Tunable Nanoscale Interlayer of Graphene with Symmetrical Polyelectrolyte Multilayer Architecture for Lithium Extraction

Graphene, a 2D sp2‐hybridized carbon sheet is a hot topic in the fields of materials science and chemistry. Here, a symmetrical multilayer architecture of graphene is designed by grafting of sulfonated 4,4′‐ diaminodiphenyl sulfone (SDDS) with the ample sulfonate groups and tunable interlayer spacing to exhibit the Li+ extraction from ionic mixtures with Na+, Mg2+ and Ca2+. Under the application of an electric field, the selective separation of cations can be achieved by controlling the flow channels of negatively charged ions (≈0.48 nm) during the synthesis of rGO‐SDDS‐rGO membrane. The result shows that the ion selectivity of the rGO‐SDDS‐rGO membrane is Na+ > Li+ > Ca2+ > Mg2+ and the absolute separation efficiency values of Li+/Mg2+ and Li+/Ca2+ are as high as 85.32 and 80.81%, respectively.