Understanding the lithiation intermediates of a silicon-based alloying anode by using operando diffraction and Raman spectroscopic techniques

In the present study, the effect of lithiation on a chalcopyrite phase, cadmium silicon phosphide (CdSiP2) anode is studied. This silicon-based phosphide anode helps in overcoming certain challenges encountered towards the application of elemental silicon anode for lithium-ion battery. Despite of having a fairly high band gap, this material represents outstanding cycling stability for lithium storage. Half-cell configuration results in a capacity of 970 mAh g-1 towards the end of 500 cycles at an applicable rate of 300 mA g-1, whereas a capacity of 645 mAh g-1 is obtained at a rate of 5000 mA g-1 for about 1800 cycles. The rate capability studies suggest highly reversible storage processes when switching from extremely high current rates such as 30 A g-1. Full-cell studies indicate highly stable charge-discharge voltage profiles with an appreciable capacity of around 400 mAh g-1 towards the end of 1400 cycles. Further, in-situ X-ray diffraction (XRD) analysis indicates conversion processes and confirms the formation of phases such as Li3P, LiCdP, Li5SiP3, Li13Si4, Li22Si5 and CdLi at various stages of charge-discharge cycling.