The researchers managed to remove two long-standing barriers to these improvements by putting silicon particles in graphene "cages."
To improve capacity in recent years batteries have begun to use silicon anodes, which have more capacity than the graphite conventionally used. But silicon particles also swell so much during charging that they're prone to cracking or shattering and they can also react with the battery electrolyte, forming a coating that reduces performance.
The solution from the team at Stanford and the Department of Energy's SLAC National Accelerator Laboratory is to encase each silicon particle in a "custom-fit cage" of graphene. At only one-atom thick, graphene is the thinnest, strongest form of carbon and also conducts electricity well.
The carbon cages would allow the silicon to expand and even break apart, but keep the pieces together so that they can continue to function. The graphene barrier would also block the destructive chemical reactions with the electrolyte from occurring.