Activated and high-energy milled carbons were halide modified via a vapor phase deposition of iodine. The physical and electrochemical properties of carbons iodated under various conditions were investigated. The iodine incorporation induced marked structural and electrochemical modification of activated carbons. These compounds resulted in a unique combination of high volumetric/gravimetric capacity. Specifically, the incorporation of halide leads to a 200–500% increase in volumetric capacity of carbon materials. The resulting improvement is brought about through a modification of the non-Faradaic performance and development of a psuedocapacitive reaction at approximately 3.1V. Both of these reactions have contributed to the higher volumetric capacity and are investigated relative to the synthesis conditions of the compound.