Modified solid-state electrolyte and preparation method thereof, solid-state battery

Abstract

The application discloses a modified solid-state electrolyte and a preparation method and a solid-state battery thereof. The preparation method comprises the following steps: providing a first component and a second component for forming a binary halide solid-state electrolyte matrix, the chemical general formula of the binary halide solid-state electrolyte matrix is Li3InR6, R comprises one or more of Cl, Br, I and F, and a third component for modifying the structure of the binary halide solid-state electrolyte matrix; mixing the first component, the second component and the third component, performing a first solid-phase reaction to prepare a precursor powder; performing cold pressing treatment on the precursor powder to prepare a cold-pressed forming body; and performing heat treatment on the cold-pressed forming body to perform a second solid-phase reaction to prepare the modified solid-state electrolyte. The preparation method can introduce the third component into the binary halide matrix while effectively reducing the high energy consumption required for introducing the third component for modification, and also avoids the adverse effects caused by long-time high-temperature sintering.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, specifically to a modified solid electrolyte and its preparation method, and a solid-state battery. Background Technology

[0002] All-solid-state lithium batteries, as next-generation energy storage devices, have attracted widespread attention due to their potential for high safety and high energy density. Among them, halide solid electrolytes, such as binary bismuth chloride-based electrolytes (e.g., Li3InCl6) based on LiCl and InCl3, have become important candidate materials due to their high oxidation stability and good compatibility with high-voltage cathodes. These materials are usually prepared using traditional methods such as solid-state synthesis and exhibit certain cycle stability when matched with cathodes such as LiCoO2. However, with the increasing demands on the performance of all-solid-state batteries, on the one hand, existing binary bismuth chloride-based electrolyte systems face performance bottlenecks due to insufficient intrinsic ionic conductivity and inadequate interfacial stability with lithium metal anodes, leading to increased interfacial impedance and battery failure; on the other hand, the incorporation of a third component for optimization purposes requires high-energy-consuming processes to overcome interfacial compatibility issues between components. Summary of the Invention

[0003] In view of this, this application provides a modified solid electrolyte and its preparation method, as well as a solid battery, to solve the above-mentioned technical problems.

[0004] To achieve the above objectives, in a first aspect, this application provides a method for preparing a modified solid electrolyte, the method comprising: providing a first component and a second component for forming a binary halide solid electrolyte matrix, the binary halide solid electrolyte matrix having the general chemical formula Li3InR6, where R includes one or more of Cl, Br, I, and F; and a third component for structurally modifying the binary halide solid electrolyte matrix; mixing the first component, the second component, and the third component, and performing a first solid-phase reaction to prepare a precursor powder; cold-pressing the precursor powder to prepare a cold-pressed body; and heat-treating the cold-pressed body to perform a second solid-phase reaction to prepare the modified solid electrolyte.

[0005] Based on the first aspect, in some embodiments, mixing is carried out by ball milling to conduct the first solid-phase reaction, with the ball milling speed being 400 rpm to 600 rpm and the ball milling time being 9 h to 16 h.

[0006] Based on the first aspect, in some embodiments, the pressure of the cold pressing process is from 100 MPa to 300 MPa.

[0007] Based on the first aspect, in some embodiments, the heat treatment temperature is 250 °C to 300 °C.

[0008] Based on the first aspect, in some embodiments, the heat treatment time is 1 h to 3 h.

[0009] Based on the first aspect, in some embodiments, the heating rate of the heat treatment is from 2 °C / min to 5 °C / min.

[0010] Based on the first aspect, in some embodiments, the first component includes lithium halide.

[0011] Based on the first aspect, in some embodiments, the second component includes indium halide.

[0012] Based on the first aspect, in some embodiments, the third component includes an oxygen-containing lithium source.

[0013] Based on the first aspect, in some embodiments, the first component includes lithium chloride, the second component includes indium chloride, and the third component includes lithium oxide.

[0014] Based on the first aspect, in some embodiments, the molar ratio of lithium chloride, indium chloride and lithium oxide is (2.8~3.2):1:(0.05~0.25).

[0015] Secondly, this application provides a modified solid electrolyte, which is prepared by the above-described preparation method.

[0016] Based on the second aspect, in some embodiments, the chemical formula of the modified solid electrolyte is Li. 3+2x InCl6O x , 0.05≤x≤0.25.

[0017] Based on the second aspect, in some embodiments, the modified solid electrolyte has equiaxed grains bonded together, the size of which is 1 μm to 5 μm.

[0018] Based on the second aspect, in some embodiments, the modified solid electrolyte has an ionic conductivity of 1.8 mS / cm at room temperature. -1 Up to 2.5 mS cm -1 .

[0019] Based on the second aspect, in some embodiments, the critical current density of the modified solid electrolyte and the lithium metal anode is greater than or equal to 0.8 mA cm⁻¹. -2 .

[0020] Thirdly, this application provides a solid-state battery comprising the modified solid-state electrolyte described above.

