Electric cars, tablets, and cell phones could all benefit from batteries that hold more energy, charge faster, and last longer, but meeting all of those criteria is tricky. Here are some ways that researchers are developing materials for superior batteries.
The U.S. Department of Energy’s Pacific Northwest National Laboratory has developed a “sponge-like” nanomaterial made of silicon that could help lithium-ion batteries last longer between charges.
Leveraging Lithium
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Stanford researchers say they have reached a long-held goal among battery researchers: creating a battery anode made of pure lithium. This could lead to batteries that let cell phones run for three times as long between charges and make it possible to sell electric vehicles with a range of 300 miles for around $25,000, which is much less than today’s top-performing electric cars. The anode, usually made from graphite, is the part of the battery that sends electrons to the cathode. Lithium is better than graphite for an anode because it is lighter and has a higher energy density, but several challenges have made it hard for scientists to make anodes from this material. Battery life can be shortened by growths called dendrites on the anode’s surface that form when lithium expands during charging. To make the anode chemically stable and strong enough to handle this expansion, the researchers topped it with a flexible, 20-nanometer-thick wall that they made from carbon domes called nanospheres. The research was published in Nature Nanotechnology on July 27.
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Some researchers are replacing graphite anodes with silicon. In particular, they’re making the anodes with spongelike silicon nanostructures in hopes of increasing battery life by 30 percent. Researchers from the U.S. Department of Energy’s Pacific Northwest National Laboratory say that one downside of using silicon in this way is that it can balloon by three times its original size during charging and break the battery, so scientists must figure out how to make the battery components smaller for the material to work. The research was published in Nature Communications on July 8.
More Cycles
A commonly found material may also be used to triple the life span of lithium-ion batteries, say researchers at the University of California, Riverside. The key to the improved battery is that the anode is made of nontoxic silicon dioxide nanotubes rather than graphite. The researchers demonstrated that they could cycle the battery 100 times without losing energy storage, and they expect that it could last through hundreds of additional cycles. The findings were published in Scientific Reports in April.
Role Reversal
Instead of switching to a new material, University of Alberta researchers tried using graphite as the cathode rather than the anode in a lithium-ion battery and boosted the energy output by five to eight times. What’s more, the team thinks this new battery can beat two other types of batteries in development—lithium-sulfur and lithium-air. The research was published in Nature Scientific Reports on June 16. Through his company, AdvEn Solutions, lead researcher Xinwei Cui is working to develop three prototypes that focus on different improvements: super-high energy storage, quick charging, and a long life cycle.
Studying Structures
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Scientists have known for a long time that charging and draining batteries degrades them over time, but little has been known about how this damage occurs. Now scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have constructed 3-D images of a lithium-ion battery’s microstructures as the battery charges and dispenses energy—changes that affect how much energy the battery can store and how many times it can be recharged. They found that a key to a battery’s capacity is what goes on during the initial charging and discharging cycle. A paper explaining the research was published online in March in the German Chemical Society’s Angewandte Chemie.
The takeaway:
Today’s widely used lithium-ion batteries do improve each year, but progress is slow. While new battery designs and improvements in materials could offer incremental advances, it can be difficult to make some of the materials, like silicon, work in real-world environments. Dealing with the highly flammable nature of lithium batteries is another challenge.
