New ORNL titanium dioxide material shows high-rate capability and long-time cyclability for Li-ion batteries
|Mesoporous TiO2–B microspheres. Click to enlarge.|
Researchers at Oak Ridge National Laboratory (ORNL) have designed and synthesized a new titanium dioxide material—Mesoporous TiO2–B microspheres—for high-power lithium-ion batteries. The material combines the advantages of fast lithium transport with a pseudocapacitive mechanism, adequate electrode-electrolyte contact, and compact particle packing in the electrode layer, and shows superior high-rate charge–discharge capability and long-time cyclability for lithium-ion batteries, according to their paper published in the journal Advanced Materials.
The new material allows the battery to be charged to 50% of full capacity in six minutes while the traditional graphite-based lithium-ion battery would be just 10 percent charged at the same current, said Hansan Liu, lead author of the paper. Compared to commercial lithium titanate material, the ORNL compound also boasts a higher capacity—256 vs. 165 mAh g-1—and a sloping discharge voltage that is good for controlling state of charge.
This characteristic combined with the fact oxide materials are extremely safe and long-lasting alternatives to commercial graphite make it well-suited for hybrid electric vehicles and other high-power applications.
The results could also have significance for applications in stationary energy storage systems for solar and wind power, and for smart grids. The titanium dioxide with a bronze polymorph also has the advantage of being potentially inexpensive, according to Liu.
At the heart of the breakthrough is the novel architecture of the mesoporous TiO2-B microspheres, which features channels and pores that allow for unimpeded flow of ions with a capacitor-like mechanism. Consequently, a lithium-ion battery that substitutes TiO2-B for the graphite electrode charges and discharges quickly.
Theoretical studies have uncovered that this pseudocapacitive behavior originates from the unique sites and energetics of lithium absorption and diffusion in TiO2-B structure.—Liu et al.
Co-author Parans Paranthaman noted that the microsphere shape of the material allows for traditional electrode fabrication and creates compact electrode layers. He also observed, however, that the production process of this material is complex and involves many steps, so more research remains to determine whether it is scalable.
Hansan Liu, Zhonghe Bi, Xiao-Guang Sun, Raymond R. Unocic, M. Parans Paranthaman, Sheng Dai, Gilbert M. Brown (2011) Mesoporous TiO2–B Microspheres with Superior Rate Performance for Lithium Ion Batteries. Advanced Materials. doi: 10.1002/adma.201100599