超临界CO2流体辅助合成Si-Fe-Fe3O4-C复合材料及储锂性能

硅碳负极是未来锂离子电池材料发展的重点方向之一，本文针对传统球磨法制备硅碳负极复合不均匀、界面融合差等问题，提出了一种超临界二氧化碳(scCO₂)流体介质球磨合成Si-Fe-Fe₃O₄-C复合材料的新方法。研究发现，纳米硅和中间相碳微球(MCMB)在scCO₂介质球磨混合过程中，CO₂和Fe反应先得到均匀分散的Si-FeCO₃-C前驱体，然后FeCO₃原位高温固相分解得到Si-Fe-Fe₃O₄-C复合材料。同时，在scCO₂流体渗透下，MCMB剥离成石墨片，并与纳米硅和Fe-Fe₃O₄实现较好的界面融合，Fe-Fe₃O₄的引入显著提升了硅碳负极的储锂容量、循环稳定性和倍率性能，Si-Fe-Fe₃O₄-C复合材料在0.2 A·g?1下100次循环后可逆容量保持在1065 mA·h·g?1。本方法利用超临界流体渗透性好、扩散能力强等特点，合成工艺简便，容易工业化实施，具有商业化开发潜力。 

Supercritical CO2 fluid assisted synthesis of Si-Fe-Fe3O4-C composites and lithium storage performance

Silicon-carbon anode is an important issue for the development of lithium-ion battery materials. Aiming at the problems of uneven combination and poor interfacial contact of silicon-carbon anode prepared by traditional ball milling, this paper proposes a new strategy to synthesize Si-Fe-Fe₃O₄-C composite by ball milling in supercritical carbon dioxide (scCO₂) fluid medium. It is found that during the process of ball milling mixture of nano-silicon and mesophase carbon microspheres (MCMB) in the scCO₂ medium, CO₂ and Fe reacts firstly to form a uniformly dispersed Si-FeCO₃-C precursor, and then in situ high temperature decomposition of FeCO₃ solid phase results in final Si-Fe-Fe₃O₄-C product. Under the infiltration of scCO₂ fluid, MCMB microspheres exfoliate into graphite flakes, and achieve ideal combination with nano-silicon and Fe-Fe₃O₄. The introduction of Fe-Fe₃O₄ in the composite has significantly improved the lithium storage capacity, cycle stability and rate performance of silicon-carbon anode, the synthesized Si-Fe-Fe₃O₄-C composite material maintains a reversible capacity of 1065 mA·h·g?1 after 100 cycles at 0.2 A·g?1. The method shows the merits of facile operation procedure, easy industrial production and potential commercial application basing on the supercritical fluid permeability and strong diffusion ability.