All-fluorinated electrolyte for non-flammable batteries with ultra-high specific capacity at 4.7 V

• Published in: Green energy & environment 2024-10, Vol.9 (10), p.1601-1609
• Main Authors: Wang, Zhe, Li, Zhuo, Fu, Jialong, Zheng, Sheng, Yu, Rui, Zhou, Xiaoyan, He, Guanjie, Guo, Xin
• Format: Article
• Language: English
• Subjects: Cathode electrolyte interphase; Cathodes; Cathodic dissolution; Coulombic efficiency; Cycles; Decomposition; Dissolution; Efficiency; Electrolytes; Electrons; Energy; Energy charge; Flammability; Fluorinated electrolyte; Fluorination; Gas production; Li metal batteries; Life span; Lithium; Lithium batteries; Nickel; Oil and gas production; Oxidation; Side reactions; Solid electrolyte interphase; Solvents; Specific capacity; Specific energy; Transition metals; Voltage
• ISSN: 2468-0257; 2096-2797; 2468-0257
• DOI: 10.1016/j.gee.2023.06.002

Li metal batteries (LMBs) with LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes could release a specific energy of >500 Wh kg−1 by increasing the charge voltage. However, high-nickel cathodes working at high voltages accelerate degradations in bulk and at interfaces, thus significantly degrading the cycling lifespan and decreasing the specific capacity. Here, we rationally design an all-fluorinated electrolyte with addictive tri(2,2,2-trifluoroethyl) borate (TFEB), based on 3, 3, 3-fluoroethylmethylcarbonate (FEMC) and fluoroethylene carbonate (FEC), which enables stable cycling of high nickel cathode (LiNi0.8Co0.1Mn0.1O2, NMC811) under a cut-off voltage of 4.7 V in Li metal batteries. The electrolyte not only shows the fire-extinguishing properties, but also inhibits the transition metal dissolution, the gas production, side reactions on the cathode side. Therefore, the NMC811||Li cell demonstrates excellent performance by using limited Li and high-loading cathode, delivering a specific capacity >220 mA h g−1, an average Coulombic efficiency >99.6% and capacity retention >99.7% over 100 cycles. Co-effect of components in all-fluorinated electrolyte (LiPF6-FEC/FEMC/TFEB) promotes the formation of LiF-rich solid electrolyte interphase (SEI) and F-/B-rich cathode electrolyte interphase (CEI), thus achieving a high specific capacity in the NMC811||Li battery under a voltage of 4.7 V. [Display omitted] •The fundamentals and design strategies of the fully-fluorinated electrolyte are concluded.•The fully-fluorinated electrolyte decreases side-effect and forms highly stable cathode-electrolyte interphases.•Full cells with the high-loading cathode and the limited Li retain 99.7% capacity for 100 cycles under harsh conditions.