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Better batteries with boron
NEWS
The NIST lens has a focal length of about half a micrometer, a focusing scale that is almost impossible to achieve with conventional glass lenses. Moreover, the active behavior of the meta lens can be switched off by using higher frequency light as a switch, so that the lens can also act like a camera shutter but without the moving parts.
Materials Today Volume 16, Number 6 June 2013
‘Our lens will offer other researchers greater flexibility for manipulating UV light at small length scales,’ explains Lezec. ‘With its high photon energies, UV light has a myriad of applications, including photochemistry, fluorescence microscopy and semiconductor manufacturing. That, and the fact that our lens is so easy to make,
should encourage other researchers to explore its possibilities.’ The NIST team worked with colleagues at the Maryland NanoCenter at the University of Maryland, College Park, Syracuse University and the University of British Columbia, Kelowna, Canada. David Bradley
that of graphite – the most commonly used electrode material in today’s Li-ion batteries [J. Phys. Chem. Lett. (2013) doi:10.1021/ jz400491b]. The work, published in the Journal of Physical Chemistry Letters, confirmed experimental results suggesting that the weak binding between lithium and carbon was limiting the storage capacity of graphene. The Rice researchers went on to theoretically investigate the effects of modifying graphene for better lithium storage, by mechanically stressing it and chemically doping it. While mechanical modification did not increase graphene’s charge capacity, the addition of boron had a large effect. A stack of graphene layers in which a quarter of the carbon atoms were replaced by boron provided the optimum lithium storage capacity. The researchers found that C3B had a
theoretical capacity of 857 mAh/g – over twice as large as graphite’s 372 mAh/g. The team explain that in this arrangement, the boron attracts lithium ions into the matrix, but the bond is not so strong that it inhibits lithium movement in the presence of a more attractive cathode – a key consideration for its use within batteries. These stacks of C3B were also determined to have a comparable power density to graphite and very little volume variation during discharge/charge cycles. The Rice team say that their results help to ‘‘. . .clarify the fundamentals of lithium storage in low-dimensional materials’’. If a method to synthesize the boron–carbon compound in large quantities can be found, it is hoped that this theoretical study can lead to a practical outcome, in the form of high-capacity lithium-C3B batteries. Laurie Winkless
Better batteries with boron A mix of boron and graphene has been offered as a potential lithium storage solution by theorists at Rice University, leading to suggestions that high-capacity graphene batteries may not be too far off. Graphene has been a buzzword in materials research since it was first isolated in 2004, thanks to its impressive mechanical, thermal and electrical properties. The huge surface area of these one-atom-thick sheets of carbon (C) also highlighted graphene as a potential storage material for use in lithium ion batteries. But, in practice, it was found that lithium ions did not form strong enough bonds with pristine sheets of graphene to consider as a storage medium. However, work from a group of theoreticians at Rice University suggests that including specific boron (B) defects in the graphene lattice can hugely increase its charge capacity, making it comparable to
The new photovoltaic on the block A new class of photovoltaic solar cell based on self-assembling block copolymers is being developed by collaborators at Pennsylvania State and Rice universities. The organic materials being developed by chemical engineer Enrique Gomez and his team at PSU and colleague Rafael Verduzco of Rice arrange themselves into distinct layers that could outperform other polymer-based solar cells [Verduzco et al., Nano Lett. (2013) doi:10.1021/nl401420s]. Commercial, silicon-based solar cells are approximately 20% efficient at absorbing and converting incident sunlight into electricity. Experimental advances may have taken that to 25%. However, such devices are costly and fragile. Polymer-based photovoltaics have reached peaks of just 10% efficiency but are far cheaper to make and much tougher; there has thus been a good deal of research aimed at making plastic solar panels to bring solar energy more into 210
The NIST lens has a focal length of about half a micrometer, a focusing scale that is almost impossible to achieve with conventional glass lenses. Moreover, the active behavior of the meta lens can be switched off by using higher frequency light as a switch, so that the lens can also act like a camera shutter but without the moving parts.
Materials Today Volume 16, Number 6 June 2013
‘Our lens will offer other researchers greater flexibility for manipulating UV light at small length scales,’ explains Lezec. ‘With its high photon energies, UV light has a myriad of applications, including photochemistry, fluorescence microscopy and semiconductor manufacturing. That, and the fact that our lens is so easy to make,
should encourage other researchers to explore its possibilities.’ The NIST team worked with colleagues at the Maryland NanoCenter at the University of Maryland, College Park, Syracuse University and the University of British Columbia, Kelowna, Canada. David Bradley
that of graphite – the most commonly used electrode material in today’s Li-ion batteries [J. Phys. Chem. Lett. (2013) doi:10.1021/ jz400491b]. The work, published in the Journal of Physical Chemistry Letters, confirmed experimental results suggesting that the weak binding between lithium and carbon was limiting the storage capacity of graphene. The Rice researchers went on to theoretically investigate the effects of modifying graphene for better lithium storage, by mechanically stressing it and chemically doping it. While mechanical modification did not increase graphene’s charge capacity, the addition of boron had a large effect. A stack of graphene layers in which a quarter of the carbon atoms were replaced by boron provided the optimum lithium storage capacity. The researchers found that C3B had a
theoretical capacity of 857 mAh/g – over twice as large as graphite’s 372 mAh/g. The team explain that in this arrangement, the boron attracts lithium ions into the matrix, but the bond is not so strong that it inhibits lithium movement in the presence of a more attractive cathode – a key consideration for its use within batteries. These stacks of C3B were also determined to have a comparable power density to graphite and very little volume variation during discharge/charge cycles. The Rice team say that their results help to ‘‘. . .clarify the fundamentals of lithium storage in low-dimensional materials’’. If a method to synthesize the boron–carbon compound in large quantities can be found, it is hoped that this theoretical study can lead to a practical outcome, in the form of high-capacity lithium-C3B batteries. Laurie Winkless
Better batteries with boron A mix of boron and graphene has been offered as a potential lithium storage solution by theorists at Rice University, leading to suggestions that high-capacity graphene batteries may not be too far off. Graphene has been a buzzword in materials research since it was first isolated in 2004, thanks to its impressive mechanical, thermal and electrical properties. The huge surface area of these one-atom-thick sheets of carbon (C) also highlighted graphene as a potential storage material for use in lithium ion batteries. But, in practice, it was found that lithium ions did not form strong enough bonds with pristine sheets of graphene to consider as a storage medium. However, work from a group of theoreticians at Rice University suggests that including specific boron (B) defects in the graphene lattice can hugely increase its charge capacity, making it comparable to
The new photovoltaic on the block A new class of photovoltaic solar cell based on self-assembling block copolymers is being developed by collaborators at Pennsylvania State and Rice universities. The organic materials being developed by chemical engineer Enrique Gomez and his team at PSU and colleague Rafael Verduzco of Rice arrange themselves into distinct layers that could outperform other polymer-based solar cells [Verduzco et al., Nano Lett. (2013) doi:10.1021/nl401420s]. Commercial, silicon-based solar cells are approximately 20% efficient at absorbing and converting incident sunlight into electricity. Experimental advances may have taken that to 25%. However, such devices are costly and fragile. Polymer-based photovoltaics have reached peaks of just 10% efficiency but are far cheaper to make and much tougher; there has thus been a good deal of research aimed at making plastic solar panels to bring solar energy more into 210