INVESTIGATIONS OF LITHIUM MANGANESE OXIDE MATERIALS FOR LITHIUM-ION BATTERIES

As candidates for cathode materials in lithium-ion batteries, lithium manganese oxides are attractive and competitive. In this work, the fea sibility of using a novel manganese oxide with a large-tunnel structur e (i.e, todorokite, tunnel size: 3x3) as cathode material in lithium-i on batteries has been explored. It is found that the initial capacity of todorokite material with Mg2+ in the tunnel is 151 mAh g(-1) at a d ischarge current density of 0.1 mA cm(-2). It still has a capacity of 128 mAh g(-1) after four charge-discharge cycles. The effects of diffe rent cations, such as Co2+, Ni2+, Li+ etc., in the todorokite tunnel s tructure, on the electrochemical characteristics of the materials are also studied using slow-rate cyclic voltammetry and electrochemical im pedance spectroscopy (EIS). Finally, the intercalation process of Liin the spinel manganese oxide films has been investigated using the in situ electrochemical quartz crystal microbalance (EQCM) method. It is shown that the intercalation process of Li+ in the films can be divid ed into at least two stages. The results also implied co-intercalation of solvent with Li+ in the second stage.