Researchers at Georgia Institute of Technology have been using an x-ray technique to help figure out how to build a long-lasting solid state battery.
Typical lithium-ion batteries release energy through the transfer of lithium ions between two electrodes through a liquid electrolyte. Solid state would be potentially safer and ideal for electric vehicles.
The researchers have used X-ray computed tomography to visualize how cracks form at the edges of materials in the solid state batteries. Learning about the cracks and how they form will help engineer interfaces between solid pieces to make them last as long as possible, said Matthew McDowell, assistant professor of mechanical engineering.
McDowell and Christopher Saldana, also an assistant professor in mechanical engineering, have been placing a solid state battery under an x-ray microscope and charging it and discharging it to look for signs of degradation. They found that over several days, a weblike pattern of cracks formed in the material.
They found that this fracturing during the charging/discharging cycle causes a resistance to the flow of ions. McDowell said previous research had assumed that chemical reactions are the cause for cell degradation, but It is really the cell fractures themselves.
Solving the fracturing problem may help in the development of more durable interfaces to work toward high energy density solid state batteries. “If you could use solid lithium with a solid electrolyte, that would be the holy grail of energy density,” McDowell said.
Industry interest in building a solid state battery is keen. Researchers at imec in Belgium said recently they are using a solid nanocomposite electrolyte to double the energy density of a battery cell over their discovery of one year ago. Their latest effort has created a battery with an energy denstiy of 400 Wh/l, with a charging speed of two hours.
Imec wants to surpass wet Li-ion battery performance and reach 1000 Wh/l with a charging speed of less than 30 minutes by 2024.