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CN-121983530-A - Silicon-carbon composite anode material based on multi-step calcination construction of finite field structure and preparation method thereof

CN121983530ACN 121983530 ACN121983530 ACN 121983530ACN-121983530-A

Abstract

The invention discloses a silicon-carbon composite anode material based on a multi-step calcination construction limit structure and a preparation method thereof, and belongs to the technical field of lithium ion batteries. The core of the invention is to combine a carbon source with structural building capability with a multi-step calcination process. The method comprises the steps of mixing nano silicon with specific carbon sources (such as asphalt, phenolic resin, lignin and the like) to prepare a precursor, carrying out three-step heat treatment on the precursor under an inert atmosphere, firstly carrying out structural curing at 200-350 ℃ to crosslink the carbon sources to form a stable framework, then carrying out preliminary carbonization at 400-550 ℃ to form an amorphous carbon matrix with buffer capacity, and finally carrying out interface strengthening at 600-950 ℃ to promote the combination between carbon and silicon particles and enhance the graphitization degree and the electric conductivity of the carbon layer. According to the invention, through the synergistic regulation and control of the carbon structure and the calcination process, a plurality of carbon-based domain-limited structures with firm interfaces and strong external hardness and internal toughness are constructed in situ outside the silicon particles, and the volume expansion of silicon can be effectively inhibited, so that the silicon-carbon composite anode material with high capacity and excellent cycle stability is prepared.

Inventors

  • YAO YAOCHUN
  • XU BAOQIANG
  • Wang Yaoce
  • ZHANG KEYU
  • ZHOU XIANGYANG
  • WANG PENG
  • YANG JUAN
  • ZHANG YAGUANG
  • HU JIANJUN
  • YANG BIN

Assignees

  • 昆明理工大学
  • 大理宸宇储能新材料有限公司
  • 中南大学

Dates

Publication Date
20260505
Application Date
20251201

Claims (8)

  1. 1. The preparation method of the silicon-carbon composite anode material based on the multi-step calcination construction of the limit structure is characterized by comprising the following specific steps: (1) Mixing a nano silicon material with a first carbon source in a water-based solvent, dispersing by mechanical stirring and ultrasonic to form a uniform suspension, and then carrying out centrifugal separation and drying to obtain a Si-C blend; (2) Adding a second carbon source into the blend obtained in the step (1), placing the blend in a planetary ball mill for dry ball milling, and carrying out mechanical dry mixing for 2-10h at a rotating speed of 300-400 r/min to obtain a Si-C composite precursor; (3) Heating the Si-C composite precursor obtained in the step (2) to 200-350 ℃ at a rate of 1-8 ℃ per minute under inert atmosphere, and preserving heat for 1-5h to perform structural curing treatment; (4) After the step (3) is finished, continuously heating to 400-550 ℃ at a rate of 3-14 ℃ per minute under inert atmosphere, and preserving heat for 2-9 hours to finish primary carbonization treatment; (5) After the step (4) is completed, continuously heating to 600-950 ℃ at a rate of 5-13 ℃ per minute under inert atmosphere, preserving heat for 2-8 hours, performing interface strengthening and partial graphitization treatment, and then naturally cooling to room temperature to obtain the final Si-C composite anode material.
  2. 2. The preparation method of the silicon-carbon composite anode material based on the multi-step calcination construction domain-limited structure is characterized in that in the step (1), the nano silicon material is one or more of nano silicon particles, nano silicon spheres, porous nano silicon, silicon nanowires and silicon nanotubes, meanwhile, the particle size range of the nano silicon is 10-800 nm, the water-based solvent is deionized water, ethanol or a mixed solution of the deionized water and the ethanol, and the mass ratio of the nano silicon to the water-based solvent is 1:100-1:800.
  3. 3. The preparation method of the silicon-carbon composite anode material based on the multi-step calcination construction limit structure, which is disclosed in claim 1, is characterized in that in the step (1), the first carbon source is one or more of ordered mesoporous carbon, biomass porous carbon, resin-based carbon and graphitized porous carbon, and the mass ratio of nano silicon to the first carbon source is 1:1-5:1.
  4. 4. The preparation method of the silicon-carbon composite anode material based on the multi-step calcination construction limit structure, which is characterized in that the second carbon source in the step (2) is one or more of glucose, sucrose, petroleum asphalt, coal asphalt and phenolic resin, and the mass ratio of the addition amount of the second carbon source to the obtained Si-C blend is 1:2-1:10.
  5. 5. The preparation method of the silicon-carbon composite anode material based on the multi-step calcination construction limit structure, which is disclosed in claim 1, is characterized in that the process of the structure curing treatment in the step (3) is that the temperature rising rate is 3-6 ℃ per minute, the sintering temperature is 250-300 ℃, and the heat preservation time is 4-8 hours.
  6. 6. The preparation method of the silicon-carbon composite anode material based on the multi-step calcination construction limit structure, which is disclosed in claim 1, is characterized in that the technological parameters of the primary carbonization treatment in the step (4) are that the temperature is raised to 450-500 ℃ at 5-10 ℃ per minute, and the temperature is kept for 3-6 hours.
  7. 7. The preparation method of the silicon-carbon composite anode material based on the multi-step calcination construction limit structure, which is disclosed in claim 1, is characterized in that the technological parameters of interface strengthening and graphitization treatment in the step (5) are that the temperature is raised to 750-850 ℃ at 6-9 ℃ per minute, and the temperature is kept for 4-7h.
  8. 8. A silicon-carbon composite anode material prepared by the preparation method of any one of claims 1 to 7.

