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

Abstract

The invention 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 the following components in parts by weight: 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 styrene butadiene rubber emulsion, 1-5 parts of deionized water and 15-25 parts of N-methyl pyrrolidone. Lanthanum nitrate hexahydrate, barium nitrate and graphite powder are prepared into a precursor, the precursor reacts with lithium fluoride to obtain a compound, hydroxyl of the compound reacts with a silane hydrolysis product to obtain a pre-product, amino of the pre-product reacts with a double bond of a siloxane chain to obtain a low-temperature-resistant modifier, internal resistance is reduced, a gradient conductive network is formed, 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 invention not only has a good low-temperature-resistant effect, but also has excellent high-rate performance and cycling stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a low-temperature high-rate graphite negative electrode material and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries have high open-circuit potential, large energy density, excellent cycle performance and no memory effect, and thus have wide application prospects in energy storage systems, transportation and portable devices. At present, graphite materials are the most commonly used negative electrode materials of lithium ion batteries due to their low price and good cycle stability.

[0003] However, the working potential of graphite is low and is easily affected by polarization. In particular, in a low-temperature environment, the impedance of the solid electrolyte interface film on the surface of graphite increases sharply, and the lithium ion transmission rate decreases significantly, resulting in abnormal charging and discharging of the battery. At the same time, the lattice vibration of graphite at low temperature is weakened, which limits the movement of lithium ions in the graphite lattice, thereby slowing down the ion diffusion rate and significantly reducing the performance of the negative electrode, aggravating polarization, resulting in reduced battery capacity and weakened charging and discharging efficiency, and even failure. This not only affects the capacity retention rate and cycle efficiency of the battery, but also shortens the operation time of the equipment and affects the user experience. In addition, although the low-temperature high-rate graphite negative electrode material itself has a certain high rate, with the increasing demand of practical application, its own high rate has been difficult to meet the current demand. Therefore, it is of great practical significance and application value to develop a low-temperature high-rate graphite negative electrode material with excellent performance. SUMMARY

[0004] To solve the above technical problems, the application provides a low-temperature high-rate graphite negative electrode material and a preparation method thereof.

[0005] The object of the application can be achieved by the following technical solutions. A low-temperature high-rate graphite negative electrode material and a preparation method thereof, comprising the following raw materials by weight: graphite 25-35 parts, molybdenum disulfide 1-2 parts, carbon black 0.8-1.2 parts, nano-titanium nitride 3-5 parts, low-temperature resistant modifier 3-5 parts, butyl rubber emulsion 1-3 parts, deionized water 1-5 parts, and N-methyl pyrrolidone 15-25 parts.

[0006] The low-temperature resistant modifier is prepared by the following method: Step A1: mixing lanthanum nitrate hexahydrate, barium nitrate and 100 mL of deionized water to obtain a mixed solution, mixing graphite powder and 50 mL of deionized water and stirring for 1 h, slowly adding the mixture to the mixed solution, continuing to stir for 4 h after the addition is completed, ultrasonic treatment for 60 min after the reaction is completed, centrifugation, washing, drying at 80 DEG C for 12 h, grinding into powder, and sintering at 800 DEG C for 2 h under the protection of argon to obtain a precursor; Further, the amount 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; Step A2: lithium fluoride and hydrochloric acid were mixed and stirred for 30 min, then the precursor was added, and the mixture was placed in a 36°C oil bath and continuously stirred for 24 h. After the reaction was completed, the system was centrifuged, washed until the pH was neutral, and freeze-dried to obtain the compound; Further, the amount 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. Step A3: 3-aminopropyltriethoxysilane and an ethanol-water mixed solution were uniformly mixed, then the compound was added and uniformly mixed, stirred for 6 h, and then allowed to stand for 12 h. The precipitate was washed and freeze-dried to obtain a pre-product. Further, the amount ratio of 3-aminopropyltriethoxysilane, an ethanol-water mixed solution and the compound is 0.5-1 g: 50-150 mL: 10-20 g, and the volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1. Step A4: dodecylbenzenesulfonic acid and deionized water were mixed, heated to 45°C, and stirred until uniform, then decamethylcyclopentasiloxane, γ-methacryloyloxypropyltrimethoxysilane and hexamethyldisiloxane were added and uniformly mixed, and the mixture was reacted for 3 h to obtain an intermediate. Further, the amount 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%. Step A5: the pre-product, the intermediate and triethylamine were uniformly mixed, stirred at 60°C for 10 min, then azobisisobutyronitrile was added and stirred for another 30 min. After the reaction was completed, the mixture was rotary evaporated and vacuum dried at 50°C for 12 h to obtain a low-temperature resistant modifier. Further, the amount ratio of the pre-product, the intermediate, triethylamine and azobisisobutyronitrile is 0.01-0.03 mol: 0.01-0.03 mol: 10-30 mL: 2-18 g.

