Fast Intercalation in Locally Ordered Carbon Nanocrystallites for Superior Potassium Ions Storage

Hard carbons (HCs) have great potential as anode material for high-performance potassium ion batteries (PIBs). However, due to the complexity of HCs, the relationship between their structures and potassium (K) storage behaviors is still not quite clear. Here, three types of HCs with different structures are designed for further understanding the electrochemical storage processes. Among them, the carbon spheres (CS) exhibit impressive rate performance (161.6 mAh g⁻¹ at 2 A g⁻¹) and cycle stability (140.2 mAh g⁻¹ at 2 A g⁻¹ after 500 cycles). The superior performance of CS can be mainly ascribed to the intercalation into its locally-ordered carbon nanocrystallites, and the charge/discharge processes are further characterized with significant pseudocapacitive dominating. Suitable nanocrystalline size and the ratio of defects with proper morphology are the key factors to improve K storage efficiency. This work will contribute to understanding the role of these factors in the K storage performance of carbon materials.