Development of a high-power lithium-ion battery

Safety is a key concern for a high-power energy storage system such as will be required in a hybrid vehicle. Present lithium-ion technology, which uses a carbon/graphite negative electrode, lacks inherent safety for two main reasons: (1) carbon/graphite intercalates lithium at near lithium potential, and (2) there is no end-of-charge indicator in the voltage profile that can signal the onset of catastrophic oxygen evolution from the cathode (LiCoO2). Our approach to solving these safety/life problems is to replace the graphite/carbon negative electrode with an electrode that exhibits stronger two-phase behavior further away from lithium potential, such as Li4Ti5O12. Cycle-life and pulse-power capability data are presented in accordance with the Partnership for a New Generation of Vehicles (PNGV) test procedures, as well as a full-scale design based on a spreadsheet model.