A new lithium-sulphur battery with an ultra-high capacity five times higher than that of today’s lithium-ion batteries could lead to drastically cheaper electric vehicles (EV), smartphones and grid energy storage.
Mahdokht Shaibani at Monash University in Melbourne, Australia, and her research colleagues have developed a Li-sulphur battery with a capacity 5 times higher than that of lithium-ion batteries. The battery maintains an efficiency of 99% for more than 200 cycles, and a smartphone-sized version would be able to keep a phone charged for 5 days.
For an uninitiated, use of sulfur cathodes in lithium-sulfur (Li-S) batteries and silicon anodes in lithium-ion batteries is the most attractive example of inexpensive electrodes. An electrode is a conductor through which electricity enters or leaves and Li-S electrodes has excellent ability to store lithium, hence the potential for outperforming conventional lithium-ion used today in EVs, smartphones.
Lithium-ions stored on their electrodes during charging are subsequently released during discharging — just like when smartphones are charged-discharged. One of these electrodes, known as the anode, is typically made from graphite, an inexpensive form of carbon that is used in pencil lead. However, graphite accommodates a relatively small amount of lithium ions.
The practical difference between Lithium batteries and Lithium-ion (Li-ion) batteries is that most Lithium batteries are not rechargeable but Li-ion batteries are rechargeable.
To date, the problem with lithium-sulphur batteries has been that the capacity of the sulphur electrode is so large that it breaks apart over cycles of charging and discharging, and the energy advantage rapidly disappears, says Shaibani. The electrode will fall apart, and then the battery dies fast.
To prevent the electrode disintegrating in their lithium-sulphur battery, the Shaibani and her research team gave the sulphur particles more space to expand and contract by using a smaller amount of a polymer binding material and thus created more spaced-out structures between the sulphur particles.
A polymer is a large molecule made up of chains or rings of linked repeating sub-units called monomers. Polymers usually have high melting and boiling points.
According to Shaibani, this lithium-sulphur battery would drastically reduce the cost of batteries for electric cars and grid energy storage because sulphur is abundant and extremely cheap. In order to have much cheaper energy and more ethical batteries, we need a radically new energy storage system.