Preparation method of fast-charging modified carbon-coated graphite negative electrode material

Abstract

The application relates to a preparation method of a fast-charging modified carbon-coated graphite negative electrode material. The preparation method of the fast-charging modified carbon-coated graphite negative electrode material comprises the following steps: preparing oxidized spherical graphite, coating polyacrylonitrile on the oxidized graphite, coating polyacrylonitrile on the oxidized graphite and compounding tin dioxide, and preparing the carbon-coated graphite negative electrode material, wherein the specific operation steps comprise coating modification, hot spray drying, high-temperature carbonization and the like. The fast-charging modified carbon-coated graphite negative electrode material prepared by the method has the advantages of fast charging capacity, high energy, long cycle life, excellent electrochemical performance, high safety stability and the like, and has a wide application prospect in the fields of lithium ion batteries and the like.

Description

Technical Field

[0001] This invention relates to a method for preparing a fast-charging modified carbon-coated graphite anode material, belonging to the field of lithium-ion batteries. Background Technology

[0002] Graphite consists of stacked hexagonal conjugated carbon nanosheets bonded together by van der Waals forces. Within the same carbon atom plane, the force between two arbitrary carbon atoms (sharing sp2 hybrid bonds) is much stronger than the force between any two carbon planar layers. It is this difference in force that allows lithium to intercalate between the graphite planes; this lithium intercalation process is the mechanism by which graphite stores lithium. When lithium is intercalated in graphite, it occupies the interstitial sites between two graphite layers. Once an lithium ion is inserted, the lithium occupying the interstitial site prevents other lithium from binding to the directly adjacent interstitial site. Thus, lithium ions can only bind to the second carbon atom in each hexagonal graphite layer, limiting the number of lithium atoms to one per six carbon atoms. The lithium intercalation behavior of graphite is directly related to the energy storage density of graphite in lithium-ion batteries; this lithium storage density is commonly referred to as capacity.

[0003] While natural graphite offers numerous advantages as anode materials, it also suffers from drawbacks such as low capacity, poor rate performance, and safety issues due to solvent co-intercalation. Therefore, modifying natural graphite through oxidation, coating, and metal doping can significantly improve its overall electrical performance. Inventing a simple and effective modified graphite material is thus crucial for the development of graphite anode materials. Summary of the Invention

[0004] In order to overcome the above-mentioned technical problems existing in the existing technical field, the purpose of this invention is to provide a method for preparing fast-charging modified carbon-coated graphite anode material.

[0005] This invention provides a method for preparing a fast-charging modified carbon-coated graphite anode material, comprising the following steps:

[0006] Step (1) Preparation of oxidized spherical graphite

[0007] S11. A suitable amount of natural spherical graphite is slowly added to a round-bottom flask containing concentrated sulfuric acid under magnetic stirring.

[0008] S12 is then slowly added to sodium nitrate, cooled in an ice water bath, and stirred rapidly.

[0009] S13 is slowly added to potassium permanganate while controlling the temperature and stirring. After the potassium permanganate is added, the water bath is removed and the reaction is stirred. Deionized water is slowly added to raise the temperature while stirring continuously.

[0010] S14 was washed with H2O2 aqueous solution and filtered, then the filter cake was washed with HCl solution and washed with deionized water until no SO4 was found in the filtrate. 2– (Detected with BaCl2 solution), after centrifugation, the spherical graphite oxide (SGO) was obtained by drying in a drying oven.

[0011] Step (2) Polyacrylonitrile coating of graphite oxide

[0012] S21 Weigh out surface-oxidized spherical graphite (SGO) and place it in a beaker, add a certain amount of deionized water; then add a certain amount of graphite-containing nitrogen-carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder, stir at room temperature under magnetic force, and mix evenly to obtain a mixed suspension coated with LPAN.

[0013] S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a certain temperature to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0014] Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide

[0015] S31 Weigh out surface-oxidized spherical graphite (SGO) and place it in a beaker. Add a certain amount of deionized water and tin dioxide. Then add a certain amount of graphite-containing nitrogen-carbon precursor solution (LPAN) to the suspension of water, tin dioxide and surface-oxidized spherical graphite powder. Stir at room temperature under magnetic force to mix evenly and obtain a mixed suspension coated with LPAN.

