Can carbon sponge be used as separator in Li metal batteries

Abstract The high theoretical specific capacity and low redox potential endow lithium (Li) great promise to be used in the next generation rechargeable batteries. However, the safety issues and cycling degradation that are caused by dendrite growth and high reactivity of Li, impede the practical application of Li metal batteries. Herein, a strategy is reported to confine electrolyte in a nitrogen- and carboxyl-rich hollow carbon sponge reservoir. The hollow structure and its lithiophilicity help to mitigate the side reactions by containing the electrolyte. The carboxyl groups in the carbon sponge that can form hydrogen bond with 1,2-dimethoxyethane and thus alleviate the Li solvation and enhance the Li mobility, along with the lithiophilicity that controls Li distribution, substantially suppress dendrite growth. The limited Li solvation also reduces the parasitic reactions of solvent molecules on Li anode. With such carbon sponge electrolyte reservoir, the Li-Li cells can operate stably for over 4000 hours and Li-Cu cells exhibit Coulombic efficiency of ~99.3% after at least 800 cycles. The practical application of such reservoir is also demonstrated in Li-LiCoO2 and Li-S batteries.