A Multifunctional Dual‐Salt Localized High‐Concentration Electrolyte for Fast Dynamic High‐Voltage Lithium Battery in Wide Temperature Range

Abstract In this work, a multifunctional 2m dual‐salt sulfolane (TMS)/ethyl acetate (EA)‐based localized high‐concentration electrolyte (LHCE) with 10 wt% fluorocarbonate (FEC) is reported. Its incorporation into a Li||Ni 0.5 Co 0.2 Mn 0.3 O 2 battery enables it to maintain nearly 89% capacity retention after 200 cycles with 1 C (200 mA g −1 ) charge/discharge current density charged to 4.6 V at 25 °C, showing good high‐voltage cyclic stability. A superior 10 C high‐rate performance with 65% (≈130 mAh g −1 ) specific capacity is also achieved. Furthermore, it still remains a liquid and exhibits good ionic conductivity even at −80 °C, and enables Li||Ni 0.5 Co 0.2 Mn 0.3 O 2 batteries to deliver more than 50% of their room‐temperature capacity at −40 °C and remains stable for over 200 cycles under the same condition as before, realizing outstanding low‐temperature fast‐charging/discharging performance. It also demonstrates compatibility with both lithium metal and graphite anode. All in all, this work provides a new idea for the design of a fast‐dynamic, high‐voltage, and low‐temperature lithium battery electrolyte. The findings of this work indicate that LHCEs made directly from the optimal high‐concentration electrolyte are not the most suitable approach, combining the diluent with an additive is necessary and effective.