Improving the Performance of Lithium Ion Batteries at Low Temperature

Li-ion batteries are considered promising candidates for electric vehicles (EV) and hybrid electric vehicles (HEV). At the present time, commercially available HEVs use nickel metal hydride (NiMH) batteries ¿ which are expensive and heavy, and have limited power and energy ¿ features critical to HEV success. Currently, the poor performance of Li-ion batteries at low temperature is the main roadblock to implementing this technology in the EV and HEV commercial markets. In particular, the formation of high interfacial impedance at the electrode interfaces has been shown to result in progressive capacity-fading and limited discharge-rate at low temperatures. Consequently, in order to improve the low-temperature performance of Li-ion battery, the resistance at the electrode (anode and cathode) interfaces must be minimized at low temperatures. This project will identify, evaluate, and modify cell components, such as electrolyte and electrode materials, in order to enhance the low temperature performance of Li-ion cells without compromising their room temperature properties. Phase I will involve two simultaneous approaches: (1) development of new electrolyte formulations; and (2) modification of the surface chemistry and bulk properties of the electrode components, in order to improve their stability and minimize their low-temperature interfacial impedance in the presence of these new electrolyte formulations. The combined approach will improve the stability of the electrode/electrolyte interface and increase the charge/discharge capability at low temperatures. Commercial Applications and Other Benefits as described by the awardee: Li-ion batteries should have approximately twice the power and energy of an equivalent NiMH batery. Further, Li-ion batteries will be less expensive, safer, and lighter, and more environmentally friendly. The market potential for lithium ion batteries is very large, growing at ~20% annually. High-volume applications in civilian markets include power communications equipment, portable computers, video recorders, night vision devices, and various sensors.