Practical implantation of Si nanoparticles in Carbon-coated alpha-FeSi2 matrix for Lithium-ion batteries

Abstract

Silicon, one of the most promising anodes, has been facing challenges to improve continuous increased electrode expansion during the cycles, resulting in a deteriorated conducting network between the particles from the accelerated side reactions with the electrolytes and inferior long-term cycle performance of the graphite counterpart for practical application. Herein, we demonstrated an easy and scalable synthesis of Si nanoparticles in the carbon-coated and interconnected alpha-FeSi2 matrix where alpha-FeSi2 acts as a buffer matrix for the expansion of adjacent Si, and the uniformly-coated carbon surface layer on the alpha-FeSi2 matrix enhances conductivity and reduces the side reaction of electrolyte and structural degradation. Our results reveal that the alpha-FeSi2/Si/carbon (FSC) exhibits better electrochemical properties in the lithium-ion cell compared to alpha-FeSi2/Si (FS), benchmarking samples of alpha-FeSi2/Si (BM-FS) and carbon nanotubes (CNTs) grown FS (BM-FS/CNT). The FSC anode in the full cell with the areal capacity and electrode density of anodes of 2.25 mAh cm(-2) and 1.7 g cc(-1), respectively, exhibited quite a comparable capacity retention to a graphite counterpart, showing 83 % at a rate of 0.7C charging /0.5C discharging rate between 4.4 and 3 V after 200 cycles.