Halide solid state electrolyte, method of making the same, and solid state battery comprising the halide solid state electrolyte

Abstract

This invention provides a halide solid electrolyte, its preparation method, and a solid-state battery including the halide solid electrolyte. Specifically, the preparation method includes: (1) adding a matrix material, a main dopant, and an auxiliary dopant to an aprotic organic solvent under an inert atmosphere, stirring and ultrasonically dispersing, then adding an interface modifier and continuing stirring to obtain a precursor solution; (2) subjecting the precursor solution to vacuum freeze-drying to remove the aprotic organic solvent to obtain a precursor powder, then sintering the precursor powder under an inert atmosphere to obtain a pre-synthesized powder; (3) mechanically ball-milling the pre-synthesized powder under an inert atmosphere to obtain a fine-grained powder, then cold-pressing the fine-grained powder into a solid shape. The halide solid electrolyte prepared according to the technical solution of this invention has high ionic conductivity, a wide electrochemical window, and good humidity stability, improving the cycle life and safety of all-solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery material technology, specifically relating to a halide solid electrolyte and its preparation method, as well as an all-solid-state battery containing the electrolyte. Background Technology

[0002] With the rapid growth of global energy storage demand, all-solid-state batteries are considered the core development direction of next-generation energy storage systems due to their outstanding advantages such as high energy density and excellent safety. As the core component of all-solid-state batteries, the performance of the solid electrolyte directly determines the battery's energy density, cycle life, and safety performance. Currently, the mainstream solid electrolyte systems include four categories: oxides, sulfides, polymers, and halides. Among them, halide solid electrolytes, with their good electrochemical oxidation stability, excellent deformation capability, and high ionic conductivity potential, have become the preferred electrolyte material for high-voltage all-solid-state batteries.

[0003] Despite the many advantages of halide solid electrolytes, there are still several technical problems that need to be solved in the current technology.

[0004] First, the room temperature ionic conductivity of traditional halide electrolytes such as Na₂ZrCl₆ (NZC) is only 6.46 × 10⁻⁶. -6 S•cm -1 Furthermore, it is prone to oxidation and decomposition at voltages exceeding 3.9 V, making it difficult to meet the application requirements of high-power, high-voltage batteries. While fluorine doping can improve high-voltage stability, fluorine reacts with charge carriers (Li... + / Na + The strong Coulomb interaction between the two groups can easily lead to an increase in the ion migration energy barrier, which restricts the improvement of conductivity; while chlorine and bromine halides have relatively high conductivity, but lack high-voltage stability.

[0005] Furthermore, halide solid electrolytes are prone to irreversible chemical degradation when exposed to humid environments, leading to a rapid decrease in ionic conductivity. In existing technologies, single-element doping (such as In)... 3+ Although it can improve humidity stability to some extent, the conductivity retention rate is still less than 70% in environments with humidity exceeding 5%; while physical modification methods such as Al2O3 coating have problems such as poor bonding between the coating and the electrolyte interface and easy detachment after long-term cycling.

[0006] Furthermore, while halide electrolytes exhibit high oxidative stability, they have low reduction stability. When in contact with negative electrodes such as lithium or sodium metals, they are prone to interfacial side reactions, generating high-resistivity products that lead to decreased battery cycle life. Simultaneously, poor solid-solid interface contact between the electrolyte and the positive electrode material further increases interfacial impedance and reduces ion transport efficiency. While existing three-layer composite electrolyte structures (halide layer-sulfide layer-polymer silver layer) can improve interfacial performance, their complex design, high manufacturing cost, and susceptibility to interfacial delamination between layers are significant challenges.

[0007] In terms of preparation process, solid phase synthesis methods (such as mechanical ball milling and sintering) are prone to introducing impurities, resulting in low product purity and uneven grain size distribution; liquid phase synthesis methods (such as aqueous medium synthesis and ammonia-assisted synthesis) have the risk of solvent residue or require special corrosion-resistant equipment, which is not conducive to large-scale production.

[0008] Therefore, developing a halide solid electrolyte that combines high ionic conductivity, excellent high-voltage stability, good humidity tolerance and interfacial compatibility, and has a simple preparation process and controllable cost is of great significance for promoting the commercialization of all-solid-state batteries. Summary of the Invention

[0009] Based on the technical problems described above, this invention aims to provide a high-performance halide solid electrolyte and its preparation method, so as to solve the problems of low ionic conductivity, poor high voltage and humidity stability, high interfacial impedance, and complex preparation process and high cost in the prior art, thereby improving the performance of the electrolyte.

[0010] Specifically, according to one aspect of the present invention, a method for preparing a halide solid electrolyte is provided, the method comprising the following steps:

[0011] (1) Under an inert atmosphere, the matrix material, main dopant and auxiliary dopant are added to an aprotic organic solvent, stirred and ultrasonically dispersed, then an interface modifier is added and stirring is continued to obtain a precursor solution;

[0012] (2) The precursor solution is subjected to vacuum freeze-drying to remove the aprotic organic solvent to obtain precursor powder. The precursor powder is then sintered under an inert atmosphere to obtain pre-synthesized powder.

