These batteries will weigh a third of the equivalent lithium-ion batteries and have twice their lifespan. It is also worth noting that their battery was three times as energy-dense as lithium-ion and could charge just as fast! This was so effective that the scientists sent the battery through 4,000 charge cycles without a drop in capacity, meaning it lasts at least twice as long as lithium-ion. In the battery, this phase completely stops the reaction that creates polysulfides. This is the first time it has been seen at room temperature. This chemical phase is known as monoclinic gamma-phase sulfur but had only ever been observed in the lab at high temperatures - upwards of 95☌ (203☏). Slowing them down could make these very energy-dense batteries last longer. These crystals effectively take sulfur out of the electrode and ultimately cause a massive loss of capacity. Their goal was to slow down the chemical reaction that creates polysulfides when the battery charges and discharges. To solve this, the Drexel team was trying new approaches to lithium-sulfur, by changing compounds in the battery’s cathode. Lithium-sulfur batteries can be cheaper to produce and up to three times more energy-dense than lithium-ion batteries. So, after a year or two of proper use, a lithium-sulfur battery is basically dead. While a lithium-ion battery can be useable for around 2000 charge cycles, lithium-sulfur is typically limited to around only half that. So, what’s the catch? Why don’t we already have them? It uses far less ecologically harmful materials, can be cheaper to produce, can be up to three times more energy-dense (meaning a lighter battery) and is far less likely to catch fire. On the surface, lithium-sulfur seems to solve all of lithium-ion’s problems.

Lyten are one of the few manufactures of lithium-sulfur batteries (pouch cell on left).

Sulfur ion charge