Sila Nanotechnologies emerged from stealth mode last month, partnering with BMW to put the company's silicon-based anode materials in at least some of the German automaker's electric vehicles by 2023. A BMW spokesman told the Wall Street Journal the company expects that the deal will lead to a 10 to 15 percent increase in the amount of energy you can pack into a battery cell of a given volume. Sila's CEO Gene Berdichevsky says the materials could eventually produce as much as a 40 percent improvement.

Sila Nanotechnologies figured out ways to alter the internal structure to prevent the battery electrolyte from seeping into the particles, and it achieved dozens of incremental gains in energy density that ultimately added up to an improvement of about 20 percent over the best existing technology.