Comparative insight into negative electrode performance in lead-acid and lead-carbon batteries under high-load and partial state-of-charge cycling profiles

The resulting cycle performances from our previous studies are compared for operation in 50% depth-ofdischarge (DoD) and 17.5% DoD at 50% state-of-charge (SoC) cycling profiles, representing two working
modes: high load and partial state-of-charge, respectively. This comparative analysis examines test cells
configured with negative electrode as the capacity-limiting component. This comparative analysis, based on
prior independent studies, highlights the distinct degradation mechanisms influencing negative electrode sulfation, morphology, and electrochemical behavior between the two cycling regimes. While the 50% DoD profile
creates more overall sulfation due to frequent discharge to half of rated capacity, it produces greater evenness in
PbSO4 distribution across the electrode cross-sectional area. In contrast, the 17.5% DoD profile, with lower
charge/discharge loads in each cycle of a test unit, exhibits an uneven distribution of PbSO₄ mostly concentrated
at the edge region and larger crystal sizes due to sustained undercharge. Cyclic voltammetry reveals that the
uneven sulfation in the 17.5% DoD profile results in increased hydrogen evolution reaction despite less overall
degradation. This comparative insight suggests different practical optimization strategies for each operational
mode, with periodic recovery charges at low current being particularly beneficial for long-term battery durability
in partial state-of-charge applications.