Synthesis and electrochemical characteristics of Ni1-xMn2O4 cathodes for rechargeable lithium batteries

Two Ni-Mn spinels were synthesized at low (sample A) and high (sample B) temperatures, using the sol-gel and precipitation method; respectively. Both spinels were assessed for use in rechargeable lithium cells. The sol-gel spinel exhibits a single reduction step centered about 2.9 V. with a large discharge capacity (144 Ah kg(-1) at 0.05 mA cm(-2)). This spinel also exhibits excellent reaction kinetics and fairly good cyclability. By contrast, the high temperature spinel delivers a low capacity (4 Ah kg (2)), similar to that reported for Mn3O4. Chemical analyses and x-ray powder diffraction data revealed sample A to be a Ni cation deficient. highly disordered spinel with a high surface area and a significant Mn4+ content. Unlike sample A, sample B is a highly crystalline, almost stoichiometric spinel of low surface area. These features are consistent with the better electrochemical properties of the sol-gel spinel.