Argonne National Laboratory Center for Nanoscale Materials U.S. Department of Energy

Batteries Get a Quick Charge with New Anode Technology

Tijana Rajh

Argonne nanoscientist Tijana Rajh holds a strip of material created from titanium dioxide nanotubes.

A team of researchers led by Tijana Rajh (Group Leader, Argonne Center for Nanoscale Materials NanoBio Interfaces Group), and Christopher Johnson (Argonne's Chemical Sciences & Engineering Division), working under a CNM user science project, discovered that nanotubes composed of titanium dioxide can switch their phase as a battery is cycled, gradually boosting their operational capacity. New batteries produced with this material can be recharged up to half of their original capacity in less than 30 seconds. By switching out conventional graphite anodes with titanium nanotube anodes, a surprising phenomenon occurs. As the battery cycles through several charges and discharges, its internal structure orients itself in a way that dramatically improves the battery's performance.

According to Hui Xiong (NanoBio Interfaces Group), titanium dioxide seemed like it would be unlikely to adequately substitute for graphite. "We started with a material that we never thought would have provided a functional use, and it turned into something that gave us the best result possible," she said. Another researcher in Rajh's group, Sanja Tepavcevic, has adopted a similar approach to make a self-improving structure for a sodium-ion nanobattery.

The reason that titanium dioxide seemed like an implausible solution for battery development lies in the amorphous nature of the material. Because amorphous materials have no internal order, they lack the special electronic properties of highly ordered crystalline materials. However, amorphous materials have not been known to undergo such profound structural transformations during cycling. Most of the known battery materials undergo the opposite transition: they start out as highly crystalline and degrade to an amorphous state upon cycling. Having anodes composed of titanium dioxide instead of graphite also improves the reliability and safety of lithium-ion batteries. In certain cases, lithium can work its way out of solution and deposit on the graphite anodes, causing a dangerous chain reaction known a s thermal runaway.

The Argonne discovery came from collaboration between two of the Laboratory's flagship user facilities: the Center for Nanoscale Materials and the Advanced Photon Source (APS). By combining state-of-the-art nanofabrication techniques with high-intensity X-rays to characterize the nanotubes, the Argonne researchers were able to quickly observe this unusual behavior.

H. Xiong et al.," Amorphous TiO2 Nanotube Anode for Rechargeable Sodium Ion Batteries," J. Phys. Chem. Lett.., 2, 2560-2565 (2011) dx.doi.org/10.1021/jz2012066 |

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November 2011

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