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 feasibility of using a novel manganese oxide with a large-tunnel structure (i.e. todorokite, tunnel size: 3x3) as cathode material in lithium-ion 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 discharge 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 different cations, such as Co2+, Ni2+, Li+ etc., in the todorokite tunnel structure, on the electrochemical characteristics of the materials are also studied using slow-rate cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Finally, the intercalation process of Li+ in 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 divided into at least two stages. The results also implied co-intercalation of solvent with Li+ in the second stage.