With a number of advantages over other existing energy storage system (ESS) including flexibility, mobility, depth of discharge, rapid response, and safety, redox flow batteries (RFB) are one of the most promising and versatile options for grid scale energy storage, potentially enabling the integration of intermittent but growing fast renewable energy sources into power grids. RFB represent one class of electrochemical ESS and have been attracting attention over last two decades. Several chemistries of RFBs have been studied. However none of them fully meet the cost and performance requirements. Significant developments are required at all levels: investigation of new chemistries, materials engineering, cell design and long-term performance characterization in realistic environments.

This project will investigate an innovative RFB system based on nickel and zinc redox couples. The zinc-nickel system is promising due to the low cost and material abundance of its redox couples, their environmentally acceptable chemistry, high standard electrode potential and high power and energy densities. The scope of this project is on the improvement of materials and engineering design, combined with advanced characterisation techniques and computational modelling to gain fundamental insights and accelerate progress towards a high-performance, durable cell design. The programme will be focused on ways to improve the morphology of thick zinc electrodeposits when subjected to multiple deposition/dissolution cycles, and methods to increase the charge capacity of the positive electrode in flowing electrolyte conditions.

In addition, the system is a membrane-free flow battery, which differs from conventional flow battery technologies since it employs only a single electrolyte and therefore operates without a need in membrane separator; this reduces the cost and design complexity of the batteries significantly. Overall, the performance of the Zn-Ni battery should compare well with existing redox flow batteries.

The project will be a collaborative research endeavour between highly experienced researchers with internationally recognised expertise in flow batteries from the University of Exeter, Imperial College London and the University of Warwick.

Potential Impact:
The project is based on substantial pre-existing activities of redox flow battery (RFB) research and development between the universities of Exeter, Imperial, and Warwick. We have now reached the stage where investment from EPSRC will significantly accelerate the research. Outputs from the project will contribute significantly towards the future energy mix of the UK, as well as Europe and beyond.

The project research will focus on the ultimate goal of developing a marketable, scalable zinc-nickel flow battery concept, capable of meeting energy storage needs from kW to MW scales. The research therefore has the potential to make a significant contribution to the development of the emerging energy storage industry in the UK. More generally, through its contribution to the continued viability of the UK's energy infrastructure, the research has the potential to contribute to the national economy as a whole.

One direct impact is that renewable energy sectors will be benefited from the zinc-nickel flow battery. Two energy storage companies, WhEST and C-Tech Innovation, are significantly interested in the research direction and will be involved in developing and realising effective routes towards exploitation.

Outcomes of the project will be reported in peer-reviewed scientific journals targeting J Power Sources, Energy & Environ Sci, and Electrochem Commun etc. and presented at major international and national conferences such as International Flow Battery Forum and International Society of Electrochemistry. The dissemination of the results will assist the wider academic community including materials scientists, electrochemists and chemical engineers. Additionally, there will be the opportunity to communicate the findings of the research at various seminars and workshops.

Exploitable results or innovations arising from the programme of work will be managed by the Research & Knowledge Transfer teams at the University of Exeter, Imperial, and Warwick, who have significant experience in such matters.

The successful build-up of a demonstration of this battery will provide undergraduate and postgraduate students with an opportunity to gain first-hand experience in the field of energy storage technology. The PDRAs and a PhD student working on this project will acquire a range of technical skills in RFBs field and these skills which are highly valued by practitioners will enable them to contribute to energy storage technology in the future.