[0007] A preparation method of a low-temperature high-rate graphite negative electrode material, specifically comprising the following steps: S1, graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature resistant modifier, butadiene-styrene rubber emulsion, deionized water and N-methyl pyrrolidone were mixed to obtain an active slurry. S2, coating the active slurry on the surface of the copper foil current collector, drying at 110 DEG C, to obtain the low-temperature high-rate graphite negative electrode material.

[0008] The beneficial effects of the present application are: The low-temperature high-rate graphite negative electrode material has good low-temperature resistance, excellent high-rate performance and cycle stability, and further prolongs the service life.

[0009] The low-temperature resistant modifier prepared by the present application is prepared by first reacting lanthanum nitrate hexahydrate, barium nitrate and graphite powder to obtain a precursor, then reacting fluorine ions of lithium fluoride with the precursor to obtain a compound, secondly, reacting the hydroxyl group of the compound with the silicon hydroxyl group generated by the hydrolysis of 3-aminopropyl triethoxysilane to obtain a pre-product, then ionizing H + The low-temperature resistant modifier is prepared by the following steps: first, making decamethylcyclopentasiloxane ring-opening to form a growing chain, then condensing with hexamethyldisiloxane and hydrolyzed γ-methacryloyloxypropyl trimethoxysilane to obtain an intermediate, and finally, reacting the amino group of the pre-product with the carbon-carbon double bond of the intermediate to obtain the low-temperature resistant modifier. The lanthanum-barium composite carbide precursor synthesized by the coprecipitation method in the low-temperature resistant modifier can introduce a highly conductive phase between the graphite layers to form a three-dimensional conductive framework, and its two-dimensional layered structure provides a fast transmission channel for lithium ions and electrons, significantly reducing the internal resistance of the battery and improving the charging and discharging efficiency. In addition, the siloxane chain formed after the ring-opening of decamethylcyclopentasiloxane has excellent flexibility, which can buffer the volume change of the graphite negative electrode material during low-temperature charging and discharging, reduce electrode cracking, and maintain the continuity of the electron or ion transmission network, thereby exhibiting good cycle stability. Furthermore, the siloxane chain condensed by the intermediate can form a chemical bond with the graphite surface, inhibit electrolyte decomposition, form a low-impedance SEI film, accelerate the lithium ion desolvation process, reduce the charge transfer impedance at low temperature, and at the same time, γ-methacryloyloxypropyl trimethoxysilane forms a three-dimensional network structure through crosslinking reaction, enhances the mechanical strength of the electrode material, prevents capacity decay caused by structure destruction at low temperature, and forms a gradient conductive network with the graphite surface, reduces the lithium ion migration energy barrier, and prolongs the service life of the material, greatly improving the rate performance of the negative electrode material. DETAILED DESCRIPTION

