3D printing can be used to manufacture porous electrodes for lithium-ion batteries — but because of the nature of the manufacturing process, the design of these 3D printed electrodes is limited to just a few possible architectures. Until now, the internal geometry that produced the best porous electrodes through additive manufacturing was what’s known as an interdigitated geometry — metal prongs interlocked like the fingers of two clasped hands, with the lithium shuttling between the two sides.