Suppressing dendrite growth by a functional electrolyte additive for robust Li metal anodes

Lithium (Li) metal is considered as an attractive anode for next-generation energy storage systems due to its higher energy density and the lowest redox potential. However, great challenges including safety issues associated with dendrite growth and low Coulombic efficiency (CE) related to poor cycle stability, especially at high charge current densities, are still impeding its practical uses in Li metal secondary batteries. Herein we propose that an optimal amount of lithium iodide (LiI) as a functional additive in ether-based electrolyte for dendrite-free Li deposition. The additive could induce the electrolyte polymerization to in-situ form a robust solid electrolyte interphase (SEI) layer enriched with elastic oligomer on Li surface. Furthermore, the LiI in the electrolyte heightens the ionic conductive of formed SEI and facilitates the migration of Li ion, remarkably promoting the uniform deposition of Li at Li/electrolyte interface and suppressing the growth of Li dendrite. With a controlled Li deposition in an optimal amount (2 wt%) of LiI as an additive in ether-based electrolytes, a prolonged cycling lifespan (>1200 h) with a hysteresis voltage of ∼250 mV at 2 mA cm−2, as well as a very high CE up to 98.1% for 200 cycles at 0.5 mA cm−2. Moreover, the fabricated Li||Se battery system delivers an improved cycling stability and decreased polarization.