, and X includes at least one of Cl, Br, I, and F.

[0007] In a possible implementation, X contains at least Br.

[0008] In a possible implementation, when y = 1.1 and X is Br in the general chemical formula, the selenide solid electrolyte is Li. 5.9 PSe 4.9 Br 1. 1.

[0009] On the other hand, this application also provides a method for preparing a selenide solid electrolyte, which includes the following steps: Under an inert atmosphere, according to the stated chemical formula Li 7-y PSe 6-y X y Lithium source, phosphorus source, selenium source and halogen source X were weighed as raw materials according to the stoichiometric ratio; The raw materials are added to a grinder and mixed to obtain an initial mixed precursor. The initial mixed precursor was placed in a muffle furnace under an inert atmosphere, and after heating and holding for calcination, it was cooled to room temperature with the furnace to obtain an electrolyte block. The electrolyte block is crushed and sieved to obtain the selenide solid electrolyte. In a possible implementation, the lithium source is at least one of LiH, Li2CO3, LiCl, LiBr, LiI, LiF, Li2S, Li2Se, and Li.

[0010] In a possible implementation, the phosphorus source is P2S5 or P4S. 10 At least one of P4S3 and P.

[0011] In a possible implementation, the selenium source is Se and / or Li2Se.

[0012] In a possible implementation, the grinding time of the grinder is 10s-60s, and the number of grinding cycles is 5-20.

[0013] In a possible implementation, the heating rate is 1-5℃ / min, the holding and calcining temperature is 200℃-650℃, and the holding time is 10-40h.

[0014] On the other hand, this application also provides a solid-state battery, including the selenide solid electrolyte.

[0015] Implementing the embodiments of this application has the following beneficial effects: The selenide solid electrolyte of this application obtains a higher ion migration channel by completely replacing sulfur with selenium, and the ionic conductivity of the prepared selenide solid electrolyte is significantly improved at room temperature by optimizing the lithium vacancy concentration through partial bromine doping.

[0016] The selenide electrolyte of this application exhibits extremely low ionic conductivity decay rate and a retention rate of over 90% after prolonged exposure in a low dew point environment, which greatly reduces the requirements for the production environment and helps to reduce production costs.

[0017] The solid-phase reaction method used in this application combines a high-energy pulverizer and a common muffle furnace. The process is simple, the equipment requirements are low, the raw materials are readily available and the cost is low, making it very suitable for large-scale industrial production and possessing extremely high commercial conversion value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0019] Figure 1 This is a flowchart of a method for preparing a selenide solid electrolyte according to an embodiment of this application; Figure 2 This is the XRD pattern of the solid electrolyte prepared in Example 12 of this application; Figure 3 This is the XRD pattern of the electrolyte prepared in Comparative Example 1 after heat treatment in the embodiments of this application; Figure 4 This is a comparison diagram of the ionic conductivity of Example 12 and Comparative Example 1 in the embodiments of this application; Figure 5 This is a comparison chart of the retention rate of ionic conductivity of Example 12 and Comparative Example 1 after exposure to the atmosphere in this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] For the terms defined below, unless a different definition is given elsewhere in the claims or this specification, these definitions shall apply. All numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about." The term "about" generally refers to a range of numerical values ​​that a person skilled in the art would consider equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A range of numerical values ​​indicated by a low value and a high value is defined as including all numerical values ​​included within that range and all subranges included within that range.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0023] This application provides a selenide solid electrolyte, the chemical formula of which is Li. 7- y PSe 6-y X y Where 0 ≤ y ≤ 1.6, and X includes at least one of Cl, Br, I, and F. This electrolyte completely replaces sulfur (S) in traditional sulfide electrolytes with selenium (Se). Selenium has a larger atomic radius than sulfur, resulting in a weaker and more easily polarized P-Se bond compared to a PS bond, which facilitates lithium-ion migration and improves ionic conductivity. Simultaneously, selenium has significantly lower hygroscopicity than sulfur, fundamentally enhancing the material's atmospheric stability.

