There are two main types of supercapacitors:
- Electrochemical double layer capacitors (EDLCs): EDLCs store energy in the double layer that forms at the interface between the electrode and the electrolyte. EDLCs have high power density and can be charged and discharged quickly, but they have lower energy density than other types of supercapacitors.
- Pseudocapacitors: Pseudocapacitors store energy through reversible redox reactions at the electrode surface. Pseudocapacitors have higher energy density than EDLCs, but they have lower power density and slower charge and discharge times.
EDLCs are typically made with carbon-based electrodes, while pseudocapacitors are typically made with metal oxide or conducting polymer electrodes.
In addition to these two main types, there are also hybrid supercapacitors that combine the characteristics of EDLCs and pseudocapacitors. Hybrid supercapacitors have higher energy density and power density than either EDLCs or pseudocapacitors alone.
The following table summarizes the key differences between EDLCs, pseudocapacitors, and hybrid supercapacitors:
| Type | Energy density | Power density | Charge/discharge time |
|---|---|---|---|
| EDLC | Low | High | Fast |
| Pseudocapacitor | High | Low | Slow |
| Hybrid supercapacitor | Medium | Medium | Medium |
The best type of supercapacitor for a particular application depends on the specific requirements of that application. For example, if an application requires high power density and fast charge and discharge times, then an EDLC would be a good choice. If an application requires high energy density, then a pseudocapacitor or hybrid supercapacitor would be a better choice.
Here are some examples of applications where each type of supercapacitor is typically used:
- EDLCs: Electric vehicles, hybrid vehicles, regenerative braking systems, start-stop systems, power tools, medical devices, wearable devices, IoT devices
- Pseudocapacitors: Energy storage systems for renewable energy sources, grid frequency regulation, industrial automation, robotics, backup power supplies
- Hybrid supercapacitors: Electric buses, electric trains, electric ferries, electric aircraft, microgrids
Supercapacitor technology is still evolving, and new types of supercapacitors are being developed all the time. As the technology continues to develop and costs come down, supercapacitors are expected to be used in even more applications in the future.