Batteries and hydrogen fuel cells are vying to become the cheapest, cleanest way to power vehicles, in hopes of one day unseating the gasoline engine as the propulsion system of choice. Recent breakthroughs have brought both technologies closer to that goal.
With fuel economy standards ratcheting up under President Obama's climate action agenda, automakers are under pressure to put more zero-emission vehicles on the market. In this context, there's high demand to make battery-electric and hydrogen fuel-cell vehicles cheaper and more accessible to a wider set of consumers.
In the hydrogen space, researchers at Stanford University revealed today that they've developed a low-cost, emissions-free device that can produce hydrogen renewably through electrolysis of water using the power from an ordinary AAA battery. Unlike existing electrolyzers that use precious-metal catalysts, the Stanford group used a catalyst made from abundant and inexpensive nickel and iron that was active enough to split water at room temperature with a single 1.5-volt battery.
"This is the first time anyone has used non-precious metal catalysts to split water at a voltage that low," Hongjie Dai, a professor of chemistry at Stanford, said in a statement. "It's quite remarkable, because normally you need expensive metals, like platinum or iridium, to achieve that voltage."
A fuel-cell vehicle works by combining hydrogen on board with oxygen from the air to produce electricity and propel the car. The only tailpipe emission is water.
However, most hydrogen today is made by steam reforming natural gas at large, industrial-scale facilities, which is an energy-intensive process that releases carbon dioxide into the air. Scientists are working on cheaper ways to make renewable hydrogen in order for fuel-cell vehicles to be considered truly zero-emission cars on a life-cycle basis.
A non-emitting fuel
This spring, the California Energy Commission announced it will invest $46.6 million to accelerate the development of 28 additional publicly accessible hydrogen refueling stations. California now has a total of 54 stations either built or planned. The state requires that 33 percent of all hydrogen for transportation come from renewable sources, either directly from a biogas or using electrolysis powered by wind or solar.
Companies like Connecticut-based Proton Onsite already sell electrolyzers that can create hydrogen from renewable electricity.
FuelCell Energy Inc., another Connecticut-based company, has developed a novel way to make renewable hydrogen directly from biogas at a wastewater treatment plant. But both of these technologies are still very high-cost.
Stanford graduate student Ming Gong, lead author of the study, published today in Nature Communications, will continue to test the cheap nickel-based catalyst in an attempt to improve durability. The electrodes on the current device start to decay after a few days, he said. Next, the team plans to develop a water splitter that runs on electricity produced by solar energy.
There's also been progress on the battery front. Michigan-based Sakti3 announced this week that its solid-state lithium battery cells achieved record energy density of more than 1,100 watt-hours per liter (Wh/l), which is roughly double that of today's leading lithium-ion battery technology.
Two years ago, the company demonstrated that its technology could achieve more than 1,000 Wh/l in volumetric energy density in a research-grade test. But Sakti3 stayed quiet on developments until it could prove the technology worked and was repeatable on fully scalable, cost-effective equipment.
"We've been able to demonstrate a battery cell with very, very high energy density about double what's available now on the marketplace," said Ann Marie Sastry, CEO of Sakti3. "We believe the significance of this finding is not only the high energy density, which of course others have demonstrated high energy density on other energy systems -- what's exciting is we've demonstrated it on scalable equipment that's commercial, normal equipment you'd find at a mass manufacturing facility."
Typical lithium-ion batteries rely on a liquid electrolyte that, over time, can degrade the battery and cause a fire or even an explosion. Lithium-ion batteries also need extra packaging inside a vehicle for more protection.
Solid-state batteries are more durable as well as more energy-dense than their lithium-ion counterparts. Past attempts at making solid batteries used manufacturing processes that were prohibitively expensive. Sakti3's recent breakthrough relies as much on its novel, low-cost production process as it does on the battery technology itself.
Sakti3's first target market will be for consumer electronics, but from there it's an established and natural progression to automotive batteries, said Sastry. If successful, Sakti3's battery technology could make the 300-mile, $25,000 electric car a reality.
Lithium-ion batteries get upgraded
Researchers are also actively working to improve the performance of traditional lithium-ion batteries to try and achieve the sought-after 300-mile electric vehicle. For instance, last month, another Stanford research team announced a breakthrough lithium-ion battery design that improves both energy density and durability (ClimateWire, July 30).
Yesterday, the Department of Energy announced $17 million to advance environmentally friendly transportation technologies, including $1.5 million to develop safer lithium-ion batteries for electric vehicles.
Many experts argue that batteries and fuel cells aren't in direct competition, that each technology has its own set of benefits and drawbacks. And, ultimately, both are needed to reduce greenhouse gas emissions and effectively combat climate change. But in the near future, at least, battery electric and hydrogen-powered vehicles are likely to vie for the same coveted early-adopter consumers to scale up the technology.
Elon Musk, CEO of the popular battery electric car company Tesla Motors, has gone as far as calling hydrogen fuel cell vehicles "bullshit." On Tesla's second-quarter earnings call last month, he denounced the technology based on inherent inefficiencies, high costs and the complexity of setting up hydrogen fueling infrastructure.
Fuel-cell vehicle proponents, meanwhile, tout the vehicles' long range and short refueling time -- 4 minutes versus the 30 minutes, at best, it takes to fast-charge a plug-in vehicle.
"Hydrogen-powered vehicle would by far outrun battery-powered vehicle due to much higher energy density," said Hongjie. "This is why interest in hydrogen fuels has been always around, and picking up as more car makers seem to be rolling out fuel-cell-powered vehicles."
Several major automakers have made a big bet on fuel-cell vehicles. Hyundai started leasing fuel-cell vehicles in Southern California this summer. Toyota and Honda plan to begin selling fuel-cell vehicles next year.
Both batteries and hydrogen fuel-cell technologies have a ways to go before they'll overtake the internal combustion engine as the dominant vehicle propulsion technology. But researchers in both camps are now firmly locked in a race toward that finish line.
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