The faster electric can be charged, the more viable and the potential economic success of electric vehicles. Drivers don’t have an hour or even 30 minutes to charge their batteries to get home, work or another destination.
Lithium-ion batteries (LIBs) provide offer high energy density, but while they make it possible to driving within a reasonable range, they take considerably longer to recharge than traditional vehicles. Multiple properties of the applied anode, cathode, and electrolyte materials affect the fast-charging ability of a battery cell.
Two years ago, a dozen senior battery and supercapacitor expert scientists and 30 doctoral students and postdoctoral fellows from both Israel and Germany attended the 4th German-Israeli Battery School (GIBS 4) in Berlin, Germany. The Berlin workshop was focused on in-depth discussions on four “hot subjects,” including: How will the far future of electrochemical power sources be after the lithium era, if ever? Will the future of portable power sources be based on liquid or solid electrolytes? Fuel cells versus battery technologies – complementary or competitors? And finally, the topic of fast charging – a reality or just a dream?
In a review published this month in the high impact journal Advanced Energy Materials under the title “Fast Charging of Lithium-Ion Batteries: A Review of Materials Aspects, an international team of researchers studied in detail the physicochemical basics of different material combinations and identified the transport of lithium inside the electrodes as the crucial rate-limiting steps for fast charging.
In addition, concentration polarization by a slow lithium-ion transport within the electrolyte phase in the porous electrodes also limits the charging rate. Both kinetic effects are responsible for lithium plating observed on the graphite anodes. Such plating of metallic lithium may lead to a dangerous thermal runaway, resulting in explosion and fire.
The conclusions drawn by the researchers from potential and concentration profiles within LIB cells are complemented by extensive literature surveys on anode, cathode, and electrolyte materials. They analyzed the advantages and disadvantages of typical LIB materials and offered suggestions for optimum properties on the material and electrode level for fast-charging applications.
The group was headed by Prof. Yair Ein-Eli and graduate student Natasha Ronit Levy from the department of materials science and engineering at the Technion-Israel Institute of Technology in Haifa, along with Prof. Jürgen Janek and Dr. Manuel Weiss from Giessen University (Institute of Chemical Physics, Germany). They concluded that lithium-ion diffusion and migration within the active materials inherently slows down the charging process and imposes high resistivity.