Documenting capacity and cyclic stability enhancements in synthetic graphite potassium-ion battery anode material modified by low-energy liquid phase ball milling

Graphite is the most promising anode material for potassium-ion batteries due to the attractive theoretical capacity of 278 mAh g⁻¹ and its low potential operation with respect to a potassium reference electrode. However, it is reported that its practically achievable capacities and cyclic stabilities are often relatively poor, which may impact the practical application of graphite in this new type of batteries. The recent results indicate that mechanical milling can be a possible modification method for graphitic materials to improve their electrochemical behaviors. In this work, we document the effects of liquid-phase ball milling conducted under low-energy conditions on the capacity levels and cyclic stability of the commercially available synthetic graphite. The obtained thin graphite flakes with high surface area lead to a much improved electrochemical performance of the electrodes with high reversible capacity of 227 mAh g⁻¹ after 500 cycles at 100 mA g⁻¹ (capacity decay as slow as 0.0043% per cycle and a capacity retention of ~98%) and de-potassiation capacity of 226 mAh g⁻¹ at 4 A g⁻¹ current. This study demonstrates the possibility of capacity and cyclic stability enhancement in graphitic materials by mechanical milling under appropriately selected milling conditions.