Want to know the future of electric cars? First you have to understand where battery technology is going, and more importantly—when. You think, if Tesla is selling fast, long-range EVs today, and Chevy has announced its “200-mile” Bolt, why can’t BMW build its own new 200-mile i-model before 2020?
You may have heard about the remarkable Envia lithium-ion battery, or should I say the rise and fall of said infamous battery. The story bears repeating, because it explains a lot about the pitfalls of EV development (and marketing)—why some electric car manufacturers make claims that are aggressively optimistic, while others have more conservatively opted for the battery in hand, over the two prettier ones in the bush.
A lithium ion is a charged particle, a few atoms with the negatively-charged electrons and positively-charged protons not balancing out. A lithium-ion battery is a fairly simple device, as long as you ignore the details and permutations. Lithium-ion batteries have two electrodes (one with a positive charge and the other negative) separated by a typically liquid electrolyte that enables the flow of charged lithium ions from one electrode to the other. The electrodes are labeled either cathode or anode, depending on which way the current is flowing—charging or discharging.
Editor's Note: This post, authored by Chris Llana, appears on BMWBLOG. Check it out here.
Lithium in its elemental state is a metal—a very combustible metal. So lithium ion batteries generally use a safer lithium compound instead (for example—Lithium Cobalt Oxide (LiCoO2)). The lithium compound is in the cathode; the anode has traditionally been graphite. A good battery, but pretty low energy density, particularly for electric cars. If you want long range, that basic battery would need to be really heavy.
So, back to the Envia story. Two engineers founded the company in 2007, on the strength of a cathode patent licensed from the Argonne National Laboratory (a U.S. government facility outside Chicago). That nickel, manganese, and cobalt (NMC) -based cathode yielded a battery with a 66% better performance than standard Li-ion batteries.
That got them initial funding, and they started working to turn Argonne’s discovery into something commercial. But by 2009, however, their marketing efforts had not borne fruit, and they were about to go belly up. They turned to their venture capitalist for help, bringing him in as CEO of the company, along with another bit of cash.
If they could win a government competition with their battery tech, they thought the resulting grant would solve their money problems. The new cathode they developed yielded a 280 watt-hour per kilogram (Wh/kg) battery. (watt-hour is a measure of energy) That laboratory performance was very good, but certainly not jaw-dropping.
But for the competition, they added a silicon-carbon anode—a potential game changer. A standard graphite anode can absorb only so many lithium ions. Silicon, however, can absorb a LOT more—ten times more than graphite. Each lithium ion represents so much energy. The more of them you can move from one electrode to the other, the more energy you can store. So silicon is big!
Which is the problem, really. During the charge/discharge cycle, the insertion of the lithium ion into the silicon causes it to expand 400%. Unless you can accommodate that expansion, the electrode self-destructs, pulverizes (like water freezing in a pipe, only much worse). The battery would give you great range, but only for a couple of charge cycles.
The Envia engineers thought they could solve the problem. They built their battery and had it tested by an independent lab. It yielded a remarkable 400 Wh/kg! Not only that, but Envia claimed they could build it for half the cost. They got their $4 million grant.
Lots Of Questions
The big boys took notice, to wit, General Motors. Notwithstanding opposition from their engineers (who were suspicious of the small start-up with no track record), the GM brass wanted Envia’s battery for their 2015 model year Volt, and for a planned 2016 BEV with a 200-mile range. It would be a game changer. They started paying Envia $2 million per quarter to commercialize the battery. For the 200-mile EV, GM needed a 350 Wh/kg battery pack that could last 1000 cycles with little degradation. That went in the contract; the battery also had to be ready by October 2013, with a further 10 months allowed for final optimization. After that, no changes.
When the time came and Envia’s battery was tested, it failed miserably, not coming close to the earlier test results. On its face, that is. For the government competition, Envia had claimed their battery yielded 400 Wh/kg, and that it had been tested to 300 charge/discharge cycles. True. What they had not revealed was that the 400 Wh/kg figure was only produced for the first three charge cycles. The stored energy dropped precipitously after that. By cycle 300, the battery was only good for 237 Wh/kg. The culprit, of course, was the extreme volumetric expansion. Envia had not been able to devise a fix.
