Flux growth of patterned LiCoO2 crystal arrays directly on a Pt substrate in molten LiNO3

Abstract

We demonstrate a new way to prepare hollow-structured LiCoO₂ crystals directly on a Pt substrate for the first time through a combination of semi-additive electrodeposition of a Co core and subsequent flux growth in molten LiNO₃. The reaction process was characterized by time-dependent X-ray diffraction and scanning electron microscopy. The vertically oriented crystals having a platelet shape grew densely on the Co dot surface. The crystal growth was driven by supersaturation in the same manner as the flux growth. Significantly slower oxidation of the Co core and rapid lithiation of Co₃O₄ lead to pore formation, which suggests that slow oxygen diffusion in the Co core is rate limiting. Galvanostatic tests revealed that the LiCoO₂ crystal array exhibited typical capacity–voltage profiles with no heavy capacity loss during the first three cycles without any additives.