Liquid metal-coated modified metal fluoride cathode material and method of making same

Abstract

The application provides a liquid metal-coated modified metal fluoride positive electrode material, comprising a positive electrode material substrate and a coating layer coated on the surface of the positive electrode material substrate, wherein the positive electrode material substrate comprises a metal fluoride, and the coating layer comprises a liquid metal; and the liquid metal is at least one of gallium or a gallium-based alloy. The modification of the metal fluoride positive electrode material substrate is achieved by coating the liquid metal on the surface of the metal fluoride positive electrode material substrate, the self-repairing property of the liquid metal is utilized, an interface layer capable of plastic deformation is provided, the dissolution of metal ions of the metal fluoride during the charging and discharging process is inhibited, and the electronic and ionic transmission channels between the metal fluoride particles and the particles are provided, so that the capacity density, the cycle stability and the cycle life of the metal fluoride positive electrode material are greatly improved. The application also provides a preparation method of the liquid metal-coated modified metal fluoride positive electrode material.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery cathode materials, and in particular to a liquid metal-coated modified metal fluoride cathode material and its preparation method. Background Technology

[0002] Currently commercially available lithium-ion battery cathode materials, such as lithium cobalt oxide, lithium iron phosphate, and nickel-cobalt-manganese ternary cathode materials, typically have low theoretical specific capacities, only 140-180 mAh / g. Metal fluorides, on the other hand, possess higher theoretical operating voltages (e.g., CuF2, 3.55V vs Li / Li). + With its considerable specific capacity (e.g., FeF3, 713 mAh / g), it has become the most promising high-energy-density cathode material. However, due to the ionic nature of the metal-fluorine bond, metal fluorides are nearly insulating, resulting in poor reaction kinetics, low energy transfer efficiency (large voltage hysteresis), and low capacity utilization. Furthermore, volume changes during charge and discharge, unstable reaction interfaces, and the dissolution of electrode active materials lead to rapid capacity decay within short cycles, resulting in poor cycle stability and short cycle life.

[0003] Existing studies have employed various methods to coat and modify existing metal fluorides or perform other surface modifications to improve their overall electrochemical performance. For example, some researchers have used Fe... 3+ B 3+ The surface of the copper fluoride particles is sequentially coated with modified FeF 3-2x O x The Fe2O3 coating layer, while alleviating the dissolution problem of active materials in the electrolyte to some extent and promoting the uniform distribution of copper discharge products in the electrode, thus improving the cycle stability of the copper fluoride cathode, cannot fully adapt to the volume changes generated during the charge and discharge process of the copper fluoride cathode material. This leads to damage to the coating structure and interface failure during cycling. Therefore, the copper fluoride cathode material obtained by the above scheme has poor cycle performance and low energy density, with limited improvement effect. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this application is to provide a liquid metal-coated modified metal fluoride cathode material to effectively improve the specific capacity, cycle stability, and cycle life of metal fluoride cathode materials.

[0005] In addition, this application also provides a method for preparing the above-mentioned liquid metal coated and modified metal fluoride cathode material.

[0006] To achieve the above objectives, this application provides a liquid metal-coated modified metal fluoride cathode material, comprising a cathode material substrate and a coating layer modified on the surface of the cathode material substrate, wherein the cathode material substrate comprises a metal fluoride and the coating layer comprises liquid metal; the liquid metal is at least one of gallium or gallium-based alloys.

[0007] In some possible embodiments, the general chemical formula of the metal fluoride is MF. y M is at least one of Fe, Co, Ni or Cu, and y is 2 or 3.

[0008] In some possible implementations, the metal fluoride is CuF2, FeF2, or FeF3.

[0009] In some possible implementations, the gallium-based alloy is a gallium-tin alloy, a gallium-indium alloy, or a gallium-indium-tin alloy.

[0010] In some possible implementations, the mass ratio of the metal fluoride to the liquid metal is 50:(1-10).

[0011] This application also provides a method for preparing a liquid metal-coated modified metal fluoride cathode material, including the following steps:

[0012] At a temperature higher than the melting point of the liquid metal, the cathode material matrix, the liquid metal, and the dispersion medium are physically dispersed to coat the surface of the cathode material matrix with the liquid metal. After drying, the liquid metal-coated modified metal fluoride cathode material is obtained.

