The cycle life of commercial lead-acid batteries could potentially be improved by suppression of the battery aging mechanism. In this context, one of the main challenges is the irreversible phase transformation from PbSO4 to PbO2 at the positive electrode upon charging. We herein report a nanoparticle strategy at tens of nanometers length scale that can enhance the reversible phase transformation from PbSO4 to PbO2 upon charging, thus potentially extending the lifetime of these batteries. Our combined theoretical and experimental studies suggest that control over the initial size of the PbO2 nanoparticles at the positive electrode is critical to the aging mechanism, with PbO2 nanoparticles of similar to 100 nm in diameter suppressing sulfation, which leads to a reversible phase transformation from PbSO4 to PbO2. In addition, PbO2 nanoparticles (100 nm in diameter) can provide a greater robustness in the context of shedding of the active materials from the positive grid. These results suggest that lead-acid batteries can be operated with an extended lifetime partly by addressing the intrinsic aging issues associated with irreversible sulfation. (C) 2017 The Electrochemical Society. All rights reserved.