Electrochemistry of anodes in solid-state Li-ion polymer batteries

An examination of the electrochemical performance of solid-state lithium-ion batteries was carried out using a solvent-free solid-polymer electrolyte at 60 degrees C. We studied two different types of anode (negative electrode) material: graphite intercalation compound (CIC) or lithium-titanium oxide (Li4Ti5O12), and LiCoO2 was used as the cathode (positive electrode). Natural graphite and carbon fiber gave high reversible capacities of about 372 and 300 mAh/g, respectively. A Li4Ti5O12 vs, lithium cell discharged at the C/15 rate delivered 155 mAh/g corresponding to a 97% first-cycle Coulombic efficiency. The irreversible capacity was high when carbon material was used as the negative electrode. However, this sacrificial capacity was very small when we replaced carbon with the spinel material. The crystallographic structure of Li4Ti5O12 was analyzed by X-ray diffraction, and its stability was demonstrated by in situ scanning electron microscopy using Li4Ti5O12, which is a zero-strain insertion material that offers advantages for the solid-polymer electrolyte cell including safety, long life, and reliability.