Nanoporous coal via Ni-catalytic graphitization as anode materials for potassium ion battery

Abstract Potassium-ion batteries (PIBs), with advantages of abundant and easily accessible raw materials of potassium, are receiving increasing attention. Carbon-based materials are perceived as one of the most prospective PIBs anode materials due to their rational intercalation capacity and abundant resources. However, their intercalation chemistry reaction involving potassium intercalation/deintercalation can lead to a large irreversible volume change of anode, resulting in poor cycle performance. Herein, coal, with a natural pore structure which can eliminate negative effects of volume change in the intercalation processes, is explored for the anode in PIBs after a catalytically graphitized process. Graphitized coal via annealing catalysis with NiCl2·6H2O displays a superior K+ storage performance of 248.0 mAh g−1 at 50 mA g−1 after 100 cycles, which is 1.5 times as that of raw coal and 5.9 times as that of reference graphite.