It also turned out that the anode material was not proprietary to Envia, as had been claimed, but had secretly been sourced from a Japanese supplier. Envia’s founders had hoped they could solve the problems in time, had hoped they would become hugely rich, but their miracle had not come home. They had even kept Envia’s CEO in the dark.
It would seem that GM’s plans for the Envia battery to power its 200-mile car in 2016 had been smashed, but GM claimed it had an alternative battery in the wings. One report, however, suggested that it was too expensive. Another speculated that the car might show up as early as 2018. GM hasn’t shed any light.
There are other possibilities, of course (but not for 2016—maybe a few years later).
California Lithium Battery (CalBattery)
In 2009, another small company — California Lithium Battery (CalBattery) — started having discussions with a scientist at Argonne National Labs (them again). Those discussions ultimately led to the Argonne scientist becoming the Chief Technical Officer for CalBattery, to lead the development of his patented lithium-ion anode into a commercial product.
That anode also used silicon to greatly increase the energy density of the battery, but adopted a novel approach to accommodate the 400% volume change during the charge/discharge cycle. The Argonne scientist had discovered that a gas deposition process to embed silicon into a graphene matrix could provide enough cushion to prevent the pulverization of the electrode. (Graphene is a two-dimensional hexagonal lattice with one carbon atom at each vertex—basically a one-atom thick form of carbon, with remarkable properties.)
In the fall of 2012, CalBattery had produced a sample battery and announced it had been independently tested to store 525 Wh/kg of energy. By comparison, commercial lithium batteries at that time had energy densities between 100 and 180 Wh/kg. This was huge news! In February 2013, CalBattery said it could make the anode material commercially available by 2014.
By December 2013, however, CalBattery said it was working to scale up production, and expected to produce anode material in commercial quantities “in a few years.” Initially working toward supplying its battery tech for use in EVs, CalBattery later shifted its focus to consumer electronics, which would bring in revenue faster. They discovered that getting its batteries into EVs could take up to seven years. EV batteries are made up of many cells. The cell would have to be proven, and then the battery pack would have to be developed and tested, and then the car would have to be tested—extensively. Car makers are very focused on product liability issues.
By the middle of 2014, CalBattery had teamed up with another small company called CALEB, pooling their respective cutting edge battery chemistries. They have been scaling up their production methods, with the goal of keeping costs down. They are now optimizing their third-generation continuous-flow reactor (a proven design adopted from another industry). They hope to be producing thousands of tons by around 2018. Some OEMs have already been given samples for testing, and one large corporation has reportedly tasked them with building a cell phone battery.
This effort seems one of the most promising over the next five years, but it is just one of many, mainly government and academic research programs ongoing worldwide, all working to solve a piece of the puzzle. The academic people are publishing their results, perhaps trolling for financing. The government scientists want their work to end up in a product. The big corporations, on the other hand, are pretty quiet about their progress.
Secretive may be a more apt description. VW recently acquired a 5% stake in a Silicon Valley start-up called QuantumScape, a company that is pioneering a solid-state lithium battery based on Stanford University research. Neither the company nor VW is offering a description of the battery, but a number of people have done some research into patents and some of the Stanford research conducted by the founders of QuantumScape; the clues are compelling.
The new battery might use something called the All-Electron Battery (AEB) effect—no ions shuttling back and forth, just speedy electrons. A thin film of a synthetic material called antiperovskite could be involved, doped with aluminum material, which could enable the use of metallic lithium (instead of a lithium compound). All of which would give a very high energy density, and very little degradation with repeated charge/discharge cycles—thousands of them.
VW has suggested this new technology could give their e-Golf a 700-kilometer range, more than triple what it is now. VW says development and testing are progressing enough to permit a decision on its future use by this July. Another intriguing development.
With batteries having up to 500 Wh/kg energy densities potentially coming within the next five years, what sort of energy densities do we have now?
Tesla leads the pack with its small Panasonic cylindrical cells (thousands of them in a pack). 233 Wh/kg. These are the same sorts of cells used in consumer electronics, which generally have higher energy densities, but at the expense of longevity and safety. When the battery in your cell phone dies, just buy a new battery or upgrade to a new phone. No big deal, and the life-span of consumer electronics is typically a couple of years. Not so with cars, but Tesla has done a good job of managing the downsides through active cell monitoring, and careful design to limit heat build-up and protect the cells from puncture. Because the individual cells are so small, each produces a very small amount of energy, so if cooled effectively, there is less chance for a fire.
