Graphite-catalyzed carbonization of biowaste unlocks energy-dense, high-rate, and long-lifespan potassium-ion batteries

Biowaste-derived hard carbon (HC) has emerged as a promising anode material for potassium-ion batteries (PIBs) due to its low cost and sustainability. However, the complex surface chemistry and large specific surface area of such HC often result in high working potentials, along with poor initial Coulombic efficiency (ICE). To address these challenges, this study introduces a graphite-catalyzed carbonization strategy to convert biowaste into high-performance HC anode materials, paving the way for energy-dense, high-rate, and long-lifespan PIBs. The results demonstrate that graphite promotes the formation of pseudo-graphitic domains and significantly reduces the specific surface area of the HC. Consequently, the prepared HC exhibits a low average depotassiation potential of 0.32 V (vs. K⁺/K) and delivers a specific capacity of 283.3mAh g⁻¹ with a high ICE of 84.42 %. When coupled with a high-voltage K₂Mn[Fe(CN)₆] cathode, the full-cell, without requiring pre-cycling treatment for either electrode, achieves an average discharge voltage of 3.43 V, a specific energy of 264 Wh kg⁻¹ (based on the total mass of K₂Mn[Fe(CN)₆] and HC), excellent rate performance (retaining 90 % of capacity at 0.1C when the charge–discharge rate is increased to 1.0C), and remarkable cycling stability, with 90.5 % capacity retention after 1500cycles at 0.5C.