Featured Intriguing battery technology for EVs

I had heard mention of it, but don’t claim to know much about it...

 

It is already is some use has grid storage, and a residential sized one with a 25 year lifespan is suppose to come to the residential market this year.

Compared to Li-ion, flow batteries have lower energy density. That residential unit may only have a fifth of Li-ion. There other chemistries of flow that do better, but the electrolyte for those might be toxic, unstable, and/or expensive.

Even if energy density can be solved for cars, flow batteries can't switch between discharging and charging as quickly as Li-ion and NiMH. For regenerative braking, the car will need another battery, or go without it.

 

OK so maybe lock it in a box with a bank of ultracaps for braking+launch duty and a referee ECU?

 

or keep hoping for steady lion improvements

 

The leading contender in a flow type battery for transportation is aluminum air. The spent electrolyte is valuable so it needs to be drained and collected for recycling then filled.

The people pushing flow are talking about keeping it the current fueling infrastructure, but what most people seem to like about plug-ins are the ability to charge at home and/or work instead of a fueling station. My guess is to be successful cars with a flow battery would also have a fairly large rechargeable battery. Sure ultracaps may become small and cheap enough to fulfill this function, but I would bet flow is at least a decade away for transportation, and by then solid state or much improved lithium ion or gel will be included.

My guess is most miles would be charged in the rechargable, and 20% of miles might be on the flow.

 

Mazda's i-Eloop regenerative braking system uses a supercap. It works well enough to net a gain on the EPA city test, but the mild hybrid territory it is in isn't near what a BEV can pull off in terms of regen energy capture. There is going to be cost and packaging issues when sizing up the capacitor or battery for regen in one of these flow battery cars. Then it might be worth it to add a plug.

The flow battery may work out as a range extender for long trips, but there are questions that need to be answered. Like how much will the infrastructure for it cost? In addition to its cost, is the electrolyte toxic? What are the potential health and environmental dangers?

In comparison, the Al-air battery would seem to have an edge over the flow battery. Phinergy, an Al-air battery company, has a little demo car with one of their batteries installed that was new around when the gen1 Leaf was still new. The plug in range on the Li-ion battery was around 80 miles, and the Al-air battery could provide about 1000 miles before needing the anodes replaced. Before then some distilled water needed to be added every 100 to 200 miles. While you'll want stations with dispensing pumps for the water at some point, distilled water is already available and cheap now.

The hurdle will be setting a 'recycling' network. A basic auto shop could do the work of replacing the anodes. They are just slabs of aluminum being replaced with aluminum hydroxide(IIRC) sludge being pumped out. Nothing toxic being handled. You just want a system in place for collecting the Al hydroxide for reuse, it has some value on its own, or to be resmelted back into metal.