[0016] S32 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a certain temperature to obtain the final product, polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2).

[0017] Step (4) Preparation of carbon-coated graphite anode material

[0018] A certain mass ratio of polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) was placed in a beaker. A certain amount of deionized water was added, and after stirring evenly, the mixture was ultrasonically treated. Subsequently, the ultrasonically treated mixture was centrifuged and then spray-dried to obtain carbon-coated graphite anode material.

[0019] Preferably, step (1) the preparation of oxidized spherical graphite includes: S11 adding 2-5g of natural spherical graphite slowly to a round-bottom flask containing 35-50mL of concentrated sulfuric acid under magnetic stirring; S12 adding 1-2.5g of sodium nitrate slowly, cooling to 0-5℃ in an ice-water bath, and stirring rapidly for 1-4h; S13 adding 5-8g of potassium permanganate slowly, controlling the temperature at 14-20℃ and stirring, removing the water bath after the potassium permanganate is added, stirring the reaction for 1-4h, slowly adding 40-55mL of deionized water to raise the temperature to 92-98℃, and stirring continuously for 3-6h; S14 adding 8-14mL of H2O2 aqueous solution to wash and filter, then adding 10-16mL of HCl solution to wash the filter cake, and washing with deionized water until no SO4 is present in the filtrate. 2– (Detection with BaCl2 solution), centrifuged at 2800~3100 rpm, and dried in a drying oven to obtain spherical graphite oxide (SGO).

[0020] In this method, sodium nitrate, concentrated sulfuric acid, potassium permanganate, and other oxidizing agents with high oxidation effects are used in the preparation of oxidized spherical graphite. These agents can effectively oxidize graphite into graphite oxide, improve the oxidation degree of graphite oxide, and have a high preparation efficiency in a short time. Concentrated sulfuric acid plays an acidification role in the reaction, which can adjust the pH value of the reaction system and facilitate the reaction. Potassium permanganate acts as a catalyst in the reaction, which can accelerate the oxidation process of graphite and improve the oxidation efficiency.

[0021] Preferably, step (2) of polyacrylonitrile-coated graphite oxide includes: S21 Weighing 1-2g of surface-oxidized spherical graphite (SGO) and placing it in a beaker, adding 4-10mL of deionized water; then adding 5%-20% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder, stirring at room temperature for 8-12h under magnetic force, and mixing evenly to obtain a mixed suspension coated with LPAN; S22 Using hot spray drying to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder, placing the intermediate powder in a tube furnace and carbonizing it at a high temperature of 900-1200℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0022] The polyacrylonitrile used in this method can form a good interfacial bond with graphite oxide, improving the overall performance of the composite material. Polyacrylonitrile has good wettability and adhesion, which can promote the uniform dispersion of graphite oxide in the composite material and avoid agglomeration. Moreover, polyacrylonitrile-coated graphite oxide as a negative electrode material has excellent electrochemical performance, including high specific capacity, high rate performance and good cycle stability. Because polyacrylonitrile has good thermal stability, the battery negative electrode material can maintain good structural stability and electrochemical performance at high temperatures. In addition, the introduction of polyacrylonitrile can improve the electrical conductivity of the composite material, thereby improving fast charging performance.

[0023] Preferably, step (3) of polyacrylonitrile-coated graphite oxide composite tin dioxide includes: S31 Weighing 1~2g of surface-oxidized spherical graphite (SGO) into a beaker, adding 4~10mL of deionized water and 0.1~0.2g of tin dioxide; then adding 5%~20% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) into the suspension of water, tin dioxide and surface-oxidized spherical graphite powder, stirring at room temperature for 8~12h under magnetic force, and mixing evenly to obtain a mixed suspension coated with LPAN; S32 Using hot spray drying to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder, placing the intermediate powder in a tube furnace for high-temperature carbonization treatment at 900~1200℃ to obtain the final product polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2).

[0024] In this method, tin dioxide is composited with polyacrylonitrile coated with graphite oxide. The excellent electrochemical properties of tin dioxide can be utilized to improve the specific capacity and rate performance of the composite material, thereby enhancing its fast-charging performance. Furthermore, the composite introduction of polyacrylonitrile and tin dioxide can increase the structural strength and toughness of the composite material, improving its impact resistance and bending resistance. By compositely coating graphite oxide and tin dioxide with polyacrylonitrile, a high-specific-capacity negative electrode material can be obtained to meet the requirements of fast charging. The stable interfacial structure and excellent electrochemical properties of polyacrylonitrile and tin dioxide give the composite material good cycle stability.

