Scientists resolved two of the most challenging issues surrounding lithium-oxygen batteries

The future is battery-powered – we already know that. But batteries, despite the recent advancements, are still not perfect. Far from it – they are expensive, have very limited lifespan, require a lot of time to charge and so on. Hopefully, at least some of the problems can be solved by the new lithium-oxygen batteries, created by chemists from the University of Waterloo in Canada, because they have almost a 100 per cent coulombic efficiency.

Lithium-ion batteries are used very commonly now, but in the future they could be replaced by li-air technology. Image credit: Ralf Roletschek via Wikimedia

Scientists managed to achieve four-electron conversion for the first time. This technology doubles the electron storage of lithium-oxygen batteries. With this new study scientists proved that four-electron conversion for lithium-oxygen electrochemistry is highly reversible, which could lead to the next big breakthrough, even though there are still limitations based on thermodynamics. This could solve some problems that scientists have been trying to tackle for a long time.

Lithium-oxygen batteries, also known as lithium-air batteries, theoretically feature high energy density relative to their light weight. In fact, this property made them the Holy Grail of rechargeable battery systems. Although it really is a question worth billions of dollars, some issues, such as chemical stability, kept lithium-oxygen batteries from becoming anything else than purely academic curiosity. Batteries must have a long cycle life for them to be practical. But lithium-oxygen batteries are not great in this case, because LiO2 superoxide and Li2O2 reacts with porous carbon cathode and degrades it. This means that the battery starts deteriorating from within. Furthermore, LiO2 consumes the electrolyte, which significantly reduces the lifespan of the battery.

So these were the two main issues – the organic electrolyte and porous carbon cathode. Scientists replaces the electrolyte with a more stable inorganic molten salt and substituted the porous carbon cathode with a bi-functional metal oxide catalyst. Scientists also decided to operate the battery at temperatures of 150 degrees Celsius, which removed the Li2O2 in favour for a more stable Li2O, which improved reversibility of the lithium-oxygen battery and increased their coulombic efficiency to almost 100 %. Linda Nazar, senior author of the project, said: “By swapping out the electrolyte and the electrode host and raising the temperature, we show the system performs remarkably well”.

These are, of course, the first steps to making lithium-oxygen batteries more common. Hopefully, further research will reveal other positive results and more efficient batteries can become commercially available fairly soon.

 

Source: University of Waterloo


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