[0021] The preparation method of this application introduces a third component to modify the binary halide matrix through a specific process. The first solid-phase reaction is carried out by mixing, which helps to form a precursor powder with more uniform chemical properties and a uniform distribution of reactive sites. This achieves uniform pre-activation and dispersion of the third component at the molecular scale, thereby reducing the risk of component segregation and the formation of non-target impurity phases. The cold-pressed body is prepared by cold pressing, which constructs a high-density, closely contacted reaction precursor configuration at room temperature. This helps to shorten the diffusion path of substances in subsequent heat treatment, so that the solid-phase reaction, which originally required high temperature and high pressure, can be carried out at a lower heat treatment temperature and at normal pressure (or low pressure). This helps to reduce the activation energy and process severity required for subsequent solid-phase reactions. Then, the second solid-phase reaction is carried out by heat treatment, which allows for a full solid-phase reaction. This promotes the efficient and quantitative entry of the third component (such as oxygen) into the target lattice position to form a solid solution, resulting in a product with uniform grain size, clean grain boundaries, and dense microstructure. Moreover, under the specific process design of this application, the above heat treatment is carried out at a lower temperature, without the need for long-term high temperature or special atmosphere conditions. Therefore, the preparation method of this application can effectively reduce the high energy consumption required for the modification of the third component while introducing the third component into the binary halide matrix. This is beneficial to improving the controllability of the process and reducing the process cost. At the same time, it avoids the loss of volatile components, abnormal coarsening of grains, and structural defects caused by uncontrolled reaction kinetics that may be caused by long-term high-temperature sintering. Attached Figure Description

[0022] Figure 1 The XRD patterns of the precursor powder provided in Comparative Example 1, the precursor powder provided in Example 1, and the modified solid electrolyte provided in Example 1 are shown.

[0023] Figure 2 This is an SEM image of the modified solid electrolyte provided in Example 1 of this application.

[0024] Figure 3 The XRD patterns of the modified solid electrolytes provided in Comparative Examples 1-4 of this application are shown. Detailed Implementation

[0025] To facilitate understanding of the technical solutions of this application, a more comprehensive description of the technical solutions of this application will be provided below with reference to the accompanying drawings, which illustrate preferred embodiments of the technical solutions of this application. However, the technical solutions of this application can be implemented in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and comprehensive understanding of the disclosure of the technical solutions of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] Currently, the LiCl-InCl3 binary system faces bottlenecks in further reducing the lithium-ion migration barrier due to the structural characteristics of the binary components themselves. Optimizing traditional synthesis processes is insufficient to improve ionic conductivity, thus failing to meet the demands of high-rate applications. Meanwhile, the In content in the binary electrolyte... 3+ Thermodynamic instability leads to severe interfacial side reactions when it comes into contact with lithium metal anodes, generating a high-resistivity decomposition layer. Attempts to improve the interfacial problem by simply adding a third component often fail to achieve precise control and stable binding of the component in the interfacial region during the preparation process, resulting in limited interfacial modification effects and even sacrificing bulk conductivity or cathode compatibility.

[0028] This study found that if a third component is introduced to synergistically regulate bulk ion conduction and interfacial stability, firstly, the physicochemical properties of the third component (such as melting point, reactivity, and volatility) may differ significantly from the original binary system. Simple mechanical mixing and heat treatment can easily lead to uneven component distribution, local segregation, or the formation of non-target impurity phases, making it difficult to obtain a single, pure target phase. Secondly, the synthesis reaction kinetics of the ternary system are more complex and extremely sensitive to process parameters such as reaction temperature, time, atmosphere, and precursor state. Even slight deviations can lead to crystal structure defects, a surge in grain boundary impedance, or blockage of ion migration channels, which is detrimental to improving ion conductivity. In related technologies, long-term high-temperature sintering is usually required to promote the effective incorporation of the third component and achieve stable interfacial bonding, thereby fully leveraging the modification effect of the third component on the binary system. However, such preparation processes are energy-intensive, increase the difficulty and uncontrollability of process control, and increase the overall manufacturing cost of materials, which is not conducive to the large-scale application of bismuth chloride-structured electrolytes. Therefore, there is still a lack of controllable, stable and highly reproducible synthesis methods for the above ternary systems.

[0029] Based on this, the present application improves the preparation method of the modified solid electrolyte, so as to achieve effective incorporation of the third component with lower energy consumption and promote the formation of stable interfacial bonding between components, thereby improving the controllability, stability and repeatability of the preparation of the above ternary system and reducing the preparation cost.

[0030] Based on this, one embodiment of this application provides a method for preparing a modified solid electrolyte, the method comprising:

[0031] Step 1: Provide a first component and a second component for forming a binary halide solid electrolyte matrix, the general chemical formula of which is Li3InR6, where R includes one or more of Cl, Br, I, and F, and a third component for structural modification of the binary halide solid electrolyte matrix. Mix the first component, the second component, and the third component to carry out a first solid-phase reaction to prepare a precursor powder.

[0032] In related technologies, raw material components are typically subjected to high-temperature treatment after simple physical mixing. This application's research found that when the physicochemical properties of the third component differ from those of the first and second components, simple mixing easily leads to uneven distribution. To promote effective incorporation of the third component and achieve stable interfacial bonding, a longer high-temperature sintering time is required. Therefore, the preparation method of this application introduces the third component to modify the binary halide matrix through a specific process. Firstly, mixing is used to carry out a first solid-phase reaction, which helps to form a precursor powder with more uniform chemical properties and a more even distribution of reactive sites. This achieves uniform pre-activation and dispersion of the third component at the molecular scale, thereby reducing the risk of component segregation and the formation of non-target impurity phases.

