Starch Gel Electrolyte and its Interaction with Trivalent Aluminum for Aqueous Aluminum‐Ion Batteries: Enhanced Low Temperature Electrochemical Performance

This study explores trivalent Al interaction with aqueous starch gel in the presence of two different anions through salting effect. Salting-out nature of Al₂(SO₄)₃·18H₂O with starch gel causes precipitation of starch; this happens due to competitive anion-water complex formation over starch-water interaction, thereby reducing polymer solubility. Salting-in effect of AlCl₃ with starch gel happens through Al³⁺ cation interaction with hydroxyl group of starch and increases polymer solubility, making gel electrolyte viable for battery applications. Prepared gel electrolyte exhibits ionic conductivity of 1.59 mS cm^-1 and a high t_Al ³⁺ value of 0.77. The gel electrolyte's performance is studied using two different cathodes, the Al|MoO₃ cell employing starch gel electrolyte achieves discharge capacity of 193 mA h g^-1 and Al|MnO₂ cell achieves discharge capacity of 140 mA h g^-1 @0.1 A g^-1 for first cycle. The diffusion coefficient of both cells using starch gel electrolyte is calculated and found to be 2.1 × 10^-11 cm² s^-1 for Al|MoO₃ and 3.1 × 10^-11 cm² s^-1 for Al|MnO₂ cells. The Al|MoO₃ cell at lower temperature shows improved electrochemical performance with a specific capacity retention of ≈87.8% over 90 cycles. This kind of aqueous gel electrolyte operating at low temperature broadens the application for next generation sustainable batteries.