Multi-walled carbon nanotube-coated spiral coils for loss reduction in wireless power transfer systems

Abstract Realization of high efficiency and long transmission range in high-frequency wireless power transfer (WPT) systems has always been hindered by the increased resistance due to the eddy current loss occurring in the inductive coils. In this study, multi-walled carbon nanotube-coated copper (MWCNT-Cu) coils are successfully introduced to address this limitation by implementing the frequency-inert MWCNT channels along with using their high-surface areas to realize the electromagnetic shielding of the Cu substrate through multiple reflection mechanisms. At a frequency of 15 MHz, the resistance of the individual MWCNT-Cu coil was reduced to less than 40% of its original value for primitive Cu, leading to more than a four-fold increase in their quality factor. When MWCNT-Cu coils were used as the transmitting component, the transmission efficiency of the WPT system increased from 10.57% to 95.81% at a transmission distance of 4 cm and a frequency of 3.45 MHz. Finally, it was demonstrated that the loss reduction improved as the eddy current loss became more severe in coils with higher inductance values, which makes this approach promising for significantly improving the performance of inductive components in WPT applications.