High Na-content P2 and P2-O3 layered oxide cathodes for high performance Na-ion batteries

P2-NaxTMO2, (x ≤0.67, TM-transition metal) oxides are promising cathode materials for Na-ion batteries, however they suffer from Na+-vacancy ordering and huge structural transformations (P2→O2→OP4). In contrast, high Na content in P2-type cathodes enables high structural stability and promotes active elements to their lower oxidation state and thereby achieving high capacity and cycling stability. Herein, light-weight elements boron and lithium doped in P2-type Na0.67Ni0.33Mn0.67O2 using cationic potential approach, aiming to improve the Na content. Li-B doped Na0.8Ni0.3Mn0.6Li0.05B0.05O2 delivers a capacity of 85 mAh/g and excellent capacity retention (88 % after 500 cycles). The effects of Li-B doping in P2-type Na0.67Ni0.33Mn0.67O2 are systematically investigated.