High-temperature capacitor for electric vehicles

Scientists at the National Physical Laboratory are helping to create electronics capabilities for electric vehicles, with the development of a high-temperature capacitor.

Electric vehicles (EV) are hoped to represent more than 50% of worldwide light-duty vehicle sales by 2050. The absence of suitable capacitors is one of the major barriers to meeting this goal. Capacitors are a means of storing energy and are vital to the process of converting DC power from the vehicle battery into AC power required to drive the motor. Current capacitors do not meet the EV requirements, due to an inability to function reliably under the high temperatures created in electric vehicles.

NPL has overcome this issue, as part of a Technology Strategy Board funded project. The outcome is a capacitor - called HITECA - that can operate close to normal efficiency at over 200°C, significantly higher than any other capacitor on the market. It also offers a high energy density - the measure of how much energy it can store.

The upshot for the electrical vehicle driver could mean an increased mileage range, reduced maintenance and an enhanced driving feel.

To develop the capacitor, NPL investigated a range of lead-free materials that could have the desired properties to develop into a high-temperature capacitor. The scientists explored different compositions and different ways of fabricating them. They measured current at a range of high temperatures using advanced measurement techniques. The most promising materials were optimised to achieve the desired properties. The resulting capacitor is created from a ceramic, based on doped-BiFeO3 compound.

Tatiana Correia, lead scientist on the project, said: “The opportunities for electric vehicles are huge, both financially and environmentally, but they are currently being held back by a few technical issues. With this high-temperature capacitor, we believe we have solved an important one of those issues and will play a vital part in the move towards mass market electric vehicles.”

A recent Frost & Sullivan Report shows that capacitors represent a £10bn global market in the automotive industry alone. This capacitor also has huge potential in other areas of high-temperature electronics for other industries, for example: pulsed power applications (defibrillators and X-ray generators), energy conversion in photovoltaic and integrated circuits, downhole power electronics in the oil and gas industry, which need to work at high temperatures or are subject to overheating.

The project has also allowed NPL to develop a range of new capabilities in metrology to assess energy and power in capacitors across a temperature range, which it will be offering as a new service.

The capacitor was developed as part of the Technology Strategy Board Project, Advanced Capacitors for Energy Storage (ACES). NPL is interested in hearing from industrial partners interested in licensing the innovation.