In situ XRD study of the structural changes of graphite anodes mixed with SiOx during lithium insertion and extraction in lithium ion batteries

A comparative study of crystallographic changes of the graphite anodes mixed with SiOx (in short, graphite-SiOx) to the pristine graphite during the lithium insertion and extraction under a half-cell condition is conducted by using in situ XRD for the first time. The structural changes of the graphite-SiOx anodes are relatively quantified from the time-dependent alteration in a and c lattice constants of their contained graphite during the charge and discharge. The results clearly confirm that Li+ ions are inserted in the SiOx domain prior to graphite during the charge, and the delithiation takes place later in SiOx during the discharge consistently. Via this in situ XRD study, the electrochemical effect of the amount of silicon active materials in the graphite-SiOx is also monitored up to the 160% increase of the capacity.