Xenon and fluoride, combined under pressures similar to those found at the center of the Earth, have been used to create an ultra-battery, capable of storing more condensed energy than any other battery ever built.
The material used to make the battery is xenon difluoride (XeF2), a white crystal, which is placed in a diamond anvil cell. The cell uses two tiny diamond anvils to produce incredibly high pressures in tiny, contained spaces.
io9 reports:
“When the pressure reached a million atmospheres ... the molecules formed 3D metallic ‘network structures’, which forced all the mechanical energy of the compression process to be stored as chemical energy within the molecular bonds ... Heading up this research is Washington State chemistry professor Choong-Shik Yoo, who says this ‘is the most condensed form of energy storage outside of nuclear energy.’”