Synthesis and Electrochemical Characterization of Novel Category Si3-xMxN4 (M= Co, Ni, Fe) Anodes for Rechargeable Lithium Batteries

A novel category Si3N4 anode and a series of doped derivatives of silicon nitride with a general formula Si3-xMxN4 (M= Co, Ni and Fe) were synthesized, characterized and exploited as possible alternative anodes for rechargeable lithium batteries through the present study. The compound Si3N4 exhibited inferior capacity (~ 100 mAh/g) compared to the carbonaceous and lithiated nitride anodes. On the other hand, the Si3-xMxN4 compounds (M = Co, Ni, Fe) qualified themselves as better anodes with a specific capacity of at least 130 ~ 470 mAh/g, and lesser capacity fade (< 20 %) after 50 cycles. Particularly, Si3-xFexN4 anode showed the highest specific capacity of 470 mAh/g, wheras the rest of the anodes, viz., Si3N4 and Si3-xMxN4 (M= Co, Ni) exhibited better capacity retention upon cycling. The lowest average oxidation number and the higher ionic radius of Fe compared to Co and Ni metals are believed to be responsible for the improved specific capacity values and the excellent coulumbic efficiency (99%) of Si3-xFexN4 anodes, via. restricted formation of passivating surface film.