Because of their high reversible capacity and wide operation voltage window, P2-type layered transition metal oxides are considered as one type of potential cathode candidate for sodium-ion batteries. However, they still suffer from low kinetics, phase degeneration, and ambiguous mechanism of Na + diffusion. Here, we synthesized a P2-type Na0.6Li0.07Mn0.66Co0.17Ni0.17O2 with a high Na+ diffusion performance by sintering a nanoplate-structural precursor with alkali metal salt and proposed a possible mechanism for improving Na + diffusion. The as-prepared P2-type layered oxide presents a quasi-hexagon shape and demonstrates a discharge capacity of 87 mAh g–1 at a current density of 875 mA g–1 (5 C rate), twice that of the sample synthesized from a non-nanoplate particle precursor. Rietveld refinement and results of X-ray photoelectron spectroscopy reveal the probable mechanism that the expanded interplanar spacing along the c-axis orientation would facilitate Na + diffusion during Na + intercalation/deintercalation processes, and the expanded interplanar spacing may arise from a high oxidation state of transition metal ions.

α-MnO 2 nanorods with large 2 × 2 tunnels are often selected as storage materials in aqueous zinc-ion batteries due to their high theoretical capacity, environmental friendliness, and low cost. The electrochemical performance is strongly associated with their particle size; however, many techniques for controlling size include undesirable contents, such as carbon-containing components, which reduce the overall energy density of the electrodes. In this paper, Ni(II) ions are introduced to hinder the spatial growth during the preparation of α-MnO 2 , hence tuning the aspect ratio and enhancing the zinc-ion storage performance. The confinedspace effect is employed by controlling the size of α-MnO 2 particles, in which the initial long rods at the micron scale have become tiny α-MnO 2 nanorods. Smaller particle size electrode materials offer shorter ion diffusion paths, greater electron transport efficiency, and more sufficient solid−liquid interface space due to the small size effect, which also determines the capacity and lifetime of batteries. At the same time, Ni(II) addition selectively hinders the growth direction (001) plane, which effectively shrinks Zn(II) and electron transport paths. As a result, the prepared α-MnO 2 nanorods obtained a high capacity (272 mA h g −1 at 50 mA g −1 ) and stable cycling stability (70% capacity retention after 500 cycles at 500 mA g −1 ). These results demonstrate that the introduction of uncoordinated ions is an effective way to control the metal oxide size and provide a direction in the development of electrode materials for secondary batteries.