Silicon-oxygen negative electrode material, preparation method and application thereof

Abstract

The application relates to the technical field of battery materials, and particularly discloses a silicon-oxygen negative electrode material, a preparation method and application thereof. The silicon-oxygen material is coated by adopting a'secondary ethyne carbon coating' process, the deposition conditions of ethyne cracking are accurately controlled, the fluorides remaining on the surface of the active substance are fully coated by the secondary carbon layer, direct contact between the fluorides and the electrolyte is isolated, and the high-temperature storage stability of the material is significantly improved. The battery prepared by adopting the material provided by the application has a highest high-temperature storage initial efficiency of 71%, and the high-temperature storage capacity retention rate of a comparative sample (fluoride exposure) without secondary ethyne carbon coating treatment is only 61%. It is shown that the growth range of the interface impedance of the material provided by the application is significantly reduced after high-temperature storage, and it is shown that the interface side reaction is effectively inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly relates to a silicon-oxygen anode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of new energy vehicles and large-scale energy storage markets, higher and higher requirements are put forward for the energy density of lithium-ion batteries. Currently, the commercially available graphite anode material is difficult to meet the development needs of high-energy density batteries due to its limited theoretical specific capacity (372 mAh / g). Silicon-based materials are considered to be one of the most promising anode materials for next-generation lithium-ion batteries due to their extremely high theoretical specific capacity (about 4200 mAh / g), suitable lithium intercalation potential, and rich resource reserves. Among them, silicon-oxygen materials (SiO x , 0 < x < 2) can effectively buffer the volume expansion of silicon during the lithium deintercalation and intercalation processes because Li2O and lithium silicate are generated during the first lithium intercalation process, and their cycle stability is better than that of pure silicon materials, so they have been commercially applied first.

[0003] However, silicon-oxygen materials themselves also have problems such as poor conductivity and low initial Coulomb efficiency. To address the defect of poor conductivity, the prior art generally uses surface carbon coating for modification, that is, a conductive carbon layer is formed on the surface of silicon-oxygen particles to reduce the lithium intercalation barrier and improve the kinetic performance of the material. Commonly used carbon coating methods include solid-phase coating (such as pitch pyrolytic carbon coating), liquid-phase coating (such as organic carbon source carbonization coating), and gas-phase coating (such as chemical vapor deposition), etc. However, in practical applications, even for silicon-oxygen materials treated by carbon coating, their high-temperature storage performance often fails to meet the standards, seriously affecting the calendar life and reliability of the battery. Therefore, how to further improve the high-temperature storage performance of silicon-oxygen anode materials has become a technical problem亟待解决 in this field.

[0004] Chinese Patent Document CN105958036A discloses a preparation method of a carbon-coated silicon anode material for a lithium-ion battery, which uses a two-step carbon coating process: first, silicon powder is dispersed in liquid and mixed with the first carbon coating layer material, and after drying, it is carbonized at high temperature to obtain primary carbon-coated silicon material; then, a dispersion liquid of the second carbon coating material is prepared, and the primary carbon-coated silicon material is dispersed therein, dried again and subjected to secondary roasting to obtain a secondary carbon-coated silicon anode material. This technical solution aims to improve the conductivity and cycle stability of silicon materials through a double-layer carbon coating structure. However, it is difficult to achieve complete coating of silicon-oxygen particles by the above carbon coating process, especially the coating effect on specific active sites (such as fluoride doping regions or residues) on the particle surface is not good. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a silicon-oxygen anode material, its preparation method, and its application. The present invention proposes to use a "secondary acetylene carbon coating" process to coat silicon-oxygen materials. By precisely controlling the acetylene pyrolysis deposition conditions, the residual fluoride on the surface of the active material is fully coated by the secondary carbon layer, thereby isolating the fluoride from direct contact with the electrolyte and significantly improving the high-temperature storage stability of the material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix silicon suboxide and fluoride evenly to obtain a mixture; S2. Add asphalt to the mixture for liquid phase coating, and then calcine to obtain calcined material; S3. The calcined material is subjected to air jet milling to obtain depolymerized material; S4. Using acetylene as a carbon source, the obtained depolymerized material is coated with carbon by chemical vapor deposition to obtain a coated material; S5. The obtained coating material is subjected to air jet pulverization to obtain the silicon-oxygen anode material.

[0007] In the technical solution disclosed in this invention, in step S1, the mass ratio of silicon suboxide to fluoride is 4-8:1.

[0008] In the technical solution disclosed in this invention, in step S1, the size D50 of the silicon suboxide powder is 5-6 μm.

