Flexible Carbon Sponge Electrodes for All Vanadium Redox Flow Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Vanadium redox flow batteries (VRFBs) are crucial for grid-scale energy storage.
• Electrode materials significantly impact VRFB performance and cost.
• Graphite felt is a common but suboptimal electrode material.

Purpose of the Study:

• To investigate a flexible carbon sponge as a high-performance electrode for VRFBs.
• To compare the performance of carbon sponge electrodes against traditional graphite felt electrodes.
• To explore methods for further enhancing the carbon sponge electrode's efficiency.

Main Methods:

• Fabrication of carbon sponge electrodes by direct carbonization of melamine formaldehyde resin.
• Experimental characterization of the carbon sponge's structure and properties.
• Performance testing of VRFBs using carbon sponge electrodes at various current densities.
• Post-treatment of carbon sponge electrodes via thermal treatment in air.

Main Results:

• The carbon sponge electrode exhibits a 3D bi-continuous architecture with 99.6% porosity.
• VRFBs with carbon sponge electrodes achieved 77.9% energy efficiency at 200 mA cm⁻², outperforming graphite felt (72.9%).
• Air thermal treatment improved energy efficiency to 81.2% due to oxygen functionalities.
• Carbon sponge electrodes demonstrated stable operation over 200 cycles with minimal efficiency loss.

Conclusions:

• Flexible carbon sponge is a promising, cost-effective alternative electrode for advanced VRFBs.
• Carbon sponge electrodes offer superior energy efficiency and stability compared to graphite felt.
• Surface functionalization via air treatment can further boost the performance of carbon sponge electrodes.