New Hybrid Electrolyte For Solid-State Lithium Batteries

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Scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a novel electrolyte for use in solid-state lithium batteries that overcomes many of the problems that plague other solid electrolytes while also showing signs of being compatible with next-generation cathodes.

Berkeley Lab battery scientist Nitash Balsara, working with collaborator Joseph DeSimone of the University of North Carolina at Chapel Hill, came up with a highly conductive hybrid electrolyte, combining the two primary types of solid electrolytes—polymer and glass.

Their discovery is detailed in “Compliant Glass-Polymer Hybrid Single-Ion-Conducting Electrolytes for Lithium Batteries,” published online this week in the journal Proceedings of the National Academy of Sciences (PNAS), co-authored by Berkeley Lab researchers Irune Villaluenga, Kevin Wujcik, Wei Tong, and Didier Devaux, and Dominica Wong of U. North Carolina. Villaluenga, a postdoctoral fellow at Berkeley Lab, played a key role in designing and realizing the solid electrolyte; Balsara and DeSimone are the senior authors.

“The electrolyte is compliant, which means it can readily deform to maintain contact with the electrode as the battery is cycled, and also has unprecedented room temperature conductivity for a solid electrolyte,” said Balsara.

The electrolyte carries electrical charge between the battery’s cathode and anode and in most commercial batteries is liquid. Researchers are striving to develop a battery with all solid components, as it would likely perform better, last longer, and be safer.

The two kinds of solid electrolytes—polymer and glass or ceramic—each come with their own set of issues. Polymer electrolytes don’t conduct well at room temperature and need to be heated up. Ceramic electrolytes, on the other hand, do conduct well at room temperature but require a great deal of pressure to maintain contact with the electrodes. “It needs something like 1 ton over every square centimeter, so you need a big truck sitting on the battery as it cycles,” Balsara said.

The new material they developed, a glass-polymer hybrid, was made by taking particles of glass, attaching perfluoropolyether chains to the surface of the particles, adding salt, and then making a film out of these components. By tuning the polymer-to-glass ratio, they were able to come up with a compliant electrolyte with high conductivity at room temperature and excellent electrochemical stability.

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