Electrochromic ＆ magnetic properties of electrode materials for lithium ion batteries

Progress in electrochromic lithium ion batteries （LIBs） is reviewed, highlighting advances and possible research di- rections. Methods for using the LIB electrode materials＇ magnetic properties are also described, using several examples. Li4Ti5Ol2 （LTO） film is discussed as an electrochromic material and insertion compound. The opto-electrical proper- ties of the LTO film have been characterized by electrical measurements and UV-Vis spectra. A prototype bi-functional electrochromic LIB, incorporating LTO as both electrochromic layer and anode, has also been characterized by charge- discharge measurements and UV-Vis transmittance. The results show that the bi-functional electrochromic LIB prototype works well. Magnetic measurement has proven to be a powerful tool to evaluate the quality of electrode materials. We introduce briefly the magnetism of solids in general, and then discuss the magnetic characteristics of layered oxides, spinel oxides, olivine phosphate LiFePO4, and Nasicon-type Li3Fez（PO4）3. We also discuss what kind of impurities can be detected, which will guide us to fabricate high quality films and high performance devices.