Copper sulfide-coated copper fluoride composite material and its preparation method and use

Abstract

The present invention provides a kind of copper sulfide coated copper fluoride composite material and preparation method and use, belong to the field of lithium ion battery technology.The method is ball-milled under an inert atmosphere after a certain amount of sulfur, anhydrous copper fluoride are mixed with an organic solvent according to a mass ratio of 1:9~1:19, wherein the organic solvent is 1 methyl 2 pyrrolidone (NMP), ethylene glycol or ethanol, and the inert gas is nitrogen, argon or neon; After ball-milling, the product is placed under an inert atmosphere and heat-treated after vacuum drying at a certain temperature and time, and finally obtains a copper sulfide-coated copper fluoride cathode material.The method provided by the present invention not only effectively improves the electrochemical performance of copper fluoride cathode material, but also improves the air stability of copper fluoride cathode material, with the advantages of simple synthesis process, good repeatability and strong versatility.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a copper sulfide-coated copper fluoride composite material, a preparation method and uses thereof. Background Art

[0002] Rechargeable lithium batteries are essential power sources for portable appliances, transportation, military equipment, and aerospace. The rapid development of these fields has created promising applications for lithium batteries, while inevitably placing higher demands on their performance. Layered electrode materials are widely used in lithium batteries. These traditional lithium-ion batteries, based on the lithium-ion insertion and extraction mechanism, exhibit excellent cycling performance. However, due to structural limitations, the amount of lithium ions that can be inserted and extracted is limited, and the low theoretical capacity has become a major bottleneck restricting the development of lithium-ion batteries. The search for a new generation of electrode materials to achieve higher energy density is a key trend in the development of lithium-ion batteries.

[0003] Fluorine has the strongest electronegativity in the periodic table. The transition metal fluorides it forms have strong ionic bonds, resulting in a high theoretical discharge platform for battery electrode materials. Fluoride can undergo a multi-electron reversible redox reaction with lithium ions through a conversion mechanism, thereby achieving lithium storage. Among transition metal fluorides, CuF2 is one of the most promising cathode materials due to its high specific capacity (528 mAh / g) and highest theoretical potential (3.55 V). However, in practical applications, the performance of CuF2 cathode materials falls far short of theoretical levels. This is due to the strong ionic nature of the Cu-F bond, which makes CuF2 electronically insulating and exhibits poor electrochemical performance. Furthermore, CuF2 reacts readily with water, forming hydrates or hydroxyl compounds such as CuF2·2H2O or CuOHF upon brief contact with air. The discharge specific energy and voltage platform of these compounds are far below the theoretical values ​​for CuF2, further reducing the electrochemical performance of CuF2 cathode materials. Therefore, improving the conductivity and air stability of CuF2 is crucial for enhancing its practical electrochemical performance. Current research often involves mechanically mixing CuF2 with highly conductive materials, such as carbon materials and metal oxides, to modify it. However, due to poor contact between CuF2 and the introduced materials, the electrochemical performance improvement is limited. Furthermore, the introduced materials do not improve the air stability of CuF2. Furthermore, due to the thermodynamic and kinetic activity of copper fluoride, traditional coating modification methods can easily destroy the copper fluoride material structure, making it impossible to obtain coated copper fluoride materials.

[0004] In response to the above problems, the present invention proposes a method for preparing a copper sulfide-coated copper fluoride positive electrode material. Compared with the existing technology, this method can effectively improve the conductivity and air stability of the copper fluoride positive electrode material. x Copper sulfide is an excellent functional semiconductor material with wide applications in sensors, solar cells, lithium batteries and other fields. Copper sulfide has good electronic conductivity and its conductivity can reach 10 -3 S / cm. The present invention obtains copper fluoride coated with copper sulfide by mixing sulfur and copper fluoride and then heat-treating them under appropriate reaction conditions. This improves the electrical conductivity of copper fluoride, thereby enhancing its electrochemical performance. Simultaneously, the formation of this coating structure also effectively improves the air stability of the copper fluoride material. Summary of the Invention

[0005] The present invention provides a copper sulfide-coated copper fluoride composite material, a preparation method, and uses thereof. When the composite material is used as a positive electrode material for a lithium-ion battery, compared with the prior art, the present method can effectively improve both the conductivity and air stability of the copper fluoride positive electrode material.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for preparing a copper sulfide-coated copper fluoride composite material comprises the following steps:

[0008] S1. Weigh sulfur, anhydrous copper fluoride, and an organic solvent and ball mill them under an inert atmosphere at a constant speed;

[0009] S2. The mixture obtained in step S1 is vacuum dried at a certain temperature and holding time;

[0010] S3. The dried material is heat-treated in an inert atmosphere to obtain a copper sulfide-coated copper fluoride composite material.