[0024] In one possible implementation, the halogen source X contains at least Br. By partially substituting selenium (Se) sites with bromine (Br), the electronegativity of bromine is significantly lower than that of selenium. When bromine is introduced into the selenide lattice, it alters the local charge distribution, weakens the electrostatic interaction with lithium ions, and thus effectively lowers the energy barrier for lithium ion migration, creating a more favorable environment for rapid lithium ion transport. Bromine doping can further optimize the spatial distribution and site order of halogen sites in the crystal structure. This optimization not only increases the number of vacancies available for lithium ions to occupy in the crystal structure—the lithium vacancy concentration—directly providing more pathways for ion migration, but also helps to form more continuous and spacious ion migration channels. From a thermodynamic perspective, the introduction of bromine can also moderately adjust the highest occupied molecular orbital energy level of the electrolyte, making it more negative. This means that the electrolyte's own antioxidant capacity is enhanced, and its interfacial stability when in contact with high-voltage cathode materials, such as lithium cobalt oxide and high-nickel ternary materials, is improved. This significantly broadens the electrochemical stability window of the material, enabling it to be adapted to battery systems with higher operating voltages, and laying a key material foundation for improving the energy density of all-solid-state batteries.

[0025] In a preferred embodiment, when y = 1.1 and X is Br in the general chemical formula, the solid electrolyte is Li. 5.9 PSe 4.9 Br 1.1The electrolyte crystal structure belongs to the sulfide-germanium type. By completely replacing sulfur with selenium, which has a larger atomic radius, weaker and more easily polarized P-Se bonds are formed, which is beneficial for lithium ion migration and lays the foundation for improving ionic conductivity. At the same time, partial doping with bromine introduces halogen atoms with lower electronegativity, which can further optimize the distribution of halogen sites in the crystal structure, increase the lithium vacancy concentration, thereby significantly improving ionic conductivity and broadening the electrochemical stability window of the material.

[0026] This application also provides a method for preparing a selenide solid electrolyte, used to prepare the selenide solid electrolyte. This specification provides method operation steps as shown in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operation steps may be included. The order of steps listed in the embodiments is merely one possible order of execution among many steps and does not represent the only possible order. In actual execution of the preparation method, it can be performed in the order shown in the embodiments or drawings or in parallel. The preparation method may include S10-S40: S10, under an inert atmosphere, according to the stated chemical formula Li 7-y PSe 6-y X y Lithium source, phosphorus source, selenium source and halogen source X were weighed as raw materials according to the stoichiometric ratio; S20, the raw materials are added to a grinder for mixing to obtain an initial mixed precursor; S30, the initial mixed precursor is placed in a muffle furnace under an inert atmosphere, and after heating and holding for calcination, it is cooled to room temperature with the furnace to obtain an electrolyte block; S40, the electrolyte block is crushed and sieved to obtain the selenide solid electrolyte. The raw materials required to prepare the above-mentioned selenide solid electrolyte include lithium source, phosphorus source, selenium source and halogen source.

[0027] The lithium source can be at least one of LiH, Li₂CO₃, LiCl, LiBr, LiI, LiF, Li₂S, Li₂Se, and Li. High-purity lithium salts, such as Li₂S or LiBr, are preferred to precisely control the stoichiometry. These compounds are advantageous not only because their high purity helps in precisely controlling the overall stoichiometry and reducing the introduction of impurities, thus ensuring the regularity of the final product's crystal structure and electrochemical purity; but also because some of their components, such as S and Br, are themselves constituent elements of the target product, simplifying the raw material system and facilitating a more uniform solid-phase reaction during subsequent heat treatment, forming a homogeneous sulfogermanium-germanium ore-type structure.

[0028] Phosphorus sources can be P2S5 and P4S. 10At least one of P4S3 and P. P is preferred because its reaction pathway with selenium (Se) and lithium source is more direct and the stoichiometric relationship is clear. This can effectively avoid the interference of additional sulfur elements introduced when using compounds such as P2S5 on the target selenide system, and is conducive to obtaining a final product with higher phase purity.

[0029] The selenium source can be Se and / or Li₂Se. Using Li₂Se can provide both selenium and lithium, achieving an integrated supply of both. This not only simplifies the raw material weighing and mixing process and reduces the risk of uneven mixing of multiple raw materials, but more importantly, it helps to promote the uniform distribution of lithium and selenium at the atomic scale, laying a solid foundation for the formation of a highly ordered target crystal phase.