[0013] (3) The pre-synthesized powder is mechanically ball-milled under an inert atmosphere to obtain fine-grained powder, which is then cold-pressed to obtain the halide solid electrolyte, wherein:

[0014] The matrix material is selected from one or more of lithium-based halides or sodium-based halides;

[0015] The main dopant is a mixture of fluoride and bromide in a weight ratio of 1:3 to 1:6, wherein the fluoride is selected from at least one of LiF, NaF and AlF3, and the bromide is selected from at least one of LiBr, NaBr and ZrBr4;

[0016] The auxiliary dopant is selected from at least one of La2O3, In2O3 and MgO;

[0017] The interface modifier is hexachlorocyclotriphosphazene;

[0018] Based on the total weight of the matrix material, the main dopant, the auxiliary dopant, and the interface modifier as 100%, the content of the matrix material is 70-85%, preferably 75-80%, the content of the main dopant is 5-15%, preferably 8-12%, the content of the auxiliary dopant is 3-10%, preferably 5-8%, and the content of the interface modifier is 2-8%, preferably 3-6%.

[0019] According to certain preferred embodiments of the present invention, the lithium-based halide is selected from at least one of Li3YCl6, Li2ZrCl6, Li3InCl6 and Li6SnCl8.

[0020] According to certain preferred embodiments of the present invention, the sodium-based halide is selected from at least one of Na2ZrCl6, Na3AlCl6 and Na3InCl6.

[0021] According to certain preferred embodiments of the present invention, the matrix material is a mixture of Li3YCl6 and Na2ZrCl6 in a weight ratio of 1:2 to 1:5.

[0022] According to certain preferred embodiments of the present invention, the main dopant is a mixture of LiF and ZrBr4 in a weight ratio of 1:3 to 1:5.

[0023] According to certain preferred embodiments of the present invention, the matrix material, the main dopant and the auxiliary dopant are dried before step (1).

[0024] According to certain preferred embodiments of the present invention, the drying process includes drying the matrix material, the main dopant, and the auxiliary dopant under vacuum at a temperature of 80-120°C for 12-24 hours.

[0025] According to certain preferred embodiments of the present invention, the aprotic organic solvent is selected from at least one of tetrahydrofuran (THF), dimethyl ethylene glycol (DME), and propylene carbonate (PC).

[0026] According to certain preferred embodiments of the present invention, the ratio of the total weight of the matrix material, the main dopant, the auxiliary dopant and the interface modifier to the weight of the aprotic organic solvent is in the range of 1:5 to 1:10.

[0027] According to certain preferred embodiments of the present invention, the ultrasonic dispersion time in step (1) is 30-60 minutes.

[0028] According to certain preferred embodiments of the present invention, the vacuum freeze-drying in step (2) is performed at a temperature of -50 to -30°C, a vacuum degree of ≤ 10 Pa, and a time of 24-48 hours.

[0029] According to certain preferred embodiments of the present invention, the sintering temperature in step (2) is 200-300°C, the heating rate is 2-5°C / min, and the holding time is 2-4 hours.

[0030] According to certain preferred embodiments of the present invention, the grinding media for the mechanical ball milling in step (3) is zirconia balls.

[0031] According to certain preferred embodiments of the present invention, the ball-to-material ratio of the mechanical ball mill in step (3) is 20:1-40:1.

[0032] According to certain preferred embodiments of the present invention, the mechanical ball milling in step (3) rotates at a speed of 300-500 rpm for 8-12 hours.

[0033] According to certain preferred embodiments of the present invention, the pressure of cold pressing in step (3) is 300-500 MPa, and the holding time is 5-10 minutes.

[0034] According to certain preferred embodiments of the present invention, the inert atmosphere is argon or nitrogen.

[0035] According to another aspect of the present invention, a halide solid electrolyte is provided, which is prepared according to the method described above.

[0036] According to certain preferred embodiments of the present invention, the room temperature ionic conductivity of the halide solid electrolyte is 2.5-5.0 mS•cm. -1 .

[0037] According to certain preferred embodiments of the invention, the electrochemical window of the halide solid electrolyte is 0-5.0 V (vs. Li / Li). + ).

[0038] According to certain preferred embodiments of the present invention, after the halide solid electrolyte is exposed to an environment with a humidity of 5-10% for 72 hours, the ionic conductivity retention rate is greater than or equal to 85%.

[0039] According to another aspect of the present invention, a solid-state battery is provided, the solid-state battery comprising:

[0040] positive electrode;

[0041] negative electrode;

[0042] The halide solid electrolytes described above.

[0043] According to certain preferred embodiments of the present invention, the positive electrode comprises a positive electrode active material, a conductive agent, and the halide solid electrolyte.

[0044] According to certain preferred embodiments of the present invention, the content of the positive electrode active material is 60-80% based on 100% by weight of the positive electrode, the content of the conductive agent is 5-10%, and the content of the halide solid electrolyte is 15-25%.

[0045] According to certain preferred embodiments of the present invention, the surface of the negative electrode is provided with an interface modification layer, the interface modification layer comprising the halide solid electrolyte and metal alloy powder.

[0046] According to certain preferred embodiments of the present invention, the metal alloy powder is selected from at least one of lithium-based alloys or sodium-based alloys.

[0047] According to certain preferred embodiments of the present invention, the lithium-based alloy is selected from at least one of Li-In alloy or Li-Sn alloy, and the sodium-based alloy is Na-Sn alloy.

