Porosity in battery electrodes refers to the fraction of the electrode’s volume that is empty space (pores) as opposed to solid material. When electrodes are made (coating active material, binder, etc., onto a foil), there are tiny gaps and channels between particles. This porosity is crucial because it allows liquid electrolyte to fill those gaps and provide pathways for lithium ions to move to and from the active material particles. The level of porosity is a balance: higher porosity means more electrolyte storage and easier ion transport (good for power capability), but also means lower volumetric energy density (because less active material per volume). Too low porosity could lead to poor wetting (electrolyte might not reach all areas) and ion transport limitations because of the tortuosity of the channels; too high porosity might cause insufficient inter-particle electrical contact.
NOVONIX studies and optimizes electrode porosity as part of electrode design. NOVONIX will adjust calendering (rolling) pressure to set the desired porosity: for example, an electrode might initially have 40% porosity after coating and drying, then be calendered down to 30%. They then test how that affects performance: more calendering (lower porosity) increases energy density but might hurt fast charging performance, so they find the sweet spot depending on the cell target performance metrics. Through such work, NOVONIX guides how to engineer the electrode’s porosity to get the best mix of energy, power, and lifetime for a given application.
