The Ragone Plot shows Power Density vs Energy Density for an energy storage device. Originally introduced by D. Ragone in 1968 [2] it has been rather misused and hence the review by Beyers et al [1] is a useful starting point.
Beyers et al [1] definition: a Ragone plot should have an energy axis and a power axis or derived specific quantities of the two. “Proxies” for the energy axis, such as discharge time and efficiency, should not be labelled as Ragone plots. Practical Ragone curves should comprise multiple E-P value pairs, each obtained by separate, full charge/discharge processes, to predetermined upper/lower operating limits. The authors recommend a constant power test.
A comparison of three Samsung cells using the Ragone Plot [3].
Here we can see turning points in each of the curves at high discharge rates.
We can see how misleading it would be to plot maximum maximum continuous discharge rate vs maximum energy density.
Li and Yazami [3] show the Reverse Ragone Plot where energy density is plotted vs charge power density.
This plot shows the improvement using the Non-Linear Voltammetry charging method.
The Ragone Plot is useful when comparing different battery chemistries.
It should be noted that this is specification based and as such not a true representation of power versus energy.
References
- Inga Beyers, Astrid Bensmann, Richard Hanke-Rauschenbach, Ragone plots revisited: A review of methodology and application across energy storage technologies, Journal of Energy Storage, Volume 73, Part D, 2023
- Ragone, D., “Review of Battery Systems for Electrically Powered Vehicles,” SAE Technical Paper 680453, 1968
- Li, Shiqi and Yazami, Rachid, Reverse Ragone vs. Direct Ragone plots: a comparative study for ultra-fast charging lithium-ion batteries, EES Batteries, 2025
See also: Pareto Frontier of the Ragone Plot, Battery Pack Ragone Plot