[0013] In some possible implementations, the physical dispersion process includes at least one of planetary ball milling, high-energy ball milling, ultrasonic dispersion, high-speed shear dispersion, high-speed grinding, mechanical stirring dispersion, or high-pressure homogenization dispersion.

[0014] In some possible implementations, the physical dispersion process is carried out under an inert atmosphere.

[0015] In some possible implementations, the drying step is performed at a temperature of 70°C-120°C for 6-12 hours.

[0016] In some possible implementations, the dispersion medium is an organic solvent that does not react with the metal fluoride and the liquid metal.

[0017] To address the problems of low conductivity, poor electrode / electrolyte interface stability, and rapid capacity decay of metal fluorides, this application breaks through traditional solid solution and oxide modification methods. It modifies the surface of metal fluoride cathode materials by coating them with liquid metal. Utilizing the "self-healing" properties of liquid metal, a "dynamically stable" cathode interface is constructed, providing a plastically deformable interface layer. This inhibits the dissolution of metal ions during charge and discharge, effectively improving electrode capacity and cycle life. Furthermore, the liquid metal coating layer, acting as a conductive network, provides electron and ion transport channels between metal fluoride particles, thereby significantly improving the capacity density, cycle stability, and cycle life of the metal fluoride cathode material. Attached Figure Description

[0018] Figure 1 This is an X-ray diffraction pattern of the CuF2 / carbon cathode material modified with liquid gallium coating in Example 2 of this application.

[0019] Figure 2 This is a scanning electron microscope image of the CuF2 / carbon cathode material modified with liquid gallium coating in Example 2 of this application.

[0020] Figure 3 This is an EDS mapping diagram of the CuF2 / carbon cathode material modified with liquid gallium coating in Example 2 of this application.

[0021] Figure 4 This is a charge-discharge curve of the coin cell prepared in Example 2 of this application. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0024] One embodiment of this application provides a liquid metal-coated modified metal fluoride cathode material, comprising a cathode material substrate and a coating layer coated and modified on the surface of the cathode material substrate. The cathode material substrate comprises a metal fluoride, and the coating layer comprises liquid metal. The liquid metal is at least one of gallium or a gallium-based alloy.

[0025] To address the problems of low conductivity, poor electrode / electrolyte interface stability, and rapid capacity decay of metal fluorides, this application breaks through traditional solid solution and oxide modification methods by coating the surface of the metal fluoride cathode material with liquid metal. Due to the "self-healing" properties of liquid metal, it can effectively adapt to the volume changes of the electrode material during charge and discharge, constructing a coating layer that is not easily damaged and has intact mechanical structure, thus providing an interface layer capable of plastic deformation. Furthermore, metal fluorides generate some soluble metal ion intermediates during charge and discharge. The liquid metal can spontaneously alloy with these soluble metal ion intermediates, fixing the soluble metal ions within the liquid metal coating layer structure. This inhibits the dissolution of metal ions during charge and discharge, thereby constructing a "dynamically stable" cathode interface and significantly improving the capacity density, cycle stability, and cycle life of the metal fluoride cathode material. Furthermore, the liquid metal coating layer, acting as a conductive network, can also provide electron and ion transport channels between metal fluoride cathode particles, effectively improving the electrode's capacity and cycle life.

[0026] Understandably, in addition to metal fluoride cathode materials, the modification method using liquid metal coating in this application can be applied to other lithium-ion battery electrode materials with large volume changes during charging and discharging, such as silicon-based anode materials, which can effectively alleviate capacity decay and electrode failure caused by volume expansion.

[0027] In some embodiments, the general chemical formula of the metal fluoride is MF. y M is at least one of Fe, Co, Ni, or Cu, and y is 2 or 3. Specifically, the metal fluoride is CuF2, FeF2, or FeF3.

[0028] Understandably, since metal fluorides themselves have very poor conductivity and are essentially insulators, the cathode material matrix used in this application can be a metal fluoride / carbon composite material, i.e., the general chemical formula of the cathode material matrix is ​​MF. y / C, using carbon materials, a continuous conductive network can be constructed for metal fluorides, thereby improving conductivity. The carbon material can be a carbon-based conductive additive, and the metal fluoride is located in the gaps within the conductive structure formed by the carbon-based conductive additive material. Specifically, the carbon-based conductive additive can be, but is not limited to, carbon nanotubes, Super-P, acetylene black, Ketjenblack carbon black, XC-72 carbon black, ordered mesoporous carbon CMK-3, etc.

