Silicon is a staple of the digital revolution, shunting loads of signals on a device that’s likely just inches from your eyes at this very moment.
Now, that same plentiful, cheap material is becoming a serious candidate for a big role in the burgeoning battery business. It’s especially attractive because it’s able to hold 10 times as much energy in an important part of a battery, the anode, than widely used graphite.
But not so fast. While silicon has a swell reputation among scientists, the material itself swells when it’s part of a battery. It swells so much that the anode flakes and cracks, causing the battery to lose its ability to hold a charge and ultimately to fail.
Now scientists have witnessed the process for the first time, an important step toward making silicon a viable choice that could improve the cost, performance and charging speed of batteries for electric vehicles as well as cell phones, laptops, smart watches and other gadgets.
“Many people have imagined what might be happening but no one had actually demonstrated it before,” said Chongmin Wang, a scientist at the Department of Energy’s Pacific Northwest National Laboratory. Wang is a corresponding author of the paper recently published in Nature Nanotechnology.
Of silicon anodes, peanut butter cups and packed airline passengers
Lithium ions are the energy currency in a lithium-ion battery, traveling back and forth between two electrodes through liquid called electrolyte. When lithium ions enter an anode made of silicon, they muscle their way into the orderly structure, pushing the silicon atoms askew, like a stout airline passenger squeezing into the middle seat on a packed flight. This “lithium squeeze” makes the anode swell to three or four times its original size.
When the lithium ions depart, things don’t return to normal. Empty spaces known as vacancies remain. Displaced silicon atoms fill in many, but not all, of the vacancies, like passengers quickly taking back the empty space when the middle passenger heads for the restroom. But the lithium ions return, pushing their way in again. The process repeats as the lithium ions scoot back and forth between the anode and cathode, and the empty spaces in the silicon anode merge to form voids or gaps. These gaps translate to battery failure.
Scientists have known about the process for years, but they hadn’t before witnessed precisely how it results in battery failure. Some have attributed the failure to the loss of silicon and lithium. Others have blamed the thickening of a key component known as the solid-electrolyte interphase or SEI. The SEI is a delicate structure at the edge of the anode that is an important gateway between the anode and the liquid electrolyte.
In its experiments, the team watched as the vacancies left by lithium ions in the silicon anode evolved into larger and larger gaps. Then they watched as the liquid electrolyte flowed into the gaps like tiny rivulets along a shoreline, infiltrating the silicon. This inflow allowed the SEI to develop in areas within the silicon where it shouldn’t be, a molecular invader in a part of the battery where it doesn’t belong.
That created dead zones, destroying the ability of the silicon to store lithium and ruining the anode.
Think of a peanut butter cup in pristine shape: The chocolate outside is distinct from the soft peanut butter inside. But if you hold it in your hand too long with too tight a grip, the outer shell softens and mixes with the soft chocolate inside. You’re left with a single disordered mass whose structure is changed irreversibly. You no longer have a true peanut butter cup. Likewise, after the electrolyte and the SEI infiltrate the silicon, scientists no longer have a workable anode.
The team witnessed this process begin immediately after just one battery cycle. After 36 cycles, the battery’s ability to hold a charge had fallen dramatically. After 100 cycles, the anode was ruined.
Exploring the promise of silicon anodes
Scientists are working on ways to protect the silicon from the electrolyte. Several groups, including scientists at PNNL, are developing coatings designed to act as gatekeepers, allowing lithium ions to go into and out of the anode while stopping other components of the electrolyte.
Scientists from several institutions pooled their expertise to do the work. Scientists at Los Alamos National Laboratory created the silicon nanowires used in the study. PNNL scientists worked together with counterparts at Thermo Fisher Scientific to modify a cryogenic transmission electron microscope to reduce the damage from the electrons used for imaging. And Penn State University scientists developed an algorithm to simulate the molecular action between the liquid and the silicon.
Altogether, the team used electrons to make ultra-high-resolution images of the process and then reconstructed the images in 3-D, similar to how physicians create a 3-D image of a patient’s limb or organ.
“This work offers a clear roadmap for developing silicon as the anode for a high-capacity battery,” said Wang.
More information: Chongmin Wang et al, Progressive growth of the solid–electrolyte interphase towards the Si anode interior causes capacity fading, Nature Nanotechnology (2021). DOI: 10.1038/s41565-021-00947-8
Founders of Lectric eBikes (based in Phoenix AZ) Robby Deziel and Levi Conlow
All Levi Conlow’s dad wanted was an electric bike that didn’t cause sticker shock.
So when he approached his son and his son’s best friend Robby Deziel with the proposal that they put their heads together to make obtaining his e-bike dream come true, the new college graduates started thinking.
“My dad was just entering that phase of his life when he wanted an e-bike for himself and my mom. Their friends had e-bikes,” Conlow said. “He was frustrated. He couldn’t find one for less than $2,000 or $3,000.”
This is when the professional exploration path of Conlow — equipped with bachelor’s and master’s degrees in business entrepreneurship and leadership from Grand Canyon University — and Deziel — who has a bachelor’s degree in mechanical engineering from the University of Minnesota — merged with dad’s personal quest.
“Our parents and their friends were said they’d buy one if we figured it out,” Conlow said. “The dream of being able to work for ourselves was always cool and we just went for it.”
Deziel added, “We put our heads together to make them more accessible for everyone without sacrificing quality.”
That union resulted in Lectric eBikes, Conlow and Deziel’s electric bike company that has become a monster in the industry just over a year after launching in Phoenix in 2019. To date, more than 15,000 of their bikes have sold. In June, the company sold $3.5 million worth of bikes alone, Conlow said.
This success rides on their two models, the original XP and the customer demand-inspired XP Step-Thru, each of which bears a more wallet-friendly price tag of $899.
The more they researched and got into the nitty gritty, they saw no reason for consumers to pay into the four digits.
“Other companies just wanted a higher profit margin. We’re really committed to a community of riders,” Conlow said.
Lectric is part of a global e-bike market that was valued at $23 billion in 2019, according to an Analytical Research Cognizance report. It’s also projected to be worth $46 billion by 2026, according to Fortune Business Insights.
This commitment has created a thriving business model that has relied on word-of-mouth. The idea: Deliver a product that generates strong support from customers, who will become natural advocates when they are stopped on the street by curious bystanders.
