Evaluation of the Structural Properties and Electrochemical Stability of Crude Red Oil Filtrate-Based Electrolytes Formulated with Sodium Chloride (NaCl) And Potassium Chloride (KCl) Salts for Battery Applications

Abstract

Developing sustainable, non-toxic electrolytes from biomass faces challenges due to low salt dissociation and poor ion mobility in hydrophobic lipid environments. This study presents a comprehensive structural and electrochemical analysis of green liquid-matrix electrolytes composed of red palm oil (RPO) mixed with alkali chloride salts (NaCl or KCl) and distilled water. Using Fourier Transform Infrared (FTIR) spectroscopy, viscometer, Galvanostatic charge discharge (GCD) technique and Electrochemical Impedance Spectroscopy (EIS) technique, we systematically evaluate twelve formulation variations (Samples A to L) to establish relationships between structural configuration and potential battery performance. Attenuated Total Reflection (ATR-FTIR) monitoring revealed a notable coordinate bathochromic shift of the triglyceride ester carbonyl to 1737.92 cm^-1 uniquely in the NaCl system (Sample A), indicating direct cation chelation. Conversely, the KCl system maintained a baseline ester peak at 1743.71 cm^-1, indicating that larger K⁺ ions remain confined within polar aqueous microchannels. Furthermore, critical boundaries were identified between water-overloaded systems displaying extensive hydrogen bonding (3394.83 cm^-1) and oil-encapsulated micellar networks. Spectroscopic evidence also uncovered an identical partial hydrolysis pathway for both salts (1712.85 cm^-1 free fatty acid shoulder), highlighting a key challenge for battery shelf-life. Finally, a comparison of methods showed that classical KBr pelletization causes phase displacement that obscures organic signatures, establishing ATR as the required technique for characterisation. The GCD results, show that redox currents are only set up at the voltage range with an oxidation peak around 0.9 V, demonstrate that the primary cause of the change in the charging voltage is K⁺ insertion (the voltage decreases) and extraction (the voltage increases) into and from the RPO Matrix in the electrolyte. These findings provide a framework for balancing ionic conductivity, voltage stability, and corrosion resistance in biomass-derived liquid batteries.