Nanodiamond Electrodes Used in Supercapacitors Increase Energy Storage Capacity

The steadily increasing use of battery-operated appliances and devices has led to the need for efficient, safe, and high-performing power sources. Therefore, a type of electrical energy storage device known as the supercapacitor has now been regarded as a viable alternative to traditional, extensively used energy-storage devices such as Li-ion batteries.

In a breakthrough study, scientists from Japan use nanodiamonds to construct supercapacitors that can be widely used as a more efficient alternative to conventional energy-storage devices. Image Credit: Tokyo University of Science.

Supercapacitors can charge and discharge a lot more quickly than traditional batteries and also continue to perform in the same manner for a longer time. This renders them ideal for a variety of applications such as wearable electronic devices, regenerative braking in vehicles, and so on.

If a high-performance supercapacitor using a non-flammable, non-toxic, and safe aqueous electrolyte can be created, it can be incorporated into wearable devices and other devices, contributing to a boom in the Internet of Things.

Dr Takeshi Kondo, Study Lead, Tokyo University of Science

However, in spite of their potential, supercapacitors, currently, have some disadvantages that have hampered their extensive use. One key problem is that they possess low energy density; that is, they store inadequate energy per unit area of their space.

Researchers first tried to overcome this obstacle by using organic solvents as the electrolyte—the conducting medium—within supercapacitors to increase the produced voltage (it must be noted that the square of the voltage is directly proportional to energy density in energy storage devices). However, organic solvents are expensive and have low conductivity. Therefore, an aqueous electrolyte would perhaps be better, the researchers noted.

Therefore, the creation of supercapacitor components that would be effective with aqueous electrolytes became a core research topic in the domain.

In the above-mentioned latest study, published in Scientific Reports, Dr Kondo and team from the Tokyo University of Science and Daicel Corporation in Japan investigated the possibility of using a unique material, the boron-doped nanodiamond, as electrode in the supercapacitors—electrodes are the conducting materials in a capacitor or battery that link the electrolyte with external wires, to convey current out of the system.

The research team chose this electrode material based on the know-how that boron-doped diamonds have an extensive potential window, a feature that allows a high-energy storage device to stay steady over time.

We thought that water-based supercapacitors producing a large voltage could be realized if conductive diamond is used as an electrode material.

Dr Takeshi Kondo, Study Lead, Tokyo University of Science

The researchers made these electrodes using a method known as the microwave plasma-assisted chemical vapor deposition (MPCVD) and analyzed their performance by testing their properties. They learned that in a standard two-electrode system with an aqueous sulfuric acid electrolyte, these electrodes generated a considerably higher voltage than traditional cells, producing much higher power densities and energy for the supercapacitor.

Moreover, they witnessed that even after 10,000 cycles of charging and discharging, the electrode was highly stable. The boron-doped nanodiamond had been found to be reliable.

Based on this success, the researchers then attempted to investigate whether this electrode material would produce the same results if the electrolyte were replaced with a saturated sodium perchlorate solution, which is said to facilitate the production of a higher voltage than what is feasible with traditional sulfuric acid electrolyte. Undeniably, the already high voltage produced expanded significantly in this arrangement.

The boron-doped nanodiamond electrodes are useful for aqueous supercapacitors, which function as high-energy storage devices suitable for high-speed charging and discharging.

Dr Takeshi Kondo, Study Lead, Tokyo University of Science

The electronic and physical world around humans could soon be driven by diamonds.


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