Reevaluate low-concentration ether-based electrolytes for lithium metal batteries

Ether is regarded as an exceptional solvent in liquid electrolytes for lithium (Li) metal batteries due to its outstanding compatibility with Li metal anode. Low salt concentration in ether-based electrolytes (LCEEs) is highly favorable to reducing the cost of future Li metal batteries. Nevertheless, LCEEs have been reported to exhibit poor anodic stability (as low as 4.0 V vs. Li/Li+), therefore considered unsuitable for practical batteries using LiNixMnyCozO2 as cathodes and charge up to 4.4 V. Here, using 1.0 M lithium bis(fluorosulfonyl)imide (LiFSI) in 1,2-dimethoxyethane (DME) as the baseline, we demonstrate the intrinsic anodic stability window of LCEE to be above 4.5 V. We revealed the true failure mechanism of LCEE to be various electrochemical reactions with different working electrodes (WEs). We further provide electrolyte and electrode design rules to prevent LCEE decomposition, as well as electrode and packaging materials corrosion at high voltage. This study highlights the importance of previously overlooked battery component compatibility in electrolyte development and offers valuable insights into battery engineering considerations toward high-energy and cost-effective Li metal batteries.