Fe2O3 Nanoparticle Interfacial Reaction Redistributing Li-Ion Flux in Flexible Hierarchically Porous Membrane Electrodes for Dendrite-Free Lithium Metal Batteries

Abstract

The uncontrollable formation of Li dendrites and the problems arising from it are the major obstacles in the practical application of Li metal batteries. Thereby, it is crucial to induce the uniform dispersion and deposition of Li+. To realize it, we constructed a flexible membrane electrode that facilitated Li+ dispersion by the interwoven conductive porous skeleton and simultaneously promoted Li+ deposition with doped active sites. The skeleton was composed of CNTs cross-linked with polyvinylidene fluoride (PVDF), which ensured the good conductivity and flexibility of membrane, and the −CF2 groups on PVDF chains also accelerated the migration of Li+. The doped Fe2O3 with strong lithiophilicity played a vital role in Li+ deposition. Quasi in situ X-ray photoelectron spectroscopy and in situ X-ray diffraction measurements were employed to reveal the reaction mechanism that Fe2O3 could be partially reduced by Li+ forming LixFe alloy, and reoxidized to amorphous Fe2O3. According to the galvanostatic current test of symmetric battery, the voltage had no significant changed after 1500 h, which proved that multifunctional membrane electrode effectively reduced the effect of Li dendrites. The assembled coin battery delivered an initial capacity of 125.9 mA h g–1 and still maintained at 114.9 mA h g–1 after 200 cycles at 0.5 C, with a capacity decay rate of only 0.048% per cycle. The pouch cell also exhibited excellent cycling stability with a Coulombic efficiency of >99.2% after 70 cycles at 0.5 C. This work provides a novel flexible membrane electrode design in solving the Li dendrites and developing novel electrodes for Li metal batteries.