Lithium-Sulfur batteries might be one of the new kinds of batteries that could replace currently most used Lithium-Ion batteries. But so far they suffer from a few problems.
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Bigger But Lighter
The advent of electric cars is accompanied by much more intense research into new types of batteries. One of the technologies that might prove itself in the future is lithium-sulfur batteries. These have been in development for a significant time and they have gone through a good number of advancements. Like in the spring of 2019, MIT managed to make them significantly smaller as the size is still one of the biggest issues of the technology.
On the other hand, the benefit of the technology is a much larger energy density to space ratio. The resulting batteries would need more space in a car but would be less heavy. For example, in the case of the MIT batteries, they would require 20 % more space but would be lighter by 30 %. Now scientists from Monash University in Australia decided to take a look at lithium-sulfur batteries.
Energy Is Good – But The Lifespan Isn't
These scientists say that the technology is theoretically capable of having up to five times more energy per kilogram of mass compared to Li-Ion batteries. But that is really just theoretical. The shape of and the use of the battery plays a large role in how much energy you can pack into it. If you create it in a shape of a regular battery it is capable of having roughly four-times more energy density but car batteries are quite different and the energy density there would likely be only around two times as much.
That may sound quite good, but there is another and much bigger problem that needs to fix. The cathode lasts for only 40 – 50 charging cycles. That is just an awful number. To give you an idea of how bad this is – if the electric car had a driving distance of 500 km before it needed a recharge such a battery would last for only 20 to 25 thousand kilometers.
The Biggest Problem - Lifespan
The problem lies in the fact that when the cathodes discharge it gathers lithium ions and creates Li2S. But this process significantly increases the volume of and repetition of these changes of volume during charging and discharging brings quite a degradation. This is why the scientists added carbon into the cathode and changed its structure into a sort of web. The web has much less binding that keeps the carbon and sulfur together allowing for more free space. This means that when the cathode discharges it doesn't change its volume by that much as it uses the free space increasing its longevity.
The scientists would like to achieve a lifespan of at least 500 charging cycles as that would give electric cars a total driving distance of roughly 250,000 kilometers. Nonetheless, so far their new technology allowed them to get to only a hundred cycles and that is still too little.
To get truly commercially viable lithium-sulfur batteries they would still need to get two to four times more cycles out them (in my opinion) but once that is done they could get on the market within a relatively short time – just two to four years.
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