Pendulum-swing coordination boosting “liquid-like” Li-ion conduction within asymmetric lamellar fillers for solid polymer electrolytes

Abstract

Solid polymer electrolytes have shown great prospect in high-energy lithium-metal batteries, yet the most critical challenge is their unsatisfactory ionic conductivity. A common strategy involves the incorporation of symmetric lamellar fillers with ions/molecules fixed in interlayers. However, because of strong fixation, it sacrifices “liquid-like” flow properties as small-molecular solvents in polymer matrices. Herein, a novel concept of pendulum-swing coordination within interlayers is proposed to integrate advantages from both scenarios, based on the design of one-side fixation of solvents in asymmetric lamellar fillers. This delicate modulation of the coordination environment ensures the weakened Li+-solvent interaction and the strengthened anion-cation dissociation of lithium salts. More importantly, it enhances dynamic motion of the “hanged” solvents in highly-confined space, activating “liquid-like” Li-ion conduction. Meanwhile, the confined solvent does not plasticize polymer matrices, thus excellent mechanical property maintains. As a result, the developed electrolyte exhibits an impressive ionic conductivity of 1.35 × 10−4 S/cm at room temperature and exceptional anodic stability with stable Li stripping/platting cycles for over 2000 h. Solid-state Li-LiFePO4 batteries exhibit good rate behavior and remarkable capacity retention of 85.4% after 400 cycles at 0.5C. This work provides enlightening ideas for continuous development of high-performance polymer electrolytes towards real applications of lithium-metal batteries.