A study of the incorporation of bromine in activated carbons showed that highly reactive bromine facilitated a charge transfer reaction with the host carbon leading to lateral structural disordering, formation of polybromide compounds, reduction of BET surface area by preferential micropore filling and a net increase (over 100%) in the gravimetric and volumetric electrochemical capacity of activated carbons. The effect of chemical bromination was investigated focusing on various physical and electrochemical properties. Bromination is compared and contrasted with iodation to generalize halidation as a possible route to improve activated carbons for electrochemical energy storage.