[0048] According to certain preferred embodiments of the present invention, the content of the halide solid electrolyte is 60-80% and the content of the metal alloy powder is 20-40% based on 100% of the weight of the interface modification layer.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: through multi-element synergistic doping and gradient interface modification design, the room temperature ionic conductivity of the halide solid electrolyte is significantly improved to 2.5-5.0 mS•cm. -1 The electrochemical window is widened to 4.5-5.0 V, exhibiting excellent high-voltage stability. After 72 hours of exposure to 5-10% humidity, the conductivity retention rate remains above 85%, demonstrating significantly enhanced humidity tolerance. The assembled solid-state battery exhibits low interfacial impedance and good cycle stability. Furthermore, the employed low-temperature liquid-phase-mechanical ball milling composite preparation process is simple, energy-efficient, and has controllable raw material costs, facilitating large-scale production. Its overall performance surpasses existing technologies. Attached Figure Description

[0050] The accompanying drawings are provided in this specification to more clearly explain the technical solutions of the present invention; however, the art is not limited thereto.

[0051] Figure 1 A flowchart illustrating the preparation process of a solid electrolyte according to the present invention is shown.

[0052] Figure 2 A scanning electron microscope (SEM) image of the halide solid electrolyte prepared in Example 1 is shown;

[0053] Figure 3 The X-ray diffraction (XRD) pattern of the solid electrolyte prepared in Example 1 is shown. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It will be understood that other embodiments may be implemented without departing from the scope or spirit of the invention. Therefore, the following detailed description is non-limiting.

[0055] Unless otherwise specified, all figures used in this specification to represent characteristic dimensions, quantities, and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters listed in the foregoing specification are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired properties using the teachings disclosed herein.

[0056] As mentioned above, existing halide solid electrolytes suffer from the following problems in terms of performance and preparation process: First, it is difficult to balance ionic conductivity and high-voltage stability; traditional materials have low conductivity and are prone to decomposition under high voltage. Second, they have poor humidity stability, easily degrading in air and causing a sharp drop in performance. Third, they have poor compatibility with the solid-solid interface of the electrode, resulting in high interfacial impedance and a tendency for side reactions, affecting cycle life. Fourth, the preparation process has defects; solid-phase methods easily introduce impurities, while liquid-phase methods leave solvent residues or require special equipment, making it difficult to achieve high purity, low cost, and large-scale production. This invention aims to solve the above problems.

[0057] Specifically, according to one aspect of the present invention, a method for preparing a halide solid electrolyte is provided, the method comprising the following steps:

[0058] (1) Under an inert atmosphere, the matrix material, main dopant and auxiliary dopant are added to an aprotic organic solvent, stirred and ultrasonically dispersed, then an interface modifier is added and stirring is continued to obtain a precursor solution;

[0059] (2) The precursor solution is subjected to vacuum freeze-drying to remove the aprotic organic solvent to obtain precursor powder. The precursor powder is then sintered under an inert atmosphere to obtain pre-synthesized powder.

[0060] (3) The pre-synthesized powder is mechanically ball-milled under an inert atmosphere to obtain fine-grained powder, which is then cold-pressed to obtain the halide solid electrolyte, wherein:

[0061] The matrix material is selected from one or more of lithium-based halides or sodium-based halides;

[0062] The main dopant is a mixture of fluoride and bromide in a weight ratio of 1:3 to 1:6, wherein the fluoride is selected from at least one of LiF, NaF and AlF3, and the bromide is selected from at least one of LiBr, NaBr and ZrBr4;

[0063] The auxiliary dopant is selected from at least one of La2O3, In2O3 and MgO;

[0064] The interface modifier is hexachlorocyclotriphosphazene;

[0065] Based on the total weight of the matrix material, the main dopant, the auxiliary dopant, and the interface modifier as 100%, the content of the matrix material is 70-85%, preferably 75-80%, the content of the main dopant is 5-15%, preferably 8-12%, the content of the auxiliary dopant is 3-10%, preferably 5-8%, and the content of the interface modifier is 2-8%, preferably 3-6%.

[0066] Figure 1 A flowchart illustrating the preparation of a solid electrolyte according to the present invention is shown. Specifically, the preparation method includes the following steps:

[0067] S1: Under an inert atmosphere, the matrix material, main dopant and auxiliary dopant are added to an aprotic organic solvent, stirred and ultrasonically dispersed, and then an interface modifier is added to obtain a precursor solution.

[0068] S2: The precursor solution is freeze-dried under vacuum to obtain precursor powder, and then the precursor powder is sintered under an inert atmosphere to obtain pre-synthesized powder.

[0069] S3: The pre-synthesized powder is mechanically ball-milled under an inert atmosphere to obtain fine-grained powder, which is then cold-pressed into shape.

[0070] Specifically, the invention solves the problems of poor conductivity and stability and poor interfacial compatibility of traditional halide electrolytes by using a quaternary synergistic design of matrix material, main dopant, auxiliary dopant and interface modifier.

