Low-temperature high-rate graphite negative electrode material and preparation method thereof

Abstract

The application relates to a low-temperature high-rate graphite negative electrode material and a preparation method thereof, and belongs to the technical field of high polymer materials. The low-temperature high-rate graphite negative electrode material comprises, in terms of weight parts, 25-35 parts of graphite, 1-2 parts of molybdenum disulfide, 0.8-1.2 parts of carbon black, 3-5 parts of nano titanium nitride, 3-5 parts of a low-temperature resistant modifier, 1-3 parts of butadiene styrene rubber emulsion, 1-5 parts of deionized water and 15-25 parts of N-methyl pyrrolidone. A compound is obtained by reacting a precursor prepared from lanthanum nitrate hexahydrate, barium nitrate and graphite powder with lithium fluoride, a pre-product is obtained by reacting the hydroxyl group of the compound with a silane hydrolysis product, and finally, the low-temperature resistant modifier is obtained by reacting the amino group of the pre-product with the double bond of a siloxane chain, the internal resistance is reduced, a gradient conductive network is formed, the volume change is buffered, and the rate performance of the negative electrode material is improved. The low-temperature high-rate graphite negative electrode material prepared by the application not only has good low-temperature resistance, but also has excellent high-rate performance and cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a low-temperature high-rate graphite anode material and its preparation method. Background Technology

[0002] Lithium-ion batteries possess characteristics such as high open-circuit potential, high energy density, excellent cycle performance, and no memory effect, demonstrating broad application prospects in various fields such as energy storage systems, transportation, and portable devices. Currently, graphite materials have become the most commonly used anode material for lithium-ion batteries due to their low cost and good cycle stability.

[0003] However, graphite has a low operating potential and is susceptible to polarization, especially at low temperatures. The impedance of the solid electrolyte interface film on its surface increases sharply, and the lithium-ion transport rate decreases significantly, leading to abnormal battery charging and discharging. Simultaneously, the weakening of graphite lattice vibration at low temperatures restricts the movement of lithium ions within the graphite lattice, resulting in a slower ion diffusion rate, a significant decrease in anode performance, and exacerbated polarization. This leads to reduced battery capacity, decreased charging and discharging efficiency, and even battery failure. This not only affects the battery's capacity retention and cycle efficiency but also shortens equipment uptime, impacting user experience. Furthermore, while low-temperature high-rate graphite anode materials possess a certain high rate capability, their inherent high rate capability is insufficient to meet current demands as practical applications become increasingly sophisticated. Therefore, developing superior low-temperature high-rate graphite anode materials has significant practical importance and application value. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a low-temperature, high-rate graphite anode material and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A low-temperature, high-rate graphite anode material and its preparation method, comprising the following raw materials in parts by weight: 25-35 parts graphite, 1-2 parts molybdenum disulfide, 0.8-1.2 parts carbon black, 3-5 parts nano-titanium nitride, 3-5 parts low-temperature modifier, 1-3 parts styrene-butadiene rubber latex, 1-5 parts deionized water, and 15-25 parts N-methylpyrrolidone.

[0007] The low-temperature resistant modifier is prepared by the following method:

[0008] Step A1: Lanthanum nitrate hexahydrate, barium nitrate and 100 mL of deionized water are mixed to prepare a mixed solution. Graphite powder and 50 mL of deionized water are mixed and stirred for 1 hour. The mixture is then slowly added dropwise to the mixed solution. After the addition is complete, stirring is continued for 4 hours. After the reaction is complete, the mixture is sonicated for 60 minutes, centrifuged, washed, dried at 80°C for 12 hours, ground into powder, and sintered at 800°C for 2 hours under argon protection to obtain the precursor.

[0009] Furthermore, the ratio of lanthanum nitrate hexahydrate, barium nitrate, and graphite powder is 0.02-0.06 mol: 0.01-0.03 mol: 0.02-0.06 mol;

[0010] Step A2: Mix lithium fluoride and hydrochloric acid and stir for 30 min, then add the precursor, place in an oil bath at 36 ℃, and stir continuously for 24 h. After the reaction is completed, centrifuge and wash until the pH of the system is neutral, freeze dry, and obtain the compound.

[0011] Furthermore, the ratio of lithium fluoride, hydrochloric acid, and precursor is 0.01-0.03 mol: 40 mL: 0.01-0.03 mol, and the concentration of hydrochloric acid is 9 mol / L;

[0012] Step A3: Mix 3-aminopropyltriethoxysilane and ethanol-water mixed solution evenly, then add the compound and mix evenly. Stir for 6 hours and let stand for 12 hours. Wash the precipitate and freeze dry to obtain the preproduct.

