The 21700 battery represents the latest in cutting-edge lithium-ion batteries. Popularized by Tesla — manufacturers like Samsung, LG, Sanyo, and Panasonic are following suit and will increase production of their own li-ion 21700 cells in the near future.
The 21700 battery is a new lithium-ion cylindrical cell size format. The increased size (21 mm by 70mm) offers increased energy density over the common 18650 battery. Furthermore, a 21700 battery pack requires fewer cells, making 21700 packs safer and more reliable.
Other new high-density cylindrical cells include the 20650 battery and the 20700 battery. Browse a full list of other sizes.