Scientists have spent a lot of time trying to lengthen battery life, but safety and thickness matter, too. Just ask Boeing about that first problem -- its 787 Dreamliner was grounded for months thanks to battery fires. However, a group of University of Michigan researchers may have found a way to make lithium-ion energy packs that are safer and slimmer at the same time. The team has developed Kevlar-based, nano-sized membranes that insulate the electrodes in a battery while still allowing lithium ions to pass through and create a proper circuit. The extra-thin layers should not only reduce the chances of short circuiting, but allow for more energy in a given space. You could get away with thinner batteries in smartwatches and other devices without giving up battery life... or worrying that your device will spontaneously combust, for that matter.