[0011] The above-mentioned method for preparing a copper sulfide-coated copper fluoride composite material, in step S1, the mass ratio of sulfur to copper fluoride is 1:9 to 1:19, the organic solvent is any one of 1-methyl-2-pyrrolidone, ethylene glycol, and ethanol, the inert gas is any one of nitrogen, argon, and neon, the ball mill speed is 100 to 600 rpm, and the ball milling time is 30 to 180 min.

[0012] In the above-mentioned method for preparing a copper sulfide-coated copper fluoride composite material, in step S2, the drying temperature is 80-120° C., and the holding time is 300-720 minutes.

[0013] In the above-mentioned method for preparing a copper sulfide-coated copper fluoride composite material, in step S3, the inert gas is any one of nitrogen, argon, and neon, the heat treatment temperature is 120-190° C., and the holding time is 120-1440 min.

[0014] A copper sulfide-coated copper fluoride composite material prepared by the method described in any one of the above is a spherical composite material in which copper fluoride is coated with copper sulfide.

[0015] A copper sulfide-coated copper fluoride composite material prepared by any of the methods described above is used as a positive electrode material for a battery.

[0016] A copper sulfide-coated copper fluoride composite material prepared by the method described in any of the above methods is used as a battery positive electrode material, with copper fluoride as the main material and copper fluoride coated on the outside. It has good air stability, an initial discharge specific capacity of 470 to 600 mAh / g, and an initial discharge specific energy of 1120 to 1600 Wh / kg. After exposure to air for 24 hours, the initial discharge specific capacity decays by 1.2% to 2.8%, and the initial discharge specific energy decays by 1.5% to 4.0%.

[0017] The beneficial effects of the present invention are as follows: this method can coat copper sulfide on the outside of copper fluoride, and when used as a positive electrode material for lithium-ion batteries, it can improve the conductivity and air stability of the copper fluoride positive electrode material; the coating of copper sulfide improves the conductivity of the copper fluoride positive electrode material. At the same time, because the theoretical specific capacity of CuS is greater than that of copper fluoride, within a certain range, as the amount of S added increases, the first discharge specific capacity and first discharge specific energy of the copper sulfide-coated copper fluoride positive electrode material are both improved. In addition, due to the strong insulating properties of S, excessive S residue will be detrimental to the electrochemical properties of copper fluoride. This method not only avoids the adverse effects of S on the electrochemical properties of copper fluoride, but also prevents the destruction of the copper fluoride structure and effectively generates CuS coated on the surface of copper fluoride. This method can not only achieve effective coating of copper sulfide, but also achieve improved conductivity and air stability; adding a suitable organic solvent for ball milling makes it more convenient to mix evenly and improve dispersibility. The invention is environmentally friendly, has low heat treatment temperature, low energy consumption, simple method, easy operation, low equipment requirements, obvious effects of improving conductivity and air stability, good repeatability and strong versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Figures a, b, and c are the X-ray diffraction (XRD) patterns of the CuF2 sample without coating, the CuF2 sample modified with 5 wt% S, and the CuF2 sample modified with 10 wt% S, respectively. Figure 1It can be seen that the XRD patterns of the CuF2 samples modified with 5wt% and 10wt% S show the diffraction peaks of CuS and Cu2S, while no diffraction peak of S is observed, which indicates that the material forms a copper sulfide coating structure.

[0019] Figure 2 Figures a and b show the XRD patterns of uncoated CuF2 and uncoated CuF2 after being exposed to air for 24 hours, respectively. It is clear from the figure that CuF2·2H2O is formed in the uncoated CuF2 after being exposed to air for 24 hours.

[0020] Figure 3 Figures a and b show the XRD patterns of CuF2 modified with 10 wt% S and after 24 hours in air. The coated material is relatively stable in air, retaining its original phase after 24 hours, with virtually no copper fluoride hydrate formation. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings and examples, but the present invention is not limited to the following examples. In the following examples, unless otherwise specified, the reagents are all commercially available chemical reagents.

[0022] When characterizing the electrochemical performance, the positive electrode materials before and after coating were assembled into CR2025 button half-cells.

[0023] Comparative Example 1

[0024] The untreated copper fluoride positive electrode material was tested in the voltage range of 1.5V to 4.2V and the current density of 0.1C. The first discharge specific capacity was 469.7mAh / g and the first discharge specific energy was 1117.7Wh / kg.

[0025] Comparative Example 2

[0026] After being placed in the air for 24 hours, the untreated copper fluoride positive electrode material was tested in the voltage range of 1.5V to 4.2V and the current density of 0.1C. The first discharge specific capacity was 311.7mAh / g and the first discharge specific energy was 551.7Wh / kg.

[0027] Compared with Comparative Example 1, after the material was placed in air for 24 hours, the first discharge specific capacity decayed by 33.6%, and the first discharge specific energy decayed by 50.6%.

