A composite halide solid-state electrolyte and a method of preparing the same

Abstract

The application relates to a composite halide solid electrolyte and a preparation method thereof, and belongs to the technical field of solid electrolytes. The preparation method comprises the following steps: S1, under a protective atmosphere, uniformly ball-milling a lithium source, a zirconium source, an M source and an ammonium halide, and then sintering, and obtaining a nitrogen-rich halide through cooling; S2, under a protective atmosphere, transferring the nitrogen-rich halide into a reaction chamber of a fluidized bed vapor deposition reactor, then circulating and sequentially introducing a metal / metalloid source compound, water and a lithium source into the reaction chamber to carry out deposition, forming a conductive interface layer on the surface of the nitrogen-rich halide, and obtaining a composite halide; and S3, circulating and sequentially introducing an aluminum source and water into the reaction chamber to carry out deposition, forming a protective layer on the surface of the composite halide, and obtaining a composite halide solid electrolyte. The material can effectively adapt to cyclic stress, avoid cracking and peeling, and ensure the durability and reliability of the protection effect of the battery in the whole service life.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, and particularly relates to a composite halide solid electrolyte and its preparation method. Background Technology

[0002] All-solid-state lithium-ion batteries are considered a core direction for next-generation energy storage technology due to their potential high energy density and inherent safety. Among these, the solid-state electrolyte, as the "heart" of the all-solid-state battery, directly determines its success or failure. Among various solid-state electrolyte systems, halide solid-state electrolytes (such as Li₂ZrCl₆ and Li₃YBr₃) have attracted considerable attention due to their excellent overall performance. These materials typically possess high lithium-ion conductivity, comparable to sulfide electrolytes. Simultaneously, they exhibit excellent chemical stability against high-voltage oxide cathode materials (such as lithium cobalt oxide and high-nickel ternary materials), compensating for the weakness of sulfides being easily oxidized under high voltage. Furthermore, compared to oxide electrolytes that are unstable to lithium metal, some halide electrolytes show better interfacial compatibility with lithium metal anodes. Therefore, halide electrolytes are considered one of the most promising candidate materials for achieving high-energy-density, long-life all-solid-state batteries.

[0003] However, halide solid electrolytes suffer from a fatal weakness in practical applications: extremely poor environmental stability, particularly their extreme sensitivity to atmospheric moisture and oxygen. When exposed to humid air, halide electrolytes undergo rapid and irreversible hydrolysis. For example, Li₂ZrCl₆ reacts with water to produce HCl, Zr(OH)₄, and other products. This process not only completely destroys the material's crystal structure and ion transport channels, leading to a permanent loss of conductivity, but the resulting acidic byproducts also corrode other battery components (such as current collectors and binders), posing serious safety hazards. This "water-destroyed" characteristic necessitates that all subsequent processes—including the synthesis, storage, electrode preparation, and battery assembly of halide electrolytes—must be carried out in an extremely stringent and costly inert atmosphere, severely hindering their large-scale production and commercialization.

[0004] To address the air stability issue of halide electrolytes, existing technologies generally employ a "surface coating" strategy, which involves constructing a physical barrier on the particle surface to prevent water and oxygen corrosion. Current research primarily focuses on coating with oxide coatings, such as introducing a layer of Li₂O-ZrO₂, LiNbO₃, or Li₄Ti₅O₂ onto the surface of halide particles using solution methods, mechanical fusion methods, or atomic layer deposition techniques. 12Oxide films are another type of coating. While these methods have improved the operational tolerance of materials in dry environments to some extent, existing oxide coating technologies suffer from two fundamental and irreconcilable contradictions, preventing them from achieving practical application. First, there is the contradiction between stability and ionic conductivity. To achieve effective isolation, the coating layer needs to be as dense and thick as possible. However, this oxide layer itself is usually a poor lithium-ion conductor (or its ionic conductivity is much lower than that of the halide core), and it introduces significant interfacial impedance between particles, severely sacrificing the overall ionic conductivity and rate performance of the battery. Second, there is the contradiction between physical isolation and chemical compatibility. Simple physical coating layers often exhibit chemical incompatibility with highly reactive halide cores, leading to side reactions at the interface and the formation of a high-impedance interfacial phase. Furthermore, under the stress of battery cycling, the coating layer is prone to cracking. Once a tiny defect appears, moisture can quickly penetrate, causing localized core failure and triggering a chain reaction, rendering the protective effect ineffective.

