Carbon-based self-supporting electrode material, preparation method and application

Abstract

The invention relates to a negative electrode material of a battery, in particular to a carbon-based self-supporting electrode material, a preparation method and application, the self-supporting electrode material comprises carbon fibers and transition metal particles distributed on the carbon fibers; the metal particles exist in a metal elementary substance particle state and are any one or more of cobalt, iron and nickel; the self-supporting electrode material comprises the following components in percentage by weight: 58-95 wt% of carbon and 5-42 wt% of transition metal particles. According to the carbon-based self-supporting electrode material, the preparation method and the application, the preparation method is simple and convenient, and the stability is high.

Description

Technical Field

[0001] This invention relates to a negative electrode material for batteries, and more particularly to a carbon-based self-supporting electrode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic products, but the energy density of currently commercialized lithium-ion batteries lags behind the needs of high-energy-consuming devices. The energy storage mechanism of lithium-ion batteries is similar to that of sodium-ion batteries: carbon-based anode materials such as graphite store lithium through intercalation, resulting in low capacity and a tendency to expand and pulverize; anode materials based on alloys and conversion mechanisms can provide high capacity but suffer from poor stability. Therefore, developing novel electrode materials with high capacity and good stability is a cutting-edge scientific issue for advancing the development of next-generation high-performance energy storage devices.

[0003] A newly developed in-situ magnetic testing technique reveals the "interfacial space charge" energy storage mechanism of transition metal elements in lithium-ion batteries. This mechanism boasts advantages such as high capacity, fast ion transport speed with no volume change, and good stability, making it a promising candidate for next-generation lithium-ion battery anode materials. Carbon-based electrode materials, due to their excellent conductivity, chemical stability, and abundant porous structure, have broad application prospects in energy storage and conversion fields such as supercapacitors and batteries. Self-supporting electrode materials eliminate the need for binders and current collectors, effectively improving the energy density and power density of the electrode, simplifying the electrode fabrication process, and reducing costs. However, existing methods for preparing carbon-based self-supporting electrode materials often suffer from complex processes, high costs, and uneven metal loading, limiting their large-scale application. Therefore, developing a low-cost, simple, and high-performance method for preparing self-supporting electrode materials is of great significance. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a carbon-based self-supporting electrode material, its preparation method, and its application.

[0005] One of the objectives of this invention is to provide a carbon-based self-supporting electrode material, which includes carbon fibers and transition metal particles distributed on the carbon fibers; the metal particles exist in the state of elemental metal particles, which are any one or more of cobalt, iron and nickel; by weight percentage, the self-supporting electrode material includes 58-95 wt% carbon and 5-42 wt% transition metal particles.

[0006] The second objective of this invention is to provide a method for preparing a carbon-based self-supporting electrode material, comprising the following steps: (S1) Cut the pure cotton fabric to a suitable size, then rinse it multiple times with deionized water and anhydrous ethanol. During each rinse, the temperature of the rinsing solution should be controlled between 20 and 30°C to avoid damage to the fiber structure due to excessively high temperature or affecting the rinsing effect due to excessively low temperature. Remove surface impurities, oil stains, and other possible contaminants; the pure cotton fabric mentioned above can be commercially available pure cotton face towels.

[0007] (S2) The pretreated pure cotton fabric is dried at high temperature to obtain carbon fiber membrane.

[0008] (S3) The carbon fiber membrane is placed in a metal salt solution and ultrasonically treated to allow the carbon fiber membrane to fully contact and react with the metal salt solution, and to allow the transition metal salt solution to fully penetrate into the carbon fiber membrane, ensuring uniform distribution of metal ions; then it is freeze-dried and vacuum-dried to obtain the composite film precursor.

[0009] (S4) In order to obtain a carbon fiber film with attached metal particles, the carbon fiber film precursor film is placed in a tube furnace and the composite film precursor is calcined at high temperature in an inert gas atmosphere to obtain a carbon-based self-supporting electrode material. The argon atmosphere can prevent the carbon-based material from being oxidized at high temperature. The carbonization process transforms the CT-Co film into a carbon-based material with specific structure and properties, and makes the metal particles uniformly loaded on the carbon-based film.

[0010] Preferably, the metal salt solution is composed of a metal salt compound and a solvent, wherein the metal salt compound is any one or more of cobalt salt, iron salt, and nickel salt; the cobalt salt includes any one or more of cobalt nitrate, cobalt chloride, and cobalt acetate; the iron salt includes any one or more of ferric nitrate, ferric chloride, and ferric sulfate; and the nickel salt includes any one or more of nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate; and the solvent is any one or more of N,N-dimethylformamide, methanol, ethanol, deionized water, and tetrahydrofuran.

