SYNTHESIS AND CHIMIE DOUCE REACTIONS IN LITHIUM PHYLLOMANGANATE

Lithium phyllomanganate, LixMnO2 . yH(2)O (x = 0.25-0.29, y approximat e to 0.6) with the birnessite structure cannot be obtained directly by oxidation of Mn(OH)(2) in Li-containing medium. It was obtained by a two-step topotactic reaction involving an acidic treatment of sodium p hyllomanganate, followed by ion exchange in LiOH at room temperature. The lamellar lithium manganate is characterized by electron diffractio n, magnetic measurements and thermogravimetry, showing that the struct ure is retained after water loss up to 500 degrees C. The material can not be chemically oxidized by bromine, cerium(IV), or nitryl fluoborat e. However, sodium and lithium phyllomanganates can be delithiated rev ersibly in electrochemical cells at ca. 4 V vs. Li/Li+.