A high selective membrane based on SPEEK and sulfonated lignin-modified GO for vanadium redox flow batteries

Addressing the membrane’s dilemma between H⁺ conduction and Vⁿ⁺ ion crossover is a challenge for developing the vanadium redox flow batteries (VRFBs). Herein, we developed a series of composite membranes by incorporating sulfonated lignin-modified graphene oxide (GO@SL) into sulfonated polyether ether ketone (SPEEK). The GO@SL effectively improves H⁺ conduction and Vⁿ⁺ ion resistance of the SPEEK/GO@SL. Relative to the pure SPEEK, the SPEEK/GO@SL composite membranes exhibit higher selectivity (144.8 × 10³ S min cm⁻³). The SPEEK/GO@SL-2 exhibits a higher energy efficiency (81.2% at 100 mA cm⁻²) and excellent stability. This work validates the significant potential of the GO@SL composite for crafting next-generation ion exchange membranes, offering a promising strategy to overcome the conductivity-permeability trade-off.