| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1295453 | Solid State Ionics | 2016 | 8 Pages |
•Magnetic measurements on LixCoO2 cathodes with precise background correction•Battery charging/discharging monitored by in-operando magnetometry.•Anderson-type of nonmetal–metal transition deduced from χ0 − x variation.•Structural reordering for x ≤ 0.55 observed by magnetometry and positron annihilation.•Complex oxidation behavior involving O deduced from observed Co-oxidation state.
The variation of the structural and electronic properties of LixCoO2 upon electrochemical Li-extraction was studied over wide range concentration of 1 ≥ x ≥ 0.20 by means of SQUID magnetometry. The ex-situ measurements performed for 13 different compositions were supplemented by operando measurements of the magnetic moment during repetitive electrochemical in-situ cycling of the Li-concentration. From the temperature-dependent measurements an effective magnetic susceptibility with Curie–Weiss behavior and an additional temperature-independent part due to Pauli and Van Vleck magnetism is derived. The increase of the temperature-independent susceptibility with Li-extraction reflects a concomitant increase of the electronic density of states and, in addition, indicates an Anderson-type of the occurring nonmetal–metal transition. The effective magnetic moment reveals that only a fraction of 30% of the charge is transferred to Co upon Li-extraction indicating a complex oxidation behavior involving oxygen. Exposure to ambient atmosphere gives rise to a complete oxidation of Co. The results on the structural variation with Li-concentration are compared with accompanying measurements by X-ray diffraction and by our recent defect studies by positron annihilation.
