Characteristics, materials, and performance of Ru-containing oxide cathode materials for rechargeable batteries

Li-rich Mn-based cathode materials have attracted extensive attention due to their remarkable energy density contributed by additional anionic redox. However, they always suffer from some undesired problems impeding their further commercialization such as irreversible oxygen loss, transition metal migration, sluggish kinetics and so on. Fortunately, the above issues can be relieved effectively when 3d metal Mn is replaced by 4d metal Ru. We focus on the recent progress of Ru-containing cathode materials and make a detailed summary in this review. At first, we attempt to combine and elucidate the relationship between oxygen and Ru redox. Subsequently, the up-to-date materials of Ru-based cathode materials for Li⁺/Na⁺ batteries are concluded systematically. Afterward, the effects of Ru are discussed in depth including enhancing the reversibility of anionic redox and structural stability, modulating the ratio between cationic and anionic redox, improving the kinetics of Li⁺/Na⁺, inhibiting the transition metal migration and so on. More importantly, the future designs of Ru-containing cathode materials are also proposed enlighteningly. We hope this review could offer some new perspectives to comprehend the layered oxides involving anionic redox and provide useful guidelines to achieve better Li⁺/Na⁺ rechargeable batteries.