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Rice University - Add Boron for better batteries

Theorists state Graphene-boron mix demonstrates promise for lithium-ion batteries

DCN Corp® - A theory developed at Rice University - led by the physicist Boris Yakobson - determined that a graphene/boron compound would excel as an ultra-thin anode for lithium-ion (Li) batteries.  The compound would store far more energy than graphite electrodes used in current batteries.  Credit - Vasilii Artyukhov from Rice UniversityIrate frustration led to the discovery by the Rice University (RU) scientists, when they determined how Graphene might be made useful for high-capacity batteries.

Theoretical calculations led by the physicist Boris Yakobson - found that a Gaphene/Boron anode should be able to hold a lot of lithium (Li) and perform at a proper voltage for use in Li-ion batteries.  Such a discovery appears in the American Chemical Society's (ACS) Journal of Physical Chemistry Letters. [1]

The future potentials offered by Graphene are becoming clearer by the day - especially as labs around the world grow and test the one-atom-thick form of carbon (C).  Because the nanomaterial is as thin as possible - battery manufacturers hope to take advantage of Graphene's massive surface area to store Li ions.  Subsequently counting both sides of the material - one gram would cover 2,630 square meters (m2) - at least equivalent to half a football field.  However, there's a problem, which is that the ions do not stick to Graphene very well.

Yakobson states - "As often happens with Graphene, people over-sold how wonderful it would be to absorb lithium,".  Yakobson's group analyzes relationships between atoms based on their intrinsic energy - "but in experiments, they could not see it, and they were frustrated."

Interestingly scientists at the Honda Research Institute - who are interested in powerful batteries for electric cars - requested for Yakobson to view the situation.  Yakobson went onto state - "We looked at the theoretical capacity of an ideal sheet of graphene, and then how it could or could not benefit from curvature (into a nano-tube) or topological defects.  Our initial expectation was that it would improve lithium binding."  "But the theory did not show any significant improvement," - he said.  In addition, Yakobson stated - "I was disappointed, but the experimentalists were satisfied because now their observations made sense."

The calculations conducted - involved Graphene with defects, in which the honeycomb array is disrupted by five- and seven-atom polygons, fared no better.  However, Yakobson stated - "So we decided to explore defects of different types where we replace some carbon atoms with another element that creates more attractive sites for lithium," - "and boron is one of them."

Yakobson continues to state - "A carbon/boron compound in which a quarter of the carbon atoms are replaced by boron turned out to be nearly ideal as a way to activate Graphene's ability to store lithium."  Essentially boron (B) attracts Li ions into the matrix, but not so strongly that they cannot be pulled away from a carbon/boron (C/B) anode by a more attractive cathode.  On this point - Yakobson states - "Having boron in the lattice gives very nice binding, so the capacity is good enough, two times larger than graphite," - and "at the same time, the voltage is also right."  Please Note graphite is the most commonly employed electrode in Li-ion batteries.

Yakobson and Rice graduate student Yuanyue Liu, first author of the paper, calculated that a fully lithiated sheet of two-dimensional grapene/boron would have a capacity of 714 milli-amp hours per gram (mAh/g).  Such a capacity translates to an energy density of 2,120 watt-hours per kilogram (W.h/kg) - much greater than graphite, when paired with a commercial lithium cobalt oxide (LiCoO2) cathode.  In addition, the theorist also determined that material would not radically expand or contract as it changes and discharges.  Yakobson states - "In this case, it seems quite reasonable and exceeds - theoretically, at least - what is available now,"

In summary, an important step going forward will be to find a way to fabricate the C/B compound in large quantities - "It does exist, but it's not commercially available" - as Yakobson concludes. Original article available here

As with previous similar kind of nano thin film news articles - DCN Corp finds the above research extremely interesting, and wishes to find-out if the same thin film USPs can be achieved from the company's homogeneous dip coating displacement protocol?  If so, and you or your colleagues are interested in making the above a reality - please ensure to contact the company as soon as practicably possible.

[1] Yuanyue Liu, Vasilii I. Artyukhov, Mingjie Liu, Avetik R. Harutyunyan and Boris I. Yakobson - Feasibility of Lithium Storage on Graphene and Its Derivatives. Journal of Physical Chemistry Letters 4, 10, 1737-1742 (2013). Journal citation available here