Supercapacitors finding new markets and applications as new types emerge
Life is good for supercapacitors manufacturers and developers. That includes those involved in the intermediate product, the supercabattery or Asynchronous Electrochemical Double Layer Capacitor (AEDLC) with its higher energy density achieved in a compromise of other operational parameters intermediate between supercapacitors and batteries, notably the supercabattery called a lithium-ion capacitor.
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 occupying 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; also, 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. Maxwell is the market leader that has just announced its best quarter ever. In recent times, its largest sales have been into electric buses in China, where its products protect the battery bank, improving performance and causing smaller batteries 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. 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 recognised 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 synthesise enhanced yet affordable materials for supercapacitors. The research team led by Prof. Ji-Hyun Jang from UNIST, previously reported a novel approach to synthesise chemical vapour 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 customisable 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 Farads per gramme (F/g) and 96% retention of capacitance after 10,000 cycles even at a high current density.
"Our work is very meaningful since we succeed in the fabrication of CVD-grown graphene with high qualities on a gram scale," said Prof. Jang. "When the mesoporous graphene balls are used as an electrode material for a supercapacitor, it proves great potential for energy storage devices with high efficiency. If the properties of mesoporous graphene are improved further by continuous research, developing an electric vehicle with high power will become a realisation not just a dream."
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 F/g, a considerable improvement from the 80 F/g achieved with alternative designs.
For its November conference IDTechEx has chosen a number of key topics;
•How supercapacitors wholly or partly replace batteries – what next?
•How supercapacitors replace electrolytic capacitors
•Road map of how supercapacitors, pseudocapacitors, supercabatteries and other variants are improving and what markets this will open up
•New forms – structural, smart skin, flexible, transparent, foldable, paper
•10 year forecasts for supercapacitors and their variants – operating parameters, costs, sales
•Today’s supercapacitors and their variants – comparative data, sales successes and applicational challenges
•The future of hybrid and pure electric EV’s using supercapacitors by land, water or air
•Applications for supercapacitors (cold start, regenerative braking, etc.)
•Supercapacitors in military and aerospace applications
•Static applications – grid, welding and other electrical engineering applications
•The future role of energy storage in renewable energy/energy harvesting technologies: challenges and solutions
•Supercapacitor applications in consumer electronics including mobile phones
•Technical challenges and improvements needed for supercabatteries to fully realize their potential
•Printing technology and supercapacitors, including control circuits and their integration
•Materials in energy storage: Graphene, Carbon Nanotubes, ionic liquids, non-flammable and non-toxic electrolytes, increased temperature range
Speakers will include Cap-XX of Australia which has licensed technology to Murata of Japan, Maxwell Technologies of the USA, the market leader, the University of Florida, The University of Surrey in the UK which has been managing a large European Union supercapacitor project and the University of California Davis which recently announced a breakthrough.