Highly Oxidation‐Resistant Ether Gel Electrolytes for 4.7 V High‐Safety Lithium Metal Batteries

Ether electrolytes are considered to be one of the most promising candidates for lithium metal batteries (LMBs) since they help to form a stable solid electrolyte interface (SEI) on lithium anodes. However, conventional liquid ether electrolytes are not suitable for the high‐voltage LMBs over 4.5 V due to their narrow potential windows. Herein, a gel electrolyte strategy is demonstrated to improve the high voltage stability of ether electrolytes in LMBs with Li‐rich layered oxide (LLO) cathodes that usually operate at 4.6 V and above. Compared with a liquid electrolyte, the electrochemical window of the gel electrolyte with cross‐linked amide framework is increased by 1 V. The strong cross‐linked framework not only regulates the uniform growth of cathode electrolyte interface (CEI)/SEI on the cathode/anode sides, but also greatly increases the Li+ transference number and inhibits the generation of harmful substances by anchoring PF6− anions, thus providing a long cycle for LMBs at a high voltage up to 4.7 V. Simultaneously, the flame retardancy and flexibility of the gel electrolyte ensures the safe operation of high‐voltage LMBs. Therefore, the LLO||Li pouch cell using gel electrolyte realizes stable cycling at a high voltage 4.6 V, and can pass the acupuncture test. A gel electrolyte strategy to achieve stable operation of fluorinated ether electrolytes in high‐voltage and high‐safety lithium metal batteries (LMBs). The LLO||Li half cells using a gel electrolyte can steady operation at high voltage of 4.7 and 4.6 V, and the capacity retention is up to 86.7% after 500 cycles at 4.6 V. The corresponding LLO||GPE||Li pouch cell realizes stable cycling performance and successfully passes the acupuncture test.