M. Baginska, B.J. Blaiszik, R.J. Merriman, J.S. Moore, N. R. Sottos, and S.R. White
University of Illinois
Lithium-ion (Li-ion) batteries are widely used for powering mobile electronic devices, ranging from consumer electronics to electric vehicles. Improvements in safety are necessary, especially with the increased energy densities in advanced battery systems. Currently, multi-layer separators are used to terminate cell operation if the internal battery temperature exceeds a design threshold corresponding to the softening temperature of the separator. However, the separator can fail, due to shrinkage of the separator, exposing the electrodes to internal shorting if the cell temperature continues to increase post-shutdown as a result of thermal inertia.
To enhance the safety of Li-ion batteries, researchers at the Center for Electrochemical Energy Science, a U.S. Department of Energy Energy Frontier Research Center, have developed a novel technique to terminate cell operation during an overheating event, while minimizing the risk for electrode shorting. Autonomic, thermally induced shutdown of Li-ion batteries is demonstrated by incorporating thermoresponsive polyethylene (PE) microspheres (ca. 4 µm) onto battery anodes. When the internal battery environment reaches a critical temperature, the microspheres melt and coat the anode with a non-conductive barrier, halting Li-ion transport and shutting down the cell permanently (Figure 1). Scanning electron microscopy (SEM) images of electrode surfaces from cells that have undergone autonomic shutdown provides evidence of melting, wetting, and resolidification of PE into the anode and polymer film formation at the anode/separator interface. This work was published as a cover article in the journal Advanced Energy Materials.
Figure 1 caption: (Left panel) cross-section and top-down view of a normal MCMB anode; (center panel) cross-section and top-down view of an MCMB anode coated with thermoresponsive microspheres; and (right panel) cross-section and top-down view of a coated MCMB anode that has undergone shutdown.
M. Baginska, B.J. Blaiszik, R.J. Merriman, N.R. Sottos, J.S. Moore, and S.R. White, “Autonomic Shutdown of Lithium-Ion Batteries Using Thermoresponsive Microcapsules,” Advanced Energy Materials 2(5), 583–590 (2012).