[0013] Furthermore, the ratio of 3-aminopropyltriethoxysilane, ethanol-water mixed solution, and compound is 0.5-1g: 50-150mL: 10-20g, and the volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1.

[0014] Step A4: Mix dodecylbenzenesulfonic acid and deionized water, heat to 45°C, stir until homogeneous, then add decamethylcyclopentasiloxane, γ-methacryloyloxypropyltrimethoxysilane and hexamethyldisiloxane and mix until homogeneous. React for 3 hours to obtain the intermediate.

[0015] Furthermore, the ratio of dodecylbenzenesulfonic acid, deionized water, decamethylcyclopentasiloxane, γ-methacryloyloxypropyltrimethoxysilane, and hexamethyldisiloxane is 0.6-1 mL : 10-20 mL : 0.01-0.03 mol : 0.01-0.03 mol : 0.01-0.03 mol, and the mass fraction of dodecylbenzenesulfonic acid is 10%.

[0016] Step A5: Mix the preproduct, intermediate and triethylamine evenly, stir at 60°C for 10 min, then add azobisisobutyronitrile, continue stirring for 30 min, after the reaction is complete, rotary evaporate, vacuum dry at 50°C for 12 h to obtain the low temperature resistant modifier.

[0017] Furthermore, the ratio of the amount of preproduct, intermediate, triethylamine, and azobisisobutyronitrile is 0.01-0.03 mol: 0.01-0.03 mol: 10-30 mL: 2-18 g.

[0018] A method for preparing a low-temperature, high-rate graphite anode material specifically includes the following steps:

[0019] S1. Graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature modifier, styrene-butadiene rubber latex, deionized water and N-methylpyrrolidone are mixed to prepare an active slurry;

[0020] S2. The active slurry is coated on the surface of the copper foil current collector and dried at 110°C to obtain a low-temperature high-rate graphite anode material.

[0021] The beneficial effects of this invention are:

[0022] The low-temperature high-rate graphite anode material of the present invention has good low-temperature resistance, and at the same time, it also has excellent high-rate performance and cycle stability, further extending its service life.

[0023] The low-temperature resistant modifier prepared in this invention is first prepared by reacting lanthanum nitrate hexahydrate and barium nitrate with graphite powder to obtain a precursor; then, the precursor is reacted with fluoride ions from lithium fluoride to obtain a compound; next, the hydroxyl groups of the compound react with the silanol groups generated by the hydrolysis of 3-aminopropyltriethoxysilane to obtain a preproduct; finally, dodecylbenzenesulfonic acid is ionized in deionized water to release H+. +The ring-opening process of decamethylcyclopentasiloxane forms a growing chain, which is then condensed with hexamethyldisiloxane and hydrolyzed γ-methacryloxypropyltrimethoxysilane to obtain an intermediate. Finally, the low-temperature modifier is prepared by reacting the amino group of the preproduct with the carbon-carbon double bond of the intermediate. The lanthanum-barium composite carbide precursor synthesized by co-precipitation in this low-temperature modifier can introduce a highly conductive phase into the graphite interlayer, forming a three-dimensional conductive framework. Its two-dimensional layered structure provides a fast transport channel for lithium ions and electrons, significantly reducing battery internal resistance and improving charge-discharge efficiency. In addition, the siloxane chains formed after the ring-opening of decamethylcyclopentasiloxane have excellent flexibility, which can buffer the volume change of graphite anode material during low-temperature charge-discharge, reduce electrode cracking, maintain the continuity of the electron or ion transport network, and thus exhibit good cycle stability. Furthermore, the siloxane chains condensed in the intermediate can form chemical bonds with the graphite surface, inhibiting electrolyte decomposition, forming a low-impedance SEI film, accelerating the lithium ion desolvation process, and reducing charge transfer impedance at low temperatures. At the same time, γ-methacryloyloxypropyltrimethoxysilane forms a three-dimensional network structure through cross-linking reaction, enhancing the mechanical strength of the electrode material, preventing capacity decay caused by structural damage at low temperatures, and forming a gradient conductive network with the graphite surface, reducing the lithium ion migration barrier, extending the material's lifespan, and greatly improving the rate performance of the anode material. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1: A method for preparing a low-temperature, high-rate graphite anode material, specifically including the following steps:

[0026] S1. Weigh the raw materials according to the following parts by weight: 25 parts graphite, 1 part molybdenum disulfide, 0.8 parts carbon black, 3 parts nano titanium nitride, 3 parts low-temperature resistant modifier (prepared in this embodiment), 1 part styrene-butadiene rubber latex, 1 part deionized water, and 15 parts N-methylpyrrolidone; mix the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature resistant modifier, styrene-butadiene rubber latex, deionized water, and N-methylpyrrolidone to prepare an active slurry;

[0027] S2. The active slurry is coated on the surface of the copper foil current collector and dried at 110°C to obtain a low-temperature high-rate graphite anode material.

