Tailoring LaCoO₃ Perovskite Oxides via Ce Substitution and Nanofiber Architecture for Enhanced Electrochemical Storage Performance

Perovskite oxides offer great potential for supercapacitors thanks to their redox activity and structural tunability. However, their practical application is hindered by issues such as phase stability and low conductivity. Herein, La1–xCexCoO3−δ (x = 0, 0.05, 0.1, 0.15, and 0.2) perovskite nanofibers were synthesized via the electrospinning–calcination method. As Ce substitution increased, the perovskite transitioned from a single hexagonal phase to a dual-phase (hexagonal and cubic) structure. Given that the as-constructed cubic phase and nanofiber morphology are more thermodynamically stable than the hexagonal phase in Co-based perovskites, Ce substitution was found to enhance the overall structural stability. Moreover, Ce substitution affected the oxygen vacancy concentration, with the highest concentration observed at x = 0.1, resulting in an optimal value of 267.9 F g–1 at a current density of 1 A g–1. This was attributed to its relatively intact nanofiber structure providing abundant active sites and the lowest internal resistance. A supercapacitor device using La0.9Ce0.1CoO3@Ni-foam serving as the positive electrode and activated carbon (AC)@Ni-foam as the negative electrode achieved an energy density of 11.4 W h·kg–1 at a power density of 775.1 W·kg–1. After 5000 charge–discharge cycles at 1 A g–1, the device retained 90.42% of its initial capacitance. These results demonstrate that Ce substitution significantly improves the electrochemical and cycling performance of LaCoO3, offering a viable strategy for designing stable and high-performance supercapacitor electrodes.