Carbon-Based Nanocomposite Materials for High-Performance Supercapacitors

*Prasanta Kumar Sahoo, Chi-Ang Tseng, Yi-June Huang and Chuan-Pei Lee*

## **Abstract**

Lightweight, flexible, wearable, and portable electronic gadgets have drawn significant attention in modern electronics industry. To power these gadgets, great efforts have been made to develop highly efficient energy-storage equipment. Among various power sources, a supercapacitor, acting as a bridge between the conventional battery and electrolytic capacitor, has been considered a promising portable energy storage device because of its high power density, fast charge/ discharge rate, adequate operational safety, and excellent working lifetime. Hybrid supercapacitors, which combine redox materials with carbon-based materials, exhibit tremendous potential to fulfill the requirement of practical applications. In this chapter, we will review recent reports focusing on composite materials (*i.e.* metal oxide, metal hydroxide, and metal dichalcogenide composited with carbon materials) for the application in supercapacitors. The conclusion and futuristic prospects and challenges of highly efficient supercapacitors are briefly discussed.

**Keywords:** energy storage, composites, metal oxides, metal hydroxides, transition metal dichalcogenides, supercapacitor

#### **1. Introduction**

There is sharply increasing demand for energy with the rapid growth of the global economy. The energy generation from sustainable sources, such as wind and solar, plays an important role in power supply. However, the intermittent nature and imbalanced regional distribution of the sustainable energy make them unable to stably supply the power [1]. The development of energy storage systems is an urgent requirement to meet the sufficient and stable power supply for industrial and residential usage. Although rechargeable lithium-ion batteries, dominant energy sources in each field, as high energy density providers have filled their position [2], lithium-ion batteries still have the limitations of poor cycle life and low power performance [3]. Supercapacitors (SCs), also known as ultracapacitor and electrochemical capacitors, are an emerging class of energy storage device, which possess high power density and tens of thousands of charge/discharge cycles [4, 5]. **Figure 1** shows the Ragone plot of different energy conversion and storage devices. SCs have a unique position to bridge the gap between conventional capacitors and batteries. Compared with conventional capacitor, SCs possess higher specific energy density

**Figure 1.** *Ragone plot for various energy storage and conversion devices [6].*

in several orders of magnitude. Moreover, SCs provide higher specific power density than batteries due to its unique charge storage mechanism.
