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

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-09, Vol.20 (37), p.e2402245-n/a
• Main Authors: Ramakrishnan, Saraswathi, Sasirajan Little Flower, Sajan Raj, Hanamantrao, Desai Prashant, Kasiviswanathan, Kavibharathy, Sesu, Divya Catherin, Muthu, Kesavan, Elumalai, Varathan, Vediappan, Kumaran
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum chloride; Aluminum sulfate; Al‐ion batteries; Anions; biopolymeric starch; Cationic polymerization; Complex formation; Diffusion coefficient; Discharge; Electrochemical analysis; Electrolytes; Electrolytic cells; gel‐electrolyte; Hydroxyl groups; Ion currents; Low temperature; Manganese dioxide; Polymer solubility; Polymers; Salting; salting effect; Solubility
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202402245

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 tAl3+ 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. The salting‐out and salting‐in effects of aluminum salt with starch gel occurs in the presence of SO42− and Cl− anions. Salting‐in effect on starch gel increases polymer solubility and happens through Al3+ cation interaction with hydroxyl group of the starch and renders the gel suitable for use as an electrolyte in battery applications.