Challenges related to BEVs include limited driving range, high costs, battery issues, long charging time, and inadequate charging infrastructure. Also, with vehicle electrification there are issues with various power semiconductors and other devices.
Limited driving range and battery issues. Charging is a crucial topic for the success of vehicle electrification. The top technical challenge is that the energy density of lithium-ion batteries can provide a limited driving range of 400 to 500 km (249 to 311 miles), while consumers prefer a driving range of 700 km (435 miles) or more. Also, the design of a battery pack is limited by the size and mass of the pack. More battery cells mean more mass for the vehicle. Increased mass requires more energy for vehicle movement, and also affects vehicle maneuverability such as handling, acceleration, and braking. The greater the mass, the harder it is to achieve good results on those performance metrics. Also, all BEV batteries degrade (become less efficient). Most car manufacturers warrant EV batteries to not degrade below a certain level for around eight years. So, it may become necessary to replace a battery in an EV while the driver owns the vehicle.
Long charging time and inadequate charging infrastructure. With the right mix of infrastructure and charging comfort, EVs could become competitive with vehicles powered by ICE. The big issue is long-distance travel, where charging stations are not always available. Installing more fast-charging stations takes massive investments. However, daily re-charging at home or work or at public or commercial parking areas (retail locations, motorway rest areas, etc.) would mean that drivers never have to stop at filling stations in the future. Charging comfort, in general, would strongly benefit PHEV use by ensuring that they are operated in electric mode in urban areas as much as possible, while minimizing range anxiety during longer trips where the availability of (and access to) suitable charging facilities are uncertain.
Power semiconductors. Power conversion systems are essential and important to modern EVs. A DC-AC inverter system is used to convert DC from the battery and run an AC induction motor. A combination of AC-DC converter and DC-DC converter along with power factor corrector (PFC) is used in charging systems. Other DC-DC converters power other auxiliary electrical systems in a vehicle. A power converter system uses power semiconductor switches such as power MOSFETs and the insulated-gate bipolar transistor (IGBT) to boost the efficiencies and minimize the energy losses in systems. The dominant power semiconductor types are based on silicon. But silicon power MOSFETs are limited in operating voltage up to 250 volts. t IGBTs are powerlifters as they can handle operating voltage from 400 volts to 1600 volts. However, IGBTs are not used in high-frequency operation (>30 kHz) due to poor switching performance. Power MOSFETs with better switching performance are used in frequency >200 kHz. To overcome these limitations, wide-bandgap devices such as SiC and GaN must be used. Wide-bandgap devices can operate in high voltage (> 1200 volts) and high frequency (> 200 kHz) due to the wide energy bandgap. They also operate with less on-state resistance and high thermal conductivity. This improves the efficiency by 2%, which is a great deal in EVs. Since the power density and thermal conductivity are higher for the same power rating, the size of the device and thermal management system (heat sink) is also smaller. With the higher operating frequency, the size of the passive components is also smaller. Size and weight are huge considerations in EVs. SiC diodes are also sometimes recommended for the PFC to make the charger more efficient and reduce the size of the components. But wide-bandgap devices are expensive and not many manufacturers commercially produce them. Therefore, not many EV manufacturers opt for wide-bandgap devices as it is a premium solution.
Other devices. Robustness and reliability of the integrated power devices are key challenges for automotive power IC designs and manufacturing. One of the biggest challenges for EVs and hybrids is how the microcontroller can optimize the power efficiency for different components inside the EV, from high- to low-end designs to ensure long-term design flexibility. Also, on-chip memory solutions need to comply with the AEC-Q100 standard to satisfy the stringent operating temperature specifications. The use of 7nm and 10nm parts create lots of systematic defects and integration challenges that haven’t been debugged yet. These processes still have a lot of maturing to do.