[0025] Preferably, step (4) of preparing the carbon-coated graphite anode material includes taking polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) in a beaker with a mass ratio of (1~3):1. Add 10~25mL of deionized water, stir evenly, and then sonicate for 1~4h. Subsequently, centrifuge the ultrasonically treated mixture and spray dry to obtain the carbon-coated graphite anode material.

[0026] In this method, a fast-charging modified carbon-coated graphite anode material is prepared by jointly using polyacrylonitrile (PAC) carbon-coated graphite oxide and PAC carbon-coated graphite oxide composite tin dioxide material. This is because PAC carbon-coated graphite oxide and PAC carbon-coated graphite oxide composite tin dioxide have different performance characteristics. PAC carbon-coated graphite oxide exhibits excellent electrochemical performance and good interfacial stability, while PAC carbon-coated graphite oxide composite tin dioxide has higher specific capacity and better fast-charging performance. By using these two materials simultaneously, a composite material with complementary properties can be obtained, improving the overall performance of the fast-charging modified carbon-coated graphite anode material. PAC carbon-coated graphite oxide and PAC carbon-coated graphite oxide composite tin dioxide can form a synergistic effect in the composite material. Their interaction can improve the material's electrical conductivity, mechanical properties, and interfacial stability, further enhancing the overall performance of the fast-charging modified carbon-coated graphite anode material.

[0027] This invention discloses a method for preparing a fast-charging modified carbon-coated graphite anode material. The prepared fast-charging modified carbon-coated graphite anode material has advantages such as fast charging capability, high energy, long cycle life, excellent electrochemical performance, and high safety and stability, and has broad application prospects in the field of lithium-ion batteries. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for preparing a fast-charging modified carbon-coated graphite anode material. Detailed Implementation Example 1

[0029] This invention provides a method for preparing a fast-charging modified carbon-coated graphite anode material, comprising the following steps:

[0030] Step (1) Preparation of oxidized spherical graphite

[0031] S11. 2g of natural spherical graphite was slowly added to a round-bottom flask containing 35mL of concentrated sulfuric acid under magnetic stirring.

[0032] S12 is then slowly added to 1g of sodium nitrate, cooled to 0°C in an ice water bath, and stirred rapidly for 1 hour.

[0033] Slowly add 5g of potassium permanganate to S13, control the temperature at 14℃ and stir. After the potassium permanganate is added, remove the water bath and stir the reaction for 1 hour. Slowly add 40mL of deionized water to raise the temperature to 92℃ and stir continuously for 3 hours.

[0034] S14 was washed with 8 mL of H2O2 aqueous solution and filtered. Then, 10 mL of HCl solution was added to wash the filter cake, and the mixture was washed with deionized water until no SO4 was found in the filtrate. 2–(Detection with BaCl2 solution), centrifuged at 2800 rpm, and then dried in a drying oven to obtain spherical graphite oxide (SGO);

[0035] Step (2) Polyacrylonitrile coating of graphite oxide

[0036] S21 Weigh 1g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 4mL of deionized water. Then add 5% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder. Stir at room temperature for 8 hours under magnetic force to obtain a mixed suspension coated with LPAN.

[0037] S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a high temperature of 900℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0038] Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide

[0039] S31 Weigh 1g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 4mL of deionized water and 0.1g of tin dioxide. Then add 5% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water, tin dioxide and surface-oxidized spherical graphite powder. Stir at room temperature for 8 hours under magnetic force to obtain a mixed suspension coated with LPAN.

[0040] S32 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at 900℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2).

[0041] Step (4) Preparation of carbon-coated graphite anode material

[0042] A mixture of polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) with a mass ratio of 1:1 was placed in a beaker. 10 mL of deionized water was added, and the mixture was stirred until homogeneous. After ultrasonic treatment for 1 h, the ultrasonically treated mixture was centrifuged and then spray-dried to obtain the carbon-coated graphite anode material. Example 2

[0043] Step (1) Preparation of oxidized spherical graphite

[0044] S11. 3g of natural spherical graphite was slowly added to a round-bottom flask containing 40mL of concentrated sulfuric acid under magnetic stirring.

