MTorrice writes "Lithium-sulfur batteries promise to store four to five times as much energy as today's best lithium-ion batteries. But their short lifetimes have stood in the way of their commercialization. Now researchers demonstrate that a sulfur-based polymer could be the solution for lightweight, inexpensive batteries that store large amounts of energy. Battery electrodes made from the material have one of the highest energy-storage capacities ever reported" Litihium Ion batteries should maintain capacity for about 1000 cycles, whereas Lithium-sulfur batteries traditionally went kaput after about 100. But it looks like they are getting pretty close to something feasible, from the article: "The best performing copolymer consisted of 90% sulfur by mass. Batteries using this copolymer had an initial storage capacity of 1,225 mAh per gram of material. After 100 charge-discharge cycles, the capacity dropped to 1,005 mAh/g, and after 500 cycles it fell to about 635 mAh/g. In comparison, a lithium-ion battery typically starts out with a storage capacity of 200 mAh/g but maintains it for the life of the battery, Pyun says."