[0010] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0011] Embodiment 1: A preparation method of a low-temperature high-rate graphite negative electrode material, specifically comprising the following steps: S1, the raw materials are weighed by parts by weight, 25 parts of graphite, 1 part of molybdenum disulfide, 0.8 parts of carbon black, 3 parts of nano titanium nitride, 3 parts of low-temperature resistant modifier (prepared by this embodiment), 1 part of butadiene rubber emulsion, 1 part of deionized water, 15 parts of N-methyl pyrrolidone; the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature resistant modifier, butadiene rubber emulsion, deionized water and N-methyl pyrrolidone are mixed to prepare an active slurry; S2, the active slurry is coated on the surface of the copper foil current collector, dried at 110°C to prepare a low-temperature high-rate graphite negative electrode material; The low-temperature resistant modifier is prepared by the following method: Step A1: 0.02 mol of lanthanum nitrate hexahydrate, 0.01 mol of barium nitrate and 100 mL of deionized water are mixed to prepare a mixed solution, then 0.02 mol of graphite powder and 50 mL of deionized water are mixed and stirred for 1 h, and then slowly added to the mixed solution, and after the addition is completed, continue to stir for 4 h, after the reaction is completed, ultrasonic treatment for 60 min, centrifugation, washing, drying at 80°C for 12 h, grinding into powder, sintering at 800°C under argon protection for 2 h to prepare a precursor; Step A2: 0.01 mol of lithium fluoride and 40 mL of hydrochloric acid are mixed and stirred for 30 min, then 0.01 mol of the precursor is added, and the system is placed in a 36°C oil bath and continuously stirred for 24 h. After the reaction is completed, centrifugation, washing to neutral pH, freeze-drying to prepare a compound, the concentration of hydrochloric acid is 9 mol / L; Step A3: 0.5 g of 3-aminopropyltriethoxysilane and 50 mL of ethanol-water mixed solution are uniformly mixed, then 10 g of the compound is added and uniformly mixed, stirred for 6 h, then placed for 12 h, the precipitate is washed and freeze-dried to prepare a pre-product, the volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1; Step A4: 0.6 mL of dodecylbenzenesulfonic acid and 10 mL of deionized water are mixed, heated to 45°C, stirred uniformly, then 0.01 mol of decamethylcyclopentasiloxane, 0.01 mol of γ-methacryloyloxypropyltrimethoxysilane and 0.01 mol of hexamethyldisiloxane are added and uniformly mixed, reacted for 3 h to prepare an intermediate, the mass fraction of dodecylbenzenesulfonic acid is 10%; Step A5: 0.01 mol of the pre-product, 0.01 mol of the intermediate and 10 mL of triethylamine are uniformly mixed, stirred at 60°C for 10 min, then 2 g of azobisisobutyronitrile is added and stirred for 30 min, after the reaction is completed, rotary evaporation, vacuum drying at 50°C for 12 h to prepare a low-temperature resistant modifier.

[0012] Example 2: A preparation method of a low-temperature high-rate graphite negative electrode material, specifically comprising the following steps: S1, the raw materials are weighed by parts by weight, 30 parts of graphite, 1.5 parts of molybdenum disulfide, 1 part of carbon black, 4 parts of nano titanium nitride, 4 parts of low-temperature resistant modifier (prepared by this embodiment), 2 parts of butadiene rubber emulsion, 3 parts of deionized water, 20 parts of N-methyl pyrrolidone; the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature resistant modifier, butadiene rubber emulsion, deionized water and N-methyl pyrrolidone are mixed to prepare an active slurry; S2, the active slurry is coated on the surface of the copper foil current collector, dried at 110°C to prepare a low-temperature high-rate graphite negative electrode material; The low-temperature resistant modifier is prepared by the following method: Step A1: 0.04 mol of lanthanum nitrate hexahydrate, 0.02 mol of barium nitrate and 100 mL of deionized water are mixed to prepare a mixed solution, then 0.04 mol of graphite powder and 50 mL of deionized water are mixed and stirred for 1 h, and then slowly added to the mixed solution, and after the addition is completed, continue to stir for 4 h, after the reaction is completed, ultrasonic treatment for 60 min, centrifugation, washing, drying at 80°C for 12 h, grinding into powder, sintering at 800°C for 2 h under argon protection to prepare a precursor; Step A2: 0.02 mol of lithium fluoride and 40 mL of hydrochloric acid are mixed and stirred for 30 min, then 0.02 mol of the precursor is added, and the mixture is placed in a 36°C oil bath and continuously stirred for 24 h. After the reaction is completed, centrifugation, washing until the system pH is neutral, freeze-drying to prepare a compound, the concentration of hydrochloric acid is 9 mol / L; Step A3: 0.75 g of 3-aminopropyltriethoxysilane and 100 mL of ethanol-water mixed solution are mixed uniformly, then 15 g of the compound is added and mixed uniformly, stirred for 6 h, then stand for 12 h, the precipitate is washed and freeze-dried to prepare a pre-product, the volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1; Step A4: 0.8 mL of dodecylbenzenesulfonic acid and 15 mL of deionized water are mixed, heated to 45°C, stirred uniformly, then 0.02 mol of decamethylcyclopentasiloxane, 0.02 mol of γ-methacryloyloxypropyltrimethoxysilane and 0.02 mol of hexamethyldisiloxane are added and mixed uniformly, reacted for 3 h to prepare an intermediate, the mass fraction of dodecylbenzenesulfonic acid is 10%; Step A5: 0.02 mol of the pre-product, 0.02 mol of the intermediate and 20 mL of triethylamine are mixed uniformly, then 10 g of azobisisobutyronitrile is added after stirring at 60°C for 10 min, and the mixture is continuously stirred for 30 min. After the reaction is completed, rotary evaporation, vacuum drying at 50°C for 12 h to prepare a low-temperature resistant modifier.