[0011] Preferably, the concentration of the metal salt solution is 0.02~0.1 mmol·L⁻¹.

[0012] Preferably, in step (S3), the room temperature ultrasonic treatment frequency is 20~30Hz and the time is 1~2h. Within this ultrasonic parameter range, the interaction between transition metal ions and active sites on the surface of the carbon fiber of the washcloth can be effectively promoted, forming stable chemical bonds or physical adsorption, while avoiding damage to the membrane structure due to excessive ultrasonic energy; the vacuum degree during vacuum drying is 50~500Pa; the freeze-drying temperature is -55~-30℃ and the time is 24~72h. Specifically, the carbon fiber membrane soaked in the transition metal salt solution is rapidly transferred to liquid nitrogen. The low temperature of liquid nitrogen can completely freeze the carbon fiber membrane in a very short time, fixing the distribution state of metal ions in the membrane; the frozen carbon fiber membrane is freeze-dried for 24~72h to remove moisture from the membrane; then, it is vacuum-dried at 60~90℃ for 8~12h to further ensure the dryness of the membrane, obtaining a carbon fiber membrane precursor loaded with metal ions. The transfer time of the carbon fiber membrane soaked in the transition metal salt solution to the freeze dryer should not exceed 1 minute to ensure rapid cooling and freezing. This avoids changes in the internal structure caused by slow cooling, which could affect the performance of subsequent products. Simultaneously, the transfer process must be carried out in a dry and clean environment to prevent contamination from external impurities. During freeze-drying, moisture can be removed from the frozen carbon fiber membrane through sublimation, while maintaining the membrane's porous structure and fiber morphology, preventing cracking or deformation of the membrane due to stress changes during drying. Preferably, in step (S2), the heating rate during drying is 10~20℃ / min, the drying temperature is 60~90℃, and the drying time is 8~12h.

[0013] Preferably, the calcination temperature is 600~1000℃, and the heating rate is 1~10. o The temperature is C / min, and the time is 1~5h; the inert gas is selected from any one or more of N2, Ar, and Ar / H2 (90% / 10%) mixtures. A suitable gas flow rate can effectively remove the gaseous products generated during the reaction, ensuring that the carbonization process takes place in an oxygen-free inert environment and preventing the membrane from being oxidized at high temperatures; a suitable heating rate helps to control the progress of the carbonization reaction, allowing the membrane to gradually form a uniform and stable carbon skeleton structure at high temperatures.

[0014] Metal elements exist in the carbon skeleton in the form of uniformly dispersed nanoparticles or nanoclusters. The loading of transition metal elements can be precisely controlled by adjusting parameters such as the concentration of metal salt solution and immersion time, thereby achieving regulation of the physicochemical properties and performance of the membrane.

[0015] The third objective of this invention is to provide an application of a carbon-based self-supporting electrode material, that is, to apply it to a battery, and more specifically, to apply it to the negative electrode of a battery.

[0016] The present invention has the following technical effects: (1) The present invention uses commercially available pure cotton material as a self-supporting carbon source skeleton. On the one hand, the raw materials are readily available and the cost is low. On the other hand, the self-supporting structure avoids the cumbersome coating process of traditional electrodes and simplifies the production process.

[0017] (2) The present invention uses ultrasonic loading and freeze drying methods to achieve uniform dispersion of transition metal particles in the carbon fiber skeleton in the transition metal particle / carbon composite membrane. The loading amount of transition metal elements can be precisely controlled by adjusting parameters such as the concentration of metal salt solution and impregnation time, thereby achieving regulation of the physicochemical properties and performance of the membrane.

[0018] (3) The carbon-based self-supporting electrode material supported by transition metal particles of the present invention has abundant microporous / mesoporous structures and a specific surface area of ​​up to 850 cm². 2 / g, compared to the traditional physical spraying method for preparing flexible electrodes from powdered active materials, does not require the addition of binders and conductive agents, and can achieve a more stable load structure and electronic conductivity.

