Charge Storage Mechanism via Vacancy-Mediated Anion Intercalation in a Two-Dimensional Cs₂PbI₂Cl₂ Ruddlesden–Popper Perovskite

This research delves into the exploration of the electrochemical charge storage mechanism and supercapacitive behavior exhibited by 2D Ruddlesden–Popper (RP) halide perovskites. The mechanochemically synthesized Cs 2 PbI 2 Cl 2 perovskite, characterized by its tetragonal phase and I 4/ mmm space group symmetry, has been investigated as a promising electrode material for energy storage applications. In our investigation, we probed the charge storage mechanism within Cs 2 PbI 2 Cl 2 by employing a 1 M KOH aqueous electrolyte in a three-electrode setup. This system operated within the potential window of 0.0–0.6 V vs Ag/AgCl. The pseudocapacitive behavior of the Cs 2 PbI 2 Cl 2 perovskite arises from anion (OH – ion) intercalation from the electrolyte into vacant sites within the electrode material, accompanied by redox transformations of Pb ions. Specifically, the Cs 2 PbI 2 Cl 2 perovskite exhibits a specific capacitance of 2017 F g –1 at a scan rate of 2 mV s –1 . Furthermore, we fabricated an asymmetric supercapacitor device with the configuration of a Cs 2 PbI 2 Cl 2 /PVA-KOH gel/activated carbon. This device delivers an energy density of 67 Wh kg –1 and a power density of 794 W kg –1 at a current density of 1 A g –1, with ∼75% capacitive retention after 8000 charge–discharge cycles. These compelling electrochemical findings strongly support the feasibility of utilizing a low-dimensional Cs 2 PbI 2 Cl 2 perovskite as an electrode material for advanced supercapacitor electrodes.