The Li-ion awakens

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especially if a battery is damaged or assembled wrongly in a way that causes an internal short-circuit. Such an overheating cell can ignite, causing its neighbours to catch fire in a ‘thermal runaway’—as happened to the faulty batches in 2006. To stop that occurring, and also to enhance performance, new electrode materials are being tried out. The most promising are phosphates of manganese and iron—made more promising still by being manufactured as particles whose dimensions are measured in nanometres (billionths of a metre). Making an electrode out of such nanoparticles increases its surface area. That, in turn, decreases the battery’s internal resistance and improves its ability to store and deliver energy.

One of the leaders in this field is A123 Systems of Watertown, Massachusetts. The phosphate particles in its electrodes are less than 100 nanometres across—about a hundredth of the size of the oxide particles used in existing Li-ion batteries. The new generation of Li-ion batteries are hardy enough for A123 Systems to make batteries for DeWalt, a supplier of industrial power tools. DeWalt is now confident enough in the ability of Li-ion batteries to withstand the rigours of construction sites that it recently began offering them as an option for its cordless hammerdrills and other heavy-duty machines. A123 Systems is now developing a Li-ion system for the Chevvy Volt, an electric car planned by General Motors.

The prize for machismo in this area, however, goes to Saft, a French firm. In November it unveiled a Li-ion cell capable of withstanding extreme vibration, high pressure and temperatures of up to 125°C. This will be used to power the measuring equipment incorporated into drill heads used by the oil and gas industry. If Li-ion can withstand that sort of punishment, electric cars should be a breeze.