STUDIES ON ORGANIC ELECTROLYTES FOR BATTERIES

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Several combinations of organic solvents and lithium (Li) salts were examined as the electrolytes of ambient temperature Li batteries. Propylene carbonate (PC), sulfolane (SL), and dimethyl sulfoxide (DMSO) were used as the high permittivity solvents, and 1,2-dimethoxyethane (DME), tetrahydrofuran (THF) and the like were used as the low viscosity solvents. The conductivity of Li salts was improved by blending the solvents, ie. maximum conductivities were obtained in the mixed solvent systems. The <LiPF_6> solutions had much higher conductance than those of <LiClO_4> or <LiBF_4> , especially in the mixed solvent systems. The charge-discharge cycling efficiency of the Li negative electrode was markedly dependent not only on the solvent composition but the electrolytic salt. Higher efficiencies were observed in the electrolytes with higher conductivities. The highest efficiency on the Ni substrate was obtained in <LiPF_6> /DMSO(or SL)-DME. High rechargeability of Li was also expected in the solution containing <LiClO_4> or <LiBF_4> when Al was used as the substrate. The addition of crown ethers was effective for the improvements in the electrolytic conductivity of the PC-based solution and the recharge-ability of the Li/ <TiS_2> cell.