Electric vehicle (EV)-use lithium batteries suffer large decreases in operating efficiency when exposed to working environment of very low temperatures, but the problem can be solved by a few methods, according to Digitimes Research's findings.
Working temperatures for normal operation of such batteries range from -20 degrees to 60 degrees Celsius, Digitimes Research indicated. If working temperatures drop to below -20 degree, electrolytic solution becomes more viscous like hair spray and consequently, mobility of lithium ions is reduced and so is operating efficiency for batteries, Research Insight explained.
Heating of batteries or addition of anti-freezing agents to electrolytic solution can solve the problem.
Similar to heating of copper sulfate solution in batteries used to start fuel cars in freezing environment, additional heating devices are used to hike working temperatures of batteries to -20 degree to let batteries start normal operation and then working temperatures will rise to above -20 degree after EVs run.
In order for higher operating efficiency, some EV vendors adopt thermal management technology for which heat-circulating pipes provide heat to maintain batteries at optimal working temperatures.
Alternatively, anti-freezing agents can be added to electrolytic solution to prevent it from getting more viscous. However, formulas of anti-freezing agents should be matched with electrolytic solution, cathode and anode materials, separation film of batteries to avoid reduction in battery's operating efficiency and service lives.
A fundamental solution of the problem is solid-state batteries, for solid-state electrolyte of them does not have the problem concerning viscosity of liquid. However, technological development of solid-state batteries is not yet mature and commercial use is estimated to begin three years after.
Besides impact of very low temperatures, chemical activity of batteries decreases when working temperatures drop to below zero degree, resulting in lower capability of discharging power and accordingly EVs' less endurance running distance.
Most of new EV models are equipped with cloud computing-based battery management systems to enable drivers to inquire about remaining power storage capacities of batteries via smartphones for estimating residual endurance running distance. This also enables EV vendors to detect low levels of power storage capacity and remind drivers of the need for power charging via smartphones.