Batteries might seem like they come in every shape and size that we can imagine.
But as electronic devices become tinier and skinnier without reducing their power and energy demands, they challenge engineers to design batteries that can fit into smaller and smaller spaces without compromising on performance.
For small sensors, we need to re-design the battery, this is can be done by 3-D.We can use Semiconductor processing and a conformal electrolyte to make one that is compatible with the demands of small internet-connected devices.
2-D batteries are limited in shape.The basic battery takes a slice of anode and a slice of cathode and packs an ion-conducting electrolyte between the two to complete the circuit. On the other hand, there are in principle innumerable ways to craft a 3D anode and a 3D cathode that snap together like puzzle pieces.
The setup chosen by Researcher’s group is called a “concentric-tube” design, where an array of evenly spaced anode posts are covered uniformly by a thin layer of a photo-patternable polymer electrolyte and the region between the posts is filled with the cathode material.
Many researchers have succeeded in developing half of 3D battery, creating anodes and cathodes that are stable on their own, but fail when trying to assemble these electrodes into one functional battery.
This is not more efficient than 2D battery. This can be overcome by taking methods normally used to make semiconductors and modifying them to carve silicon into a grid of precisely-spaced cylinders that they wanted for the anode.
To complete the battery, they applied thin layers of electrolyte to the silicon structure and poured in a standard lithium-ion cathode material, using the anode as a mold to ensure that the two halves would fit together just right.
The resulting battery achieved an energy density of 5.2 milli-watt-hours per square centimeter, among the highest reported for a 3D battery, while occupying a miniscule 0.09 square centimeter footprint and withstanding 100 cycles of charging and discharging.