[0045] S12 is then slowly added with 1.5g of sodium nitrate, cooled to 1°C in an ice-water bath, and stirred rapidly for 2 hours.

[0046] Slowly add 6g of potassium permanganate to S13, control the temperature at 16℃ and stir. After the potassium permanganate is added, remove the water bath and stir the reaction for 2 hours. Slowly add 45mL of deionized water to raise the temperature to 94℃ and stir continuously for 4 hours.

[0047] S14 was washed with 10 mL of H2O2 aqueous solution and filtered. The filter cake was then washed with 12 mL of HCl solution and deionized water until no SO4 was found in the filtrate. 2– (Detection with BaCl2 solution), centrifuged at 2900 rpm, and dried in a drying oven to obtain spherical graphite oxide (SGO);

[0048] Step (2) Polyacrylonitrile coating of graphite oxide

[0049] S21 Weigh 1.3g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 6mL of deionized water. Then add 10% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder. Stir at room temperature for 9h under magnetic force to obtain a mixed suspension coated with LPAN.

[0050] S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a high temperature of 1000℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0051] Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide

[0052] S31 Weigh 1.3g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 6mL of deionized water and 0.13g of tin dioxide. Then add 10% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water, tin dioxide and surface-oxidized spherical graphite powder. Stir at room temperature for 9h under magnetic force to obtain a mixed suspension coated with LPAN.

[0053] S32 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at 1000℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2).

[0054] Step (4) Preparation of carbon-coated graphite anode material

[0055] A mixture of polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) with a mass ratio of 1.5:1 was placed in a beaker. 15 mL of deionized water was added, and the mixture was stirred until homogeneous. The mixture was then sonicated for 2 h. Subsequently, the ultrasonically treated mixture was centrifuged and spray-dried to obtain the carbon-coated graphite anode material. Example 3

[0056] Step (1) Preparation of oxidized spherical graphite

[0057] S11. 4g of natural spherical graphite was slowly added to a round-bottom flask containing 45mL of concentrated sulfuric acid under magnetic stirring.

[0058] S12 is then slowly added with 2.0g of sodium nitrate, cooled to 2°C in an ice-water bath, and stirred rapidly for 3 hours.

[0059] Slowly add 7g of potassium permanganate to S13, control the temperature at 18℃ and stir. After the potassium permanganate is added, remove the water bath and stir the reaction for 3 hours. Slowly add 50mL of deionized water to raise the temperature to 96℃ and stir continuously for 5 hours.

[0060] S14 was washed with 12 mL of H2O2 aqueous solution and filtered. The filter cake was then washed with 14 mL of HCl solution and deionized water until no SO4 was found in the filtrate. 2– (Detection with BaCl2 solution), centrifuged at 3000 rpm, and then dried in a drying oven to obtain spherical graphite oxide (SGO);

[0061] Step (2) Polyacrylonitrile coating of graphite oxide

[0062] S21 Weigh 1.6g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 8mL of deionized water. Then add 15% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder. Stir at room temperature for 10h under magnetic force to obtain a mixed suspension coated with LPAN.

[0063] S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a high temperature of 1100℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0064] Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide

[0065] S31 Weigh 1.6g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 8mL of deionized water and 0.16g of tin dioxide. Then add 15% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water, tin dioxide and surface-oxidized spherical graphite powder. Stir at room temperature for 10h under magnetic force to obtain a mixed suspension coated with LPAN.

[0066] S32 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at 1100℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2).

[0067] Step (4) Preparation of carbon-coated graphite anode material

[0068] A mixture of polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) with a mass ratio of 2:1 was placed in a beaker. 20 mL of deionized water was added, and the mixture was stirred evenly and then sonicated for 3 h. Subsequently, the ultrasonically treated mixture was centrifuged and spray-dried to obtain carbon-coated graphite anode material. Example 4

[0069] Step (1) Preparation of oxidized spherical graphite

[0070] S11. 5g of natural spherical graphite was slowly added to a round-bottom flask containing 50mL of concentrated sulfuric acid under magnetic stirring.

[0071] S12 is then slowly added with 2.5g of sodium nitrate, cooled to 4°C in an ice-water bath, and stirred rapidly for 4 hours.

