Electrochemical behavior of lithium imide/cyclic ether electrolytes for 4 V lithium metal rechargeable batteries

To develop organic electrolytes for 4 V lithium metal rechargeable batterie s, LiN(SO2CF3)(2) electrolytes with five-, six-, and seven-membered cyclic ether solvents were characterized. Among these examined electrolytes, LiN(S O2CF3)(2)/tetrahydropyran (THP) electrolyte was found to possess the most a dvantages, such as high cycling efficiency, good oxidation stability, and h igh boiling point. Furthermore, lithium cycling efficiency and conductivity were improved by mixing 50% ethylene carbonate (EC) in 1 mol/dm(3) LiN(SO2 CF3)(2)/THP electrolyte. By using LiN(SO2C2F5)(2) solute as an alternative to LiN(SO2CF3)(2) in EC + THP(1:1) electrolyte, corrosion of the aluminum c urrent collector was inhibited and therefore, excellent cycling performance of a Li/LiMn2O4 coin cell was realized. It was also found that lithium cyc ling efficiency increased with decreasing deposition current density or inc reasing dissolution current density. Especially at deposition/dissolution c urrent densities of 0.2/0.6 mA/cm(2), the observed lithium cycling efficien cy in 1 mol/dm(3) LiN(SO2C2F5)(2)/EC + THP (1:1) electrolyte was above 99%. Thermal tests further disclosed that this mixed electrolyte has good therm al stability even in the presence of lithium metal or cathode materials. (C ) 1999 The Electrochemical Society. S0013-4651(99)03-060-8. All rights rese rved.