[0030] The halogen source X can be at least one of LiCl, LiBr, LiI, I, and LiF. When X is Br, LiBr is preferred as the halogen source to avoid introducing other cationic impurities. It has a suitable thermal decomposition temperature and reactivity, and can fully react with other raw materials under the set heat treatment process to achieve effective doping of bromine at selenium sites.

[0031] In step S20, the weighed raw materials are added to a pulverizer, such as a high-energy pulverizer, for mechanical mixing. The process parameters of the pulverizer have a significant impact on the uniformity of the precursor.

[0032] In possible implementations, the single grinding time is controlled between 10s and 60s. Understandably, the single grinding time can be any value within the range of 10s to 60s. For example, the single grinding time can be set to 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, etc. In some implementations, 15s to 30s is preferred. Within this preferred range, sufficient energy input is ensured for each grinding operation to achieve effective shearing and diffusion mixing of the powder, while avoiding negative effects caused by excessively prolonged continuous mechanical action.

[0033] In possible implementations, the number of grinding cycles is 5-20. Understandably, the number of grinding cycles can be any value within the range of 5-20. Exemplarily, the number of grinding cycles can be set to 5, 6, 8, 10, 12, 14, 16, 18, or 20. In some implementations, 6-12 cycles are preferred. By controlling the grinding parameters, it is ensured that the raw material powders are fully and uniformly mixed to obtain an initially mixed precursor with accurate stoichiometry.

[0034] In step S30, the uniformly mixed precursor powder is placed into a suitable crucible, such as an alumina crucible, and then transferred to a muffle furnace under an inert atmosphere for high-temperature sintering, i.e., heat preservation calcination. The core of the sintering process lies in the precise control of the heating program, which mainly includes three key parameters: heating rate, heat preservation calcination temperature, and heat preservation time.

[0035] The heating rate is controlled between 1°C / min and 5°C / min. Understandably, the heating rate can be any value within the range of 1°C / min to 5°C / min. For example, the heating rate can be set to 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, 5°C / min, etc. In some preferred embodiments, the heating rate is preferably between 1°C / min and 3°C / min. Within this preferred range, a relatively slow heating rate is beneficial for the sufficient diffusion and orderly arrangement of atoms among the components in the reaction system, avoiding local overheating, component segregation, or the formation of amorphous phases due to excessively rapid heating, thereby contributing to the formation of a target product with good crystallinity and high phase purity. A gentle heating rate also facilitates the gradual escape of any small amount of gaseous byproducts that may be generated during the reaction, reducing adverse effects on the microstructure of the final product.

[0036] The holding and calcining temperature is set between 200℃ and 650℃. Understandably, the holding and calcining temperature can be any value within the range of 200℃ to 650℃. For example, the holding and calcining temperature can be set to 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, etc. In some preferred embodiments, the holding and calcining temperature is preferably between 450℃ and 600℃. If the temperature is too low, such as below 450℃, the solid-phase reaction may be incomplete, and the precursor may not be fully converted into the thermodynamically stable target crystalline phase. Unreacted raw materials or intermediate phases may remain in the product, resulting in low ionic conductivity. If the temperature is too high, such as above 600℃ or even close to 650℃, excessive volatilization of selenium (Se) may occur, disrupting the designed stoichiometry. It may also lead to abnormal grain growth or local melting, which in turn reduces the sintering activity and densification ability of the material, negatively impacting the ionic conductivity and mechanical properties of the final electrolyte. Within the preferred temperature range of 450℃-600℃, the precursor can be ensured to fully react and generate a silver-germanium sulfide main phase with high ionic conductivity, while effectively suppressing the occurrence of harmful side reactions.

[0037] The holding time is controlled between 10h and 40h. Understandably, the holding time can be any value within the range of 10h to 40h. For example, the holding time can be set to 10h, 15h, 20h, 25h, 30h, 35h, 40h, etc. In some preferred embodiments, the holding time is preferably 15h-30h. The holding stage is a critical period for crystal nucleation and growth. A sufficiently long holding time ensures that atoms have ample time for long-range diffusion and rearrangement, thereby forming a target crystal structure with few lattice defects, complete crystallization, and clear grain boundaries. If the time is too short, the reaction and crystallization may be insufficient; if the time is too long, it is uneconomical in terms of energy consumption and production efficiency, and may lead to excessive grain coarsening.