[0013] Example 3: A preparation method of a low-temperature high-rate graphite negative electrode material, specifically comprising the following steps: S1, the raw materials are weighed by parts by weight, 35 parts of graphite, 2 parts of molybdenum disulfide, 1.2 parts of carbon black, 5 parts of nano titanium nitride, 5 parts of low-temperature resistant modifier (prepared by this embodiment), 3 parts of butadiene rubber emulsion, 5 parts of deionized water, 25 parts of N-methyl pyrrolidone; the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low-temperature resistant modifier, butadiene rubber emulsion, deionized water and N-methyl pyrrolidone are mixed to prepare an active slurry; S2, the active slurry is coated on the surface of the copper foil current collector, dried at 110°C to prepare a low-temperature high-rate graphite negative electrode material; The low-temperature resistant modifier is prepared by the following method: Step A1: 0.06 mol of lanthanum nitrate hexahydrate, 0.03 mol of barium nitrate and 100 mL of deionized water are mixed to prepare a mixed solution, then 0.06 mol of graphite powder and 50 mL of deionized water are mixed and stirred for 1 h, and then slowly added to the mixed solution, after the addition is completed, continue to stir for 4 h, after the reaction is completed, ultrasonic treatment for 60 min, centrifugation, washing, drying at 80°C for 12 h, grinding into powder, sintering at 800°C for 2 h under argon protection to prepare a precursor; Step A2: 0.03 mol of lithium fluoride and 40 mL of hydrochloric acid are mixed and stirred for 30 min, then 0.03 mol of the precursor is added, and the mixture is placed in a 36°C oil bath and continuously stirred for 24 h. After the reaction is completed, centrifugation, washing until the system pH is neutral, freeze-drying to prepare a compound, the concentration of hydrochloric acid is 9 mol / L; Step A3: 1 g of 3-aminopropyltriethoxysilane and 150 mL of ethanol-water mixed solution are mixed uniformly, then 20 g of the compound is added and mixed uniformly, stirred for 6 h, then stand for 12 h, the precipitate is washed and freeze-dried to prepare a pre-product, the volume ratio of ethanol to deionized water in the ethanol-water mixed solution is 4:1; Step A4: 1 mL of dodecylbenzenesulfonic acid and 20 mL of deionized water are mixed, heated to 45°C, stirred uniformly, then 0.03 mol of decamethylcyclopentasiloxane, 0.03 mol of γ-methacryloyloxypropyltrimethoxysilane and 0.03 mol of hexamethyldisiloxane are added and mixed uniformly, reacted for 3 h to prepare an intermediate, the mass fraction of dodecylbenzenesulfonic acid is 10%; Step A5: 0.03 mol of the pre-product, 0.03 mol of the intermediate and 30 mL of triethylamine are mixed uniformly, then 18 g of azobisisobutyronitrile is added after stirring at 60°C for 10 min, continue to stir for 30 min, after the reaction is completed, rotary evaporation, vacuum drying at 50°C for 12 h to prepare a low-temperature resistant modifier.

[0014] Comparative Example: This comparative example is a low-temperature high-rate graphite negative electrode material, which is different from Example 3 in that an equal amount of fluoroethylene carbonate is used instead of the low-temperature resistant modifier prepared in Example 3, and the rest is the same.

[0015] Performance test: the low-temperature high-rate graphite negative electrode material prepared by examples 1-3 and comparative examples was used as the negative electrode material of CR2032 button cell, the CR2032 button cell was prepared, and the first specific capacity was tested at 0.2C and 2C, 25℃ by battery tester, and the first specific capacity at 2C, -20℃ and 0℃ was tested; the system carried out constant current charging and discharging, the voltage was 0.01-3.0V, and the cycle capacity retention rate was tested; the test results are shown in Table 1: Table 1

[0016] From the data tested in Table 1, it can be seen that the low-temperature high-rate graphite negative electrode material prepared by the application has good low-temperature resistance effect, and from Table 1, it can be seen that the low-temperature high-rate graphite negative electrode material prepared by the application has good high-rate performance and cycle stability, and prolongs the service life.

