Battery manufacturer Amprius claims it has perfected the application of silicon for lithium-ion anodes (writes Lawrence Butcher). 

Based on its proprietary silicon nanowire technology, it says it has demonstrated breakthrough performance in energy density and cycle life. Silicon anodes have much higher specific capacity than the graphite anodes used in conventional lithium-ion batteries. In particle or film structures, however, silicon is unstable and lasts only a few recharge cycles. Amprius says its silicon nanowire structures overcome this instability, enabling hundreds of cycles with specific energies of more than 435 Wh/kg and energy densities in excess of 1200 Wh/litre.

The silicon nanowire batteries are currently in use in the Airbus Zephyr UAV, which operates as a high-altitude pseudo-satellite (at heights above 70,000 ft), with the high specifi c energy of the batteries allowing for much longer run times than would be possible with traditional lithium-ion batteries of a similar size.