Mg, F co-doped solid-state electrolyte material and preparation method thereof

Abstract

This application provides a Mg / F co-doped solid electrolyte material and its preparation method, relating to the field of solid-state battery technology. The material matrix provided by this invention has the general chemical formula Li. （3‑x+Δ） M (1‑x) Cl (6‑Δ) S Δ Where M is Zr and / or Y, 0≤x≤1, 0≤Δ≤1; This invention innovatively balances and improves the bulk and interfacial properties of Li-Zr / Y-Cl-S solid electrolyte through Mg and F co-doping, making it more suitable for high-safety, high-energy-density all-solid-state lithium metal batteries, and has important application value; The preparation method provided by this invention uses a single MgF2 doping source, combined with ball milling-rapid thermal treatment process, which eliminates the need for high-temperature sintering, reduces energy consumption, and is easy to scale up.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and more specifically, to a Mg and F co-doped solid electrolyte material and its preparation method. Background Technology

[0002] All-solid-state lithium batteries, due to their use of non-flammable solid electrolytes, represent the future direction for high-safety, high-energy-density batteries. Existing halide solid electrolytes (such as Li3YCl6 and Li2ZrCl6) exhibit relatively high room-temperature ionic conductivity (approximately 10). -3 Advantages include good mechanical flexibility and a wide electrochemical stability window (compatible with high-voltage cathodes such as NCM811). However, two major technical bottlenecks still exist: Insufficient ionic conductivity: The Li–Zr(Y)–Cl system has a room temperature conductivity of approximately 10. -3 S / cm, lower than sulfide superionic conductors (10 -2 (on the order of S / cm), limiting battery power performance.

[0003] Poor interface stability: It is prone to reduction reaction when in contact with lithium metal anode (lower stability limit approximately 2.3V vs Li / Li). + The generation of byproducts such as LiCl leads to an increase in interfacial impedance, which induces the growth of lithium dendrites.

[0004] Existing technologies utilize single anion / cation doping (such as F) - Replace Cl - Zr 4+ Replace Y 3+ ) or mixed anions (such as S) 2- With Cl - Co-doping can partially improve performance, but it has not yet achieved synergistic optimization of improving bulk conductivity and interface stability.

[0005] Therefore, this application aims to provide a Mg and F co-doped solid electrolyte material and its preparation method to better solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this application is to provide a Mg and F co-doped solid electrolyte material and its preparation method. By simultaneously performing cation doping and anion doping, the bulk ionic conductivity and interfacial stability of the material are synergistically improved, thereby overcoming the shortcomings of the prior art and meeting the performance requirements of solid electrolytes for all-solid-state lithium metal batteries.

[0007] This application provides a Mg / F co-doped solid electrolyte material, the matrix of which has the general chemical formula Li. （3-x+Δ） M (1-x) Cl (6-Δ) SΔ Where M is Zr and / or Y, 0≤x≤1, 0≤Δ≤1, and the material is doped with Mg based on the matrix composition. 2+ and F - The total doping amount is 0.05-0.1 at% relative to the atomic percentage of the total atoms in the matrix, and the doping source is MgF2.

[0008] Furthermore, the molar ratio of Zr to Y in this material is 1:1 to 3:7 to form a solid solution; and the material contains a hexagonal halide phase and an amorphous glass phase.

[0009] Based on the same inventive concept, this application also provides a method for preparing the above-mentioned Mg, F co-doped solid electrolyte material, comprising the following steps: The raw materials are mixed according to the target stoichiometric ratio and ball-milled to ensure that the components are fully mixed and reacted to obtain the precursor powder. The precursor is subjected to rapid heat treatment, followed by immediate quenching, to obtain a solid electrolyte material that is mainly in the glassy state.

[0010] Furthermore, the raw materials contain lithium halides, zirconium halides, yttrium halides, sulfur sources, and MgF2 doping sources.

[0011] Furthermore, ball milling was performed under anhydrous and oxygen-free conditions.

[0012] Furthermore, the heat treatment involves rapidly heating the temperature to approximately 300°C and maintaining it for 0.5-1 hour under an inert atmosphere or in a sealed environment.

[0013] Further, after quenching, the material is ground and sieved in an argon glove box to obtain the final product.

