Rubber is an insulator, and is essentially not an ideal electrolyte material for lithium-ion batteries, though Georgia Institute of Technology has managed to develop a highly conductive rubber material, and the particular flexible electrolyte makes it possible in creating EV batteries that are safer and longer in driving range.
Lithium-ion batteries have derived revolutions for multiple technologies, and introduced tremendous changes to the human civilization ranging from smartphones and notebooks to EVs and battery energy storage systems. However, lithium-ion batteries can still be improved in areas, such as possible fire or explosion from the liquid electrolytes of batteries during damages or overheating.
Is solid electrolyte the solution if liquid electrolytes are accompanied with risks of fire? The short answer is yes, as past experience tells us that solid electrolytes can effectively lower the risk of fire outbreak, though they also lead to other challenges, such as the slight “fragile” fixed electrolytes made with ceramic materials, as well as the incomprehensive interface between electrolytes and electrodes that would also decrease the conductivity of lithium-ions.
Hence, the research team at Georgia Institute of Technology believes that flexible materials such as rubber will be able to resolve the two above-mentioned issues. Due to the insulation property of rubber, the team embedded the conductive succinonitrile, whereas the rubber part serves as a more elastic 3D bracket that facilitates a smooth interface between electrolytes and electrodes, which also prevents growths of dendrites.
As indicated by the test, a lithium-ion battery adopted with the new electrolyte is able to operate with a voltage of 4.5V under room temperature, with almost no deterioration in capacity (93 mAh g-1) after 1000 circulations, and no dendrite growths after 100 cycles of charging and discharging. Of course, the results can be better, and the team is currently trying to elevate the number of circulations and the conductivity rate of ions that will eventually present batteries that are safer and more prolonged in duration.
Lead author Michael Lee commented that higher ion conductivity indicates more ion movement, where the increase of specific energy in batteries and density of energy will further extend driving range of EVs.
As a renowned EV innovation center, University of Georgia is also working with SK Innovation, who is currently subsidizing on the studies of electrolyte materials in the hopes of producing the next generation solid-state batteries that are safer and higher in energy density as opposed to traditional lithium-ion batteries. SK Innovation recently announced its establishment of a battery plant at Commerce, Georgia, which is expected to arrive at an annual production of 21.5GWh by 2023.
(Cover photo source: University of Georgia)