[0028] The low-temperature resistant modifier is prepared by the following method:

[0029] Step A1: Mix 0.02 mol lanthanum nitrate hexahydrate, 0.01 mol barium nitrate and 100 mL deionized water to prepare a mixed solution. Then mix 0.02 mol graphite powder and 50 mL deionized water and stir for 1 h. Slowly add the mixture dropwise to the mixed solution. After the addition is complete, continue stirring for 4 h. After the reaction is complete, sonicate for 60 min, centrifuge, wash, dry at 80 °C for 12 h, grind into powder, and sinter at 800 °C for 2 h under argon protection to obtain the precursor.

[0030] Step A2: Mix 0.01 mol lithium fluoride and 40 mL hydrochloric acid and stir for 30 min. Then add 0.01 mol precursor and place in an oil bath at 36 °C. Stir continuously for 24 h. After the reaction is complete, centrifuge and wash until the pH of the system is neutral. Freeze dry to obtain the compound. The concentration of hydrochloric acid is 9 mol / L.

[0031] Step A3: Mix 0.5g of 3-aminopropyltriethoxysilane and 50mL of ethanol-water mixed solution evenly, then add 10g of compound and mix evenly. Stir for 6h and let stand for 12h. Wash the precipitate and freeze dry to obtain the preproduct. The volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1.

[0032] Step A4: Mix 0.6 mL of dodecylbenzenesulfonic acid and 10 mL of deionized water, heat to 45 °C, stir until homogeneous, then add 0.01 mol of decamethylcyclopentasiloxane, 0.01 mol of γ-methacryloyloxypropyltrimethoxysilane, and 0.01 mol of hexamethyldisiloxane and mix until homogeneous. React for 3 h to obtain the intermediate, with a dodecylbenzenesulfonic acid mass fraction of 10%.

[0033] Step A5: Mix 0.01 mol of preproduct, 0.01 mol of intermediate and 10 mL of triethylamine evenly, stir at 60 °C for 10 min, then add 2 g of azobisisobutyronitrile, continue stirring for 30 min, after the reaction is complete, rotary evaporate, and vacuum dry at 50 °C for 12 h to obtain the low temperature resistant modifier.

[0034] Example 2: A method for preparing a low-temperature, high-rate graphite anode material, specifically including the following steps:

[0035] S1. Weigh the raw materials according to the following parts by weight: 30 parts graphite, 1.5 parts molybdenum disulfide, 1 part carbon black, 4 parts nano titanium nitride, 4 parts low-temperature resistant modifier (prepared in this embodiment), 2 parts styrene-butadiene rubber latex, 3 parts deionized water, and 20 parts N-methylpyrrolidone; mix the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature resistant modifier, styrene-butadiene rubber latex, deionized water, and N-methylpyrrolidone to prepare an active slurry;

[0036] S2. The active slurry is coated on the surface of the copper foil current collector and dried at 110°C to obtain a low-temperature high-rate graphite anode material.

[0037] The low-temperature resistant modifier is prepared by the following method:

[0038] Step A1: Mix 0.04 mol lanthanum nitrate hexahydrate, 0.02 mol barium nitrate and 100 mL deionized water to prepare a mixed solution. Then mix 0.04 mol graphite powder and 50 mL deionized water and stir for 1 h. Slowly add the mixture dropwise to the mixed solution. After the addition is complete, continue stirring for 4 h. After the reaction is complete, sonicate for 60 min, centrifuge, wash, dry at 80 °C for 12 h, grind into powder, and sinter at 800 °C for 2 h under argon protection to obtain the precursor.

[0039] Step A2: Mix 0.02 mol lithium fluoride and 40 mL hydrochloric acid and stir for 30 min. Then add 0.02 mol precursor and place in an oil bath at 36 °C. Stir continuously for 24 h. After the reaction is complete, centrifuge and wash until the pH of the system is neutral. Freeze dry to obtain the compound. The concentration of hydrochloric acid is 9 mol / L.

[0040] Step A3: Mix 0.75g of 3-aminopropyltriethoxysilane and 100mL of ethanol-water mixed solution evenly, then add 15g of compound and mix evenly. Stir for 6h and let stand for 12h. Wash the precipitate and freeze dry to obtain the preproduct. The volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1.

