STATE OF THE BATTERY: SOON TO BE SOLID
Battery technology, however improved, has always been the critical limiting factor in the development of electric car drivelines. But as Automate’s Harrison Boudakin reports, a move beyond the traditional liquid-cell battery could be the key that unlocks the next wave of revolution in automotive engineering
Serious change is never rooted in a single moment in time. Instead, it comes to us in slow waves of events and breakthroughs, which converge one after another until eventually, the status quo can simply stand no more.
And without doubt, the car industry’s stilted stagger towards the electric future bears witness to this in a grand way. For decades now, the mass-produced, battery-electric car has been held before us like a sort of soon-to-be-real vision of tomorrow; but lo and behold, for all the talk and hype, the path we have taken to actually get to this future has been frustratingly long and winding.
However, there’s also no doubt that in recent years, a number of key – and unexpected – accelerants have forced the industry to work harder at turning the fiction of electric cars into some kind of feasible reality. The arrival of Elon Musk’s pioneering Tesla brand was one such catalyst; the industrial and political chaos of the Volkswagen Dieselgate scandal was another.
And now, as legislators and politicians pressure automakers to step away from their beloved internal combustion engine like never before, we are witnessing another critical accelerant loom on the horizon – and it comes to us in the form of a new breakthrough in battery technology.
Now it is true to say that the liquid-state, lithium-ion battery has absolutely been the great focal point of scientific and economic investment in recent electric car development. And yes, this R&D has produced some genuine advancements in the capabilities of lithium-ion technology,
with the best electric cars now offering more
than 500km of driving range, and the potential for relatively fast charging. But however
improved these batteries are, liquid cell lithium-ion remains a deeply compromised and problematic technology, particularly in the context of road car design.
At the heart of the matter is the challenging relationship between energy density and cell safety.
In much the same way as phone manufacturers are constantly looking to develop smaller batteries with greater levels of power, automakers are also desperate to squeeze as much energy into as small a battery cell as possible. But the challenge is that increasing the energy density of a cell also makes it proportionally less safe. Liquid cells, as we know from the case of the exploding Samsung Galaxy phones, are extremely volatile when they malfunction, particularly when the malfunctions are caused by engineers pushing the limits of energy density too far.
Put simply, the problem with lithium-ion batteries is that they contain liquid – because as we know from chemistry, liquids almost always promote more unstable cell behaviour and are very vulnerable to thermal runaway situations.
As much has been apparent in a number of high profile accidents involving Tesla cars, where the impact of a collision has led to electrical fires, which have subsequently burned for hours at incredibly high temperatures. As a result, manufacturers have had to be extremely careful in the way they package their cells in the chassis, adding heavy layers of protection to prevent the batteries from being punctured.
But even with protection, it’s clear that engineers are rapidly approaching the limits of liquid lithium-ion technology. So to make batteries that are lighter, smaller and more powerful – the Holy Trinity in automotive terms – manufacturers are now hedging their bets on something a little more… solid.
Yes, without a doubt, solid state batteries will be the key that unlocks the next – and very important – stage of the electric revolution.
While no manufacturer has actually put a solid-state cell into mass production yet, many automakers are now talking openly about their investments in the technology.
At the Frankfurt Motor Show last year, Porsche made it clear that their next generation of 911 and Boxster models will feature some sort of electrification – and they believe only a solid-state battery design can offer them the kind of performance, light weight and durability that Porsche owners expect.
Meanwhile, industry giant Toyota is also throwing their considerable weight behind the technology, stating that a solid-state battery design will be at the heart of their first mass-market, all-electric model, to be launched in the early 2020s.
And finally last December, BMW announced a partnership with a Colorado-based firm, Solid Power, to boost their competency in the field. Solid Power, with its links to the University of Colorado, already has facilities working on small-scale cell research, and BMW predicts that production-ready versions of the batteries will hit the market around 2025.
That coincides with research from prominent analysts suggesting that the cost of mass manufacturing solid-state batteries will likely reach parity with internal combustion engines by the mid-2020s. In other words, in dollar terms, that means the price of producing one kilowatt hour of electricity falling to around $100 – down from the $200 per kilowatt rate of the present day.
So if it’s true that this technology is relatively imminent, it’s probably worth exploring a little bit of the science behind the solid-state revolution.
Put simply, using a solid-state cell allows engineers to unlock a lithium-metal anode; and in terms of how much charge it can store per unit of mass and volume, lithium-metal is about as good as it gets.
That means far lighter batteries with far higher levels of energy density. Unlike conventional lithium-ion designs, solid state cells also don’t need to be stacked or ‘layered’ closely together and then linked via electrical connectors. This gives engineers far more flexibility when laying out the batteries within the chassis, ultimately liberating more space for passengers and giving designers more freedom to innovate around the aesthetics of their future models.
But the real clincher is the safety factor. With a solid-state battery, the chemical reaction that would traditionally cause a short-circuit in a conventional lithium-ion design in this case also produces an inert electrolyte, which just so happens to deny the fuel that would stoke a fire.
So what you end up with is an incredibly stable cell, giving engineers licence to increase the energy density without compromising safety. That’s what’s attracting the world’s automakers to the technology: it promises to deliver a massive boost in range and power, while at the same time helping to put a lid on the current scourge of EV batteries, which is weight.
Still, challenges remain. Engineers continue to work on ensuring the lifespan of the cells is long enough to meet the demands of mainstream automotive design. As yet, no one appears to have mastered how to produce a cell that will last 200,000km or more – a critical stumbling block.
For the record, none of the companies currently working on the technology have disclosed their targets for the lifespan of solid-state batteries, but Toyota’s Chairman – the man dubbed “the father of the Prius” for his work on that revolution vehicle 20 years ago – says no one would dare launch a car with a battery life that isn’t absolutely acceptable to the market.
Clearing that hurdle will leave the automotive industry on the precipice of a significant revolution in drivetrain technology. More than ever before, we are entering an epoch where automakers are squeezed between the idealistic demands of politicians and the pragmatism of the buying public. And as a piece of engineering that seemingly offers a viable solution to this challenging remit, the solid-state battery does appear to be the industry’s best and brightest hope.
Written by Harrison Boudakin for AutoMate Training, an industry leading provider of online, on-demand digital training.
Visit www.automatetraining.com for a free 14-day trial.