Zinc-air and aluminum batteries to compete with lithium ion
The race to dominate the electric car market hinges as much on battery technology and improved recharging infrastructure as it does on sticker price, software updates, and styling. Which is why Chinese companies are investing massive sums in matching and surpassing Tesla’s industry-leading battery technology and manufacturing capacity.
Is Tesla on its way to achieve a battery pack cost of $100 per kilowatt-hour?
Nearly all of that capacity is focused on lithium-ion technology, but other approaches are emerging that promise to change the battery technology landscape to extend the range of electric vehicles. Increasing driving range to, say, the equivalent of a tank of gas could provide the inflection point that at last accelerates electric drivetrains past the internal combustion engine.
Aluminum- and zinc-air batteries
As new battery technologies emerge, new wireless schemes are also being demonstrated that could make recharging electric vehicle batteries as fast as filling a gas tank.
With lithium-ion battery technology perhaps approaching its own Moore’s Law ceiling, researchers are branching out to pursue technologies like aluminum- and zinc-air batteries that are just now entering the market. The key to those emerging technologies is boosting recharging capability while demonstrating the ability to lower energy storage cost to the baseline of roughly $100 per kilowatt-hour.
By some estimates, zinc-air batteries could hit the electric car market by as early as 2019 and eventually could be cheaper, lighter, and safer than lithium-ion. Battery startups such as EnZinc and NantEnergy are promoting zinc battery technology as an alternative to lithium-ion as a cheaper, safer alternative with potential energy densities and recharging capabilities approaching lithium-ion.
NantEnergy’s world’s first zinc-air rechargeable cells come with proven global deployment — serving as a sole source of power to 200,000 people. Meanwhile, the company claims that the new rechargeable cells have already broken the $100/kWh manufacturing cost barrier. (Photo: NantEnergy)
Three-dimensional “zinc-based batteries will offer the power and range needed at a lower cost,” asserts EnZinc. “They will be lighter-weight or longer-range, safer, and recyclable.”
Among the drawbacks of metal-air batteries is their susceptibility to corrosion. That means that promising new approaches like aluminum-air batteries can quickly lose their stored charge. Researchers recently reported in the journal Science on a corrosion-inhibiting approach that uses oil as a buffer to reduce corrosion. The approach might also work with zinc-air batteries, boosting their shelf life.
If these and other efforts pan out, lightweight, compact zinc- and aluminum-air batteries could provide backup power to electric cars, assert proponents.
Meanwhile, Tesla continues to ramp up lithium-ion battery production at its Gigafactory in Nevada and a planned battery factory in China — Tesla and battery partner Panasonic claim about 60% of global electric vehicle battery output. Chinese rivals like Contemporary Amperex Technology Ltd. (CATL) are also pouring billions into an effort to become China’s Panasonic. A key to success is leveraging growing domestic demand for electric cars.
Tesla, Porsche, and other electric car rivals have spent heavily on supercharging infrastructure with the goal of recharging electric car batteries as fast as filling a gas tank. Other approaches are emerging that might eventually allow electric vehicles to recharge on the go.
For example, the U.S. Energy Department’s Oak Ridge National Laboratory announced in October that researchers have demonstrated a 120-W wireless recharging system for electric vehicles. Oak Ridge engineers claim six times the power of previous wireless charging technology, representing what the lab asserts is “a big step toward charging times that rival the speed and convenience of a gas station fill-up.”
Oak Ridge National Laboratory’s 20-kW wireless charging system features 90% efficiency. (Photo: Oak Ridge National Laboratory)
Oak Ridge researchers demonstrated a 20-kW wireless charging system that is being modified for applications like delivery trucks. The research was sponsored by DoE’s Vehicle Technologies Office and performed at its National Transportation Research Center at the Oak Ridge lab.
The next step is scaling the power transfer level to 350 kW while exploring “dynamic wireless charging schemes” in which wireless charging pads installed under a roadway could automatically charge electric vehicles.
“The goal is dynamic charging at highway speeds,” said Veda Galigekere, project leader at the lab’s Power Electronics and Electric Machinery Group.
The wireless recharging architecture takes energy from the grid and converts it to high-frequency alternating current. The resulting magnetic field can be used to transfer power across a large air gap. Once transferred, it is converted back to direct current and stored in a vehicle’s batteries, said researchers.
“Wireless charging is a key enabling technology for transportation electrification because it’s safe, it’s convenient, and it’s highly efficient,” added Omer Onar of Oak Ridge’s Electrical & Electronics Systems Research Division.
— George Leopold is the former executive editor of EE Times and the author of “Calculated Risk: The Supersonic Life and Times of Gus Grissom” (Purdue University Press, Updated 2018).