[0028] Example 1

[0029] A method for preparing a copper sulfide-coated copper fluoride positive electrode material comprises the following steps: weighing 0.05 g of elemental sulfur and 0.95 g of anhydrous copper fluoride in an argon atmosphere glove box, grinding and pre-mixing them in a mortar. Subsequently, the mixed materials are placed in a ball mill, and an appropriate amount of solvent NMP and zirconium balls are added. The ball mill is set to a speed of 100 rpm and a duration of 180 minutes. After the ball milling process is completed, the material is transferred to a vacuum drying oven and kept at 80°C for 720 minutes. The dried material is heat-treated in an argon atmosphere tubular furnace at a heat treatment temperature of 120°C and a holding time of 1440 minutes. Finally, a copper sulfide-coated copper fluoride positive electrode material is obtained.

[0030] Compared to Comparative Example 1, the CuF2 modified with 5wt% S exhibited an initial discharge capacity of 497.5 mAh / g and an initial discharge energy of 1205.4 Wh / kg at a voltage range of 1.5V to 4.2V and a current density of 0.1C. This demonstrates that the coating enhances the material's conductivity and improves both the initial discharge capacity and energy of the CuF2.

[0031] Example 2

[0032] A method for preparing a copper sulfide-coated copper fluoride positive electrode material comprises the following steps: weighing 0.075g of sublimed sulfur and 0.925g of anhydrous copper fluoride in an argon atmosphere glove box and grinding and premixing them in a mortar. The mixed materials are then placed in a ball mill, and an appropriate amount of solvent ethanol and zirconium balls are added. The ball mill is set to a speed of 600rpm and a duration of 30 minutes. After the ball milling process is completed, the material is transferred to a vacuum drying oven and kept at 120°C for 300 minutes. The dried material is heat-treated in an argon atmosphere tubular furnace at a heat treatment temperature of 190°C for 120 minutes. Finally, a copper sulfide-coated copper fluoride positive electrode material is obtained.

[0033] Compared to Comparative Example 1, the CuF2 modified with 7.5wt% S exhibited an initial discharge capacity of 537.9 mAh / g and an initial discharge energy of 1374.2 Wh / kg at a voltage range of 1.5V to 4.2V and a current density of 0.1C. This demonstrates that the coating enhances the material's conductivity and improves both the initial discharge capacity and energy of the CuF2.

[0034] Example 3

[0035] A method for preparing a copper sulfide-coated copper fluoride positive electrode material comprises the following steps: 0.10 g of sublimed sulfur and 0.90 g of anhydrous copper fluoride are weighed in an argon atmosphere glove box and ground and pre-mixed in a mortar. The mixed materials are then placed in a ball mill, and appropriate amounts of ethylene glycol solvent and zirconium balls are added. The ball mill is set to a speed of 300 rpm and a duration of 120 minutes. After the ball milling process is completed, the material is transferred to a vacuum drying oven and heated at 100°C for 500 minutes. The dried material is heat-treated in an argon atmosphere tubular furnace at a heat treatment temperature of 155°C for 720 minutes. Finally, a copper sulfide-coated copper fluoride positive electrode material is obtained.

[0036] Compared with Comparative Example 1, the CuF2 after 10wt% S composite modification was tested in the voltage range of 1.5V~4.2V and the current density of 0.1C. The first discharge specific capacity was 574.3mAh / g, and the first discharge specific energy was 1568.5Wh / kg, indicating that the conductivity of the material was improved after coating, and the first discharge specific capacity and first discharge specific energy of CuF2 were improved.

[0037] Example 4

[0038] A method for preparing a copper sulfide-coated copper fluoride positive electrode material comprises the following steps: weighing 0.05 g of elemental sulfur and 0.95 g of anhydrous copper fluoride in an argon atmosphere glove box, grinding and pre-mixing them in a mortar. Subsequently, the mixed materials are placed in a ball mill, and an appropriate amount of solvent NMP and zirconium balls are added. The ball mill is set to a speed of 100 rpm and a duration of 180 minutes. After the ball milling process is completed, the material is transferred to a vacuum drying oven and kept at 80°C for 720 minutes. The dried material is heat-treated in an argon atmosphere tubular furnace at a heat treatment temperature of 120°C and a holding time of 1440 minutes. Finally, a copper sulfide-coated copper fluoride positive electrode material is obtained, and the obtained material is exposed to air for 24 hours before battery assembly.

[0039] Compared to Example 1, after 24 hours of exposure to air, the 5wt% S-coated CuF2 exhibited an initial discharge capacity of 485.3 mAh / g and an initial discharge energy of 1159.8 Wh / kg at a current density of 0.1C over a voltage range of 1.5V to 4.2V. The initial discharge capacity decayed by 2.5%, and the initial discharge energy decayed by 3.8%, indicating that the coating improved the air stability of CuF2.

