Nitrided Silicon-Based Composite Anodes for Lithium Rechargeable Batteries

There are growing research interests in developing high energy density lithium ion batteries with stable cycling performances and longer cycle life. Silicon is a potential candidate for an anode material due to its theoretical specific capacity (4,200 mAh/g), which is more than ten times the value of the currently used anode material, graphite (370 mAh/g). One of the main challenges for silicon as an anode material is its huge volume expansion (~400%) upon the formation of silicon-lithium alloys, resulting in the pulverization of electrodes and performance degradation. Due to this, strategies have led to the use of nano-sized Si morphologies to improve the cyclic performance. This paper reports two chemical vapor deposition (CVD)-based efforts in synthesizing nitrided silicon anodes: (1) nitriding of Si nanoparticles (SiNP) and (2) reduction of SiNP/graphene oxide composite. Both approaches are performed using NH₃ as the nitride source. For (1), the silicon nanoparticles were doped, then dispersed within a graphene matrix to form a composite anode. A formed SiNP/graphene oxide composite anode was then reduced in (2) forming a composite with both nitride Si and graphene. These anode materials were investigated by spectroscopy, microscopy and electrochemical techniques to characterize their composition and performance. The potential of these materials to produce anodes that display better volume stress management and thus improve the overall electrochemical cycling stability is presented.