Supercapacitors Gain Ascendancy

In some contrast to lithium-ion batteries, where the number of manufacturers is rising to 200 amid spectacular bankruptcies that are only a foretaste of the shakeout to come, there are only 80 manufacturers of supercapacitors and supercabatteries, none of them not sitting on huge, largely idle production lines like those encountered at leading lithium-ion battery companies. In part, the optimism comes from the fact that supercapacitors are improving faster than batteries and they have the potential, theoretically at least, to match or hugely out-perform the parameters of batteries. Already power density is magnitudes better and energy density, typically one tenth of that of a lithium-ion battery, is rapidly improving without adding major expense down the production line and non-toxic, non-flammable versions abound, in contrast to the situation with Li-ion batteries. These improvements trigger many new applications such as replacing a lead acid battery in a truck with a same-format supercapacitor to guarantee cold starting and replacing lead acid batteries for micro-hybrid conventional cars known as stop-start; where over 600,000 supercapacitors have been supplied by Maxwell Technologies alone, the market leader that has just announced its best quarter ever. In recent times, its largest sales have been into electric buses in China, protecting the battery bank, improving performance and causing less battery to be needed.

It is relatively easy for supercapacitor companies to raise funds. Acquisitive Ioxus, a manufacturer of premium performance ultracapacitor technology for use in transportation, industrial and energy applications, received $15 million in Series C funding from investors. Ioxus announced the investment via documentation filed with the U.S. Securities and Exchange Commission (SEC) on July 12, 2013. The Westly Group, a venture capital firm based in Menlo Park, California led the financing. Additional investors include Northwater Capital Management, Braemar Energy Ventures, Energy Technology Ventures, a joint venture of General Electric, NRG Energy and ConocoPhillips, and Aster Capital. The company plans to use the funds to further research and development, expand its manufacturing capabilities and increase sales and marketing operations. "We are delighted to spearhead this round of funding for Ioxus at a time when the company and market are primed for dramatic global growth," said Mike Dorsey, Managing Partner, The Westly Group.

Recently, Ioxus announced 80% annual growth in Japan, a progressive market for ultracapacitor applications, though it was in Hong Kong that Meidensha of Japan recently landed the world's largest supercapacitor order at over $300 million.

 

Earlier in 2013, Ioxus unveiled the 1200F iCAP™ cell, a high-powered building block for a new family of advanced module products enabling superior start/stop designs for combustion engine vehicles. This introduction followed the successful launch of three new modules for renewable energy and heavy transport applications: the iMOD® 80V/12F, 16V/500F and 48V/165F series. For the market as a whole, IDTechEx forecasts 30% real growth, in line with recently declared results for the industry leaders and the new markets about to be opened such as major use in capturing rotational and vertical energy in material handling, braking of elevators and mainstream replacement of lithium-ion batteries in hybrid electric vehicles.

The excitement lies in the potential for better supercapacitors as much as the surging rate of sales. Theoretically, graphene based supercapacitors could have over six times the energy density of lithium-ion batteries while retaining vastly superior cycle life, calendar life, reliability and power density and the ability to be fully discharged. Graphene has been recognized as a promising active material for supercapacitors due to its outstanding electrical conductivity and large surface area, as they are the two most important requirements for supercapacitors. Mostly, the energy density figures offered are a mere one hundredth of this because the graphene is so impure and re-agglomeration remains a problem. Indeed, having a pre-layer on the electrode that firmly holds atomic thickness sheets is a major challenge too.

Researchers from Ulsan National Institute of Science and Technology (UNIST) in Korea recently developed a new method to massively synthesize enhanced yet affordable materials for supercapacitors. The research team led by Prof. Ji-Hyun Jang from UNIST, previously reported a novel approach to synthesize chemical vapor deposition-grown three-dimensional graphene nano-networks (3-D GNs) that can be mass produced while retaining the excellent properties of 2D graphene and published in Scientific Reports in May 2013. Now, Prof. Jang has demonstrated a unique route to obtain a mass-producible mesoporous graphene that does not re-agglomerate. It is a mesoporous graphene ball (MGB) with a large surface area and great conductivity, via precursor-assisted CVD, using metal precursors as a catalyst which is applicable to supercapacitors. Compared to the conventional graphene synthesis methods, the new approach is scalable and able to produce high quality and customizable graphene with better environmental impacts.

 

With these MGBs, the capacity of supercapacitors has been improved significantly. Due to the unique mesoporous structure, three-dimensional networks are formed, which help to improve conductivity. Furthermore, mesopores inside the graphene surfaces induce nanochannels to transport ions in electrolyte, and improve the properties of supercapacitors.

 

The MGB presents a specific surface area of 508 m2/g and mesoporosity with a mean pore diameter of 4.27 nm. The conductivity of the p-doped MGB obtained from more than 10 samples was 6.5 S/cm. The MGB-based supercapacitor shows good performance, including an excellent capacitance of 206 F/g and 96% retention of capacitance after 10,000 cycles even at a high current density. Prof. Jang said the following:

 

 

In a totally different approach, Esha Khare an 18-year-old high school graduate from California won the Intel Foundation Young Scientist Award of $50,000 for her invention of an ultra-fast charging gadget that can load power into a phone in 20 seconds. She used a hydrogenated titanium dioxide core, which, when combined with its polyaniline shell, increases both capacitance and density. In a test, Khare's supercapacitor exhibited capacitance of 238.5 Farads per gram, a considerable improvement from the 80 Farads per gram achieved with alternative designs.