[0005] In summary, developing a halide electrolyte material and its preparation method that can balance "environmental stability" and "high ionic conductivity" to achieve excellent air stability without sacrificing or even optimizing its intrinsic high ionic conductivity and interfacial compatibility has become an urgent and crucial issue for promoting the development of all-solid-state battery technology. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a composite halide solid electrolyte and its preparation method. It employs a combination of customized synthesis of surface-active nitrogen-rich halides and surface-site-guided in-situ atomic layer deposition. Specifically, lithium, zirconium, M-sources, and ammonium halide are ball-milled until homogeneous. Nitrogen is then introduced from the raw material end through two-stage atmosphere sintering, constructing nitrogen-rich halides rich in active nitrogen species in situ on the particle surface. Subsequently, using these active nitrogen species as specific reaction sites, a conductive interface layer and a protective layer are guided to grow, forming a stable core-shell structure with an initial chemically bonded interface. This "outer shell-inner shell-core" structure exhibits strong cohesion and a firm bond with the core, with matching thermomechanical properties. It effectively adapts to cyclic stress, avoids cracking and peeling, and ensures the durability and reliability of the protective effect throughout the battery's entire lifespan. This integrated "materials-process-interface engineering" approach synergistically overcomes the challenges of environmental stability and high ionic conductivity in halide solid electrolytes.

[0007] The first objective of this invention is to provide a method for preparing a composite halide solid electrolyte, comprising the following steps: S1. Under a protective atmosphere, lithium source, zirconium source, M source and ammonium halide are ball-milled evenly and then sintered and cooled to obtain nitrogen-rich halides; S2. Under a protective atmosphere, the nitrogen-rich halide described in S1 is transferred to the reaction chamber of a fluidized bed vapor deposition reactor. Then, a metal / metal-like source compound, water, and a lithium source are sequentially circulated into the reaction chamber for deposition, forming a conductive interface layer on the surface of the nitrogen-rich halide to obtain a composite halide. S3. Aluminum source and water are sequentially circulated into the reaction chamber for deposition, forming a protective layer on the surface of the composite halide to obtain the composite halide solid electrolyte.

[0008] In one embodiment of the present invention, in S1, the lithium source is selected from LiCl, Li2O or Li3N; And / or, the zirconium source is selected from ZrCl4 or ZrO2; And / or, the M source is selected from M oxide, M chloride, or M bromide; the M in the M source is selected from one or more of Y, In, Sc, Al, Ta, Nb, and W; And / or, the ammonium halide is selected from NH4Cl or NH4Br; on the one hand, the ammonium halide acts as a reaction medium and structure directing agent, regulating the synthesis process and particle surface state, and the incompletely decomposed NH4 during the reaction... + Nitrogenous species such as NH3 or others selectively adsorb or react on the surface of newly grown Li2ZrCl6 grains, forming an extremely thin, metastable surface layer rich in functional groups such as "-NH2", "-NH-", or Li-N bonds. This surface layer does not change the crystal structure and chemical formula of the core bulk phase, but it can completely change its surface chemical properties. On the other hand, ammonium halides serve as specific reaction sites for subsequent atomic layer deposition. The nitrogen-containing functional groups on their surface, which are deliberately retained during the synthesis process, provide ideal, highly active, and specific reaction sites for atomic layer deposition. When a metal / metal-like source compound is pulsed in, it preferentially reacts with the -NH2 and other groups on the surface (such as forming Al-N bonds). Its reactivity is much higher than that of physical adsorption on the surface of inert halides. This chemical bonding initiation from "nitrogen-containing surface" to "atomic layer deposition growth film" ensures the formation of a strong and low-impedance interface between the coating layer and the core.

[0009] In one embodiment of the present invention, in S1, the amounts of the lithium source, zirconium source, and M source satisfy the chemical formula Li 2- a Zr 1-y M y X6,0 <y≤0.4,a=y(V m -4), V m Let M be the valence of M; And / or, the amount of ammonium halide added is 5%-10% of the molar amount of lithium source.

