Electroless plating on porous carbon felts in redox flow batteries and thickness effect on the electrical and mechanical properties

Redox-flow batteries, in particular vanadium redox flow battery (VRB), are receiving intensive attention due to their ability to store large amounts of electrical energy in a relatively cheap and efficient scenario. One of the key components in VRB is carbon felt, which serves as the liquid diffusion layers (LDL) and differentiates distinctively from the gas diffusion layers (GDL) in proton exchange membrane fuel cell (PEMFC) such that the thickness LDL is in mm range, whereas GDL is only 1/5 - 1/10 of it. One reason for a significantly thick carbon felt is due to the enhancement of diffusion length for the VRB while the associated resistance should be minimized. While the thickness of LDL plays the role of stress absorber and maintains the conductivity and the electrical contacts, the durability of the MEA is reasonably safeguarded. This paper adopts a new Ni plating carbon felt and the effect of plating thickness on mechanical, electrical and morphological properties are also discussed. Experimental results show that the nickel coated carbon felt prepared by electroless plating was successfully applied and a drastically reduced ASR of 50% can be obtained under 40% compression, while the stress-strain curve, residual strain and porosity basically remain unchanged. The nickel coated carbon felt is a promising electrode material for VRB application.