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CN-122025610-A - Nano silicon/mesoporous carbon silicon carbon composite anode material based on CVD, preparation method and lithium ion battery

CN122025610ACN 122025610 ACN122025610 ACN 122025610ACN-122025610-A

Abstract

The invention discloses a nano silicon/mesoporous carbon silicon carbon composite anode material based on CVD, a preparation method and a lithium ion battery, and belongs to the technical field of lithium ion battery anode materials. The porous carbon comprises mesoporous carbon serving as a skeleton substrate, wherein a silicon carbide interface layer is coated on the surface of the mesoporous carbon, and sub-nano silicon particles are deposited in situ in pore channels of the mesoporous carbon. Meanwhile, the method for preparing the anode material is provided, wherein the silicon carbide interface layer is deposited on the surface of the mesoporous carbon, the technological parameters of the mixture ratio of the mixed gas, the reaction temperature, the deposition pressure and the reaction time are regulated and controlled, the thickness of the silicon carbide interface layer is controlled, and the silicon carbide interface layer is ensured to be uniformly distributed on the surface of the mesoporous carbon. Meanwhile, the production inhibitor is introduced to limit the grain size of the growth of the silicon crystal nucleus, so that the electrochemical stability of the material can be improved, and the mechanical strength of the material in long-time use can be enhanced. The prepared composite anode material can be used for preparing a lithium ion battery, so that the cycle stability, the rapid charge and discharge performance and the overall energy density of the battery can be remarkably improved.

Inventors

  • XU JUN
  • SONG HUCHENG
  • YU ZHONGWEI
  • ZHANG ZEHUI

Assignees

  • 南通大学

Dates

Publication Date
20260512
Application Date
20260331

Claims (10)

  1. 1. The preparation method of the mesoporous carbon/silicon carbide double-matrix silicon-carbon composite anode material based on CVD is characterized by comprising the following specific steps of: s1, carrying out pretreatment and activation treatment on mesoporous carbon to obtain preposed mesoporous carbon; s2, placing the front mesoporous carbon into a CVD reactor, introducing a silicon carbide precursor gas, and depositing a silicon carbide interface layer on the surface of the front mesoporous carbon to obtain middle mesoporous carbon; s3, switching silicon carbide precursor gas into silicon source gas, wherein the silicon source gas contains production inhibitor, limiting the growth of silicon crystal nucleus to a particle size of not more than 8nm through the production inhibitor, and depositing sub-nano silicon particles in situ in a pore canal of the mesoporous carbon to obtain the composite anode material.
  2. 2. The method for preparing a CVD-based mesoporous carbon/silicon carbide dual-matrix silicon-carbon composite anode material according to claim 1, wherein the production inhibitor introduced into the silicon source gas in step S3 consists of SiH 4 and C 2 H 4 , and the volume ratio of SiH 4 to C 2 H 4 is (0.5-2): 1.
  3. 3. The preparation method of the CVD-based mesoporous carbon/silicon carbide double-matrix silicon-carbon composite anode material is characterized by further comprising the step S4 of carbon coating sub-nano silicon particles, specifically, introducing a mixed gas of acetylene and argon into a reaction furnace, and carrying out heating treatment at 550-700 ℃ for 0.5-2 hours to obtain the sub-nano silicon particles with a carbon coating layer, wherein the volume ratio of the acetylene to the argon in the mixed gas is 1 (3-5).
  4. 4. The method for preparing a CVD-based mesoporous carbon/silicon carbide dual-matrix silicon carbon composite anode material according to claim 2, wherein the silicon carbide precursor gas in step S2 is composed of SiCl 4 、C 2 H 4 and argon gas, and the volume ratio thereof is (0.8-1.2): 1.2-2.0): 7.0-8.0; The deposition temperature is controlled at 500-600 ℃, the deposition pressure is 50-100 Pa, and the deposition time is 1-3 hours.
  5. 5. The method for preparing a CVD-based mesoporous carbon/silicon carbide dual-matrix silicon-carbon composite anode material according to claim 2, wherein the silicon source gas in step S3 is composed of SiH 4 、C 2 H 4 and H 2 and the volume ratio thereof is (0.8-1.2): (0.8-1.2): (2.5-3.5); The deposition temperature is 700-800 ℃, the deposition pressure is 150-200Pa, and the deposition time is 2-5 hours.
  6. 6. The method for preparing the CVD-based mesoporous carbon/silicon carbide dual matrix silicon carbon composite anode material according to claim 5, wherein the specific step of pretreating the mesoporous carbon in the step S1 is to soak the mesoporous carbon in a 5-10% HNO 3 solution for 4-6 hours.
  7. 7. The CVD-based mesoporous carbon/silicon carbide dual-matrix silicon carbon composite anode material according to any one of claims 1 to 6, wherein the composite anode material comprises mesoporous carbon and a silicon carbide interface layer coated on the surface of the mesoporous carbon, sub-nano silicon particles are deposited in pore channels of the mesoporous carbon, the sub-nano silicon particles are uniformly distributed in the pore channels of the mesoporous carbon and have a particle size of not more than 8nm, and meanwhile, the sub-nano silicon particles and the silicon carbide interface layer form a multi-stage buffer structure together.
  8. 8. The CVD-based mesoporous carbon/silicon carbide dual matrix silicon carbon composite anode material according to claim 7, wherein the surface of the sub-nano silicon particles is coated with a carbon coating layer, and the thickness of the carbon coating layer is 1-5nm.
  9. 9. The CVD-based mesoporous carbon/silicon carbide dual matrix silicon carbon composite anode material according to claim 6 or 7, wherein the thickness of the silicon carbide interface layer is 2-10nm, and a stable covalent bond is formed between the silicon carbide interface layer and the mesoporous carbon.
  10. 10. A lithium ion battery comprising the composite anode material of any one of claims 1-6 or 7-9.

