England (Commonwealth Union) _The development of a new type of rechargeable lithium battery that is safer, lighter, and more compact than existing models has been pursued by labs around the world for years, and MIT researchers’ discovery may finally open that door.
The replacement of the liquid electrolyte between the positive and negative electrodes with a considerably thinner, lighter layer of solid ceramic material and the replacement of one electrode with solid lithium metal are the two essential components of this prospective advancement in battery technology. By doing this, the battery’s total size and weight would be significantly reduced, and the flammable liquid electrolytes that provide a safety issue would be eliminated.
Dendrites, however, have proven to be a significant obstacle in that pursuit.
Dendrites, whose name derives from the Latin for branches, are metal growths that can accumulate on the lithium surface and pierce into the solid electrolyte, eventually slicing through two electrodes and shorting out the battery cell. The cause of these metal filaments hasn’t been well understood by researchers, and there hasn’t been much progress in finding ways to stop them, making lightweight solid-state batteries a viable alternative.
The new study, which MIT Professor Yet-Ming Chiang, graduate student Cole Fincher, and five other researchers from MIT and Brown University are publishing today in the journal Joule, appears to provide an answer to the puzzle of what triggers dendritic growth. Additionally, it demonstrates how to stop dendrites from piercing the electrolyte.
In earlier research, the team discovered something that Chiang calls “surprising and unexpected”, namely that lithium, a very soft metal, can penetrate the hard, solid electrolyte material used in solid-state batteries as lithium ions move between the two sides of the battery during charging and discharging. The volume of the electrodes changes as a result of the ions’ back-and-forth movement. The solid electrolyte, which must maintain complete contact with both electrodes it is sandwiched between, is inevitably stressed as a result.