[0014] The beneficial effects of this invention are: 1. The material provided by this invention, through Mg 2+ Substitution introduces cation vacancy defects, significantly improving the Li content in solid electrolytes. + The number and mobility of these molecules greatly improve the room-temperature ionic conductivity of the material, while simultaneously increasing the amount and rate of migration through F... - The doping of the material and the in-situ generation of the LiF passivation layer at the interface effectively suppresses lithium dendrite growth and reduces interfacial side reactions, thus greatly improving the interface stability. This invention innovatively balances and improves the bulk and interfacial properties of the Li-Zr / Y-Cl-S solid electrolyte through Mg and F co-doping, making it more suitable for high-safety, high-energy-density all-solid-state lithium metal batteries, and has important application value. 2. The preparation method provided by the present invention uses a single MgF2 doping source and combines ball milling-rapid heat treatment process, which eliminates the need for high-temperature sintering, reduces energy consumption, and facilitates large-scale production. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the preparation process in an embodiment of the present invention. Detailed Implementation

[0017] To facilitate understanding of the present invention, it will be described more fully below through embodiments, and preferred embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Any other implementation schemes obtained by modifying or equivalently substituting the technical solutions of the present invention without inventive step are all within the protection scope of the present invention.

[0018] 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. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] The numerical values ​​disclosed in the embodiments of this invention are approximate values, not definitive values. Where error or experimental conditions permit, all values ​​within the error range may be included, and the specific numerical values ​​disclosed in the embodiments of this invention are not limited to those specified.

[0020] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0021] Comparative Example: Li-Zr / Y-Cl-S matrix solid electrolyte (undoped control sample) This comparative example provides a Mg and F co-doped solid electrolyte material, the matrix of which has an approximate chemical formula of Li3Zr. 0.5 Y 0.5 Cl 5.5 S 0.5 (That is, in the Li-Zr / Y-Cl-S system, the Zr:Y atomic ratio is about 1:1, and the Cl:S ratio is about 11:1).

[0022] The raw materials and their proportions are as follows: 2.0 mol of anhydrous lithium chloride (LiCl), providing equivalent amounts of Li and Cl; 0.5 mol of zirconium tetrachloride (ZrCl4), providing equivalent amounts of Zr and Cl; 0.5 mol of yttrium trichloride (YCl3), providing equivalent amounts of Y and Cl; and 0.5 mol of lithium sulfide (Li2S), providing equivalent amounts of Li and S. The target stoichiometric ratio calculated from the above raw material proportions is: Li:Zr:Y:Cl:S = 3 : 0.5 : 0.5 : 5.5 : 0.5.

[0023] Prepared using the following steps: Ball milling and mixing: Weigh approximately 5 grams of each of the above-mentioned raw materials in an Ar-protected glove box and place them into a sealed stainless steel ball mill jar. Add several zirconia ceramic balls (5 mm in diameter) to the jar, with a material-to-ball ratio of approximately 1:10. Place the jar in a planetary ball mill and mill at 500 rpm for 10 hours, stopping for 10 minutes every 0.5 hours to prevent overheating. During the ball milling process, easily hydrolyzable raw materials such as ZrCl4 and YCl3 are kept in an anhydrous environment to avoid material failure. After ball milling, a uniformly mixed precursor powder is obtained, which is light grayish-white in color.

[0024] Heat treatment and quenching: The precursor powder was transferred into a quartz ampoule, evacuated, filled with high-purity Ar gas, and sealed. The ampoule was heated to 300°C at a rate of 10°C / min in a tube furnace and held for 30 minutes to allow the precursor to undergo a solid-phase reaction and partial recrystallization. The ampoule was then quickly removed from the furnace and rapidly cooled to ambient temperature. Due to the sealed ampoule, the material experienced precipitous cooling during the rapid cooling process, preventing sufficient grain growth and resulting in a solid electrolyte product containing a glassy phase. The cooled sample was removed from a glove box, gently ground, and passed through a 100-mesh sieve to obtain a uniform solid electrolyte powder.

[0025] XRD analysis revealed that the main phase was a Li-Zr / Y-Cl-S solid solution, accompanied by a broad amorphous scattering background.

