94 pages ; This work presents a capacitive wireless power transfer (WPT) system for electric vehicle charging that achieves high efficiency and record-breaking power transfer density. This high performance is enabled by multi-MHz operation, innovatively designed matching networks, enhancements in the design of the capacitive coupling plates, and use of new interleaved-foil air-core coupled inductors. A multi-module system is shown to reduce fringing-fields, and the impact of foreign objects is also investigated. The capacitive WPT system utilizes two pairs of metal plates separated by an air-gap as the capacitive coupler, and incorporates L-section matching networks to provide gain and reactive compensation. High efficiency and simplicity is achieved by eliminating the need for high-voltage capacitors, and instead the parasitic capacitances formed between the coupling plates and the vehicle chassis and roadway are utilized as part of the matching networks. A comprehensive design methodology for a capacitive WPT system is presented that guarantees high performance by ensuring zero-voltage switching of the inverter transistors, and by selecting matching network component values to maximize efficiency. Coupling plate enhancements include the use of circular plates enveloped in a high-breakdown-strength dielectric material to alleviate arcing, allowing kilowatt-scale power transfer across a large air-gap. New toroidal interleaved-foil (TIF) inductors provide a better tradeoff between quality factor, size and self-resonant frequency compared to conventional solenoidal inductors, making them suitable for compactly and efficiently processing kilowatt-scale power at multi-MHz frequencies. A 13.56-MHz, 12-cm air-gap prototype capacitive WPT system utilizing TIF inductors with a quality factor of 2055 in its matching networks is designed, built and tested. This system achieves record-breaking performance for a capacitive EV charging system, transferring 3.75 kW with an efficiency of 94.7%, corresponding to a power ...