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A quiet revolution in rechargeable battery technology has helped drive a global market for portable electronic devices. The know-how is also being applied in outer space and in new, ‘greener’ cars.
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Mobile phones, digital music players, PDAs and laptop computers have become ubiquitous features of modern life. However, these power-hungry devices depend on the availability of battery technology that makes them useful, portable and affordable.
The market for rechargeable (or secondary) batteries has shadowed the boom in personal electronic devices that they serve. According to EUROBAT (the Association of European Storage Battery Manufacturers), the world market for rechargeable batteries was worth €19 billion in 2004, although more than half of this was for conventional automotive applications.
Today, worldwide, R&D investments on advanced rechargeable batteries are over $1 billion, having increased tenfold in the last five years. During the last two years, incentives to innovation have been set in place in the USA, in Canada, Japan, South Korea and China.
The increase in sales of personal device batteries, which feeds into further R&D investments, is reflected in patenting activity. According to Thomas Maxisch, patent examiner specialised in this technology at the European Patent Office, "there has been a growing interest for rechargeable batteries over the last couple of decades, with the shift in technology from lead-acid to nickel technologies and then to the recent dominance of lithium ion chemistry."
Patent filing activity for lithium (Li-) technology started in the early 1990s and quickly overtook the fairly well established Nickel Cadmium (NiCd) [1] and more recent Nickel Metal Hydride (NiMH) [2] technologies.
Lithium-ion frenzy
Since 2000, the lithium-ion battery has become the battery of choice for all laptop computers and a wide variety of other devices. The key to its success is its relatively high energy capacity compared to competing technology and its high energy density, making smaller, more powerful batteries.
"The lithium-ion battery works at three times higher voltage than the other technologies," says Maxisch. ‘A typical consumer rechargeable battery cell is rated at 1.2 volts. Lithium-ion batteries work typically at 3.6 volts. Voltage is proportional to energy density so a lithium battery has three times the energy density." On the downside, these batteries are more expensive but mass production and use in high value-added products takes the edge of this disadvantage.
The ‘lithium-ion' designation actually covers a range of chemistries: lithium manganese oxide [3 , 4] , lithium cobalt oxide [5] and lithium nickel oxide. Optimisation and integration of new materials for the anode, cathode or electrolyte are key to further progress in lithium battery technology. Thomas Maxisch points to new chemistries that offer good potential, such as lithiated olivine phosphates as a cathode material [6] .
Thomas Maxisch:
"nano-structured materials
for rechargeable batteries
are receiving great attention"
"Electrode and electrolyte materials have to be chosen carefully to ensure safety of operation: they have to sustain quite high electrochemical potentials and remain stable. Then, every new material needs careful integration into the overall chemistry of the battery to get the optimum performance", he warns. "In particular, there is also a lot of activity in the use of nanotechnology in batteries. Nano-structured materials can solve some problems with respect to optimisation".
Batteries in spacecrafts
Geoff Dudley is an expert in batteries for space applications at the European Space Agency's European Space Technology Centre. "Rechargeable battery technology is a critical ‘spin-in' technology for space applications," he tells.
There are critical parameters for space application: a high specific energy expressed as watthours per kilogram (Wh/kg) - meaning low weight and high energy storage - and very fast charge time with long cycle life.
"Some low-earth orbit satellites need batteries that will be able to operate up to 12 years which may mean 60,000 cycles," says Dudley. "Reliability is very important in space as a failed battery usually means a failed mission."
Li-ion batteries are now flying in about 20 spacecraft. The vast majority were supplied by European battery manufacturers - the three exceptions include the two intrepid and long-lasting NASA Mars Rover missions. Dudley has seen the specific energy for Li batteries increase as the technology is optimised.
"Today, the best-qualified batteries could give about 150 Wh/kg," he says. "This is five times the previous NiCd or three times nickel hydride technology. The current chemistry might be pushed up to 200 Wh/kg and new chemistries, for example based on lithium sulphur, might eventually reach 300 Wh/kg. Many of the requirements for power sources for satellites and other spacecrafts reflect those for the new electric vehicles."
Batteries in cars
With concerns about greenhouse gas emissions rising, interest in viable electric vehicles is also increasing. For vehicle applications, batteries need very high capacity (for good range), high rates of charge (during breaking) and discharge (to achieve acceptable acceleration), low re-charge time, high safety, low volume, low weight. The traditional lead-acid car battery can provide high power with high current but is too bulky and heavy for use in a modern all-electric car.
