Spontaneous aggregation in ether-functionalized ionic liquid-based non-flammable electrolyte for high-performance lithium metal battery

High-safety and high-performance electrolytes are in great demand for lithium metal batteries (LMBs) with highenergy-density, due to the volatile nature of lithium (Li) metal anode. This study proposes a nonflammable electrolyte containing 50 wt% [Pyr1,1O1]FSI 1,1O1 ]FSI (N-methoxymethyl-N-methylpyrrolidinium bis(fluorosulfonyl) amide) and 0.2 M Li bis(trifluoromethanesulfonyl)imide in 1,3-dioxolane/dimethoxymethane (1/1, vol.) to enhance the performance of LMBs significantly. Both experimental and simulation results demonstrate that the coordination of Li+ + ion with the ether oxygen atom in [Pyr1,1O1] 1,1O1 ] overcomes their electrostatic repulsion, resulting in aggregation of Li+ + with [Pyr1,1O1]. 1,1O1 ]. This marks the first observation of Li+ + aggregates (AGGs) containing an organic cation. Such unique aggregation renders the electrolyte more reduction resistant and facilitates more uniform decomposition to form robust LiF-rich solid electrolyte interphase. When used in LMBs, the AGG-rich electrolyte exhibits vastly superior performance compared to electrolytes with fewer or no AGGs. For instance, the Li/LiFePO4 4 cells with an electrolyte containing 50 wt% [Pyr1,1O1]FSI 1,1O1 ]FSI achieve maximum capacities of 164 and 142 mAh & sdot;g-- 1 at 0.1 and 0.5C respectively, with capacity retention of about 80 % after 600 cycles.