[0071] The matrix material, as the framework structure of the electrolyte, significantly influences ionic conductivity due to its ion transport channel characteristics. According to the technical solution of this invention, lithium-based halides or sodium-based halides are used as the matrix, preferably lithium-based halides such as Li3YCl6, Li2ZrCl6, Li3InCl6, and Li6SnCl8, and sodium-based halides such as Na2ZrCl6, Na3AlCl6, and Na3InCl6. These halides have open crystal structures, which is beneficial for Li… + Na + It migrates rapidly and has better chemical stability than traditional sulfide electrolytes.

[0072] Preferably, the technical solution according to the present invention uses a composite matrix of Li3YCl6 and Na2ZrCl6 with a weight ratio of 1:2-1:5. This composite system can form a solid solution structure with moderate lattice distortion: Li3YCl6 has high ion mobility, while Na2ZrCl6 has excellent structural stability. The composite of the two can retain the properties of Li... + A fast transmission channel, and can also be used via Na + The lattice occupancy modulates the ion migration energy barrier, significantly improving conductivity and structural stability.

[0073] According to the technical solution of the present invention, the content of the matrix material is 70-85% (preferably 75-80%). If the content is less than 70%, the electrolyte skeleton structure is incomplete, the ion transport channels are blocked, and the conductivity decreases. If the content is higher than 85%, the effect of the dopant and the interface modifier is weakened, the high voltage stability and humidity tolerance decrease, and it is difficult to meet the application requirements of high voltage batteries.

[0074] According to the technical solution of the present invention, the main dopant is a mixture of fluoride and bromide with a weight ratio of 1:3 to 1:6, wherein the fluoride is selected from LiF, NaF, and AlF3, and the bromide is selected from LiBr, NaBr, and ZrBr4, preferably a mixture of LiF and ZrBr4 with a weight ratio of 1:3 to 1:5. This binary doping system enhances the technical effect of resolving the contradiction between conductivity and high-voltage stability in traditional single doping through the synergistic effect of "fluorine enhancing stability and bromine improving conductivity".

[0075] F in fluorides - With a small ionic radius (0.133 nm), it can replace Cl in the halide lattice. - This forms stronger ionic bonds, improves the oxidative stability of the electrolyte, and broadens the electrochemical window; simultaneously, F- Its high electronegativity can suppress interfacial side reactions between the electrolyte and the positive electrode material. Meanwhile, Br in bromides... - It has a relatively large ionic radius (0.196 nm) and substitutes Cl. - Then, a moderate lattice distortion can be introduced to reduce the Li + / Na + The migration barrier is increased, thus improving conductivity. The weight ratio of the two is controlled between 1:3 and 1:6. If the proportion of fluoride is too high (e.g., a weight ratio of 1:2), the ion migration barrier will increase and the conductivity will decrease; if the proportion of bromide is too high (e.g., a weight ratio of 1:7), the lattice distortion will be excessive, the structural stability will be reduced, and it will be easy to decompose under high pressure.

[0076] According to the technical solution of the present invention, the content of the main dopant is 5-15% (preferably 8-12%). If the content is too low, the doping modification effect will be not obvious and the improvement of high voltage stability will be limited; if the content is too high, it will destroy the crystal structure of the matrix and cause the ion transport channels to be blocked.

[0077] The technical solution of the present invention also employs an auxiliary dopant. The auxiliary dopant is selected from at least one of La₂O₃, In₂O₃, and MgO, and its core function is to further optimize the humidity stability and interfacial compatibility of the electrolyte. The metal cations of these oxides (La₂O₃, In₂O₃, and MgO) 3+ In 3+ Mg 2+ It can bind to defect sites in the halide lattice, inhibiting the bonding of moisture with lattice Cl. - The reaction (such as avoiding the formation of HCl and hydroxides) is mitigated, and the oxygen atoms on the oxide surface can form chemical bonds with the interface modifier, enhancing the interfacial bonding force. The content of the auxiliary dopant is 3-10% (preferably 5-8%). If the content is too low, the defect repair and humidity protection effects will be insufficient; if the content is too high, the oxide is prone to agglomeration, blocking ion transport channels and reducing conductivity.

[0078] In step (1) of the preparation method of the halide solid electrolyte according to the present invention, an interface modifier is also added. The interface modifier is hexachlorocyclotriphosphazene (N3P3Cl6), whose molecular structure contains P-Cl bonds and lone pair electrons of N atoms, which can form coordination bonds with hydroxyl groups and halide ions on the electrolyte surface, and at the same time form chemical bonds with electrode materials (positive electrode active material, negative electrode metal), thereby realizing chemical bonding modification of the "electrolyte-electrode" interface.

[0079] Specifically, hexachlorocyclotriphosphazene can form a dense protective film on the electrolyte surface: on the one hand, it isolates moisture in the air, inhibits the hydrolysis reaction of the electrolyte, and improves humidity stability; on the other hand, it reduces the interfacial energy between the electrolyte and the electrode, improves solid-solid interface contact, and inhibits interfacial side reactions (such as preventing lithium metal from reacting with the electrolyte to form high-resistivity LiCl). According to the technical solution of the present invention, the content of the interface modifier is 2-8% (preferably 3-6%). If the content is too low, a complete protective film cannot be formed; if the content is too high, the modifier is prone to aggregate to form an insulating layer, increasing the interfacial impedance.