[0033] It should be noted that the essence of a solid-phase reaction is the disappearance of the old phase and the formation of a new phase. In this application, the first solid-phase reaction can be characterized by XRD of the precursor powder obtained after mixing, and compared with the standard cards of the first, second and third components. The results show that new diffraction peaks appear, and the intensity of the characteristic peaks of the original raw materials is significantly weakened or even disappears, indicating that the first solid-phase reaction has occurred and a new crystalline phase has been formed.

[0034] In some embodiments, mixing is performed by ball milling to carry out the first solid-phase reaction, with the ball milling speed ranging from 400 rpm to 600 rpm and the milling time ranging from 9 h to 16 h. For example, the ball milling speed can be 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm, 500 rpm, 520 rpm, 540 rpm, 560 rpm, 580 rpm, 600 rpm, or any value within the range of any two of the above values. The ball milling time can be 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h, 14 h, 14.5 h, 15 h, 15.5 h, 16 h, or any value within the range of any two of the above values. Mixing by ball milling and controlling the ball milling speed and time within the above ranges helps to promote the mixing of raw materials and promote the first solid-phase reaction. This approach helps reduce the risk that lower ball milling speeds may not provide sufficient mechanical energy to initiate initial solid-phase reactions and achieve uniform dispersion, while higher speeds may generate excessive heat, leading to localized overheating or unexpected phase transitions in the precursor. Shorter ball milling times may result in insufficient activation and inadequate component homogeneity, while longer milling times reduce efficiency and may introduce excessive impurities (from ball milling media wear). Therefore, controlling these ball milling conditions achieves a balance between energy input and reaction uniformity, resulting in highly active and uniformly composed precursor powders. This provides a reliable foundation for subsequent low-temperature, low-pressure reactions, further improving process repeatability and batch stability.

[0035] In some embodiments, the first component includes lithium halides. For example, the first component may include, but is not limited to, lithium chloride, lithium fluoride, lithium bromide, or lithium iodide. In some embodiments, the second component includes indium halides. For example, the second component may include, but is not limited to, indium chloride, indium fluoride, indium bromide, or indium iodide. Lithium halides and indium halides have high reactivity, but they also have relatively poor thermal stability and are prone to volatilization or decomposition at high temperatures. The high-temperature and high-pressure processes (such as hot-pressing sintering) used in related technologies to introduce the third component can easily exacerbate the volatilization loss of such raw materials, leading to non-stoichiometric products and the formation of porosity defects, which in turn degrades performance. The preparation method of this application can pre-activate lithium halides and indium halides at the molecular scale by carrying out a first solid-phase reaction, so that they form a uniform precursor powder with the third component, reducing the dependence of subsequent complete reaction on high temperature. The subsequent cold pressing process significantly increases the contact density between precursor particles at room temperature, creating a short path for halide ions to diffuse at medium and low temperatures. Low-temperature heat treatment (250 ℃~300 ℃) within a temperature window below the point of violent halide volatilization gently and fully completes the second solid-phase reaction. Therefore, for binary matrices composed of the specific, classic, but heat-sensitive combination of lithium halides and indium halides, the modification process achieved by the method in this application helps maintain the stoichiometry of the raw materials, reduces thermal damage, and promotes the efficient and uniform incorporation of the third component into the matrix. This more effectively optimizes the inherent ionic conductivity bottleneck and interfacial instability problems of this binary system. This preparation method has significant advantages in solving this type of classic halide electrolyte system.

[0036] In some embodiments, the third component includes an oxygen-containing lithium source. For example, the third component may include, but is not limited to, lithium oxide, lithium carbonate, lithium hydroxide or its hydrate (LiOH·H2O), lithium nitrate, or lithium oxalate. These compounds decompose during heat treatment, releasing the Li2O active component and participating in the solid-state reaction. Choosing an oxygen-containing lithium source as the third modifying component allows for the simultaneous introduction of an additional lithium source while providing oxygen for lattice doping. This helps maintain or adjust the overall lithium stoichiometry of the final product and reduces the adverse effects of excess lithium vacancies caused by doping. Based on this, the preparation method of this application provides a better process route for the efficient and stable introduction and modification of binary halide solid electrolyte substrates using oxygen-containing lithium sources. Specifically, in the mixing and first solid-phase reaction stage, the oxygen-containing lithium source and the first and second components (such as halides) are uniformly mixed in the solid state and undergo mechanochemical activation. This allows the oxygen-containing lithium source and halides, which originally had significantly different chemical properties, to achieve close contact and pre-reaction at the molecular and atomic scale. This helps to reduce the interfacial energy barrier between oxygen and halides, generating a precursor powder with uniformly distributed reactive sites. This helps to solve the problem of the difficulty in directly and uniformly dispersing the oxygen-containing lithium source due to its different physicochemical properties from those of the halides. The subsequent cold pressing process presses the precursor powder into a high-density cold-pressed body at room temperature, which helps to further eliminate the particle size of the oxygen-containing lithium source and the matrix raw material. The gaps between particles form a tight contact interface and a highly dense microstructure, which helps to shorten the mass transfer path of oxygen ions diffusing into the halide lattice and undergoing substitution reactions during subsequent heat treatment. This allows the reaction driving force to be effectively utilized at lower temperatures. During the second solid-phase reaction through heat treatment, thanks to the excellent initial state of uniform activation and tight contact created in the first two steps, the solid-phase reaction between the oxygen-containing lithium source and the binary halide matrix can proceed fully at relatively low temperatures (e.g., 250-300℃) and atmospheric (or low) pressure conditions. This facilitates the quantitative and controllable entry of oxygen from the oxygen-containing lithium source into specific positions in the target halide lattice (e.g., partial substitution of Cl). - This forms a uniform oxygen halide solid solution, thereby reducing the impurities caused by the decomposition of the oxygen-containing lithium source itself, excessive loss of volatile halide components, or uncontrolled rapid reaction during long-term high-temperature processing.

