Rapid Preparation of All-In-One Compressible Capacitors with Flame Carbonized Melamine Foam for AC Line Filtering

Abstract

Melamine foam (MF) is a good candidate for electrochemical filter capacitors due to its 3D porous structure, flexibility, and nitrogen-containing property. However, traditional thermal carbonization would cause a severe loss of nitrogen and need several hours to perform the transition from melamine to carbon. Moreover, to construct all-in-one electrochemical capacitors, the nonconductive MF must be deposited a conductive layer on the surface of MFs. Herein, we developed a flame carbonization method to carbonize the MFs to an all-in-one structure in less than one minute. The carbonized MF exhibits 2.6 times higher nitrogen content than that of the traditional carbonized. MF-based all-in-one compressible electrochemical capacitors deliver excellent alternating current (AC) line filtering performance, such as a low phase angle of −83.1° at 120 Hz, a low resistance capacitance time constant of 157 μs, and a short relaxation time constant of 46 μs. The AC signal of 120 Hz, even a higher frequency of 2000 Hz, can be successfully converted into a stable direct current (DC) signal. Besides, the influence of electrolyte, compressive strain, and the thickness/carbonization time of MFs on the electrochemical performance has been studied. This work provides an ingenious design and effective preparation strategy for MFs-based all-in-one electrochemical capacitors.