The structural and electrochemical study on the blended anode with graphite and silicon carbon nano composite in Li ion battery

•Blended anode with graphite and silicon nano composite is separately analyzed.•The complementary study using in-situ XRD and ex-situ NMR is conducted.•Relative Li amount inside silicon to graphite is observed.•Silicon is lithiated differently with graphite in a low state of discharge.•Silicon is degraded faster than graphite during cycling.

The in-situ XRD and ex-situ solid state NMR analysis are performed as well as electrochemical measurements to understand transfer properties of Li ion. Capacities of blended anode increased with increasing silicon carbon nano composite content and voltage profiles are differentiated with each other. In-situ XRD experiments reveal that structural changes of graphite are retarded as silicon carbon nano composite contents increased. 7Li NMR spectra are measured for blended anodes with different state of discharging and as a result, silicon is discharged prior to graphite at the initial stage of discharging. Moreover, asymmetric behaviors of structural changes between discharging and charging process are explained by comparison with 7Li NMR spectra of anodes at 20% of state of discharge during discharging and charging. Capacity fade of blended anode is investigated with NMR measurement on the different state of health and it is found that portions of graphite and silicon's faded capacities are differently evolved during calendar life and degraded.