Abstract: Mn-based layered oxides as one of the most promising and cost-effective cathode candidates for sodium-ion batteries still face great challenge to achieve high capacity with long cycle life under high-rate current simultaneously. In this work, we propose an effective strategy by a combination of liquid N₂ quenching and aliovalent doping to get new layered cathode materials. As evidenced by in-situ synchrotron X-ray diffraction, time-of-flight powder neutron diffraction and solid-state ²³Na nuclear magnetic resonance techniques, the proposed synthesis methods allow tuning the transition metal ions vacancies and enhance Mn⁴⁺/Mn³⁺ redox center of P2-type Mn-based materials. Our results demonstrate that such an optimized structure significantly enhances the deliverable capacity, Na⁺ mobility and electronic conductivity of the materials. Furthermore, the effects of aliovalent doping elements and different cooling approaches on the long-range structure, local environment and electrochemical performance are comprehensively studied by comparing a wide range of doped Na_0.67M_xMn_1-xO₂ (M = Li, Mg, Al, Fe) materials. The optimized Na_0.67Al_0.1Fe_0.05Mn_0.85O₂ material exhibits a remarkably high initial capacity of 202 mAh g⁻¹ among ever reported P2-type layered oxides within 2–4 V, a stable capacity retention of 81% after 600 cycles and outstanding rate capability of the specific capacity up to 122 mAh g⁻¹ at 1200 mA g⁻¹.

Source:https://pcss.xmu.edu.cn/en/info/1095/1959.htm

Full-Link:https://www.sciencedirect.com/science/article/pii/S2211285520305747