October 8, 2010 – Ottawa, Ontario
Global demand for hybrid electric vehicles and plug-in hybrid electrical vehicles is growing rapidly. NRC researchers and their partners are working to improve the performance, lifespan and safety of lithium ion batteries, which have three times greater energy density than the nickel metal hydride batteries now used in hybrid vehicles. Their goal is to make lithium ion batteries safe enough in large format to use in vehicles while significantly lowering their cost.
NRC Highlights recently spoke with Dr. Isobel Davidson, leader of the Clean Energy Technologies Program at the NRC Institute for Chemical Process and Environmental Technolog, about some of the challenges we face to develop the next generation of lithium ion batteries.
Question: What is the most exciting development happening now in lithium ion batteries?
Answer: There is a renaissance of interest in electrical storage, largely driven by the need to wean ourselves off fossil fuels. We need electrical storage solutions to allow the electrification of transportation, which is almost totally dependent on liquid hydrocarbons, and to stabilize our electrical grids so they can run on renewable energy. Lithium ion technology is well suited to both needs. However, there are two major issues: lithium ion batteries, on the scale required for electric vehicles, cost too much and there is a safety issue that needs to be addressed.
In transportation, there's always the risk of an accident, which could rupture the battery, so we need them to be safe in the charged state. And if they're accidentally exposed to air, we don't want them to leak anything nasty. Right now, the lithium ion batteries used in cell phones and other consumer electronics contain some chemicals that are very reactive, corrosive and/or toxic.
Q: What traits would the ideal battery have?
A: It would be rechargeable and have about 3.6 volts output - as do the lithium ion batteries used in today's consumer electronics. Nickel metal-hydride and nickel-cadmium cells have typically about 1.2 volts, so to match the same output as a lithium ion battery you need three times as many. The battery would also be inexpensive. It would have 15 years of operating life. And it would have components that are environmentally benign.
Q: What is the "holy grail" of lithium ion battery research?
A: The cost, in large formats, has to be cut at least in half. A transportation quality battery now costs about a thousand dollars per kilowatt hour. For typical electric vehicles for which you need about 35 kilowatt hours, this is not affordable since the battery alone would cost $35,000. You would have to operate the vehicle for a very, very long time and many, many kilometres to recoup your investment.
Q: What is NRC working on right now?
A: NRC is developing alternative materials for use in the major components of batteries - including anodes, cathodes, electrolytes, etc. We're looking for materials that are greener, cheaper and safer. We're working on some very innovative technologies such as safer electrolytes based on ionic liquids. Ionic liquids are molten salts that can combine the good ionic conductivity needed for high power output with low flammability. And we're working on high voltage cathodes like the lithium nickel manganese spinel, which is a five volt cathode that can increase the power and energy of the battery.
Q: What distinguishes NRC from other research players?
A: We work on very innovative materials and we look a little outside the box. We are able to draw on expertise in materials science, electrochemistry and process engineering.
Q: What is innovative about the materials you're working with?
A: In the case of the ionic liquids that we're studying, many of them never existed before. In other cases, we're modifying known materials to increase both their energy output and their stability by doping them with other constituents, modifying their chemistry or modifying their principal construction.
Q: What is the biggest misconception that people have about electric vehicles?
A: People think they're not going to be peppy. In fact, electric motors have very good torque and can accelerate the vehicles very rapidly.
Another misconception is something called range anxiety. Some people worry about running out of battery energy in an awkward spot. But the reality is that for normal daily use, charging the battery on most nights will be more than enough to provide the range needed. . You won't drain the whole battery unless you go on a very long trip.
Q: Is there any concern about the capacity of the grid?
A: Yes. It could be a problem in urban areas where it's hard to add new capacity. Also, the more affluent the neighborhood, the more likely that people will have electric vehicles, which could create a lot of local demand on the grid.
Another challenge is that an electric vehicle should not be plugged into a standard outlet in the garage - it could overheat the electrical circuit and cause a fire. You need an upgraded outlet for charging an electric vehicle. Also, in many large cities, such as in Europe, many people park their cars on the street and don't have access to a plug. There are plans to install public charging stations where people could pay for a recharge with their credit card.
Q: How much power would you need to charge a car versus running, say, a household appliance?
A: A plasma TV consumes almost as much energy as an electric vehicle. Generally, recharging the battery requires plugging in the vehicle for six to eight hours, drawing the maximum current. Now that assumes you drain your battery completely, but I live just 16 kilometres from work and could probably go several days without charging my battery. Options also exist for much faster charging using higher voltages and currents.
Q: What do you like most about working on lithium ion technology?
A: I find the whole concept of lithium ion batteries fascinating, because their efficiency is very high - the amount of energy in and energy out are almost the same. Lithium ion batteries are almost like a perpetual motion machine, losing very little energy per cycle. In satellites, they can run for 20 or 30 years. I love the challenge of trying to make them work better.
