ZSM-5 Membranes Fabricated through Template-Free Gel for Energy Storage

Vanadium flow battery (VFB) shows great potential in balancing the volatility of renewable energy. In this work, we investigated, for the first time, the various properties of crystalline ZSM-5 membranes prepared through the organic template-free gel strategy in VFB. The subnano windows (∼0.55 nm) of ZSM-5 zeolite provided selective transport paths for protons (∼0.27 nm) and blocked the vanadium (>0.6 nm) migration through pore repulsion effect. The zeolite membranes exhibited a very low vanadium penetration rate (0.05 mmol L–1 h–1), achieving a Coulombic efficiency (CE) of 96.1%, a voltage efficiency of 78.3%, and an energy efficiency of 75.3% at the current density of 40 mA cm–2. Notably, ZSM-5 prepared using the template-free strategy eliminates the need for a high-temperature calcination step, and the membrane has a lower defect density and exhibits a higher CE. The self-discharge time of the ZSM-5 zeolite membrane increased up to 78 h. Furthermore, the charge–discharge performance kept stable more than 300 cycles at 60 mA cm–2.