Molecular Design of Mono‐Fluorinated Ether‐Based Electrolyte for All‐Climate Lithium‐Ion Batteries and Lithium‐Metal Batteries

Fluorinated‐ethers are promising electrolyte solvents in lithium metal batteries, for their high antioxidant and excellent reductive stability on Li anode. However, fluorinated‐ethers with high fluorination degree suffer from low ionic conductivity and narrow temperature adaptibility. Herein, we synthesize a mono‐fluorinated linear ether of bis(2‐fluoroethoxy) methane (BFME) with enhanced solvated ability. The −OCH2O− structure and fluoride substitution on the β‐C position endows the BFME electrolyte with moderate affinity to Li+, thereby improving the ionic conductivity and decreasing the Li+‐desolvation energy barrier at a wide temperature range of −60–60 °C. Additionally, the electrolyte with anion‐participated solvation structure demonstrates high film‐forming ability by forming LiF‐rich interfacial film on the electrode surfaces, rendering the graphite anode with an initial Coulombic efficiency (CE) of 94.9 % and a Li plating/stripping CE of 99.8 % by Aurbach method. Consequently, the Graphite||LiFePO4 pouch cells delivered 83.2 %, 92.5 % and 81.2 % capacity retention after 1250, 200 and 300 cycles at 25, −20 °C and 60 °C, respectively. Moreover, the Li||LFP pouch cell with 3 Ah capacity can operate for 65 cycles with 99 % capacity retention, verifying the effectiveness of the BFME electrolyte in stabilizing the interfaces and broadening the temperature adaptibility of lithium‐ion and lithium metal batteries. A mono‐fluorinated linear ether of bis(2‐fluoroethoxy) methane (BFME) with OCH2O‐ segment was synthesized as solvent. With signal salt and signal solvent, the electrolyte showed low Li+‐desolvation energy and high anion film‐forming ability at interfaces under −60–60 °C, realizing the reversibly Li+ insertion/extraction process into graphite anode with an initial Coulombic efficiency (CE) of 94.9 % and Li position/stripping CE of 99.8 %.