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; respectiv ely. 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 goo d 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 N i 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 f eatures are consistent with the better electrochemical properties of t he sol-gel spinel.