[0038] After the holding period, the heating power to the muffle furnace is cut off, allowing the furnace chamber and the sample to cool naturally to room temperature. Once the furnace temperature has dropped to room temperature, the crucible is removed under an inert atmosphere, yielding a dense, blocky selenide solid electrolyte mass. This high-temperature sintering process is a crucial step in forming the target crystalline phase.

[0039] In step S40, the obtained electrolyte block is removed from the muffle furnace, manually ground into powder using a mortar and pestle, and then sieved to obtain the final desired selenide solid electrolyte powder. The purpose of manual grinding is to fully deagglomerate the dense sintered block, breaking down its internal grain boundary bonds, thereby obtaining fine-particle powder with high specific surface area and good flowability. After grinding, the obtained electrolyte powder needs to be sieved to remove any large, insufficiently ground particle agglomerates, ensuring that the final product has a uniform and acceptable particle size distribution. Sieving effectively improves the consistency between powder batches and removes excessively large particles that may affect battery performance. In a preferred embodiment, a 60-mesh standard sieve is preferably used for sieving.

[0040] The preparation method described in this application combines a high-energy pulverizer with muffle furnace calcination for the preparation of this selenide electrolyte. Compared with the ball mill-dedicated sintering furnace process commonly used for traditional sulfide electrolytes, this method is simpler, has lower equipment costs, and allows for large-scale production, demonstrating significant process innovation and high commercialization value.

[0041] This application also provides a solid-state battery, including the aforementioned selenide solid electrolyte. Specifically, the solid-state battery typically includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive and negative electrodes. The solid electrolyte layer is composed of the chemical formula Li as described in this application. 7-y PSe 6-y X yIt is composed of a selenide solid electrolyte. The electrolyte layer can be a dense membrane layer formed by pressing the selenide solid electrolyte powder, or it can be a composite electrode layer formed by combining it with a positive electrode active material or a negative electrode active material.

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in detail below with reference to the specific embodiments and comparative examples in Table 1.

[0043] Example 1 According to the general chemical formula Li 7-y PSe 6-y X y Given y = 1.1 and X as the stoichiometric ratio of Br, 20.50 g of Li₂Se (99.9% purity), 2.85 g of phosphorus P (99% purity), 18.16 g of selenium Se (99% purity), and 8.78 g of LiBr (99.5% purity) were weighed as raw materials in a nitrogen glove box and placed into a pulverizer. The mixed raw materials were pulverized 6 times in the pulverizer at 15-second intervals to obtain a uniformly mixed Li₂Se. 5.9 PSe 4.9 Br 1.1 Initial mixed precursor. This initial mixed precursor powder was placed in a crucible and placed in an inert atmosphere muffle furnace. It was heated to 500°C at a heating rate of 2°C / min and held at this temperature for 10 hours, then cooled to room temperature with the furnace. The resulting electrolyte block was removed from the muffle furnace, manually ground into a fine powder in a mortar, and sieved to obtain the selenide solid electrolyte sample of this embodiment, designated as Example 1.

[0044] Example 2 The difference between this embodiment and Embodiment 1 is that the number of grinding cycles in step S20 (mechanical mixing) is adjusted to 9 times; the remaining steps and parameters are exactly the same as in Embodiment 1. The electrolyte sample prepared is designated as Embodiment 2.

[0045] Example 3 The difference between this embodiment and Embodiment 2 is that in step S20, the single grinding time is adjusted to 30 seconds, while the remaining steps and parameters are exactly the same as in Embodiment 2. The electrolyte sample prepared is designated as Embodiment 3.

[0046] Example 4 In a nitrogen glove box, the following raw materials were weighed according to the same stoichiometric ratio as in Example 1: 20.50 g Li₂Se (99.9% purity), 2.85 g P (99% purity), 18.16 g Selenium (99% purity), and 8.78 g LiBr (99.5% purity). The mixed raw materials were placed in a grinder and ground 9 times at 30-second intervals to obtain Li₂.5.9 PSe 4.9 Br 1.1 Initial mixed precursor. The initial mixed precursor was placed in a crucible and heated to 450°C in an inert atmosphere muffle furnace at a heating rate of 2°C / min, held for 10 hours, and then cooled to room temperature with the furnace. The resulting electrolyte block was removed from the muffle furnace, manually ground into a fine powder in a mortar, and sieved. The prepared electrolyte sample was designated as Example 4.

