CN117199292A - A kind of preparation method of porous silicon carbon negative electrode material - Google Patents

Abstract

The invention relates to the technical field of lithium ion batteries, and provides a preparation method of a porous silicon-carbon anode material for a lithium ion battery, which comprises the following steps: (1) For nanometer Si powder and nanometer Al (OH) ₃ Ultrasonic dispersion is carried out on the mixed water-based suspension liquid of the (B), and the Si/Al (OH) is obtained through freeze drying ₃ Mixing the powder; (2) Adding 4,4' -diaminodiphenyl ether (ODA) and pyromellitic anhydride (PMDA) in dimethylacetamide solution into Si/Al (OH) ₃ Mixing the powder, stirring uniformly, placing in a muffle furnace, completely volatilizing dimethylacetamide and synthesizing Polyimide (PI) to obtain Si/Al (OH) ₃ PI compositeA material; (3) For Si/Al (OH) under inert atmosphere ₃ High temperature carbonization of PI to obtain Si/Al ₂ O ₃ a/C composite; (4) To Si/Al ₂ O ₃ Adding excessive diluted hydrochloric acid into the composite material, and carrying out suction filtration, washing and drying to obtain a porous silicon-carbon anode material; the invention utilizes nano Si powder to carry negative charge and nano Al (OH) ₃ The porous silicon-carbon anode material is prepared by carbonization cladding of PI and hydrochloric acid etching.

Description

A kind of preparation method of porous silicon carbon negative electrode material

Technical field

The present invention relates to the technical field of electrode materials, specifically a method for preparing porous silicon carbon negative electrode materials for lithium ion batteries.

Background technique

Silicon material has a theoretical capacity of up to 4200 mAh/g and a low operating potential, and is considered to be one of the most promising anode materials for next-generation lithium-ion batteries. However, silicon particles undergo significant volume expansion during the lithium intercalation process, causing structural rupture and rapid battery capacity attenuation, thus limiting the practical application of silicon in lithium-ion batteries. The present invention prepares porous silicon carbon materials through a hard template method, which effectively alleviates the volume expansion caused by lithium insertion, ensures the stability of the material structure, and thereby improves the cycle performance of the battery.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the existing defects and provide a preparation method of porous silicon carbon negative electrode material, using nano-Si, nano-Al(OH) ₃ , ODA, and PMDA as raw materials, through ultrasonic dispersion, freeze-drying, Cross-linking and solidification, high-temperature carbonization, hydrochloric acid etching, washing and drying and other processes are used to prepare silicon-carbon negative electrode materials with porous structures, which can effectively solve the problems in the background technology.

In order to achieve the above objects, the present invention provides the following technical solution: a preparation method of porous silicon carbon negative electrode material, including the following steps:

(1) The mixed aqueous suspension of nano-Si powder and nano-Al(OH) ₃ is ultrasonically dispersed and freeze-dried to obtain Si/Al(OH) ₃ mixed powder;

(2) Add the Si/Al(OH) ₃ mixed powder to the dimethylacetamide solution of ODA and PMDA, stir evenly and place it in a muffle furnace. The dimethylacetamide is completely volatilized and PI is synthesized to obtain Si/Al. (OH) ₃ /PI composite materials;

(3) Carry out high-temperature carbonization of Si/Al(OH) ₃ /PI under an inert atmosphere to prepare Si/Al ₂ O ₃ /C composite material;

(4) Add excess dilute hydrochloric acid to the Si/Al ₂ O ₃ /C composite material, and finally undergo suction filtration, washing, and drying to obtain a porous silicon carbon negative electrode material.

The purity of the nano-Si powder is ≥99.9% and the maximum particle size is ≤150 nm; the purity of the nano-Al(OH) ₃ is ≥99.9% and the maximum particle size is ≤200 nm; the mass ratio of the Si and Al(OH) ₃ is 1: 1 to 1:2; the molar ratio of ODA to PMDA is 1:1, and the solution concentration is 15%; the mass ratio of Si/Al(OH) ₃ to ODA/PMDA is 1:1 to 1:2; The temperature of the muffle furnace is 250-280°C, and the heating time is 1-3 hours; the carbonization temperature is 800-1200°C, and the time is 1-2 hours; the inert atmosphere is nitrogen, argon, or helium. of at least one.

Compared with the existing technology, the beneficial effects of the present invention are: the preparation method of the porous silicon carbon negative electrode material has the following benefits:

The silicon carbon anode material prepared by the present invention has a gram capacity greater than 750 mAh/g, a first Coulombic efficiency greater than 90%, and a capacity retention rate greater than 80% after 300 cycles, effectively solving the problem of poor cycle performance of silicon-based anode materials. .

