AN ODE, FOR a moment, to the anode, for it is so frequently overlooked. When a battery is powered up, lithium ions rush toward this positively-charged end and ensconce themselves there until the energy is needed. Originally, anodes were made from lithium metal. But lithium metal is unstable, and liable to explode in contact with air or water, so scientists tried out carbon instead. Over the years, they refined it into a material composed of hexagonal atomic rings—a lattice that could hold an abundance of ions, without the explodey-ness. That material is graphite, the same stuff found in the tip of a No. 2 pencil. It is often said that the cathode—that’s the other end of the battery—is where the magic happens. It’s home to an arrangement of metals like cobalt, nickel, and manganese. But each of those metals is negotiable, depending on the specific battery design. Humble graphite isn’t. It helps define how much energy a battery can hold, and how fast it charges up.
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