[0080] In the preparation method of the halide solid electrolyte according to the present invention, preferably, before step (1), the matrix material, main dopant and auxiliary dopant are dried under vacuum at 80-120°C for 12-24 hours to remove moisture and trace organic impurities adsorbed on the surface of the raw materials. Halide raw materials are hygroscopic and will generate hydroxides (such as Y(OH)3, Zr(OH)4). These impurities may block ion transport channels, reduce conductivity, and easily decompose to generate gas during sintering, leading to the formation of pores inside the electrolyte and affecting its compactness.

[0081] In step (1), a precursor solution is prepared under an inert atmosphere (argon or nitrogen). The aprotic organic solvent is selected from tetrahydrofuran (THF), dimethyl ethylene glycol (DME), and propylene carbonate (PC). These solvents have high dielectric constants and good solubility, which can disperse the matrix material and dopants to form a stable suspension. Among them, THF has a low boiling point (66°C), is easy to remove during subsequent freeze-drying, and has the best solubility for halides, making it a preferred solvent.

[0082] Preferably, the weight ratio of the total raw material to the organic solvent is limited to 1:5-1:10. The ultrasonic dispersion time is preferably 30-60 minutes, and the ultrasonic frequency is preferably 40 kHz. Mechanical vibration can break up the raw material agglomerates, so that each component is uniformly dispersed in the solvent to form a suspension with uniform particle size.

[0083] After adding the interface modifier, continue stirring for 2-4 hours to ensure that hexachlorocyclotriphosphazene comes into full contact with other raw materials and forms molecular-level interactions, thus avoiding local aggregation of the modifier during subsequent drying and sintering.

[0084] In step (2), the vacuum freeze-drying temperature is -50 to -30°C, the vacuum degree is ≤10 Pa, and the time is 24-48 hours. This process solidifies the solvent by freezing at low temperature and then removes the solvent by direct sublimation under high vacuum, avoiding the raw material agglomeration and component segregation caused by solvent evaporation in traditional hot air drying. The resulting precursor powder has a loose porous structure with a large specific surface area, which is conducive to the reaction and diffusion of each component in the subsequent sintering process.

[0085] Preferably, the sintering process is carried out under an inert atmosphere at a temperature of 200-300℃, a heating rate of 2-5℃ / min, and a holding time of 2-4 hours. This low-temperature sintering process can achieve solid-state reactions of each component to form the target halide structure, while avoiding the decomposition and volatilization of halides at high temperatures (the sintering temperature of traditional solid-state synthesis methods is mostly 400-600℃, which easily leads to the volatilization of LiCl).

[0086] In step (3), preferably, the grinding media for mechanical ball milling is zirconia balls, which have high hardness, good chemical stability, do not introduce impurities, and have strong wear resistance, making them suitable for long-term use. Preferably, the ball-to-material ratio is 20:1-40:1, the rotation speed is 300-500 rpm, and the time is 8-12 hours. High-energy ball milling refines the pre-synthesized powder into fine-grained powder (particle size 0.5-2 μm), increasing the specific surface area and introducing appropriate lattice defects to further reduce the ion migration barrier.

[0087] Preferably, the cold pressing pressure is 300-500 MPa, and the holding time is 5-10 minutes. The 5-10 minute holding time ensures that the powder is fully compacted to form a dense electrolyte sheet with a density of over 95%, thus ensuring rapid ion transport.

[0088] According to the present invention, the entire preparation process in step (3) is carried out under an inert atmosphere (argon or nitrogen). Argon has better chemical inertness than nitrogen and is less likely to react with halides, making it the preferred atmosphere. This low-temperature liquid-phase-mechanical ball milling composite process avoids the high-temperature sintering problem of the traditional solid-phase method and the solvent residue problem of the liquid-phase method. The process is simple, energy-efficient, and the raw material cost is controllable, making it easy to scale up industrially.

[0089] The halide solid electrolyte prepared by this invention, through the synergistic design of the raw material system and process optimization, possesses the following performance advantages:

[0090] 1. High room temperature ionic conductivity: The solid electrolyte prepared in this invention exhibits a room temperature ionic conductivity of 2.5-5.0 mS•cm. -1 This is higher than that of traditional halide electrolytes (such as Na2ZrCl6, which has a concentration of 6.46 × 10⁻⁶). -6 S•cm -1 It is superior to existing sulfide electrolytes (such as LPS electrolytes with 1.5 mS•cm) in terms of performance. -1 ).

[0091] 2. Wide electrochemical window: The solid electrolyte prepared in this invention has an electrochemical window of 0-5.0 V (vs. Li / Li). +It has a voltage higher than the approximately 3.9 V of traditional halide electrolytes, and can be matched with high-voltage cathode materials (such as NCM811, LiCoO2, etc., with an operating voltage of 3.5-4.5 V).

[0092] 3. Good humidity stability: After being exposed to an environment with a humidity of 5-10% for 72 hours, the solid electrolyte prepared by this invention retains an ionic conductivity of greater than or equal to 80% (or even as high as ≥90%), which is superior to the prior art.

[0093] 4. Good interfacial compatibility: The solid electrolyte prepared by this invention has low interfacial impedance with the positive and negative electrode materials, and good interfacial stability during long-term cycling.

