All-Temperature, High-Energy-Density Li/CF_x Batteries Enabled by a Fluorinated Ether as a Cosolvent

Lithium/fluorinated carbon (Li/CFx) batteries have received widespread attention due to their high specific energy density. However, the development of Li/CFx primary batteries is seriously hampered owing to the low electrical conductivity and poor wettability against the fluorinated carbon electrolyte. Here, we report a CFx-compatible fluorinated ether-containing electrolyte for all-temperature high-energy-density Li/CFx primary batteries. Specifically, a CFx-philic 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) is introduced to the carbonate-based electrolyte as a cosolvent. Benefiting from the low viscosity and low freezing point of TTE, the conductivity and wettability are drastically improved, contributing to a lowered charge-transfer resistance. Thus, the modified electrolyte with TTE endows Li/CFx batteries with high energy density of 850 Wh kg–1 at 25 °C and 745 Wh kg–1 at 55 °C under the current density of 5000 mA g–1, accompanied by high power density of 9931 and 10046 W kg–1, respectively. Even at the freezing temperature of −50 °C, Li/CFx batteries can still exhibit a high middle value of voltage of 1.91 V, and the discharge capacity is 299 mAh g–1 at 100 mA g–1. The improvement of electrochemical performance over a wide temperature range from −50 to 55 °C has greatly expanded the application of Li/CFx batteries.