The television ads are appearing more frequently and the cars they tout more recognizable. Within a few months public charging stations will start to spring up around central Illinois as electrical vehicles (EVs) enter the American consumer consciousness as a viable choice for motorists. And those EVs don’t exist without batteries, just like laptops, cell phones, and almost every other one of the electronic devices that seem essential to life in the 21st Century.
With the factors of climate change, the energy crisis, and consumer demand as incentives, the government – principally the Department of Energy (DOE) — is pushing for big technology advances in batteries, or the more generic term, electrical energy storage (EES) systems. Beckman Institute researchers are at the forefront of these research efforts when it comes to creating battery systems that are longer lasting, more reliable, more powerful, faster, and safer. That is especially true when it comes to advancing battery technology for electrical vehicles.
Electrical vehicles have been around for awhile, but mostly they have been the transportation choice of those concerned with the environment and the hobbyist. Now there is a push by both manufacturers and government (in the form of tax credits and research grants) to bring them to a mass marketplace.
A new ad campaign for an all-electric car, the Mitsubishi i EV, is touting Bloomington-Normal, Illinois, as a model EV community. The car is already being sold by dealerships in California, and is slated to hit the roads locally this spring. The Chevrolet Volt is an electrical vehicle with a gas generator in reserve for longer distance driving; there are more than 6,000 already in use on American roadways.
Several faculty in Beckman’s Molecular and Electronic Nanostructures research theme have made recent discoveries that have the potential for greatly advancing battery systems, including creating self-healing technology for EES (Scott White, Nancy Sottos and Jeff Moore), and developing ultrahigh energy and power density batteries (Paul Braun, Harley Johnson, and Sottos).
White, Sottos, and Moore are members of Beckman’s Autonomous Materials Systems group who have developed self-healing materials systems based on microcapsule and vascular technology that autonomically responds to damage with healing agents. Now they are applying some of those same techniques toward self-healing for batteries. Their work is part of a new DOE-funded Center for Electrical Energy Storage (CEES) that seeks to create future battery technology for EVs that is both longer-lasting and safer.
But electrical vehicles are already coming off assembly lines, General Motors and Mitsubishi wagering a lot on their success. Fires in lithium-ion batteries — the most common battery technology in use today — have plagued electronic devices, and have occurred in delayed fashion following crash tests of the Volt.
“There is a huge amount of pressure to solve problems right away because these are being rolled out,” White said. “As we’ve just seen with the Volt fire, the more these cars are out there, the more you’re going to see these reports. If electric cars come out and have safety problems and have major loss of life and property, the public is just not going to go that route.
“And we have to in order to solve the energy problem. We can’t fail. We’ve got to pay really serious attention to safety issues and make sure that is never going to be a problem.”
Self-healing Methods for Making Batteries Safer
Last year two Volts caught fire following crash tests — in one case, days and in another, weeks after the test — by the National Highway Traffic Safety Administration; later, the lithium-ion battery that powers the car was determined to be the culprit. According to the Associated Press story on one incident, an “NHTSA investigation concluded the crash test damaged the battery, which later led to the fire. Lithium-ion batteries, which are used in a vast array of consumer electronics, have a history of sometimes catching fire when damaged.”
“That story made the rounds in our group right away,” White said.
White said researchers like those from the AMS group and others at the CEES are trying to make battery technology that is longer lasting and more powerful, but also safer. The technology offered by the Beckman researchers employs an autonomic system that prevents potential fires or explosions through self-healing methods.
“We’ve made a lot of progress in autonomic shutdown mechanisms using microcapsules,” White said. “We’ve been able to reduce the critical concentration to put into the battery to achieve shutdown by about an order of magnitude through surface functionalization of these capsules and various other methods for improving their dispersion.”
White said they are looking at three approaches for delivering self-healing agents to damage sites in batteries. One involves liquid metal capsules that he said would more likely have applications in electronics. Another approach is to deliver a conductive monomer that would undergo polymerization within the battery after it’s delivered to the damage site. A third, and most promising method White said, is to fill capsules with a conductive filler phase that is in suspension, so that when the capsule breaks, it delivers that conductive phase and re-establishes conductivity.
“We’ve been pursuing that pretty heavily over the last few months and it looks like it has good applicability in terms of battery anode materials,” he said.
In addition to micro-capsules, the group is also looking at a microvascular network system which is part of a battery that is integrated into the vehicle. White said that approach could be thought of as a flow battery in which the active materials, including the self-healing agents, are in a fluid phase and part of a vascular battery integrated with the vehicle’s structure.
“We’re starting on trying to meld together all of our expertise in new developments in terms of vascular materials with energy storage,” White said. “It has lots of advantages in terms of application but what we are particularly interested in is trying to integrate energy storage together with structural functionality seamlessly; rather than having a car with a battery bank, it would be the car.”
White said battery electrodes — the anodes and (to a lesser degree) the cathodes — are microporous materials systems that could be seen as a vascular material.
“The liquid electrolytes that are in batteries are pervasive throughout all of these pores,” he said. “So we have thought about delivering compounds that would improve battery longevity through a vascular network that is embedded in these materials systems and that may play out as a good application.
“But when you’re starting from the ground up and you want to develop a vascular materials system, it’s natural for us to think ‘well we’ve already got all of this technology that is structural material that is vascularized. Let’s put them both together and make something that is seamless.’”
