10 Improving magnetic performance in EV motors Researchers in South Korea have developed a process for creating permanent magnets that reduces the need for heavy rare earth elements, writes Nick Flaherty. The process significantly advances the diffusion technology, which is essential for improving magnetic performance, and creates new possibilities for applying high-efficiency magnets in EV motors. Neodymium (Nd-Fe-B) permanent magnets, widely used in EV motors, show decline in magnetic performance under extreme heat, and require the addition of heavy rare earth elements such as terbium and dysprosium to maintain field strength; however, these elements are rare and expensive. The current grain boundary diffusion process is limited to the surface layer and does not penetrate the magnet’s interior, making it difficult to apply to thick magnets. So, the team at the Nano Technology Research Division at DGIST in Korea, led by Dr Donghwan Kim and Dr Jungmin Kim, combined spark plasma sintering with the grain boundary diffusion process. Premixing the diffusion material during the powder-based magnet fabrication stage achieved uniform diffusion throughout the magnet. This increased the diffusion depth, allowing the creation of structures such as a core–shell topology that has a higher, uniform performance. A magnet created at 750 C and 50 MPa achieved near-theoretical density with minimal grain growth. A post-sintering heat treatment at 1000 C significantly enhances coercivity and refines the microstructure, even with the same amount of rare earth material as in conventional magnets, allowing fabrication of smaller and lighter magnets with the same magnetic strength. “This study presents a method that overcomes the limitations of the conventional grain boundary diffusion technology, enabling uniform performance throughout the magnet. It will make a significant contribution to the development of high-performance permanent magnets,” said principal researcher Dr Donghwan Kim. MATERIALS BATTERIES A double-layer electrode design could significantly boost the performance of silicon-graphite batteries, increasing the range of electric vehicles while reducing cost, writes Nick Flaherty. The development of the double-layer electrode design shows significant improvements in the cyclic stability and fast-charging performance of automotive batteries, with the potential to reduce costs by 20–30%. Silicon electrodes can provide a higher theoretical capacity at 3.579 Ah/g – 10 times that of today’s NMC batteries – along with fast charging in a few minutes, but large-scale deployment is held back by substantial volume changes of up to 300% during charge/discharge cycles. This means they degrade quickly and can have limited lifetime. The use of X-ray computed tomography in combination with digital volume correlation imaging techniques, conducted at Queen Mary College of the University of London, enabled 3D visualisation of the morphological changes and local strain in the graphite/ silicon composite electrodes. Five key challenges in materials design were explored, ranging from the tradeoffs between capacity and electronic transport, the porosity trade-offs between capacity and ionic transport through the silicon loss leading to lithium plating, and the graphite enclosure delaying silicon lithiation as well as the silicon expansion blocking electrolyte access. This led to a two-layer graphite/silicon electrode with a silicon content of 35% in a coin cell for testing that has five times the cycle life of a standard silicon electrode. “For the first time, we visualise the interplay between microstructural design and electro-chemo-mechanical performance across length scales – from single particle to full electrode – by integrating multimodal operando imaging techniques,” said Dr Xuekun Lu, who led the study. “This opens new avenues for innovating 3D composite electrode architectures, thereby accelerating large-scale EV adoption.” January/February 2026 | E-Mobility Engineering Silicon battery boost The grain boundaries for permanent magnets (Image: DGIST)
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