Featured Toyota makes progress on all-solid-state batteries

Maybe we're discussing roughly the same thing. There was confusion before I posted, possibly caused by @bwilson4web.

Solid-state batteries are a type of lithium-ion battery. Dendrites are only a concern with lithium-metal anodes, not all solid-state batteries. However, some companies (QuantumScape, Prologium, SES AI, etc.) have successfully developed lithium-metal solid-state EV batteries and are about to commercialize them. Dendrites cannot grow through well-designed and well-interfaced ceramic solid electrolytes. There is no space in the ceramic for lithium metal to form anywhere other than at crystal grain boundaries, and some companies have found ways to circumvent that. Dendrites are harder to control with sulfide solid-state electrolytes, likely because they have a more glassy structure. That’s why Toyota uses a carbon/silicon anode instead of a lithium-metal one. Similarly, with a polymer solid-state electrolyte, it’s challenging to achieve a good anode interface that prevents dendrite growth.

Again, the working principle of solid-state batteries is the same as that of liquid-electrolyte batteries, except that a non-porous solid-state electrolyte with high lithium-ion conductivity lies between the anode and the cathode, making a porous membrane unnecessary.

 

I expect at least some Gen 6 Prius trims to have solid-state batteries.

 

Toyota has already worked out a carbon/silicon-anode, sulfide-solid-state electrolyte all-solid-state battery.

The only remaining question is whether they can make it as cheap as conventional lithium-ion batteries or even cheaper. The answer is probably yes by the time they move into their 50-GWh/yr factory. It is all about scaling right now, which involves building smart, large-scale tools.

Lithium-metal solid-state batteries developed by others are much harder to make (due to the need to prevent dendrites), but that does not mean they won’t be a reality.

PS: Making conventional lithium-ion batteries is also a nightmare, which took decades to figure out.

 

And the challenge with non-lithium-metal-anode solid-state batteries is primarily to keep the layer of solid-state electrolyte between the anode and cathode well-interfaced, as the batteries undergo volume changes during charging and discharging. (The same challenge also exists for lithium-metal-anode solid-state batteries.) For example, if the glassy sulfide solid-state electrolyte layer Toyota uses loses good contact, then the battery dies, as the lithium ions can no longer move between the anode and cathode. They apply external pressure (typically 50 psi) with steel plates on the pouch solid-state cells to keep the layer of solid-state electrolyte tightly against the anode and cathode, which also increases weight, but it doesn’t always help. Precise manufacturing and internal cell innovations are necessary, which potentially increase the cost.