Motor Mouth: The top battery tech you can expect in tomorrow's EVs

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For the last five years — as long as the electric vehicle has been the predominant new technology on the horizon — we’ve fretted, nay agonized, about range. We needn’t have.

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Oh, we were right to be anxious, but mistaken regarding what to be anxious about — what we should have been worried about is charging time. It’s all well and good, to bump your EV’s range to 600 kilometres of range from 300, but if it takes twice as long to charge, well, you’re not really that much further ahead, are you? We’ve also been reminded that the average North American commute is far less than 100 kilometres, and that huge batteries are a costly drag on EV economics. Hence GreenCarReports’ recent contention that “range is a red herring.”

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Much more important than how far we can “‘range” is how quickly we can get back on the road, a point made clear by the U.S. Department of Energy’s research, which found that electric vehicle owners with access to fast charging stations boasted more than 25 per cent more “annual electric vehicle miles travelled” (eVMT in government bureaucratese). More importantly, faster charging would mean batteries could be made smaller, making EVs more affordable while still retaining range “confidence.”

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Charging times, then, are the real anxiety-inducers. So, here’s a roundup of the technologies that might get us back on the road more quickly. Some might be available soon, while others may take more time than we hoped for.

Silicon graphically improves battery performance

Recharging a battery is largely dependent on the free flow of electrons between the two electrodes — the cathode (the “+” terminal) and the anode (the “-“ side). The limiting factor in current batteries seems to be the anode, which in current batteries is made of graphite. Adding silicon, say researchers from numerous laboratories, renders a battery both more powerful and speedier to recharge. So, while the big news from Tesla’s Battery Day — the introduction of the new, larger 4680 cell — promised longer range, the even bigger news in the EV world might have been the continuing research from a small startup called Enevate that is looking to seriously bump charging speeds with pure silicon anodes.

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There is significant work to be done still before we’ll see such fast charging in production EVs. While Enevate is claiming its latest batteries can be charged to 75 per cent in just five minutes, there is a huge difference between trickling a few milliamps into a laptop-sized battery incredibly quickly and quite another to pump 600 amps into a car without blowing things to smithereens. Nonetheless, we’ll no doubt see some faster-charging batteries in electric vehicles within the next three to five years, at least in part due to silicon and other anode enhancements like niobium oxide.

Almost here: solid-state batteries

In probably the most surprising EV announcement last week — one that didn’t happen at Battery Day, of course — was Daimler’s statement it will soon be producing solid-state versions of its battery-powered Mercedes eCitaro electric buses. Solid-state batteries differ from traditional lithium-ion cells in that they typically have a solid material (ceramics, polymers, etc.) conjoining their electrodes rather than having them swimming in a bath of liquid electrolyte. The result is a more compact cell, Daimler claiming 25 per cent increased power density. Mercedes’ bus engineers used the increased efficiency to squeeze a whopping 441 kWh of lithium ion into its articulated bus.

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However, there’s still much work to be done before solid-state can really outclass traditional lithium-ion. Daimler, for instance, is boasting the eCitaro’s 300 kW charging ability, hardly turtle-like to be sure, but still darned close to two hours for a complete charge. Indeed — and this shows the difficulty in developing new battery technologies — Mercedes says that since “solid-state batteries are restricted in their fast-charging capacity,” it will keep offering more traditional lithium nickel manganese cobalt oxide (NMC) batteries in its buses because they’re still “better suited to high charging current.” In other words, we’re still need to wait a while — between five and 10 years, say most experts — for a (solid-state) battery revolution. One thing that should warm Canadian cockles, however, is that Mercedes’ solid-state batteries are being developed right here in Canada, their chemistry the result of research by Hydro-Quebec’s Center of Excellence in Transportation Electrification.

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We can dream, can’t we?

If there’s one technology that reveals the difficulty of developing new battery chemistries, it’s the holy grail of power-dense EVs — the lithium-air battery. The biggest issue for electric vehicles — besides range … er, recharging anxiety — is all the weight they have to lug around. While a typical 80-litre gas tank fully filled weighs around 55 kilograms, a 100 kWh battery can weigh almost a half metric tonne. The reason that gasoline is so much more energy dense is because, despite its relative inefficiency, it doesn’t need to carry around its entire energy source. Indeed, because one part gasoline combines, in a perfectly stoichiometric blend, with 14.7 times its weight in air, those 80 litres are equivalent to more than 850 kilograms of fuel. The problem for current batteries, of course, is they must carry all their “fuel” inside the car.

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Hence the benefit of lithium-air. All batteries work on what’s called an oxidation-reduction (redox) principle; lithium from the anode gets oxidized, while oxygen molecules are reduced at the cathode. That’s the magic of the lithium-air design. By sourcing the needed oxygen from the air (as a combustion engine does), rather than storing it in the battery, a Li-Air battery can be 10 times more energy dense than a traditional Li-ion version. That means a smaller battery can generate increased range.

Unfortunately, according to the Institute of Electrical and Electronics Engineers, lithium-air batteries are notoriously hard to charge, their charging efficiency some “15 to 25 per cent lower than what we would expect from lithium-ion batteries.” Combined with other technical issues — removing battery-damaging water vapour and carbon-dioxide from our atmosphere before it hits the battery, and pure lithium anodes that are even more prone to fire — the ultimate in range-extending batteries are, at best, a long way off. As Harry Hoster , director of U.K.-based researcher Energy Lancaster , says: “The lithium-oxygen battery is a bit like nuclear fusion. There are big potential wins, but there are many loose ends.”

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The roadblock: Charging infrastructure

While early adopters have proven willing to put up with long waits for recharging, most experts make plain that even the 20 to 30 minutes a long-range electric vehicle would need from a current state-of-the-art 35 kW charging station isn’t quick enough for mass adoption. The Swiss École polytechnique fédérale de Lausanne goes even farther, predicting that “electric cars will only be truly competitive when it doesn’t take longer to charge them than it does to fill a gas tank.”

Electric cars will only be truly competitive when it doesn’t take longer to charge them than it does to fill a gas tank.

École polytechnique fédérale de Lausanne

In other words, their estimates for what the consuming public will accept from an all-battery-powered fleet might range from five to 10 minutes. Do the math with a Tesla 100 kWh battery needing an 80 per cent charge and you’d require something akin to a 500-kW to one-megawatt charging station for ICE-equivalent back-on-the-road performance. The former seems almost within the realm of possibility as we’re already seeing smatterings of 350kW spots, and 450 kW might be common by 2030.

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Unfortunately, those attainable gains are about the limit to be expected before our post 2030 (or 2035) all-electric future. Faster chargers, meanwhile, will be problematic, being more complicated — that should be read expensive — automatically operating “flash” units (sometimes called “opportunity” charging) that are limited, at least currently, to about 600 kW. Any discussion of super-duper-fast, three-MW units — as promised, again, by Mercedes-Benz’s commercial unit — are only for trucks and buses, far larger systems than will see use in common, everyday automobiles.

So, while it might be someday possible to “handhold” such a 500-kW charger as we do a hose from a fuel pump, the chances that we’ll be conveniently topping up with 1MW in the near future would seem a pipe dream for now. Indeed, batteries may not be our electric future’s most vexing problem; there may well come a time when batteries will be available that can charge more quickly than our infrastructure can supply electrons.

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And lest we forget

Despite the controversy surrounding Nikola and General Motors, fuel cell vehicles — “fool cells,” if you’re a Tesla fanboy — also got some good news last week, no less than the Bank of America proclaiming hydrogen is at a “tipping point” ready to explode into a US$11 trillion industry by 2050. Morgan Stanley, meanwhile, extolled the many virtues of a wind-powered green hydrogen network.

As for mobility industry, while a wide-ranging hydrogen-supply infrastructure will be difficult and costly to build, fuel-cell electric vehicles (FCEVs) can already recharge in the five minutes that BEV engineers still see as a pipedream. Meanwhile, the Hydrogen Council predicts that refueling an FCEV will become price-competitive with ICEs with mass production. That’s important for widespread FCEV adoption, but even more vital for trucking since long-distance commercial haulage is expected to go FCEV rather than battery-powered in its quest for zero emissions. And finally, again referring to Mercedes’ commercial business, those eCitaro buses with solid-state batteries will be available with hydrogen-fueled range extenders.

Author’s note: Eagle eyes will note that there’s a substantial number of new developments left untouched by this discussion, lithium-sulfur chemistries and a new wireless battery management system from General Motors, not to mention the always titillating, 1,000-mile aluminum-air battery, to name just a few. They are not to be ignored and will be discussed in future Motor Mouths as technologies leap ahead.