[0029] In addition, the cathode material matrix can be prepared using existing conventional methods. For example, the preparation method of CuF2 / C composite material may include the following steps:

[0030] First, a copper source solution of a certain concentration is prepared, and a certain amount of carbon source is added to the copper source solution. At this time, ultrasonic technology can be used to promote dispersion and obtain a mixture. Then, after the mixture is dried, it is heated and fluorinated in a fluorine source gas atmosphere to obtain the CuF2 / C composite material.

[0031] Alternatively, CuF2 and a carbon source can be physically dispersed (e.g., ball milling) to obtain the CuF2 / C composite material.

[0032] In some embodiments, the liquid metal is one or more of gallium, gallium-tin alloy, gallium-indium alloy, and gallium-indium-tin alloy. Preferably, the liquid metal is gallium. Liquid gallium and gallium-based alloys possess excellent properties such as low melting point, high conductivity, high surface tension, and low toxicity, exhibiting extremely strong self-healing capabilities. Therefore, the core-shell structure constructed from liquid metal can perfectly adapt to the volume changes that occur during battery charging and discharging, maintaining the integrity of the coating layer.

[0033] In some embodiments, the mass ratio of the metal fluoride to the liquid metal is 50:(1-10). Preferably, the mass ratio of the metal fluoride to the liquid metal is 50:(2-5). When the amount of liquid metal added is too small, it is not conducive to the formation of a complete and continuous coating layer, and the dissolution of the positive electrode active metal ions cannot be sufficiently suppressed, which is not conducive to improving the reversibility of the metal fluoride positive electrode; while when the amount of liquid metal added is too large, the coating layer is too thick, which affects the migration and transport of lithium ions at the positive electrode interface, and will lead to a decrease in the capacity of the positive electrode material.

[0034] An embodiment of this application also provides a method for preparing the above-mentioned liquid metal coated modified metal fluoride cathode material, comprising the steps of: physically dispersing the cathode material matrix, the liquid metal and the dispersion medium at a temperature higher than the melting point of the liquid metal, so that the liquid metal coats the surface of the cathode material matrix, and obtaining the liquid metal coated modified metal fluoride cathode material after drying.

[0035] Physical dispersion utilizes external shear and impact mechanical energy to break down the liquid metal from macroscopic droplets into nanoscale microdroplets, ensuring their uniform distribution within the dispersion medium. Simultaneously, the mechanical force promotes full contact between the liquid metal microdroplets and the metal fluoride cathode particles, generating force interactions that effectively coat the cathode particles with the liquid metal. Compared to chemical dispersion methods, physical dispersion is lower in cost, simpler to operate, and requires no dispersant, making it more suitable for the preparation of the material system described in this application.

[0036] In some embodiments, the physical dispersion treatment is one or more of planetary ball milling, high-energy ball milling, ultrasonic dispersion, high-speed shear dispersion, high-speed grinding, mechanical stirring dispersion, and high-pressure homogenization dispersion. Preferably, the physical dispersion treatment is planetary ball milling, high-energy ball milling, ultrasonic dispersion, or high-speed shear dispersion.

[0037] The dispersion medium is an organic solvent that does not react with metal fluorides or liquid metals. Specifically, the dispersion medium is one or more selected from anhydrous ethanol, anhydrous acetonitrile, N-methylpyrrolidone, acetone, N,N-dimethylformamide, isopropanol, ethylene glycol dimethyl ether, toluene, ethylene glycol, propylene glycol, and dimethyl sulfoxide. Preferably, the dispersion medium is anhydrous ethanol, anhydrous acetonitrile, N-methylpyrrolidone, or acetone.

[0038] The drying step is performed at a temperature of 70-120℃ for 6-12 hours.

[0039] In some embodiments, the preparation method may specifically include the following steps:

[0040] In an inert atmosphere apparatus, a certain mass ratio of metal fluoride and liquid metal is added to a container, and an appropriate amount of dispersion medium is added to the container to obtain a mixture.

[0041] The mixture is physically dispersed at a temperature higher than the melting point of the liquid metal, so that the liquid metal fully coats and modifies the surface of the metal fluoride cathode particles.

[0042] The sample after the above physical dispersion treatment is transferred to a drying device and dried in a drying environment at a certain temperature. After cooling, the liquid metal-coated modified metal fluoride cathode material is obtained and transferred to an inert atmosphere device for storage.

