A Few Probable Electrolyte and Electrode Design Strategies for Multivalent-Ion-Based Rechargeable Batteries

Abstract

Lithium-ion batteries have transformed modern energy storage, but their limitations concerning the materials supply chain and safety risks highlight the need for alternative technologies. This PhD thesis explores multivalent ion-based aqueous rechargeable batteries as a sustainable alternative, focusing primarily on aluminum (Al3+) and magnesium (Mg2+) systems. These multivalent ions are promising due to their high capacities and abundance, but their use in aqueous systems is limited by poor compatibility with electrolytes and sluggish ion transport owing to their stable hydration environment.

The core challenges attempted to be addressed as part of this work are the development of stable and efficient cathode materials that can accommodate large, hydrated multivalent ions without structural degradation. Layered vanadate and Prussian Blue Analogues (PBAs) were studied as promising hosts. Strategies such as electrolyte concentration tuning and salt additives were employed to reduce cathode dissolution and improve cycling stability. In addition to aqueous systems, we investigated a non-aqueous aluminum battery system using AlCl3-Et3NHCl ionic liquid electrolyte, aiming to understand the interfacial behaviour and solid electrolyte interphase (SEI) formation on aluminum.

Detailed electrochemical measurements were combined with structural and compositional analyses, such as ICP-OES and XPS, to understand ion insertion behaviour, degradation pathways, and electrolyte-electrode interactions. The influence of multivalent ion speciation, solvation structure, and electrolyte composition was systematically examined to identify the governing factors behind the capacity fade and redox reversibility across different systems.

Overall, this work contributed to a broader understanding of multivalent-ion storage and highlighted the key considerations in designing materials and electrolytes for future rechargeable battery systems.