INSERTION OF LITHIUM INTO THE MANGANESE DIOXIDES - PYROLUSITE AND RAMSDELLITE

Insertion of lithium into two MnO2 isomorphs is investigated. Pyrolusi te is the stable modification, having a rutile structure with 1 X 1 st rings of empty channels and Mn-filled octahedral. Ramsdellite is a met astable form with 2 x 1 blocks of these structural elements. Both modi fications take up 1 Li/Mn (100-degrees-C), but for 0 < x < 1/2 in LixM nO2 the lithium insertion potential is higher for ramsdellite. Gamma-M nO2s (EMD, CMD), which are intergrowths of pyrolusite and ramsdellite, can be structurally distinguished on the basis of their lithium inser tion behaviour.