Impact of MWCNT passivation on single crystal Silicon electrode: An investigation of electrochemical performance and SEI formation

Abstract To investigate the role of Li intercalation and deintercalation on Si (111) and MWCNTs passivated Si (111) substrate, half battery cells were fabricated using these templates as anode material. The electrochemical properties of the fabricated cells were investigated by recording cyclic voltammetry (CV) measurements (scan rate of 0.5 mV/s) keeping the lower cutoff voltage as 10 mV, to ensure forced lithiation process so that Li-Si alloy formation can be an obvious phenomena. The standard Si bulk intercalation behavior and power storage behavior has been reported for a battery cell fabricated using Si (111) substrate and, MWCNTs passivated Si (111) substrate respectively, clearly depict the crucial role of MWCNTs used. The CV investigations reported herewith thus demonstrate that, the passivation of substrate can be a key to avoid etching of the Si to avoid cell capacity fading. Thus noticeable differences observed in CV after desired number of cycles, followed by ex-situ structural and chemical analysis of these anode materials suggest different electrochemical reactions that may occurring on the respective templates. Based on these results, hypothetical model for explaining lithiation and delithiation processes that may occur on MWCNT passivated Si (111) substrate is proposed.