Redox Engineering of Fe-Rich Disordered Rock-Salt Li-Ion Cathode Materials

Abstract

The pursuit of high-performance and cost-effective Li-ion batteries emphasizes the need for cathode materials composed of abundant elements, such as Fe. Disordered rock-salt (DRX) cathode materials, known for their high compositional flexibility, offer a unique opportunity in this regard. However, Fe-rich DRX (Fe-DRX) cathodes, potentially the most cost-effective among all DRXs, have seen limited research interest due to their comparatively restrained performance. This limitation stems from the inaccessibility of the Fe3+/Fe4+ redox in the DRX structure, prompting the need for redox engineering to enable Fe-DRXs with readily utilizable redox mechanisms. In this work, utilizing both experiments and theoretical study, reversible Fe2+/Fe3+ redox in an Fe2+-based DRX cathode is demonstrated. This design minimizes the reliance on O redox, resulting in a high capacity (≈290 mAh g−1) and energy density (≈700 Wh kg−1), as opposed to an Fe3+-based DRX operating on the limited Fe3+/Fe4+ redox and extensive O redox upon cycling. Overall, the study introduces a novel approach to redox engineering to develop low-cost, high-performing Fe-rich cathode materials.