[0040] Example 5

[0041] A method for preparing a copper sulfide-coated copper fluoride positive electrode material comprises the following steps: 0.075 g of sublimed sulfur and 0.925 g of anhydrous copper fluoride are weighed in an argon atmosphere glove box and ground and pre-mixed in a mortar. The mixed materials are then placed in a ball mill, and an appropriate amount of solvent ethanol and zirconium balls are added. The ball mill is set to a speed of 600 rpm and a duration of 30 minutes. After the ball milling process is completed, the material is transferred to a vacuum drying oven and kept at 120°C for 300 minutes. The dried material is heat-treated in an argon atmosphere tube furnace at a heat treatment temperature of 190°C for 120 minutes. Finally, a copper sulfide-coated copper fluoride positive electrode material is obtained, and the obtained material is exposed to air for 24 hours before battery assembly.

[0042] Compared to Example 2, after 24 hours of exposure to air, the CuF2 modified with 7.5 wt% S exhibited an initial discharge capacity of 526.2 mAh / g and an initial discharge energy of 1335.5 Wh / kg at a current density of 0.1 C over a voltage range of 1.5 V to 4.2 V. The initial discharge capacity decayed by 2.2%, and the initial discharge energy decayed by 2.8%, indicating that the coating improved the air stability of the CuF2.

[0043] Example 6

[0044] A method for preparing a copper sulfide-coated copper fluoride positive electrode material comprises the following steps: 0.10 g of sublimed sulfur and 0.90 g of anhydrous copper fluoride are weighed in an argon atmosphere glove box and pre-mixed by grinding in a mortar. The mixed materials are then placed in a ball mill, and appropriate amounts of ethylene glycol solvent and zirconium balls are added. The ball mill is set to a speed of 300 rpm and a duration of 120 minutes. After the ball milling process, the material is transferred to a vacuum drying oven and heated at 100°C for 500 minutes. The dried material is then heat-treated in an argon atmosphere tube furnace at 155°C for 720 minutes. The resulting copper sulfide-coated copper fluoride positive electrode material is obtained. The resulting material is exposed to air for 24 hours before battery assembly.

[0045] Compared to Example 3, after 24 hours of exposure to air, the 10wt% S-composite-modified CuF2 exhibited an initial discharge capacity of 565.1 mAh / g and an initial discharge energy of 1540.6 Wh / kg at a voltage range of 1.5V to 4.2V and a current density of 0.1C. The initial discharge capacity decayed by 1.6%, and the initial discharge energy decayed by 1.8%, indicating that the coating improved the air stability of CuF2.

[0046] The above description is only a preferred embodiment of the present invention and does not limit the present invention. It should be pointed out that any modifications, replacements, etc. within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a copper sulfide-coated copper fluoride composite material, characterized in that: The steps include: S1. Weigh sulfur, anhydrous copper fluoride, and an organic solvent and ball mill them under an inert atmosphere at a constant speed; S2 the mixture obtained in step S1 is vacuum dried at a certain temperature and holding time; S3. The dried material is heat-treated in an inert atmosphere to obtain a copper sulfide-coated copper fluoride composite material, wherein the heat treatment temperature is 155-190° C. and the holding time is 120-1440 min.

2. The method for preparing a copper sulfide-coated copper fluoride composite material according to claim 1, characterized in that: In step S1, the mass ratio of sulfur to copper fluoride is 1:9 to 1:19, the organic solvent is any one of 1-methyl-2-pyrrolidone, ethylene glycol, and ethanol, and the inert atmosphere is any one of nitrogen, argon, and neon.

3. The method for preparing a copper sulfide-coated copper fluoride composite material according to claim 1, characterized in that: In step S2, the drying temperature is 80-120° C., and the holding time is 300-720 min.

4. The method for preparing a copper sulfide-coated copper fluoride composite material according to claim 1, characterized in that: In step S3, the inert atmosphere is any one of nitrogen, argon, and neon.

5. A copper sulfide-coated copper fluoride composite material prepared by the method according to any one of claims 1 to 4, characterized in that: The composite material is a spherical composite material in which copper fluoride is coated with copper sulfide.

6. A copper sulfide-coated copper fluoride composite material prepared by the method according to any one of claims 1 to 4 is used as a battery positive electrode material.

7. The copper sulfide-coated copper fluoride composite material according to claim 5, characterized in that: Used as battery positive electrode material, copper fluoride is the main material, and copper fluoride is coated with copper sulfide. It has good air stability, the first discharge specific capacity is 470~600mAh / g, the first discharge specific energy is 1120~1600Wh / kg. After exposure to air for 24 hours, the first discharge specific capacity decays by 1.2%~2.8%, and the first discharge specific energy decays by 1.5%~4.0%.

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