Vitamin K as a high-performance organic anode material for rechargeable potassium ion batteries

Potassium ion batteries (PIBs) have drawn considerable attention owing to the low cost and high natural abundance of potassium. However, risks associated with the extremely high activity of potassium metal have motivated the search for alternative anode materials with high performance and good safety. Herein, an essential element of the human body, vitamin K, is applied as an organic redox-active electrode material for PIBs. This biomolecule has a quinone structure with two active redox carbonyl groups, which can provide a theoretical specific capacity of 313.5 mA h g^-1. After hybridization with graphene nanotubes (GNTs), the composite delivered a high reversible capacity of 300 mA h g^-1 and maintained 222.3 mA h g^-1 after 100 cycles at a current density of 100 mA g^-1 with a coulombic efficiency of ∼99%. Moreover, at higher current densities of 200, 500, and 1000 mA g^-1, it maintained high discharge capacities of 203, 181, and 165 mA h g^-1, respectively. The enhanced electrochemical performance of the composite might be attributed to the improved electronic conductivity and inhibition of vitamin K dissolution into the organic electrolyte. This biomolecule-based electrode offers a new alternative approach to the development of PIBs.