Synthesis of nanostructured materials by using metal-cyanide coordination polymers and their lithium storage properties

Abstract

Herein, we demonstrate a novel and simple two-step process for preparing LiCoO₂ nanocrystals by using a Prussian blue analogue Co₃[Co(CN)₆]₂ as a precursor. The resultant LiCoO₂ nanoparticles possess single crystalline nature and good uniformity with an average size of ca. 360 nm. The unique nanostructure of LiCoO₂ provides relatively shorter Li⁺ diffusion pathways, thus facilitating the fast kinetics of electrochemical reactions. As a consequence, high reversible capacity, excellent cycling stability and rate capability are achieved with these nanocrystals as cathodes for lithium storage. The LiCoO₂ nanocrystals deliver specific capacities of 154.5, 135.8, 119, and 100.3 mA h g⁻¹ at 0.2, 0.4, 1, and 2 C rates, respectively. Even at a high current density of 4 C, a reversible capacity of 87 mA h g⁻¹ could be maintained. Importantly, a capacity retention of 83.4% after 100 cycles is achieved at a constant discharge rate of 1 C. Furthermore, owing to facile control of the morphology and size of Prussian blue analogues by varying process parameters, as well as the tailored design of multi-component metal–cyanide hybrid coordination polymers, with which we have successfully prepared porous Fe₂O₃@Ni_xCo_3−xO₄ nanocubes, one of the potential anode materials for lithium-ion batteries, such a simple and scalable approach could also be applied to the synthesis of other nanomaterials for energy storage devices.