P2-type Na0.67Ni0.33Mn0.67O2 cathode materials that show high discharge voltage and theoretical specific capacity have attracted extensive research, although the problem of rapid capacity decay under high voltage needs to be overcome. Here, a series of Na0.67Ni0.33–x Cu x Mn0.67–y Ti y O2 cathode materials were synthesized that had good cyclic stability and rate performance at a high voltage of 4.5 V. The combined analyses of Rietveld refinement X-ray diffractometer (XRD), X-ray photoelectron spectroscope (XPS), Raman, and transmission electron microscope (TEM) showed that Ti4+ and Cu2+ had been successfully incorporated into the material crystal lattice. The Ti/Cu dual-doping materials operated at a high mid-voltage of ∼3.2 V vs Na/Na+ and exhibited a reversible capacity of 93 mA·h·g–1 at 5C. The voltage step of Ti4+/Cu2+-doped materials at ∼4.2 V was clearly suppressed with increased Cu content, and NNMT-0.14Cu materials exhibited an initial discharge capacity of 153.2 mA·h·g–1 owing to Cu contributing to reversible capacity based on Cu2+/Cu3+. Galvanostatic intermittent titration technology measurements showed that’ the Na+ mobility of NNMT-0.14Cu materials was improved.

Sodium-ion batteries (SIBs) are expected to be a great substitute for lithium ion batteries. Although there are many difficulties to overcome, SIBs have become one of the most important research areas for large-scale energy storage equipment. The spherical particles are conducive to the contact between the cathode material and the electrolyte, which could increase the electrochemical reaction area, and improve the deintercalation rate of sodium ions during charging and discharging. In this paper, a precipitation method was used to prepare spherical MnCO3 material as template and raw material. After all the raw materials were weighed with the molar ratios of Na0.67Mn0.67–0.75x Ni0.33Al x O2, a series of hollow micro-spherical sodium-ion cathode materials were synthesized by the conventional high-temperature solid-state method. The effects of Al-doped on the structure and electrochemical performance of Na0.67Ni0.33Mn0.67O2 was studied, and it was founded that the samples doped with Al had smaller particle size than that without Al. The electrochemical tests showed that Na0.67Mn0.595Ni0.33Al0.1O2 (x = 0.1) exhibite superior high-rate capabilities and cyclic stability. And the hollow microsphere structure has a higher capacity, the first discharge capacity at 0.1C reach 128 mAh g−1.