Diamond Supercabatteries with High Power Densities and Energy Densities

• Applicant: Professor Dr.-Ing. Nianjun Yang, Ph.D.
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 457444676

Supercapacitors and batteries are two kinds of important electrochemical energy storage devices. Supercapacitors feature high power densities but low energy densities, while batteries exhibit high energy densities but low power densities. To overcome the challenges for both supercapacitors and batteries, we propose in this project the design and fabrication of “supercabatteries”, a compound of supercapacitors and batteries, which are constructed with diamond capacitor electrodes and redox electrolytes. By means of the microwave plasma enhanced chemical vapor deposition technique, two kinds of diamond capacitor electrodes will be synthesized: diamond cloths and diamond networks. Diamond cloths will be grown via the overgrowth of the templates of carbon cloths with thin boron-doped diamond layers. Diamond networks will be fabricated through wet-chemical etching of cubic silicon carbide from the diamond/SiC composite films. The thicknesses of coated BDD layers on diamond cloths and the porosities of diamond networks will be varied. The quality of as-grown diamond layers, electrochemical and mechanical features of diamond capacitor electrodes will then be characterized with microscopic, spectroscopic, electrochemical and related techniques. The effect of the used carbon cloths, the thicknesses of over-grown diamond layers and the porosities of diamond networks on the mechanical properties of these diamond capacitor electrodes will be clarified. Cyclic voltammetry, the galvanostatic charge/discharge method, and electrochemical impedance spectroscopy will be employed to investigate the performance of as-fabricated diamond supercabatteries, including their capacitances, capacitance retention, power densities and energy densities. The effect of the mechanical properties of diamond capacitor electrodes and the used redox electrolytes (e.g., type, amount) on the performance of diamond supercabatteries will be examined. To verify practical applications of diamond supercabatteries, stand-alone demonstrators will be constructed to, e. g., run timers and/or light LEDs. These diamond capacitor electrodes will be free-standing, binder-free and flexible in some cases. More importantly, they will feature low densities, wide potential windows, high surface areas, high thermal conductivities, and good mechanical stability. Together with the involvement of faradaic processes of redox electrolytes, these diamond supercabatteries are expected to yield high performances, namely by much enhanced capacitances, outstanding capacitance retention, high power densities and energy densities. They might be operational at high temperatures. Consequently, they will be superior to most of the currently available solutions. They are thus promising energy storage devices for medical, military and civil applications.

• DFG Programme: Research Grants