Potassium-enriched graphite for use as stable hybrid anodes in high-efficiency potassium batteries

Potassium-ion batteries (PIBs) have attracted significant attention due to their low cost and high energy density. Despite being a promising anode candidate for PIBs, graphite is still plagued by limited capacity and fast capacity degradation with low coulombic efficiency (CE). Herein, we propose a high-capacity and highly stable potassium-enriched graphite (KRG) anode which surpasses the limitation of parent graphite. The KRG is characteristic of possessing the potassium-graphite intercalation compounds as a potassiophilic host for uniform and high-efficiency plating/stripping of potassium metal. The robust mixed conducting network possessed by the KRG is beneficial for mitigating drastic volume change of the electrode and improving ion/electron transport. A specific capacity of ∼520 mAh/g was demonstrated for KRG anode as the optimized value to maximize the capacity storage while suppressing dendrites growth. With a stable solid-electrolyte interphase buildup, the KRG/Prussian blue full cell with a controlled anode/cathode capacity ratio of 1.1:1 can deliver a high capacity of 108 mAh/g with a CE of 99% after 180 cycles at 1C. Our results provide valuable insights into the rational design of graphitic anodes for high-energy-density PIBs.