[0037] In some embodiments, the first component comprises lithium chloride, the second component comprises indium chloride, and the third component comprises lithium oxide. Chloride systems possess relatively high ionic conductivity potential and moderate chemical stability. Lithium oxide, as the third component, can directly participate in the solid-phase reaction during the reaction process, reducing the generation of gaseous byproducts (such as CO2, H2O, etc.), thereby improving the compactness and phase purity of the product and reducing microstructural defects caused by gas escape. Furthermore, in this application, lithium oxide has a high melting point, making it suitable for low-temperature processes. It remains solid during subsequent heat treatment at 250-300°C, reducing the risk of premature melting or violent decomposition of the third component. This allows it to match the low-temperature and gentle process window of this application, achieving uniform and controllable oxygen doping. This specific combination, prepared using the method of this application, exhibits high reaction compatibility and phase-forming ability under low energy consumption conditions, thus facilitating the formation of high-performance Li. 3+2x InCl6O x Solid solution.

[0038] In some embodiments, the molar ratio of lithium chloride, indium chloride, and lithium oxide is (2.8~3.2):1:(0.05~0.25). For example, taking the molar number of indium chloride as 1, the molar number of lithium chloride can be 2.8, 2.9, 3, 3.1, 3.2, or any value within the range of any two of the above values, and the molar number of lithium oxide can be 0.05, 0.1, 0.15, 0.2, 0.25, or any value within the range of any two of the above values. Controlling the molar ratio of lithium chloride, indium chloride, and lithium oxide within the above range helps to regulate the chemical composition of the final product. Specifically, a Li:In ratio around a stoichiometric ratio of 3:1 is beneficial for promoting the stable formation of the main crystalline phase of bismuth chloride ore. The molar amount of lithium oxide (corresponding to the x value) affects the oxygen doping amount in the final product. Controlling the above doping amount helps to promote the synergistic improvement of high ionic conductivity and excellent interface stability, and helps to reduce the risk of insignificant modification effects when the doping amount is low, or the risk of impurity phase precipitation damaging the single-phase structure and performance when the doping amount is high.

[0039] In some embodiments, the molar ratio of lithium chloride, indium chloride, and lithium oxide is 3:1:(0.1~0.2). For example, the molar ratio of lithium chloride, indium chloride, and lithium oxide can be 3:1:0.1, 3:1:0.11, 3:1:0.12, 3:1:0.13, 3:1:0.14, 3:1:0.15, 3:1:0.16, 3:1:0.17, 3:1:0.18, 3:1:0.19, 3:1:0.2, or any value within the range of any two of the above values. Further controlling the molar ratio of lithium chloride, indium chloride, and lithium oxide within the above range is beneficial for further promoting the synergistic improvement of high ionic conductivity and excellent interfacial stability.

[0040] Step 2: Cold press the precursor powder to prepare a cold-pressed molded body.

[0041] In related technologies, high-temperature hot pressing is typically used to promote diffusion and bonding between components, which is energy-intensive and requires demanding equipment. This application discovers a method that introduces cold pressing before heat treatment, compressing precursor powder into a cold-pressed body at room temperature to achieve close particle packing. This cold-pressed body has a high-density, low-porosity microstructure, with particle bonding primarily relying on mechanical and van der Waals forces, without high-temperature driven chemical diffusion and grain boundary fusion. Therefore, the phase composition and reactivity of the precursor are fully preserved. This cold-pressed body is in a transitional state between loose powder and the final sintered body, providing a good reactive precursor for subsequent low-temperature heat treatment.

[0042] This close physical contact helps to shorten the diffusion path of substances in subsequent heat treatment, allowing solid-phase reactions that originally required high temperature and high pressure to proceed to be carried out at lower heat treatment temperatures and at normal (or low) pressure.

[0043] In some embodiments, the cold pressing pressure is between 100 MPa and 300 MPa. For example, the cold pressing pressure can be 100 MPa, 120 MPa, 140 MPa, 160 MPa, 180 MPa, 200 MPa, 220 MPa, 240 MPa, 260 MPa, 280 MPa, 300 MPa, or any value within the range of any two of the above values. Controlling the cold pressing pressure within the above range helps to obtain high-density cold-pressed articles while reducing the risk of excessive equipment wear or adverse plastic deformation of the powder. It is beneficial to reduce the risk of insufficient density of the cold-pressed article and insufficient interparticle contact at lower pressures, which may prevent the effective shortening of subsequent diffusion paths. It also reduces the risk of drastically increased equipment requirements at higher pressures, which may lead to the breakage of brittle powder particles, excessive fine powder, or internal stress (which is detrimental to subsequent uniform solid-state reactions). Therefore, by controlling the above-mentioned cold pressing conditions, it is possible to prepare embryos with better initial density and microscopic contact morphology with reasonable equipment costs and energy consumption, which is beneficial to further reduce the activation energy required for subsequent reactions.

