A new battery system may someday allow drivers to recharge their cars as quickly and easily as filling up a gas tank.
The membrane-less flow battery, created by Purdue University researcher John Cushman, features inexpensive components: water, ethanol, salt, and a metal such as aluminum or zinc. If the "Ifbattery" catches on, fueling stations could potentially power vehicles by dispensing a water and ethanol solution as fluid electrolytes.
John Cushman, a distinguished professor of earth, atmospheric and planetary science, co-founded Ifbattery LLC (IF-battery) to further develop and commercialize the technology.
Tech Briefs: How does the charging process improve upon current ways to charge a vehicle?
John Cushman: There are two types of [electric] vehicles. One is the fuel cell vehicle, and the other is a lithium-ion-battery-powered vehicle, like the Tesla. Our [system] is very similar to a fuel cell vehicle’s in that instead of using, let’s say, hydrogen and oxygen as your sources for energy, you’re using electrolytes. You pump electrolytes into the battery and recharge the old electrolytes.
With flow batteries like fuel cells, you don’t have to sit around and charge the thing up. You just fill it with electrolytes and drive off. That’s the model we’re shooting for. We’ve created a flow battery that rivals in energy density that of the lithium-ion battery.
Tech Briefs: What is a flow battery?
Cushman: Flow batteries are a very simple concept. On the anode side, you’re oxidizing some compound; on the cathode side, you’re reducing it. That creates a charge imbalance, which shifts the electrons through the load. You have to have a redistribution of the ions within the electrolytes. If the electrons are flying down toward the cathode, then you need to also, within the electrolyte, have positive ions moving down to balance that charge. The electrolyte allows you to maintain that charge neutrality. If you don’t have an electrolyte, then the battery won’t work. Our electrolytes are very simple: basically, a salt and a polar fluid.
Tech Briefs: What are the advantages of flow batteries?
Cushman: Flow batteries are not a new idea. They’ve been around for 40 years at least. The problem with older concepts of flow batteries is they have a very low energy density, which means you have to carry a very large mass of fluid on your car, and that just makes it impractical. We’ve created a battery that has enough energy per kilogram that it can be carried in a small vehicle. The one we’re playing with right now has a concept called super-capacitance, which allows you to significantly increase the current in the battery at very low cost.
Tech Briefs: What is super-capacitance?
Cushman: Super-capacitance is the “Holy Grail” for batteries. It is a combination of double-layer capacitance [the storing of electrical energy at the interface between a conductive electrode and an adjacent liquid electrolyte] and redox capacitance [an energy storage process in which one substance or molecule is reduced and another oxidized]. Super-capacitance imparts significant current density and power to a cell, which translates to high energy density and hence often allows for small and lighter batteries — which can help minimize cost.
Tech Briefs: What makes the Ifbattery system a cost-effective one?
Cushman: There are several different chemistries, and they all involve very inexpensive components: components that are biodegradable, recyclable, and contain no environmental contaminants at all; they’re not hazardous. The cost for most of the components can be measured in pennies per gallon.
Tech Briefs: How do you envision this recharging system being used in the future? What needs to happen for this concept to be a mainstream idea?
Cushman: It’s a tough, uphill battle because the lithium-ion battery is so well established right now. With the lithium model, you need to completely redo the entire energy infrastructure of the United States in order to have 10 million cars being charged up at the same time. To me, that is not a practical solution for the needs that we have.
The beauty of what we’re doing is it doesn’t require remaking the entire energy infrastructure of the country. Gas stations can deliver electrolytes instead of gasoline. The piping systems can pipe electrolytes instead of gasoline. Trucks and trains can all be used to carry this. The electrolytes are not environmentally hazardous.
It’s like any new technology. It needs to be adapted, which is always a very complicated idea because people don’t like to change. Only time will tell. I think we have a model that is good as anything I’ve ever seen out there.
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