Unveiling the electrochemical supercapacitor dynamics in lead-free Cs3Bi2X9 (Cl/Br) perovskite: Impact of halogen alteration

Abstract

The research community has recently focused especially on all inorganic lead-free perovskites as possible materials for energy storage in electrochemical systems. Here, a low-cost solution-based facile synthesis approach is adopted to prepare Cs₃Bi₂(Br/Cl)₉ perovskite for energy storage applications. These perovskites are crystallized in hexagonal phase with P3m1 space group, as confirmed by XRD analysis. The pseudo-capacitance arises in the Cs₃Bi₂(Br/Cl)₉ perovskites due to the redox transition between Bi³⁺ and Bi⁵⁺ and OH^‐− ion intercalation/de-intercalation through the electrode material. The specific capacitances of 1617 F g⁻¹ and 613 F g⁻¹ at a scan rate of 2 mV s⁻¹ have been delivered by Cs₃Bi₂Cl₉ and Cs₃Bi₂Br₉ perovskites, respectively. We have also fabricated an asymmetric device using optimized perovskite with the configuration of Cs₃Bi₂Cl₉//PVA-KOH gel/activated carbon (AC), which exhibits an energy density of 27 Whkg⁻¹ and a power density of 689 W kg⁻¹ at a current density of 1 Ag⁻¹ with a capacitive retention of ∼80 % even after 5000 charging/discharging cycles. In our opinion, such promising findings are poised to unlock new horizons for the forthcoming generation in the development of lead-free perovskite-based, non-toxic, sustainable energy storage systems.