Hierarchical carbon chain network ‘armor’ escorts long-term cycling stability for vanadium redox flow batteries

Abstract

Nowadays, the bottleneck constraining the development of electrode materials for all-vanadium flow batteries lies in their poor performances at high current densities. Pertinently, we propose a high-stability hierarchical N and S co-doped carbon chain network ‘armor’ strategy to achieve long-term stability enhancement for electrodes. It is found that hierarchical carbon chain network can effectively enhance the voltage efficiency, energy efficiency, and long-term cycling stability for all-vanadium flow batteries. The modified electrode presents superior long-term stability over 1900 cycles, and the energy efficiency is maintained at about 80 % at 180 mA cm−2. In addition, the energy efficiency can also reach over 70 % at 320 mA cm−2, while at 280 mA cm−2 the modified electrode can circulate stably for over 800 turns. It is proved that the bridging effect of polydopamine facilitates the stable carbon chain network, and effectively regulates the N and S co-doping, further constructing the N and S co-doping sites to assemble electrochemical catalytic network. More importantly, the carbon chain network ‘armor’ design can effectively prevent electrode breakage. This work provides a reference way for the design of long-term stable electrodes, which is of great significance for advancing commercial applications of all-vanadium flow batteries.