Pseudocapacitive charge storage in layered oxides SrLaFe1−xCoxO4−δ (x = 0–1)

Abstract

Pseudocapacitive energy storage has been demonstrated for three materials belonging to a family of layered oxides. This work is the first report on the observation of charge-storage properties in this family of materials that feature 2-dimensional layers, consisting of MO6 units (M = transition metal). The spaces between layers are occupied by alkaline-earth or rare-earth metals. Systematic trends have been demonstrated, where the charge-storage properties are enhanced as a function of Co-concentration, structural distortion and oxygen-deficiency in SrLaFe1−xCoxO4−δ. Symmetric pseudocapacitor cells based on these materials show substantial specific capacitance, energy density and power density. They are also remarkably stable and retain their charge storage capacity even after 1000 cycles of charge-discharge. The observation of pseudocapacitive charge-storage properties in these materials indicates the potential of this class of layered oxides for utilization in energy storage.