Regulating the Mott-Hubbard Splitting for High-Performance Co-Free Li-Rich Mn-Based Oxide Cathode

Co-free Li-rich Mn-based layered oxides attract great attention as next-generation cathodes due to high specific capacity and low cost. However, their practical applications are hindered by the structural damage and poor cycling stability caused by the irreversible oxygen anion redox (OAR). Herein, a distinct strategy for regulating Mott-Hubbard splitting to address the detrimental issues is proposed. Introducing cations with specific electronic properties into the Li layer and transition metal (TM) layer decreases the Mott-Hubbard splitting energy (U) of TM cations, which promotes the electron removal and optimizes the band structure. This causes the antibonding band (M & horbar;O)* to rise and reduces its overlap with O2p band, thereby simultaneously enhancing the redox activity of TMs and the reversibility of OAR. The specific capacity, rate capability, and capacity retention are all significantly improved (255 mAh g-1 vs 223 mAh g-1 at 0.1C;197 mAh g-1 vs168 mAh g-1 at 1C;147 mAh g-1 vs115 mAh g-1 at 5 C; 93.2% vs 75.5% at 1C after 400 cycles). The oxygen release and voltage decay are also mitigated (92.4% vs 85.6% at 1C after 400 cycles). Moreover, a quantitative method to estimate U value is established for the first time. These findings provide insights into the intrinsic interaction mechanism of anions and cations redox and provide guidance for designing high-performance cathodes.