Technology
converting waste heat into electricity Magnesium silicide (Mg2
Sb-doped Mg2 Si) is a thermoelectric
material that can convert heat into electricity. Adding antimony (Sb) impurities enhances its performance and, now, scientists from the Tokyo University of Science (TUS) in Japan have analysed the effects of these impurities at the atomic level. Te result is a step closer to efficiently harvesting waste heat from cars and thermal power plants to produce clean energy. In the search for solutions to ever-worsening
environmental problems, such as the depletion of fossil fuels and climate change, many have recognised the potential of thermoelectric materials to generate power. Tese materials exhibit a thermoelectric effect, creating a voltage difference when there is a temperature gradient across the material. Tis can be exploited to produce electricity using the enormous amount of waste heat generated by human activity, thereby providing an eco-friendly alternative to our energy needs. Magnesium silicide is a particularly promising
thermoelectric material with a high “figure of merit” (ZT), a measure of its conversion performance. Although scientists previously
noted that doping Mg2 Si more efficient in Si with a small amount
of impurities improves its ZT by increasing its electrical conductivity yet reducing its thermal conductivity, the underlying mechanisms behind these changes were unknown – until now. TUS teamed up with the Japan Synchrotron Radiation Research Institute (JASRI) and Shimane University, Japan, to uncover the mysteries behind the improved performance of Mg2
Si
doped with antimony. “Although it has been found that Sb
impurities increase the ZT of Mg2Si, the
resulting changes in the local structure and electronic states that cause this effect have not been elucidated experimentally. Tis information is critical to understanding the mechanisms behind thermoelectric performance and improving the next generation of thermoelectric materials,” said Dr Masato Kotsugi from TUS. Te scientists found that Sb atoms replace Si
atoms in the Mg2Si crystal lattice and introduce
a slight distortion in the interatomic distances. Tis could promote a phenomenon called phonon scattering, which reduces the thermal
The setup at Spring-8 used to run the antimony-doped magnesium silicide material
conductivity of the material and, in turn, increases its ZT. Moreover, because Sb atoms contain one more valence electron than Si, they effectively provide additional charge carriers that bridge the gap between the valence and conduction bands; simply put, Sb impurities unlock energy states that ease the energy jump required by electrons to circulate. As a result, the electrical conductivity of doped Mg2
Si increases, and so does its ZT.
Project Quantum signals a new era for British EV battery manufacturing
Innovate UK has launched a three-year, £5.4m project called Project Quantum to develop cutting-edge battery manufacturing solutions and make the UK a world leader in the field. Electric vehicles (EVs) are forecast to
account for one in five car sales by 2026, which means the demand for its most valuable component – the lithium ion battery – will soon skyrocket. Project Quantum is expected to drive productivity and economic growth in this sector and support the UK’s transition to electrification. Te project will commercialise known quantum technology, to address identified inefficiencies and challenges in the manufacture of lithium cells. Quantum technology enables highly- sensitive measurements of magnetic fields to improve quality yields, and effectively grade new batteries – reducing the time taken for the ageing process from weeks to days.
“There is an urgent need for rapid,
continuous and non-invasive monitoring of the cell ageing process on the production line. New quantum sensing technology can cut the cost of production and provide additional capability in grading battery quality, meaning more cells can be produced in less time,” said Kevin Brundish, CEO of AMTE Power, the British battery manufacturer leading Project Quantum. Scaleable battery production is forecast
to be worth $5bn in five years’ time, and the UK-BIC (Battery Industrialisation Centre) facility in Coventry will soon open, to aid the UK’s transition to world leadership in battery development and manufacture, complementing AMTE Power’s ambition to open the country’s first gigafactory – capable of producing millions of cells onshore every year.
“Making the battery production process
both more efficient and greener is a crucial step towards the UK meeting its zero-carbon climate objectives, especially since about half of vehicle production will be wholly or partially electric by 2030. Aligning with the Government’s Industrial Strategy, which outlines its ambitions on EV and battery technologies, the UK should now be building out an independent infrastructure for lithium-ion batteries, in support of firms like AMTE Power’s gigafactory expansion plans,” said Brundish. Other Project Quantum partners include
Compound Semiconductor Centre, Magnetic Shields, Compound Semiconductor Technologies, Alter Technology, Kelvin Nanotechnology, Centre for Process Innovation, CDO2, University of Strathclyde and University of Sussex.
www.electronicsworld.co.uk November/December 2020 05
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