Even though batteries used in electric cars have advanced in performance significantly over the years and more so recently, but it still leave some gaps in performance due to some of the inherent problems of batteries such as longer charging time, life of the battery (irrespective of its usage are not), and charge and discharge cycles.
On the other side a little different supercapacitors/ultracapacitor technology has even more technical issues for using them to store energy in electric cars. The biggest issue with the supercapacitors is they store less energy compared to batteries and the stored energy dissipates faster compared to batteries while the capacitors are idle. The researchers working on increasing the energy density by increasing the surface area of metal plates and also using a dielectric material to increase the capacitance. Graphene is very well employed as a metal layer. Below are some of the latest achievements in the super capacitor area:
Researchers at California NanoSystems Institute have developed a super capacitor which offers features of both a battery as well as a super capacitor. The super capacitor developed by California NanoSystems Institute Store six times more energy than the presently available commercial super capacitors in the market.
The concept used by these researchers is, they could able to increase the contact area between the electrolyte and the metal plates by creating three-dimensional Graphene structures using lasers.
In another case of similar research work by Rice University, researchers have created fingerlike interlocked patterns on a boron-infused sheet of polyimide. Afoam-like matrix of interconnected graphene flakes is created.
The charge storage capacity was boosted by four times by infusing the polymer with boric acid.
The process used for improving supercaps performance can also be used for making catalysts, field emission transistors and components for solar cells and lithium-ion batteries.
"The two-step process produces microsupercapacitors with four times the ability to store an electrical charge and five to 10 times the energy density of the earlier, boron-free version. The new devices proved highly stable over 12,000 charge-discharge cycles, retaining 90 percent of their capacitance. In stress tests, they handled 8,000 bending cycles with no loss of performance, the researchers reported."
The energy density of the super capacitors made using this process was increase by 10 times compared to the earlier boron free version. They can also charge and discharge 12,000 times with 90% of their capacitance retaining ability. On the physical bend test, these capacitors are designed to be flexible and they could withstand 8000 bending cycles.
The idea in both cases is to develop some kind of hybrid storage which includes both batteries and supercapacitors.