You may not give a lot of thought to what happens inside the battery of your laptop or cell phone, but to judge from the video above, it's not a dull place. The battery in question is a miniature rechargeable lithium-ion device, and the clip shows what happens when it is charged. As lithium ions flow from the positively charged cathode into the 200-nanometre diameter wires of tin oxide that make up the negatively charged anode, the nanowires writhe and bulge, causing them to expand up to 2.5 fold. The wires also change structure from a neatly ordered crystal to a disordered glassy material. These distortions may explain why such batteries ultimately wear down, the team reports  online today in Science. Knowing more about the process may help researchers develop longer lasting, and perhaps much smaller, batteries in the future.
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