Dual membrane promises long-term energy storage..!

Source:Imperial College London

Dual membrane Technology

According to researchers at Imperial College London, the new method of battery design provides the key to low-cost, long-term energy storage.

 The team of engineers and chemists is not one, but has created a polysulfide-air redox flow battery (PSA RFB) with two membranes.

“Our dual-membrane approach is very exciting because it opens up many new possibilities.”       -Professor Nigel Brandon

Dual membrane design eliminates the main problems with this kind of large-scale battery, opening up the ability to store extra energy, for example, renewable sources such as wind and solar.  

In redox flow batteries, energy is stored in liquid electrolytes, which flow through the cells during charge and discharge, activated by chemical reactions.  The amount of energy stored is determined by the volume of the electrolyte, making the design efficiently easy to measure.

However, the electrolyte – vanadium – used in conventional redox flow batteries is expensive and is primarily sourced from China or Russia.

The problem to be solved

The Imperial team, led by professors Nigel Brandon and Anthony Kusernak, is working on alternatives to using widely available low-cost materials.  Their method uses liquid as an electrolyte and another gas – in this case polysulfide (dissolved sulphur in alkaline solution) and air.

^{The charging process}

However, the performance of polysulfide-air batteries is limited because no membrane can fully activate chemical reactions, but prevents the passage of polysulfide to the other side of the cell.

Dr Meng Jing Ouyang of Imperial’s Department of Earth Sciences and Engineering explained: “If the polysulfide crosses the air side, you lose material from one side, which reduces the reaction there and inhibits catalytic activity.  Others.  This reduces battery performance – so this is a problem we need to address.

An alternative, invented by the researchers, is to use two membranes to separate the polysulfide and air, the solution of sodium hydroxide between them.  The advantage of design is that all materials, including membranes, are relatively inexpensive and widely available, and the design provides more choice in usable materials.

^{Discharge of energy from the battery}

Determining Costs

The new design has been able to provide significantly more power, up to 5.8 milliwatts per centimetre, compared to the best results so far from the polysulfide-air redox flow battery.

Because cost is a critical factor for long-term and large-scale procurement, the team also conducted a cost analysis.  He calculated the cost of energy – the cost of storage materials relative to the amount of energy stored – about $ 2.5 per kilowatt hour.

The cost of electricity – the charge and discharge rate achieved in relation to the cost of membranes and catalysts in the cell – appears to be about $ 1600 per kilowatt.  The team believes that it is currently more than feasible for large-scale energy storage, but further improvements are easily achieved.

Professor Nigel Brandon, Dean of the Faculty of Engineering, said: “Our dual-membrane method is very exciting because it opens up many new possibilities for this and other batteries.

“To make it cost-effective for large-scale storage, a relatively modest improvement in performance is required, either by changes in the catalyst to increase its activity or by further improvements in the used membranes.”

Pressing need

Work in this area is already underway within the team, through the catalytic expertise of Professor Anthony Kusernak from the Department of Chemistry and the research of membrane technology by Dr Qilei Song from the Department of Chemical Engineering.

The spin-out company RFC Power Limited, which was established to develop long-term storage of renewable energy based on team research, is set to commercialise this new design if improvements are to be made.

Tim van Vern, CEO of RFC Power Ltd, said: “There is a need for new ways to store renewable energy for days, weeks or even months at a reasonable cost.

The research is funded by the UK Research and Innovation Engineering and Physical Sciences Research Council and the European Research Council.

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A cost-effective polysulfide-air redox flow battery activated by dual-membrane cell architecture by Yuhua Xia et al.  Published in Nature Communications.

Source Credit :

Materials provided by Imperial College London.  The original was written by Hayley Dunning. Communication section.