碳材料改性 SiOC 负极在锂离子电池中的研究进展

Lithium-ion batteries are considered as the most promising chemical power source due to their high energy density, good safety, and environmental friendliness. As a key component of batteries, anode material plays an important role on the electrochemical performance. Graphite, Li₄Ti₅O₁₂ and Si-based materials have attracted much attention as anode materials in lithium-ion batteries. Among these materials, graphite has good conductivity, small volume change, high initial coulombic efficiency, and low cost. As a conventional anode material for lithium-ion batteries, graphite is first commercially applied. However, its low theoretical capacity is the main factor restricting the development of high energy density lithium-ion batteries. Li₄Ti₅O₁₂ anode material is considered to have a great development potential due to its stable structure during lithiation and delithiation processes and good safety. However, its low theoretical capacity and high cost restrict its practical application. Si has a high theoretical capacity, but it has a disadvantage of large volume expansion during lithiation and delithiation processes, resulting in the poor safety of batteries. The composite of Si and carbon materials is considered as an effective strategy for stabilizing electrodes. SiOC is considered as one of the high potential anode materials for lithium-ion batteries due to its excellent properties such as high theoretical specific capacity, good mechanical flexibility and structural stability, and facile structure regulation. However, the low conductivity of SiOC leads to its poor rate performance and cycling ability, thus restricting its development and application in the field of lithium-ion batteries. The composition of SiOC materials can be controlled through optimizing the composition, structure, and pyrolysis conditions of polymer precursors. Carbon material has high specific surface area, high mechanical stability, and excellent electrical conductivity. Composite with SiOC anode materials, the conductivity of SiOC can be improved, accelerating the transfer rate of lithium ions during lithiation and delithiation processes. Carbon material can act as an inert layer to reduce the volume effect of SiOC. SiOC/C composites can improve the conductivity effectively, thereby significantly improving the electrochemical performance of lithium-ion batteries as anode materials. For elucidating the structure of SiOC, this review analyzes the mechanism of lithium ions storage on SiOC anodes. To address the poor conductivity of SiOC, the composite process of graphite, carbon nanotubes, graphene and carbon nanofibers with SiOC anode materials are reviewed. The design of modification based on different carbon materials and between the anode microstructure and electrochemical performance are discussed. The selection of carbon materials is particularly important for the electrochemical performance of SiOC/C composites. Nanocarbon is beneficial to constructing conductive networks, and after composite with SiOC, there are many micro-/meso-pores inside, which enhances the capacitance effect and further improves the electrochemical performance. Therefore, the electrochemical performance of SiOC/nanocarbon composite materials is better than that of SiOC/traditional carbon composite materials. The rate capability and cycling stability of SiOC-based lithium-ions batteries are improved. Summary and prospects SiOC-based anode materials have a great potential for lithium-ion batteries, but the poor conductivity is the main problem that make it difficult to commercialize. The SiOC/C anode materials combine the high conductivity of carbon materials with some advantages of high capacity, stability, and mechanical flexibility of SiOC. Among them, SiOC/nanocarbon composite materials are developed due to their superior electrochemical performance. Although some progresses are achieved in the design of SiOC/C anode for the lithium-ion batteries, some challenges still remain in practical application. The main problems existing in SiOC/C anode materials are that the size of SiOC is larger, resulting in a lower utilization of active sites. The preliminary research conducted on nitrogen-doped carbon indicate that more active sites can be obtained via utilizing the defects. However, it is still necessary to explore the effect of other doping elements or through multi-component composites. To further enhance the feasibility of electrochemical performance, the lithium ions storage mechanism of SiOC anode materials still needs a further research. The detailed structure evolution of SiOC can be revealed during lithium ions storage process through some advanced in-situ characterization techniques. The lithium ions storage mechanisms can be further clarified, and, the electrochemical performance of SiOC-based anode materials can be improved more effectively. Improving the electrochemical performance and safety of lithium-ion batteries is a goal pursued by many researchers. Overcoming the above problems can lead to the widespread application of SiOC-based anode materials in high energy lithium-ion batteries, even in areas such as lithium sulfur batteries, sodium ion batteries, and potassium ion batteries.