Most of the solid state batteries have far less thermal runaway problem than lithium-ion batteries. At this point, several companies have working demo solid state batteries, but the price is far too high. Mercedes has one demo car with a solid state battery. Ducati has one motorcycle. Donut Labs just has one demo cell, not even enough for their motorcycle. The technology works but is so expensive there aren't even multiple prototypes.

Samsung says they will ship some solid state batteries in watches and earbuds this year, where the batteries are so tiny they're affordable. Even solid state batteries for phones are still too costly. Everybody in the industry is trying to solve the production price problem. Consensus is that the price starts to come down around 2028 or so.

Lithium iron phosphate batteries don't have a thermal runaway problem, either, but they have about half the Wh/Kg of lithium-ion, so they're not popular for portable devices.

Ten years out, lithium-ion batteries will probably be obsolete technology and totally prohibited on aircraft.

I wasn't sure what a solid state battery is, so I looked it up on Wikipedia.

Fun fact though:

> Between 1831 and 1834, Michael Faraday discovered the solid electrolytes silver sulfide and lead(II) fluoride, which laid the foundation for solid-state ionics. Through his research, Michael Faraday took note of these solid compounds transitioning from insulators to conductors after being heated. While this would take almost another century to be acknowledged by Michael O'Keeffe in 1976, this mixed ionic/electronic conductions became the first record of a solid-state battery

(emphasis mine)

Afaik sodium batteries are much safer than li-ion and already in mass production. Unless Donut scales up really quick I think it will be more viable to just use sodium batteries for safety in the medium-term future