[0072] Slowly add 8g of potassium permanganate to S13, control the temperature at 20℃ and stir. After the potassium permanganate is added, remove the water bath and stir the reaction for 4 hours. Slowly add 55mL of deionized water to raise the temperature to 98℃ and stir continuously for 6 hours.

[0073] S14 was washed with 14 mL of H2O2 aqueous solution and filtered. Then, 16 mL of HCl solution was added to wash the filter cake, and the mixture was washed with deionized water until no SO4 was found in the filtrate. 2– (Detection with BaCl2 solution), centrifuged at 3100 rpm, and dried in a drying oven to obtain spherical graphite oxide (SGO).

[0074] Step (2) Polyacrylonitrile coating of graphite oxide

[0075] S21 Weigh 2.0g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 10mL of deionized water. Then add 20% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder. Stir at room temperature for 12h under magnetic force to obtain a mixed suspension coated with LPAN.

[0076] S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a high temperature of 1200℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0077] Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide

[0078] S31 Weigh 2.0g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 10mL of deionized water and 0.2g of tin dioxide. Then add 20% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water, tin dioxide and surface-oxidized spherical graphite powder. Stir at room temperature for 12h under magnetic force to obtain a mixed suspension coated with LPAN.

[0079] S32 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at 1200℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2).

[0080] Step (4) Preparation of carbon-coated graphite anode material

[0081] A mixture of polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) with a mass ratio of 3:1 was placed in a beaker. 25 mL of deionized water was added, and the mixture was stirred evenly and then sonicated for 4 h. Subsequently, the ultrasonically treated mixture was centrifuged and spray-dried to obtain carbon-coated graphite anode material. Comparative Example 1

[0082] Step (1) Preparation of oxidized spherical graphite

[0083] S11. 2g of natural spherical graphite was slowly added to a round-bottom flask containing 35mL of concentrated sulfuric acid under magnetic stirring.

[0084] S12 is then slowly added to 1g of sodium nitrate, cooled to 0°C in an ice water bath, and stirred rapidly for 1 hour.

[0085] Slowly add 5g of potassium permanganate to S13, control the temperature at 14℃ and stir. After the potassium permanganate is added, remove the water bath and stir the reaction for 1 hour. Slowly add 40mL of deionized water to raise the temperature to 92℃ and stir continuously for 3 hours.

[0086] S14 was washed with 8 mL of H2O2 aqueous solution and filtered. Then, 10 mL of HCl solution was added to wash the filter cake, and the mixture was washed with deionized water until no SO4 was found in the filtrate. 2– (Detection with BaCl2 solution), centrifuged at 2800 rpm, and then dried in a drying oven to obtain spherical graphite oxide (SGO);

[0087] Step (2) Polyacrylonitrile coating of graphite oxide

[0088] S21 Weigh 1g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 4mL of deionized water. Then add 5% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder. Stir at room temperature for 8 hours under magnetic force to obtain a mixed suspension coated with LPAN.

[0089] S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a high temperature of 900℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0090] Step (3) Preparation of carbon-coated graphite anode material

[0091] A mixture of polyacrylonitrile carbonized graphite oxide (CG) and spherical graphite oxide in a mass ratio of 1:1 was placed in a beaker. 10 mL of deionized water was added, and the mixture was stirred until homogeneous. The mixture was then sonicated for 1 hour. Subsequently, the ultrasonically treated mixture was centrifuged and spray-dried to obtain the carbon-coated graphite anode material. Comparative Example 2

[0092] Step (1) Preparation of oxidized spherical graphite

[0093] S11. 5g of natural spherical graphite was slowly added to a round-bottom flask containing 50mL of concentrated sulfuric acid under magnetic stirring.

[0094] S12 is then slowly added with 2.5g of sodium nitrate, cooled to 4°C in an ice-water bath, and stirred rapidly for 4 hours.

[0095] Slowly add 8g of potassium permanganate to S13, control the temperature at 20℃ and stir. After the potassium permanganate is added, remove the water bath and stir the reaction for 4 hours. Slowly add 55mL of deionized water to raise the temperature to 98℃ and stir continuously for 6 hours.

