Lithium-ion batteries power a vast majority of the world’s portable electronics, from smartphones to laptops. A standard lithium-ion batteries utilizes a liquid as the electrolyte between two electrodes. However, the liquid electrolyte has the potential to lead to safety hazards. Researchers from MIT believe that by using a solid electrolyte, lithium-ion batteries could be safer and able to store more energy. However, most research in the area of all-solid-state lithium-ion batteries has faced significant barriers.
According to the team from MIT, a reason why research into solid electrolytes has been so challenging is due to incorrect interpretation of how these batteries fail.
This from MIT:
The problem, according to this study, is that researchers have been focusing on the wrong properties in their search for a solid electrolyte material. The prevailing idea was that the material’s firmness or squishiness (a property called shear modulus) determined whether dendrites could penetrate into the electrolyte. But the new analysis showed that it’s the smoothness of the surface that matters most. Microscopic nicks and scratches on the electrolyte’s surface can provide a toehold for the metallic deposits to begin to force their way in, the researchers found.
“The formation of dendrites, leading to eventual short-circuit failures, has been the main reason that lithium-metal rechargeable batteries have not been possible,” says Yet-Ming Chiang, co-author of the research and winner of the 2012 ECS Battery Division Technology Award.
According to Chiang, researchers focusing on solid electrolytes should be looking at the quality of the surfaces, making sure they are smooth and defect-free.
“I believe that this high-quality and novel work will reset the thinking about how to engineer practical lithium metal solid-state batteries,” says ECS member Alan Luntz, a consulting professor for metal-air battery research at Stanford University, who was not involved in this research. “The authors have shown that a different mechanism governs lithium metal shorting in lithium solid-state batteries than in liquid or polymer lithium metal batteries where dendrites form. This implies that if lithium metal solid-state batteries are ever to have practical current densities, then careful minimization of all structural defects at the lithium metal and electrolyte interface is essential. I consider it to be an extremely important contribution to the goal of developing practical and safe all solid-state batteries.”