Aluminum-air battery may be cure for range anxiety
Developed by Phinergy, an Israeli start-up, and aluminum giant Alcoa, the aluminum-air battery, its inventors say, could eliminate range anxiety from electric vehicles, adding 1,600 km.
NOVI, MICHIGAN—Every so often I see an innovation so intriguing that I hope it’s for real; not just another too-good-to-be-true “breakthrough.”
So it was as I wandered the annual Battery Show in the cavernous Suburban Collection Showplace convention centre here, just west of Detroit. Off to one side sat a small hatchback with a bundle of wires and metal plates packed into its luggage compartment.
A nearby sign said “Phinergy,” and directed me toward a booth a couple of aisles over.
There, I encountered the aluminum-air battery, a device that, its inventors say, could eliminate range anxiety from electric vehicles. It’s being developed by Phinergy, an Israeli start-up, and the aluminum giant Alcoa.
As usual, the workings are somewhat complicated.
First, aluminum-air could not be the only battery in an EV: it would operate in conjunction with a lithium-ion unit.
The lithium-ion battery would power the car until depleted, in practice covering most daily driving. When needed, particularly for longer trips, the vehicle’s computer would automatically switch to aluminum-air.
Lithium-ion batteries are recharged by plugging into the electricity grid. The range they provide is determined by how much energy can be stored in the metallic compounds that coat the positive electrode, or cathode, in their cells. Once all of that energy has moved to the negative side, or anode, the battery must be recharged.
This storage capacity is the major limit on EVs.
Aluminum-air works differently: instead of consuming stored energy, it generates electricity through a reaction created by air drawn into the battery cells, similar to how internal-combustion engines suck in air to help burn gasoline.
The cathode is coated with a patented material — no details offered — that reacts with oxygen. The anode is an aluminum plate.
As in all batteries, the electrodes are kept apart by a separator and electrolyte, usually a liquid. The electric current is created when charged particles move through these two components of the cell from cathode to anode.
In a nutshell, in aluminum-air, the charged materials created when air reacts with the cathode are drawn to the aluminum anode, where they react again to create aluminum hydroxide. That substance, in turn, goes into the electrolyte.
The process gradually eats away the aluminum plates. The battery will operate as long as those plates last. That’s the 1,600-kilometre limit.
When the plates are done, they can be replaced. Phinergy estimates that procedure would cost about the same as 1,600 kilometres worth of gasoline, at today’s price.
When aluminum reacts with oxygen, as in this battery, the process creates a coating that stops further oxidation. That’s why aluminum resists rusting so well and also why we can safely cook with aluminum pots: The metal is toxic but the coating protects us by sealing the surface.
In the battery, oxidation must continue, so the electrolyte contains additives to prevent the sealing effect.
As the aluminum plate is eaten away, the electrolyte acquires so much aluminum hydroxide it must be must be replaced. That step is required every 500 kilometres or so and, Phinergy says, would take about five minutes. The aluminum can be extracted and both it and the electrolyte recycled.
The battery is only active with electrolyte in its cells. When it isn’t required, its electrolyte drains into a tank and the system goes dormant until needed again.
Phinergy says the system works well. Alcoa could make the aluminum plates at its smelter in Baie-Comeau, Que. The companies are seeking support from the province, which is pushing EV adoption to consume its vast store of hydroelectric power.
As always, there are roadblocks.
The batteries current version is bulky; it must be repackaged and downsized.
The system would increase an EV’s price: The companies won’t say by how much.
It also requires a large network of places to replace the electrolyte and aluminum plates.
Too good to be true? Maybe. But it looks like a good try.