Lithium-air batteries have been challenged with several big hurdles, but the new design brings so much promise. Lithium-air cells can store more dense energy than today’s lithium-ion batteries, making them promising for electric cars. The design uses a spongy graphene electrode and a new chemical reaction to drive the cell. It can be recharged many more times, and it loses much less energy than previous lithium-air batteries.
Engineers hope that lithium-air batteries will take in regular air to create a chemical reaction that releases electricity. Lithium ions move from the positive electrode to the negative electrode, where they are oxidized. At present, University of Cambridge engineers have only made pure oxygen-laboratory test units rather than air. It is noted, however, that prototypes operate when the oxygen is moist.
True Lithium-Air Battery
Senior author of the study, Prof Clare Grey, said that they want a true lithium-air battery – the one that just takes in air without the need to remove water, nitrogen, and CO2. Grey revealed they currently have a system that tolerates a lot of water. But, despite this significant progress, Prof Grey and his team admit that they need at least ten years for a commercial lithium-air battery.
As of today, their demonstration units are still sluggish. Prof Grey explained that their batteries needed days to charge and discharge, and they were aiming for it to happen in minutes and seconds. But they found significant advantages of the design.
New Way Of Thinking
It stores energy denser than the theoretical limit for lithium-air batteries. The energy density will take electric cars across countries on a single charge rather than just cities. It loses little energy as heat – it charges and discharges at a voltage of 3.0 and 2.8 respectively – an efficiency of 93%. This a vast improvement on previous lithium-air efforts and near to the current lithium-ion batteries’ efficiency.
Additionally, these test batteries can be charged and recharged over 2,000 times with only little effect on their function. Prof Grey said that they had been able to cycle their cells for months, with very little evidence of side reactions. The so-called wonder material is part of the reason for the success. The design of the cathode is made from a sponge-like arrangement of graphene, build up from one-atom-thick sheets of carbon.
The porous cathode’s holes enable reaction products to build up, as the battery discharges, then dissolve away again as it gets recharged. Also important is the chemical reaction itself. An additive, lithium iodide, changes the chemistry at the heart of the battery. The discharging reaction makes lithium hydroxide (LiOH) at the cathode instead of lithium peroxide like in most other lithium-air designs.
New Directions To Study
The lithium hydroxide can be entirely dissolved away again when the battery is recharged, and the lithium ions return to the anode. Prof Grey said that it is a very different chemistry as it offers a new way of thinking about it. Though more work should be done to make it commercial, the development provides some interesting new directions to study.
Chemical Engineer at University College London, Dr Paul, said that the design was an important step towards taking lithium-air batteries from the lab to the market. He added the Cambridge design was very impressive as it could potentially address the problems of poor cycle life of the current lithium air batteries. If successful, lithium-air batteries can make a huge difference as their density is very close to the energy-per-kilogram packed by petrol.