The reaction mechanism of V2O5 xerogel and the electrode properties of V2O5/carbon composites in an aqueous electrolyte solution were examined to obtain high-performance electrodes for rechargeable proton batteries. Based on the results of the chemical analysis of the electrode, proton intercalation is suggested to be the dominant reaction mechanism. By using the relationship between the capacity and current density of a thin-film electrode consisting of V2O5 xerogel, the diffusion coefficient in the V2O5 xerogel was determined to be 8 +/- A 1 x 10(-11) cm(2) s(-1). The V2O5/carbon composite electrode was prepared by drying a homogeneous dispersion of carbon particles in the V2O5 sol. The composite electrodes showed a large capacity of 460 mAh g(-1) at a current density of 1 A g(-1) and maintained a relatively large capacity of 160 mAh g(-1) at 100 A g(-1). These properties were attributed to the homogeneous microstructure of the V2O5/carbon composites. The V2O5/carbon composite electrodes were thus revealed as high-performance electrodes with large capacities and excellent high-rate capabilities.