Electronic structure of the transition metal ions in LiCoO2, LiNiO2 and LiCo0.5Ni0.5O2

We studied the electronic structure of the transition metal ions in LiCoO2, LiNiO2 and LiCo0.5Ni0.5O2. The experimental technique used in the study wa s Co 2p and Ni 2p X-ray absorption spectroscopy. The experimental results w ere analyzed using atomic multiplet plus crystal field calculations. The Co ions in LiCo0.5Ni0.5O2 are in a trivalent Co3+ low-spin state given by t(2 g)(6) ((1)A(1)), as in LiCoO2. The Ni ions in LiCo0.5Ni0.5O2 are in a dival ent Ni2+ high-spin state given by t(2g)(6) e(g)(2) ((3)A(2)), as in LiNiO2. The missing charge at the Ni site is compensated by a less negative O ion; this means that the charge state in LiNiO2, for instance, is closer to LiNi2+O21.5- than to me usually quoted Li+Ni3+O22-. This Is important for und erstanding the oxidation-reduction process es upon Li deintercalation-ninte rcelation reactions. (C) 1999 Elsevier Science B.V. All rights reserved.