Preparation of an Li 0.7 Ni 0.8 Co 0.2 O 2 Electrode Material From a New Li–Co–Ni Mixed‐Citrate Precursor

A new chemical route to prepare the mixed oxide Li 0.7 Ni 0.8 Co 0.2 O 2 , which is a member of the well‐known Li‐Ni‐Co‐O family that is of interest as an electrode material for rechargeable lithium batteries, from a mixed citrate is reported. In a first step the new citrate (NH 4 ) 3 LiNi 0.8 Co 0.2 (C 6 H 5 O 7 ) 2 , is synthesized, which, after thermal decomposition, gives the layered mixed‐oxide phase Li 0.7 Ni 0.8 Co 0.2 O 2 . This oxide has been characterized by chemical analysis, XRD, FTIR, SEM, and DTA, revealing an “ideal” trigonal α‐NaFeO 2 type structure with a well‐ordered distribution of Li and Ni ions in different lattices. Thermoelectric power and four‐point electrical conductivity measurements indicate a nonactivated conductivity mechanism of a small polaron. The Li 0.7 Ni 0.8 Co 0.2 O 2 compound prepared by this so‐called “citrate route” has a better reversibility of Li‐insertion in charge–discharge cycles than related phases reported previously. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)