The CEES is focused on advancing battery technology generally, but White said the DOE is “pushing (EV batteries) as their focus. But there is lots of talk about grid storage and that sort of thing. The same issues are going to apply there.”
There is also the issue of range, and what is called “range anxiety” faced by consumers who might be considering purchasing an electrical vehicle, but are worried how many miles an EV can take them before needing to be recharged. That is one of the problems being addressed by Braun and his collaborators in a Beckman seed proposal and related efforts focusing on ultrahigh energy and power density batteries.
Braun reported last year in Nature Nanotechnology on the development of a three-dimensional nanostructure for use in battery cathodes that was fast-charging without reducing the energy density or storage capacity. Braun said the system they developed has capacitor-like power because it can release energy quickly but, unlike capacitors and similar to a battery, could store a large amount of energy. The method employs a thin film for the active material (for fast charging and discharging) but turns the film into a 3-D structure that can store energy, resulting in 10 to 100 times faster charge and discharge than normal bulk battery electrodes.
“Most of the time for a fast-charge battery, they make it where you have fast charge or high-powered discharge, but you sacrifice the storage capacity,” Braun said. “Sometimes people will talk about how long it holds the capacity, which would be if you charge it today three months from now would it still be fully charged. We didn’t work on that side of the problem. What we worked on was to have a battery that could deliver charge quickly or accept charge quickly and maintain the high energy density.”
A recent advance in this line of work involves development of a three-dimensional structure for battery anodes.
“In a real battery you need both sides to be fast, you need a fast anode and a fast cathode,” Braun said. “In the first paper we really concentrated on the cathode. Now we have developed a number of systems that give fast charge on the anode and are putting the two of them together to make a real battery.”
The seed proposal work with Johnson, Sottos, and Beckman affiliate Shen Dillon involves comprehensive efforts to understand the science and engineering of high energy and power density batteries. They are looking to exceed government targets for introducing advanced battery technologies to consumers and the military.
Taking these developments from labs to the marketplace and other applications is further away in some respects but much closer in others. The technology developed by Braun and his collaborators — called StructurePore — has already been licensed to a company at the University of Illinois Research Park called Xerion Advanced Battery Corporation for commercial applications. Manufacturing that technology for use in EVs is a few years down the road, but is being envisioned as one of its important potential outcomes.
Braun said the initial applications for the technology will be in niche consumer and military applications.
“Once they are making those batteries and have the manufacturing capability, that’s when you start looking at things like automotive, where you would have to be able to make a million batteries,” Braun said. “There is certainly development but the design we’re using and the processes we’re using are things that are compatible with bulk and volume manufacturing. From the beginning we’ve tried to focus on designs which can be manufactured.”
Braun said Xerion is taking the lead on commercialization.
“They’ve hired a number of people so that is a real and active effort,” he said. “They are starting with our cathode designs but now that we are getting some of these new advanced anode designs too, I think we’ll be able to make batteries that are fast charge, fast discharge, and high power.”
When the paper was published heralding the new technology in Nature Nanotechnology, Braun said that he was optimistic about its use in EVs. He sees it as one way to make electrical vehicles practical for consumers used to filling up with gasoline and driving for hundreds of miles. Charging stations offer much faster EV battery system recharging than home outlets, which can take 24 hours to fully recharge, but still don’t come close to the few minutes drivers spend refilling with gasoline.
Braun said the problem lies not with the recharging station, but with current battery technology, which in vehicles like the Mitsubishi i and Nissan Leaf, is the sole method for propulsion.
“There are a lot of issues with delivering that much power; there are a lot of engineering issues that are going to be a challenge for the electrical filling station,” he said. “But, for the most part, there are known solutions. Right now, for the battery, there is really just not a known solution. So, the structure for our design is one attempt at that. That’s our goal.
“With conventional batteries, people are talking about 15 minutes to 30 minutes, so you could go shopping while your car recharges. But it’s still not practical for driving to, say Chicago. You don’t want to stop halfway, wait 30 minutes while it recharges, and finish your trip. If you want to get people to adopt this as their primary vehicle, they’re going to have to be able to charge it the same way they fill up their car with gas.”
Which means researchers like Braun will have to solve the problem of range anxiety.
“If you could build an electrical vehicle that could be charged as quickly as you can now refill a car with gas, that would greatly diminish what is called people’s range anxiety,” Braun said. “Today’s electric vehicles can go a hundred miles and then you have to wait a half-an-hour, an hour, two hours to charge. That’s difficult to get the consumer to accept. I think electric vehicles will really make an impact when you charge them just as fast as you can fill your car. I think our battery is the first step to doing that.”
The Next Generation of Batteries
Commercialization of self-healing technology is being developed by a company called Autonomic Materials Inc., which was started by members of the AMS group. White said application of the conductivity restoration aspect of their self-healing work is years away from commercial use, but the autonomic shutdown method — which could prevent the types of fires seen with Volts — is much closer to becoming a reality.
“What we developed and showed here is infinitely scalable and doable pretty quickly,” White said. “People can pick it up and run with it.”
If the efforts pay off with these technologies being adopted in future electrical vehicles, whose numbers could swell to millions in the next couple of decades (California has proposed rules to increase the number of EVs on its road to 500,000 by 2025), then the University of Illinois and Beckman will likely be as integral to those advances as they have been in information technologies.
“We started it here and it’s exciting that it came out of Illinois,” Braun said. “The battery effort here is growing a lot, not just my group but others. Broad-based, this is great opportunity for Beckman and the University.”