Materials Science: Lithium-Ion Batteries 2.0

Ten years ago, the first generation of lithium-ion batteries enjoyed prominence for markedly advancing portable power technology for small electronics. Cell phones, laptop computers, and other mobile devices commercialized in the early 1990s typically used nickel-based batteries. But by the new millennium, those devices’ popularity had soared, thanks to lithium-ion batteries that weighed less and lasted longer.

Then came an advance that changed the lithium-ion battery scene substantially: In 2002, MIT’s Yet-Ming Chiang and coworkers reported that doping the inexpensive and stable cathode nanomaterial LiFePO₄ with Mg²⁺, Nb⁵⁺, and other ions boosted the electrical conductivity by a whopping eight orders of magnitude relative to the undoped material (Nat. Mater., DOI: 10.1038/nmat732). The discovery, which led to batteries that could be charged and discharged repeatedly at extraordinary rates, ushered in a new era—what Chiang refers to as “lithium-ion batteries 2.0.”

Within a few years, the company that Chiang cofounded to commercialize this battery technology, A123 Systems, was able to move into high-powered applications previously untouched by lithium-ion batteries. For example, the batteries were used in a new line of DeWalt power tools. And they ran electric motorcycles that repeatedly set speed records. In short, Chiang’s materials advance helped give rise to lithium-ion batteries with some muscle.

The batteries continue to move into areas that once were unimaginable. In the transportation sector, for example, lithium-ion batteries now power some 3,000 hybrid-electric city buses across North America and have collectively racked up more than 300 million miles of road service, Chiang says. Commercial versions of the batteries are now used in several lines of electric and hybrid-electric passenger cars. In addition, specialty batteries have been used to power Formula 1 race cars, replacing liquid fuels, and the world’s fastest electric car, the Buckeye Bullet, which topped 307 mph in 2010.

LiFePO₄ batteries have also made inroads in the electric power industry. The batteries are used in commercial facilities for grid-scale storage, short-term peak-power stabilization, backup power, and integrating power generated at wind farms into the electric grid.

Despite these successes, however, A123 Systems has fallen on hard times. It filed for bankruptcy in October, and as of C&EN press time it was in the process of being split up and sold. As Chiang explains, A123 undertook major manufacturing scale-ups to keep pace with the projected rapid growth in lithium-ion battery demand by the electric-vehicle industry. “But that market simply has not grown as quickly as was forecast,” he says.

“We’re looking now beyond lithium-ion 2.0,” Chiang adds. His group and others are searching for materials that may lead to a third generation of lithium-ion batteries, ones that provide even lower cost and longer peak-power solutions in the area of electric-grid storage.