My watch list
my.chemeurope.com  
Login  

Low-cost battery from waste graphite

13-Oct-2017

Empa / ETH Zürich

Kish graphite is a waste product from steel production. It could be used to make a cheap rechargeable battery out of abundant materials.

Lithium ion batteries are flammable and the price of the raw material is rising. Are there alternatives? Yes: Empa and ETH Zürich researchers have discovered promising approaches as to how we might produce batteries out waste graphite and scrap metal.

Kostiantyn Kravchyk works in the group of Maksym Kovalenko. This research group is based at both ETH Zurich and in Empa’s Laboratory for Thin Films and Photovoltaics. The two researchers’ ambitious goal at the Empa branch is to make a battery out of the most common elements in the Earth’s crust – such as magnesium or aluminum. These metals offer a high degree of safety, even if the anode is made of pure metal. This also offers the opportunity to assemble the batteries in a very simple and inexpensive way and to rapidly upscale the production.

In order to make such batteries run, the liquid electrolyte needs to consist of special ions that do not crystallize at room temperature – i.e. form a kind of melt. The metal ions move back and forth between the cathode and the anode in this “cold melt”, encased in a thick mantle of chloride ions. Alternatively, large but lightweight organic anions, which are metal-free, could be used. This does come with a problem, though: where are these “thick” ions supposed to go when the battery is charged? What could be a suited cathode material? By way of comparison: in lithium ion batteries, the cathode is made of a metal oxide, which can easily absorb the small lithium cations during charging. This does not work for such large ions, however. In addition, these large anions have an opposite charge to the lithium cations.

Battery turned “upside down”

To solve the problem, Kovalenko’s team had a trick up their sleeves: the researchers turned the principle of the lithium ion battery upside down. In conventional Li-ion batteries, the anode (the negative pole) is made of graphite, the layers of which (in a charged state) contain the lithium ions. In Kovalenko’s battery, on contrary, the graphite is used as a cathode (the positive pole). The thick anions are deposited in-between the graphene layers. In Kovalenko’s battery, the anode is made of metal.

Kravchyk made a remarkable discovery while searching for the “right” graphite: he found that waste graphite produced in steel pro-duction, referred to as ”kish graphite”, makes for a great cathode material. Natural graphite also works equally well – if it is supplied in coarse flakes and not ground too finely or into folded, non-flake shapes. The reason: the graphite layers are open at the flakes’ edges and the thick anions are thus able to slip into the structure more easily. The fine-ground graphite normally used in lithium ion batteries, however, is ill-suited for Kovalenko’s battery: by grinding the graphite particles, the layers become creased like crumpled-up paper. Only small lithium ions are able to penetrate this crumpled graphite, not the new battery’s thick anions.

The graphite cathode battery constructed from steel production “kish graphite” or raw, natural graphite flakes has the potential to become highly cost-effective. And if the first experiments are anything to go by, it is also long-lasting. For several months, a lab system survived thousands of charging and discharging cycles. “The aluminum chloride – graphite cathode battery could last decades in everyday household use,” explains Kravchyk and adds “similar demonstrations, but further increased battery voltages, without compromising capacities, and of even lighter elements are on the way and will offer further increase in energy densities from current 60 Wh kg-1 to above 150 Wh kg-1”

Facts, background information, dossiers
  • ETH Zürich
  • cathode materials
More about Empa
  • News

    Nanomaterial helps store solar energy: efficiently and inexpensively

    Efficient storage technologies are necessary if solar and wind energy is to help satisfy increased energy demands. One important approach is storage in the form of hydrogen extracted from water using solar or wind energy. This process takes place in a so-called electrolyser. Thanks to a new ... more

    Microplastics from the washing machine

    The presence of microplastics in our wastewater can be attributed primarily to two factors. Firstly, many cosmetic products, such as toothpaste, creams, shower gels, and peelings, contain tiny pieces of plastic in order to achieve a mechanical cleaning effect. Secondly, microplastics are wa ... more

    How protons move through a fuel cell

    Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conve ... more

More about ETH Zürich
  • News

    Rapid imaging of granular matter

    Even in our modern world full of highly technological machines and devices it is still impossible to predict when rockslides, such as the recent one in Graubünden, or earthquakes will occur and how exactly they evolve. This is partly due to the fact that despite many years of research, scie ... more

    A dream of foam

    Oktoberfest in Munich is an exciting cultural event, but it is also a source of inspiration for materials scientists and engineers. Not the beer itself, but rather the beer foam is a source of inspiration. A good head of foam -- generally measuring about 1.5 cm and containing an impressive ... more

    Green light for ultra-fine display colors

    Chih-Jen Shih is very satisfied with his breakthrough: "To date, no one has succeeded in producing green light as pure as we have," says the Professor of Chemical Engineering in his laboratory at ETH Zurich. He points at an ultra-slim, bendable light-emitting diode (LED), which displays the ... more

  • Videos

    Oxybromination of methane over vanadium phosphate

    ETH Zurich scientists have discovered a new catalyst that allows the easy conversion of natural gas constituents into precursors for the production of fuels or complex chemicals, such as polymers or pharmaceuticals. The new catalyst is extremely stable and results in fewer unwanted by-produ ... more

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE