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Forget lithium, think zinc!

28 April 2017

If you wanted to come up with a piece of technology that would make you insanely rich then you should be focused on battery technologies.

For quite some time, the world has relied on chemical batteries to provide us with the portable hi-tech electronics we use every day. More recently, batteries have become a crucial component in the transition of our transport fleet from fossil fuels to electric power.

He who invents a better battery will never have to work again.

As a result of this it's only natural that squillions of dollars are being poured into exploring alternatives to today's chemistry-de-jour: the lithium-based secondary cell.

Every now and then you hear that a team of researchers have made a breakthrough and that their "revolutionary" aluminium/air or cardboard/rose-petal batteries are just five years from production.

Five years on... we're still waiting.

But now (if the reports are to believed, it's the humble and abundant element zinc (Zn) that is coming to our rescue.

Yes, it seems that a pairing of zinc and nickel offers (in the lab at least) great promise as a safer alternative to lithium.

Actually, I already have a handful of NiZn cells at the workshop. They've been sitting around for a couple of years; I must test them and see if they've lost much capacity during this period.

According to the report, the *new* NiZn technology has an energy density that challenges lithium cells and a charge-cycle life that's also pretty close.

So what's benefit of this new NiZn chemistry?

Well it's simply safer, we're told.

Instead of having your cellphone or fitness bracelet explode in flames and turn your flesh into a charred mass of pain, NiZn cells are more likely to die quietly in their sleep -- apparently.

So is this the breakthrough battery technology we've been waiting for?

No.

To attract widespread adoption, the next battery technology must be far more energy dense than current technologies, both from a mass and volume perspective. To put it simply, we've got to pack more watt-hours into less space and weight.

This is essential if we want our electric cars to go further on a charge and our smartphones to run for a week or more without getting the ominous "battery low" warning.

To be honest, I haven't seen anything on the horizon yet.

Sure, researchers and battery companies keep firing off press releases such as the one that prompted today's column but they are all struggling to come up with "the next big thing" in battery technology and even when they do, storing such large amounts of electrical power in such a small volume will always carry enormous safety risks.

Even if the chemistry itself is relatively benign, pushing huge amounts of current through a shorted circuit will always produce pyrotechnic effects with a decidedly negative outcome. Sadly, at least in the case of EVs, large amounts of current is exactly what the batteries must be capable of producing.

Yes, petrol and diesel have a much higher energy density that existing battery technologies but it's very hard to make these liquid fuels produce a catastrophic explosion in the way that a shorted battery will. Although there is more energy in a gallon of petrol than in a stick of dynamite, conditions have to be near-perfect for petrol to release all that energy at once. The stoic ration (ratio of air and fuel) has to be within very strict bounds and a source of containment must also be present or all you get is a fire that consumes the fuel (relatively) slowly with little physical force.

Drop a short on your 75KW/H battery and you'll find that it'll make an impressive "bang" regardless of what else is going on. No contest -- petrol is safer in most cases!

So I guess that the perfect battery technology that nobody's even close to developing will be energy-dense, cheap, have benign chemistry and be automatically limiting in terms of its energy output under provocations such as circuit failures or mechanical insult.

Don't worry... it *will* happen, but just not today, or tomorrow, or next week, or even next year.

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