Significant challenges exist in using manganese bismuth (MnBi) magnets in electric vehicles (EVs), primarily related to their magnetic and environmental properties as well as performance metrics compared to traditional rare-earth magnets.
Key Challenges of MnBi Magnets in EV Applications
1. Lower Magnetic Performance Compared to Rare-Earth Magnets
MnBi magnets exhibit much lower maximum energy product and coercivity than the commonly used neodymium iron boron (NdFeB) magnets in EV motors. The coercivity—critical for maintaining magnetization under operational stresses—significantly decreases during manufacturing processes, diminishing their magnetic strength and effectiveness in motor applications. This limits MnBi’s ability to match the torque and power density performance of rare-earth magnets which are highly optimized for EV drivetrains.
2. Susceptibility to Environmental Degradation
MnBi magnets are open to environmental exposure, making them prone to property degradation. This sensitivity causes issues with the stability of their magnetic properties during use, which is a concern for automotive environments that include temperature fluctuations and moisture. Stability and reliability over the vehicle’s lifetime are critical considerations unmet by MnBi magnets so far.
3. Temperature-Dependent Performance and Demagnetization Risks
EV motors operate across a wide range of temperatures, including below-freezing conditions. MnBi magnets face risks of irreversible demagnetization with temperature changes. Understanding and mitigating these effects is crucial because inconsistent magnetization can reduce motor efficiency and reliability. This is especially important since EV motors must sustain performance under harsh temperature variations.
4. Lack of Suitable Motor Designs Using MnBi
To date, there are very few practical motor designs employing MnBi magnets that meet the speed, power, and torque requirements for commercial EV applications. Existing research shows that previously designed MnBi motor topologies do not provide suitable power density or performance comparable to rare-earth motors, making them less viable for current EV drivetrain standards.
Summary
While manganese bismuth magnets offer a rare-earth-free alternative—a crucial advantage given the cost and supply risks of rare-earth elements—they currently face significant challenges for EV use:
- Reduced coercivity and energy product after manufacturing processes limits their magnetic strength.
- Environmental sensitivity can degrade magnetic properties during vehicle operation.
- Temperature-induced demagnetization risks threaten stable motor performance.
- Suitable, high-performance MnBi motor designs for EVs remain undeveloped, with existing prototypes falling short of commercial requirements.
These challenges mean MnBi magnets are not yet a practical substitute for rare-earth magnets in EV motors, though ongoing research attempts to address these issues to enable future adoption.
This evaluation is grounded in recent research and developments from 2023 and 2024 focusing on MnBi magnets in EV motor design.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/are-there-any-significant-challenges-in-using-manganese-bismuth-magnets-in-evs/
