Lawrence Berkeley National Laboratory

Polymer-derived and micro-cracked silicon carbonitride (SiCN) materials have been successfully synthesized via pyrolyzing from poly(diphenylcarbondiimide) and post-treating with different molar concentration of sodium hydroxide (NaOH) aqueous solution (0.2-5.0 mol L−1). The as-prepared SiCN materials have been used as anodes for lithium ion batteries. Electrochemical charge-discharge measurements indicate that the SiCN with the 0.5 mol L−1 of NaOH treating (SiCN-0.5-NaOH) shows the best electrochemical performance. It exhibits a high initial specific extraction capacity of 1159.5 mAh g−1 and stable capacity of 900 mAh g−1 at current density of 40 mA g−1. The morphology and structure measurements show its surface is rough, and many micro-sized cracks are formed. The special performances of NaOH-treated SiCN anodes are attributed to non-conductive Si3N4 phase elimination from SiCN matrix by NaOH treatment, and lithium ion transfer channel enrichment by the formation of micro-cracks.