▎ 摘　　要

Potassium ion batteries (PIBs) have drawn considerable interest because of the resource-abundance and tempting electrochemical potential of potassium. However, developing high-performance anodes for PIBs with superior reversible capacity and ultralong stability is still a huge challenge to meet the requirements of sustainable and cost-effective large area energy storage systems. To address the above-mentioned issues, we report for the first time a simple in situ growth strategy to synthesize pillared graphene nanosheets with expanded interlayer spacing as free-standing flexible electrodes for PIBs. The expanded interlayer spacing is confirmed to accelerate ion transmission by kinetics. The graphene nanosheet/NiO-500 (GS/NiO-500) composite assembled binder-free flexible anode delivers ultrahigh reversible capability (416.1 mA h g(-1) at 0.1 A g(-1)), excellent rate performance (305.6 mA h g(-1) at 1 A g(-1)) and superior capacity retention (82.6% over 3000 cycles at 1 A g(-1)). This study provides ideas for the development of fast charging potassium electrode materials and promotes the commercialization of large-scale energy storage systems.