Fabrication, electrochemical performance, and in situ infrared thermal imaging of Na0.67(Mn0.5Fe0.5)1-xCuxO2 battery cells

Na-0.67(Mn0.5Fe0.5)(1-x)CuxO2 powders (where x = 0, 0.05, 0.1, 0.2, and 0.3) were produced by quenching at 900 degrees C, and the structural features of the powders were studied in detail. It was found that the undoped and Cu-substituted for (x <= 0.2) powders had no impurity phases in the structure. Furthermore, the lattice volume calculated by the GSAS-II open-source program decreased with increasing Cu content, and it is suggested that Cu ions have a 3+ valence state in the samples. The cycling voltammetry of the cells is very similar to each other. The constant current charge/discharge cycling measurements were performed for up to 100 cycles, and the best performance was observed for x = 0.2 Cu substitution in Na-0.67(Mn0.5Fe0.5)(1-x)CuxO2. The best capacity value was obtained as 182.3 mAh/g at the C/10 rate for x = 0.2 Cu substitution. The cycling measurements at 50 degrees C exhibit worse capacity fade when compared to the measurements performed under ambient conditions. The in situ infrared thermal imaging measurements for the cell that had the highest performance in this study were performed for a constant voltage of 4.3 V for charging and 1.5 V for discharging of the cell. The ohmic heat was calculated from chronoamperometry measurements, and the heat generation was fitted with the quadratic term in the system.

Automated summary

The study found that Cu substitution had no impurity phases in the structural of Na-0.67(Mn0.5Fe0.5)(1-x)CuxO2 powders, with decrease in lattice volume as Cu content increased, implying Cu ions were in a +3 valence state. Cycling voltammetry showed similar performance across different powders, with the best capacity observed for x = 0.2 Cu substitution.