Construction of environmental-stable and high-rate layered oxide cathodes for sodium-ion batteries

Layered manganese oxides, as dynamic cathodes for high energy density sodium ion batteries (SIBs), still suffer from not only rapid capacity decay, but also irreversible phase transition, unsatisfactory rate performance and air instability. In this work, Li/Ni/Ti co-doping Na0.72Li0.16Ni0.12Ti0.1Mn0.62O2 (NLNTMO) cathode was successfully synthesized and it revealed that the structure design not only effectively inhibits Jahn-Teller distortion to improve cycling stability but also enhances its resistance to air and moisture degradation. Besides, density functional theory (DFT) calculations reveal that Ti can slightly adjust the energy level of isolated O 2p and Mn 3d orbitals. The in-situ X-ray diffraction (XRD) analysis reveals the inhibition of the repulsive phase transition from P2–OP4/O2 and the occurrence of a solid solution reaction instead. As a result, NLNTMO cathode presents a high specific capacity of 198.6 mAh g−1 at 0.2C, 70 mAh g−1 at 20C (4 A g−1) and a high capacity retention of 80 % in 2.0–4.4 V after 200 cycles at 1C.