[0047] Example 5 The difference between this embodiment and Embodiment 4 is that the set calcination temperature was adjusted to 550℃, while the remaining steps and parameters are exactly the same as in Embodiment 4. The electrolyte sample prepared is designated as Embodiment 5.

[0048] Example 6 The difference between this embodiment and Embodiment 4 is that the set calcination temperature is adjusted to 600℃, while the remaining steps and parameters are exactly the same as in Embodiment 4. The electrolyte sample prepared is designated as Embodiment 6.

[0049] Example 7 The difference between this embodiment and Embodiment 4 is that the set calcination temperature was adjusted to 650℃, while the remaining steps and parameters are exactly the same as in Embodiment 4. The electrolyte sample prepared is designated as Embodiment 7.

[0050] Example 8 In a nitrogen glove box, the following raw materials were weighed according to the same stoichiometric ratio as in Example 1: 20.50 g Li₂Se (99.9% purity), 2.85 g P (99% purity), 18.16 g Selenium (99% purity), and 8.78 g LiBr (99.5% purity). The mixed raw materials were placed in a grinder and ground 9 times at 30-second intervals to obtain Li₂. 5.9 PSe 4.9 Br 1.1 Initial mixed precursor. The initial mixed precursor was placed in a crucible and heated to 600°C in an inert atmosphere muffle furnace at a heating rate of 2°C / min, held for 8 hours, and then cooled to room temperature with the furnace. The resulting electrolyte block was removed from the muffle furnace, manually ground into a fine powder in a mortar, and sieved. The prepared electrolyte sample was recorded as Example 8.

[0051] Example 9 The difference between this embodiment and Embodiment 8 is that the holding time for calcination is adjusted to 15 hours, while the remaining steps and parameters are exactly the same as in Embodiment 8. The electrolyte sample prepared is designated as Embodiment 9.

[0052] Example 10 The difference between this embodiment and Embodiment 8 is that the holding time for calcination is adjusted to 20 hours, while the remaining steps and parameters are exactly the same as in Embodiment 8. The electrolyte sample prepared is designated as Embodiment 10.

[0053] Example 11 In a nitrogen glove box, the following raw materials were weighed according to the same stoichiometric ratio as in Example 1: 20.50 g Li₂Se (99.9% purity), 2.85 g P (99% purity), 18.16 g Selenium (99% purity), and 8.78 g LiBr (99.5% purity). The mixed raw materials were placed in a grinder and ground 9 times at 30-second intervals to obtain Li₂. 5.9 PSe 4.9 Br 1.1 Initial mixed precursor. The initial mixed precursor was placed in a crucible and heated to 600°C in an inert atmosphere muffle furnace at a heating rate of 1°C / min, held for 15 hours, and then cooled to room temperature with the furnace. The resulting electrolyte block was removed from the muffle furnace, manually ground into a fine powder in a mortar, and sieved. The prepared electrolyte sample was designated as Example 11.

[0054] Example 12 The difference between this embodiment and Example 11 is that the heating rate is adjusted to 3°C / minute, while the remaining steps and parameters are exactly the same as in Example 11. The electrolyte sample prepared is designated as Example 12.

[0055] Comparative Example 1 For comparison, a conventional Li6PS5C was prepared. 1.0 Sulfide electrolyte. In a nitrogen glove box, according to Li6PS5C... 1.0 According to the stoichiometric ratio, 22.17 g of Li₂S (99.9% purity), 21.64 g of P₂S₅ (99% purity), and 8.21 g of LiCl (99.5%) were weighed and placed in a 500 ml zirconium oxide ball mill jar. Zirconia grinding balls with a diameter of φ10 mm were added to the mixture at a ball-to-material ratio of 10:1. After sealing, the mixture was removed from the glove box. The ball mill jar was placed on a planetary ball mill and milled at 300 rpm for 1 hour, then at 500 rpm for 10 hours. During this period, the ball mill jar was moved back to the glove box every hour for mixing to ensure uniformity, yielding Li₆PS₅C. 1.0 The initial mixed precursor was placed in a quartz crucible and heated to 540°C at a heating rate of 1°C / min under a nitrogen atmosphere. After holding at this temperature for 10 hours, the mixture was cooled in the furnace to obtain Li6PS5C (Comparative Example 1). 1.0 Solid electrolyte sample.

