Dendrite-free, wide temperature range lithium metal batteries enabled by hybrid network ionic liquids

Abstract

Replacing liquid electrolytes with solid-state electrolytes is a promising approach to achieving practical applications of lithium metal batteries (LMBs). In this work, ionic liquid N-methyl-N-propyl-pyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI) was introduced into a hybrid network to obtain a series of gel polymer electrolytes (GPEs). Mechanical and electrochemical properties of the GPEs were tuned through controlling the network structure and ionic liquid contents, and ionic conductivity higher than 1 ​mS ​cm-1 at room temperature was achieved. The newly developed GPEs are flame-retardant and show excellent thermal and electrochemical stability as well as ultra-stability with lithium metal anode. Symmetrical lithium cells with the GPEs exhibit a stable cycling over 6800 ​h ​at a current density of 0.1 ​mA ​cm-2 and stable lithium stripping-plating at 1 ​mA ​cm-2, the highest current density reported for ionic liquid-based GPEs. Detailed correlation between mechanical properties, ionic conductivity and cell short-circuit time is discussed. Moreover, Li/LiFePO4 batteries with the obtained GPEs exhibit desirable cycling stability and rate performance over a wide temperature range from 0 ​°C to 90 ​°C, further suggesting that this new hybrid-network/ionic liquid GPE system has great potential for practical applications in next generation LMBs.