Rapid Charging of Lithium-Ion Batteries Using Pulsed Currents

Abstract

Lithium-ion batteries are typically charged using constant current that is applied until the cell voltage reaches about 4.2 V, at which time, charging continues at a constant voltage until the full battery capacity is attained.This process is slow, typically requiring 2-4 h.Empirically selected pulse-charging sequences have been shown to provide enhanced charging; however, no model exists to explain and optimize the pulse-charging protocols.Modeling the lithium diffusion into a homogeneous intercalant layer indicates that the lithium concentration reaches saturation at the graphite/electrolyte interface after about 1 h under conventional constant current charging, mandating the shift to the lower rate constant voltage charging.It is shown here that charging the lithium battery using non-dc waveforms with properly selected parameters may circumvent this lithium saturation, enabling charging at significantly higher rates.A nonlinearly decreasing current density profile which conforms to the mass transfer coefficient variation was shown to provide complete charging in less than 3 4 of an hour, faster than any other pulse-charging profile studied.