The researchers studied why zinc-nickel batteries lose capacity over time. They found that the low efficiency of the zinc anode causes hydrogen to build up, preventing the cathode from fully discharging. This imbalance leads to faster battery capacity decay. By adding nano Bi powders to the anode, they reduced hydrogen buildup and improved battery performance. The study shows that the decline in battery life is not just due to electrode changes but also to the mismatch in efficiency between the cathode and anode.