[0010] In one embodiment of the present invention, in S1, the ball mill rotates at a speed of 320 rpm to 380 rpm for a time of 4.5 h to 5.5 h. And / or, the sintering is first performed under an argon atmosphere, with the temperature increased to 320℃-380℃ at a rate of 1.8℃ / min-2.2℃ / min and held for 3h-5h; then, under a mixed atmosphere, the temperature is increased to 520℃-580℃ at a rate of 9.5℃ / min-10.5℃ / min and held for 1h-2h; the mixed atmosphere is selected from argon / ammonia or nitrogen / ammonia.

[0011] In one embodiment of the present invention, the volume ratio of ammonia to another gas in the mixed atmosphere is (0.5-1.5):(98.5-99.5).

[0012] In one embodiment of the present invention, in S2, the metal / metal-like source compound is selected from trimethylaluminum or silicon tetrachloride; And / or, the lithium source is lithium tert-butoxide.

[0013] In one embodiment of the present invention, in S2, the deposition temperature is 160°C-200°C, the pressure is 150Pa-250Pa, and the number of repetitions is 30-80. And / or, the pulse time of the metal / metal-like source compound is 0.1s-0.5s, the nitrogen flow rate is 20sccm-40sccm, and the nitrogen purging time is 30s-60s; And / or, the water pulse time is 0.4s-0.8s, the nitrogen flow rate is 20sccm-40sccm, and the nitrogen purging time is 30s-60s; And / or, the pulse time of the lithium source is 0.3s-0.7s, the nitrogen flow rate is 15sccm-25sccm, and the nitrogen purging time is 70s-110s.

[0014] In one embodiment of the present invention, in S3, the aluminum source is trimethylaluminum.

[0015] In one embodiment of the present invention, in S3, the deposition temperature is 160°C-200°C, the pressure is 150Pa-250Pa, and the number of repetitions is 60-100. And / or, the pulse time of the aluminum source is 0.1s-0.5s, the nitrogen flow rate is 20sccm-40sccm, and the nitrogen purging time is 30s-50s; And / or, the water pulse time is 0.1s-0.3s, the nitrogen flow rate is 15sccm-25sccm, and the nitrogen purging time is 30s-50s.

[0016] A second objective of this invention is to provide a composite halide solid electrolyte prepared by the method described above.

[0017] The technical solution of the present invention has the following advantages compared with the prior art: (1) The preparation method described in this invention successfully solves the core contradiction of the protective layer and the active core being unable to simultaneously achieve stability and ion conductivity through a customized synergistic mechanism of "surface nitrogen functionalization" and "in-situ atomic layer deposition bridging". First, a thermodynamically metastable but kinetically highly active nitrogen-rich surface terminal (such as -Li-NH2) is constructed at the end of the synthesis using ammonium halide. This surface terminal can undergo a specific chemical reaction with the atomic layer deposition precursor. When atomic layer deposition is performed, the metal / metal-like source compound of the first pulse will preferentially react with the groups of the nitrogen-rich surface terminal to form a strong covalent bond. This binding force is much stronger than physical adhesion, thereby effectively avoiding the phenomenon of rapid performance degradation of the battery in subsequent cycles.

[0018] (2) The composite halide solid electrolyte of the present invention adopts a functionally decoupled double-layer structure, namely an inner conductive interface layer and an outer protective layer. The core functions of the inner conductive interface layer are "lithium conduction" and "stress buffering". Its amorphous structure can provide a loose lithium ion migration channel. Although the lithium ion conductivity is not as high as that of the halide core, it is sufficient to serve as a nanoscale ion bridge. More importantly, the conductive interface layer forms a chemical bond with the core through a nitrogen-rich interface, and its modulus is between that of halide and alumina. It can effectively buffer the stress caused by the difference in thermal expansion coefficients between the two, thereby preventing the brittle protective layer from cracking. The core function of the outermost protective layer is "absolute barrier". The protective layer grown by atomic layer deposition technology is one of the densest water / oxygen diffusion barriers. Since the inner conductive interface layer has perfectly solved the interface bonding and ion conduction problem, there is no need to worry too much about the protective layer increasing the interface impedance. Attached Figure Description

[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 The image shows the XRD pattern of the composite halide solid electrolyte in Test Example 1 of this invention. Figure 2 This is a Nyquist electrochemical impedance spectroscopy comparison diagram of the composite halide solid electrolyte in Test Example 2 of the present invention, showing the initial state and the Nyquist electrochemical impedance spectroscopy after being placed in air for 30 minutes. Figure 3 This is a comparison graph showing the initial state of the composite halide solid electrolyte in Test Example 3 of the present invention and its ionic conductivity after being placed in air for 30 minutes. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0021] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified. Example 1

