Exploring Rochelle Salt Aqueous Solutions for Supercapacitors: Transport, Stability, and Performance

This study examines the thermal, transport, and electrochemical properties of Rochelle salt (SPTa, KNaC 4 H 4 O 6 ·4H 2 O) aqueous solutions for energy storage applications. SPTa exhibits eutectic melting (−38 °C), crystallization, density variations (e.g., 0.25 g cm −3 at 25 °C for 2.0 mol dm −3 ), and high ionic conductivity (70 mS cm −1 at 25 °C for 1.0 mol dm −3 ), which increases with temperature and concentration. Ionic transport follows the Arrhenius and Vogel–Fulcher–Tammann models, indicating low activation energies for ion mobility, especially below 8 °C. The Walden plot analysis suggests that most ions remain dissociated in the solution, while the thermodynamic parameters from the activated state of viscosity indicate strong chelation and molecular structuring effects. Cyclic voltammetry of symmetric supercapacitors with activated carbon electrodes in 1.0 mol dm −3 SPTa confirms double‐layer capacitive behavior with a 2.5 V electrochemical window. Galvanostatic charge/discharge tests reveal an energy density of 35 Wh kg −1 , excellent cycling stability (10 000 cycles), and high coulombic efficiency (>97%). Electrolyte evaporation and electrode degradation require further optimization for long‐term stability. These findings highlight SPTa as a cost‐effective and sustainable candidate for electrochemical energy storage.