There is considerable interest and demand in lithium-ion batteries for electric and hybrid vehicles, satellite, defense, and military applications in addition to the need for laptops, cell phones, and other portable devices. Battery performance - the capacities and lifetimes and safety, depend largely on the formation and development of the solid electrolyte interface (SEI) layer. Battery manufacturers and end users have expressed a real need for reduction of time needed for initial SEI formation and maturation/stabilization of lithium-ion batteries. In order to sustain and increase quality, each battery produced must go through initial charge/discharge cycles and shelf time. This can take up to one month for large-scale batteries. Standard constant current/constant voltage (CC/CV) charging practices are safer, but extend charging times and do not fully utilize active materials.

In an effort to reduce the maturation time, we have changed the initial protocol from CC/CV to a pulsed protocol, and the goal is to develop, implement, test, and evaluate specific pulsing parameters to optimize SEI formation time. Experimental cells have been fabricated using a split-cell setup. These cells were charged and discharged using both CC/CV and pulsed methods, and then subjected to electrochemical impedance spectroscopy (EIS) for comparative analysis. Data retrieved during EIS analysis showed a high degree of complexity and unpredictability. Thus, current research endeavors, to be presented in the poster, include new battery array designs and employ various optical techniques used to correlate changes in the SEI layer to changes in the impedance spectra. With high precision control of battery fabrication parameters, meaningful comparative investigation of battery cell structures, charging/discharging histories, systematic characterization and analysis, it may be possible to provide knowledge of how the SEI layer and dendrites form. It will then be possible to provide “design rules” to effectively address battery performance and safety issues.