A study on the next-generation secondary batteries incorporating vanadium oxide-based cathodes

Abstract

Metal battery systems have emerged as promising candidates for next-generation energy storage due to their high capacity and low cost. Among them, high-power and energy lithium metal batteries (LMBs) and high- energy and safe aqueous zinc metal batteries (AZMBs) are considered two of the most promising and complementary systems for modern applications, including electric vehicles (EVs), advanced air mobility (AAM), and grid-scale energy storage systems (ESSs). However, the practical deployment of these systems remains hindered by electrode structural degradation and interfacial instability. To address these challenges, this dissertation presents system-level design strategies with in-depth degradation mechanism studies for both LMBs and AZMBs, focused on the use of vanadium oxide (VO) cathodes. VO is particularly attractive due to its high theoretical capacity, structural versatility, and cost-effectiveness, making it a strong candidate for achieving high-performance metal battery systems. For the LMB system, configuration of a low-voltage, high-capacity structural modified VO cathode with a low-concentration ether-based electrolyte (1 M LiFSI in DME, denoted E-LCE) is suggested. The nanoplate- stacked VO structure facilitates short Li+ diffusion pathways, while the E-LCE enables the formation of a thin, ionically conductive sulfur-rich cathode–electrolyte interphase (CEI) and a robust, elastic solid electrolyte interphase (SEI) on the lithium metal anode. This synergistic design delivers stable cycling at high current densities (5 C, full cell) and induces a favorable phase transition from α– to γ′– V2O5, enhancing both power and energy densities, along with long-term stability. Simultaneously, degradation mechanisms in VO-based AZMBs are elucidated, with particular focus on vanadium ion cross-talk as a critical but underexplored degradation pathway. Using a V2O5·nH2O cathode and 2 M ZnSO4 electrolyte, a vanadium shuttling is identified, in which dissolved vanadium species undergo spontaneous reduction at the zinc anode, leading to interfacial instability, open-circuit voltage (OCV) drift, and capacity fading, especially under moderate current densities (<500 mA g−1). From these findings, holistic strategies to suppress shuttling are also proposed. This dissertation highlights the importance of physicochemical insights into both material structures and interfacial reactions for the rational design of high performance next-generation metal battery systems.