[0019] (4) The uniform loading of transition metal particles onto a carbon fiber self-supporting electrode of the present invention exhibits good electrochemical performance in lithium-ion batteries: at 0~3.0V, Li / Li + Within the voltage range, after 1000 charge-discharge cycles at a current density of 100 mAh / g, it still maintains a capacity retention rate of over 78%, demonstrating excellent cycle stability. Attached Figure Description

[0020] Figure 1 The bending state of the self-supporting carbon-based thin film doped with Co particles according to Embodiment 1 of the present invention is shown in the actual photograph. Figure 2 The XRD pattern of a self-supporting carbon-based thin film doped with Co particles according to Embodiment 1 of the present invention is shown. Figure 3 The TG diagram of a self-supporting carbon-based thin film doped with Co particles according to Embodiment 1 of the present invention is shown. Figure 4 The TG diagram of a self-supporting carbon-based thin film doped with Fe particles according to Embodiment 1 of the present invention is shown. Detailed Implementation

[0021] The principles and features of the present invention are described below with reference to embodiments; the examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0022] Example 1: A method for preparing a carbon-based self-supporting electrode material includes the following steps: (S1) Take a thickened pure cotton face towel from PurCotton and cut a circular piece with a diameter of 5cm. Rinse it three times with deionized water and anhydrous ethanol in sequence, and dry it overnight at 60℃ to obtain a clean and impurity-free carbon fiber membrane.

[0023] (S2) The carbon fiber membrane after the above treatment was placed in a 200 ml cobalt chloride solution with a concentration of 0.05 mmol·L⁻¹ and ultrasonically treated for 1 h under the conditions of ultrasonic power of 100 W and frequency of 25 Hz. The carbon fiber membrane turned light pink. (S3) The ultrasonically treated carbon fiber membrane was transferred to a freeze dryer and the freezing conditions were: -50℃. After 48 hours, it was taken out and vacuum dried at 60℃ for 12 hours to obtain the carbon fiber membrane precursor. (S4) The carbon fiber membrane precursor is placed in a tube furnace and heated to 900°C at a heating rate of 50 mL / min in an argon atmosphere for 3 hours to obtain a self-supporting carbon thin film material doped with elemental Co particles. Then, it is punched on a slicer to obtain a circular electrode sheet with a diameter of 12 mm for later use.

[0024] A real-world photograph of the bending state of a self-supporting carbon-based thin film doped with metallic Co particles is shown below. Figure 1 It exhibits good mechanical flexibility, meeting the requirements for the fabrication of flexible lithium-ion batteries. The XRD pattern of the self-supporting carbon-based thin film doped with Co particles is shown below. Figure 2 The distinct Co peak positions indicate the successful formation of elemental Co particles on the carbon fiber surface, and the mass content of Co was calculated to be approximately 12.48 wt% using TG testing (e.g., Figure 3 The average particle size of metallic Co particles is 30~200 nm.

[0025] Example 2: The difference from Example 1 is that cobalt chloride is replaced with ferric chloride solution, while the other operation steps are the same, to prepare a self-supporting carbon thin film material doped with elemental Fe particles.

[0026] like Figure 4 The mass content of Fe metal was calculated to be approximately 9.09 wt% through TG testing.

[0027] Example 3: The difference from Example 1 is that nickel chloride is replaced with ferric chloride solution, while the other operation steps are the same, to prepare a self-supporting carbon thin film material doped with elemental Ni particles.

[0028] The mass content of metallic Ni was calculated to be approximately 8.14 wt% based on TG testing.

[0029] Example 4: The difference from Example 1 is that cobalt chloride is replaced with cobalt acetate solution, while the other operation steps are the same, to prepare a self-supporting carbon thin film material doped with elemental Co particles.

[0030] Example 5: The difference from Example 1 is that the 0.05 mmol·L⁻¹ cobalt chloride solution was replaced with 0.02 mmol·L⁻¹, while the other operating steps were the same, and a self-supporting carbon thin film material doped with elemental Co particles was prepared.

[0031] Example 6: The difference from Example 1 is that the 0.05 mmol·L⁻¹ cobalt chloride solution was replaced with 0.1 mmol·L⁻¹, while the other operating steps were the same, and a self-supporting carbon thin film material doped with elemental Co particles was prepared.

[0032] Example 7: The difference from Example 1 is that the ultrasonic treatment time is changed to 0.5h, while the other operation steps are the same, and a self-supporting carbon thin film material doped with elemental Co particles is prepared.

[0033] Example 8: The difference from Example 1 is that the ultrasonic treatment time is changed to 3 hours, while the other operation steps are the same, and a self-supporting carbon thin film material doped with elemental Co particles is prepared.

[0034] Comparative Example 1: The difference from Example 1 is that step (2) is not required, while the remaining steps are the same, and a pure carbon self-supporting thin film material without metal particles attached is obtained.

