Improvement of Cycle Performance of Lithium-Ion Batteries at Elevated Temperature of 60oC Using Graphite Coated with Metal Oxide

Abstract

Improvement of cycle performance at 60oC by using SiOx modified graphite has been investigated. A main degradation mode of LiFePO4/Graphite cell was investigated. In LiFePO4 and graphite, the degradation of LIB is mainly due to the loss of Li+, and probably not due to the damage to active material analyzed by XRD pattern and charge-discharge curve. To suppress the loss of Li+, surface modification was examined. SEI formation on Si film is suppressed by modification of SiOx and AlOx. SEI thickness on the Si thin film coated with metal oxide (MOx) has critical influence on resistance of MOx. In the cyclic voltammetry, the intensity of the charge peak at 0.9V during the first charge indicates decomposition of an electrolyte. In SiOx modified graphite, the capacity estimated from 1 V to 0.7 V is decreased compared to the unmodified graphite. Cycle performance was improved by SiOx modified graphite.