“We make it so customers absolutely love and support us. It shows the power of the customer advocate and what wonders they can do,” Conlow said.
Beverly Lambert has been one of those advocates from the start. She and her husband own two XP’s and have a Step-Thru on order.
Her husband used to own a bicycle store and they had owned every kind of bike on Earth. The last thing she wanted was another new-fangled version. But her husband bought them XP’s anyway.
She tried to return hers but was convinced to try it just once.
“I was like, whoa, this is really easy to ride,” said Lambert, who was impressed at its performance up a gravel hill. “I thought, ‘What just happened?’”
Today, Lambert rides it every chance she gets. She’s currently on a camping trip, where she and her husband use it to ride around the campsite, hiking trails and to run quick errands. She takes it on bike trails and the reserve area near her Norco, California, home.
Lambert has helped sell many Lectric bikes to friends and complete strangers who became friends after spotting her on the road and asking her about her e-bike.
Separating from the pack
Conlow and Deziel have been pals since the sixth grade in their hometown of Lakeville, Minnesota. College geographically separated them but they kept in touch and hoped to get into some kind of business together after they graduated.
They did. But for a while, it seemed their entrepreneurial dream would be just that.
At first, Conlow and Deziel, who moved to the Valley, designed several renditions and got fine tuning feedback from their parents.
Originally, they envisioned a sleek, high-tech version aimed at a young audience. They designed the bikes, sourced the manufacturing and were poised to dazzle at tradeshows.
But what they found was that their bike wasn’t practical for the audience that really wanted it. Among the complaints: people couldn’t fit on it; they wanted a more comfortable experience; and its traditional bicycle look meant it needed to be hauled on a car rack with other accessories, which quickly negated the bike’s low price.
“We could not sell those bikes to save our lives,” Deziel recalled. “With all of those lessons in mind, we went back to the drawing board.”
They emerged with what would be their flagship model, the XP. This version has smaller diameter wheels and is lower to the ground, allowing riders of various heights to easily get on and off. The handlebars and seats are adjustable and, because it’s a folding fat tire bike, the increased air volume allows for a more comfortable ride and no rack is needed.
It fits neatly into the trunk of Deziel’s Honda Civic. It can do mild off-roading onto gravel and hiking trails.
The bike also is assembled when shipped. All customers need to do is pump up the tires and make seat and handlebar adjustments and they’re good to go.
All of these, Deziel said, would be key factors that separate them from the pack.
“With some, you need to put the wheels and handlebars on and build the seat. One company asks you to build the brakes,” Deziel said. “The way we see it, we are the bike people. Not all of our customers are mechanics.”
A sudden surge in orders
Early on, no one was biting. Their parents were the only customers. Deziel was evaluating his bank account and figuring out how many days he could afford to live here before having to move back home.
“We had no inventory. No money. We were in debt to my dad,” Conlow said.
They took a gamble with the little money they did have, made eight bikes and sent those to influencers. With no funds to partner with them, the guys crossed their fingers that at least a couple of the influencers would post positively about their bike.
“We were on pins and needles,” Conlow said.
Soon, one influencer reached out and said he liked the bike would post a review. Still, they were skeptical. They did not set up a bank account and decided to put up a website at the last minute.
“No way people are going to buy a bike on the first day,” Conlow said of their thinking at the time. “We planned to make an account later.”
The first day the influencer’s video posted, $30,000 in Lectric bikes were sold. Over the next 24 hours, another $30,000 in sales, Conlow said.
“We knew we had other videos scheduled to come out after that first day,” Deziel said. “I thought, ‘I can’t believe this, this is crazy… oh man, it’s about to get even crazier.’”
By the time the company was 10 days old, a second influencer video had posted, generating $120,000 a day in sales.
Needless to say, that company bank account was set up real quick.
At the 21-day mark, Lectric sold $1 million in pre-orders. For the first few months, Conlow and Deziel worked out of a Phoenix garage doing $1 million a month. They worked 18-hour days and personally answered emails and calls.
“We were simply overwhelmed. We didn’t really have time to appreciate it because we were consumed by it. We were just trying to hold on,” Conlow said. “But after having nothing, we were excited to wake up and get to work and answer those calls and e-mails.”
Since then, they’ve added to their staff and moved out of the garage into a 13,000-square foot headquarters and showroom.
Most of Lectric’s client base is between the ages of 45-80, who haven’t been on a bike in a while or have mobility issues that prevent them from riding a traditional bike, Deziel said. However, they are all outdoorsy and enjoy time in nature.
Many clients, like the Lamberts, use their bikes around campsites, explore trails while camping or to run errands into town without having to unhook their vehicle. This led Lectric’s involvement with Homes on Wheels Alliance, a non-profit that helps people struggling with homelessness through converting vans into livable spaces and assisting them with managing their finances.
So far, Lectric has sponsored two build outs and plan to do more.
“We’re extremely excited and grateful that we are able to be part of it. Just knowing the impact is very important to us,” Conlow said.
Each bike comes with a one-year warranty, one of the amenities that Deziel knew needed to be worked out as the company saw its profile rapidly rise.
“We feel a great sense of responsibility as to what we are doing with our customers. We needed to get all of this in place so people can have a positive experience,” he said.
The Step-Thru model was a response to customers asking for an even easier bike to get on and off of. The frame allows greater ease to do that.
The first day the company announced its release, it sold $300,000 in pre-orders, Conlow said. He and Deziel had to answer calls and e-mails just to handle the customer traffic. It was then when Conlow took a call from a woman named Sue who had a leg condition that prevented her from getting on to the XP. She was excited because with the Step-Thru, she could ride with her husband.
“She was brought to tears telling me about the impact the bike would have and how it’s going to change her life,” Conlow said. “It reaffirmed why we do what we do and why we design what we do. We don’t want to leave anyone out and get as many people riding as possible. It’s a very cool thing to be part of.”
What: Lectric eBikes
Where: 2010 W. Parkside Lane, Phoenix
Factoid: The global e-bike market was valued at $23 billion in 2019, according to an Analytical Research Cognizance report.
In the past two years, companies have promised electric motors producing far more torque density, measured in kilowatts per kilogram. Avid said its Evo Axial Flux motor makes “one of the highest usable power and torque densities of any electric vehicle motor available on the market today.” Equipmake says its motors develop “class leading power densities.” Yasa claims its “electric motors … provide the highest power/torque density available in their category.”