Description

Silicon-carbon composite anode material based on multi-step calcination construction of finite field structure and preparation method thereof Technical Field The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a silicon-carbon composite anode material based on a multi-step calcination construction limit structure and a preparation method thereof. Background Silicon is considered to be an ideal negative electrode material for next generation high energy density lithium ion batteries because of its theoretical specific capacity up to 4200 mAh/g (about ten times that of conventional graphite negative electrodes). However, silicon has a volume expansion exceeding 300% during charge and discharge, which is liable to cause pulverization of an electrode structure, failure of electrical contact between an active material and a current collector, and repeated rupture and regeneration of a Solid Electrolyte Interface (SEI) film. These problems together cause rapid capacity decay and shortened cycle life, severely restricting the practical application of silicon cathodes. To address the above challenges, the "nanocrystallization+carbon cladding" strategy has been studied to relieve the stress caused by volume change by nanocrystallizing the silicon material and compounding with the carbon material, constructing a conductive network with good conductivity and mechanical toughness and buffering expansion. At present, the common method mostly adopts a single carbon source (such as glucose, asphalt or polymer) and nano silicon to be mixed and then subjected to one-step high-temperature treatment to realize coating. However, it is difficult to satisfy the multiple performance requirements of a single carbon source, such as good buffering but poor compactness of porous carbon formed after carbonization of glucose, and an asphalt-derived carbon layer having excellent conductivity but insufficient toughness is liable to crack when silicon swells. In addition, the formation process of the carbon layer is difficult to accurately regulate and control by one-step high-temperature sintering, and the step-by-step construction of the carbon structure and the in-situ strengthening of a silicon-carbon interface cannot be realized, so that the coating layer is not ideal in structure and weak in binding force, and the improvement of the comprehensive performance of the material is limited. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a silicon-carbon composite anode material based on a multi-step calcination construction limit structure and a preparation method thereof. According to the method, secondary compounding is carried out by introducing carbon sources with different functions step by step, and a three-step calcination process is combined, so that a composite carbon shell layer which is sufficient in internal buffer space, compact in external packaging and firm in combination with a silicon core interface is constructed outside nano silicon, and therefore high specific capacity, high first coulomb efficiency and ultra-long cycle life are synchronously realized. The preparation method comprises the following specific preparation steps: (1) The preparation of the blend comprises the steps of weighing a nano silicon material and a first carbon source according to a mass ratio of 1:1-5:1, dispersing the nano silicon material and the first carbon source in a water-based solvent (the mass ratio of the nano silicon powder to the water-based solvent is 1:100-1:800), and fully and uniformly mixing the nano silicon material and the first carbon source through mechanical stirring and ultrasonic treatment. Then, centrifugally separating the mixed system (the rotating speed is 5000-12000 r/min, the time is 2-10 min), discarding the supernatant, and drying the obtained precipitate at 80-120 ℃ for 6-12h to obtain the blend of the nano silicon and the first carbon source; (2) Adding a second carbon source into the blend obtained in the step (1), placing the blend in a planetary ball mill, performing dry ball milling, performing mechanical dry mixing for 2-10 hours at a rotating speed of 300-400 r/min to obtain a Si-C composite precursor, wherein the mass ratio of the addition of the second carbon source to the blend is 1:2-1:10, and uniformly distributing the second carbon source in the blend by stirring; (3) The core-shell precursor obtained in the step (2) is placed in a tube furnace or an atmosphere sintering furnace, and is heated to 200-350 ℃ at a rate of 1-8 ℃ per minute under inert protective atmosphere (such as argon and nitrogen), and is kept for 1-5h; (4) Primary carbonization treatment, namely continuously heating to 400-550 ℃ at a rate of 3-14 ℃ per minute under inert atmosphere after the step (3) is completed, and preserving heat for 2-9 hours; (5) And (3) interface strengthening and graphitizing treatment, namely continuously hea