From biomass to battery: lignin-derived carbons achieving unprecedented high capacity retention in potassium batteries

The increasing demand for sustainable energy storage solutions has led to a growing interest in post‑lithium-ion battery technologies. In this context, potassium-ion batteries (KIBs) have emerged as a promising alternative for large-scale applications due to the high natural abundance, cost-effectiveness, and favorable electrochemical properties of potassium. Hard carbon materials derived from biomass are particularly attractive as KIB anodes, offering a sustainable solution with appropriate structural and electrochemical behavior. This study investigates the electrochemical performance of hard carbons derived from lignin-rich biomass residues, which were chemically activated with different KOH ratios. Structural, morphological, and compositional analyses were conducted to elucidate the influence of activation parameters on porosity, chemical composition, graphitization degree, and interlayer spacing. Additionally, chemical composition and formation mechanism of the solid electrolyte interphase layer were in-depth analyzed. This work underscores the potential of biomass-derived hard carbons as sustainable anode materials for next-generation KIBs, aligning with circular economy principles and renewable energy storage strategies, and also targeting unprecedented electrochemical performances in terms of device durability. Turning industrial lignin waste into powerful carbon materials for next-generation potassium-ion batteries. Our eco-friendly electrodes combine high performance with long-term stability, paving the way for greener and more affordable energy storage solutions beyond lithium. • Lignin-derived hard carbons show exceptional cycling stability in K-ion batteries. • Optimized 1:1 KOH activation balances porosity and interlayer spacing for performance. • SW11 sample retains 88.8 % capacity after 500 cycles at 0.05 A g −1 . • Pseudocapacitive behavior dominates charge storage mechanism of best-performing HCs. • SEI layer is rich in stable KF and K₂CO₃, enhancing electrode durability.