Tailoring the electronic structure of O3-type layered oxide cathodes to achieve long-cycle life and high-rate performance sodium-ion batteries

Despite its great potential for practical application in sodium-ion batteries (SIBs), the O3-type layered oxide cathode is still hindered by rapid capacity decay and poor cycle life, which is primarily due to irreversible phase transitions caused by the Jahn-Teller effect of Mn3+ ions. Here, we design an O3-Na0.98Li0.03Co0.05Ni0.22Fe0.2Mn0.5O2 (LCNFM) oxide cathode to effectively suppress the irreversible phase transition by tailoring its electronic structure. This approach activates more transition metal ions (Ni2+ and Fe3+) to participate in the redox reactions above 2.5 V, and suppresses the redox reactivity of Mn3+/4+ below 2.5 V. Additionally, cobalt ions, with their excellent electronic conductivity, significantly improve the dynamic performance. Importantly, the fundamental mechanism is fully understood through systematic in situ/ex situ characterization techniques and density functional theory computations. Consequently, the as-prepared LCNFM electrode, with high structural stability, exhibits excellent cycling performance (87.2% capacity retention after 1000 cycles at 5C within 2.0-4.0 V) and high rate capacity (112.1 mA h g-1 at 0.1C compared to 100 mA h g-1 at 1C). This work provides a new perspective for designing high-performance O3-type layered cathodes and offers a practical strategy to boost the commercial application for SIBs.