[0094] According to another aspect of the present invention, a solid-state battery is provided, the solid-state battery comprising:

[0095] positive electrode;

[0096] negative electrode;

[0097] The halide solid electrolytes described above.

[0098] Preferably, the positive electrode comprises a positive electrode active material, a conductive agent, and a halide solid electrolyte of the present invention, wherein the weight ratio of the three is: 60-80% positive electrode active material, 5-10% conductive agent, and 15-25% halide solid electrolyte.

[0099] Preferably, the positive electrode active material can be selected from high-specific-capacity layered oxides (such as LiNi). 0.8 Co 0.1 Mn 0.1 O2, LiCoO2), polyanionic compounds (such as LiFePO4) or lithium-rich manganese-based materials, with a content of 60-80%, can ensure the high energy density of the battery;

[0100] Preferably, the conductive agent can be selected from carbon black (Super P), graphene, carbon nanotubes, etc., and a content of 5-10% can construct a continuous electron transport network and reduce the positive electrode electronic impedance.

[0101] Preferably, 15-25% of a halide solid electrolyte is used as an ion conductor to fill the gap between the positive electrode active material and the conductive agent.

[0102] According to certain preferred embodiments of the present invention, the surface of the negative electrode is provided with an interface modification layer, which comprises 60-80% of the halide solid electrolyte and 20-40% of metal alloy powder. The metal alloy powder is selected from lithium-based alloys such as Li-In alloy and Li-Sn alloy, or sodium-based alloys such as Na-Sn alloy. The function of the interface modification layer is to suppress interfacial side reactions between the negative electrode and the electrolyte, and to reduce interfacial impedance.

[0103] Preferably, the halide solid electrolyte is made of the same material as the bulk electrolyte, has good interfacial compatibility, and can avoid introducing new interfacial impedance.

[0104] Elements such as In and Sn in metal alloy powder can react with Li + Forming alloys (such as LiIn, Li 22 Sn5) This alloy has a higher lithiation potential than pure lithium metal, which can suppress the growth of lithium dendrites and improve battery safety; at the same time, the alloy powder has good conductivity, which can improve the electron transport efficiency of the negative electrode.

[0105] Preferably, the content of the metal alloy powder is 20-40%. This interface modification layer does not require a complex preparation process and can be formed by coating, sputtering, etc., and has good compatibility with existing anode preparation processes.

[0106] The present invention will now be described in more detail with reference to embodiments. It should be noted that these descriptions and embodiments are intended to facilitate understanding of the present invention and are not intended to limit the invention.

[0107] Example

[0108] In this invention, unless otherwise specified, all reagents used are commercially available products and are used directly without further purification. Furthermore, "%" refers to "weight %" and "parts" refers to "parts by weight".

[0109] Table 1 below lists specific information about the raw materials used in the embodiments and comparative examples of the present invention.

[0110] Table 1 List of Experimental Materials

[0111]

[0112] Table 2 below lists specific information about the experimental equipment used in the embodiments and comparative examples of the present invention.

[0113] Table 2 List of Experimental Equipment

[0114]

[0115] Performance testing methods

[0116] (a) Room temperature ionic conductivity

[0117] The room temperature ionic conductivity of solid electrolyte samples prepared in the following examples and comparative examples was tested according to the methods described below.

[0118] Specifically, referring to the national standard GB / T 39864-2021 "Test Method for Ionic Conductivity of Solid Electrolytes", the AC impedance spectroscopy method was used for testing. The specific steps are as follows: Solid electrolyte sheets were cut into 14mm diameter discs, and surface impurities were removed in an argon glove box. The film thickness (L) was accurately measured to 0.1μm. Then, the sample was clamped between two polished stainless steel blocking electrodes to create a symmetrical battery with a stainless steel blocking electrode (SS) / solid electrolyte / stainless steel blocking electrode (SS) structure. Subsequently, using an electrochemical workstation, the test temperature was set to 25℃ (room temperature), the frequency range to 1Hz-1MHz, and the AC signal amplitude to 10mV. The temperature was kept constant during the test. Then, Nyquist impedance spectra were obtained, and the bulk resistance (R) corresponding to the intersection of the high-frequency region and the real axis was read. The ionic conductivity (σ) was calculated using the formula σ = L / (R×A), where A is the effective contact area of ​​the electrode. Each sample was tested in parallel three times, and the average value was taken as the final result (unit: mS•cm). -1 ).

[0119] (II) Electrochemical stability window

[0120] Electrochemical stability window tests were performed on solid electrolyte samples prepared in the following examples and comparative examples according to the methods described below.

[0121] Specifically, referring to the relevant electrochemical performance testing specifications in the national standard GB / T 39864-2021 "Test Method for Ionic Conductivity of Solid Electrolytes", the linear sweep voltammetry (LSV) method was adopted. The specific steps are as follows: the solid electrolyte tablet was cut into 14mm diameter discs, surface impurities were removed in an argon glove box, and the thickness was accurately measured. Lithium metal foil was used as the counter electrode and reference electrode (Li / Li). + Stainless steel was used as the working electrode, and an SS / solid electrolyte / Li symmetric cell was assembled. Then, the electrochemical workstation was started, the test temperature was set to 25℃, and the scan range was 0-6V (vs. Li / Li). + The scan rate was 1 mV / s. A linear scan was initiated under argon protection, and the current-voltage (IV) curve was recorded to observe current abrupt changes. When the current density reached 10 μA / cm², the scan was completed. 2 The voltage value corresponding to the time is the upper limit of the electrochemical stability window (unit: V). The test results are expressed as 0 to the corresponding upper limit voltage. The average value is taken from 3 parallel tests.

