A cost-effective nafion/lignin composite membrane with low vanadium ion permeation for high performance vanadium redox flow battery

Here we report an eco-friendly Nafion/lignin composite membrane with excellent performance for vanadium redox flow battery (VRFB). Through facile solution casting, the Nafion/lignin composite membrane presents the merits of high conductivity and low vanadium ions permeability. Under high current density (120 mA cm−2), the VRFB single cell with the optimized Nafion/lignin composite membrane exhibits superior performance metrics to commercial counterpart: high Coulombic efficiency (~97.4%) and energy efficiency (~82.7%), and prominent cyclability with slower capacity decay for ~52.8% capacity retention after 1000 cycles (vs. Nafion 212 membrane ~34.8% after only 150 cycles). More importantly, compared with the pristine Nafion 212 membrane, the cost of the composite membrane is reduced sharply by reducing the usage amount of Nafion polymer, while maintaining the membrane stability. Thus, the Nafion/lignin composite membrane is one of the competitive candidates for VRFB towards commercialization. [Display omitted] •A cost-effective Nafion/lignin composite membrane is fabricated.•The Nafion/lignin membrane shows lower vanadium ion permeability than Nafion 212.•The VRFB shows ultra-long cycle life with ultra-low capacity decay rate.