Realization of Lithium-Ion Capacitors with Enhanced Energy Density via the Use of Gadolinium Hexacyanocobaltate as a Cathode Material.

Li-ion storage devices having superior energy density are critical for one-time-charge long-term applications. Currently, much research endeavor is directed at enhancing the energy density of hybrid Li-ion capacitors, which incorporate the high energy of conventional Li-ion batteries with the elevated power density of Li-ion supercapacitors. Herein, we prepare orthorhombic GdCo(CN)6 as a new Prussian blue analogue (PBA), showing that this compound offers excellent energy/power densities (605 W·h kg-1 and 174 W kg-1, respectively) and features Li-ion storage capacities (352 and 258 mA·h gelectrode-1 at 100 and 1000 mA g-1, respectively) that are almost twice higher than those of other cathode materials utilized in hybrid Li-ion capacitors. Thus, this study not only opens a new path for the exploration of new-type PBAs, but also provides insights on the use of lanthanides in energy storage applications.