Like lithium-air batteries, other potential high-energy battery technologies face a number of hurdles, which could help explain why hybrids with their high-power rather than high-energy batteries have been more successful than electric vehicles. Many of the most promising battery chemistries are too difficult to make at a large scale, fall apart after a few cycles, or are too expensive. According to the U.S. Department of Energy, complete battery packs today cost between $800 and $1,200 a kilowatt hour, and store about 100 to 120 watt-hours per kilogram. To make electric vehicles practical and affordable, the DOE would like to see costs drop to $250 per kilowatt hour and increase storage capacity to over 200 watt-hours per kilogram. (Reaching these goals will require even higher storage capacities for the individual battery cells that make up battery packs–about 400 watt hours per kilogram.)
While improving batteries for hybrids and electric vehicles is difficult, one of the biggest long-term challenges for battery researchers is making batteries that can cheaply store vast amounts of energy generated by solar panels and wind turbines, so that electricity from these sources is available when the sun isn’t shining or the wind isn’t blowing. For now, such batteries aren’t needed–there’s enough power from conventional sources to take up the slack. But if solar and wind are ever to provide the majority of electricity, storage will be needed, and batteries today are far too expensive. The DOE goal for such batteries is less than $100 per kilowatt-hour, less than half its goal for electric vehicles. It’s cheaper today to build a natural gas power plant as a backup source of power, or to store energy by pumping water uphill, where it can later flow downhill to spin a generator. One experimental approach to such low-cost batteries is something called a “liquid” battery, which uses inexpensive battery materials that assemble themselves.
Even if problems with batteries are overcome in the lab, these technologies face obstacles to being commercialized. To drive down costs, battery makers are turning to applications other than electric vehicles and the grid to get new technologies off the ground, applications such as microelectronics, power tools, and race cars. Plug-in hybrids can also help serve as a bridge to electric vehicles. Plug-ins use back-up gas-powered generators to help extend their range, allowing automakers to use smaller, less expensive battery packs than they’d need for electric vehicles. Automakers such as GM, with its Chevrolet Volt due out this year, are taking this approach. The electric vehicles on sale now, and that will be going on sale in the next few years, are either expensive sports cars and luxury vehicles, where costs can be high, or their upfront costs are being decreased using creative financing, such as leasing battery packs or offering per-mile plans something like the per-minute plans offered by cell phone companies.