FTIR SPECTROSCOPY OF METAL-OXIDE INSERTION ELECTRODES - A NEW DIAGNOSTIC-TOOL FOR ANALYSIS OF CAPACITY FADING IN SECONDARY LI LIMN2O4 CELLS/

Fourier transform infrared spectroscopy (FTIR) has been applied to the study of oxide insertion compounds used in rechargeable lithium batte ries. The mechanisms responsible for capacity fading during normal cyc ling of LiMn2O4 cells in both the 3 and 4 V regions were determined by examination of spectra obtained from electrodes following 25 cycles a t charge and discharge rates of C/6. In the 3 V region, electroactive material becomes electronically disconnected from the rest of the elec trode due to fracture of the oxide particles and/or expansion and cont raction of the active material during the cubic-to-tetragonal phase tr ansformation. In the upper voltage region, the active electrode materi al is gradually converted to a lower voltage defect spinel phase via d issolution of manganese in the electrolyte.