Table 1. Comparison Table of Supercapacitors, Conventional Capacitors, Metal-Ion Batteries, Metal-Ion Capacitors, and Redox Flow Batteries3−6.
| supercapacitor | capacitor | Li-ion battery | Li-ion capacitor | redox flow batteries | |
|---|---|---|---|---|---|
| storage mechanism | physical | physical | chemical | chemical and physical | chemical |
| operating voltage (V) | 1.0–3.2 | 4–630 | 2.5–4.3 | 2.2–3.8 | 1.0–2.1 |
| energy density (Wh/kg) | 2.5–15 | <0.1 | 75–250 | 10–100 | <10–70 |
| power density (W/kg) | 500–10000 | >1000000 | 150–315 | 300–5000 | 10–100 |
| cycle life | >105 | >106 | 103–104 | 104–106 | >103 |
| operating temperature (°C) | from −40 to 70 | from −20 to 100 | from −20 to 60 | from −25 to 85 | from 0 to 60 |
| efficiency (%) | 95 | 99 | 85–90 | 90 | 60–85 |
| self-discharge | very high | very high | very low | low | low |
| safety | good | good | needs improvement | good | low |
| voltage monitoring | not required | not required | needed | needed |