Recent investigations on thin films and single particles of transition metal oxides for lithium batteries

Various aspects in the lithium battery field have been explored in our grou p: (i) uniform and dense thin films of LiMn2O4, up to 0.5 mum thickness hav e been synthesized by electrostatic spray deposition (ESD). The electrochem ical properties of these films were investigated by cyclic voltammetry and impedance spectroscopy under a variety of experimental conditions. (ii) The kinetic and transport properties of Lithium insertion/extraction of numero us sphere-shaped single particles have been also evaluated by transient tec hniques as well as by ac-impedance spectroscopy. (iii) Electrochemical quar tz crystal microbalance (EQCM) technique was employed to study the low capa city fading of LiMn2O4 at elevated temperatures in LiPF6 containing solutio ns. It has been confirmed that this phenomenon is due to the manganese diss olution promoted by acidic species (HF) originated from the reaction of LiP F6 with water. (iv) Alternative materials were sought to replace the actual LiCoO2 or LiMn2O4. Among them: Li1.1Mn1.9O4. LiNi0.85Co0.15O2, and Li,Li1. 10Mn1.852Cr0.048O4. Interestingly, Li1.10Mn1.852Cr0.048O4 exhibited no sign ificant capacity fading even in the 1 M LiPF6/PC-EC (1:1) solution at 50 de greesC upon 50 cycles of charge/discharge. (C) 2001 Elsevier Science B.V. A ll rights reserved.