Prussian blue analogues: A new class of anode materials for lithium ion batteries

Metal-organic frameworks (MOFs) have attracted extensive interest in the context of energy storage due to their high surface areas, controllable structures and excellent electrochemical properties. In particular, Prussian blue analogues (PBAs) have recently gained attention as a new class of cathode materials for rechargeable batteries. However, the anode properties of the host framework have been very limited. Herein, we demonstrate that nanoparticles of cobalt hexacyanocobaltate and manganese hexacyanocobaltate, typical Prussian blue analogues with the chemical formula M₃^II[Co ^III(CN)₆]₂·nH₂O (M = Co, Mn), can be operated as novel battery anodes in an organic liquid-carbonate electrolyte. The Co₃[Co(CN)₆]₂ material exhibits a clear electrochemical activity in the voltage range of 0.01-3 V vs. Li/Li⁺ with a reversible capacity of 299.1 mA h g^-1. Furthermore, superior rate capability (as the current density increases from 20 to 2000 mA g^-1, the capacity retains about 34%) could be achieved, attributing to the small particle sizes and rapid transport of Li⁺ ions through large channels in the open-framework. We believe that this work provides a new insight into the electrochemical properties of PBAs and opens new perspectives to develop anode materials for rechargeable batteries.