Description

Nano silicon/mesoporous carbon silicon carbon composite anode material based on CVD, preparation method and lithium ion battery Technical Field The invention relates to a composite negative electrode material and a preparation method thereof, in particular to a nano silicon/mesoporous carbon silicon carbon composite negative electrode material based on CVD, a preparation method thereof and a lithium ion battery, and belongs to the technical field of lithium ion battery negative electrode materials. Background With the rapid development of global energy transformation and new energy automobile industry, battery technology, especially in terms of improving battery safety and energy density, is an important direction of global technological innovation. Silicon-based materials are considered as ideal choices for negative electrode materials of next-generation high-energy-density lithium ion batteries due to their theoretical specific capacity of up to 4200 mAh/g, abundant resource reserves and lower lithium intercalation potential. However, the severe volume expansion of silicon occurring during lithium intercalation/deintercalation causes pulverization of an electrode structure, separation of an active material from a current collector, and continuous consumption of electrolyte and active lithium by repeatedly ruptured Solid Electrolyte Interface (SEI) films, severely limiting the cycle life thereof. In order to cope with the challenges, the silicon negative electrode technology is subjected to three generations of iteration, namely, nano silicon and graphite are mixed by mechanical ball milling in the early stage, the volume expansion is partially relieved, silicon particles are easy to agglomerate, a conductive network is incomplete, the capacity retention rate is less than 60% after 100 times of 0.1C circulation, and the later developed carbon-coated nano silicon technology promotes electron conduction and buffer expansion through a surface carbon layer, but the uniformity of carbon coating is poor, and dynamic cracking of an SEI film is difficult to inhibit. In recent years, the third generation of in-situ deposition of silicon in mesoporous carbon channels has become the mainstream of CVD technology, which utilizes mesoporous confinement effect to control silicon particle size, and cycle performance is significantly improved, but still faces the bottlenecks of uneven silicon particle size distribution, poor batch stability and insufficient high-rate performance. Ethylene-assisted CVD technology is proposed by Korean university, and silicon nucleus growth is inhibited through Si-C bond, so that a sub-nano silicon and carbon/silicon carbide double-matrix composite material is successfully prepared, and the coulombic efficiency reaches 99.96% after 50 times of circulation, but the process needs to accurately control the ethylene proportion, and the silicon carbide interface layer deposition condition is harsh, so that the industrialization cost is high. In view of the above, in order to overcome the technical problems, the invention designs a mesoporous carbon/silicon carbide double-matrix silicon carbon composite anode material based on CVD, and a preparation method and application thereof. Disclosure of Invention The invention provides a mesoporous carbon/silicon carbide double-matrix silicon-carbon composite anode material based on CVD, a preparation method and a lithium ion battery, and the technical aim to be achieved is to remarkably improve the cycle stability, the rapid charge and discharge performance and the overall energy density of the battery by optimizing the structural design and the preparation method, and not only inhibit pore collapse by utilizing the high mechanical strength of silicon carbide, but also stabilize an SEI film by a conductive network of a carbon layer, thereby solving the technical problems. In order to solve the technical problems, the first aspect of the invention provides a preparation method of a mesoporous carbon/silicon carbide double-matrix silicon carbon composite anode material based on CVD, which comprises the following specific steps: s1, carrying out pretreatment and activation treatment on mesoporous carbon to obtain preposed mesoporous carbon; s2, placing the front mesoporous carbon into a CVD reactor, introducing a silicon carbide precursor gas, and depositing a silicon carbide interface layer on the surface of the front mesoporous carbon to obtain middle mesoporous carbon; s3, switching silicon carbide precursor gas into silicon source gas, wherein the silicon source gas contains production inhibitor, limiting the growth of silicon crystal nucleus to a particle size of not more than 8nm through the production inhibitor, and depositing sub-nano silicon particles in situ in a pore canal of the mesoporous carbon to obtain the composite anode material. By adopting the technical scheme, the process realizes the accurate regulation and control of the silicon size,