It's not just electricitygeneration that will make a difference in the future, it's also energy storage.And that's especially true for mobile devices — whether that means iPhones orespecially, electric cars. Low-capacity batteries have held back electric carsfor decades, but that's beginning to change thanks to a new(ish) technology.The electronics of the 1990s — and most hybrid cars today — used nickel-ion batteriesfor power. They were an upgrade over the lead batteries used in the past, butthey weren't strong enough to power electric cars for long distances.Lithium-ion batteries,however, are a potential game-changer. If you use a laptop or a mobile phone,chances are you already own a lithium-ion battery. (Without them, your iPhonewouldn't even have the less-than-great operating life it does today.)Lithium-ion batteries can pack more power in a smaller case, so the battery forGM's plug-in hybrid Volt is tiny compared to the gigantic power pack that hadbeen used on its EV1. A smaller battery is also lighter, which reduces theweight of the electric car and the power needed to drive it. The price onlithium-ion batteries still needs to come down — a battery for a new electriccar can cost more than $10,000. But battery-making companies like A123 Systemsin Massachusetts are already emerging as the future titans of a clean energyeconomy.