Photoelectron spectroscopy studies of Li1+xMn2-xO4 for Li ion battery applications

Using photoelectron spectroscopy (PES) we have studied the surfaces of Li1+xMn2-xO4 materials and related surface properties with the electrochemical performance of Li/Li1+xMn2-xO4 cells. The surface seems to be more lithium rich than the bulk as the amount of excess lithium is increased. A Li 1s component with binding energy of about 54.5 eV and a Mn 3p component with binding energy of about 47.6 eV are shown to be correlated with the undesirable 3.3 V discharge plateau in Li/Li1+xMn2-xO4 cells. Using a series of samples quenched from different temperatures we have also studied the surface composition at different temperatures. The PES results of a good performing sample, that cycles well even at a temperature as high as 55 degrees C are also shown. This shows that PES can be useful to qualify good spinel materials for Li-ion battery applications. (C) 1996 American Institute of Physics.