Enter Linear Labs, which says it has a motor to beat all. The company declares its Hunstable Electric Turbine (HET), perhaps with unintentional shades of Ayn Rand, “The Motor of the World.”
Watch The Video
The company told Autoblog, “The defining characteristic of this motor [is that] at very low RPMs … [for] the same size, same weight, same volume, and the same amount of input energy into the motor, we will always produce – at a minimum, sometimes more, but at a minimum – two to three times the torque output of any electric motor in the world, and it does this at high efficiency throughout the torque and speed range.”
“Hunstable” comes from the two principals: Fred Hunstable, an engineer who spent years designing the electrical infrastructure for nuclear power plants in the United States; and Brad Hunstable, Fred’s son and an ex-tech entrepreneur who helped found the streaming service Ustream, sold to IBM in 2016 for $150 million.
Linear Labs began as a father-son project to create a linear generator surrounding the shaft of an old-fashioned windmill that would provide reliable power (as well as clean water) to impoverished communities. The challenge was designing a generator able to produce sufficient power from the shaft’s low-speed, high-torque reciprocating movement. Brad said his father cracked the code about four years ago, resulting in “a linear generator that produced massive amounts of electricity from a slow-moving windmill.” What’s more, the breakthrough was modular, leading to a family of motors that has been issued 25 patents so far.
What is the Hunstable Electric Turbine?
Electric motors are well into their second century, having barely changed since Nikola Tesla patented his innovations with the modern three-phase, four-pole induction motor between 1886 and 1889. While all motors consist of similar fundamental components – copper wire coils known as windings, and magnets – the way in which those components interact is slightly different. In a radial flux motor, one component spins within the other – imagine a small can spinning inside a larger stationary one. In an axial flux design, the components spin next to each other, like two flywheels sandwiching a central, stationary plate.
Typically, the way to create more torque is to send more current into a motor or build a larger motor. Linear Labs has found another way: by combining axial and radial flux designs in a single motor.
Images: Stators and Rotors
Copper Windings Inside the Huntstable Electric Turbine: Illustrations by Linear Labs
The HET is four rotors surrounding a stator. A central rotor spins inside a stator, creating one source of flux. A second rotor spins outside the stator, creating a second source of flux. Two additional rotors lie at the left and right ends of the stator, essentially forming an AF motor. That’s two more sources of flux, making four in total. It’s essentially two concentric radial motors bookended by two axial ones.
Linear Labs says all the HET generates all torque in the direction of rotor motion. In a promotional video, Fred Hunstable said, “We call it circumferential flux, sort of like a torque tunnel.”
Generating more torque in a given volume, and having all of that torque move in the direction of rotor motion, is how the Hunstables claim, “two to three times the torque for that size envelope compared to any other motor out there. It doesn’t matter what kind [of motor] it is, we will always out-produce it.”
Furthermore, by using discrete rectangular coils inset into the stator poles, the HET needs 30% less copper than a motor of similar size. The design also eliminates end windings – lengths of copper that lie outside the stator in a typical motor, generating wasted magnetic field and heat.
Illustration by Linear Labs
What the HET could mean for future electric cars
So far, Linear Labs has inked deals with a scooter maker, with Swedish electric drive system firm Abtery, and with an unnamed firm designing a hypercar to be released within two years, utilizing four HETs. However, Brad Hunstable thinks the HET could have applications in the electric vehicle space, since the HET’s torque comes at RPMs that match the end use. Current EV motors spin much faster than the wheels, so most EVs use a reduction gear to connect a motor spinning at several thousand RPM with wheels spinning at anywhere from one to perhaps 1,800 RPM. If the HET generates the necessary torque at RPMs that match wheel speed, a carmaker could theoretically discard the reduction gear, reducing weight and improving powertrain efficiency.
Brad said testing has shown the HET in direct-drive configuration works in applications normally served by a 6:1 reduction gearbox, and it’s possible that the ratio is even higher. The downstream effects could be significant, according to Hunstable. That weight savings – the lower operating speed of the HET means fewer and lighter electronics, the company says – and efficiency gain could be used to reduce the size of the battery and thus the weight of the vehicle, saving cash and letting the manufacturer use lighter-duty components – perhaps enough to make a significant difference to the bottom line, Hunstable thinks.
The HET can also take over the role of a component known as a DC/DC boost converter, used in some EVs in situations in which the vehicle needs to trade torque for horsepower, such as during hard acceleration at highway speeds. By doing so, they use additional energy that can’t be put towards range. In general terms, EVs that emphasize performance use a boost converter, like the Tesla Model S, while ones that emphasize efficiency don’t, like the Hyundai Ioniq EV. (It should be noted that some hybrids, such as Toyota and Lexus hybrids, utilize boost converters to goose acceleration.)
Linear Labs says the HET does the job of the DC/DC boost converter on its own by changing the relative position of one or more of its four rotors, analogous to the variable cam system on an ICE, altering position depending on load needs. Combining the extra torque, reduced weight and complexity possible without a gearbox or boost converter, and lighter ancillaries, Linear Labs claims the HET could increase range by 10%.
A carmaker says …
No automaker will address claims by a company it has never heard of about a component it has never used. Still, we wanted to get OEM commentary to compare to Linear Labs’ statements. We contacted Chevrolet, Tesla, and Hyundai. Only Hyundai agreed to a Q&A, connecting us with Jerome Gregeois, a senior manager at a Hyundai Group powertrain facility, and Ryan Miller, the manager for Hyundai’s electrified powertrain development team.
Gregeois said OEMs invest so much in batteries because they’re “so much more expensive than any of the [other] components,” and there’s so much more efficiency to be extracted from battery chemistry. Therefore, “The only way to reach competitive pricing compared to internal combustion engines or hybrids is really to get battery costs lower and lower.”
Concerning motors, Miller said, “Our focus and the industry’s focus on motors has been transitioning to silicon-carbide-based motor inverters.” The motor inverter converts the battery pack’s direct current (DC) into the alternating current (AC) used to power the electric motors that provide drive to the vehicle. Under regenerative braking, the motor inverter does the opposite – turning AC from the motors back into DC to recharge the battery. Silicon carbide technology, which the IEEE called “Smaller, faster, tougher,” is seen as enabling something like a 50% reduction in inverter volume.
