Unveiling the Role of Heteroatoms Gradient-Distributed Carbon Fibers for Vanadium Redox Flow Batteries with Long Service Life.

The fundamental understanding of electrocatalytic reaction process is anticipated to guide electrodes upgradation and acquirement of high-performance vanadium redox flow batteries (VRFBs). Herein, a carbon-fiber prototype system with a heteroatom gradient distribution has been developed with enlarged interlayer spacing and a high graphitization that improve the electronic conductivity and accelerate the electrocatalytic reaction, and the mechanism by which gradient-distributed heteroatoms enhance vanadium redox reactions was elucidated with the assistance of density functional theory calculations. All these contributions endow the obtained electrode prominent redox reversibility and durability with only 1.7% decay in energy efficiency (EE) over 1000 cycles at 150 mA cm in the VRFBs. Our work sheds light on the significance of elaborated electrode design and impels the in-depth investigation of VRFBs with long service life.