UC Davis

Here, we advance electrode-omics to identify evolutionary bursts by which ethereal locally superconcentrated electrolytes (LSCEs) mitigate silicon anode degradation through its epochs of electrochemical and chemical reactions. Anode composites form initially at high potential from ethereal solvent and anion [bis(fluorosulfonyl)imide (FSI^-)] redox. A first evolutionary burst at lower potential enriches composites with lithium alkoxides (LiO-R) and lithium oxide (Li₂O) and depletes sulfur oxides (SO_x) species. As the cells are cycled, a second evolutionary burst takes place, where previously extinct SO_x species reemerge concurrently with a loss of LiO-R and Li₂O. This identifies reactions rooted in "SuFEx" chemistry, where oxoanionic LiO-R and Li₂O species, electrochemically generated in the solid-electrolyte interphase, chemically react with FSI^- in the electrolyte to form emergent species. This sequence of evolutionary bursts produces a mechanically resilient composite that reduces silicon anode cracking over hundreds of cycles, leading to overpotential increase of only ~0.01 volts after 200 cycles.