View photos Illustration courtesy Hyundai
Miller told us the permanent magnet motor in the Hyundai Ioniq is about 50 kilograms, or 110 pounds. The gearbox, which contains a final drive and a differential, is about 70 pounds. “It’s not light,” he said, “because gears are generally steel.” As for volume, the gearbox occupies about 70% of the volume of the motor.
We asked Gregeois and Miller if a direct-drive motor that allowed elimination of the gearbox would make an enormous difference in cost or complexity of the powertrain. Said Gregeois, “We think cost-wise that gearbox is going to be cheaper than two motors.” Miller added, “Steel and aluminum is very cheap.”
One automaker example doesn’t negate the benefits of the Hunstable Electric Turbine, and Brad Hunstable believes the savings are there. “Every drivetrain can be designed and engineered multiple ways,” he said. “But if you have two motors that produce twice the torque in half the size as one conventional motor that must utilize a gearbox, then there is no comparison. HET wins. Of course, for the short-term mass-market vehicle, one motor driving directly into the differential is the most likely scenario, still eliminating the standard … gearbox.”
And automakers are throwing money at improving their motors. Honda improved the electric motor in the Accord Hybrid by using square copper wires for the stator windings, and three magnets instead of two on the rotor. The changes are said to have added 6 pound-feet of torque and 14 horsepower.
View photos Illustration by Linear Labs
The First Inning
We asked Brad how long he thought it would be before we’d see an HET in a car like the Chevrolet Bolt. “Three or four, some say five years out … There are longer lead cycles to get into production for big companies, [but] we are in joint development agreements, we are testing with [automakers].”
There have been so many charlatans in the EV space that many of the stories we’ve read about the HET end in commenters attacking it like hyenas disemboweling a wildebeest.
“There’s a lot of smoke and mirrors in the motor space,” Brad acknowledged. “The difference in this one: We’ve built them. At the end of the day you can’t argue with something that’s built right in front of you.”
“We’re literally in the first inning of this technology,” he continued, “so there’s more things that we’ll continue to do that that’ll make this even better. But the first motors that we’re producing in the market are literally a quantum leap on everything that’s out there.”
The question, then, is whether that quantum leap makes sense from a cost and packaging perspective for the spectrum of EV manufacturers, or does it make sense primarily for luxury EV makers who can justify the HET’s cost. Can this one more efficient-yet-expensive component be countered and justified by removing a not-especially expensive thing (the gearbox) and removing some of these pretty expensive and heavy things (batteries)? Hyundai’s representatives weren’t so sure, but if this really is just the first inning for HET, perhaps more development and actual access by major manufacturers will provide the answer as the game goes on.
China is well advanced in switching to the NCM 811 type of lithium-ion cathode for EV batteries.
The new NCM 811 lithium-ion battery chemistry takes the Chinesepassenger xEV (BEV, PHEV, HEV) market like a storm.
According to Adamas Intelligence, In September, NCM 811 was responsible for18%of passenger xEV battery deployment (by capacity).
The NCM 811 is a low cobalt-content cathode (nickel:cobalt:manganese at a ratio of 8:1:1).
The expansion is tremendous compared to 1% in January, 4% in June and 13% in August.
NCM 811 cells combines high-energy density with affordability (lower content of expensive cobalt), which probably is enough for most manufacturers to make the switch from NCM 523 and LFP (often bypassing NCM 622).
“In China, for the second month in a row, NCM 811 was second-only to NCM 523 by capacity deployed, while the once-popular NCM 622 now finds itself in fifth spot with a mere 5% of the market.
In the pursuit of lower costs and higher energy density, a growing number of automakers in China have seemingly opted to bypass NCM 622, shifting instead straight from LFP or NCM 523 cathode chemistries into high-nickel NCM 811.
Since January 2019, the market share of NCM 811 in China’s passenger EV market has rapidly increased from less than 1% to 18% and shows little signs of slowing its ingress. Outside of China, however, automakers have been slow to adopt NCM 811 to-date but we expect to see the chemistry make inroads in Europe and North America by as early as next year.”
NCM 811 share globally is also growing and in September it was at 7%.
The other leading low cobalt chemistry is Tesla/Panasonic’sNCA.
How to build a better Battery through Nanotechnology
PALO ALTO, CALIFORNIA (Note to Readers: This original article was published in 2016 May. Recent updates, News Releases and a YouTube Video have been provided)
On a drizzly, gray morning in April, Yi Cui weaves his scarlet red Tesla in and out of Silicon Valley traffic. Cui, a materials scientist at Stanford University here, is headed to visit Amprius, a battery company he founded 8 years ago. Amprius Latest News Release(December 2018)
It’s no coincidence that he is driving a battery-powered car, and that he has leased rather than bought it. In a few years, he says, he plans to upgrade to a new model, with a crucial improvement: “Hopefully our batteries will be in it.”
Cui and Amprius are trying to take lithium–ion batteries—today’s best commercial technology—to the next level. They have plenty of company. Massive corporations such as Panasonic, Samsung, LG Chem, Apple, and Tesla are vying to make batteries smaller, lighter, and more powerful. But among these power players, Cui remains a pioneering force.
Unlike others who focus on tweaking the chemical composition of a battery’s electrodes or its charge-conducting electrolyte, Cui is marrying battery chemistry with nanotechnology. He is building intricately structured battery electrodes that can soak up and release charge-carrying ions in greater quantities, and faster, than standard electrodes can, without producing troublesome side reactions. “He’s taking the innovation of nanotechnology and using it to control chemistry,” says Wei Luo, a materials scientist and battery expert at the University of Maryland, College Park.
“I wanted to change the world, and also get rich, but mainly change the world.”
In a series of lab demonstrations, Cui has shown how his architectural approach to electrodes can domesticate a host of battery chemistries that have long tantalized researchers but remained problematic. Among them: lithium-ion batteries with electrodes of silicon instead of the standard graphite, batteries with an electrode made of bare lithium metal, and batteries relying on lithium-sulfur chemistry, which are potentially more powerful than any lithium-ion battery. The nanoscale architectures he is exploring include silicon nanowires that expand and contract as they absorb and shed lithium ions, and tiny egg like structures with carbon shells protecting lithium-rich silicon yolks.
(Article continues below Video)
Watch a YouTube Video on the latest Update from Professor Cui (November 2018). A very concise and informative Summary of the State of NextGen Batteries.
