Discerning the Role of A‐Site Cation on the Efficiency and Stability of the Halide Perovskite Solid‐State Supercapacitor

Abstract

Hybrid halide perovskites have emerged promising energy‐storage materials due to their high ionic and electronic conductivity. They can be used in rechargeable batteries, photo‐rechargeable supercapacitors, and other ion capacitors. In this article, the role of A‐site cations in halide perovskites on the charge‐storage mechanism in supercapacitors is verified. Three different types of halide perovskites of APbI3 (where A = MA, Cs, or FA) are investigated to unveil the role of A‐site cation in energy‐storage application. Specific capacitance increases with the increasing surface area from CsPbI3 to FAPbI3. From the three‐electrode electrochemical measurement, it is observed that the FAPbI3 has the highest specific capacitance while CsPbI3 is the lowest among all. Herein, solid‐state asymmetric supercapacitors are further fabricated using quasi‐solid‐state gel electrolyte. The specific areal capacitance is achieved over 72 mF cm−2, which is at least six times higher than the CsPbI3‐based devices due to high ionic mobility. The stability and structural charge are further investigated due to charge storage in FAPbI3 electrode by ex situ X‐ray diffraction measurement. As prepared FAPbI3 powder is in δ phase, however during charging it changes to α‐phase and becomes stable. Significant phase changes are not observed for MAPbI3 and CsPbI3 electrodes either charging or discharging cycles.