Microbatteries and Artificial Leaves May Be the Solutions for Alternative Fuel Problems
Illustration of a microbattery electron transfer. From illinois.edu
Two recent breakthroughs in energy storage technology could provide solutions for some of the most pressing problems with power generation and delivery. On one side, we have the so-called microbattery. Scientists at the University of Illinois in Urbana-Champaign recently announced they have developed a lithium-ion battery that utilizes a fast-charging system (also developed by the university), and miniaturizes it to create a battery that is, dimensionally, extremely small, in addition to providing a lot of power in a very short amount of time. A chemist from Harvard has also created a silicon-based wafer that, when placed in water and combined with sunlight, can separate water’s hydrogen and oxygen molecules; the hydrogen can be captured and used as fuel. Both innovations may help speed up the inevitable switch from fossil fuel-powered sources of energy if they were ever mass-produced.
At the core of the microbatteries developed by UI lies a breakthrough recharging system that was developed by the same university two years ago. Professor Paul Braun led a team that created a cathode system that can charge and discharge a battery very rapidly without sacrificing its capacity to store energy. Normally, there is a tradeoff between capacity and power in batteries. Normal AA batteries store a decent amount of electrical charge, but cannot discharge it at a high rate (think of an old Game Boy and the 4 AA batteries it required to power the darn thing). Compare this with a capacitor, which releases energy quickly but cannot store much of it. When the quick-charging cathode system is applied to a lithium-ion battery, the cathode is recharged at a much higher rate than in a conventional li-ion battery.
In a nutshell, the movement of electrons from cathode to anode by way of an intermediary electrolyte creates power. When rechargeable batteries are connected to a power source, the electron flow is reversed to send the electrons back to the cathode, and when unplugged, the battery repeats the process. In normal lithium-ion batteries, like the ones used in electric vehicles and laptops, the recharging process is slow, and in the case of EVs, takes several hours even with a high-voltage recharging station.
The novel solution invented by Braun and his team is described by the university’s press release as a “three-dimensional nanostructure for battery cathodes that allows for dramatically faster charging and discharging without sacrificing energy storage capacity” (Source). This effectively means that the recharging system is so quick that a charge or discharge is between 10 and 100 times faster than in a standard li-ion battery. The next team, led by Professor William King, created a matching anode and miniaturized the entire system.
This technology, applied to the world of consumer EVs, would produce obvious benefits. Because of the miniaturization, batteries would no longer need to be giant, heavy blocks that upset the handling, weight, and range of such cars (the batteries in the Mercedes SLS AMG Electric Drive add more than 1,000lbs to the weight of an SLS). They would also be able to recharge much more rapidly; Braun notes that “instead of taking hours to charge the vehicle you could potentially have vehicles that would charge in similar times as needed to refuel a car with gasoline.”
There are issues that need to be addressed before the microbatteries would be available to the public, however. IEEE.org emailed Braun, who described the two most pressing problems with the system. The most glaring is the number of times the battery can be recharged. All lithium-ion batteries experience a certain amount of decay as time goes on; this is why battery packs in cars are guaranteed for a certain number of years before they need to be replaced (often at a substantial cost). While most packs can survive a few thousand times (and true capacitors can reach the millions), with the microbattery system, IEEE notes, ” the authors write that the battery cell retained 64 percent of its initial energy after only 15 cycles, losing about 5 percent with each “low-rate” cycle.” So rapid decay is the most prevalent issue to be sorted, along with the fact that the electrolyte used is combustible. Only a small amount is used in the standard-sized battery, but making a larger battery for full-scale applications could cause safety concerns.
The artificial leaf operates on a different end of the spectrum. Dr. Daniel Nocera, a researcher and chemist, first created what he called an “artificial leaf” while working at MIT in 2011. When submerged in purified water and placed in sunlight, the silicon wafer (covered in a catalyst) broke down the hydrogen and oxygen molecules, which bubble up to the surface as a gas. When properly separated and collected, the hydrogen can be stored for use in a fuel cell. Until recently, the problem was securing purified water, but Nocera and his team, now working at Harvard, have figured out a way to repeat the process with dirty water.
Photo from “The Artificial Leaf“
When exposed to impurities in the water, the artificial leaf’s original coating would eventually be covered in bacteria, which halted production of the gases. That setback has been overcome by tweaking the catalyst’s coating. Now, the catalyst can break apart, denying the bacteria a smooth surface to attach to, and reassemble itself. This means that the artificial leaf can be used with unpurified water, a necessary component to the eventual usage of the artificial leaf, as it is expected to be used in parts of the world where access to an electrical grid is not possible, like in Africa.
In its current state, the leaf can provide 100 watts for 24 hours by being submerged in only one liter of water. Obviously, this is not nearly enough to power a house in more developed countries, but it is extraordinarily beneficial in parts of the world that don’t demand a large amount of electricity. It is unclear whether the artificial leaf can perform its functions using seawater, but I doubt it. Other than the costs of the artificial leaf (which shouldn’t be too expensive, the materials used are supposedly common), the saltwater issue would likely be the last significant hurdle for a truly widespread, full-scale application. The idea of using water to generate electricity to use in an EV in certainly attractive; it’s not precisely the water-powered car of the future that we have dreamed of for decades, but it very nearly is.
Both the microbatteries and the artificial leaf have an extraordinary potential should they make it to the production stage. It is true that each has a specific set of challenges that must be overcome, not the least of which is consumer cost, but if brought to market they could truly revolutionize the way we live and drive. A Tesla Model S quicker than a BMW M5 that can be filled up in just a couple of minutes with electricity derived from water? If that’s not the future, I don’t know what is.