MnO microspheres with and without carbon coating are prepared as anode materials for lithium ion batteries. The MnO microsphere material shows a reversible capacity of 800 mAh g(-1) and an initial efficiency of 71%. It can deliver 600 mAh g(-1) at a rate of 400 mA g(-1). Results of Mn K-edge X-ray absorption near-edge structure (XANES) spectra and extended X-ray absorption fine structure (EXAFS) confirm further the conversion reaction mechanism, indicate that pristine MnO is reduced to Mn after discharging to 0 V and part of reduced Mn(0) is not oxidized to Mn(2+) after charging to 3 V. This explains the origin of the initial irreversible capacity loss partially. The quasi open circuit voltage and the relationship between the current density and the overpotential are investigated. Both indicate that there is a significant voltage difference between the charging and discharging profiles even when the current density decreases to zero. (C) 2010 Elsevier B.V. All rights reserved.