[0056] Characterization and performance testing The phase structure and electrochemical performance of the solid electrolytes prepared in Examples 1-12 and Comparative Example 1 were tested.

[0057] X-ray diffraction (XRD) analysis The crystal structure of the obtained electrolyte was characterized using X-ray diffraction. Figure 2 The image shows the XRD pattern of the Li5.9PSe4.9Br1.1 solid electrolyte prepared in Example 12. As can be seen from the image, the diffraction peaks of the prepared selenide solid electrolyte are in good agreement with the standard PDF card (#49-1298), indicating that the target crystalline phase of the selenide solid electrolyte was successfully synthesized.

[0058] Figure 3 The image shows the XRD pattern of the electrolyte prepared in Comparative Example 1 after heat treatment. The diffraction peaks in the image show good agreement with the standard PDF card (#34-0688), indicating that the comparative sample was successfully synthesized.

[0059] The ionic conductivity of the sulfide solid electrolytes prepared in the examples and comparative examples was tested. The ionic conductivity of the sample electrolytes was determined using AC impedance spectroscopy. Electrolyte powder was pressed into a sheet under specific pressure, and blocking electrodes, such as gold or stainless steel, were coated on both sides to assemble a symmetrical cell. The impedance spectrum was measured within a specific frequency range using an electrochemical workstation to obtain the total impedance value (R). Ionic conductivity (σ) was calculated using the formula σ = L / (R×S), where L is the thickness of the sample electrolyte sheet, and S is the effective contact area between the electrode and the sample electrolyte. All tests were performed at room temperature.

[0060] The specific process parameters and measured room temperature ionic conductivity results for each embodiment and comparative example are summarized in Table 1.

[0061] Table 1. Process parameters and ionic conductivity of the solid electrolytes prepared in the examples and comparative examples.

[0062] As can be seen from the data in Table 1, the ionic conductivity of the selenide solid electrolytes prepared in the various embodiments of this application is generally higher than that of the sulfide solid electrolyte in Comparative Example 1. In particular, Example 12, under optimized process parameters (powdering time 30s, powdering times 9, heating rate 3℃ / min, calcination temperature 600℃, and holding time 15h), achieved an ionic conductivity of 5.53 mS / cm.

[0063] Figure 4This is a comparison graph of the ionic conductivity of Example 12 and Comparative Example 1. The graph visually compares the ionic conductivity of the electrolytes after heat treatment with calcination in Example 12 and Comparative Example 1. It can be seen from the graph that the ionic conductivity of the sample in Example 12 (5.53 mS / cm) is significantly higher than that of the sample in Comparative Example 1 (3.97 mS / cm).

[0064] To assess the atmospheric stability of the electrolyte, 200 mg each of the heat-treated powders from Example 12 and Comparative Example 1 were spread on a petri dish in a dry room with a dew point of -50°C and exposed for 24 hours. The exposed powders were then tableted, and their ionic conductivity was tested again. The conductivity retention rate was calculated as (conductivity after exposure / initial conductivity × 100%).

[0065] Test results show that the sample in Example 12 retained an ionic conductivity of up to 93.12% after 24 hours of exposure. In contrast, the electrolyte in Comparative Example 1 retained only 80.3% of its ionic conductivity under the same conditions. This result fully demonstrates that the selenide electrolyte of this application has significantly better atmospheric environmental stability.

[0066] Figure 5 The graph shows a comparison of the retention rates of ionic conductivity of Example 12 and Comparative Example 1 after exposure to air, illustrating the difference in ionic conductivity retention rates between the two examples after exposure to dry air.

[0067] The selenide solid electrolyte provided in this application benefits from the higher ion migration channels brought about by the complete replacement of sulfur with selenium, and the optimization effect of partial bromine doping on lithium vacancy concentration. The selenide solid electrolyte prepared in the embodiments of this application can achieve an ionic conductivity of more than 5.0 mS / cm at room temperature, and Example 12 reaches 5.53 mS / cm, which is significantly better than typical Li6PS5Cl electrolyte (about 1-3 mS / cm, Comparative Example 1 is 3.97 mS / cm).