[0026] Performance testing: The obtained solid electrolyte powder was pressed into tablets (10 mm in diameter, approximately 1 mm thick, at a pressure of 300 MPa), and the room temperature ionic conductivity was measured using electrostatic impedance spectroscopy (EIS). The results showed that the room temperature conductivity of the undoped sample was approximately 5.8 × 10⁻⁶. -4 The ion migration activation energy, Ea≈0.30 eV, was calculated by impedance testing at varying temperatures (25℃-60℃) and linear fitting of the Arrhenius relation. This electrolyte was then used to assemble a symmetrical battery (Li|Li-Zr / Y-Cl-S|Li) with a lithium metal sheet, and lithium deposition / stripping cycles were repeatedly performed at a constant current density of 0.1 mA / cm². 2 Single-trip capacity: 0.1 mAh / cm³ 2As a result, the battery polarization voltage rose rapidly after about 20 hours, indicating that the increased interfacial impedance led to cycling instability.

[0027] This electrolyte is used in full-cell assembly: The positive electrode is NCM811 (loading ≈ 4 mg / cm³). 2 A mixture of 20 wt% solid electrolyte and lithium-plated copper foil was used as the negative electrode (the lithium plating was removed before the first cycle to simulate an anode-free state), and a pure solid electrolyte membrane was used as the separator. Charge-discharge tests were conducted at 0.2C at room temperature. The results showed that the discharge capacity in the first cycle was approximately 150 mAh / g, the initial coulombic efficiency was approximately 90%, and the capacity retention rate after 50 cycles was approximately 70%, exhibiting some capacity decay and interfacial instability.

[0028] Example 1: This embodiment provides a Mg and F co-doped solid electrolyte material, which introduces Mg and F co-doping based on the matrix composition of the comparative example. The doping source is magnesium fluoride (MgF2), and the doping amount refers to the atomic ratio of Mg relative to the total number of metal atoms. According to the set doping ratio, in addition to the raw materials described in the comparative example, approximately 0.0025 moles of MgF2 are added. The molar ratios of the raw materials are as follows: LiCl 2.0, ZrCl4 0.5, YCl3 0.5, Li2S 0.5, MgF2 0.0025.

[0029] The raw materials were mixed uniformly using the same ball milling process as the comparative example (500 rpm, 10 hours). Due to the addition of a small amount of MgF2 in this embodiment, some in-situ reactions may occur during ball milling, such as a small amount of MgF2 reacting with LiCl to generate LiF and MgCl2. These byproducts are uniformly dispersed in the precursor and have a positive impact on subsequent performance. Subsequently, the precursor powder was rapidly heat-treated under the same conditions (300℃, 0.5 hours) and quenched to obtain Mg, F co-doped Li-Zr / Y-Cl-S solid electrolyte powder.

[0030] Phase structure: XRD results show that the characteristic diffraction peak positions of the sample in this embodiment are slightly shifted compared to the undoped sample in the comparative example. The main peak, located at approximately 15.2°, shifts towards higher angles to approximately 15.3°, indicating a slight decrease in the lattice constant. This may be attributed to F - Partially replaced Cl with a larger ionic radius - and S 2- This causes lattice shrinkage. Simultaneously, the full width at half maximum (FWHM) of the diffraction peaks increases, reflecting a decrease in grain size and an increase in lattice disorder, resulting in more amorphous features in the material. This is consistent with the effect of rapid condensation combined with trace heterogeneous doping in hindering grain growth.

[0031] Ion conductivity: When the co-doped sample was fabricated into a φ10 mm disc for testing, its room temperature ionic conductivity increased to approximately 9.1 × 10⁻⁶. -4 The S / cm ratio was increased by approximately 57% compared to the undoped sample. Arrhenius fitting yielded an ion migration activation energy Ea ≈ 0.25 eV, a significant decrease from the undoped 0.30 eV, indicating that Mg... 2+ Li introduced by doping + Empty space and F - Doping-induced lattice distortion effectively reduces Li + Migration barrier.