[0024] The composite halide solid electrolyte and its preparation method in this embodiment specifically include the following steps: S1. Preparation of the mixed precursor: In an argon glove box, according to the stoichiometric ratio of Li... 1.8 Zr 0.8 Ta 0.2 Weigh out LiCl, ZrCl4, and TaCl5 respectively, and add NH4Cl at 8% of the molar amount of LiCl; transfer the materials to a ball mill jar, seal it, remove it from the glove box, and ball mill at 350 rpm for 5 hours to obtain a mixed precursor; S2. Preparation of nitrogen-rich halides: The mixed precursors were placed in a tube furnace, argon gas was introduced first, and the temperature was raised to 350°C at a rate of 2°C / min and held for 4 hours; then an argon / ammonia mixture (volume ratio of 99:1) was introduced, and the temperature was raised to 550°C at a rate of 10°C / min and held for 1.5 hours to obtain nitrogen-rich halides. S3. Preparation of composite halides: Nitrogen-rich halides were transferred to the reaction chamber of a fluidized bed vapor deposition reactor after vacuum sealing. The deposition temperature was set to 180℃ and the deposition pressure to 200Pa. Subsequently, trimethylaluminum, deionized water, and lithium tert-butoxide carried by nitrogen were sequentially circulated into the reaction chamber. The pulse duration of trimethylaluminum was 0.3s, the nitrogen flow rate was 30sccm, and the nitrogen purging time was 45s; the pulse duration of deionized water was 0.6s, the nitrogen flow rate was 30sccm, and the nitrogen purging time was 45s; the pulse duration of lithium tert-butoxide was 0.5s, the nitrogen flow rate was 20sccm, and the nitrogen purging time was 90s. This process was repeated 40 times to form a conductive interface layer on the surface of the nitrogen-rich halides, thus obtaining composite halides. S4. Preparation of composite halide solid electrolyte: Trimethylaluminum and deionized water carried by nitrogen are continuously circulated into the reaction chamber in sequence; wherein the pulse duration of trimethylaluminum is 0.3s, the nitrogen flow rate is 30sccm, and the nitrogen purging time is 40s; the pulse duration of deionized water is 0.2s, the nitrogen flow rate is 20sccm, and the nitrogen purging time is 40s; this process is repeated 80 times to form a protective layer on the surface of the composite halide, and the composite halide solid electrolyte is obtained by sieving. Comparative Example 1

[0025] The basic formula is the same as in Example 1, except that NH4Cl is not added. Comparative Example 2

[0026] It is basically the same as Example 1, except that the S3 operation is not performed, that is, there is no conductive interface layer. Comparative Example 3

[0027] It is basically the same as Example 1, except that the S4 operation is not performed, that is, there is no protective layer. Comparative Example 4

[0028] The process is basically the same as in Example 1, except that the order of operations S3 and S4 is reversed, i.e., the protective layer is prepared first, and then the conductive interface layer is prepared. Comparative Example 5

[0029] The process is basically the same as in Example 1, except that the nitrogen-rich halide is divided into two parts, and the S3 and S4 operations are performed separately, and then they are physically mixed together. Comparative Example 6

[0030] The process is basically the same as in Example 1, except that the preparation of nitrogen-rich halides (first synthesizing the halides, then introducing nitrogen) includes the following steps: S1. Preparation of the mixed precursor: In an argon glove box, according to the stoichiometric ratio of Li... 1.8 Zr 0.8 Ta0.2 Weigh out LiCl, ZrCl4, and TaCl5 respectively; transfer the materials to a ball mill jar, seal it, remove it from the glove box, and ball mill at 350 rpm for 5 hours to obtain a mixed precursor; S2. Preparation of halides: The mixed precursors were placed in a tube furnace, argon gas was first introduced, and the temperature was raised to 350°C at a rate of 2°C / min and held for 4 hours; then a mixture of argon and ammonia gas (volume ratio of 99.5:0.5) was introduced, and the temperature was raised to 550°C at a rate of 10°C / min and held for 1 hour to obtain halides. S3. Preparation of nitrogen-rich halides: The halides were mixed evenly with NH4Cl, with the amount of NH4Cl added being 8% of the molar amount of LiCl; then placed in a tube furnace, argon gas was first introduced, and the temperature was raised to 350℃ at a rate of 2℃ / min and held for 4h; subsequently, an argon / ammonia mixture (volume ratio of 99.5:0.5) was introduced, and the temperature was raised to 550℃ at a rate of 10℃ / min and held for 1h to obtain nitrogen-rich halides. Test Example 1