Implementation

The present invention will be further described below through specific examples.

Example 1: Simply mix nano-Si powder (purity ≥ 99.9%, maximum particle size ≤ 150 nm) and nano-Al(OH) ₃ (purity ≥ 99.9%, maximum particle size ≤ 200 nm), Si powder and Al(OH) ₃ The mass ratio is 1:1, add an appropriate amount of water, conduct ultrasonic dispersion, and freeze-dry to obtain Si/Al(OH) ₃ mixed powder; ODA and PMDA are dissolved in dimethylacetamide at a molar ratio of 1:1. Solution with a concentration of 15%, then add Si/Al(OH) ₃ mixed powder. The mass ratio of Si/Al(OH) ₃ to ODA/PMDA is 1:1. Stir evenly and place it in a muffle furnace at 260°C. Keep the temperature for 2 hours, completely volatilize dimethylacetamide and synthesize PI to obtain Si/Al(OH) ₃ /PI composite material; carbonize the composite material at 1000°C for 1 hour in a nitrogen atmosphere to obtain Si/Al ₂ O ₃ /C composite material; add excess dilute hydrochloric acid to the Si/Al ₂ O ₃ /C composite material, and finally undergo suction filtration, washing, and drying to obtain porous silicon carbon negative electrode material.

Example 2: Simply mix nano-Si powder (purity ≥ 99.9%, maximum particle size ≤ 150 nm) and nano-Al(OH) ₃ (purity ≥ 99.9%, maximum particle size ≤ 200 nm), Si powder and Al(OH) ₃ The mass ratio is 1:2, add an appropriate amount of water, conduct ultrasonic dispersion, and freeze-dry to obtain Si/Al(OH) ₃ mixed powder; ODA and PMDA are dissolved in dimethylacetamide at a molar ratio of 1:1. Solution with a concentration of 15%, then add Si/Al(OH) ₃ mixed powder. The mass ratio of Si/Al(OH) ₃ to ODA/PMDA is 1:1. Stir evenly and place it in a muffle furnace at 260°C. Keep the temperature for 2 hours, completely volatilize dimethylacetamide and synthesize PI to obtain Si/Al(OH) ₃ /PI composite material; carbonize the composite material at 1000°C for 1 hour in a nitrogen atmosphere to obtain Si/Al ₂ O ₃ /C composite material; add excess dilute hydrochloric acid to the Si/Al ₂ O ₃ /C composite material, and finally undergo suction filtration, washing, and drying to obtain porous silicon carbon negative electrode material.

Example 3: Simply mix nano-Si powder (purity ≥ 99.9%, maximum particle size ≤ 150 nm) and nano-Al(OH) ₃ (purity ≥ 99.9%, maximum particle size ≤ 200 nm), Si powder and Al(OH) ₃ The mass ratio is 1:1, add an appropriate amount of water, conduct ultrasonic dispersion, and freeze-dry to obtain Si/Al(OH) ₃ mixed powder; ODA and PMDA are dissolved in dimethylacetamide at a molar ratio of 1:1. Solution with a concentration of 15%, then add Si/Al(OH) ₃ mixed powder. The mass ratio of Si/Al(OH) ₃ to ODA/PMDA is 1:2. Stir evenly and place it in a muffle furnace at 260°C. Keep the temperature for 2 hours, completely volatilize dimethylacetamide and synthesize PI to obtain Si/Al(OH) ₃ /PI composite material; carbonize the composite material at 1000°C for 1 hour in a nitrogen atmosphere to obtain Si/Al ₂ O ₃ /C composite material; add excess dilute hydrochloric acid to the Si/Al ₂ O ₃ /C composite material, and finally undergo suction filtration, washing, and drying to obtain porous silicon carbon negative electrode material.

Example 4: Simply mix nano-Si powder (purity ≥ 99.9%, maximum particle size ≤ 150 nm) and nano-Al(OH) ₃ (purity ≥ 99.9%, maximum particle size ≤ 200 nm), Si powder and Al(OH) ₃ The mass ratio is 1:2, add an appropriate amount of water, conduct ultrasonic dispersion, and freeze-dry to obtain Si/Al(OH) ₃ mixed powder; ODA and PMDA are dissolved in dimethylacetamide at a molar ratio of 1:1. Solution with a concentration of 15%, then add Si/Al(OH) ₃ mixed powder. The mass ratio of Si/Al(OH) ₃ to ODA/PMDA is 1:2. Stir evenly and place it in a muffle furnace at 260°C. Keep the temperature for 2 hours, completely volatilize dimethylacetamide and synthesize PI to obtain Si/Al(OH) ₃ /PI composite material; carbonize the composite material at 1000°C for 1 hour in a nitrogen atmosphere to obtain Si/Al ₂ O ₃ /C composite material; add excess dilute hydrochloric acid to the Si/Al ₂ O ₃ /C composite material, and finally undergo suction filtration, washing, and drying to obtain porous silicon carbon negative electrode material.

