• CTR-derived carbon materials were synthesized via direct carbonization at 700–1000°C, converting hazardous solid waste into valuable anodes for potassium-ion batteries.
• The optimal CTRC-900H electrode delivered a high reversible capacity of 265.6 mAh·g−1 at 50 mA·g−1 and retained 93.8% capacity after 100 cycles, demonstrating excellent cycling stability.
• Electrochemical analysis revealed that potassium storage is dominated by surface-induced capacitive processes, following an 'adsorption–weak intercalation' mechanism.
• This work provides a sustainable, low-cost strategy for high-value-added utilization of coal tar residue, addressing both waste management and energy storage challenges.