A Failure-Cascade View of Cathode Degradation and Intervention Strategies in Aqueous Zn-Ion Batteries

Abstract

Aqueous zinc-ion batteries are attractive as safe and low-cost candidates for stationary energy storage, but cathode degradation still limits their practical use. Manganese oxides, vanadium-based hosts, and Prussian blue analogues are among the most studied cathodes, yet none currently delivers the cycle life required under realistic conditions. Many reports treat their degradation modes, including metal dissolution, structural instability, and by-product formation, as separate issues rather than stages of a linked process. Here, we propose a failure-cascade framework that views cathode degradation as a sequential chain in which an upstream trigger gives rise to secondary reactions, by-product accumulations, and transport limitations that eventually lead to cell failure. We identify distinct triggers for each family: Mn dissolution in manganese oxides, intercalation-coupled chemo-mechanical strain in vanadium hosts, and vacancy-water coupling in Prussian blue frameworks. Recognizing that similar macroscopic symptoms can arise from different triggers explains why generic mitigation strategies often show limited effectiveness and motivates distinguishing upstream strategies that act on the trigger from downstream strategies that address propagated damage. This perspective offers a common lens for analyzing existing studies and directing future work toward interventions with the greatest impact on long-term stability.