There’s something in Li-air

Ally Winning


The search for a better and more sustainable form of battery technology is arguably the most important aspect of our fight against climate change.

Nothing will assist our switch from fossil fuels to renewable energy faster than better storage technology. Exactly the same thing can be said for the same move for the automotive and transportation industries. In 2020, only 12% of energy used came from renewable sources with another 9% from cleaner nuclear fuel according to the US Energy Information Administration. The same report states that transportation accounts for a quarter of all energy used in the US. Better batteries are key to cutting our dependence on fossil fuels.


Li-ion battery technology is the battery type that we currently rely on most widely. It has served us well through the mobile phone revolution and the development of electric vehicles. Even though many researchers are trying to squeeze every last ounce of performance out of the technology, it probably can’t improve enough for very high capacity electric vehicles or for large scale renewable grid use. Researchers are also looking to other types of battery chemistries for the higher density that is required.


One of the most promising types of battery chemistry is Lithium air. Although the technology was originally developed in the 1970s, it has several drawbacks that stopped it becoming mainstream. Lithium air batteries can store between five and six times the energy of Li-ion batteries, but they are not as efficient, and the energy required to charge than is much more than they can store. A second drawback is that the Lithium tends to react with the impurities in air as well as the oxygen. This means the cathode is ‘clogged up’ and doesn’t offer more than a handful of charging cycles. If those drawbacks could be ironed out, then we could see electric vehicles sporting Lithium air batteries with ranges of up to 2,000 miles.


One researcher who is trying to overcome these restrictions and bring Lithium Air batteries to the market is Mohammad Asadi, Assistant Professor of Chemical Engineering at the Illinois Institute of Technology (IIT). Asadi has been investigating new materials that could be used for the three main components of the battery – the anode, cathode and electrolyte. Much of the problem is that the Lithium ions react with other substances in the air, using up the Lithium and stopping the oxygen reaching the cathode. Asadi and his team have developed a novel hybrid electrolyte that works to absorb the impurities before they react with the Lithium. A Lithium Carbonate coating is used on the Lithium anode, which blocks out everything but Lithium ions as the battery charges and discharges. This process allows the battery to achieve up to 1200 charge/discharge cycles.


The second hurdle to overcome was improving the efficiency. The team at IIT tested various materials for the cathode. The main problem here was that there are two reactions that need to happen at the cathode – the formation of lithium peroxide when the battery is being used and breaking up the lithium peroxide when the battery is being charged. Many materials are good at one or the other of these reactions, but until now, there hasn’t been one found that excelled at both. Asadi and his team discovered that an inexpensive material called trimolybdenum phosphide nanocatalysts could efficiently drive the two reactions.


Testing has now shown that the new Lithium air battery materials are functioning as well as simulations have predicted, and are starting to become comparable to Li-ion. The next hurdle to overcome is to scale the new battery designs up to be commercially viable. For this stage, Asadi is looking to partner with industry to incorporate the technology into new technology and applications for lab scale prototyping and commercialisation.


Although Li-air technology may offer an ideal battery solution with higher energy density, it is not the end of the road for battery development. Lithium is still hard to source, and demand will keep growing. Other materials, such as Magnesium, Aluminium and Calcium may be able to provide similar performance, but are far more widely available.