The properties of different forms of carbon and their potential, as active mass additives, for influencing the performance of valve-regulated lead–acid batteries are reviewed. Carbon additives to the positive active-mass appear to benefit capacity, but are progressively lost due to oxidation. Some forms of carbon in the negative active-material are able to resist the tendency to sulfation during high-rate partial-state-of-charge operation to some considerable extent, but the mechanism. | Available online at ELSEVIER Journal of Power Sources 157 2006 3-10 Review The role of carbon in valve-regulated lead-acid battery technology . Moseleya . Nelsonb . Hollenkampc a International Lead Zinc Research Organization 2525 Meridian Parkway Research Triangle Park North Carolina NC 27709 USA b Recombination Technologies LLC 909 Santa Fe Drive Denver Colorado CO 80204 USA c CSIRO Energy Technology Box 312 Clayton South Vic. 3169 Australia Available online 29 March 2006 Abstract The properties of different forms of carbon and their potential as active mass additives for influencing the performance of valve-regulated lead-acid batteries are reviewed. Carbon additives to the positive active-mass appear to benefit capacity but are progressively lost due to oxidation. Some forms of carbon in the negative active-material are able to resist the tendency to sulfation during high-rate partial-state-of-charge operation to some considerable extent but the mechanism of this benefit is not yet fully understood. 2006 Elsevier . All rights reserved. Keywords Valve-regulated lead-acid Batteries Carbon Capacity Power Cycle-life Contents 1. Introduction. 3 2. Allotropes of carbon and their properties. 3 3. Conventional use of carbon in lead-acid batteries. 5 4. Effects of carbon on the behaviour of the positive plate. 5 5. Increased levels of carbon in the negative plate. 6 6. Asymmetric electrochemical capacitors. 8 7. Conclusions and ultimate prospects. 9 References. 9 1. Introduction For many years carbon has been favoured as an additive to the negative active-material in lead-acid batteries despite the fact that there has never been universal agreement on the reasons for its use 1 . Now that the valve-regulated version of the battery VRLA is being exposed to high-rate partial-state-of-charge HRPSoC operation in various applications 2 evidence is This review is one of a series dealing with the role of carbon in electrochemical energy storage.