Hierarchical polyhedron K2CoFe(CN)6 as promising cathode for rechargeable batteries

The electrochemical performance of Prussian blue and its analogues is affected by their structure and thus it is necessary to search for appropriate synthetic strategies to decrease the vacancies in the framework. A low-defect and high-crystal K2CoFe(CN)(6) with hierarchically polyhedral structure has been successfully synthesized by a facile coprecipitation method with controlling the nucleation rate. It has a well-defined structure, which can provide large channels for ion insertion/extraction. Benefiting from the kinetics optimization, the polyhedral K2CoFe(CN)(6) delivers a discharge capability of 102 mAh g(-1) at 20 mA g(-1) over 200 cycles and even remains 86 mAh g(-1) at 200 mA g(-1) after 200 cycles with capacity retention as high as 93% for Na-ion batteries. Moreover, this material as cathode is extended to Li-ion batteries and aqueous Na-ion batteries and also exhibits superior electrochemical performance. It capably keeps 92% and 85% retention after 200 cycles at 20 mA g(-1), respectively. Thus, this green material with superior electrochemical performance could be extended to more widespread storage applications. (C) 2018 Elsevier B.V. All rights reserved.