Effect of fumed silica concentration and separator type on the electrochemical performance of gel electrolyte in the rechargeable hybrid aqueous battery

Abstract

The rechargeable hybrid aqueous battery (ReHAB) has been developed as one of the commercial substitutions for the lead-acid battery thanks to its utilization of environmentally benign materials (hence lower toxicity) and higher energy storage capability. The system consists of a LiMn2O4 composite cathode and a zinc metal anode, separated by a porous separator containing a mixed aqueous solution of Li2SO4 and ZnSO4. Fumed silica, a gelling agent, is dispersed in the aqueous electrolyte, and physical and electrochemical characteristics of the newly formed gel electrolytes are investigated. Although the presence of Li2SO4 enhances the gel formation and ZnSO4 promotes the reverse, the gel strength and gelling time depend on the molar ratio between ZnSO4 and Li2SO4. Incorporation of fumed silica into the liquid electrolyte enhances the charge-discharge and the cyclability significantly. After 300 charge-discharge cycles at 4 C, discharge capacity retention of the cells with the gel electrolyte is over 10% higher than that of cells with the liquid electrolyte. Moreover, the absorbed glass mat separator (AGM) provides better stability at high C-rates than filter paper separator, thanks to the superior water retention ability of the AGM.