China-UK joint research team develops high-performance wireless EV charging system

A joint research team from China and the UK has developed a 20 kW-class wireless charging system designed for new energy vehicles, overcoming critical heat and efficiency barriers in inductive power transfer. The 20-kilowatt wireless charging system achieved an unprecedented 98.51% efficiency. The research was led by the Dongguan Institute of Materials Science and Technology under the Chinese Academy of Sciences (CAS), in collaboration with the Institute of Physics of the Chinese Academy of Sciences, City University of Hong Kong, and the University of Cambridge.

Charging challenges for self-driving vehicles

While self-driving electric vehicles can navigate complex roads, their autonomy is limited when they require manual plug-in charging. This reliance on humans poses a significant challenge for fully automated transportation. Therefore, the newly developed automatic wireless charging technology aims to eliminate this limitation, enabling autonomous fleets to operate and recharge without human intervention.

Conventional wireless charging pads primarily use heavy ferrite cores to guide magnetic fields. While ferrite performs well at low power, the material suffers from overheating, efficiency loss, and limited power density when power is scaled up for fast vehicle charging. Researchers addressed this by using stress-annealed iron-based nanocrystalline alloy and a co-design of materials and systems. The team stated: "We report an inductive charging system utilizing iron-based nanocrystalline alloy, co-developed through material- and system-level optimization."

Engineers made a counterintuitive design choice, selecting moderate permeability rather than the maximum to balance system performance. This strategy yielded a compact magnetic core strip measuring 440 mm x 330 mm with a thickness of just 4 mm. The resulting material achieves half the high power density handling performance of standard ferrite plates.

Researchers applied a specialized stress-annealing process combined with coil-aligned lamination to optimize the core structure. These techniques successfully reduced core energy loss to 135 kW/m³ under test conditions of 85 kHz and 0.2 T. According to the study, the system delivers 98.51% AC-to-AC conversion efficiency in its coils and core, with a volumetric power density of 9.55 kW/L. It also maintains reliable thermal stability during high-power operating cycles. The study noted: "Integrated material and electrical design advances inductive charging systems supporting autonomous vehicles and electric mobility."

Commercialization potential of the technology

Autonomous driving requires autonomous refueling. Without hands-free charging, fully automated robotaxi fleets remain a distant vision. This technology is designed for China's ambitious Five-Year Plan (2026-2030), which targets widespread commercialization of autonomous driving on major urban highways and expressways by 2030. Passenger cars are just the beginning. The Dongguan Institute of Materials Science and Technology has moved the prototype toward commercial production. Beyond passenger EVs, the technology targets industrial automated guided vehicles (AGVs) in factories, heavy rail transit, and even low-altitude electric aircraft.

With faster speeds, a thinner profile, and lower operating temperatures, the China-UK joint team has paved the way for a world where machines can seamlessly recharge themselves in the background. The research was recently published in the journal Nature Communications.