P3-type layered Na0.26Co1−xMnxO2 cathode induced by Mn doping for high-performance sodium-ion batteries

Layered P-type structures are integral to most competitive cathodes for sodium-ion batteries (SIBs). However, the performance of P2-type cobalt-based layered materials is unsatisfactory owing to a low initial discharge capacity caused by Na deficiency. Here, Mn-doped Na x CoO 2 with a P3 structure is synthesized by using a modified solvent-thermal method with calcination . A structural analysis shows that partial Mn doping can effectively control P3 phase formation and increase d -layer spacing, thereby improving the diffusion of Na + . In addition, enhanced electrochemical performance is observed in optimized P3-type Na 0.26 Co 0.48 Mn 0.52 O 2 (NCMO-1), which exhibits a reversible specific capacity of 64 mAh g −1 at 3 A g −1 and a good capacity retention of 58% after 500 cycles. Furthermore, the Na-ion full cell constructed with an NCMO-1 cathode and a hard carbon anode yields a competitive energy density of 175.9 Wh kg −1 at 0.4 A g −1 with excellent cycle stability. Thus, this work provides a new viewpoint on the development of P3 structural materials with higher electrochemical performance for SIBs.