** Amprius already supplies phone batteries with silicon electrodes that store 10% more energy than the best conventional lithium-ion batteries on the market.
(Article continues below)
Another prototype beats standard batteries by 40%, and even better ones are in the works. So far, the company does not make batteries for electric vehicles (EVs), but if the technologies Cui is exploring live up to their promise, the company could one day supply car batteries able to store up to 10 times more energy than today’s top performers. That could give modest-priced EVs the same range as gas-powered models—a revolutionary advance that could help nations power their vehicle fleets with electricity provided by solar and wind power, dramatically reducing carbon emissions.
Cui says that when he started in research, “I wanted to change the world, and also get rich, but mainly change the world.” His quest goes beyond batteries. His lab is exploring nanotech innovations that are spawning startup companies aiming to provide cheaper, more effective air and water purification systems. But so far Cui has made his clearest mark on batteries. Luo calls his approach “untraditional and surprising.” Jun Liu, a materials scientist at the Pacific Northwest National Laboratory in Richland, Washington, put it more directly: Cui’s nanotech contributions to battery technology are “tremendous.”
Making leaps in battery technology is surprisingly hard to do. Even as Silicon Valley’s primary innovation, the computer chip, has made exponential performance gains for decades, batteries have lagged. Today’s best lithium-ion cells hold about 700 watt-hours per liter. That’s about five times the energy density of nickel-cadmium batteries from the mid-1980s—not bad, but not breathtaking. In the past decade, the energy density of the best commercial batteries has doubled.
Battery users want more. The market for lithium-ion batteries alone is expected to top $30 billion a year by 2020, according to a pair of recent reports by market research firms Transparency Market Research and Taiyou Research. The rise in production of EVs by car companies that include Tesla, General Motors, and Nissan accounts for some of that surge.
But today’s EVs leave much to be desired. For a Tesla Model S, depending on the exact model, the 70- to 90-kilowatt-hour batteries alone weigh 600 kilograms and account for about $30,000 of the car’s price, which can exceed $100,000. Yet they can take the car only about 400 kilometers on a single charge, substantially less than the range of many conventional cars. Nissan’s Leaf is far cheaper, with a sticker price of about $29,000. But with a smaller battery pack, its range is only about one-third that of the Tesla.
Improving batteries could make a major impact. Doubling a battery’s energy density would enable car companies to keep the driving range the same while halving the size and cost of the battery—or keep the battery size constant and double the car’s range. “The age of electric vehicles is coming,” Cui says. But in order for EVs to take over, “we have to do better.”
He recognized the need early in his career. After finishing his undergraduate degree in his native China in 1998, Cui moved first to Harvard University and then to the University of California (UC), Berkeley, to complete a Ph.D. and postdoc in labs that were pioneering the synthesis of nanosized materials. Those were the early days of nanotechnology, when researchers were struggling to get a firm handle on how to create just the materials they wanted, and the world of applications was only beginning to take shape.
While at UC Berkeley, Cui spent time with colleagues next door at the Lawrence Berkeley National Laboratory (LBNL). At the time, LBNL’s director was Steven Chu, who pushed the lab to invent renewable energy technologies that had the potential to combat climate change, among them better batteries for storing clean energy. (Chu later went on to serve as President Barack Obama’s secretary of energy from 2009 to 2013.)
“At the beginning, I wasn’t thinking about energy. I had never worked on batteries,” Cui says. But Chu and others impressed on him that nanotechnology could give batteries an edge.
As Chu says now, it offers “a new knob to turn, and an important one,” enabling researchers to control not only the chemical composition of materials on the smallest scales, but also the arrangement of atoms within them—and thus how chemical reactions involving them proceed.
After moving to Stanford, Cui quickly gravitated to the nexus between nanotechnology and the electrochemistry that makes batteries work—and accounts for their limitations. Take lithium-ion rechargeable batteries. In principle, these batteries are simple: They consist of two electrodes divided by a membrane “separator” and a liquid electrolyte that allows ions to glide back and forth between the electrodes.
When a battery is charging, lithium ions are released from the positive electrode, or cathode, which consists of a lithium alloy, commonly lithium cobalt oxide or lithium iron phosphate. They are drawn toward the negatively charged electrode, called the anode, which is usually made of graphite. There they snuggle in between the graphite’s sheets of carbon atoms. Voltage from an external power source drives the whole ionic mass migration, storing power.
When a device—say, a power tool or a car—is turned on and demands energy, the battery discharges: Lithium atoms in the graphite give up electrons, which travel through the external circuit to the cathode. Meanwhile, the lithium ions slip out of the graphite and zip through the electrolyte and the separator to the cathode, where they meet up with electrons that have made the journey through the circuit (see diagram below).
Nano to the rescue
Cui and colleagues have applied several nanotechnology-inspired solutions to keep silicon anodes from breaking down and to prevent battery-killing side reactions.
Graphite is today’s go-to anode material because it is highly conductive and thus readily passes collected electrons to the metal wires in a circuit. But graphite is only so-so at gathering lithium ions during charging. It takes six carbon atoms in graphite to hold on to a single lithium ion. That weak grip limits how much lithium the electrode can hold and thus how much power the battery can store.
Silicon has the potential to do far better. Each silicon atom can bind to four lithium ions. In principle, that means a silicon-based anode can store 10 times as much energy as one made from graphite. Electrochemists have struggled in vain for decades to tap that enormous capacity.
It’s easy enough to make anodes from chunks of silicon; the problem is that the anodes don’t last. As the battery is charged and lithium ions rush in to bind to silicon atoms, the anode material swells as much as 300%. Then, when the lithium ions rush out during the battery’s discharge cycle, the anode rapidly shrinks again. After only a few cycles of such torture, silicon electrodes fracture and eventually split into tiny, isolated grains. The anode—and the battery—crumbles and dies.
Cui thought he could solve the problem. His experience at Harvard and UC Berkeley had taught him that nanomaterials often behave differently from materials in bulk. For starters, they have a much higher percentage of their atoms at their surface relative to the number in their interior. And because surface atoms have fewer atomic neighbors locking them in place, they can move more easily in response to stresses and strains. Other types of atomic movement explain why thin sheets of aluminum foil or paper can bend without breaking more easily than chunks of aluminum metal or wood can.
