Charge-discharge properties of composites of LiMn2O4 and polypyrrole as positive electrode materials for 4 V class of rechargeable Li batteries

Charge-discharge properties of chemically prepared composites of polypyrrole and spinel LiMn2O4 (LiMn2O4/PPy) have been studied at potentials ranging between 4.3 and 3.2 V vs. Li/Li+. Pellets of LiMn2O4/PPy were successfully prepared by pressing the composite powder without using any binder. Charge-discharge tests of the LiMn2O4/PPy pellet gave a potential plateau around 4 V, indicating that polypyrrole works well as a conducting matrix for the redox reaction of LiMn2O4 reversible arrow Li1-xMn2O4 + xLi(+) + xe(-). The polypyrrole behaved also like a capacitor and contributed to the capacity density of the LiMn2O4/PPy composite: The effects of charge-discharge current densities, the amount of LiMn2O4 in the composite, and cycle tests of charge-discharge reactions were investigated. Elemental analyses of the composites before and after discharging revealed that Li+ and ClO4 were involved in the charge-discharge reactions of LiMn2O4 and polypyrrole, respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.