[0043] The inert atmosphere device can be an inert atmosphere glove box, and the drying device can be a vacuum oven.

[0044] In some embodiments, the mass ratio of the added dispersion medium to the positive electrode material matrix is ​​approximately 10:1, so as to achieve uniform coating of the liquid metal on the surface of the positive electrode material matrix.

[0045] The metal fluoride raw materials used in this preparation method are abundant in the Earth's crust, inexpensive, and low-cost. Furthermore, the overall preparation process is simple, requiring no complex or expensive equipment, with short production time and effective cost savings, enabling large-scale industrial production. The resulting liquid metal-coated modified metal fluoride cathode material exhibits excellent electrochemical performance, thus holding significant importance for the development and application of next-generation high-energy-density lithium-ion batteries.

[0046] The technical solutions in this application will be explained below with reference to specific embodiments and comparative examples. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the invention. The main raw materials and equipment used in the specific embodiments and comparative examples are all conventional commercially available products or open-source materials.

[0047] The specific embodiments and comparative examples use a metal fluoride / carbon composite material, such as a CuF2 / carbon composite material, which is prepared by the following steps:

[0048] S1: In a glove box, add 750 mg CuF2 and 250 mg acetylene black to a sealed ball mill jar, and add 10 mL of anhydrous acetonitrile to the ball mill jar to obtain a mixture;

[0049] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 600 rpm for 8 hours to obtain a mixed slurry of CuF2 / carbon composite material;

[0050] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 80°C for 12 hours. After cooling to room temperature, CuF2 / carbon composite material was obtained and stored in a glove box environment.

[0051] Understandably, replacing CuF2 with FeF2 or FeF3 in the above preparation method will yield FeF2 / carbon composite material or FeF3 / carbon composite material.

[0052] Example 1

[0053] This embodiment provides a liquid gallium-coated modified CuF2 / carbon cathode material, denoted as CuF2 / C@Ga, whose preparation method includes the following steps:

[0054] S1: In a glove box, add 1000 mg of CuF2 / carbon composite material and 100 mg of liquid gallium metal into a sealed ball mill jar, and add 10 mL of N-methylpyrrolidone to the ball mill jar to obtain a mixture;

[0055] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 350 rpm for 5 hours to allow the liquid gallium metal to fully and uniformly coat the surface of the CuF2 / carbon composite particles and obtain a mixed slurry.

[0056] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, CuF2 / carbon cathode material with liquid gallium coating and modification at a mass ratio of CuF2 / carbon composite material to liquid gallium was obtained. The material was then transferred to a glove box for storage.

[0057] Example 2

[0058] This embodiment provides a liquid gallium-coated modified CuF2 / carbon cathode material, denoted as CuF2 / C@Ga, whose preparation method includes the following steps:

[0059] S1: In a glove box, 1000 mg of CuF2 / carbon composite material and 100 mg of liquid gallium metal were added to a sealed ball mill jar, and 10 mL of anhydrous acetonitrile was added to the ball mill jar to obtain a mixture;

[0060] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 350 rpm for 5 hours to allow the liquid gallium metal to fully and uniformly coat the surface of the CuF2 / carbon composite particles and obtain a mixed slurry.

[0061] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, CuF2 / carbon cathode material with liquid gallium coating and modification at a mass ratio of CuF2 / carbon composite material to liquid gallium was obtained. The material was then transferred to a glove box for storage.

[0062] Example 3

[0063] This embodiment provides a liquid gallium-coated modified CuF2 / carbon cathode material, denoted as CuF2 / C@Ga, whose preparation method includes the following steps:

[0064] S1: In a glove box, 1000 mg of CuF2 / carbon composite material and 50 mg of liquid gallium metal were added to a sealed ball mill jar, and 10 mL of anhydrous acetonitrile was added to the ball mill jar to obtain a mixture;

[0065] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 350 rpm for 5 hours to allow the liquid gallium metal to fully and uniformly coat the surface of the CuF2 / carbon composite particles and obtain a mixed slurry.

[0066] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, CuF2 / carbon cathode material with liquid gallium coating modified by CuF2 / carbon composite material and liquid gallium in a mass ratio of 50:2.5 was obtained and stored in a glove box environment.