[0009] In the technical solution disclosed in this invention, in step S1, the fluoride is selected from one or more of LiF, MgF2, CaF3, and TiF3.

[0010] In the technical solution disclosed in this invention, in step S2, the mass ratio of the mixture to the asphalt is 100:5-10.

[0011] In the technical solution disclosed in this invention, in step S2, the calcination temperature is 800-1000℃ and the calcination time is 4-6h.

[0012] In the technical solution disclosed in this invention, in step S3, the airflow pulverizing pressure is 0.2-0.3 MPa.

[0013] In the technical solution disclosed in this invention, the specific process of chemical vapor deposition in step S4 is as follows: the obtained depolymerized material is placed in a CVD furnace, and then the CVD furnace is heated to 800-900℃, and acetylene is introduced at a rate of 0.01-0.05L / min to obtain the coating material.

[0014] In the technical solution disclosed in this invention, in step S5, the airflow pulverizing pressure is 0.2-0.3 MPa.

[0015] The present invention provides a silicon-oxygen anode material prepared by the above preparation method.

[0016] The present invention also provides the application of the above-mentioned silicon-oxygen anode material in the preparation of lithium battery electrode materials.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a "secondary acetylene carbon coating" process to coat silicon-oxygen materials. By precisely controlling the acetylene pyrolysis deposition conditions, the residual fluorides on the surface of the active material are fully coated by the secondary carbon layer, thereby isolating the fluorides from direct contact with the electrolyte and significantly improving the high-temperature storage stability of the material. Attached Figure Description

[0018] Figure 1 This is an elemental distribution diagram of the silicon-oxygen anode material prepared in Example 1 of the present invention; Figure 2 The elemental distribution diagram is shown for the silicon-oxygen anode material prepared in Comparative Example 1. Detailed Implementation

[0019] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0020] It should be noted that, unless otherwise specified, all chemical reagents involved in this invention were purchased through commercial channels.

[0021] The silicon suboxide powder used in the embodiments of the present invention has a size D50 of 5-6 μm; The asphalt is a medium-temperature asphalt with a softening point of 110-120℃.

[0022] Example 1 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the depolymerized material; S4. Place the obtained depolymerized material into a CVD furnace, then heat the CVD furnace to 850℃, and introduce acetylene at a rate of 0.02L / min for 24min to obtain the coated material with a coating amount of 0.1%. S5. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0023] Example 2 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the depolymerized material; S4. Place the obtained depolymerized material into a CVD furnace, then heat the CVD furnace to 850℃, and introduce acetylene at a rate of 0.02L / min for 48min to obtain the coated material with a coating amount of 0.2%. S5. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0024] Example 3 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the depolymerized material; S4. Place the obtained depolymerized material into a CVD furnace, then heat the CVD furnace to 850℃, and introduce acetylene at a rate of 0.02L / min for 72min to obtain the coated material with a coating amount of 0.3%. S5. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0025] Example 4 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the depolymerized material; S4. Place the obtained depolymerized material into a CVD furnace, then heat the CVD furnace to 850℃, and introduce acetylene at a rate of 0.02L / min for 120min to obtain the coated material with a coating amount of 0.5%. S5. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0026] Example 5 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the depolymerized material; S4. Place the obtained depolymerized material into a CVD furnace, then heat the CVD furnace to 850℃, and introduce acetylene at a rate of 0.02L / min for 168min to obtain the coated material with a coating amount of 0.7%. S5. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0027] Example 6 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the depolymerized material; S4. Place the obtained depolymerized material into a CVD furnace, then heat the CVD furnace to 850℃, and introduce acetylene at a rate of 0.02 L / min for 240 min to obtain the coated material with a coating amount of 1.0%. S5. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0028] Comparative Example 1 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to airflow pulverization at a pressure of 0.2 MPa to obtain silicon-oxygen anode material; Comparative Example 2 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. Place the obtained mixture into a CVD furnace, then heat the CVD furnace to 850℃, and introduce acetylene at a rate of 0.02L / min for 24min to obtain the coating material. S3. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0029] Comparative Example 3 A method for preparing a silicon-oxygen anode material includes the following steps: S1. Mix 100g of silicon suboxide and 20g of lithium fluoride evenly to obtain a mixture; S2. After liquid-coating 100g of mixture with 7g of asphalt, put it into a calcining furnace and heat it from room temperature to 800℃ at a heating rate of 5℃ / min for 6 hours to obtain calcined material. S3. The calcined material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the depolymerized material; S4. Place the obtained depolymerized material into a CVD furnace, then heat the CVD furnace to 850℃, and introduce methane at a rate of 0.02L / min for 24min to obtain the coated material with a coating amount of 0.1%. S5. The obtained coating material is subjected to air jet pulverization at a pressure of 0.2 MPa to obtain the silicon-oxygen anode material.

