N-CNTs-Based Composite Membrane Engineered By A Partially Embedded Strategy: A Facile Route To High-Performing Zinc-Based Flow Batteries

Zinc-based flow batteries are promising for distributed energy storage due to their low-cost and high-energy density advantages. One of the most critical issues for their practical application is the reliability that results from the heterogeneous zinc deposition and dead zinc from falling off the electrode. Herein, nitrogen-doped carbon nanotubes (N-CNTs)-based composite membrane through a facilely partially embedded method is reported to enable a dendrite-free alkaline zinc-based flow battery. The results indicate that the electrically conductive N-CNTs functional layer can enhance the transport dynamics of charge carriers and homogenize electric field distribution in membrane–electrode interface, which induces the initial nucleation of metallic zinc from the carbon felt electrode to N-CNTs functional layer and further achieve a uniform and dense plating of metallic zinc in alkaline media. Thus, the engineered membrane enables a stable alkaline zinc–iron flow battery performance for more than 350 h at a current density of 80 mA cm⁻². Moreover, an energy efficiency of over 80% can be afforded at a current density of 200 mA cm⁻². The scientific finding of this study provides a new strategy on composite membranes design and their capability to adjust the plating of metallic zinc in alkaline media.