[0067] Example 4

[0068] This embodiment provides a liquid gallium-coated modified CuF2 / carbon cathode material, denoted as CuF2 / C@Ga, whose preparation method includes the following steps:

[0069] S1: In a glove box, 1000 mg of CuF2 / carbon composite material and 200 mg of liquid gallium metal were added to a sealed ball mill jar, and 10 mL of anhydrous acetonitrile was added to the ball mill jar to obtain a mixture;

[0070] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 350 rpm for 5 hours to allow the liquid gallium metal to fully and uniformly coat the surface of the CuF2 / carbon composite particles and obtain a mixed slurry.

[0071] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, CuF2 / carbon cathode material with liquid gallium coating modified by CuF2 / carbon composite material and liquid gallium in a mass ratio of 50:10 was obtained and stored in a glove box environment.

[0072] Example 5

[0073] This embodiment provides a CuF2 / carbon cathode material modified by liquid metal gallium indium alloy coating, denoted as CuF2 / C@GaIn, and its preparation method includes the following steps:

[0074] S1: In a glove box, 1000 mg of CuF2 / carbon composite material and 100 mg of liquid gallium indium alloy were added to a sealed ball mill jar, and 10 mL of anhydrous acetonitrile was added to the ball mill jar to obtain a mixture;

[0075] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 350 rpm for 5 hours to allow the liquid metal gallium indium alloy to fully and uniformly coat the surface of the CuF2 / carbon composite particles and obtain a mixed slurry.

[0076] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, CuF2 / carbon cathode material coated with liquid metal gallium indium alloy with a mass ratio of CuF2 / carbon composite material to liquid metal gallium indium alloy of 50:5 was obtained and transferred to a glove box environment for storage.

[0077] Example 6

[0078] This embodiment provides a FeF2 / carbon cathode material modified by liquid metal gallium-tin alloy coating, denoted as FeF2 / C@GaSn, and its preparation method includes the following steps:

[0079] S1: In a glove box, 1000 mg of FeF2 / carbon composite material and 100 mg of liquid gallium-tin alloy were added to a sealed ball mill jar, and 10 mL of anhydrous acetonitrile was added to the ball mill jar to obtain a mixture;

[0080] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 350 rpm for 5 hours to allow the liquid gallium tin alloy to fully and uniformly coat the surface of the FeF2 / carbon composite particles, thereby obtaining a mixed slurry.

[0081] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, FeF2 / carbon cathode material modified by liquid gallium tin alloy coating with a mass ratio of FeF2 / carbon composite material to liquid gallium tin alloy of 50:5 was obtained and transferred to a glove box environment for storage.

[0082] Example 7

[0083] This embodiment provides a FeF3 / carbon cathode material modified by liquid metal gallium-tin alloy coating, denoted as FeF3 / C@GaSn, and its preparation method includes the following steps:

[0084] S1: In a glove box, 1000 mg of FeF3 / carbon composite material and 100 mg of liquid gallium-tin alloy were added to a sealed ball mill jar, and 10 mL of anhydrous acetonitrile was added to the ball mill jar to obtain a mixture;

[0085] S2: Place the sealed ball mill jar containing the above mixture on a planetary ball mill and ball mill at 350 rpm for 5 hours to allow the liquid gallium tin alloy to fully and uniformly coat the surface of the FeF3 / carbon composite particles, thereby obtaining a mixed slurry.

[0086] S3: The ball-milled slurry was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, FeF3 / carbon cathode material modified by liquid gallium tin alloy coating with a mass ratio of FeF3 / carbon composite material to liquid gallium tin alloy of 50:5 was obtained and transferred to a glove box environment for storage.

[0087] Example 8

[0088] This embodiment provides a CuF2 / carbon cathode material modified by liquid metal gallium indium tin alloy coating, denoted as CuF2 / C@GaInSn, and its preparation method includes the following steps:

[0089] S1: In a glove box, add 200 mg of CuF2 / carbon composite material and 20 mg of liquid gallium indium tin alloy to a centrifuge tube, and add 10 mL of anhydrous acetonitrile to the centrifuge tube to obtain a mixture;

[0090] S2: Place the above mixture in an ultrasonic blender and ultrasonically treat it for 30 minutes at a power of 450W to allow the liquid metal gallium indium tin alloy to fully and uniformly coat the surface of CuF2 / carbon composite material particles, thereby obtaining a mixed suspension.

[0091] S3: The ultrasonically treated mixed suspension was transferred to a vacuum oven, and after slowly removing air bubbles by vacuuming, it was dried at 105°C for 8 hours. After cooling to room temperature, CuF2 / carbon cathode material coated with liquid gallium indium tin alloy with a mass ratio of CuF2 / carbon composite material to liquid gallium indium tin alloy of 50:5 was obtained and transferred to a glove box environment for storage.

