Coin Cells are one of the many different battery cell formats.
Coin Cells or Button Cells are mostly used in primary cells and available in a wide range of sizes for hearing aids, card readers and calculators.
In the chemistry research world coin cells are used for early testing of chemistry as they are small and simple to make in the lab. Therefore, it is possible to make and electrically test a large number of cells prior to moving to a larger format.
One of the fundamental steps in proving new chemistry is making small cells that can be reliably charged and discharged. These small cells are assembled in argon filled gloveboxes. They are small and very fiddly to assemble. However, they need to be precisely built to reduce variation in data caused from physical mis-alignment of electrodes which can drown-out signals of small but important improvements in cell chemistry.