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 .