Low‐Carbon‐Content Composite Bipolar Plates: A Novel Design and Its Performance in Vanadium Redox Flow Batteries

Bipolar plates possessing both high electrical conductivity and mechanical strength has been urgently required for redox flow batteries and fuel cells. Contrary to the conventional method of increasing carbon content to maximize the bipolar plate's electrical conductivity, a novel low‐carbon‐content design based on the bridging effect of graphene is developed. The microstructure, electrical conductivity, flexural strength, vanadium permeability, corrosion current density and its performance in vanadium redox flow battery single cell have been investigated. The low‐carbon‐content bipolar plates present both high electrical conductivity and flexural strength. Low area specific resistance of 3.3 mΩ cm2 is reached at 18.7 wt.% carbon content, and flexural strength of 48.1 MPa can be obtained after being reinforced by carbon fibers. The voltage efficiency and energy efficiency of the single cell reach as high as 88.6% and 85.7%, respectively, at 100 mA cm−2. To be a better plate: Due to the bridging effect of graphene, the low‐carbon‐content bipolar plate presents ultra‐high electrical conductivity, as well as superior energy efficiency when is applied in the vanadium redox flow battery. The homemade bipolar plate also shows zero vanadium permeability and good corrosion resistance, and its flexural strength can be significantly enhanced by adding a small amount of carbon fiber