Flywheels as a mode of battery have been around close to a century. They've been used by trolleys in Europe. They are already used in space where there is no friction. New technologies are making them more useful in orbit, but there are problems with using them in mobile applications. Here's a <a href="http://reddit.com/r/science/info/2bmxb/comments/c2bnf6">link </a>to a good discussion. Inside are links to several wikipedia articles. As far as chemical based batteries being overtaken by anything else in the near future, is doubtful. There's just a lot going on in that space. Aside from managing momentum better flywheels depend on novel materials that would reduce friction (superconductors are one area) Some of these same advances are sought in chemical battery operation.

Flywheels as a mode of battery have been around close to a century. They've been used by trolleys in Europe. They are already used in space where there is no friction. New technologies are making them more useful in orbit, but there are problems with using them in mobile applications. Here's a <a href="http://reddit.com/r/science/info/2bmxb/comments/c2bnf6">link </a>to a good discussion. Inside are links to several wikipedia articles. As far as chemical based batteries being overtaken by anything else in the near future, is doubtful. There's just a lot going on in that space. Aside from managing momentum better flywheels depend on novel materials that would reduce friction (superconductors are one area) Some of these same advances are sought in chemical battery operation.