Characterization of layered lithium nickel manganese oxides synthesized by a novel oxidative coprecipitation method and their electrochemical performance as lithium insertion electrode materials

Lithium nickel manganese oxides were prepared via a solution technique in which mixed nickel manganese hydroxide precursors were synthesised by oxidative coprecipitation and then calcined in the presence of LiOH leading to crystalline products with a partially disordered layered-type structure. The electrochemical performance of these materials as positive electrodes in lithium-ion batteries was evaluated as a function of the calcination temperature and manganese content. At 700 C, a sufficiently high degree of crystallinity was achieved, having a strong influence on the cycling stability of these materials. With increasing manganese content, the specific charge increased to about 170 mAh/g for materials with a Ni:Mn ratio of about 1:1. Ex situ magnetic susceptibility measurements proved that during lithium deinsertion, the trivalent manganese is preferentially oxidised, and seems to be the more reactive redox centre in these oxides. 49 refs.