Blackest material created from gold nano-spheres attached to gold nano-rods may find use in solar energy harvesting

On the chemistry world website I recently read about researchers at the King Abdullah University of Science and Technology in Saudi Arabia who have created a new material containing particles in the form of a metallic nano-sphere attached to a metallic nano-rod. Dispersed in a liquid this new material is the darkest ever created, absorbing 98 to 99% of light in the wavelength range between 400 and 1400nm. The King Abdullah researchers claim that their material absorbs 26% more light than carbon nanotubes which were the previous record holder in the in the field of black materials. Among possible uses for this material that I have seen mentioned are solar cells, solar water desalination, and optical interconnects. This material in not a photovoltaic material, but it potentially has the ability to absorb light over a wide frequency range and re-emit light in a very narrow frequency band. This property could be used in conjunction with a PV material to utilize a larger portion of the solar spectrum than do current silicon solar cells.

The nano particles actually fabricated were made out of gold. I do not think that gold is necessarily required to make such a material, but this project was a research demonstration, and gold was apparently the easiest material out of which to create nano particles with the right properties. Interestingly the design of this material was inspired by the structure of the scales on the cyphochilus beetle which is an exceptionally white material, that is a material which reflects almost all of the light which shines on it. After the researchers had deciphered the structure of these scales and figured out their operating principle they realized that they could invert the structure and create an exceptionally black material.

Whether or not this discovery will lead to practical solar energy harvesting devices remains to be seen.

Electrovaya/Litarion produce Li ion batteries with cycle life >9000 at 100% depth of discharge

Lithium ion battery manufacturer Electrovaya and its whollly owned subsidiary Litarion have announced the availability of a new lithium ion battery with very long cycle life (>9000 at 100% depth of discharge). They also claim that this cell offers superior safety characteristics and potentially lower manufacturing costs (ultimately as much as 50% lower) than conventional automotive lithium ion batteries. The Electrovaya batteries use the typical EV battery (e.g. Tesla and Nissan Leaf) chemistry of a Lithium/Nickel/Manganese/Cobalt (NMC) cathode and a graphite anode. The feature which distinguishes the new Electrovaya/Litarion battery is the ceramic coated separator. The separator is a thin porous membrane which allows ions to to move from one electrode to the other but prevents contact between the electrodes. The separators have a strong influence on the battery safety and on battery cycle life. Apparently they are also very expensive if a new separator can really drive battery cost down by 50% as claimed in the Electrovaya/Litarion press release. A cycle life of 9000 also raises the possibility that an automotive battery back could last the lifetime of the car. The avoidance of buying an expensive battery replace midway through the life of an EV is an attractive possibility. However, since the electrode chemistry is not changing this battery does not represent an improvement in energy density or EV range.

Apart from automotive applications, the very long cycle life of these batteries may make them potentially attractive for grid energy storage applications which require multiple cycles per day. At one cycle per day it would take 24 years to realize the full value of the battery, which is a long time scale in our current system of economic production. For short time scale, high value grid balancing applications such as frequency regulation, which requires multiple cycles per day, these batteries might be an attractive technology in spite of their relatively high cost per kWh. For example the Tesla Power Wall has an installed price of $714/kWh. If you could reduce this cost to $500/kWh then 9000 cycles would result in a cost of 5.5ยข/kWh plus interest. For a high value application like frequency regulation this might be an attractive proposition. Batteries which use LiFePO4 cathodes have often been promoted for grid storage application over batteries using the NMC cathode because of superior cycle life and safety, even though their energy density is lower. This new NMC design may take away these advantages from the LiFePO4 chemistry.