Batteries could get a boost from an Oak
Ridge National Laboratory discovery that increases power, energy density, and
safety while dramatically reducing charge time.
A team led by Hansan Liu, Gilbert Brown, and
Parans Paranthaman of the Department of Energy lab’s Chemical Sciences Division
found that titanium dioxide creates a highly desirable material that increases
surface area and features a fast charge-discharge capability for lithium-ion
batteries. Compared to conventional technologies, the differences in charge time
and capacity are striking.
“We can charge our battery to 50% of
full capacity in six minutes while the traditional graphite-based lithium-ion battery
would be just 10% charged at the same current,” Liu says.
Compared to commercial lithium titanate
material, the ORNL compound also boasts a higher capacity—256 vs. 165
milliampere hour per gram—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, recently published in Advanced Materials, could also have
special 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 titanium dioxide, named 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 pseudo-capacitive behavior originates from the unique sites and
energetics of lithium absorption and diffusion in TiO2-B structure,” the
authors write in their paper, titled “Mesoporous TiO2-B Microspheres with
Superior Rate Performance for Lithium Ion Batteries.”
Paranthaman notes 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.
