Lithium–sulfur battery

The lithium–sulfur battery (Li–S battery) is a type of rechargeable battery. It is notable for its high specific energy. The low atomic weight of lithium and moderate atomic weight of sulfur means that Li–S batteries are relatively light (about the density of water). They were used on the longest and highest-altitude unmanned solar-powered aeroplane flight (at the time) by Zephyr 6 in August 2008. Lithium–sulfur batteries may displace lithium-ion cells because of their higher energy density and reduced cost. This is due to the use of sulfur instead of cobalt, a common element in lithium-ion batteries. Li–S batteries offer specific energies on the order of 550 Wh/kg, while lithium-ion batteries are in the range of 150260 Wh/kg. Li–S batteries with up to 1,500 charge and discharge cycles were demonstrated in 2017, but cycle life tests at commercial scale and with lean electrolyte have not been completed. As of early 2021, none were commercially available. Issues that have slowed acceptance include the polysulfide "shuttle" effect that is responsible for the progressive leakage of active material from the cathode, resulting in too-few recharge cycles. Also, sulfur cathodes have low conductivity, requiring extra mass for a conducting agent in order to exploit the contribution of active mass to the capacity. Volume expansion of the sulfur cathode during S to Li_2S conversion and the large amount of electrolyte needed are also issues. LiS batteries were invented in the 1960s, when Herbert and Ulam patented a primary battery employing lithium or lithium alloys as anodic material, sulfur as cathodic material and an electrolyte composed of aliphatic saturated amines. A few years later the technology was improved by the introduction of organic solvents as PC, DMSO and DMF yielding a 2.35-2.5 V battery. By the end of the 1980s a rechargeable LiS battery was demonstrated employing ethers, in particular DOL, as the electrolyte solvent. In 2020 Manthiram identified the critical parameters needed for achieving commercial acceptance.