A Safe Ether Electrolyte Enabling High-Rate Lithium Metal Batteries

High-energy-density lithium metal batteries (LMBs) hold enormous potential for future energy storage systems but are plagued by poor cycling stability and safety concerns, especially under high-rate conditions. The addition of fluorinated solvents to the electrolyte is effective in enhancing the stability of the lithium metal anode (LMA) and improving safety for LMBs. However, the extensive introduction of fluorinated solvents is not conducive to the transport of lithium-ions (Li⁺), thereby negatively affecting the rate performance of LMBs. Herein, a safe ether electrolyte (SEE) is designed that exhibits both high Li⁺ conductivity and nonflammability, while maintaining high compatibility with the LMA. Li–LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cells utilizing SEE can demonstrate remarkable electrochemical performance, delivering a discharge capacity of 113.1 mAh g⁻¹ at rates as high as 30 C and maintaining 90% of their initial capacity over 300 cycles at 10 C. Moreover, a practical Li-NCM811 full cell assembled with SEE achieves stable cycling at 3 C.