Quantifying Capacitive and Diffusion-Controlled Charge Storage from 3D Bulk to 2D Layered Halide Perovskite-Based Porous Electrodes for Efficient Supercapacitor Applications

Abstract

Hybrid perovskites have been widely used in solar cells and light-emitting diode applications due to superior optoelectronic properties. However, ion migration in these materials causes photo- and thermal instability. On the other hand, mixed electronic–ionic conduction could be advantageous in electrochemical energy storage applications. We have fabricated porous electrodes from three-dimensional (3D) bulk and 2D layered perovskite single crystals and demonstrated that the ion migration could play a significant role in determining the overall performance of the electrochemical supercapacitor. The areal capacitance (∼58 mF cm –2 ), specific capacitance (∼36.82 F g –1 ), and energy density (∼9 W h kg –1 ) calculated at a current density of 0.6 mA cm –2 are higher in 3D perovskite-based supercapacitors, while the maximum power density (∼400 W kg –1 ) is significantly higher in 2D perovskite-based supercapacitors due to faster intercalation/deintercalation of the electrolyte ions into the porous electrode. We have also estimated the amount of diffusion-controlled charge storage to that of electric double-layer capacitance and surface redox reaction (pseudo-) capacitance from the power law relation in both the samples. The major difference is observed at a low-field regime, where ionic conductivity in 3D bulk perovskites is significantly higher than that in 2D-layered perovskites mainly due to strong electron–ion coupling. Therefore, in 3D perovskite-based supercapacitors, only 2% is diffusion-controlled charge storage compared to 40% in 2D samples at a low-field regime. With the increasing applied voltage, both capacitive and diffusion-controlled charge storage become comparable in both the samples. The 3D sample stability is ∼98%, while the 2D sample stability is almost 100% even after 1000 cycles of operation.