SYNTHESIS AND CHARACTERIZATION OF LAMELLAR MNO2 OBTAINED FROM THERMAL-DECOMPOSITION OF NAMNO4 FOR RECHARGEABLE LITHIUM CELLS

Thermal treatment (600-800 degrees C) in air of solid NaMnO4 induces t he reduction of Mn(VII), leading to the formation of ternary oxides: a lpha-Na0.7MnO2 around 500 degrees C and alpha-NaMnO2 for higher temper atures (800 degrees C). Sulfuric acid treatment of these compounds lea ds to the formation of a lamellar phase with a highly preferred orient ation: MnO1.86. nH(2)O (0.6 less than or equal to n less than or equal to 0.7). The lithium insertion process in this compound has been stud ied in 1 M LiClO4 solution in propylene carbonate. A high depth of dis charge is then achieved, approximate to 0.82 F/mole. Cycling experimen ts carried out in the potential window 4.2-3 V showed that after the 5 th cycle, about 0.62 F . mole(-1) (180 Ah . kg(-1)), i.e., 84% of the initial capacity, is recovered. (C) 1995 Academic Press, Inc.