[0031] The composite halide solid electrolyte prepared in Example 1 was filled into the sample holder groove. The sample was compacted and leveled using a glass slide to form a flat, dense test surface flush with the sample holder surface. XRD analysis was then performed under the following conditions: Cu Kα radiation source (λ=1.5406Å), voltage 40kV, current 40mA, scanning range 25°-70°, and scanning speed 5° / min. The test data were recorded and plotted for analysis. The results are shown below. Figure 1 As shown. From Figure 1 It can be seen that the XRD diffraction peaks of the composite halide solid electrolyte correspond precisely to the characteristic peaks of the standard PDF card of the halide core. No extra impurity diffraction peaks were detected. There were no crystalline diffraction signals related to the conductive interface layer or protective layer, nor were there any impurity phase diffraction peaks caused by the introduction of nitrogen or interface reactions. This indicates that the preparation method of the present invention does not destroy the intrinsic crystal structure of the halide core. At the same time, it proves that both the conductive interface layer and the protective layer exist in an amorphous form. This amorphous structure does not interfere with the ion transport channels of the core and can provide a loose migration path for lithium ions. It reflects the design synergy of the "lithium conduction" of the conductive interface layer and the "blocking" of the protective layer in the "functionally decoupled bilayer structure". It further confirms the rationality of the three-in-one integrated scheme of "material-process-interface engineering". Test Example 2

[0032] Electrochemical impedance spectroscopy (EIS) was performed on the composite halide solid electrolyte prepared in Example 1 using an electrochemical workstation. The test conditions were room temperature, frequency range of 1 Hz-1 MHz, and AC amplitude of 5 mV. The impedance characteristics were measured in the initial state (immediately after being removed from the argon glove box) and after being placed in air at 25°C and 45% relative humidity for 30 min. Figure 2 The Nyquist comparison diagram is shown. From... Figure 2 As can be seen, the Nyquist plot of the composite halide solid electrolyte in the embodiment exhibits a very small semicircle diameter in the initial state, indicating that its core-shell structure of "core-conductive interface layer-protective layer" forms a low-impedance lithium-ion transport path. The conductive interface layer and the nitrogen-rich core are firmly bonded by Al-N covalent bonds, without the generation of an additional high-impedance interface phase. After being placed in air for 30 minutes, the semicircle diameter of the Nyquist plot only slightly increases, proving that the outer protective layer effectively blocks water and oxygen intrusion, and the conductive interface layer buffers thermal expansion stress without cracking or peeling, demonstrating a long-lasting and stable protective effect. This demonstrates the effectiveness of the synergistic mechanism of "surface nitrogen functionalization" and "in-situ atomic layer deposition bridging." By introducing ammonium halide in situ onto a nitrogen-rich surface to provide specific reaction sites, the conductive interface layer forms a chemical bond with the core. At the same time, the functionally decoupled double-layer structure not only ensures the water and oxygen barrier properties of the protective layer but also reduces the interface impedance through the conductive interface layer, successfully solving the core contradictions of stability and ionic conductivity, and physical isolation and chemical compatibility in traditional coating technologies. Test Example 3

[0033] The ionic conductivity of the composite halide solid electrolytes prepared in Example 1 and Comparative Examples 1-6 was tested using an electrochemical workstation. The test conditions were room temperature, frequency range of 1Hz-1MHz, and AC amplitude of 5mV. The ionic conductivity of each sample was measured immediately after being removed from the argon glove box and after being placed in air at 25°C and 45% relative humidity for 30 minutes. The results are as follows: Figure 3 As shown in Table 1: Table 1

[0034] from Figure 3 As can be seen from Table 1, the composite halide solid electrolyte of Example 1 exhibits the best overall performance: its initial room temperature ionic conductivity reaches as high as 1.93 × 10⁻⁶. -3 S / cm; After being placed in air at 25℃ and 45% relative humidity for 30 minutes, the conductivity remained at 1.72×10⁻⁶. -3 The S / cm decreased by only about 10.9%, demonstrating the perfect synergy between "high ionic conductivity" and "excellent air stability", which confirms the effectiveness of "in-situ nitrogen functionalization + functional decoupling double-layer coating".