In 2008, Cui thought that fashioning a silicon anode from nanosized silicon wires might alleviate the stress and strain that pulverize bulk silicon anodes. The strategy worked. In a paper in Nature Nanotechnology, Cui and colleagues showed that when lithium ions moved into and out of the silicon nanowires, the nanowires suffered little damage. Even after 10 repeated cycles of charging and discharging, the anode retained 75% of its theoretical energy storage capacity.
Unfortunately, silicon nanowires are much more difficult and expensive to fashion than bulk silicon. Cui and colleagues started devising ways to make cheaper silicon anodes. First, they found a way to craft lithium-ion battery anodes from spherical silicon nanoparticles. Though potentially cheaper, these faced a second problem: The shrinking and swelling of the nanoparticles as the lithium atoms moved in and out opened cracks in the glue that bound the nanoparticles together. The liquid electrolyte seeped between the particles, driving a chemical reaction that coated them in a non-conductive layer, known as a solid-electrolyte interphase (SEI), which eventually grew thick enough to disrupt the anode’s charge-collecting abilities. “It’s like scar tissue,” says Yuzhang Li, a graduate student in Cui’s lab.
A few years later, Cui and his colleagues hit on another nanotech solution. They created egg like nanoparticles, surrounding each of their tiny silicon nanoparticles—the yolk—with a highly conductive carbon shell through which lithium ions could readily pass. The shell gave silicon atoms in the yolk ample room to swell and shrink, while protecting them from the electrolyte—and the reactions that form an SEI layer. In a 2012 paper in Nano Letters, Cui’s team reported that after 1000 cycles of charging and discharging, their yolk-shell anode retained 74% of its capacity.
They did even better 2 years later. They assembled bunches of their yolk-shell nanoparticles into micrometer-scale collections resembling miniature pomegranates. Bunching the silicon spheres boosted the anode’s lithium storage capacity and reduced unwanted side reactions with the electrolyte. In a February 2014 issue of Nature Nanotechnology, the group reported that batteries based on the new material retained 97% of their original capacity after 1000 charge and discharge cycles.
Earlier this year, Cui and colleagues reported a solution that outdoes even their complex pomegranate assemblies. They simply hammered large silicon particles down to the micrometer scale and then wrapped them in thin carbon sheets made from graphene. The hammered particles wound up larger than the silicon spheres in the pomegranates—so big that they fractured after a few charging cycles. But the graphene wrapping prevented the electrolyte compounds from reaching the silicon. It was also flexible enough to maintain contact with the fractured particles and thus carry their charges to the metal wires. What’s more, the team reported in Nature Energy, the larger silicon particles packed more mass—and thus more power—into a given volume, and they were far cheaper and easier to make than the pomegranates. “He has really taken this work in the right direction,” Jun Liu says.
Powered by such ideas, Amprius has raised more than $100 million to commercialize lithium-ion batteries with silicon anodes. The company is already manufacturing cellphone batteries in China and has sold more than 1 million of them, says Song Han, the company’s chief technology officer. The batteries, based on simple silicon nanoparticles that are cheap to make, are only 10% better than today’s lithium-ion cells. But at Amprius’s headquarters, Han showed off nanowire-silicon prototypes that are 40% better. And those, he says, still represent only the beginning of how good silicon anodes will eventually become.
Now, Cui is looking beyond silicon. One focus is to make anodes out of pure lithium metal, which has long been viewed as the ultimate anode material, as it has the potential to store even more energy than silicon and is much lighter.
But there have been major problems here, too. For starters, an SEI layer normally forms around the lithium metal electrode. That’s actually good news in this case: Lithium ions can penetrate the layer, so the SEI acts as a protective film around the lithium anode. But as the battery cycles, the metal swells and shrinks just as silicon particles do, and the pulsing can break the SEI layer. Lithium ions can then pile up in the crack, causing a metal spike, known as a dendrite, to sprout from the electrode. “Those dendrites can pierce the battery separator and short-circuit the battery and cause it to catch fire,” says Yayuan Liu, another graduate student in Cui’s group.
Conventional approaches haven’t solved the problem. But nanotechnology might. In one approach to preventing dendrite formation, Cui’s team stabilizes the SEI layer by coating the anode with a layer of interconnected nanocarbon spheres. In another, they’ve created a new type of yolk-shell particle, made of gold nanoparticles inside much larger carbon shells. When the nanocapsules are fashioned into an anode, the gold attracts lithium ions; the shells give the lithium room to shrink and swell without cracking the SEI layer, so dendrites don’t form.
Improving anodes is only half the battle in making better batteries. Cui’s team has taken a similar nano inspired approach to improving cathode materials as well, in particular sulfur. Like silicon on the anode side, sulfur has long been seen as a tantalizing option for the cathode. Each sulfur atom can hold a pair of lithiums, making it possible in principle to boost energy storage several fold over conventional cathodes. Perhaps equally important, sulfur is dirt cheap. But it, too, has problems. Sulfur is a relatively modest electrical conductor, and it reacts with common electrolytes to form chemicals that can kill the batteries after a few cycles of charging and discharging. Sulfur cathodes also tend to hoard charges instead of giving them up during discharge.
Seeking a nanosolution, Cui’s team encased sulfur particles inside highly conductive titanium dioxide shells, boosting battery capacity fivefold over conventional designs and preventing sulfur byproducts from poisoning the cell. The researchers have also made sulfur-based versions of their pomegranates, and they have trapped sulfur inside long, thin nanofibers. These and other innovations have not only boosted battery capacity, but also raised a measure known as the coulombic efficiency—how well the battery releases its charges—from 86% to 99%. “Now, we have high capacity on both sides of the electrode,” Cui says.
Down the road, Cui says, he intends to put both of his key innovations together. By coupling silicon anodes with sulfur cathodes, he hopes to make cheap, high-capacity batteries that could change the way the world powers its devices. “We think if we can make it work, it will make a big impact,” Cui says.
It just might help him change the world, and get rich on the side.
Bio – Professor Yi Cui
Professor of Materials Science and Engineering, of Photon Science, Senior Fellow at the Precourt Institute for Energy and Prof, by courtesy, of Chemistry PhD, Harvard University (2002)
Cui studies nanoscale phenomena and their applications broadly defined. Research Interests: Nanocrystal and nanowire synthesis and self-assembly, electron transfer and transport in nanomaterials and at the nano interface, nanoscale electronic and photonic devices, batteries, solar cells, microbial fuel cells, water filters and chemical and biological sensors.
