Three-dimensional porous carbon materials have great importance as electrode materials for vanadium redox flow batteries due to electrochemical stability over a wide potential window and low cost. However, sluggish electrode kinetics toward vanadium redox reactions makes electrode treatment vital before its use in a vanadium redox flow battery. Researchers have used different routes to modify the graphite electrode surface. This article presents a very simple (and known) but tactical procedure to treat a graphite felt. The modified electrode possesses large surface area having well-developed uniform pore structures and abundant oxygen-rich surface functional groups (11.2%), which offers a significant reduction in peak separation potential and charge-transfer resistance with a noteworthy improvement in the peak current density and redox reaction reversibility compared to a bare graphite felt. The modified graphite felt electrode enables 14-and 19-fold improvements in exchange current toward VO 2+ /VO 2 + and V 3+ /V 2+ redox reactions, respectively, than those of a bare graphite felt. The battery performance at 50 mA cm −2 of current density displays energy efficiency (89%) and electrolyte utilization (89%) nearly 12 and 98%, respectively, higher than that of a bare graphite felt. The long-term performance (200 cycles) of the battery assured stable behavior of the modified electrode. Moreover, the present modified approach improves the peak power density by 3-fold compared to that of the bare graphite felt.
Unique features of vanadium redox flow battery (VRFB), such as easy scalability and long durability, qualifies it as one of the prominent renewable energy storage technologies. Attracted by its features, scientific and commercial community around the globe have now begun to test prototypes/demonstrations of VRFB for a wide array of applications that deal at a scale of kW-MW. A few scientific groups have discussed the design and performance of kW-scale (up to 10 kW) VRFB in literature. It is interesting to note that the discussed designs have been developed with a diverse approach and have achieved different results. In this review, we critically examine and discuss those contributions at kW-scale VRFB by analyzing the materials associated with their design, understanding the development of the flow engineering aspects in order to tackle the pressure and shunt current losses and the overall electrochemical performance. Till date, kW-scale VRFB system has achieved an energy efficiency of ~80% at current densities of 100 mAÁcm À2 . Though the choice for majority of VRFB components is fixed, the right choice for its separator/membrane still needs to be standardized. With these aspects in picture, this review article will help to lay a background for researchers and engineers to know the present state-of-art and engineering issues at kW-scale VRFB, which is a building block for scaling up.
Attractive features of vanadium redox flow battery (VRFB) such as long durability, easy scalability, and low levelized cost of energy have influenced its prominence in the sectors where renewable energy is to be stored at a large scale. However, viability of VRFB to be used for a wide‐range of applications such as household electrification, electric vehicle charging infrastructure, and so on has been limited by its low power density. In principle, the power density of VRFB is dependent upon rate of electrochemical reaction on the electrode. The electrochemical properties of the electrode can be improved either by pretreatment of the electrode or by depositing electrocatalyst on the electrode. The use of electrocatalyst helps to lower overpotential losses and reduces the charge‐transfer resistance, which results the VRFB to operate at higher current densities. This review discusses the development and progress of carbon and metal‐based electrocatalyst that have been used for VRFB applications.
This article is categorized under:
Fuel Cells and Hydrogen > Science and Materials
Energy Efficiency > Science and Materials
Energy and Development > Science and Materials
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.