The silicon carbon negative electrode material prepared in the example is used to prepare button cells, as follows:

Mix the silicon carbon negative electrode material, sodium carboxymethylcellulose and acetylene black in a mass ratio of 80/10/10, add an appropriate amount of deionized water dropwise, grind it into a uniform slurry and apply it to the copper foil. The water was evaporated at room temperature and dried in a vacuum drying oven at 100°C for 12 h to prepare the working electrode. The CR2016 button analog battery is assembled in a glove box filled with high-purity argon (both water and oxygen content are less than 5 ppm). Among them, the counter electrode and reference electrode are metal lithium sheets, the separator is a porous polypropylene film (Celgard2400), and the electrolyte is a mixture of 1 mol/L LiPF ₆ and vinylene carbonate (95:5, volume ratio). The solvent of LiPF ₆ is a mixture of ethylene carbonate and dimethyl carbonate (1:1, volume ratio). A blue power test system (LANDCT2001A, Wuhan Jinnuo Electronics) was used to conduct galvanostatic charge-discharge and cycle performance tests on button batteries. The voltage range was 0.01-2 V vs. Li/Li ⁺ and the current density was 200 mA/g.

The test results of Examples 1-4 are as follows:

Example Gram capacity (mAh/g) First Coulomb efficiency (%) 300-week capacity retention rate (%) 1 1524.5 91.9 81.2 2 1247.9 91.7 82.5 3 1045.7 91.8 83.4 4 775.5 91.1 84.2

The above are only examples of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description of the present invention, or directly or indirectly applied in other related technical fields, shall be regarded as Likewise, it is included in the patent protection scope of the present invention.

Claims (8)

1. A method for preparing porous silicon carbon negative electrode material, which is characterized in that it includes the following steps: (1) The mixed aqueous suspension of nano-Si powder and nano-Al(OH) ₃ is ultrasonically dispersed and freeze-dried to obtain Si/Al(OH) ₃ mixed powder; (2) Add the Si/Al(OH) ₃ mixed powder to the dimethylacetamide solution of 4,4'-diaminodiphenyl ether ODA and pyromellitic anhydride PMDA, stir evenly and place it in the muffle furnace , completely volatilize dimethylacetamide and synthesize polyimide PI to obtain Si/Al(OH) ₃ /PI composite material; (3) Carry out high-temperature carbonization of Si/Al(OH) ₃ /PI under an inert atmosphere to prepare Si/Al ₂ O ₃ /C composite material; (4) Add excess dilute hydrochloric acid to the Si/Al ₂ O ₃ /C composite material, and finally undergo suction filtration, washing, and drying to obtain a porous silicon carbon negative electrode material. 2. The preparation method of a kind of porous silicon carbon negative electrode material according to claim 1, characterized in that: the purity of the nano-Si powder in the step (1) is ≥99.9% and the maximum particle size is ≤150 nm; nano-Al(OH ) _3Purity ≥99.9%, maximum particle size ≤200 nm. 3. The preparation method of a porous silicon carbon negative electrode material according to claim 1, characterized in that: _the mass ratio of Si and Al(OH) in the step (1) is 1:1-1:2 . 4. The preparation method of a porous silicon carbon negative electrode material according to claim 1, characterized in that: in the step (2), the molar ratio of ODA to PMDA is 1:1, and the solution concentration is 15%. 5. The preparation method of a kind of porous silicon carbon negative electrode material according to claim 1, characterized in that: in the step (2), the mass ratio of Si/Al(OH) ₃ to ODA/PMDA is 1:1 to 1:2. 6. The method for preparing porous silicon carbon negative electrode material according to claim 1, characterized in that: in step (2), the temperature of the muffle furnace is 250-280°C, and the heating time is 1-3 hours. 7. The preparation method of a porous silicon carbon negative electrode material according to claim 1: characterized in that in step (3), the carbonization temperature is 800-1200°C and the time is 1-2 hours. 8. The method for preparing a porous silicon carbon negative electrode material according to claim 1, wherein the inert atmosphere in step (3) is at least one of nitrogen, argon, and helium.