[0122] (III) Humidity stability retention rate

[0123] The humidity stability retention rate of solid electrolyte samples prepared in the following examples and comparative examples was tested according to the methods described below.

[0124] Specifically, the solid electrolyte tablets prepared in the examples and comparative examples were pressed into discs with a diameter of 14 mm and a thickness of approximately 0.8 mm. These discs were then stored for 24 hours in an argon glove box at 25°C and a humidity of ≤1% RH to eliminate the effects of historical adsorption. Immediately after removal, their initial room temperature ionic conductivity was tested using the AC impedance method specified in the national standard GB / T 39864-2021, "Test Method for Ionic Conductivity of Solid Electrolytes". Then, the sample was placed in a programmable temperature and humidity chamber, set at a temperature of 25±1℃ and a relative humidity of 8±2% RH (simulating a typical drying room environment), and exposed continuously for 72 hours. Temperature and humidity fluctuations within the chamber were recorded every 24 hours during the process, ensuring humidity was controlled within the range of 5-10% RH. After exposure, the sample was transferred to an argon glove box, and surface cleaning was completed within 30 minutes, with the room temperature ionic conductivity immediately remeasured. .

[0125] Calculate the humidity stability retention rate using the following formula:

[0126] Each group of samples was tested in parallel three times, and the average value was taken as the final result. A retention rate of ≥80% was considered to meet the basic stability requirements, and a retention rate of ≥85% was considered to have excellent humidity stability.

[0127] Example 1 (E1)

[0128] Example 1 specifically includes the following steps:

[0129] 1. Raw material pretreatment

[0130] In an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the matrix material Li3YCl6, the main dopant (LiF and ZrBr4), and the auxiliary dopant La2O3 were placed in a vacuum drying oven and dried at 100°C for 16 hours to remove adsorbed water.

[0131] 2. Preparation of precursor solution

[0132] The pretreated solid raw materials (including 70 g of matrix material Li3YCl6, 15 g of main dopant (LiF and ZrBr4, weight ratio 1:3), and 10 g of auxiliary dopant La2O3) were transferred to a flask containing 500 g of tetrahydrofuran (THF). Under argon protection, the mixture was ultrasonically dispersed at 40 kHz for 50 minutes to obtain a suspension. Subsequently, 5 g of interface modifier hexachlorocyclotriphosphazene was added, and mechanical stirring was continued for 2 hours to obtain a pale yellow transparent precursor solution.

[0133] 3. Freeze-drying and sintering

[0134] The precursor solution was poured into a polytetrafluoroethylene dish and placed in a vacuum freeze dryer. It was freeze-dried at -40°C and 8 Pa for 36 hours to obtain a fluffy white precursor powder. This powder was then transferred to an alumina crucible and pre-sintered in a tube furnace under an argon atmosphere at a rate of 3°C / min to 250°C, holding for 3 hours to obtain a grayish-white pre-synthesized powder.

[0135] 4. Ball milling and molding

[0136] 10 g of pre-synthesized powder was placed in a ball mill jar with zirconia grinding balls (ball-to-powder ratio 30:1) and ball-milled at 400 rpm for 10 hours under argon protection. The resulting fine-grained powder was then loaded into a 20 mm diameter mold and cold-pressed under 400 MPa pressure for 5 minutes to obtain a dense solid electrolyte sheet 1 with a thickness of about 1 mm.

[0137] Test results show that the electrolyte sheet prepared in Example 1 has a room temperature ionic conductivity of 2.6 mS•cm. -1 The electrochemical stability window is 0–4.6 V (vs. Li / Li). + The humidity stability retention rate reaches 82%.

[0138] Figure 2 Scanning electron microscope (SEM) images of the solid electrolyte prepared in Example 1 are shown. SEM images show that the surface is dense, the grain boundaries are clear, and the particle size distribution is in the range of 0.5-2 μm.

[0139] Figure 3 The X-ray diffraction (XRD) pattern of the solid electrolyte prepared in Example 1 is shown. The XRD pattern shows that the product has a pure-phase halide structure.

[0140] Examples 2-12 (E2-E12) and Comparative Examples 1-5 (CE1-CE5)

[0141] Examples 2-12 (E2-E12) and Comparative Examples 1-5 (CE1-CE5) were prepared in a manner similar to that of Example 1 to prepare solid electrolyte sheets 2-12 and comparative solid electrolyte sheets 1-5, the only difference being that the component types and ratios were changed as shown in Tables 3 and 4 below.

[0142] Based on the performance testing methods described above, the room temperature ionic conductivity, electrochemical stability window, and humidity stability retention of solid electrolyte sheet 2-12 and comparative solid electrolyte sheet 1-5 were tested, and the results are shown in Tables 3 and 4 below, respectively.