[0035] Comparing Example 1 and Comparative Example 1, it can be seen that Comparative Example 1, without the addition of ammonium halide (no nitrogen element introduced), showed an initial ionic conductivity decrease of approximately 23% compared to Example 1, and a conductivity decrease of 29.7% after air exposure. This indicates that the in-situ introduction of nitrogen is crucial. The active sites formed on the nitrogen-rich surface allow the coating layer to form chemical bonds with the core, which reduces interfacial impedance, ensures ion transport, and enhances structural stability. In contrast, in the nitrogen-free system, the coating layer and the core are only physically attached, resulting in high interfacial impedance and easy peeling, leading to a double decline in conductivity and stability.

[0036] Comparing Example 1 and Comparative Example 2, it can be seen that Comparative Example 2, without the S3 operation (no conductive interface layer) and only retaining the protective layer, has an initial ionic conductivity less than half that of Example 1, and its conductivity decreases by 40.4% after air exposure. This demonstrates the crucial role of the conductive interface layer: on the one hand, it acts as an "ion bridge" to reduce interface impedance, and on the other hand, it buffers thermal expansion stress to prevent the protective layer from cracking. Without this layer, the high-impedance protective layer directly contacts the core, which not only blocks ion transport but also makes it susceptible to water and oxygen intrusion due to interface reactions and stress cracking, resulting in a significant deterioration in both conductivity and stability.

[0037] Comparing Example 1 and Comparative Example 3, it can be seen that Comparative Example 3, without the S4 operation (no protective layer), had a lower initial ionic conductivity than Example 1, and its conductivity decreased by 50% after air exposure. This indicates that the protective layer is a key barrier to isolate water and oxygen: the conductive interface layer alone cannot effectively block water vapor erosion, and the halide core will still undergo hydrolysis, leading to crystal structure destruction and blockage of ion transport channels. Although some initial conductivity is retained, the air stability does not meet practical requirements at all.

[0038] Comparing Example 1 and Comparative Example 4, it can be seen that Comparative Example 4 reversed the order of the conductive interface layer and the protective layer (protective layer first, then conductive interface layer), and the initial ionic conductivity was only 0.53 × 10⁻⁶. -3 S / cm, which decreased to 0.31×10 after exposure to air. -3 S / cm indicates the necessity of the "inner lithium-conducting layer + outer barrier" functional decoupling design: when the protective layer with extremely low ionic conductivity is located in the middle, it will directly block the lithium-ion transport channel, and the outer conductive interface layer cannot play a water and oxygen barrier role, resulting in a double collapse of conductivity and stability.

[0039] Comparing Example 1 and Comparative Example 5, it can be seen that Comparative Example 5, which physically mixes the conductive interface layer and the protective layer separately, has a lower initial ionic conductivity than Example 1, and the conductivity decreases by 30% after air exposure. This indicates that "in-situ continuous deposition" is key: in physically mixed powders, particles containing only the conductive interface layer have acceptable ion transport but insufficient stability, while particles containing only the protective layer have limited stability but hindered ion transport, exhibiting a significant bottleneck effect; while the in-situ continuous deposition in Example 1 forms an integrated "core-inner shell-outer shell" structure with tight chemical bonding, no performance bottlenecks, and superior overall performance.

[0040] Comparing Example 1 and Comparative Example 6, it can be seen that Comparative Example 6, which uses the method of "synthesizing halides first and then introducing nitrogen", has an initial ionic conductivity that is less than half that of Example 1, and the conductivity decreases by 35.2% after air exposure. This demonstrates the importance of "in-situ introduction" of nitrogen: In Example 1, nitrogen species coexist with halide crystals, resulting in good surface chemical homogeneity and strong bonding with the bulk, providing high-quality reaction sites for subsequent ALD deposition; while the "post-treatment modification" of Comparative Example 6 forcibly introduces nitrogen into the already stabilized crystal surface, resulting in weak bonding strength, poor chemical homogeneity, and low quality of the subsequent coating interface, leading to a significant deterioration in both ionic conductivity and stability.

