Understanding copper sulfide formation from layered template and their use as power electrode materials in aqueous electrolyte
Abstract
Copper sulfide has received increasing attention as an electrode material in past decades. In this study, we report the synthesis of copper sulfide with layered copper hydroxide salt (LHS) (Cu2(OH)3NO3) precursors using different protocols. X-ray diffraction suggests the presence of numerous non-stoichiometric phases (Cu1-xS) and not a pure covellite phase and SEM images show particles with flower-like shape but different in size. The solidstate kinetic parameters of the reaction refined by the JMAK method indicate a pseudomorphic transformation controlled by 1D diffusion, different in term of precursors phase, reagents and protocol applied. The microwave method needs less energy to achieve the transformation than the amine digestion (AD) method and the morphology of particles is also different. Tested in sodium acetate electrolyte, CuS provides a maximum capacity of 67 mAh/g for AD, which is much higher than for the commercial grade CuS. This is explained by the difference in nanostructuration of the flower-like shape particles obtained from the layered template. Finally, CuS is used as both a positive and negative electrode material in a complete aqueous battery system but its redox process, which is strongly diffusion limited especially in the lower potential domain, prevents the whole system from operating at high power.