Tap density is a measure of how densely a powder (like an active material powder for a battery electrode) can pack together under the influence of tapping or vibration. It’s determined by filling a graduated cylinder with a powder, noting the powder weight, then mechanically tapping it a fixed number of times using a standardized machine and measuring the final volume. The mass divided by this tapped volume gives the tap density (usually in g/cm³). Tap density is an important parameter for battery materials because it affects how dense the electrode can be made: higher tap density material -> potentially higher energy density electrode since you can pack more active material in a given volume. For example, synthetic graphite often has higher tap density than some flaky natural graphite, which can be an advantage in achieving higher anode density. In cathodes, manufacturers strive to increase tap density via particle engineering, like making secondary particles.
NOVONIX, when working on materials like their synthetic graphite or cathode from their all dry, zero waste pilot facility, will measure tap density as part of its characterization. They correlate it with electrode properties and cell performance. With customer materials By understanding and utilizing tap density, NOVONIX helps optimize how powders translate into electrode quality and ultimately battery performance, especially where energy density is critical.