[0068] Selenium has a much lower hygroscopicity than sulfur. The selenide electrolyte of this application exhibits extremely low ionic conductivity decay rate and a retention rate greater than 90% after prolonged exposure in low dew point environments, such as -50°C. Example 12 shows a retention rate of 93.12%. In contrast, Li6PS5Cl shows poor stability under the same conditions, with a retention rate of 80.3% in Comparative Example 1. This significantly reduces the requirements for the production environment and helps lower production costs.

[0069] The solid-phase reaction method used in this application combines a high-energy pulverizer and a common muffle furnace. The process is simple, the equipment requirements are low, the raw materials are readily available and the cost is low, making it very suitable for large-scale industrial production and possessing extremely high commercial conversion value.

[0070] The selenide solid electrolyte of this application can be widely used as a solid electrolyte layer in all-solid-state batteries. For example, it can be mixed with positive electrode active materials (such as lithium cobalt oxide, ternary materials, etc.) and conductive agents (such as acetylene black) to prepare positive electrode sheets; and mixed with negative electrode active materials (such as lithium metal, graphite, silicon carbon, etc.) to prepare negative electrode sheets; then the solid electrolyte of this application is filled between the positive and negative electrodes, and pressure is applied to form an all-solid-state lithium battery with high energy density and high safety.

[0071] Obviously, the embodiments described above are merely some of the embodiments in this specification, and not all of them. Based on the embodiments in this specification, those skilled in the art can make other variations or modifications without creative effort, and all such variations should fall within the scope of protection of the embodiments in this specification.

[0072] Other embodiments of the embodiments disclosed herein will readily occur to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This specification is intended to cover any variations, uses, or adaptations of the embodiments thereof that follow the general principles of the embodiments thereof and include common knowledge or customary techniques in the art not disclosed in the embodiments thereof. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the embodiments thereof are indicated by the following claims.

[0073] It should be understood that the embodiments described herein are not limited to the precise structures already described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from their scope. The scope of the embodiments described herein is limited only by the appended claims.

Claims

1. A selenide solid electrolyte, characterized in that, The general chemical formula of the selenide solid electrolyte is Li. 7- y PSe 6-y X y Where 0≤y≤1.6, and X includes at least one of Cl, Br, I, and F.

2. The selenide solid electrolyte according to claim 1, characterized in that, The X contains at least Br.

3. The selenide solid electrolyte according to claim 1, characterized in that, In the general chemical formula, when y = 1.1 and X is Br, the electrolyte is Li. 5.9 PSe 4.9 Br 1.1 .

4. A method for preparing a selenide solid electrolyte, used to prepare the selenide solid electrolyte as described in any one of claims 1-3, characterized in that, Includes the following steps: Under an inert atmosphere, according to the stated chemical formula Li 7-y PSe 6-y X y Lithium source, phosphorus source, selenium source and halogen source X were weighed as raw materials according to the stoichiometric ratio; The raw materials are added to a grinder and mixed to obtain an initial mixed precursor. The initial mixed precursor was placed in a muffle furnace under an inert atmosphere, and after heating and holding for calcination, it was cooled to room temperature with the furnace to obtain an electrolyte block. The electrolyte block is crushed and sieved to obtain the selenide solid electrolyte.

5. The preparation method according to claim 4, characterized in that, The lithium source is at least one of LiH, Li2CO3, LiCl, LiBr, LiI, LiF, Li2S, Li2Se and Li.

6. The preparation method according to claim 4, characterized in that, The phosphorus source is P2S5 or P4S. 10 At least one of P4S3 and P.

7. The preparation method according to claim 4, characterized in that, The selenium source is Se and / or Li2Se.

8. The preparation method according to claim 4, characterized in that, The grinding time of the grinding machine is 10s-60s, and the number of grinding cycles is 5-20.

9. The preparation method according to claim 4, characterized in that, The heating rate is 1-5℃ / min, the holding and calcining temperature is 200℃-650℃, and the holding time is 10-40h.

10. A solid-state battery, characterized in that, Including the selenide solid electrolyte as described in any one of claims 1-3.

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