[0017] The above content is only an example and description of the concept of the application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as the modifications or supplements do not deviate from the concept of the application or exceed the scope defined by the claims, and they should belong to the protection scope of the application.

Claims

1. A method for preparing a low-temperature high-rate graphite negative electrode material, characterized in that, Specifically comprising the following steps: S1, the raw materials are weighed by weight parts, graphite 25-35 parts, molybdenum disulfide 1-2 parts, carbon black 0.8-1.2 parts, nano titanium nitride 3-5 parts, low temperature resistant modifier 3-5 parts, butyl rubber emulsion 1-3 parts, deionized water 1-5 parts, N-methyl pyrrolidone 15-25 parts; the graphite, molybdenum disulfide, carbon black, nano titanium nitride, low temperature resistant modifier, butyl rubber emulsion, deionized water and N-methyl pyrrolidone are mixed to prepare an active slurry; S2, the active slurry is coated on the surface of copper foil current collector, dried at 110℃ to prepare a low temperature high rate graphite negative electrode material; The low temperature resistant modifier is prepared by the following method: Step A1: mix lanthanum nitrate hexahydrate, barium nitrate and 100 mL deionized water to prepare a mixed solution, then mix graphite powder and 50 mL deionized water and stir for 1 h, slowly drop into the mixed solution, continue to stir for 4 h after dropping, after reaction, ultrasonic treatment for 60 min, centrifugal, washing, drying at 80℃ for 12 h, grinding into powder, sintering at 800℃ for 2 h under argon protection to prepare a precursor; Step A2: mix lithium fluoride and hydrochloric acid and stir for 30 min, then add the precursor, place in a 36℃ oil bath, continue to stir for 24 h, after reaction, centrifugal, washing until the system is neutral, freeze drying to prepare a compound; Step A3: mix 3-aminopropyl triethoxysilane and ethanol-water mixed solution uniformly, then add the compound and mix uniformly, stir for 6 h, then stand for 12 h, wash the precipitate and freeze dry to prepare a pre-product; Step A4: mix dodecylbenzenesulfonic acid and deionized water, stir uniformly until the temperature reaches 45℃, then add decamethylcyclopentasiloxane, γ-methacryloyloxypropyltrimethoxysilane and hexamethyldisiloxane and mix uniformly, react for 3 h to prepare an intermediate; Step A5: mix the pre-product, intermediate and triethylamine uniformly, stir at 60℃ for 10 min, then add azobisisobutyronitrile, continue to stir for 30 min, after reaction, rotary evaporation, vacuum drying at 50℃ for 12 h to prepare a low temperature resistant modifier.

2. The method for preparing a low-temperature, high-rate graphite negative electrode material according to claim 1, wherein: The amount ratio of lanthanum nitrate hexahydrate, barium nitrate and graphite powder in step A1 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 negative electrode material according to claim 1, wherein: The amount ratio of lithium fluoride, hydrochloric acid and precursor in step A2 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 negative electrode material according to claim 1, wherein: The amount ratio of 3-aminopropyl triethoxysilane, ethanol-water mixed solution and compound in step A3 is 0.5-1 g:50-150 mL:10-20 g, and the volume ratio of ethanol and deionized water in the ethanol-water mixed solution is 4:

1.

5. The method for preparing a low-temperature, high-rate graphite negative electrode material according to claim 1, wherein: The amount ratio of dodecyl benzene sulfonic acid, deionized water, decamethylcyclopentasiloxane, gamma-methacryloyloxypropyl trimethoxysilane, hexamethyldisiloxane in step A4 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 dodecyl benzene sulfonic acid is 10%.

6. The method for preparing a low-temperature, high-rate graphite negative electrode material according to claim 1, wherein: The amount ratio of pre-product, intermediate, triethylamine, azobisisobutyronitrile in step A5 is 0.01-0.03 mol:0.01-0.03 mol:10-30 mL:2-18 g.

7. A low-temperature high-capacity graphite negative electrode material, characterized by, Prepared by the preparation method according to any one of claims 1-6.

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