We demonstrated experimental and theoretical approaches to obtain a full picture of the mixed-anion effects for LiNi0.5Mn1.5O4−xFx cathode materials. The fluorine anion reduced the activation barrier for lithium (Li)-ion hopping along the most energetically preferable 8a-16c-8a route, enhancing the C-rate capability. Simultaneously, the coordination bond of the linear F−–Mn3+–F− (Mn@2F diagonal) arrangement increased the oxidation potential to 5.1 V (vs Li+/Li). This hampered full extraction of Li+ from the spinel lattice, which was triggered by the oxidation of Mn3+ below the cutoff voltage (3.5–4.8 V (vs Li+/Li)), leading to a capacity loss.
- Dae-wook Kim
- Hiromasa Shiiba
- Katsuya Teshima