[0092] Comparative Example 1

[0093] The CuF2 / carbon composite material used in Comparative Document 1 is the same as that in Example 2 but without liquid gallium coating modification, and is denoted as CuF2 / C.

[0094] The X-ray diffraction pattern of the liquid gallium-coated modified CuF2 / carbon cathode material prepared in Example 2 is shown below. Figure 1 As shown. From Figure 1 As can be seen, the gallium-coated modified CuF2 / carbon cathode material retains the crystal structure of CuF2, and the gallium in the material may exist in an amorphous state. Meanwhile, Example 2 was characterized by scanning electron microscopy and EDS mapping, and the experimental results are as follows: Figure 2 , 3 As shown, the CuF2 / C@Ga cathode material exists in the form of nanoparticles, and the gallium element is uniformly distributed on the surface of the CuF2 / carbon composite particles, indicating that liquid gallium metal is uniformly coated on the surface of the CuF2 / carbon composite material.

[0095] A coin cell was prepared using the liquid gallium-coated modified CuF2 / carbon cathode material prepared in Example 2, and the charge-discharge curves are shown below. Figure 4 As shown, tests using a CR2032 coin cell revealed that, within a voltage range of 2.0–4.4V and a current density of 0.02C (the theoretical specific capacity of CuF2 is 528 mAh / g), the initial discharge specific capacity was 490 mAh / g, and after 40 cycles, the charging specific capacity was approximately 109 mAh / g. In contrast, Comparative Example 1, under the same conditions, showed an initial discharge specific capacity of 451 mAh / g at a current density of 0.02C using a CR2032 coin cell, and could not be recharged after the initial discharge. These experimental results demonstrate that the CuF2 / carbon cathode material modified with liquid gallium coating exhibits ideal capacity density, excellent cycle stability, and capacity retention compared to samples without liquid gallium coating modification when used in lithium-ion batteries.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention should not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A liquid metal-coated modified metal fluoride cathode material, characterized in that, The device includes a positive electrode material substrate and a coating layer covering the surface of the positive electrode material substrate. The positive electrode material substrate includes a metal fluoride and a carbon material. The carbon material includes a carbon-based conductive additive. The metal fluoride is located in the gaps of the conductive structure formed by the carbon-based conductive additive material. The coating layer includes a liquid metal. The liquid metal is at least one of gallium or a gallium-based alloy.

2. The liquid metal-coated modified metal fluoride cathode material as described in claim 1, characterized in that, The general chemical formula of the metal fluoride is MF. y M is at least one of Fe, Co, Ni or Cu, and y is 2 or 3.

3. The liquid metal-coated modified metal fluoride cathode material as described in claim 2, characterized in that, The metal fluoride is CuF2, FeF2, or FeF3.

4. The liquid metal-coated modified metal fluoride cathode material as described in claim 1, characterized in that, The gallium-based alloy is a gallium-tin alloy, a gallium-indium alloy, or a gallium-indium-tin alloy.

5. The liquid metal-coated modified metal fluoride cathode material as described in claim 1, characterized in that, The mass ratio of the metal fluoride to the liquid metal is 50:(1~10).

6. A method for preparing a liquid metal-coated modified metal fluoride cathode material as described in any one of claims 1-5, characterized in that, The process includes the following steps: mixing the cathode material matrix, the liquid metal, and the dispersion medium at a temperature higher than the melting point of the liquid metal and performing physical dispersion treatment, so that the liquid metal coats the surface of the cathode material matrix, and after drying, the liquid metal-coated modified metal fluoride cathode material is obtained.

7. The preparation method according to claim 6, characterized in that, The physical dispersion process includes at least one of planetary ball milling, high-energy ball milling, ultrasonic dispersion, high-speed shear dispersion, high-speed grinding, mechanical stirring dispersion, or high-pressure homogenization dispersion.

8. The preparation method according to claim 6, characterized in that, The physical dispersion process is carried out under an inert atmosphere.

9. The preparation method according to claim 6, characterized in that, The drying step is performed at a temperature of 70 ℃-120 ℃ for 6 h-12 h.

10. The preparation method according to claim 6, characterized in that, The dispersion medium is an organic solvent that does not react with the metal fluoride and the liquid metal.

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