[0030] The elemental distribution diagram of the silicon-oxygen anode material prepared in Example 1 of this invention is as follows: Figure 1 As shown, the elemental distribution diagram of the silicon-oxygen anode material prepared in Comparative Example 1 is as follows. Figure 2 As shown, through comparison Figure 1 and Figure 2 As is known, through secondary acetylene carbon coating treatment, the carbon layer can be selectively deposited on the fluoride exposed area, forming a complete coating of the fluoride. After treatment, the signal intensity of fluorine on the material surface is significantly reduced, the fluoride is effectively covered by the carbon layer, and direct contact with the electrolyte is completely isolated.

[0031] The electrochemical performance of the silicon-oxygen anode materials prepared in Examples 1-6 and Comparative Examples 1-3 of the present invention was tested, as follows: Preparation of negative electrode sheet: The silicon-oxygen negative electrode materials prepared in Examples 1-6 and Comparative Examples 1-3 were mixed with conductive carbon black and sodium carboxymethyl cellulose in a ratio of 8:1:1. After adding solvent water and ethanol and grinding thoroughly, the mixture was coated on copper foil, dried in an oven, and then cut into round pieces with a diameter of 12 mm and placed in a glove box for later use.

[0032] The positive electrode is a lithium sheet.

[0033] The electrolyte is EC / DEC = 1:1 (volume ratio), 10 vol% FEC, and 1 vol% VC.

[0034] Battery testing: Battery testing is mainly conducted on the Xinwei testing software at a test temperature of 30℃.

[0035] The test results are shown in Table 1: Table 1. Electrochemical performance test results for different groups As can be seen from the table, the high-temperature storage efficiency of the battery material provided by this invention is improved after secondary carbon coating, but the efficiency decreases with increasing acetylene content. This is because acetylene carbon has a higher defect rate than pitch carbon. Excessive acetylene carbon introduction drastically reduces the mass and volume fraction of the active material in the composite electrode, leading to a significant decrease in the overall areal capacity and volumetric energy density of the electrode, thus reducing the efficiency. The data after using methane carbon is lower than that after using acetylene carbon because acetylene carbon can form a relatively smooth carbon layer, which more effectively reduces the contact area between the active material and the electrolyte.

[0036] The silicon-oxygen anode material prepared in this invention was assembled into a coin cell and subjected to high-temperature storage tests (storage at 60°C for 5 days). The results showed that the battery prepared using the material of this invention achieved a maximum initial efficiency of 71% during high-temperature storage, while the control sample (fluoride exposed) without secondary acetylene carbon coating treatment only retained 61% of its capacity during high-temperature storage. This indicates that the interfacial impedance growth of the material of this invention is significantly reduced after high-temperature storage, suggesting that interfacial side reactions are effectively suppressed.

[0037] Finally, it should be noted that the above embodiments do not limit the present invention in any way. Those skilled in the art can make modifications and improvements based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a silicon-oxygen anode material, characterized in that, Includes the following steps: S1. Mix silicon suboxide and fluoride evenly to obtain a mixture; S2. Add asphalt to the mixture for liquid phase coating, and then calcine to obtain calcined material; S3. The calcined material is subjected to air jet milling to obtain depolymerized material; S4. Using acetylene as a carbon source, the obtained depolymerized material is coated with carbon by chemical vapor deposition to obtain a coated material; S5. The obtained coating material is subjected to air jet pulverization to obtain the silicon-oxygen anode material.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of silicon suboxide to fluoride is 4-8:

1.

3. The preparation method according to claim 1, characterized in that, In step S1, the fluoride is selected from one or more of LiF, MgF2, CaF3, and TiF3.

4. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of the mixture to the asphalt is 100:5-10.

5. The preparation method according to claim 1, characterized in that, In step S2, the calcination temperature is 800-1000℃ and the calcination time is 4-6h.

6. The preparation method according to claim 1, characterized in that, In steps S3 and S5, the airflow pulverizing pressure is 0.2-0.3 MPa.

7. The preparation method according to claim 1, characterized in that, In step S4, the specific process of chemical vapor deposition is as follows: the obtained depolymerized material is placed in a CVD furnace, and then the CVD furnace is heated to 800-900℃. Acetylene is introduced at a rate of 0.01-0.05L / min to obtain the coating material.

8. The silicon-oxygen anode material prepared by the preparation method according to any one of claims 1-7.

9. The application of the silicon-oxygen anode material as described in claim 8 in the preparation of lithium battery electrode materials.

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