Two-dimensional MoS2 nanosheets constructing highly ion-selective composite membrane for vanadium redox flow battery

A novel double-layer composite membrane with a MoS 2 -rich layer and a polymer-rich layer is prepared by the method of one-step slow solvent evaporation for vanadium redox flow batteries. The composite membrane is composed of MoS 2 nanosheets as protecting layer, providing the membrane with lower VO 2+ permeability and excellent chemical stability, and sulfonated modified PBI as substrate, providing high proton conductivity. The introduction of MoS 2 nanosheets greatly reduces the area resistance of the PBI-PS/MoS 2 membrane (0.42 Ω cm 2 ), which is comparable to that of Nafion 212 (0.41 Ω cm 2 ). The cell equipped with PBI-PS/MoS 2 membrane presents improved coulombic efficiencies and energy efficiencies. At 200 mA cm −2 , a high EE of about 80% is achieved. The cell maintains stable performances for nearly 800 cycles, showing impressive durability. The cell also shows a self-discharge rate of as low as 0.0021 V h −1 . The MoS 2 nanosheets layer based composite membrane is promising for VRBs. • The composite membrane composed of MoS 2 -rich layer and polymer-rich layer is designed for flow battery. • The MoS 2 nanosheets with two-dimensional structure achieve high proton-selective conduction. • Cell with the membrane shows high and stable performances during 800 cycles.