Abstract

Electrolytes are critical enabling components for Li-ion batteries to safely operate within a wide temperature range, under extreme fast charging, and under intense abuse conditions without sacrificing energy density and cycle life. Current electrolytes cannot satisfy these requirements. We developed advanced all-fluorinated electrolytes, water-in-sale (WIS) electrolytes and solid-state electrolytes aiming to simultaneously enhance cell energy density and safety.  Guided by the electrolyte design principle for high-capacity electrodes with large volume changes, we developed serval organic liquid electrolytes suitable for micro-sized Si and Li metal anodes and NMC cathodes. We also reduced the salt concentration of water-in-salt electrolytes from 21m to 4.5m, and extended the electrochemical stability window from 3.0V of WIS to 3.4V. These improved electrolytes enable LiMn₂O₄/Li₄Ti₅O₁₂ pouch cells with an areal capacity of 2.5 mAh/cm² and a P/N capacity ratio of 1.14 to achieve a long cycle life of 500. For solid state electrolyte Li metal batteries, we suppressed the Li dendrite growth and reduced the interface resistance by constructing a lithionphobic-lithiophoilic interlayer between solid electrolyte and Li metal anodes. The critical role of solid electrolyte interphase in accommodating electrode volume changes was also investigated.