Dual membrane offers hope for long-term energy storage

Date:
May 3, 2022
Source:
Imperial College London
Summary:
A new approach to battery design could provide the key to low-cost,
long- term energy storage, according to researchers.



FULL STORY ==========================================================================
A new approach to battery design could provide the key to low-cost,
long-term energy storage, according to Imperial College London
researchers.


==========================================================================
The team of engineers and chemists have created a polysulfide-air redox
flow battery (PSA RFB) with not one, but two membranes. The dual membrane design overcomes the main problems with this type of large-scale battery, opening up its potential to store excess energy from, for example,
renewable sources such as wind and solar. The research is published in
Nature Communications.

In redox flow batteries, energy is stored in liquid electrolytes which
flow through the cells during charge and discharge, enabled through
chemical reactions. The amount of energy stored is determined by the
volume of the electrolyte, making the design potentially easy to scale
up. However, the electrolyte used in conventional redox flow batteries
-- vanadium -- is expensive and primarily sourced from either China
or Russia.

The Imperial team, led by Professors Nigel Brandon and Anthony Kucernak,
have been working on alternatives that use lower cost materials which
are widely available. Their approach uses a liquid as one electrolyte and
a gas as the other -- in this case polysulfide (sulphur dissolved in an alkaline solution) and air. However, the performance of polysulfide-air batteries is limited because no membrane could fully enable the chemical reactions to take place while still preventing polysulfide crossing over
into the other part of the cell.

Dr Mengzheng Ouyang, from Imperial's Department of Earth Science and Engineering, explained: "If the polysulfide crosses over into the air
side, then you lose material from one side, which reduces the reaction
taking place there and inhibits the activity of the catalyst on the
other. This reduces the performance of the battery -- so it was a problem
we needed to solve." The alternative devised by the researchers was
to use two membranes to separate the polysulfide and the air, with a
solution of sodium hydroxide between them.

The advantage of the design is that all materials, including the
membranes, are relatively cheap and widely available, and that the design provides far more choice in the materials that can be used.



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When compared with the best results obtained to date from a
polysulfide-air redox flow battery, the new design was able to provide significantly more power, up to 5.8 milliwatts per centimetre squared.

As cost is a critical factor for long-term and large-scale storage,
the team also carried out a cost analysis. They calculated the energy
cost -- the price of the storage materials in relation to the amount of
energy stored -- to be around $2.5 per kilowatt hour.

The power cost -- the rate of charge and discharge achieved in relation
to the price of the membranes and catalysts in the cell -- was found
to be around $1600 per kilowatt. This is currently higher than would be feasible for large- scale energy storage, but the team believe further improvements are readily achievable.

Professor Nigel Brandon, who is also Dean of the Faculty of Engineering,
said: "Our dual-membrane approach is very exciting as it opens up many
new possibilities, for both this and other batteries. To make this cost effective for large-scale storage, a relatively modest improvement in performance would be required, which could be achieved by changes to
the catalyst to increase its activity or by further improvements in the membranes used." Work in this area is already underway within the team, through the catalyst expertise of Professor Anthony Kucernak, from the Department of Chemistry, and research into membrane technology by Dr
Qilei Song from the Department of Chemical Engineering.

The spin-out company RFC Power Ltd, established to develop long-duration storage of renewable energy based on the team's research, is set to commercialise this new design should the improvements be made.

CEO of RFC Power Ltd, Tim Von Werne, said: "There is a pressing need
for new ways to store renewable energy over days, weeks or even months
at a reasonable cost. This research shows a way to make that possible
through improved performance and low-cost materials." The research is
funded through the UK Research and Innovation Engineering and Physical
Sciences Research Council, and the European Research Council.


========================================================================== Story Source: Materials provided by Imperial_College_London. Original
written by Hayley Dunning. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Yuhua Xia, Mengzheng Ouyang, Vladimir Yufit, Rui Tan, Anna Regoutz,
Anqi
Wang, Wenjie Mao, Barun Chakrabarti, Ashkan Kavei, Qilei Song,
Anthony R.

Kucernak, Nigel P. Brandon. A cost-effective alkaline
polysulfide-air redox flow battery enabled by a dual-membrane
cell architecture. Nature Communications, 2022; 13 (1) DOI:
10.1038/s41467-022-30044-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220503141342.htm

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