The news keeps coming. This development promises a power delivery of one megawatt per kilo of device and an energy density up there with the super capacitors.
The fabrication method sounds like it could be easily automated. This strategy is very clear and also very convincing. I cannot comment on how it compares to EEStor as they are clearly using a different approach and it is not fully described yet. They do claim that commercial delivery is soon.
This means though that the advent of a commercial device is soon form either approach.. Such a device will swiftly convert the automobile industry to electric just as quickly as possible.
Atomic construction yields punchier power store
18:00 15 March 2009 by Colin Barras
Devices from electric cars to laptops could benefit from a new kind of capacitor, which combines the best features of conventional devices to store a large quantity of charge and release it rapidly.
Electrostatic capacitors store charge on the surface of two conducting plates separated by an insulating layer. Their advantage is that they can store and release energy much faster than batteries.
That makes them ideal candidates to replace batteries in devices that require speedy discharge of power, such as electric cars. However, electric capacitors can hold only limited charge. Supercapacitors that store charge chemically as well as electrically have greater capacities, but perform only as well as the best batteries.
Now a prototype capacitor has been made that manages to store power as densely as a supercapacitor, but deliver it at speeds comparable with electrostatic capacitors.
Best of both worlds
It was made by chemist Gary Rubloff at the University of Maryland, with colleagues from the Korea Advanced Institute of Science and Technology.
The secret to the prototype's performance is that it actually has 10 billion tiny capacitors, each just 50 nanometres across, crammed into every square centimetre. Electrodes connect up the mini devices so they can function as a single unit.
The team starts the creation of such small capacitors by anodising – adding a surface layer of oxide – a sheet of aluminium foil to create a regularly spaced array of nanopores across its surface. Each pore is then filled with three nested, concentric layers of material that function as the traditional conductor-insulator-conductor arrangement of an electric capacitor.
The conducting layers are made from titanium nitride, and the insulating layer from aluminium oxide. They are laid down with a highly precise way of depositing nanoscale structures called atomic layer deposition (see image).
That technique makes it possible to create thin layers of metals with unprecedented accuracy, says Rubloff: That is why the semiconductor industry is heavily pursuing atomic layer deposition to make a next generation of computer chips, he adds.
The resulting capacitor can deliver energy at a speed typical of electrostatic capacitors, at a rate that would allow a single kilogram to deliver one megawatt of power – enough to power 10,000 100-watt light bulbs. It can also store energy as densely as a supercapacitor, with 1 kg holding 2500 joules.
"Our primary target [for this technology] is as part of a hybrid battery-capacitor system for electric cars," says Rubloff. "But there are many [potential] small scale applications, [including] better electrical storage systems for cellphones or laptops."
The next step is to tweak the design to improve its performance – for instance, the team will experiment with deeper pores that can each hold bigger capacitors and thus store more energy.