[0041] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a composite halide solid electrolyte, characterized in that, Includes the following steps: S1. Under a protective atmosphere, lithium source, zirconium source, M source and ammonium halide are ball-milled evenly and then sintered and cooled to obtain nitrogen-rich halides; S2. Under a protective atmosphere, the nitrogen-rich halide described in S1 is transferred to the reaction chamber of a fluidized bed vapor deposition reactor. Then, a metal / metal-like source compound, water, and a lithium source are sequentially circulated into the reaction chamber for deposition, forming a conductive interface layer on the surface of the nitrogen-rich halide to obtain a composite halide. S3. Aluminum source and water are sequentially circulated into the reaction chamber for deposition, forming a protective layer on the surface of the composite halide to obtain the composite halide solid electrolyte.

2. The method for preparing the composite halide solid electrolyte according to claim 1, characterized in that, In S1, the lithium source is selected from LiCl, Li2O or Li3N; And / or, the zirconium source is selected from ZrCl4 or ZrO2; And / or, the M source is selected from M oxide, M chloride, or M bromide; the M in the M source is selected from one or more of Y, In, Sc, Al, Ta, Nb, and W; And / or, the ammonium halide is selected from NH4Cl or NH4Br.

3. The method for preparing the composite halide solid electrolyte according to claim 1, characterized in that, In S1, the amounts of the lithium source, zirconium source, and M source satisfy the chemical formula Li 2-a Zr 1-y M y X6,0 <y≤0.4,a=y(V m -4), V m Let M be the valence of M; And / or, the amount of ammonium halide added is 5%-10% of the molar amount of lithium source.

4. The method for preparing the composite halide solid electrolyte according to claim 1, characterized in that, In S1, the ball mill operates at a rotation speed of 320 rpm to 380 rpm for a time of 4.5 h to 5.5 h. And / or, the sintering is first performed under an argon atmosphere, with the temperature increased to 320℃-380℃ at a rate of 1.8℃ / min-2.2℃ / min and held for 3h-5h; Then, under a mixed atmosphere, the temperature is increased to 520℃-580℃ at a rate of 9.5℃ / min-10.5℃ / min and held for 1h-2h; the mixed atmosphere is selected from argon / ammonia or nitrogen / ammonia.

5. The method for preparing the composite halide solid electrolyte according to claim 4, characterized in that, The volume ratio of ammonia to another gas in the mixed atmosphere is (0.5-1.5):(98.5-99.5).

6. The method for preparing the composite halide solid electrolyte according to claim 1, characterized in that, In S2, the metal / metal-like source compound is selected from trimethylaluminum or silicon tetrachloride; And / or, the lithium source is lithium tert-butoxide.

7. The method for preparing the composite halide solid electrolyte according to claim 1, characterized in that, In S2, the deposition temperature is 160℃-200℃, the pressure is 150Pa-250Pa, and the number of repetitions is 30-80. And / or, the pulse time of the metal / metal-like source compound is 0.1s-0.5s, the nitrogen flow rate is 20sccm-40sccm, and the nitrogen purging time is 30s-60s; And / or, the water pulse time is 0.4s-0.8s, the nitrogen flow rate is 20sccm-40sccm, and the nitrogen purging time is 30s-60s; And / or, the pulse time of the lithium source is 0.3s-0.7s, the nitrogen flow rate is 15sccm-25sccm, and the nitrogen purging time is 70s-110s.

8. The method for preparing the composite halide solid electrolyte according to claim 1, characterized in that, In S3, the aluminum source is trimethylaluminum.

9. The method for preparing the composite halide solid electrolyte according to claim 1, characterized in that, In S3, the deposition temperature is 160℃-200℃, the pressure is 150Pa-250Pa, and the number of repetitions is 60-100. And / or, the pulse time of the aluminum source is 0.1s-0.5s, the nitrogen flow rate is 20sccm-40sccm, and the nitrogen purging time is 30s-50s; And / or, the water pulse time is 0.1s-0.3s, the nitrogen flow rate is 15sccm-25sccm, and the nitrogen purging time is 30s-50s.

10. A composite halide solid electrolyte prepared by the method according to any one of claims 1-9.

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