They could power a car for more than 800 km, be recharged more than 2000 times, and have an energy density 10 times longer than traditional batteries.
A miracle? No, a challenge that has kept some universities across the world quite busy.
They’re the lithium-air or lithium-oxygen batteries, and could overcome many of the limitations that now hamper the development of electric cars or renewable energy accumulators, without considering the “small” applications, such as smartphones and laptops.
Many are obstacles. The lithium-air indeed offer potential energy much higher than those provided by current batteries, thanks to the combination of lithium (a light metal), with oxygen (gas widely available in the atmosphere), but their development has been held back by problems associated with poor reversibility and limited operating time such a life cycle of just 50 cycles maximum, compared to 1,200 obtainable from the lithium-ion batteries used habitually.
That’s why, in 2012, STABLE was born (acronym for “Stable high-capacity Lithium-Air Batteries with Long Life Cycle for Electric cars”), a European project that has set itself the goal of improving energy storage devices, especially for electric cars.
STABLE aims at improving the performance of lithium-air batteries: the combination of light metal with oxygen gas makes these batteries the ideal candidates for the propulsion of electric vehicles since they offer potential energy well above the current rechargeable batteries. “The main advantage of a lithium-air is the large energy density, which is theoretically 10 times higher than that of lithium-ion batteries”, says Prof. Qiuping Chen, associate professor at the Polytechnic of Turin and project coordinator STABLE.
The multidisciplinary team of STABLE worked on the life cycle of these batteries, which, thanks to the synthesis of materials, testing of new catalysts, simulation, modeling and assembly of battery reaches, now, after three years of hard work, 100-151 cycles. “It was a research project at first stage,” concludes Professor. Chen. “We managed to achieve our goals, but we have verified these results only on a laboratory scale. We still have much work to do to bring our new batteries on the market and we face difficulties ranging from the production of raw materials to improve the technology and equipment of the lithium-air.”
On this way, they are also working researchers at the University of Cambridge, that have demonstrated how some of these obstacles can be overcome. Scientists have in fact developed a prototype of a battery with a higher capacity, greater energy efficiency and better stability than previous attempts, thanks to a carbon electrode made of graphene additives and chemical reactions occurring on the battery, making it more stable and efficient.
“In the lithium-ion battery (Li-ion) used in our laptops and smartphones, the negative electrode is made of graphite, the positive electrode is made of a metal oxide, and the electrolyte is a lithium salt dissolved in a organic solvent. The action of the battery depends on the movement of lithium ions between the electrodes. The Li-ion batteries are lightweight, but their ability deteriorates with age, and their relatively low energy density means that they have need to be recharged frequently,” explains Liu, Grey and Cambridge colleagues.
What we have developed, using a chemical very different from previous attempts, relying on lithium hydroxide (LiOH) instead of lithium peroxide (Li2O2). With the addition of water and the use of lithium iodide, their battery showed the “need” of less chemical reactions, making it more stable after several cycles of charging and discharging, according to the results published on Science magazine. “What we got is a significant step forward for the technology and suggest new areas of research” says prof. Clare Grey.
However, the researchers warn: a lithium-air remain outside the market for at least a decade.