ScholarWorks@중앙대학교

초록

Recently, various pre-lithiation strategies have attracted attention as a means to increase the energy density of lithium-ion batteries (LIBs) using high-capacity Si-based anodes. In particular, Li-excess cathode additives are considered to be the most practical method of compensating for the initial Li+ consumption arising from irreversible side reactions. Although Li2NiO2 is attractive owing to its high Li content and redox potential comparable to those of commercial cathodes, its limited irreversible capacity and poor cycling stability hinder its practical implementation. Therefore, microstructural and compositional engineering have been pursued to tune the redox behavior and improve the structural robustness of Li2NiO2 during cycling. This study proposes a combined cationic and anionic substitution strategy to regulate the irreversible capacity and enhance the structural stability of Li2NiO2 as a Li-excess cathode additive. In practice, partially substituting Ni2+ with Cu2+ increases the redox activity via preferential Cu oxidation, which increases the initial charge capacity. Moreover, partial Fe2+ substitution suppresses Fe3+ reduction during discharge, which reduces the initial discharge capacity, thereby increasing the initial irreversible capacity. Furthermore, partial anionic substitution replaces lattice O with more electronegative F–, which strengthens the host lattice and mitigates O evolution at high voltages. Synergistic co-substitution of Cu, Fe, and F increases the initial irreversible capacity of Li2NiO2 above 300 mAh g–1, which effectively compensates for the initial Li+ loss and simultaneously improves the cycling stability. Therefore, this approach can be used to guide the design and development of high-energy LIBs.

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