An overview of the Li(Ni,M)O-2 systems: syntheses, structures and properties

Lithium nickel oxide derivatives are promising positive electrode materials for the next generation of lithium-ion batteries. Partial substitution of certain cations for nickel in this family of oxides significantly modifies their properties and is therefore an attractive route to develop an optimis ed oxide electrode which satisfies the demanding requirements for rechargea ble battery applications. In this paper the interest is focused on the effe ct of cobalt, iron, aluminium and magnesium for a general discussion of the effect of cationic substitution on the properties based on a review of res ults mostly obtained in our laboratories. Although iron substitution does n ot seem interesting for the practical aspect, iron Mossbauer spectroscopy a llows very precise characterisations, interesting to understand the general behaviour of this family of materials. We deal with the optimisation of th e synthesis conditions in order to obtain the most electrochemically active materials. The relations between the nature of the substituting cation, th e presence of foreign cations in the lithium site, the electrochemical beha viour and the redox processes upon electrochemical cycling are discussed in detail. A new view of the relation between this latter point and the catio nic distribution formed during the material synthesis is proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.