[0096] S14 was washed with 14 mL of H2O2 aqueous solution and filtered. Then, 16 mL of HCl solution was added to wash the filter cake, and the mixture was washed with deionized water until no SO4 was found in the filtrate. 2– (Detection with BaCl2 solution), centrifuged at 3100 rpm, and dried in a drying oven to obtain spherical graphite oxide (SGO).

[0097] Step (2) Polyacrylonitrile coating of graphite oxide

[0098] S21 Weigh 2.0g of surface-oxidized spherical graphite (SGO) and place it in a beaker. Add 10mL of deionized water. Then add 20% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder. Stir at room temperature for 12h under magnetic force to obtain a mixed suspension coated with LPAN.

[0099] S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a high temperature of 1200℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

[0100] Step (4) Preparation of carbon-coated graphite anode material

[0101] A mixture of polyacrylonitrile carbonized graphite oxide (CG) and spherical graphite oxide in a mass ratio of 3:1 was placed in a beaker. 25 mL of deionized water was added, and the mixture was stirred until homogeneous. The mixture was then sonicated for 4 h. Subsequently, the ultrasonically treated mixture was centrifuged and spray-dried to obtain the carbon-coated graphite anode material.

[0102] The negative electrode materials obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were each packaged into button batteries for testing. The specific testing methods are as follows:

[0103] Constant current charge and discharge test

[0104] The button batteries packaged in the examples and comparative examples were tested using a CT2001A Wuhan Landian testing device with a maximum charging voltage of 3V and a minimum discharging voltage of 0.01V to assess their charge and discharge performance.

[0105] Cyclic performance test

[0106] The button batteries packaged in the examples and comparative examples were subjected to 0.1C stable current charge-discharge cycles using a CT2001A Wuhan Landian testing device to test the cycle performance of the batteries.

[0107]

[0108] As shown in Table 1, the first-cycle specific capacity of the fast-charging modified carbon-coated graphite anode materials prepared in Examples 1-4 is higher than that of the fast-charging modified carbon-coated graphite anode materials prepared in Comparative Examples 1 and 2. This is because the two raw materials, polyacrylonitrile-coated graphite oxide and polyacrylonitrile-coated graphite oxide composite tin dioxide, have different performance characteristics. Polyacrylonitrile-coated graphite oxide has excellent electrochemical performance and good interfacial stability, while polyacrylonitrile-coated graphite oxide composite tin dioxide has higher specific capacity and better fast-charging performance. By using these two raw materials simultaneously, a composite material with complementary properties can be obtained, improving the overall performance of the fast-charging modified carbon-coated graphite anode material.

[0109]

[0110] As shown in Table 1, the initial efficiency and 100-cycle capacity retention of the fast-charging modified carbon-coated graphite anode materials prepared in Examples 1-4 are higher than those prepared in Comparative Examples 1 and 2. This is because the fast-charging modified carbon-coated graphite anode materials were prepared by mixing polyacrylonitrile-coated graphite oxide and polyacrylonitrile-coated graphite oxide composite tin dioxide materials in a certain proportion. The polyacrylonitrile-coated graphite oxide and polyacrylonitrile-coated graphite oxide composite tin dioxide materials can form a synergistic effect in the composite material. Their interaction can improve the material's electrical conductivity, mechanical properties, and interfacial stability, resulting in good structural stability during use and high capacity retention after multiple cycles. The combined effect of both further improves the overall performance of the fast-charging modified carbon-coated graphite anode material.