[0041] Step A4: Mix 0.8 mL of dodecylbenzenesulfonic acid and 15 mL of deionized water, heat to 45 °C, stir until homogeneous, then add 0.02 mol of decamethylcyclopentasiloxane, 0.02 mol of γ-methacryloyloxypropyltrimethoxysilane, and 0.02 mol of hexamethyldisiloxane and mix until homogeneous. React for 3 h to obtain the intermediate, with a dodecylbenzenesulfonic acid mass fraction of 10%.

[0042] Step A5: Mix 0.02 mol of preproduct, 0.02 mol of intermediate and 20 mL of triethylamine evenly, stir at 60 °C for 10 min, then add 10 g of azobisisobutyronitrile and continue stirring for 30 min. After the reaction is complete, rotary evaporate and vacuum dry at 50 °C for 12 h to obtain the low-temperature resistant modifier.

[0043] Example 3: A method for preparing a low-temperature, high-rate graphite anode material, specifically including the following steps:

[0044] S1. Weigh the raw materials according to the following parts by weight: 35 parts graphite, 2 parts molybdenum disulfide, 1.2 parts carbon black, 5 parts nano titanium nitride, 5 parts low-temperature resistant modifier (prepared in this embodiment), 3 parts styrene-butadiene rubber latex, 5 parts deionized water, and 25 parts N-methylpyrrolidone; mix the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature resistant modifier, styrene-butadiene rubber latex, deionized water, and N-methylpyrrolidone to prepare an active slurry;

[0045] S2. The active slurry is coated on the surface of the copper foil current collector and dried at 110°C to obtain a low-temperature high-rate graphite anode material.

[0046] The low-temperature resistant modifier is prepared by the following method:

[0047] Step A1: Mix 0.06 mol lanthanum nitrate hexahydrate, 0.03 mol barium nitrate and 100 mL deionized water to prepare a mixed solution. Then mix 0.06 mol graphite powder and 50 mL deionized water and stir for 1 h. Slowly add the mixture dropwise to the mixed solution. After the addition is complete, continue stirring for 4 h. After the reaction is complete, sonicate for 60 min, centrifuge, wash, dry at 80 °C for 12 h, grind into powder, and sinter at 800 °C for 2 h under argon protection to obtain the precursor.

[0048] Step A2: Mix 0.03 mol lithium fluoride and 40 mL hydrochloric acid and stir for 30 min. Then add 0.03 mol precursor and place in an oil bath at 36 °C. Stir continuously for 24 h. After the reaction is complete, centrifuge and wash until the pH of the system is neutral. Freeze dry to obtain the compound. The concentration of hydrochloric acid is 9 mol / L.

[0049] Step A3: Mix 1g of 3-aminopropyltriethoxysilane and 150mL of ethanol-water mixed solution evenly, then add 20g of compound and mix evenly. Stir for 6h and let stand for 12h. Wash the precipitate and freeze dry to obtain the preproduct. The volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1.

[0050] Step A4: Mix 1 mL of dodecylbenzenesulfonic acid and 20 mL of deionized water, heat to 45 °C, stir until homogeneous, then add 0.03 mol of decamethylcyclopentasiloxane, 0.03 mol of γ-methacryloyloxypropyltrimethoxysilane, and 0.03 mol of hexamethyldisiloxane and mix until homogeneous. React for 3 h to obtain the intermediate, with a dodecylbenzenesulfonic acid mass fraction of 10%.

[0051] Step A5: Mix 0.03 mol of preproduct, 0.03 mol of intermediate and 30 mL of triethylamine evenly, stir at 60 °C for 10 min, then add 18 g of azobisisobutyronitrile, continue stirring for 30 min, after the reaction is complete, rotary evaporate, and vacuum dry at 50 °C for 12 h to obtain the low temperature resistant modifier.

[0052] Comparative Example: This comparative example is a low-temperature high-rate graphite anode material. The difference between this example and Example 3 is that an equal amount of fluoroethylene carbonate is used instead of the low-temperature resistant modifier prepared in Example 3. All other aspects are the same.

[0053] Performance Testing: The low-temperature, high-rate graphite anode materials prepared in Examples 1-3 and the comparative example were used as the anode materials for CR2032 button cells. CR2032 button cells were fabricated, and their initial specific capacity was tested using a battery tester at 0.2C and 2C at 25°C. The initial specific capacity was also tested at 2C, -20°C, and 0°C. The system underwent constant current charge-discharge at voltages ranging from 0.01 to 3.0V, and the cycle capacity retention was tested. The test results are shown in Table 1 below.

