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 group: (i) uniform and dense thin films of LiMn2O4, up to 0.5 mum thickness have been synthesized by electrostatic spray deposition (ESD). The electrochemical 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 numerous sphere-shaped single particles have been also evaluated by transient techniques as well as by ac-impedance spectroscopy. (iii) Electrochemical quartz crystal microbalance (EQCM) technique was employed to study the low capacity fading of LiMn2O4 at elevated temperatures in LiPF6 containing solutions. It has been confirmed that this phenomenon is due to the manganese dissolution promoted by acidic species (HF) originated from the reaction of LiPF6 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 significant capacity fading even in the 1 M LiPF6/PC-EC (1:1) solution at 50 degreesC upon 50 cycles of charge/discharge. (C) 2001 Elsevier Science B.V. All rights reserved.