▎ 摘　　要

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 KxCl crystals (KxCl-rGO), and proposed a novel universal design strategy by using this electrode to achieve a high-efficiency K-graphene battery. Compared with pure rGO, KxCl-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 KxCl-rGO. What's more, for graphene with more functional groups, this pretreatment improves the potassium storage performance of carbon materials more significantly (approximately doubled). (C) 2022 Elsevier Ltd. All rights reserved.