[0054] Table 1

[0055]

[0056] As can be seen from the test data in Table 1, the low-temperature high-rate graphite anode material prepared by the present invention has good low-temperature resistance. Table 1 also shows that the low-temperature high-rate graphite anode material prepared by the present invention has good high-rate performance and cycle stability, and extends service life.

[0057] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a low-temperature, high-rate graphite anode material, characterized in that, Specifically, the following steps are included: S1. Weigh the raw materials according to the following parts by weight: 25-35 parts graphite, 1-2 parts molybdenum disulfide, 0.8-1.2 parts carbon black, 3-5 parts nano titanium nitride, 3-5 parts low-temperature modifier, 1-3 parts styrene-butadiene rubber latex, 1-5 parts deionized water, and 15-25 parts N-methylpyrrolidone; mix the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature modifier, styrene-butadiene rubber latex, deionized water, and N-methylpyrrolidone to prepare an active slurry; S2. The active slurry is coated on the surface of the copper foil current collector and dried at 110°C to obtain a low-temperature high-rate graphite anode material. The low-temperature resistant modifier is prepared by the following method: Step A1: Lanthanum nitrate hexahydrate, barium nitrate and 100 mL of deionized water are mixed to prepare a mixed solution. Graphite powder and 50 mL of deionized water are mixed and stirred for 1 hour. The mixture is then slowly added dropwise to the mixed solution. After the addition is complete, stirring is continued for 4 hours. After the reaction is complete, the mixture is sonicated for 60 minutes, centrifuged, washed, dried at 80°C for 12 hours, ground into powder, and sintered at 800°C for 2 hours under argon protection to obtain the precursor. Step A2: Mix lithium fluoride and hydrochloric acid and stir for 30 min, then add the precursor, place in an oil bath at 36 ℃, and stir continuously for 24 h. After the reaction is completed, centrifuge and wash until the pH of the system is neutral, freeze dry, and obtain the compound. Step A3: Mix 3-aminopropyltriethoxysilane and ethanol-water mixed solution evenly, then add the compound and mix evenly. Stir for 6 hours and let stand for 12 hours. Wash the precipitate and freeze dry to obtain the preproduct. Step A4: Mix dodecylbenzenesulfonic acid and deionized water, heat to 45°C, stir until homogeneous, then add decamethylcyclopentasiloxane, γ-methacryloyloxypropyltrimethoxysilane and hexamethyldisiloxane and mix until homogeneous. React for 3 hours to obtain the intermediate. Step A5: Mix the preproduct, intermediate and triethylamine evenly, stir at 60°C for 10 min, then add azobisisobutyronitrile, continue stirring for 30 min, after the reaction is complete, rotary evaporate, and vacuum dry at 50°C for 12 h to obtain the low temperature resistant modifier.

2. The method for preparing a low-temperature, high-rate graphite anode material according to claim 1, characterized in that, In step A1, the ratio of lanthanum nitrate hexahydrate, barium nitrate, and graphite powder is 0.02-0.06 mol: 0.01-0.03 mol: 0.02-0.06 mol.

3. The method for preparing a low-temperature, high-rate graphite anode material according to claim 1, characterized in that, In step A2, the ratio of lithium fluoride, hydrochloric acid, and precursor is 0.01-0.03 mol: 40 mL: 0.01-0.03 mol, and the concentration of hydrochloric acid is 9 mol / L.

4. The method for preparing a low-temperature, high-rate graphite anode material according to claim 1, characterized in that, In step A3, the ratio of 3-aminopropyltriethoxysilane, ethanol-water mixed solution, and compound is 0.5-1g: 50-150mL: 10-20g, and the volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:

1.

5. The method for preparing a low-temperature, high-rate graphite anode material according to claim 1, characterized in that, In step A4, the ratio of dodecylbenzenesulfonic acid, deionized water, decamethylcyclopentasiloxane, γ-methacryloyloxypropyltrimethoxysilane, and hexamethyldisiloxane is 0.6-1 mL: 10-20 mL: 0.01-0.03 mol: 0.01-0.03 mol: 0.01-0.03 mol, and the mass fraction of dodecylbenzenesulfonic acid is 10%.

6. The method for preparing a low-temperature, high-rate graphite anode material according to claim 1, characterized in that, In step A5, the ratio of the amount of preproduct, intermediate, triethylamine, and azobisisobutyronitrile is 0.01-0.03 mol: 0.01-0.03 mol: 10-30 mL: 2-18 g.

7. A low-temperature, high-rate graphite anode material, characterized in that, Prepared by the preparation method according to any one of claims 1-6.

Images