Activated carbons with high micro-/meso-porosity derived from biomass are increasingly popular as sustainable materials. However, these carbons often struggle with low carbon content and limited structural stability. Here, we present Mongolian anthracite-based carbons synthesized via carbonization and chemical activation. Structural analysis shows that Act-MRA samples develop plate-like morphologies with reduced particle size and greater porosity as KOH content increases. The Act-MRA samples have a disordered carbon structure with small graphitic domains, even at higher KOH ratios without significant crystal defects. Notably, Act -MRA3 displays a large specific surface area and high pore volume, with welldeveloped micropores (7–20 Å) and mesopores (20–50 Å) that expand as KOH ratios rise. Electrochemical tests indicate that Act -MRA3 achieves high specific capacitance (220.6 F/g at 5 mV/s) and rate retention (~ 80% at 300 mV/s), owing to its optimized pore structure and enhanced ion transport. These findings underscore the importance of tailored pore structures and defect engineering in boosting activated carbon performance for energy storage.