Abstract
The development of multielectron redox-active cathode materials is a top priority for achieving high energy density with long cycle life in the next-generation secondary battery applications. Triggering anion redox activity is regarded as a promising strategy to enhance the energy density of polyanionic cathodes for Li/Na-ion batteries. Herein, K(2)Fe(C(2)O(4))(2) is shown to be a promising new cathode material that combines metal redox activity with oxalate anion (C(2)O(4) (2-)) redox. This compound reveals specific discharge capacities of 116 and 60 mAh g(-1) for sodium-ion batterie (NIB) and lithium-ion batterie (LIB) cathode applications, respectively, at a rate of 10 mA g(-1), with excellent cycling stability. The experimental results are complemented by density functional theory (DFT) calculations of the average atomic charges.