Studies on chalcopyrite phosphides and phenolic acid-based derivatives towards lithium storage and chemical sensors

Abstract

Li-ion batteries are among the highly promising power sources for many emerging technologies, including electric vehicles and smart grids. However, an increased demand for energy density and long cycle life cannot be satisfied by the commercially available graphite anode at present as it represents a modest inherent specific capacity (372 mAh/g) and poses major safety risks due to lithium plating and subsequent growth of lithium dendrites. Si-based anodes have attracted significant attention due to their ultra-high theoretical capacity of 4200 mAh/g, but the practical application is limited due to their extreme volume expansion upon lithiation. In this context, the synergistic effect of combining group 14 elements (Si/Ge/Sn) with the group 12 (Zn/Cd) and 15 (P) elements is studied towards the formation of ternary chalcopyrite phosphides, which represent high performance with high initial coulombic efficiency, large specific capacity, suitable working potential, high-rate capability, and long-cycling life as compared to elemental Si-based anodes. The additional elements act as buffer matrix to cope with the volume expansion of Si-based anodes and also improve the lithium conductivity due to the formation of Li3P intermediate phases during alloying reactions. The phase change and lithiation intermediates are analyzed by using in-situ Raman and diffraction techniques. The application of these chalcopyrites is extended to photo-assisted anodes, where improved performance is observed along with self-charging characteristics under solar radiation. Further, these phosphides are studied for their humidity-sensing properties, where a fast response and high selectivity is observed for varying humidity conditions. In addition, phenolic acid-based derivatives are explored as potential organic electrode materials for Li-ion batteries, where highly reversible lithiation characteristics are analyzed by using Raman, FTIR, and XPS characterization techniques.