Hybrid Vehicles - combining conventional petrol or diesel engines with electric propulsion systems - are currently at the forefront of ‘clean vehicle' designs. Models, such as the Toyota Prius, use batteries that are charged by the braking action of the vehicle or directly from the engine. The Prius uses nickel based batteries that do not have the energy density of Li-ion technology but can deliver fast charge and discharge power. Li-ion technology is being introduced in the next generation of hybrid vehicles.
Another step is the Electric Hybrid Vehicle, also known as a plug-in hybrid or grid-connected hybrid, whose batteries can be recharged by plugging into a standard 110 Volt or 220 Volt outlet. Recharge could for instance take place at night, using cheaper, off-peak electricity, with great savings in comparison to an ordinary gasoline vehicle. One would wake up each morning with a fully charged battery pack.
Was the performance of rechargeable batteries to increase further, in particular with respect to lower re-charge time, one would expect to recharge on the road in a few minutes at the service station. That would make very appealing not just Electric Hybrid Vehicles, but also cars, buses, and scooters running on electricity only.
Fuel-cell future, or Li-ion ?
Fuel-cell technology, using hydrogen or methanol as fuel, is often put forward as the future alternative technology to batteries. Fuel-cells were indeed first used in spacecrafts, and have a progressively broadening market. Do fuel-cells and rechargeable batteries somehow complement or compete with each other?
"Over the next ten years, one can foresee many more hybrid vehicles on the road using Li-ion technology to get greater efficiency out of the internal combustion engine," says Agnès Gamez an EPO examiner in industrial chemistry with over nine years experience in the battery and fuel cell area. However, she does not predict the widespread use of fuel cells in private cars in the near future due to their complexity, weight, and cost.
"The use of stationary fuel cells for combined heat and power applications in offices, factories and residential areas will come first," she says. "And public transport - such as, for example, the fleet of hydrogen fuel cell buses that have recently been ordered for the 2010 Winter Olympics in Vancouver - are more likely early vehicle applications."
Hybrid vehicles are a near-term technology for increasing fuel efficiency and reducing greenhouse gas emissions from automobiles, she believes, while methanol powered fuel cells in dual-fuel vehicles could rather be a possibility for the medium term.
From the perspective of patenting
The rate of patenting in the
rechargeable battery field has grown steadily over many years, to be
outpaced by that in fuel-cells in the period 1999-2002. It is now on
the upswing again.
Patent examiner Agnès Gamez has made an
analysis of the historical distribution of patent applicants in Europe
in this field. "As you might expect in a market in which the Japanese
manufacturers have a dominance, we find that some 35% of patent
applications are from that country with the major players Toyota,
Matsushita and Nissan well represented," she says. A further 30%
originate from the United States and again major industrial players
feature, such as UTC, Gillette and General Motors.
"Europe accounts
for some 20% with the main active countries being Germany, France and
Great Britain," notes Gamez. Interestingly, major European filers
include not only industrial giants such as Siemens, but also
government-funded research institutions like Germany's
Forschungszentrum Jülich and the French CEA.
The remaining
activity encompasses the "rest of the world" with a large proportion
originating from South Korea. "Patent activity from Korea has greatly
increased over the past couple of years," comments Gamez. "This is
mainly due to a boom in patent applications from industries such as LG
and Samsung, in this area. Chinese patenting activity is also
increasing rapidly."
The rate of patenting in the rechargeable battery field has grown steadily over many years, to be outpaced by that in fuel-cells in the period 1999-2002. It is now on the upswing again. (click to enlarge )
- Journalist: Tim Reynolds, European Service Network
- Expert Opinion: Geoff Dudley at the European Space Agency; Thomas Maxisch and Agnès Gamez at the EPO.
- Chart and Data Research: Henry Lethiniemi, EPO.
- Photo Portrait: Erika Valencia, EPO.
- Research and Co-ordination: Leo Giannotti, EPO.
References
[1] e.g. FR2628892
[2] e.g. EP0284333
[3] e.g. US5266299
[4] e.g. WO9426666
[5] e.g. WO9218425
[6] e.g. WO9740541