Cyclic stability and C-rate performance of amorphous silicon and carbon based anodes for electrochemical storage of lithium

Polymer-derived, amorphous ceramics (PDCs) constituted from silicon, carbon, oxygen and nitrogen are promising candidates as anodes for lithium ion (Li+) batteries, having a reversible capacity of up to 800 mAh g−1. These measurements of lithium capacity are extended here to cyclic stability, high C-rate performance, and composition-range. The following new results are presented: (a) materials processed at 800 °C perform better than those synthesized at lower and higher temperatures, (b) materials with high oxygen content perform better than those with high nitrogen, (c) the SiCO materials are highly stable in cyclic loading, and (d) they are robust materials, capable of very high C-rates, without damage to their overall performance. Phenomenological analysis of composition dependent capacity suggests that Li is sequestered to mixed-bond tetrahedra of Si coordinated to both oxygen and carbon; it is argued that when oxygen is substituted by nitrogen the ability of these mixed bonds to bind to lithium in a reversible manner is severely diminished.