Fast charge rate beats US targets

Amprius Technologies has demonstrated a charging rate of 6 minutes to 80% from 0% state of charge for its silicon-based batteries (writes Nick Flaherty).

This exceeds the targets for 2025 set by the US government for charging a battery cell to 80% in less than 15 minutes. 

Using silicon nanowires avoids the problems of the silicon expanding during charging by being rooted to the substrate, and reduces the thickness of the anode by half compared with using graphite. This thinner anode also helps provide fast charging and means the cell can be half the size of today’s graphite-based cells.

Charging cycle for the silicon anode battery

The nanowires have allowed Amprius to ship commercial lithium-ion cells with a specific energy of 450 Wh/kg and an energy density of 1150 Wh/litre.

“These results confirm the benefits of our Si-nanowire anode for EV applications, where fast charging and high energy density are essential,” said Jon Bornstein, chief operating officer of Amprius Technologies. “The need to shorten charge times extends well beyond the rapidly growing EV market and into the broader e-mobility markets, including micro-mobility and aviation.”

The nanowires enable an anode that is much lighter than conventional graphite anodes, and they have much higher conductivity owing to the high electrical continuity between the silicon and the current collector. The very low tortuosity, or the amount of porosity, of the anode structure helps boost the fast charging.

The fast charging technology is available on battery cells now in commercial production by Amprius.