Layered Cobalt and Nickel Oxide Cathodes: a Comparison of their Structural and Chemical Stabilities

A. MANTHIRAM; R.V. CHEBIAM; F. PRADO

Long Beach

Conferencia; 16th Annual Battery Conference on Application and Devices; 2001

The Institute of Electrical and Electronics Engineers, Inc

Layered LiNi0.85Co0.15O2 cathode has drawn much attention recently due to its higher capacity compared to the currently used layered LiCoO, cathode. However, the structural and chemical stabilities of the LiNi0.85Co0.15O2 cathodes during long-term cycling in lithium-ion cells have not been fully assessed. From a systematic investigation, the structural and chemical stabilities of the two systems are compared. Wet-chemical analysis of chemically delithiated Lil-xCoO2 and Lil-xNi0.85Co0.15O2 establish that the former system tends to lose oxygen from the lattice for (1-x)< 0.5, which limits its capacity to 140 mAh/g, while the latter system does not suffer from oxygen loss at least for 0.3 < (1-x) < 1. However, the nickel oxide system suffers from structural instability under mild heat (T > 50 °C) due to a migration of Ni3+ ions from the nickel layer to the lithium layer. The differences in the structural and chemical stabilities between the two systems are explained based on crystal field stabilization energies and the relative positions of metal:3d and O:2p bands.