This is extremely promising. The
target today is about a ten fold improvement over our best to date
results. We will not quit then but that
is good enough to restructure our entire industrial base. That is literally what everyone has waited
for.
We have posted on a number of
promising approaches to the battery problem and most become very quiet soon
enough. Yet it is good to welcome
another serious contender. Sooner or
later we will get an effective battery and then sometime later we will get the
price we need.
Again the break point is an
effective battery that fits nicely in a car and gives easy recharges and a five
hundred mile range. From that point
onward, engineering will rejig everything to take advantage of storage. The new commodity will be automotive grade
battery packs
Sulfur in every pore
by Staff Writers
Munich, Germany (SPX) Apr 11, 2012
From smartphones to e-bikes, the
number of mobile electronic devices is steadily growing around the world. As a
result, there is an increased need for batteries that are small and light, yet
powerful. As the potential for the further improvement of lithium-ion batteries
is nearly exhausted, experts are now turning to a new and promising power
storage device: lithium-sulfur batteries.
In an important step toward the
further development of this type of battery, a team led by Professor Thomas
Bein of LMU Munich and Linda Nazar of Waterloo University in Canada has
developed porous carbon nanoparticles that utilize sulfur molecules to achieve
the greatest possible efficiency. (Angewandte Chemie, April 2012)
In prototypes of the
lithium-sulfur battery, lithium ions are exchanged between lithium- and
sulfur-carbon electrodes. The sulfur plays a special role in this system: Under
optimal circumstances, it can absorb two lithium ions per sulfur atom. It is
therefore an excellent energy storage material due to its low weight.
At the same time, sulfur is a
poor conductor, meaning that electrons can only be transported with great
difficulty during charging and discharging. To improve this battery's design
the scientists at Nanosystems Initiative Munich (NIM) strive to generate sulfur
phases with the greatest possible interface area for electron transfer by
coupling them with a nanostructured conductive material.
To this end, Thomas Bein and his
team at NIM first developed a network of porous carbon nanoparticles. The
nanoparticles have 3- to 6-nanometer wide pores, allowing the sulfur to be
evenly distributed. In this way, almost all of the sulfur atoms are available
to accept lithium ions. At the same time they are also located close to the
conductive carbon.
"The sulfur is very
accessible electrically in these novel and highly porous carbon nanoparticles
and is stabilized so that we can achieve a high initial capacity of 1200 mAh/g
and good cycle stability," explains Thomas Bein. "Our results underscore
the significance of nano-morphology for the performance of new energy storage
concepts."
The carbon structure also
reduces the so-called polysulfide problem. Polysulfides form as intermediate
products of the electrochemical processes and can have a negative impact on the
charging and discharging of the battery.
The carbon network binds the
polysulfides, however, until their conversion to the desired dilithium sulfide
is achieved. The scientists were also able to coat the carbon material with a
thin layer of silicon oxide which protects against polysulfides without
reducing conductivity.
Incidentally, the scientists
have also set a record with their new material: According to the latest data,
their material has the largest internal pore volume (2.32 cm3/g) of all
mesoporous carbon nanoparticles, and an extremely large surface area of 2445
m2/g. This corresponds roughly to an object with the volume of a sugar cube and
the surface of ten tennis courts. Large surface areas like this might soon be
hidden inside our batteries.
"Spherical Ordered Mesoporous Carbon Nanoparticles with Extremely
High Porosity for Lithium-Sulfur Batteries". Jorg Schuster, Guang He,
Benjamin Mandlmeier, Taeeun Yim, Kyu Tae Lee, Thomas Bein and Linda F. Nazar.
Angewandte Chemie, Article first published online: 1 MAR 2012 doi:
10.1038/nm.2720
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