Synergistic ionic-molecular coordination engineering in weakly solvating ether electrolytes for stable high-voltage lithium metal batteries

Abstract

Lithium metal batteries (LMBs) face critical challenges such as uncontrolled Li dendrite growth, unstable interfaces, and irreversible inactive Li formation. This study proposes an ionic-molecule synergistic electrolyte engineering strategy utilizing a weakly solvating electrolyte (WSE) with dual additives—lithium nitrate (LiNO₃) and tris(pentafluorophenyl)borane (TPFPB). The molecular interactions between TPFPB and NO₃⁻ allow LiNO₃ to be effectively dissolved in DOX. Meanwhile, TPFPB coordinates with FSI⁻ anions to facilitate salt dissociation. These processes optimise the solvation structure towards contact ion pairs (CIPs) and aggregates (AGGs). Density functional theory (DFT) calculations and molecular dynamics (MD) simulations confirm that the solvation structure has been effectively optimized through the introduction of synergistic additives, which promotes the formation of inorganic-rich interfacial layers to protect both the anode and the cathode. Consequently, Li||LiFePO₄ cells maintain 98.14 % capacity retention over 480 cycles at 1 C. Moreover, a full battery assembled with high-loading LiNi_0.8Co_0.1Mn_0.1O₂ cathode (1.82 mAh cm⁻²) coupled with ultrathin Li anode (50 μm) retains 88.0 % capacity after 250 cycles under high-voltage operation (4.4 V). This work elucidates an ionic-molecular coordination paradigm for WSE design, providing insights into next-generation electrolyte engineering in practical high-energy-density lithium metal batteries. Furthermore, the proposed strategy holds broader implications for the development of other metal-based battery systems, including but not limited to Na, K, Mg, and Zn multivalent ion systems.