Lithium ion batteries are great.  They've taken us miles beyond traditional non-rechargeable batteries. But, and you might have heard about this, they sometimes explode.  They're also reaching the limit of their capacity per kilogram.  One hundred fifty watt-hours per kilogram is a great number for a Li-Ion battery, but in the tech world, everything needs to double every few years, and if we're not going to do it with Li-ion batteries, we need to find something new.

And thin film batteries are certainly something new.  The batteries are actually composed of flat layers of pure lithium electrodes and an electrolyte bonded to a glassy surface.  The batteries never lose charge, can withstand extremes of heat and cold, can charge quickly and discharge slowly or quickly an infinite number of times, can pack a ton of power into a small space, and will not explode in your lap if you dent them.

Increasing the power to kilogram ratio is extremely important, not just in mobile computing, but also for electric driving, where the weight of batteries is a huge problem.  Lighter electric batteries means less electricity is needed to power the car, and so the car can go further, faster, and weigh less. 

Thin film batteries are, of course, currently far to expensive for retail.  But if Silicon Valley has taught us anything, it's that a technology in demand never stays expensive for too long.