All power to the proton: Researchers make battery breakthrough

All power to the proton: RMIT researchers make battery breakthrough
The RMIT-developed proton battery connected to a voltmeter. The working prototype has an energy per unit mass already comparable with commercially-available lithium ion batteries. Credit: RMIT University

Researchers from RMIT University in Melbourne, Australia have demonstrated for the first time a working rechargeable "proton battery" that could re-wire how we power our homes, vehicles and devices.

The is environmentally friendly, and has the potential, with further development, to store more energy than currently-available lithium ion batteries.

Potential applications for the proton include household storage of electricity from solar photovoltaic panels, as done currently by the Tesla 'Power wall' using lithium ion batteries.

With some modifications and scaling up, proton battery technology may also be used for medium-scale storage on electricity grids - - like the giant lithium battery in South Australia—as well as powering electric vehicles.

The working prototype proton battery uses a as a store, coupled with a reversible fuel cell to produce electricity.

It's the carbon electrode plus protons from water that give the proton battery it's environmental, energy and potential economic edge, says lead researcher Professor John Andrews.

"Our latest advance is a crucial step towards cheap, sustainable proton batteries that can help meet our future energy needs without further damaging our already fragile environment," Andrews said.

"As the world moves towards inherently-variable renewable energy to reduce greenhouse emissions and tackle climate change, requirements for electrical energy storage will be gargantuan.

"The proton battery is one among many potential contributors towards meeting this enormous demand for energy storage. Powering batteries with protons has the potential to be more economical than using lithium ions, which are made from scare resources.

"Carbon, which is the primary resource used in our proton battery, is abundant and cheap compared to both metal hydrogen-storage alloys, and the lithium needed for rechargeable lithium ion batteries."

During charging, the carbon in the electrode bonds with protons generated by splitting water with the help of electrons from the power supply. The protons are released again and pass back through the reversible fuel cell to form water with oxygen from air to generate power. Unlike fossil fuels, the carbon does not burn or cause emissions in the process.

All power to the proton: RMIT researchers make battery breakthrough
Professor John Andrews (centre) with the RMIT team that conducted the latest proton battery experiments: Dr Shahin Heidari (left) and Saeed Seif Mohammadi (PhD researcher, right). Not pictured: Dr Amandeep Singh Oberoi (now at Thapar University Patiala, India). Credit: RMIT University

The researchers' experiments showed that their small proton battery, with an active inside surface area of only 5.5 square centimetres, was already able to store as much energy per unit mass as commercially-available lithium ion batteries. This was before the battery had been optimised.

"Future work will now focus on further improving performance and energy density through use of atomically-thin layered carbon-based materials such as graphene, with the target of a proton battery that is truly competitive with lithium ion batteries firmly in sight," Andrews said.

RMIT's research on the proton battery has been partly funded by the Australian Defence Science and Technology Group and the US Office of Naval Research Global.

How the proton battery works

The working prototype proton battery combines the best aspects of hydrogen fuel cells and battery-based electrical power.

The latest version combines a carbon electrode for solid-state storage of hydrogen with a reversible fuel cell to provide an integrated rechargeable unit.

The successful use of an electrode made from activated carbon in a proton battery is a significant step forward and is reported in the International Journal of Hydrogen Energy.

During charging, protons produced by water splitting in a reversible fuel cell are conducted through the cell membrane and directly bond with the storage material with the aid of electrons supplied by the applied voltage, without forming hydrogen gas.

In electricity supply mode this process is reversed; hydrogen atoms are released from the storage and lose an electron to become protons once again. These protons then pass back through the cell membrane where they combine with oxygen and electrons from the external circuit to re-form water.

A major potential advantage of the proton battery is much higher energy efficiency than conventional hydrogen systems, making it comparable to lithium ion batteries. The losses associated with hydrogen gas evolution and splitting back into protons are eliminated.

Several years ago the RMIT team showed that a proton battery with a metal alloy electrode for storing hydrogen could work, but its reversibility and rechargeability was too low. Also the alloy employed contained rare-earth elements, and was thus heavy and costly.

The latest experimental results showed that a porous activated-carbon electrode made from phenolic resin was able to store around 1 wt% hydrogen in the electrode. This is an per unit mass already comparable with commercially-available lithium ion batteries, even though the battery is far from being optimised. The maximum cell voltage was 1.2 volt.