[0035] Comparative Example 2: The difference in Example 1 is that the gas flow rate is 20 mL / min, while the other operation steps are the same, and a self-supporting carbon thin film material doped with Co / Co3O4 particles is prepared.

[0036] Comparative Example 3: The difference from Example 1 is that the 0.05 mmol·L⁻¹ cobalt chloride solution was replaced with 0.12 mmol·L⁻¹, while the other operating steps were the same. However, a flexible self-supporting electrode material could not be obtained.

[0037] The self-supporting electrode materials used to assemble button lithium-ion half-cells in all the above embodiments and comparative examples employ the following steps: A CR-2032 stainless steel button cell battery was assembled in an argon-protected glove box in an anhydrous and oxygen-free environment (water / oxygen content ≤0.01ppm). The assembly followed the order of positive electrode shell, working electrode, electrolyte (LiFP6 / EC+DMC+DEC+2%FEC), separator, lithium sheet, gasket, spring, and negative electrode shell. The device was sealed under a pressure not exceeding 0.5MPa to obtain a lithium-ion half-cell. The electrode materials of Examples 1-5 and Comparative Examples 1-2 were cycled 1000 times at a current density of 100mA / g, and the results are shown in Table 1.

[0038] Table 1. Performance of electrode materials in Examples 1-5 and Comparative Examples 1-2 after 1000 cycles at a current density of 100 mA / g. As can be seen from the table above, Examples 1 to 8 and Comparative Examples 1 to 2 all showed a significant improvement in battery capacity retention, indicating that they have good stability.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A carbon-based self-supporting electrode material, characterized in that, The self-supporting electrode material comprises carbon fibers and transition metal particles distributed on the carbon fibers; the metal particles exist in the state of elemental metal particles, which are any one or more of cobalt, iron and nickel; by weight percentage, the self-supporting electrode material comprises 58-95 wt% carbon and 5-42 wt% transition metal particles.

2. A method for preparing a carbon-based self-supporting electrode material, characterized in that, Includes the following steps: (S1) Cut the pure cotton fabric into appropriate sizes, and then rinse it multiple times with deionized water and anhydrous ethanol to remove surface impurities, oil stains and other possible contaminants; (S2) The pretreated pure cotton fabric is dried at high temperature to obtain carbon fiber membrane; (S3) The carbon fiber membrane is placed in a metal salt solution and ultrasonically treated to ensure that the carbon fiber membrane and the metal salt solution are in full contact and react; then it is freeze-dried and vacuum-dried to obtain the composite film precursor. (S4) The composite thin film precursor is calcined at high temperature in an inert gas atmosphere to obtain a carbon-based self-supporting electrode material.

3. The method for preparing the carbon-based self-supporting electrode material according to claim 2, characterized in that, The metal salt solution is composed of a metal salt compound and a solvent. The metal salt compound is any one or more of cobalt salts, iron salts, and nickel salts. The cobalt salt includes any one or more of cobalt nitrate, cobalt chloride, and cobalt acetate. The iron salt includes any one or more of ferric nitrate, ferric chloride, and ferric sulfate. The nickel salt includes any one or more of nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate. The solvent is any one or more of N,N-dimethylformamide, methanol, ethanol, deionized water, and tetrahydrofuran.

4. The method for preparing the carbon-based self-supporting electrode material according to claim 2, characterized in that, The concentration of the metal salt solution is 0.02~0.1 mmol·L⁻¹.

5. The method for preparing the carbon-based self-supporting electrode material according to claim 2, characterized in that, In step (S3), the room temperature ultrasonic treatment frequency is 20~30Hz and the time is 1~2h; the vacuum degree during vacuum drying is 50~500Pa; and the freeze-drying temperature is -55~-30℃ and the time is 24~72h.

6. The method for preparing the carbon-based self-supporting electrode material according to claim 2, characterized in that, In step (S2), the heating rate during drying is 10~20℃ / min, the drying temperature is 60~90℃, and the time is 8~12h.

7. The method for preparing the carbon-based self-supporting electrode material according to claim 2, characterized in that, The calcination temperature is 600~1000℃, the heating rate is 1~10℃ / min, and the time is 1~5h; the inert gas is selected from any one or more of N2, Ar and Ar / H2 (90% / 10%) mixture.

8. A negative electrode sheet for a battery, made of a carbon-based self-supporting electrode material.

9. A battery comprising a positive electrode, a separator, and a negative electrode, characterized in that, The negative electrode sheet is the negative electrode sheet as described in claim 8.

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