Nano recharges battery technology

Image courtesy NASA

They are boring and mundane, but batteries, especially rechargeable types, have fuelled the development of the 24/7, “always on” lifestyle by providing portable power for mobile phones, laptops, Blackberries and MP3 players.

And it’s not just consumer electronics: higher and higher-powered batteries are in demand for a variety of automotive, energy, military and space applications.

For example, at the beginning of June the French battery developer Saft announced a contract to supply lithium-ion batteries to four satellites forming part of the Galileo project, which is Europe’s contribution to the Global Navigation Satellite System.

The world is crying out for battery-powered cars to replace petrol and diesel engines, while the number of features on mobile phones is now limited by the amount of power that batteries can deliver.

In order to keep up with these demands, novel rechargeable batteries need to be developed with higher power outputs, improved charge and discharge times, and a greater number of charge/discharge cycles.

Lithium-ion technology

In the past decade the most significant development has been the lithium ion battery, which has superior energy storage density to nickel cadmium and nickel metal hydride batteries. Lithium ion batteries have replaced these older varieties because they are lighter and can store more energy.

But they do have shortcomings – in particular lithium ion batteries are slow to recharge, wear out after being recharged a few hundred times, and do not release energy quickly enough for higher power applications.

Researchers around the world are currently hard at work developing the next generation of rechargeable batteries. Their reward will not just be a stake in the current market for rechargeable batteries worth over €4.6 billion in Europe alone this year, but also the possibility of widespread application of batteries in new markets such as electric vehicles. The world market is dominated currently by Japan with 46 per cent in 2004, China 24 percent and South Korea 22 per cent.

A battery, whether rechargeable or disposable, consists of two or more electric cells connected together. Each electric cell comprises a positive and negative electrode in an electrolyte solution, with electrons being released as a result of the negative electrode reacting with the electrolyte. In rechargeable batteries this chemical reaction is reversible.

Lithium ion batteries are examples of intercalation cells, meaning that the lithium ions are incorporated (intercalated) within layered electrodes. Current lithium ion technologies are limited mainly by the electrode surface area available for lithium intercalation (it has been estimated that only 25% of the volume of a rechargeable battery is actively used).

Adding nanoparticles to the electrodes should greatly increase their surface area and allow more lithium ions to be incorporated.

Enter nanotech

One of the first to develop a nanotechnology-enhanced battery was Altair Nanotechnologies, a US developer of ceramic nanomaterials. In February 2005, the company unveiled a lithium ion battery containing a negative electrode made from a lithium titanium oxide nanomaterial. Altair claims the power can be discharged fast enough to drive power tools. The battery can produce three times the power of its existing lithium-ion counterparts, recharge in six minutes and withstand 20,000 charge/recharge cycles.

Similarly, A123 Systems, set up in 2001 to commercialise technology developed at the Massachusetts Institute of Technology, announced in November last year that it had developed a battery with a positive electrode made from a nanostructured lithium-ion phosphate material. This can produce five times the power of existing varieties and recharges to 90 per cent capacity within five minutes.

 “We expect that our technology will have the same impact on high-power products as the introduction of first generation lithium-ion technology had on the development and commercialisation of consumer electronics in the 1990s,” says David Vieau, CEO and president of A123 Systems. These batteries are in use in a range of Black & Decker power tools, including circular saws and drills.

Toshiba, the Japanese electronics company has made similar claims for batteries that use nanomaterials in the electrode.

Europe gears up

European companies are also getting in on the act, but they are exploring other ways to improve battery technologies. For instance, Umicore, a Belgian materials technology company, is developing materials for positive electrodes in which the lithium ions are incorporated into a blend of nickel, cobalt and manganese oxides.

“The trend in portable electronics is to squeeze as much energy as possible in a given volume,” explains Laurent Gautier, product development manager. “One way to do this is to increase the cut-off voltage, so that you can charge your battery at a higher voltage potential. These new products based on nickel, cobalt and manganese allow us to do that.”

Another example is ReVolt Technology A/S, which span out of the Trondeim, Norway-based contract research institute Sintef in July 2005 with €7 million venture capital backing. Zinc batteries with substantially higher energy densities than other battery types have existed for over 20 years, but they cannot be recharged. The founder of ReVolt, Trygve Burchardt, has developed rechargeable zinc batteries that he claims could replace lithium ion ones. The ReVolt batteries cost considerably less to manufacture and have a lower environmental impact.

There is innovation also in the area of traditional lead acid batteries. Another start-up, DSL Dresden Innovation GmbH is developing composite grids for lead acid batteries that will allow them to be lower weight and higher power, while reducing the cost of materials. The company is planning to build a pilot plant next year.

Lithium ion batteries – credited with being the most important advance in energy storage in 100 years – were launched by Sony in 1990. But the key research breakthroughs were made by French, Italian and British researchers in the early 1980s. Now European researchers have banded together to apply to nanotechnology,  with the aim of bringing Europe back to the forefront of lithium-based energy storage.

Network of excellence

Sixteen research groups based in universities and institutes throughout Europe set up the Alistore (Advanced Lithium Energy Storage Systems) Network of Excellence in May 2004, specifically to explore the potential of nanopowders and nanocomposites electrodes and electrolytes.

According to the coordinator of the project, Jean-Marie Tarascon from the Laboratory of Reactivity and Solids Chemistry at the Université de Picardie Jules Verne, Amiens, Alistore has made progress on several fronts. His group has developed electrodes based on copper nanorods covered with an iron oxide film, while researchers at the University of St Andrews, led by Peter Bruce, have developed a way to synthesise cobalt oxide electrodes with a fine honeycomb structure. Alistore researchers filed for three patents in 2005.

The partners in the network are currently exploring ways to transform Alistore into a formal legal entity, which would give it more scope to liaise with industry. “Results have been achieved jointly that could never have been achieved by any of the partners working individually,” says Tarascon. “It now only remains to find ways to convert these results into low-cost and high performance battery systems.”

US and European firms are also beginning to team up to challenge Asian dominance in the market. In January 2006, Saft announced a joint venture with Johnson Controls, a US supplier of automotive components, to develop, produce and sell advanced batteries for electric vehicles. “The benefits of the combined resources of our two companies give us confidence that we will achieve significant market breakthroughs in the next 12 months,” predicts John Searle, Saft’s CEO.