Lithium superacid salts for secondary lithium batteries

Abstract

Three newly prepared lithium superacid ‡ ‡ Superacid is defined as any Bronsted acid which is stronger than 100% sulfuric acid. salts of the type C n F 2 n + 1 SO 3 Li (where n is 4, 8 and 10) and CF 3SO 3Li and (CF 3SO 2) 2NLi were used as salts in polyethylene oxide (PEO) electrolytes. Our conductivity data shows that among the salts investigated PEO electrolytes containing (CF 3SO 2) 2 NLi gave the highest conductivity followed by C 4F 9SO 3Li and C 3F 17SO 3Li. PEO electrolytes containing C 10F 21SO 3Li and CF 3SO 3Li showed a lower conductivity at room temperature than the rest. Experimental LiTiS 2 polymer cells containing either PEO-C 4F 9SO 3Li or PEO-(CF 3SO 2) 2NLi as electrolyte were fabricated and tested for cycle life performance. No significant loss in capacity was observed even after 50 to 100 cycles.