[0111] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for preparing a fast-charging modified carbon-coated graphite anode material, characterized in that... include: Step (1) Preparation of oxidized spherical graphite S11. A suitable amount of natural spherical graphite is slowly added to a round-bottom flask containing concentrated sulfuric acid under magnetic stirring. S12 is then slowly added to sodium nitrate, cooled in an ice water bath, and stirred rapidly. S13 is slowly added to potassium permanganate while controlling the temperature and stirring. After the potassium permanganate is added, the water bath is removed and the reaction is stirred. Deionized water is slowly added to raise the temperature while stirring continuously. S14 was washed with H2O2 aqueous solution and filtered, then the filter cake was washed with HCl solution and washed with deionized water until no SO4 was found in the filtrate. 2– (Detected with BaCl2 solution), after centrifugation, the spherical graphite oxide (SGO) was obtained by drying in a drying oven. Step (2) Polyacrylonitrile coating of graphite oxide S21 Weigh out surface-oxidized spherical graphite (SGO) and place it in a beaker, add a certain amount of deionized water; then add a certain amount of graphite-containing nitrogen-carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder, stir at room temperature under magnetic force, and mix evenly to obtain a mixed suspension coated with LPAN. S22 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a certain temperature to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG). Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide S31 Weigh out surface-oxidized spherical graphite (SGO) and place it in a beaker. Add a certain amount of deionized water and tin dioxide. Then add a certain amount of graphite-containing nitrogen-carbon precursor solution (LPAN) to the suspension of water, tin dioxide and surface-oxidized spherical graphite powder. Stir at room temperature under magnetic force to mix evenly and obtain a mixed suspension coated with LPAN. S32 uses a hot spray drying method to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a certain temperature to obtain the final product, polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2). Step (4) Preparation of carbon-coated graphite anode material A certain mass ratio of polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) was placed in a beaker; a certain amount of deionized water was added, and after stirring evenly, the mixture was ultrasonically treated. Subsequently, the ultrasonically treated mixture was centrifuged and then spray-dried to obtain carbon-coated graphite anode material.

2. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (1) Preparation of oxidized spherical graphite includes S11 adding 2~5g of natural spherical graphite slowly into a round-bottom flask containing 35~50mL of concentrated sulfuric acid under magnetic stirring.

3. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (1) Preparation of oxidized spherical graphite involves slowly adding 1~2.5g of sodium nitrate to S12, cooling to 0~5℃ in an ice-water bath, and stirring rapidly for 1~4h.

4. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (1) Preparation of oxidized spherical graphite involves slowly adding 5-8g of potassium permanganate to S13, controlling the temperature at 14-20℃ and stirring. After the potassium permanganate is added, remove the water bath and stir the reaction for 1-4 hours. Then, slowly add 40-55mL of deionized water to raise the temperature to 92-98℃ and stir continuously for 3-6 hours.

5. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (1) Preparation of oxidized spherical graphite includes adding 8-14 mL of H2O2 aqueous solution to wash and filter, then adding 10-16 mL of HCl solution to wash the filter cake, and washing with deionized water until no SO4 is found in the filtrate. 2– (Detection with BaCl2 solution), centrifuged at 2800~3100 rpm, and dried in a drying oven to obtain spherical graphite oxide (SGO).

6. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (2) Polyacrylonitrile-coated graphite oxide includes S21 Weigh 1~2g of surface-oxidized spherical graphite (SGO) and place it in a beaker, add 4~10mL of deionized water; then add 5%~20% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water and surface-oxidized spherical graphite powder, stir at room temperature for 8~12h under magnetic force, and mix evenly to obtain LPAN-coated mixed suspension.

7. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (2) Polyacrylonitrile-coated graphite oxide includes S22 which is dried by hot spray to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at a high temperature of 900~1200℃ to obtain the final product, polyacrylonitrile carbonized graphite oxide material (CG).

8. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide includes S31 Weigh 1~2g of surface-oxidized spherical graphite (SGO) and place it in a beaker, add 4~10mL of deionized water and 0.1~0.2g of tin dioxide; then add 5%~20% of the graphite mass of nitrogen-containing carbon precursor solution (LPAN) to the suspension of water, tin dioxide and surface-oxidized spherical graphite powder, stir at room temperature for 8~12h under magnetic force, and mix evenly to obtain LPAN-coated mixed suspension.

9. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (3) Polyacrylonitrile-coated graphite oxide composite tin dioxide includes S32 which is dried by hot spray to achieve solid-liquid separation of the mixed suspension to obtain intermediate powder. The intermediate powder is placed in a tube furnace and carbonized at high temperature of 900~1200℃ to obtain the final product polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2).

10. A method for preparing a fast-charging modified carbon-coated graphite anode material according to claim 1, characterized in that: Step (4) Preparation of carbon-coated graphite anode material includes taking polyacrylonitrile carbonized graphite oxide material (CG) and polyacrylonitrile carbonized graphite oxide composite tin dioxide material (CG-SnO2) in a mass ratio of (1~3):1 into a beaker; adding 10~25mL of deionized water, stirring evenly, and then ultrasonically treating for 1~4h. Subsequently, the ultrasonically treated mixture is centrifuged and then spray-dried to obtain carbon-coated graphite anode material.

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