Rolls Royce leads a group of UK Government funded projects under the name ACCEL, which is an abbreviation of “Accelerating the Electrification of Flight” somehow. With the group’s newest flight project,the Spirit of Innovation, they aim to exceed 300 miles per hour, and sustain speed for at least forty minutes, enough to cross over from London to Paris. It’s an ambitious project, and one that Rolls hopes will kick off a “third wave of aviation.”
Rolls Royce was at the absolute forefront of airplane propeller driven technology in 1931 with the Supermarine S.6B, which won the Schneider Trophy for top speed that year with a max speed of 343 miles per hour. That plane kicked off a series of innovations for Rolls Royce and gave the company the notoriety it needed to become the leader in British flight.
The current electric plane record is held by Siemens, which put up a plane to 210 miles per hour in 2017. ACCEL team manager Matheu Parr wants to blow that speed out of the water, and is using the Supermarine’s speed record as the benchmark for the new Spirit of Innovation.
“We’re monitoring more than 20,000 data points per second, measuring battery voltage, temperature, and overall health of the powertrain, which is responsible for powering the propellers and generating thrust. We’ve already drawn a series of insights from the unique design and integration challenges,” says Parr. “And we’re gaining the know-how to not only pioneer the field of electric-powered, zero-emissions aviation – but to lead it. At this point, our confidence is sky high.”
This all-electric plane is set to fly sometime in 2020, and the specifications look absolutely wild. For maximum frontal area efficiency, the battery pack has to be small and compact, merging 6000 lithium cells with an advanced cooling system to help keep the batteries stable. With three stacked YASA 750R electric motors, the plane will have around 500 horsepower available to spin the modern design propeller.
Watch a YouTube Video: The Top 10 Electric Planes that are Already Here and … Flying on Batteries!
Humanity has dreamt about reaching the skies throughout its existence, and even though today we can easily take a plane and travel across the world, airflight still remains rather expensive and harmful to our environment. But what if we told you that all electric aircraft are already here and they will drastically change the way we experience air travel and cut down the costs in half. Enjoy this list of these emission free planes that are pioneering their way into the future.
In order to make this project a reality, the highest tier aerodynamics engineers from all over the UK were hired, primarily from within Rolls Royce’s aerospace engineering division, as well as some from within the motorsport community. This is truly an all-in mission for the British industrial complex.
Lithium-sulfur batteries could be the energy storage devices of the future, if they can get past a chemical phenomenon that reduces their endurance. Drexel researchers have reported a method for making a sulfur cathode that could preserve the batteries’ exceptional performance. (Image from Drexel News)
Drexel’s College of Engineering reports that researchers and the industry are looking at Li-S batteries to eventually replace Li-ion batteries because a new chemistry that theoretically allows more energy to be packed into a single battery.
This improved capacity, on the order of 5-10 times that of Li-ion batteries, equates to a longer run time for batteries between charges.
However, the problem is that Li-S batteries have trouble maintaining their superiority beyond just a few recharge cycles. But a solution to that problem may have been found with new research.
The new approach, reported by in a recent edition of the American Chemical Society journal Applied Materials and Interfaces, shows that it can hold polysulfides in place, maintaining the battery’s impressive stamina, while reducing the overall weight and the time required to produce them.
“We have created freestanding porous titanium monoxide nanofiber mat as a cathode host material in lithium-sulfur batteries,” said Vibha Kalra, PhD, an associate professor in the College of Engineering who led the research.
“This is a significant development because we have found that our titanium monoxide-sulfur cathode is both highly conductive and able to bind polysulfides via strong chemical interactions, which means it can augment the battery’s specific capacity while preserving its impressive performance through hundreds of cycles.
We can also demonstrate the complete elimination of binders and current collector on the cathode side that account for 30-50 percent of the electrode weight — and our method takes just seconds to create the sulfur cathode, when the current standard can take nearly half a day.”
Please find the full report here: LINK
TiO Phase Stabilized into Free-Standing Nanofibers as Strong Polysulfide Immobilizer in Li-S Batteries: Evidence for Lewis Acid-Base Interactions
Arvinder Singh and Vibha Kalra
ACS Appl. Mater. Interfaces, Just Accepted Manuscript
We report the stabilization of titanium monoxide (TiO) nanoparticles in nanofibers through electrospinning and carbothermal processes and their unique bi-functionality – high conductivity and ability to bind polysulfides – in Li-S batteries. The developed 3-D TiO/CNF architecture with the inherent inter-fiber macropores of nanofiber mats provides a much higher surface area (~427 m2 g-1) and overcomes the challenges associated with the use of highly dense powdered Ti-based suboxides/monoxide materials, thereby allowing for high active sulfur loading among other benefits.
The developed TiO/CNF-S cathodes exhibit high initial discharge capacities of ~1080 mAh g-1, ~975 mAh g-1, and ~791 mAh g-1 at 0.1C, 0.2C, and 0.5C rates, respectively with long term cycling. Furthermore, free-standing TiO/CNF-S cathodes developed with rapid sulfur melt infiltration (~5 sec) eradicate the need of inactive elements viz. binders, additional current collectors (Al-foil) and additives. Using postmortem XPS and Raman analysis, this study is the first to reveal the presence of strong Lewis acid-base interaction between TiO (3d2) and Sx2- through coordinate covalent Ti-S bond formation.
Our results highlight the importance of developing Ti-suboxides/monoxide based nanofibrous conducting polar host materials for next-generation Li-S batteries.
“Reprinted with permission from (DOI: 10.1021/acsami.8b11029). Copyright (2018) American Chemical Society.”
One of the conveniences that makes fossil fuels hard to phase out is the relative ease of storing them, something that many of the talks at Advanced Energy Materials 2018 aimed to tackle as they laid out some of the advances in alternatives for energy storage.
“Energy is the biggest business in the world,”Max Lu, president and vice-chancellor of the University of Surrey, told attendees of Advanced Energy Materials 2018 at Surrey University earlier this month. But as
Lu, who has held numerous positions on senior academic boards and government councils, pointed out, the shear scale of the business means it takes time for one technology to replace another.
