Strategies to Mitigate First-Cycle Irreversibility in Alkali-Ion Batteries

The increasing demand for higher energy density and improved sustainability is driving the development of advanced alkali-ion batteries (AIBs), encompassing both lithium-ion and sodium-ion technologies. Despite significant progress in electrode materials, interfacial phenomena occurring during the initial electrochemical cycles remain a major limitation for practical applications. In particular, the irreversible capacity loss associated with solid electrolyte interphase (SEI) formation at the negative electrode leads to depletion of cyclable alkali ions, ultimately reducing energy density and long-term performance. Sacrificial alkali-containing salts were originally proposed as a practical strategy to compensate for this initial charge irreversibility. More recently, organic self-sacrificial lithium salts have been investigated as prelithiation agents capable of releasing additional Li+ upon electrochemical activation. Upon oxidation, these species generate ideally gaseous or soluble by-products that do not compromise electrode integrity. In parallel, electrolyte additives have been widely explored to regulate interfacial reactions, promote controlled SEI/CEI formation, and enhance cycling stability. The combination of electrode-level sacrificial strategies and electrolyte engineering represents a promising yet relatively underexplored integrated approach. In this work, we investigate an integrated strategy combining sacrificial salts incorporated within the positive electrode and selected electrolyte additives in representative alkali-ion battery systems. By systematically varying additive content and formulation parameters, we assess their impact on first-cycle efficiency and interfacial behavior. Preliminary electrochemical results indicate that the incorporation of sacrificial salts effectively mitigates initial irreversible capacity losses, while the synergistic use of electrolyte additives contributes to improved interfacial stabilization. The combined approach highlights a versatile pathway toward enhanced initial Coulombic efficiency and improved performance in next-generation alkali-ion batteries.