In this video, Stanford graduate student Wesley Zhang demonstrates the new low-cost, long-lived flow battery he helped create. The researchers created this miniature system using simple glassware. Adding a lithium polysulfide solution to the flask immediately produces electricity that lights an LED. A utility version of the new battery would be scaled up to store many megawatt-hours of energy.
Read more about the research: http://www6.slac.stanford.edu/news/2013-04-24-polysulfide-flowbattery.aspx