[0044] Step 3: Heat-treat the cold-pressed body to carry out the second solid-phase reaction and prepare the modified solid electrolyte.

[0045] By conducting heat treatment and a second solid-phase reaction, a sufficient solid-phase reaction is achieved, thereby promoting the efficient and quantitative entry of the third component (such as oxygen) into the target lattice site to form a solid solution. This results in a product with uniform grain size, clean grain boundaries, and a dense microstructure. Furthermore, under the specific process design of this application, the heat treatment is carried out at a lower temperature, eliminating the need for prolonged high temperatures or special atmospheres. Therefore, the preparation method of this application can effectively reduce the high energy consumption required for the modification of the third component while introducing it into the binary halide matrix. This improves process controllability and reduces process costs. At the same time, it avoids the loss of volatile components (such as indium and lithium), abnormal grain coarsening, and structural defects caused by uncontrolled reaction kinetics that may result from prolonged high-temperature sintering.

[0046] It should be noted that the essence of a solid-state reaction is the disappearance of the old phase and the formation of a new phase. In this application, the second solid-state reaction can be characterized by XRD, which shows the appearance of new diffraction peaks and the significant weakening or even disappearance of the characteristic peaks of the original raw materials, indicating that a second solid-state reaction has occurred and a new crystalline phase has been formed.

[0047] In some embodiments, the heat treatment temperature is between 250°C and 300°C. For example, the heat treatment temperature can be 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C, 300°C, or any value within the range of any two of the above values. In related technologies, hot pressing sintering at 800°C to 1200°C is required to promote the effective incorporation of the third component and achieve stable bonding at the interface. However, under the specific process design of this application, the above heat treatment is performed at a lower temperature of 250°C to 300°C. Controlling the heat treatment temperature within the above range not only reduces energy consumption, simplifies equipment requirements, and improves production safety, giving the preparation method a cost advantage on a large scale, but also helps to significantly reduce the loss of volatile components because the process temperature is lower than that required for the violent volatilization of halides such as indium and lithium. This facilitates quantitative doping, ensures the stoichiometric accuracy of the product, and helps to regulate the product performance.

[0048] In some embodiments, the heat treatment time is from 1 h to 3 h. For example, the heat treatment time can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, or any value within the range of any two of the above values. Combined with an optimized heat treatment temperature, controlling the heat treatment time within the above range is sufficient to ensure that the solid-phase reaction proceeds fully, forming a complete solid solution structure, while reducing the risk of uneven doping due to shorter reaction times or excessive grain growth due to longer reaction times. The aforementioned short-time treatment further reduces the overall energy consumption.

[0049] In some embodiments, the heating rate of the heat treatment is from 2 °C / min to 5 °C / min. For example, the heating rate of the heat treatment is 2 °C / min, 2.3 °C / min, 2.6 °C / min, 2.9 °C / min, 3.2 °C / min, 3.5 °C / min, 3.8 °C / min, 4.1 °C / min, 4.4 °C / min, 4.7 °C / min, 5 °C / min, or any value within the range of any two of the above values. Controlling the heating rate of the heat treatment within the above range allows for a uniform temperature rise inside the cold-pressed body, reducing the generation of microcracks caused by thermal stress. This heating rate, combined with low temperature and short holding time, constitutes a mild and efficient heat treatment regime, which is beneficial for obtaining products with uniform microstructure and few defects.

[0050] An embodiment of this application also provides a modified solid electrolyte, which is prepared by the above-described preparation method.

[0051] The modified solid electrolyte prepared by the method described in this application possesses both excellent bulk ion transport performance and interfacial stability. Specifically, because the preparation method of this application avoids harsh conditions such as high temperature and high pressure, the resulting electrolyte has the characteristics of precise stoichiometry, uniform and dense microstructure, and clean grain boundaries. Therefore, it is beneficial to improve the ionic conductivity of the obtained modified solid electrolyte and the stable, low-impedance interface with the lithium metal anode.

[0052] Understandably, this application does not particularly limit the macroscopic form of the modified solid electrolyte product prepared by the above preparation method and its application. It can be a sheet-like form obtained after heat treatment, or a powder form obtained by crushing the sheet-like form.

[0053] In some embodiments, the chemical formula of the modified solid electrolyte is Li 3+2x InCl6O xThe oxygen content is 0.05 ≤ x ≤ 0.25. The partial substitution of chlorine by oxygen in the bismuth chloride lattice optimizes the lithium-ion migration pathway at the atomic scale, effectively lowering the energy barrier for lithium-ion migration and thus laying the structural foundation for high ionic conductivity. Simultaneously, appropriate oxygen doping (x values ​​between 0.05 and 0.25) helps stabilize the crystal structure, reducing harmful phase transitions or compositional segregation during cycling, thereby contributing to the long-term electrochemical stability of the material.

[0054] In some embodiments, the modified solid electrolyte has intergathered equiaxed grains with a size of 1 μm to 5 μm. For example, the size of the equiaxed grains can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any value within the range of any two of the above values. The uniform equiaxed grains and dense bonding indicate that the reaction and grain growth process of the modified solid electrolyte obtained by the method of this application is uniform and controlled, with less abnormal grain coarsening or anisotropic growth, which is beneficial to the improvement of ionic conductivity (clear grain boundaries, low impedance) and the maintenance of mechanical strength.

