Power density (often given in W/kg for gravimetric power density or W/L for volumetric power density) is a measure of how quickly a battery can deliver energy (power = voltage × current) per unit mass or volume. A battery with high power density can be discharged (or charged) at a high rate without a significant drop in performance. Power density is distinct from energy density: some batteries, like those with thin electrodes or specialized chemistries, are very good at delivering high power but might not store as much total energy as cells with thicker electrodes. High power density is crucial for applications like power tools, electric vehicles (for strong acceleration and fast charging), or grid services (providing quick bursts of energy). Factors that influence power density include the battery’s internal resistance, electrode design (thickness, porosity), electrolyte conductivity, particle size distribution, etc.
NOVONIX evaluates power density by conducting charge and discharge rate mapping tests. They measure how much the voltage drops at various discharge rates and how much capacity can be delivered when discharging in, say, 10 minutes vs 1 hour. NOVONIX’s data helps identify internal bottlenecks: if a certain cell can’t deliver high power, is it due to cathode or anode electrode design limitations, or active material properties, or electrolyte, or? They might then tweak electrode formulations like adding more conductive additive, or making electrodes thinner, and see how power improves. For clients aiming for fast-charge capability, NOVONIX will also test how quickly the cell can be charged (which is essentially the power input side). Using techniques like hybrid pulse power characterization (HPPC), they derive metrics like resistance and power at various states of charge. NOVONIX also ensures that when they boost power, they monitor the impact on other aspects, like temperature rise and cycle life. Through these analyses, they guide how to design cells and choose materials for optimal power density. Ultimately, NOVONIX’s work on power density helps tailor batteries to high-power applications without unnecessarily sacrificing energy content.
