 However, as hydrogen production requires considerable energy, this is only a proposed method of storing energy, not producing it.Silicon nanotubes and silicon nanowires can be used in lithium-ion batteries.Conventional Li-ion batteries use graphitic carbon as the anode, but replacing this with silicon nanotubes experimentally increases the specific (by mass) anode capacity by a factor of 10 (though the overall capacity improvement is lower due to the far lower specific cathode capacities).