Low temperature performance evaluation of electrochemical energy storage technologies

The performance of electrochemical energy storage technologies such as batteries and supercapacitors are strongly affected by operating temperature. At low temperatures (<0 °C), decrease in energy storage capacity and power can have a significant impact on applications such as electric vehicles, unmanned aircraft, spacecraft and stationary power storage. In this work, the discharge behaviour of nine different commercial electrochemical cells are evaluated, representing a variety of lithium-ion, nickel metal hydride, lead acid and supercapacitor technologies. Discharge capacity, energy, maximum power and impedance spectra with equivalent circuit analysis are compared at temperatures ranging from +20 °C to -70 °C. Results demonstrate that despite exhibiting the greatest loss in performance with temperature reduction, the lithium-ion batteries tested provide the highest energy and power densities down to - 30 °C due to higher capacity and operating voltage. At lower temperatures, the lead-acid cell gives the highest energy density and supercapacitor the highest power density. A new simplified empirical method is introduced for lithium-ion cells to determine the optimum pre-heating temperature for maximum net energy output including heating efficiency. This new method can be used to assess the benefits of different cold-start thermal management strategies for electric vehicles. It is also demonstrated that the temperature of the lithium-ion cells tested can be accurately predicted from impedance phase change at low temperatures across a range of electrode materials.