Ultra-high energy density redox flow batteries

38758467-1ff3-41e8-8fae-1e8ca83b8adc

Closed

EPSRC
NERC
NERC
NERC
NERC

No funds listed.

Sept. 30, 2017

Dec. 31, 2021

Redox flow batteries (RFBs) are a unique design of rechargeable energy storage device that can be readily scaled to meet various grid needs. They offer a promising solution to stabilise the national grid from the intermittent output of renewable sources. Effective grid scale energy storage from RFBs will support the transfer of electricity production from fossil fuel burning to low carbon renewable sources.

RFBs differ from conventional batteries in that they store electrical energy in their redox active electrolytes. The electrolyte is contained in reservoirs external to the cell and is pumped via electrodes that permit charge/discharge to occur. This provides the unique advantage of decoupling battery capacity and power, enabling RFBs to be more easily modified for grid scale to microgrid applications.

Traditional RFBs are composed of redox active material, typically metals, dissolved in aqueous solvent at maximum concentrations of 3 mol dm-3. A large proportion of the electrolyte is composed of redox inactive solvent that limits the energy density to <50 Wh dm-3 which is substantially lower than today's lithium-ion batteries at >200 Wh dm-3. The low energy density of current RFBs has been highlighted as a key barrier to further market penetration. Boosting the energy density could see RFBs transforming the existing energy storage sector currently reliant on lithium ion technology.

Proposed solution and methodology

Here, we propose a novel design of redox electrolyte with a step change in energy density. Integration of redox species into ionic liquids produces redox active ionic liquids. Electrolytes based on these so called 'redox liquids' have a substantial increase in concentration of redox centres compare to conventional electrolyte systems. In addition, to further maximise energy storage capacity, we are investigating the use of redox active materials capable of accepting multiple electrons per molecule. Polyoxometalates (POMs) are metal oxide clusters composed of transition metals in high oxidation states. POMs are capable of highly reversible multi-electron redox processes and are promising candidates for battery applications. Boosting energy density through re-design of the redox electrolyte may lead to the use of RFBs in small-scale and mobile applications.

Proposed solution and methodology

Here, we propose a novel design of redox electrolyte with a step change in energy density. Integration of redox species into ionic liquids produces redox active ionic liquids. Electrolytes based on these so called 'redox liquids' have a substantial increase in concentration of redox centres compare to conventional electrolyte systems. In addition, to further maximise energy storage capacity, we are investigating the use of redox active materials capable of accepting multiple electrons per molecule. Polyoxometalates (POMs) are metal oxide clusters composed of transition metals in high oxidation states. POMs are capable of highly reversible multi-electron redox processes and are promising candidates for battery applications. Boosting energy density through re-design of the redox electrolyte may lead to the use of RFBs in small-scale and mobile applications.

Potential Impact:
This CDT will have a positive impact in the following areas:

PEOPLE. The primary focus is people and training. Industry needs new approaches to reach their sustainability targets and this is driving an increasing demand for highly qualified PhD graduates to lead innovation and manage change in the area of chemicals production. CDT based cohort training will provide industry ready scientists with the required technical competencies and drive to ensure that the sector retains its lead position in both innovation and productivity. In partnership with leading chemical producers and users, we will provide world class training to satisfy the changing needs of tomorrow's chemistry-using sector. Through integrated links to our Business School we will maximise impact by delivering dynamic PhD graduates who are business aware.

ECONOMY. Sustainability is the major issue facing the global chemical industry. Not only is there concern for our environment, there is also is a strong economic driver. Shareholders place emphasis on the Dow Jones Sustainability Index that tracks the performances of the sector and engenders competition. As a result, major companies have set ambitious targets to lower their carbon footprints, or even become carbon neutral. GSK CEO Sir Andrew Witty states that "we have a goal to reduce our emissions and energy use by 45% compared with 2006 levels on a per unit sales basis... " Our CDT will help companies meet these challenges by producing the new chemistries, processes and people that are the key to making the step changes needed.

SOCIETY. The diverse range of products manufactured by the chemical-using industries is vital to maintain a high quality of life in the UK. Our CDT will have a direct impact by ensuring a supply of people and new knowledge to secure sustainability for the benefit of all. The role of chemistry is often hidden from the public view and our CDT will provide a platform to show chemical sciences in a positive light, and to demonstrate the importance of engineering and applications across biosciences and food science.
The "green and sustainable" agenda is now firmly fixed in the public consciousness, our CDT will be an exemplar of how scientists and engineers are providing solutions to very challenging scientific and technical problems, in an environmentally benign manner, for the benefit of society. We will seek sustainable solutions to a wide range of problems, whilst working in sustainable and energy efficient facilities. This environment will engender a sustainability ethos unique to the UK. The CNL will not only serve as a base for the CDT but also as a hub for science communication.
Public engagement is a crucial component of CDT activities; we will invite input and discussion from the public via lectures, showcases and exhibition days. The CNL will form a hub for University open days and will serve as a soft interface to give school children and young adults the opportunity to view science from the inside. Through Dr Sam Tang, public awareness scientist, we have significant expertise in delivering outreach across the social spectrum, and she will lead our activities and ensure that the CDT cohorts engage to realise the impact of science on society. Martyn Poliakoff, in his role as Royal Society Foreign Secretary, will ensure that our CDT dovetails with UK science policy.

KNOWLEDGE. In addition to increasing the supply of highly trained people, the results of the PhD research performed in our CDT will have a major impact on knowledge. Our student cohorts will tackle "the big problems" in sustainable chemistry, and via our industrial partners we will ensure this knowledge is applied in industry, and publicised through high level academic outputs. Our knowledge-based activities will drive innovation and economic activity, realising impact through creation of new jobs and securing the future.