# Application of the Supercapacitor for Energy Storage in China: Role and Strategy
## 2 Technology Characterization
### Comparison  
Electrochemical supercapacitors can be divided into the double-layer capacitor, Faraday pseudocapacitor and hybrid supercapacitor. The Faraday pseudocapacitor has a relatively high energy density due to its unique structure. In the same electrode area, the capacity of the pseudocapacitor is 10 or 100 times that of the common double-layer capacitors. Some of its properties are improved but not prominently, and the others are close to those of the double-layer capacitors. Compared with symmetry double-layer capacitors with carbon electrodes, the hybrid supercapacitor has higher operation voltage and energy density, 2 to 3 times capacitance, and can offer a higher power density, which is suitable to offer a large pulse. Table 2 compares the advantages and disadvantages of the three supercapacitors. Generally, double-layer capacitors and pseudocapacitors with a short charging time and high efficiency are well suited to act as rechargeable stand-alone power sources. Although hybrid supercapacitors take longer to charge, their cycle life is shorter and more prone to leakage, so they are not as widely used as pseudocapacitors and double-layer capacitors [19]. Figure 3 visualizes the differences among the three types of supercapacitors. Electric double layer capacitor (EDLC) is one of the most mature technology, and its market share is the highest, but because of its limitation of material and structure, the energy density of EDLC is not high. In contrast, the energy density of the hybrid supercapacitors have an advantage in charging time, cycle life and power density. Pseudocapacitance in all aspects of performances between the above two. In order to balance the dual goals of massive power demand and carbon neutrality achieved by 2060, it uses abundant natural clean energy (such as wind power generation, and photovoltaic power generation) and the current grid to form a multi-energy complementary system, which can effectively reduce carbon emissions. However, the power generation stability of clean energy, such as wind power and solar power is poor, and the integration of new energy into the power grid will have a significant impact on the current power grid. The hybrid capacitor can play the role of frequency regulation and peak regulation in this multi-energy complementary system and enhance the stability of the power grid.  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Types of Supercapacitors** & & **Advantages** & **Disadvantages** \\ \hline \multirow{6}{*}{Double layer supercapacitor} & 1. & The operating temperature range is & \\  & wide from \(-40\)\({}^{\circ}\)C to \(+70\)\({}^{\circ}\)C & \\  & 2. & Small temperature change & 1. & Low voltage \\  & 3. & High power density & 2. & High cost \\  & 4. & High safety & 3. & High self-discharge \\  & 5. & High reliability and long life & \\  & 6. & Commercialized & \\ \hline \multirow{2}{*}{Faraday pseudocapacitor} & 1. & High energy density & 1. & Low power density \\  & 1. & High energy density & 2. & Low voltage \\  & & & 3. & High cost \\ \hline \multirow{3}{*}{Hybrid supercapacitor} & 1. & Wide operating temperature range & 1. & Industrialization in progress \\  & 2. & High power density & 2. & Temperature variation \\  & 3. & High safety & 3. & Low power density \\ \hline \hline \end{tabular}
\end{table}
Table 2: Advantages and disadvantages of the three kinds of supercapacitors.