The Rise of Aqueous Selenium-Based Batteries: Challenges, Strategies, and the Path Forward

Aqueous metal-selenium batteries (AMSeBs) have emerged as promising candidates for safe, cost-effective, and high-energy-density energy storage, yet their development is hindered by challenges spanning electrode stability, reaction reversibility, and electrolyte compatibility. This review systematically explores the thermodynamic and electrochemical landscape of AMSeBs, integrating theoretical analysis with experimental advances to establish a rational design framework. First, by evaluating key parameters, including electrode potentials, volume change rates, solubility of metal selenides, and energy metrics, we identify promising systems such as Zn-Se and Cu-Se, along with unexplored candidates like Fe-Se and Ga-Se. Second, selenium-based cathodes are categorized into three types, elemental Se & Se_xS_y composites, organic selenides, and transition metal selenides, with emphasis on multi-electron transfer mechanisms, particularly the six-electron Se⁴⁺/Se^2- redox pathway, which offers a route to overcome capacity limitations. Third, strategies for stabilizing metal anodes, expanding the electrochemical stability window of aqueous electrolytes, and mitigating shuttle effects are critically discussed. Finally, we outline future directions, including interface engineering, artificial intelligence-assisted material screening, and flexible device integration, providing a roadmap toward high-performance AMSeBs for next-generation energy storage applications.