At their core, all batteries are the same as ions move between electrodes, storing energy in bonds. Of course the exact mechanics of this process differs between battery types, and to design the best batteries, one must understand those mechanics. This is not a simple task with lithium ion batteries though, as lithium atoms are so small, but researchers at Michigan Technological University have successfully observed those atoms within a battery.
Lithium is the third lightest element, so watching it move through a system requires a special tool; an aberration corrected scanning transmission electron microscope (AC-STEM). Using one at the University of Illinois at Chicago, the researchers watched lithium ions in a nano-battery enter a tin oxide electrode. Modern lithium-ion batteries use graphite for their electrodes, but different electrodes allow for faster charging and discharging, as well as greater energy storage. Tin oxide has potential as a replacement for graphite electrodes, but requires further study. In this study the researchers found that lithium ions enter the electrode via specific paths, and did not simply enter the electrode randomly.
Over time the motion of ions in to and out of electrodes stresses them to the point of failure, which is why this kind of research is critical. It allows for the amount of strain on the electrode to be calculated, which many other laboratories are interested in as well.