Wide-temperature-range operation of lithium-metal batteries using partially and weakly solvating liquid electrolytes

Abstract

The optimal design of liquid electrolytes is vital for the build-up of long-lifespan lithium-metal batteries (LMBs) that function over a wide-temperature-range. Tuning the electrolyte solvation-structure using partially-fluorinated ether solvents and constructing stable electrode-electrolyte interfaces using electrolyte additives enhance the electrochemical reversibility of lithium-metal anodes and facilitate the realization of high-capacity cathodes for LMBs. This study reports a partially and weakly solvating electrolyte (PWSE) which enables the stable cycling of LMBs at high-voltages within a wide-temperature range through modulation of an electrolyte local-environment using a low-salt concentration of 1.3 M. 1,2-Bis(1,1,2,2-tetrafluoroethoxy)ethane contains two oxygen atoms that coordinate weakly with Li+-ions; it transforms the 1,2-dimethoxyethane-dominated electrolyte solvation-structure to a more anion-incorporated structure. Moreover, a combination of lithium fluoromalonato(difluoro)borate and silver nitrate strengthens the electrode-electrolyte interfaces and improves the oxidation durability of ether-based electrolytes. The PWSE enables the construction of 4.4 V Li|LiCoO2 full cells with a long-lifespan and high-areal-capacity of 3.12 mA h cm-2. With the aid of electrolyte additives, a partially and weakly solvating electrolyte which is acquired by controlling the local environment of the electrolyte qualifies the stable cycling of LMBs at high voltages over a wide temperature range.