Explore further

Proton flow battery advances hydrogen power

More information: Shahin Heidari et al, Technical feasibility of a proton battery with an activated carbon electrode, International Journal of Hydrogen Energy (2018). DOI: 10.1016/j.ijhydene.2018.01.153
Provided by RMIT University
Citation: All power to the proton: Researchers make battery breakthrough (2018, March 7) retrieved 21 October 2018 from https://techxplore.com/news/2018-03-power-proton-battery-breakthrough.html
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Mar 07, 2018
Seems like this has some nice scaling properties. The fuel cell would be sized based on the desired current draw or recharging time (recharging current.) I suspect the later might predominate. The amount of carbon electrode storage material would be determined by the desired storage capacity. I guess one thing to be careful about is to minimize the amount of free hydrogen in the device.

Mar 07, 2018
I can see some low voltage uses for those. Especially for electronics.

Mar 07, 2018
It's a rehash of a known technology:

https://en.wikipe..._battery

"The nickel-hydrogen battery combines the positive nickel electrode of a nickel-cadmium battery and the negative electrode, including the catalyst and gas diffusion elements, of a fuel cell. During discharge, hydrogen contained in the pressure vessel is oxidized into water while the nickel oxyhydroxide electrode is reduced to nickel hydroxide."


The energy density is about 75 Wh/kg for the Ni-H battery.

Hydrogen has an energy density of 33 kWh/kg so the new carbon material that returns 0.8%/wt gets 264 Wh/kg - but that figure drops lower when you consider the efficiency losses and the added mass of the packaging.

Commercial lithium batteries come around 250 wh/kg.

Mar 07, 2018
"I can see some low voltage uses for those. Especially for electronics."


This type of battery is already used in satellites, because of its long cycle life and practically unlimited shelf-life. The disadvantages are that the hydrogen tends to recombine inside the cell, leading to high self-discharge and energy retention times measured in only days. If the carbon variety behaves similiarily to the nickel version, your 'proton battery' cellphone would run out of charge in three days regardless of use.

Which isn't a problem in a satellite which gets sunlight on its solar panels every couple hours as it goes around.

Mar 07, 2018
For example, the Hubble space telescope had a Ni-H battery operational for 19 years before it was replaced - still working. The orbital period of the telescope was 97 minutes, so during that time the current to/from the batteries was reversed about 100,000 times which is pretty incredible even if you only discharge it to a shallow depth of discharge like 20% which is still equivalent to 20,000 full discharges. Lithium batteries would last only up to 2,000.

The ISS also has Ni-H batteries.

Likewise, in comparison, Tesla estimates the lifespan of its Supercharger stations to be 12 years before overhaul is needed on the batteries - the same lithium batteries it uses in its cars, and the Australian megabattery. That's part of the reason why lithium batteries are unsuitable for grid balancing.

Mar 07, 2018
Nice thing about 'vanilla' NiMH batteries is they were 'plug compatible' with NiCads, so you could keep legacy equipment going by just switching their pen-cells. There's a zoo of Li-ion batteries that are less amenable...

Again, this C-H chemistry would suit 'hybrid' power supplies, with super-capacitors for peak power...

Mar 08, 2018
If i had a dollar for every battery advancement announced to no avail over the decades i'd be a millionare today.

Mar 08, 2018
This sounds promising but don't quite fully understand their explanation of how it works.
It says;

"...During charging, the carbon in the electrode bonds with protons generated by splitting water..."

Protons are hydrogen nuclei.
Now, and I think I may risk looking like a fool by asking this so please be gentle with me, when they say the carbon 'bonds' with protons, do they mean 'bonds' as in forming covalent bonds so to change the carbon into hydrocarbon and with an electron orbital around each proton?
If so, because of the Gibbs function in relation to chemical bonds, I would be surprised if it could have much energy density.
Or do they mean some kind of ionic bond with the carbon so that there is no electron orbitals around each proton?
If so, how on earth can that work when carbon doesn't readily form ionic bonds?
What am I missing here?

Mar 08, 2018
The paper compares the energy density of the hydrogen storage element (activated carbon with a binder) to the energy density of whole batteries. Even if the packaging can be reduced this ignores the volume of the working fluids, gas diffusion layer, seals, etc.

Another issue is that the power generation has a linear voltage drop while current batteries produce a constant voltage for a long time followed by a rapid drop-off. A voltage converter will be needed to produce a constant voltage while the battery discharges resulting in further inefficiency.

Then there is the days long charging time to consider (4 to 12 days for the reported results).

Mar 08, 2018
"while current batteries produce a constant voltage for a long time followed by a rapid drop-off"


Not really. The voltage of a lithium battery drops more or less linearily with discharge. Various chemistries have flatter or steeper curves, but they all drop, and voltage converters or regulators are used almost universally.

http://www.all-ba...urve.jpg


Mar 14, 2018
good work

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