[0055] In some embodiments, the modified solid electrolyte has an ionic conductivity of 1.8 mS / cm at room temperature. -1 Up to 2.5 mScm -1 For example, the ionic conductivity of a modified solid electrolyte at room temperature can be 1.8 mS / cm. -1 1.9 mS cm -1 2 mScm -1 2.1 mS cm -1 2.2 mS cm -1 2.3 mS cm -1 2.4 mS cm -1 2.5 mS cm -1 Or any value within the range of any two of the above values. The modified solid electrolyte of this application introduces a third component (such as Li2O) into a binary bismuth chloride structure electrolyte matrix (such as Li3InCl6) based on LiCl and InCl3, providing lattice distortion and additional lithium vacancies to the matrix, thereby providing a better channel for lithium ion migration. As a result, the ionic conductivity of the modified solid electrolyte at room temperature is improved to the above range compared with that of traditional halide solid electrolytes, which is beneficial to reducing the internal resistance of the solid-state battery used and lays the material foundation for manufacturing high-rate, fast-charging all-solid-state batteries.

[0056] In some embodiments, the critical current density of the modified solid electrolyte and the lithium metal anode is greater than or equal to 0.8 mA cm⁻¹. -2The modified solid electrolyte of this application, by introducing a third component (such as Li₂O) into a binary bismuth chloride-based electrolyte matrix (such as Li₃InCl₆) based on LiCl and InCl₃, can induce the formation of a uniform, stable, and Li₂O- and LiCl-rich ion-conducting interfacial layer (SEI) at the electrolyte / lithium interface. This interfacial layer can effectively prevent In… 3+ Direct contact with lithium prevents its reduction. Test data from lithium-lithium symmetric batteries demonstrate that batteries using the electrolyte of this invention can achieve a critical current density (CCD) exceeding 0.8 mA cm⁻¹. -2 Thus, it can be achieved at 0.2 mA cm -2 It can cycle stably for more than 1000 hours at current density without any signs of short circuit, and the interface impedance remains stable.

[0057] It should be noted that the modified solid electrolyte of this application also exhibits excellent high-voltage cathode stability. Experiments have confirmed that the modified solid electrolyte of this application, while maintaining or even slightly improving its compatibility with 4.3 V-level high-voltage cathodes (such as high-nickel ternary electrodes), also improves its stability with lithium anodes. This means that within a single electrolyte material system, the triple objectives of high ionic conductivity, excellent lithium metal anode compatibility, and good high-voltage cathode stability are simultaneously achieved, overcoming the contradictions that are difficult to reconcile in traditional solid electrolytes.

[0058] One embodiment of this application also provides a solid-state battery, which includes the modified solid-state electrolyte described above.

[0059] The solid electrolyte of this application includes the modified solid electrolyte described above, which has the characteristics of high ionic conductivity, high interfacial stability and high safety, thus outperforming batteries made using conventional electrolytes in terms of rate performance, cycle life and safety.

[0060] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0061] Example 1:

[0062] A method for preparing a modified solid electrolyte, the method comprising:

[0063] Step 1: Place 0.614 g lithium chloride, 1 g indium chloride, and 0.014 g lithium oxide in the ball mill jar of a high-energy planetary ball mill. The molar ratio of lithium chloride, indium chloride, and lithium oxide is 3:1:0.1. Add an appropriate amount of zirconium balls as the ball milling medium. After loading the sample in a glove box protected by an inert gas (such as argon), mechanical ball milling is performed at a speed of 500 rpm for 12 h to carry out the first solid-phase reaction and prepare the precursor powder.

[0064] Step 2: Remove the precursor powder from the ball mill jar, weigh an appropriate amount of powder in the glove box, place it in a mold (diameter Φ=10 mm), and cold press it under a pressure of 100 MPa to produce a dense cold-pressed sheet.

[0065] Step 3: Place the cold-pressed sheet in a sealed crucible and, under the protection of a high-purity inert gas (such as argon), place it in a tube furnace for programmed temperature rise sintering. The sintering program is as follows: heat to a sintering temperature of 290 ℃ at a heating rate of 3 ℃ / min, hold at this temperature for 2 h, and then cool to room temperature with the furnace to obtain the modified solid electrolyte. Depending on the actual application requirements, the obtained modified solid electrolyte can be pulverized before use.

[0066] Example 2:

[0067] The difference from Example 1 is that the molar ratio of lithium chloride, indium chloride and lithium oxide is adjusted to 3:1:0.2.

[0068] Example 3:

[0069] The difference from Example 1 is that the pressure of the cold pressing process is adjusted to 200 MPa.

[0070] Example 4:

[0071] The difference from Example 1 is that the pressure of the cold pressing process is adjusted to 300 MPa.

[0072] Example 5:

[0073] The difference from Example 1 is that the sintering temperature was adjusted to 250 °C.

[0074] Example 6:

[0075] The difference from Example 1 is that the sintering temperature was adjusted to 300 °C.

[0076] Example 7:

[0077] The difference from Example 1 is that the first component is lithium bromide, the second component is indium chloride, and the third component is lithium oxide, with a molar ratio of 3:1:0.1. The remaining steps are the same as in Example 1 to prepare the modified solid electrolyte.

[0078] Example 8:

[0079] The difference from Example 1 is that the first component is lithium chloride, the second component is indium bromide, and the third component is lithium oxide, with a molar ratio of 3:1:0.1. The remaining steps are the same as in Example 1 to prepare the modified solid electrolyte.