[0032] Electrochemical interface stability: In the Li|electrolyte|Li symmetric battery, the electrolyte in this embodiment exhibits more stable cycle performance. (At 0.1 mA / cm²) 2 Repeated lithium plating at varying current densities for over 50 hours did not result in short circuits or significant overvoltage increases in the battery, and the interface impedance remained stable and was lower than the undoped control. This indicates that a small amount of F... - The LiF interface phase formed by doping effectively suppressed the direct and unstable contact between lithium and the electrolyte. Furthermore, AC impedance measurements revealed that after the same amount of lithium-symmetric battery cycling, the interfacial resistance of the co-doped electrolyte was only about half that of the undoped sample.

[0033] Full-cell performance: The electrolyte from this embodiment was used in an NCM811 cathode / anode-less all-solid-state battery and tested under the same conditions as the comparative example. The results showed that the battery's initial discharge specific capacity was approximately 170 mAh / g, and the initial coulombic efficiency was improved to ~92%. After 50 cycles, the capacity retention was approximately 80%, significantly better than the 70% of the comparative control battery. This indicates that the co-doped electrolyte effectively reduced irreversible capacity loss during cycling and improved the battery's cycle life.

[0034] Example 2: This embodiment provides a Mg and F co-doped solid electrolyte material, and further increases the MgF2 doping amount. The raw material ratio is: LiCl 2.0, ZrCl4 0.5, YCl3 0.5, Li2S 0.5, MgF2 0.0050 (molar).

[0035] The preparation process is the same as in Example 1: the mixture is first ball-milled, then rapidly heat-treated at 300°C and quenched to obtain a 0.1 at% Mg and F co-doped solid electrolyte.

[0036] Phase and Morphology: XRD results show that even with further increases in doping concentration, the material maintains the same halide crystal phase structure as the matrix, with no detectable impurity phases (such as obvious diffraction peaks of MgF2 or LiF), indicating that most of the dopant elements have entered the material lattice or are dispersed at the nanoscale. The main diffraction peaks further shift slightly towards higher angles (e.g., from 15.2° in the undoped form to approximately 15.35° in this embodiment), and the lattice parameters decrease slightly. The peak shapes are more broadened, and some weak peaks are even difficult to distinguish, indicating that the material is predominantly amorphous with extremely fine grains. High-resolution transmission electron microscopy reveals that LiF microcrystals of approximately 5-10 nm in size are dispersed throughout the material, forming tight contact interfaces with each other and with the main crystal phase. The presence of these trace LiF phases further corroborates the mechanism of in-situ precipitation of passivation phases at the interfaces by F^- doping.

[0037] Ionic conductivity: The ionic conductivity of the material in this embodiment is further improved. The conductivity measured at room temperature is approximately 1.1 × 10⁻⁶. -3 The S / cm ratio represents a first breakthrough into the millisiemens (cm) range, approximately twice that of the undoped matrix. The ion migration activation energy further decreased to ~0.22 eV, approaching the level of sulfide superionic conductors (such as LGPS materials with Ea ≈ 0.20 eV). This indicates that by optimizing the doping concentration, Li... + The transmission channel has been further improved. However, it should be noted that excessive doping may introduce too much insulating phase (such as LiF), which may lead to a decrease in conductivity. Therefore, the current embodiment is close to the upper limit of optimization and should not be increased excessively.

[0038] Electrochemical performance: In the Li-symmetric cell test, the electrolyte sample in this example achieved a speed of 0.1 mA / cm². 2 No short circuits were observed after more than 100 hours of stable cycling, and the interface voltage remained low and stable, demonstrating excellent resistance to dendrite penetration and interface stability. In the NCM811 / / Cu anode-free full cell, the initial discharge capacity reached approximately 175-180 mAh / g, approaching 90% of the theoretical capacity of the NCM811 cathode material; the initial coulombic efficiency was approximately 94%, indicating minimal initial irreversible capacity loss due to reduced interfacial side reactions. The battery exhibited excellent cycling performance: after 100 cycles at 0.2C, the capacity retention was above 85%, significantly higher than the ~60% of the undoped control. Even at a 0.5C discharge rate, the electrolyte-doped battery of this invention maintained a capacity of approximately 140 mAh / g, while the undoped battery rapidly decayed to below 100 mAh / g at 0.5C. These results demonstrate that the co-doping strategy significantly enhances the supporting role of the solid electrolyte in high-energy-density anode-free batteries, enabling the battery to possess both high capacity and long lifespan.

