Abstract <p>As a fundamental technology for the efficient and environmentally friendly utilization of coal, the process of coal gasification inevitably generates a substantial amount of waste in the form of coal gasification slag. In this study, we utilized coal gasification slag as a raw material to extract carbon sources, employing potassium hydroxide (KOH) as an activator to prepare porous carbon. The electrochemical performance of this porous carbon was investigated in lithium/sodium ion batteries. When the ratio of KOH to residual carbon is 3&#xa0;:&#xa0;1, the resulting material demonstrates excellent lithium storage performance as an anode, achieving a reversible specific capacity of 452.83 mA h g^–1 at a current rate of 0.1 C. Furthermore, after undergoing 100&#xa0;cycles at a current density of 0.5 C, the capacity remains stable at 272.64 mA h g^–1. Conversely, when adjusting the KOH to carbon ratio to 1 : 1, optimal sodium storage performance is observed; specifically, the initial specific discharge capacity reaches 165.56 mA h g^–1 at a current density of 1 A g^–1. These results indicate that carbon residue derived from coal gasification holds significant potential as an anode material in alkali metal ion batteries.</p>