MnFe Prussian blue analogue-derived P3-K0.5Mn0.67Fe0.33O1.95N0.05 cathode material for high-performance potassium-ion batteries

Abstract

Potassium-ion batteries (PIBs), with their high theoretical energy density and abundant natural resources, are emerging as one of the most promising candidates for next-generation energy storage systems. Nevertheless, they suffer from large volume expansion and sluggish K+ transport due to the huge ionic radius of K+, resulting in limited cyclic life and rate performance. Therefore, accelerated transport kinetics may be the key to designing electrodes with excellent potassium storage properties. Herein, we develop a new synthetic method to in-situ construct a high-efficiency PIB cathode, N-doped P3-typed K0.5Mn0.67Fe0.33O1.95N0.05 nanosheets (denoted KMFON), using the low cost Prussian blue analogue Mn2[Fe(CN)6] as a precursor. Combining experimental results and theoretical calculations, the as-synthesized KMFON exhibits large interlayer spacing, small K+ migration energy barrier, high electronic conductivity, and fast K+ transport kinetics, which are attributed to the larger-sized N substitution O. It also manifests an initial reversible capacity of 104.2 mAh g−1 at 20 mA g−1, a rate capability of 41.5 mAh g−1 at 500 mA g−1, and a high discharge capacity of 52.2 mAh g−1 after 300 cycles at 100 mA g−1. Moreover, the KMFON//pitch-derived soft carbon full cell exhibits a satisfactory rate performance of 49.4 mAh g−1 at 200 mA g−1 and a good cycling performance of 46.8 mAh g−1 after 200 cycles at 100 mA g−1, indicating the great potential of KMFON as a cathode material for PIBs.