Advanced Nanoporous Separators for Stable Lithium Metal Electrodeposition at Ultra-High Current Densities in Liquid Electrolyte
Lithium metal anode forms dendritic structure after cycling which causes the internal short circuit in flammable electrolytes and results in battery fires. Today’s separators are insufficient for suppressing the formation of lithium dendrite. Herein, we report on our use of mesoporous silica thin film (MSTF) with perpendicular nanochannels (pore size ~ 5 nm) stacking on anodic aluminum oxide (AAO) membrane as the MSTF/AAO separator for advancing Li metal batteries. The nanoporous MSTF/AAO separator with novel inorganic structures shows ultra-long term stability of Li plating/stripping in Li-Li cells under an ultra-high current density and capacity (10 mA cm–2 and 5 mAh cm–2). A significant improvement over the state-of-the-art separator is evaluated in three performance indicators, e.g. cycle life, current density and capacity. In Li-Cu cells, MSTF/AAO separator shows Coulombic efficiency of >99.9% at a current density of 10 mA cm–2 for more than 250 h of cycling. The separator gives improved rate capability in Li-LiFePO4 (LFP) batteries. The excellent performance of MSTF/AAO separator is due to good wetting of electrolytes, straight nanopores with negative charges, uniform Li deposition and blocking the finest dendrite.