Single-phase P2-type layered oxide with Cu-substitution for sodium ion batteries

Abstract The development of high-performance layered oxide cathodes for sodium ion batteries (SIBs) continues to facing be hindered by severe challenges to date. Herein, a single-phase P2-Na0.67Mn0.6Ni0.2Co0.1Cu0.1O2 (NMNCC) comprising multiple-layer-oriented stacked nanoflakes is designed and synthesized via a simple sol–gel method. The large lattice parameters ensure a large three-dimensional frame, which enables the diffusion of sodium ions. Owing to its optimal morphology structure modulation transition metal substitution strategy, the MNCC electrode delivers a reversible capacity of 131.3 mAh g−1 at 0.1 C with retention of 86.7% after 200 cycles. In addition, it provides an initial capacity of 86.7 mAh g−1, and a retention of 80.0% after 500 cycles even at a current density of up to 1 A g−1. The stable single-phase structure and slight volume shrinkage observed after Na+ extraction further delay structural degradation. High Na+ mobility and low Na+ diffusion resistance are also guarantee the excellent rate performance of the NMNCC electrode. Thus, we determine that the NMNCC cathode is significant in the advancement of promising novel layered oxide cathodes.