Other manufacturers are using large format cells for EVs (simpler to package), and therefore need to use battery chemistries that are inherently safer. The tradeoff is lower energy density.
Panasonic also supplies battery cells for the VW e-Golf, although these are larger prismatic cells having an energy density of 170 Wh/kg. VW says its short-term roadmap is projecting an increase to 220 Wh/kg.
Nissan-Renault have been using batteries made by NEC (but they seem to be shifting to LG Chem). The current LEAF batteries have an energy density of 155 Wh/kg; the Renault Zoe gets a 157 Wh/kg battery.
The Smart EV uses a 152 Wh/kg battery from Deutsche/ACCUmotive.
The Mitsubishi i-Miev uses a battery from Lithium Energy Japan (GS Yuasa/Mitsubishi) — 109 Wh/kg.
The Bosch/Samsung battery used in the Fiat 500e is rated at 132 Wh/kg.
The Toshiba lithium-ion battery used in the Honda Fit EV comes in last with an energy density of just 89 Wh/kg.
The source for most of these values did not have a rating for BMW’s i3 battery. I found another reference that listed the energy density for the i3 as 95 Wh/kg. (not sure if this is for the cell or the pack) Samsung says the nickel-cobalt-manganese cells used in the i3 have the industry’s highest volumetric energy density (Wh/per liter). In other words, heavy, but they don’t take up much space.
The choice of any particular battery chemistry is a compromise. Car manufacturers not only look at energy density, but also safety, longevity, power density (rate of energy release), charging rate, reliability, and cost.
They want a battery supplier they trust, with a reputation to uphold, and having the resources to perform on a contract. Those qualities make it unlikely that one individual would be able to make overly optimistic claims (and get away with it). Those qualities, however, also tend to favor an incremental development path to new technology, rather than relying on the proverbial big scientific breakthrough. It may be that the small startup actually achieves the breakthrough, but would a BMW bet on that before it’s been proven?
BMW’s lithium-ion battery partner is Samsung SDI, which is collaborating with the United States Advanced Battery Consortium (headed by General Motors, Ford, and Chrysler) to develop a new lithium-ion battery. According to Samsung SDI’s technology roadmap, they expect to produce an advanced cell having an energy density of about 250 Wh/kg, sometime around 2019. Until that time, their roadmap shows a battery chemistry with just 130 Wh/kg. (!)
Samsung Investment Ventures Corp. has also provided funding to Seeo, a company that is developing advanced lithium polymer batteries. Their cells, which use a non-flammable solid polymer electrolyte, are now testing at a very respectable 350 Wh/kg, and aiming to achieve 400 Wh/kg.
Assuming BMW will stick with Samsung as its lithium-ion cell provider, it would be crazy for them to plan a new model roll-out before Samsung’s 250 Wh/kg battery becomes available in commercial quantities (circa 2019-2020).
Will there be 400 Wh/kg batteries available before then, or in the same time frame. Hopefully, yes. Should BMW plan on designing a new i model based on a small company’s predictions? Probably not. Should they be tracking those developments and testing any available samples? Absolutely. Undoubtedly Samsung is doing the same thing, and would be ready to license the best proven technology, if available at a commercially attractive price. But changing batteries late in the planning, design, and engineering development process for a new car model would be chaotic, to say the least.
Samsung SDI Roadmap
Battery progress drives the release of new BEV models. Whether to meet cost targets, range targets, or performance targets, the development of successful new EV models will be driven by the performance of the batteries that are commercially available. That holds true for the Tesla Model 3, the Bolt, and BMW’s next new i model.
Modern electric cars are at a very early stage in their development, and yet they are already so good that we want much more, and we want it now. More models, more performance, more range, less weight, and of course much cheaper. But we understand all this is new, so we’re willing to wait a year or two to get all that. Ha!
You haven’t seen anything yet. Wait five years, or ten—lithium-sulfur batteries are on the way, and after that, lithium-air! Or maybe they’ll all be blown away by something else.