[0143] Table 3. Formulation and performance test results of Examples 1-12 (E1-E12)

[0144]

[0145] Table 4. Formulation and performance test results of Comparative Examples 1-5 (CE1-CE5)

[0146]

[0147] As can be seen from the results of Examples 1-12 and Comparative Examples 1-5 in Tables 3 and 4 above, the technical solution of the present invention can significantly improve the overall performance of halide solid electrolytes.

[0148] Specifically, regarding room temperature ionic conductivity, the test results for Examples 1-12 all ranged from 2.5 to 4.2 mS•cm. -1 Within this range, it is much higher than the 1.2-2.0 mS•cm of Comparative Examples 1-5. -1 In Example 12, by optimizing the matrix material ratio (Li3YCl6: Na2ZrCl6 = 1:3) and the main dopant ratio (LiF: ZrBr4 = 1:4), a viscosity of 4.2 mS•cm was achieved. -1 The highest conductivity was significantly improved compared to traditional halide electrolytes, demonstrating the synergistic effect of lithium-based-sodium-based halide composite matrix and fluorine-bromine co-doping.

[0149] In the electrochemical window test, the products of Examples 1-12 all achieved above 0-4.5 V (vs. Li / Li). + Examples 10 and 12 further broaden the range to 0-5.0 V, meeting the application requirements of high-voltage cathode materials. However, the electrochemical window of Comparative Examples 1-5 is only 0-4.2 V at most. Furthermore, Comparative Example 2, which uses a conventional sulfide matrix, and Comparative Example 3, which contains LiPF6 dopant, have windows of only 0-3.8 V and 0-3.5 V, respectively, due to their structural limitations, resulting in significantly insufficient high-voltage stability.

[0150] Regarding humidity stability, the conductivity retention rates of Examples 1-12 were all ≥80%, with Examples 6-12 achieving a retention rate of 84%-94%, while the retention rates of Comparative Examples 1-5 were only 50%-75%. Comparative Example 4, lacking auxiliary dopants, and Comparative Example 5, lacking interface modifiers, had retention rates as low as 75% and 65%, respectively. This confirms that the synergistic effect of auxiliary dopants such as La2O3 and the hexachlorocyclotriphosphazene interface modifier can effectively inhibit electrolyte degradation in humid environments.

[0151] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from the spirit and scope of this disclosure. Therefore, if such modifications and variations fall within the scope of this invention, this disclosure is also intended to include such modifications and variations.

Claims

1. A method for producing a halide solid-state electrolyte, characterized by, The preparation method includes the following steps: (1) Under an inert atmosphere, the matrix material, main dopant and auxiliary dopant are added to an aprotic organic solvent, stirred and ultrasonically dispersed, then an interface modifier is added and stirring is continued to obtain a precursor solution; (2) The precursor solution is subjected to vacuum freeze-drying to remove the aprotic organic solvent to obtain precursor powder. The precursor powder is then sintered under an inert atmosphere to obtain pre-synthesized powder. (3) The pre-synthesized powder is mechanically ball-milled under an inert atmosphere to obtain fine-grained powder, which is then cold-pressed to obtain the halide solid electrolyte, wherein: The matrix material is selected from one or more of Li3YCl6 or Na2ZrCl6; The main dopant is a mixture of fluoride and bromide in a weight ratio of 1:3 to 1:6, wherein the fluoride is selected from at least one of LiF, NaF and AlF3, and the bromide is selected from at least one of LiBr, NaBr and ZrBr4; The auxiliary dopant is selected from at least one of La2O3, In2O3 and MgO; The interface modifier is hexachlorocyclotriphosphazene; Based on the total weight of the matrix material, the main dopant, the auxiliary dopant, and the interface modifier as 100%, the content of the matrix material is 70-85%, the content of the main dopant is 5-15%, the content of the auxiliary dopant is 3-10%, and the content of the interface modifier is 2-8%.

2. The method for preparing halide solid electrolyte according to claim 1, characterized in that, The matrix material is a mixture of Li3YCl6 and Na2ZrCl6 in a weight ratio of 1:2 to 1:

5.

3. The method for preparing a halide solid electrolyte according to claim 1, characterized in that, The main dopant is a mixture of LiF and ZrBr4 in a weight ratio of 1:3 to 1:

5.

4. The method for preparing a halide solid electrolyte according to claim 1, characterized in that, The aprotic organic solvent is selected from at least one of tetrahydrofuran, ethylene glycol dimethyl ether, and propylene carbonate.

5. The method for preparing a halide solid electrolyte according to claim 1, characterized in that, The ratio of the total weight of the matrix material, the main dopant, the auxiliary dopant, and the interface modifier to the weight of the aprotic organic solvent is in the range of 1:5 to 1:

10.

6. The method for preparing the halide solid electrolyte according to claim 1, characterized in that, The vacuum freeze-drying in step (2) is carried out at a temperature of -50 to -30°C, a vacuum degree of ≤ 10Pa, and a time of 24-48 hours.

7. The method for preparing a halide solid electrolyte according to claim 1, characterized in that, The sintering temperature in step (2) is 200-300℃, the heating rate is 2-5℃ / min, and the holding time is 2-4 hours.

8. A halide solid electrolyte, characterized in that, The halide solid electrolyte is prepared by the method according to any one of claims 1-7.

9. A solid-state battery, characterized in that, The solid-state battery includes: positive electrode; negative electrode; The halide solid electrolyte according to claim 8.

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