Oxygen-driven bulk defect engineering in carbon to reduce voltage hysteresis for fast potassium storage at low voltage

Reducing the voltage hysteresis and enhancing the rate performance of carbon anode materials are critical for boosting the energy and power density of potassium-ion full-cell devices. In this study, we report an oxygen-driven bulk defect engineering in carbon to reduce the voltage hysteresis, enabling reversible and fast potassium storage at low voltage. Through high-concentration hydrothermal treatment, the oxidized pitch structure units undergo a process where oxygen bridge bonds are formed, resulting in the creation of interconnected bulk structures. The oxygen-containing functional groups are removed during carbonization, thereby introducing bulk defects into the carbon materials to enhance the kinetics of K+ insertion in the nanographite domains. The bulk carbon anode achieves low voltage hysteresis, high reversible capacity below 1 V (248 mAh g-1 at 0.05 A g-1) and high-rate (192 mAh g-1 at 1 A g-1). Additionally, the full cell exhibits a discharge plateau at approximately 3.1 V and high cyclic stability (95 % capacity retention from the 10th to the 120th cycle). This study presents a novel approach for constructing bulk defects in carbon materials to achieve efficient potassium storage at low potential, thus advancing the application of advanced carbon anodes in potassium-ion batteries.