Controllable engineering of intrinsic defects on carbon nanosheets enables fast and stable potassium storage performance

Defect-enriched carbon nanomaterials possess high potassium storage capacity and rapid ion transport capability; nevertheless, their rate performance is restricted by the deteriorated electronic conductivity induced by over-broken sp(2)-C conjugated structure. Herein, intrinsic defect-enriched carbon nanosheet (DCS) with controllable defect density is reported for the high-efficiency anode of potassium-ion batteries (PIBs). The DCS constructed by internal sp(2)-C configuration and external sp(3)-C defects can ensure good electron transport ability and afford abundant active sites for K+ storage. As PIBs anode, DCS-24 obtained by ball-milling for 24 h with optimized defect density delivers a high specific capacity of 270.9 mAh g(-1) at 0.5 C, an excellent rate performance (189 mAh g(-1) at 10 C), as well as long cycle durability (255.1 mAh g(-1) over 3000 cycles at 1 C). Electrochemical results and density functional theory simulations indicate that the intrinsic defects of carbon materials improve the capacitive K+ storage capacity, speed up the K+ diffusion, and lower the K+ adsorption energy.