Swapping Graphite Anodes For Silicon Improves Li-ion Battery Capacity Five Times
Self-Assembling Silicon-Carbon Nanocomposite Courtesy of Gleb Yushin, Georgia Tech
Battery capacity is the main thing keeping our lifestyles close to the wall socket or to the gas pump. But
while we can extend our batteries capacity by going to lithium-ion technology, it would be nice to obtain
more power density. A group of researchers at Georgia Tech have devised a “bottom-up” self-
assembling nano-composite technique that might add that extra capacity by swapping less efficient
graphite anodes for high-performance silicon structures that could increase capacities five-fold.
Nanocomposites aim to boost the capacity of lithium ion batteries by five-times by hanging nanometer-
sized silicon particles on trees of carbon black that self-assemble into porous micron-sized spheres,
which increase an electrode's surface area with interconnected internal channels.
High-performance lithium ion batteries today use anodes made from carbon (graphite). Silicon has been
proposed as a substitute for graphite since it offers a theoretical improvement of 10-times in capacity
over graphite, but so far prototypes have proven too unstable for creating lithium batteries with a long
lifetime, according to professor Gleb Yushin at the Georgia Institute of Technology.
The problem, according to Yushin, is that silicon particles crack when they are formed at the same
granularity of graphite particles—about 15 to 20 microns. The new nanocomposite material solves that
problem by hanging 30 nanometer sized silicon particles on trees of carbon black which then self-
assemble into porous spheres about 10-to-30 microns in diameter. The resulting electrode remains
stable due to the durable carbon-superstructure that prevents cracking, but benefits from the increased
surface area afforded by the smaller silicon nanoparticles.
Common chemical vapor deposition processes allow the new hybrid silicon-carbon electrodes to be
mass produced economically, according to Yushin. He also claimes that because the tiny silicon
nanoparticles are permanently attached to the micron-sized carbon black trees, they avoid the health
hazards of processes that require handling of nanoscale particles.
So far Georgia Tech has fabricated experimental anode electrodes, which it is testing for use in
standard manufacturing processes for lithium batteries. Their prototype has survived over one hundred
recharge cycles without any degradation, leading the researchers to predict they will last for thousands
of recharges.
Besides Yushin, other Georgia Tech researchers involved in the project include Alexandre Magasinki,
Patrick Dixon, Benjamin Hertzberg and Alexander Alexeev, along with Alexander Kvit from the University
of Wisconsin-Madison, Igor Luzinov from Clemson University, and Jorge Ayala from Superior Graphite
(Chicago).
Funding was provided by a Small Business Innovation Research (SBIR) grant from the National
Aeronautics and Space Administration (NASA) to Superior Graphite and Streamline Nanotechnologies,
Inc. (Atlanta).
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Self-Assembling Silicon-Carbon Nanocomposite Courtesy of Gleb Yushin, Georgia Tech
Battery capacity is the main thing keeping our lifestyles close to the wall socket or to the gas pump. But
while we can extend our batteries capacity by going to lithium-ion technology, it would be nice to obtain
more power density. A group of researchers at Georgia Tech have devised a “bottom-up” self-
assembling nano-composite technique that might add that extra capacity by swapping less efficient
graphite anodes for high-performance silicon structures that could increase capacities five-fold.
Nanocomposites aim to boost the capacity of lithium ion batteries by five-times by hanging nanometer-
sized silicon particles on trees of carbon black that self-assemble into porous micron-sized spheres,
which increase an electrode's surface area with interconnected internal channels.
High-performance lithium ion batteries today use anodes made from carbon (graphite). Silicon has been
proposed as a substitute for graphite since it offers a theoretical improvement of 10-times in capacity
over graphite, but so far prototypes have proven too unstable for creating lithium batteries with a long
lifetime, according to professor Gleb Yushin at the Georgia Institute of Technology.
The problem, according to Yushin, is that silicon particles crack when they are formed at the same
granularity of graphite particles—about 15 to 20 microns. The new nanocomposite material solves that
problem by hanging 30 nanometer sized silicon particles on trees of carbon black which then self-
assemble into porous spheres about 10-to-30 microns in diameter. The resulting electrode remains
stable due to the durable carbon-superstructure that prevents cracking, but benefits from the increased
surface area afforded by the smaller silicon nanoparticles.
Common chemical vapor deposition processes allow the new hybrid silicon-carbon electrodes to be
mass produced economically, according to Yushin. He also claimes that because the tiny silicon
nanoparticles are permanently attached to the micron-sized carbon black trees, they avoid the health
hazards of processes that require handling of nanoscale particles.
So far Georgia Tech has fabricated experimental anode electrodes, which it is testing for use in
standard manufacturing processes for lithium batteries. Their prototype has survived over one hundred
recharge cycles without any degradation, leading the researchers to predict they will last for thousands
of recharges.
Besides Yushin, other Georgia Tech researchers involved in the project include Alexandre Magasinki,
Patrick Dixon, Benjamin Hertzberg and Alexander Alexeev, along with Alexander Kvit from the University
of Wisconsin-Madison, Igor Luzinov from Clemson University, and Jorge Ayala from Superior Graphite
(Chicago).
Funding was provided by a Small Business Innovation Research (SBIR) grant from the National
Aeronautics and Space Administration (NASA) to Superior Graphite and Streamline Nanotechnologies,
Inc. (Atlanta).
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