[0080] Comparative Example 1:

[0081] A method for preparing a modified solid electrolyte, the method comprising:

[0082] Step 1: Simply blend the raw materials lithium chloride, indium chloride and lithium oxide, using the same amount of raw materials as in Example 1, to obtain precursor powder.

[0083] Step 2: The precursor powder from Step 1 is placed in a tube furnace under the protection of a high-purity inert gas (such as argon) for programmed temperature sintering. The sintering procedure is the same as in Example 1, to obtain the modified solid electrolyte.

[0084] Comparative Example 2:

[0085] A method for preparing a modified solid electrolyte, the method comprising:

[0086] Step 1: Simply blend the raw materials lithium chloride, indium chloride and lithium oxide, using the same amount of raw materials as in Example 1, to obtain precursor powder.

[0087] Step 2: The precursor powder from Step 1 is placed in a tube furnace under an oxygen atmosphere for programmed temperature sintering. The difference between the sintering program and Example 1 is that the sintering temperature is adjusted to 1000 ℃ and the holding time is adjusted to obtain the modified solid electrolyte.

[0088] Comparative Example 3:

[0089] The difference from Example 1 is that the second step is omitted, and the precursor powder obtained in the first step is directly subjected to the sintering heat treatment in the third step.

[0090] Comparative Example 4:

[0091] The difference from Example 1 is that the first step is adjusted to: simply blending the raw materials lithium chloride, indium chloride and lithium oxide to obtain precursor powder.

[0092] Taking Example 1 and Comparative Example 1 as examples, this application tested the precursor powders obtained in the first step of Example 1 and Comparative Example 1 using an X-ray diffractometer (model: Bruker D8 ADVANCE). Please refer to [link to relevant documentation]. Figure 1In Example 1, the precursor powder obtained after ball milling showed a significant decrease in the characteristic diffraction peaks of the raw materials LiCl, InCl3, and Li2O, while a broad diffraction peak corresponding to the Li3InCl6 phase appeared, indicating that a pre-solid phase reaction occurred during ball milling, forming a partially reacted intermediate product. In contrast, the precursor powder obtained by simple blending in Comparative Example 1 showed sharp diffraction peaks for LiCl, InCl3, and Li2O, as well as other phases, but no diffraction signal for Li3InCl6 was observed. This indicates that the precursor powder of Example 1 underwent a pre-solid phase reaction (first solid phase reaction), while the simple blending of the three raw materials in the precursor powder of Comparative Example 1 did not result in any detected reaction.

[0093] Taking Example 1 as an example, this application analyzes the obtained modified solid electrolyte using an X-ray diffractometer. Please refer to the previous section for further details. Figure 1 XRD patterns showed that the main diffraction peaks of the obtained product were basically consistent with the standard crystal phase of Li3InCl6, with no obvious peak shift, indicating that oxygen doping did not change the main lattice structure of indium chloride ore; at the same time, with Figure 1 A comparison of the spectra of the precursor powder in Comparative Example 1 shows that no residual peaks of raw materials such as LiCl, InCl3, or Li2O were detected in the spectra of the modified solid electrolyte of Example 1, nor were any other impurity phase peaks observed, indicating that oxygen had been successfully incorporated into the crystal lattice to form a single solid solution phase. Furthermore, compared to the pure phase Li3InCl6, the diffraction peaks of the product showed a slight shift, attributed to microscopic strain caused by oxygen doping, further confirming the entry of oxygen into the crystal lattice. This application also analyzed the obtained modified solid electrolyte using a scanning electron microscope (Hitachi SU8010). Please refer to [link to relevant documentation]. Figure 2 SEM images show that the obtained modified solid electrolyte consists of grains ranging from 1 μm to 5 μm in size. The grains are tightly bonded, with clear grain boundaries, and the microstructure is uniform and dense, without obvious pores or abnormally large grains. This uniform microstructure helps to reduce grain boundary impedance and improve the ionic conductivity of the material.

[0094] Please see Figure 3 X-ray diffraction analysis of the modified solid electrolytes of Comparative Examples 1-4 in this application showed that Comparative Example 1 clearly generated Li3In, Comparative Example 2 generated Li3In and In metal, Comparative Example 3 generated a small amount of Li3In, and Comparative Example 4 clearly generated Li3In. This indicates that the modified solid electrolytes of Comparative Examples 1-4 all have impurity phases, which are not conducive to the structural stability of solid electrolytes.

[0095] The modified solid electrolytes obtained in Examples 1-8 and Comparative Examples 1-4 were subjected to the following performance tests:

[0096] 1. Electrochemical Impedance Testing: An electrochemical workstation was used to perform AC impedance testing on the samples at room temperature, with a frequency range of 1 Hz to 7 MHz and an AC amplitude of 10 mV. The ionic conductivity of the samples was calculated by impedance spectroscopy fitting.

[0097] 2. Electrochemical performance testing of lithium symmetric batteries: The modified solid electrolyte was assembled into a Li|electrolyte|Li symmetric battery. The critical current density and cycle stability were tested under constant current charge and discharge conditions. The current density was gradually increased until the battery short-circuited, and the critical current density value was recorded.

[0098] 3. Structural stability test: After the modified solid electrolyte is bonded to the lithium metal foil, it is left to stand for 3 days. The phase change at the interface is analyzed by XRD to determine the chemical compatibility between the electrolyte and the lithium anode. At the same time, the evolution of the interface impedance over time is monitored by impedance testing.