“Even if solar power were now cheaper than fossil fuel, it would be another 30 years before it replaced fossil fuel,” said Lu. And for any alternative technology to replace fossil fuels, some means of storing it is crucial.
Batteries beyond lithium ion cells
Lithium ion batteries have become ubiquitous for powering small portable devices.
But as Daniel ShuPing Lau, professor and head at Hong Kong Polytechnic University, and director of the University Research Facility in Materials pointed out, lithium is rare and high-cost, prompting the search for alternatives.
He described work on sodium ion batteries, where one of the key challenges has been the MnO2 electrode commonly used, which is prone to acid attack and disproportionation redox reactions.
Lau described work by his group and colleagues to get around the electrode stability issues using environmentally friendly K-birnessite MnO2 (K0.3MnO2) nanosheets, which they can inkjet print on paper as well as steel.
Their sodium ion batteries challenge the state of the art for energy storage devices with a working voltage of 2.5 V, maximum energy and power densities of 587 W h kgcathode−1 and 75 kW kgcathode−1, respectively, and a 99.5% capacity retention for 500 cycles at 1 A g−1.
Metal air batteries are another alternative to lithium-ion batteries, and Tan Wai Kan from Toyohashi University of Technology in Japan described the potential of using a carbon paper decorated with Fe2O3 nanoparticles in a metal air battery.
They increase the surface area of the electrode with a mesh structure to improve the efficiency, while using solid electrolyte KOHZrO2 instead of a liquid helped mitigate against the stability risks of hydrogen evolution for greater reliability and efficiency.
A winning write off for pseudosupercapacitors
Other challenges aside, when it comes to stability, supercapacitors leave most batteries far behind.
Because there is no mass movement, just charge, they tend to stay stable for not just hundreds but hundreds of thousands of cycles
They are already in use in the Shanghai bus system and the emergency doors on some aircraft as Robert Slade emeritus professor of inorganic and materials chemistry at the University of Surrey pointed out.
He described work on “pseudocapacitance”, a term popularised in the 1980s and 1990s to to describe a charge storage process that is by nature faradaic – that is, charge transport through redox processes – but where aspects of the behaviour is capacitive.
MnO2 is well known to impart pseudocapacitance in alkaline solutions but Slade and his colleagues focused on MoO3.
Although MnO3 is a lousy conductor, it accepts protons in acids to form HMoO, and exploiting the additional surface area of nanostructures further helps give access to the pseudocapacitance, so that the team were able to demonstrate a charge-discharge rate of 20 A g-1 for over 10,000 cycles.
This is competitive with MnO2 alkaline systems. “So don’t write off materials that other people have written off, such as MoO3, because a bit of “chemical trickery” can make them useful,” he concluded.
Down but not out for solid oxide fuel cells
But do we gain from the proliferation of so many different alternatives to fossil fuels? According to John Zhu, professor in the School of Chemical Engineering at the University of Queensland in Australia, “yes.”
“For clean energy we need more than one solution,” was his response when queried on the point after his talk.
In particular he had a number of virtues to espouse with respect to solid oxide fuel cells (SOFCs), which had been the topic of his own presentation.
Besides the advantage of potential 24-7 operation, SOFCs generate the energy they store. As Zhu pointed out, “With a battery energy the source may still be dirty – so you are just moving the pollution from a high population density area to a low one.”
In contrast, an SOFC plant generates electricity directly from oxidizing a fuel, while at the same time it halves the CO2 emission of a coal-based counterpart, and achieves an efficiency of more than 60%.
If combined with hot water generation more than 80% efficiency is possible, which is double the efficiency of a conventional coal plant. All this is achieved with cheap materials as no noble metals are needed.
Too good to be true? It seemed so at one point as promising corporate ventures plummeted, one example being Ceramic Fuel Cells Ltd, which was formed in 1992 by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and a consortium of energy and industrial companies.
After becoming ASX listed in 2004, and opening production facilities in Australia and Germany, it eventually filed voluntary bankruptcy in 2015.
So “Are SOFCs going to die?” asked Zhu.
So long as funding is the lifeline of research apparently not, with the field continuing to attract investment from the US Department of Energy – including $6million for Fuel Cell Energy Inc. Share prices for GE Global Research and Bloom Energy have also doubled in the two months since July 2018, but Zhu highlights challenges that remain.
At €25,000 to install a 2 kW system he suggests that cost is not the issue so much as durability. While an SOFC plant’s lifetime should exceed 10 years, most don’t largely due to the high operating temperatures of 800–1000 °C, which lead to thermal degradation and seal failure. Lower operating temperatures would also allow faster start up and the use of cheaper materials.
The limiting factor for reducing temperatures is the cathode material, as its resistance is too high in cooler conditions. Possible alternative cathode materials do exist and include – 3D heterostructured electrodes La3MiO4 decorated Ba0.5Sr0.3Ce0.8Fe0.3O3 (BSCF with LN shell).
Photocatalysts all wrapped up
Other routes for energy on demand have looked at water splitting and CO2 reduction.
As Lu pointed out in his opening remarks, the success of these approaches hinge on engineering better catalysts, and here Somnath Roy from the Indian Institute of Technology Madras, in India, had some progress to report.
“TiO2 is to catalysis what silicon is to microelectronics,” he told attendees of his talk during the graphene energy materials session. However the photocatalytic activity of TiO2 peaks in the UV, and there have been many efforts to shift this closer to the visible as a result.
Building on previous work with composites of graphene and TiO2 he and his colleagues developed a process to produce well separated (to allow reaction space) TiO2 nanotubes wrapped in graphene.
Although they did not notice a wavelength shift in the peak catalytic activity to the visible due to the graphene, the catalysis did improve due to the effect on hole and electron transport.
There was no shortage of ideas at AEM 2018, but as Lu told attendees,
“Ultimately uptake does not depend on the best technology but the best return on investment.”
Speaking to Physics World he added,
“The route to market for any energy materials will require systematic assessment of the technical advantages, market demand and a number of iterations of property-performance-system optimization, and open innovation and collaboration will be the name of the game for successful translation of materials to product or processes.”
Whatever technologies do eventually stick, time is of the essence. Most estimates place the tipping point for catastrophic global warming at 2050.
Allowing 30 years for the infrastructure overhaul that could allow alternative energies to totally replace fossil fuels leaves little more than a year for those technologies to pitch “the best return on investment”.
Little wonder advanced energy materials research is teaming.
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