Abnormal-Stoichiometric K _xCl Crystal Decoration : A New Strategy to Improve K-Ion Storage Performance of Graphene Paper

Abstract

Carbonaceous materials are the most attractive choices for rechargeable potassium ion batteries (PIBs), but many K-ion batteries exhibit low specific capacity, limited cycling stability, and disappointed rate capability for the poor K-ions intercalation performance. Here, we chose graphene paper as the research object, fabricated a freestanding K-Cl―graphene paper electrode with abnormal-stoichiometric K_xCl crystals (K_xCl-rGO), and proposed a novel universal design strategy by using this electrode to achieve a high-efficiency K-graphene battery. Compared with pure rGO, K_xCl-rGO displays a high reversible capacity of 318 mAh g^-1 at 20 mA g^-1 (38.9% higher than rGO) and can retain a reversible capacity of 157 mAh g^-1 at 100 mA g^-1 after 500 cycles. The increased K-ion diffusion and enhanced electrical conductivity (the conductivity increased 83% than rGO) play a significant role in improving the potassium storage performance of K_xCl-rGO. What's more, for graphene with more functional groups, this pre-treatment improves the potassium storage performance of carbon materials more significantly (approximately doubled).

Keywords: abnormal-stoichiometric, KxCl, graphene, cation-π, K-ions storage