In situ catalytic polymerization of LiNO3-containing PDOL electrolytes for high-energy quasi-solid-state lithium metal batteries

Abstract

1,3-Dioxolane (DOL) can be induced to form polymer electrolytes by in situ ring opening polymerization at Lewis acid salts. However, the presence of ion–dipole interactions between NO₃⁻ and DOL suppresses this polymerization behavior. Herein, we report that the use of Sc(OTf)₃ as an initiator can well disrupt this ion–dipole interaction. The in situ ring-opening polymerization of DOL is achieved to form a LiNO₃-modified polyDOL-based electrolyte. New mechanism of Li migration in polymer electrolytes have been revealed by molecular dynamics modeling and constructed molecular interface models. It is found that the electrolyte interior is affected by the ion–dipole interactions of Li⁺ by NO₃⁻, which made it easier for Li⁺ to be released from the polar ether-oxygen ligands on the polymer chain for rapid migration, thus exhibiting an ionic conductivity of 1.8 mS cm⁻¹ and $t_{{\mathrm{Li}}^{+}}$ of 0.78. In addition, NO₃⁻ preempts the binding sites around Li⁺, improves the coordination environment, and prioritizes the formation of a kinetically stable anion-derivative interface, which effectively mitigates the interfacial side reactions between the electrodes and the electrolytes. As a result, the assembled solid-state Li||LiFePO₄ cell exhibits an impressive 152.3 mAh/g discharge capacity at 0.5C and maintains 80.3 % of the capacity after 450 cycles at 50 °C. This work not only opens a new avenue for designing high-performance gel polymer electrolytes for more metal-based batteries, but also provides valuable insights into understanding the ion migration mechanism.