Inorganic fillers tailored Li+ solvation sheath for stable lithium metal batteries

Abstract

Ionogel electrolytes based on gel scaffolds and ionic liquids (ILs) have garnered widespread attention for their processing compatibility, non-flammability, and exceptional thermal/electrochemical properties. While there have been many studies demonstrating the effectiveness of the bisalt approach in stabilizing lithium metal anode, the precise impact of skeleton-constrained dual-anion ionogels on interface modulation remains somewhat obscured and deserves further attention. Herein, we formulate a Li6.4La3Zr1.4Ta0.6O12 (LLZTO)-incorporated dual-anion ionogel to reveal the solvation chemistry in the presence of LLZTO and detail the Li+ transport mechanism and effect on the interfacial chemistries of Li-metal. The impact of inorganic substances on the solvation structure in IL-based solid electrolytes and their role in forming the SEI layer on lithium metal was unveiled. To be specific, the introduction of fillers exert a selective modulating influence on the anions species in the Li+-solvated shell and fine-tunes the local Li+ environment, thereby fostering a more robust interfacial layer. Modified ion environment in ionogels enables a preferable shift from vehicular to structural Li+ transport, whereby a high Li ion conductivity (1.24×10−3 S/cm) and high Li ion transference number of 0.42 is achieved. The synergistic solvent coordination and adjustment of the electrode-electrolyte interface enable the LiFePO4|PIL-10|Li cells to cycle steadily with capacity retention of 95.4 % after 500 cycles at 1C and 25 °C. The strategy of promoting transport mechanisms holds promise for designing the next-generation solid-state lithium metal batteries with high energy density.