BMW has begun testing solid state batteries with this prototype i7

BMW has started testing fancy all-solid-state batteries (ASSBs) in a prototype i7 with its tech mate Solid Power. Over the next several months, the two companies will work out how to get these fancy batteries to handle extreme temperatures and pressures, out of BMW’s Cell Manufacturing Competence Center (CMCC) in Parsdorf, Germany.

Solid Power, the battery chemist, is an industry-leader, looking to help carmakers lower costs, improve safety and increase battery energy density using clever chemistry.

These particular solid-state batteries use a silicon anode, an NMC cathode and (crucially) they deploy a non-flammable sulfide electrolyte. Solid Power’s use of the sulfides for the electrolyte isn't incidental. That’s the bit that reduces fire risk.

Although BMW doesn’t tell us what energy density the test i7’s batteries carry, typically Solid Power’s boast 390Wh/kg. As a point of reference, Merc’s striving for a solid-state energy density of 450Wh/kg, but current lithium-ion batteries only have up to 220Wh/kg.

The i7's ASSBs sit on BMW's Gen5 architecture, first featured in the 2021 iX3. Solid's higher energy dense chemistry has been integrated into BMW's compact prismatic-shaped cells, meaning more range. And the materials are 96 per cent recyclable.

How the duo will fare while exploring the technology during heatwaves and cold snaps is yet to be determined, but more as we get it.