Boosting the ionic transport and structural stability of Zn-doped O3-type NaNi1/3Mn1/3Fe1/3O2 cathode material for half/full sodium-ion batteries

The O3-type NaNi1/3-xMn1/3Fe1/3ZnxO2 (x = 0, 0.005, 0.01) materials were prepared by ball milling-spray drying process. XRD, EDS and XPS results proved that the Zn element was successfully embedded in the lattice and replaced the position of Ni. The sample with Zn doping amount x = 0.005 (NMF-Zn 0.005) exhibited significant improvements in long-term stability and rate capability, the initial capacity was 123.3 mAh g−1 with the capacity retention of 86.53% after 200 cycles at 1 C. Even at higher 5 C, the discharge specific capacity was still up to 102.5 mAh g−1 with the capacity attenuation of 13.96%. Moreover, the full-cell with NMF-Zn 0.005 as cathodes and hard carbon as anodes had been studied, which could deliver excellent cycling of 82.08% over 100 cycles at 1 C. Finally, combining the results of ex-situ XRD and EDS spectrum, the modification mechanism of Zn under high voltage cycling was explained in detail.