[0099] Please refer to Table 1 for the test results above.

[0100] Table 1. Performance test results of Examples 1-8 and Comparative Examples 1-4 of this application

[0101]

[0102] The modified solid electrolyte preparation methods of Examples 1-8 of this application introduce a third component to modify the binary halide matrix through a specific process. The first solid-phase reaction is carried out through mixing, which helps to form a precursor powder with more uniform chemical properties and a more even distribution of reactive sites. This achieves uniform pre-activation and dispersion of the third component at the molecular scale, thereby reducing the risk of component segregation and the formation of non-target impurity phases. The cold-pressing process prepares a preform sheet, constructing a high-density, closely contacting reaction precursor configuration at room temperature. This shortens the diffusion path of substances during subsequent heat treatment, making the original... The solid-state reaction, which normally requires high temperature and pressure to drive, can now be carried out at lower heat treatment temperatures and at ambient (or low) pressure. This reduces the activation energy and process severity required for subsequent solid-state reactions. Furthermore, through heat treatment and a second solid-state reaction, a full solid-state reaction is achieved, promoting the efficient and quantitative entry of the third component (such as oxygen) into the target lattice sites to form a solid solution. This results in a product with uniform grain size, clean grain boundaries, and a dense microstructure. Moreover, under the specific process design of this application, the heat treatment is carried out at lower temperatures, eliminating the need for prolonged high temperatures or special atmospheres. Therefore, the preparation method of this application can introduce a third component into the binary halide matrix while effectively reducing the high energy consumption required for modification. This improves process controllability and reduces process costs, while also avoiding the loss of volatile components, abnormal grain coarsening, and structural defects caused by uncontrolled reaction kinetics that may result from prolonged high-temperature sintering.

[0103] Both Comparative Example 1 and Comparative Example 2 were sintered directly after simple blending. Comparative Example 1 was sintered at a low temperature, while Comparative Example 2 was sintered at a high temperature. In comparison, the doping effect of Comparative Example 1 was worse than that of Comparative Example 2, indicating that the simple blending and sintering process in related technologies usually requires long-term high-temperature sintering to promote the incorporation of the third component.

[0104] Comparative Example 3 uses ball milling for mixing but does not perform cold pressing and directly sintersects at low temperature, while Comparative Example 4 uses simple blending followed by cold pressing and low-temperature sintering. The doping effects of Comparative Examples 3 and 4 are not as good as those of the embodiments in this application, indicating that ball milling is required to initiate a pre-solid phase reaction and cold pressing in order to effectively reduce the temperature required for subsequent sintering.

[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The embodiments described above are merely illustrative of several implementations of the technical solution of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the technical solution of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing a modified solid electrolyte, characterized in that, The preparation method includes the following steps: Provided are a first component and a second component for forming a binary halide solid electrolyte matrix, the binary halide solid electrolyte matrix having the general chemical formula Li3InR6, where R includes one or more of Cl, Br, I and F, and a third component for structural modification of the binary halide solid electrolyte matrix. The first component, the second component, and the third component are mixed and subjected to a first solid-phase reaction to prepare a precursor powder. The precursor powder is subjected to cold pressing to prepare a cold-pressed molded body; The cold-pressed body is subjected to heat treatment to carry out a second solid-phase reaction, thereby preparing the modified solid electrolyte.

2. The preparation method according to claim 1, characterized in that, The mixing is carried out by ball milling to conduct the first solid-phase reaction, wherein the ball milling speed is 400 rpm to 600 rpm and the ball milling time is 9 h to 16 h.

3. The preparation method according to claim 1, characterized in that, The pressure of the cold pressing process is 100 MPa to 300 MPa.

4. The preparation method according to claim 1, characterized in that, The heat treatment satisfies at least one of the following conditions: (1) The temperature of the heat treatment is 250 ℃ to 300 ℃; (2) The heat treatment time is 1 h to 3 h; (3) The heating rate of the heat treatment is 2 ℃ / min to 5 ℃ / min.

5. The preparation method according to claim 1, characterized in that, The preparation method satisfies at least one of the following conditions: (1) The first component includes lithium halide; (2) The second component includes indium halide; (3) The third component includes an oxygen-containing lithium source.

6. The preparation method according to claim 1, characterized in that, The first component includes lithium chloride, the second component includes indium chloride, and the third component includes lithium oxide.

7. The preparation method according to claim 6, characterized in that, The molar ratio of lithium chloride, indium chloride and lithium oxide is (2.8~3.2):1:(0.05~0.25).

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

9. The modified solid electrolyte as described in claim 8, characterized in that, The modified solid electrolyte satisfies at least one of the following conditions: (1) The general chemical formula of the modified solid electrolyte is Li 3+2x InCl6O x , 0.05≤x≤0.25; (2) The modified solid electrolyte has equiaxed grains bonded together, the size of which is 1 μm to 5 μm; (3) The modified solid electrolyte has an ionic conductivity of 1.8 mS / cm at room temperature. -1 Up to 2.5 mS cm -1 ; (4) The critical current density of the modified solid electrolyte and the lithium metal anode is greater than or equal to 0.8 mA cm⁻¹. -2 .

10. A solid-state battery, characterized in that, The solid-state battery includes the modified solid-state electrolyte as described in claim 8 or 9.

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