[0039] Comparison and Analysis: Based on the results of the comparative examples and Examples 1-2, it can be seen that with the introduction and increase of Mg and F doping, the phase structure of the Li-Zr / Y-Cl-S solid electrolyte material gradually transforms from a crystalline state to an amorphous state. + The carrier concentration and channel structure for migration were optimized, resulting in a steady increase in ionic conductivity and a significant improvement in interfacial stability. This invention achieves dual-doping modification of cations and anions simultaneously through a single doping source, representing a novel approach to the design of solid-state electrolyte materials. A small amount of Mg... 2+ and F - Causing positive effects: Mg 2+ An open space was created, F - The interface is stabilized, and the two complement each other, enabling the material to meet the requirements of use under harsh conditions (such as no-anodine battery cycling).

[0040] In summary, the material provided by this invention, through Mg 2+ Substitution introduces cation vacancy defects, significantly improving the Li content in solid electrolytes. + The number and mobility of these molecules greatly improve the room-temperature ionic conductivity of the material, while simultaneously increasing the amount and rate of migration through F... - The doping of the material and the in-situ generation of the LiF passivation layer at the interface effectively suppresses lithium dendrite growth and reduces interfacial side reactions, thus greatly improving the interface stability. This invention innovatively balances and improves the bulk and interfacial properties of the Li-Zr / Y-Cl-S solid electrolyte through Mg and F co-doping, making it more suitable for high-safety, high-energy-density all-solid-state lithium metal batteries, and has important application value. The preparation method provided by this invention uses a single MgF2 doping source and combines ball milling-rapid thermal treatment process, which eliminates the need for high-temperature sintering, reduces energy consumption, and facilitates large-scale production.

[0041] Those skilled in the art will understand that, without departing from the principles of the present invention, the specific raw material selection, proportions, and process conditions of the above embodiments can be equivalently replaced or adjusted. For example, the Zr to Y ratio of component M can be adjusted according to cost or performance requirements (e.g., Zr:Y = 3:7 or 5:5), and the S anion substitution amount Δ can also be selected from different values ​​within the range of 0-1 (e.g., Δ = 0.25 or 0.75) to adjust the crystal structure and properties of the material. Furthermore, the temperature and time of rapid heat treatment can be optimized within the range of 200-400°C according to equipment conditions, as long as partial crystallization and timely quenching are achieved. These variations all fall within the scope of protection claimed by the present invention.

[0042] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A Mg / F co-doped solid electrolyte material, characterized in that, The material matrix has a general chemical composition Li （3-x+Δ） M (1-x) Cl (6-Δ) S Δ where M is Zr and / or Y, 0≤x≤1, 0≤Δ≤1, and the material is doped with Mg 2+ and F - in an amount of 0.05-0.1 at% relative to the total number of atoms in the matrix, the doping source being MgF2.

2. The Mg, F co-doped solid electrolyte material according to claim 1, characterized in that, The material contains Zr to Y in a molar ratio of 1:1 to 3:7 to form a solid solution; and the material contains a hexagonal halide phase and an amorphous glass phase.

3. A method for preparing the Mg, F co-doped solid electrolyte material as described in claim 1 or 2, characterized in that, Includes the following steps: The raw materials are mixed according to the target stoichiometric ratio and ball-milled to ensure that the components are fully mixed and reacted to obtain the precursor powder. The precursor is subjected to rapid heat treatment, followed by immediate quenching, to obtain a solid electrolyte material that is mainly in the glassy state.

4. The method for producing a Mg and F co-doped solid electrolyte material according to claim 3, characterized in that, The raw materials contain lithium halides, zirconium halides, yttrium halides, sulfur sources, and MgF2 doping sources.

5. The method for producing a Mg and F co-doped solid electrolyte material according to claim 3, characterized in that, Ball milling under anhydrous and oxygen-free conditions.

6. The method for producing a Mg and F co-doped solid electrolyte material according to claim 3, characterized in that, Heat treatment involves rapidly heating the temperature to approximately 300°C and holding it therefore for 0.5-1 hour under an inert atmosphere or in a sealed environment.

7. The method for producing a Mg / F co-doped solid electrolyte material according to claim 3, characterized in that, After quenching, the material is ground and sieved in an argon glove box to obtain the final product.

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