A research team from the University of Hong Kong’s Department of Mechanical Engineering has achieved a major breakthrough in battery technology with the development of a high-performance quasi-solid-state magnesium-ion (QSMB) battery. The battery’s innovative design offers a sustainable, safe and high-energy-density alternative to conventional lithium-ion batteries, addressing the latter’s limitations of material scarcity and safety concerns.
According to Professor Dennis YC Leung, who led the research, the new battery has the potential to revolutionise the industry. ‘It is a game-changing development,’ he said.
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In recent years, magnesium-ion batteries have emerged as a potential solution to the limitations of lithium-ion batteries. However, the road to developing efficient magnesium-ion batteries has been fraught with challenges, including the need to overcome the narrow electrochemical window in aqueous or water-based systems, and the poor ionic conductivity in non-aqueous systems.
Addressing these obstacles, Professor Leung’s team developed a water-in-salt magnesium-ion battery with an operating voltage above two volts. However, it still lagged behind non-aqueous counterparts due to the dominance of protons over magnesium-ion storage in the cathode.
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‘Hydrogen ions, or protons, are smaller and lighter than the metal ions,’ said Sarah Leong, a PhD student in Professor Leung’s team. ‘Because of their size, protons can easily get into the battery’s cathode structure. This creates a problem because protons and magnesium ions compete for space, which severely limits how much energy the battery can store and how long it can last.’
The team’s tireless efforts finally bore fruit, however, thanks to an innovative battery design that uses a polymer-enhanced electrolyte to control the competition between protons and metal ions.
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The resulting battery boasts an impressive voltage plateau of 2.4 volts and an energy density of 264 watt hours per kilogram, surpassing the performance of current magnesium-ion batteries and almost matching the performance of lithium-ion batteries.
‘Our quasi-solid-state magnesium-ion battery combines the best of both worlds, offering the high voltage of non-aqueous systems and the safety and cost-effectiveness of aqueous systems,’ Leung said. ‘It represents a major step forward in the development of high-performance magnesium-ion batteries.’
To put the QSMB to the ultimate test, the research team conducted extensive cycling tests, with astonishing results. Even under extreme conditions of subzero temperatures (–22°C), the QSMB retained an impressive 90 per cent of its capacity after 900 cycles. The battery is also non-flammable and resistant to pressures of more than 40 times atmospheric pressure. This level of durability and performance makes the QSMB a promising candidate for consumer electronics, even in colder climates.
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According to Wending Pan, a research assistant professor in Professor Leung’s team, the QSMB technology has the potential to reshape the landscape of energy storage and power our world sustainably. ‘The advanced electrolyte development strategy presented in our research holds potential beyond magnesium-ion batteries, extending to other multivalent metal ion batteries, such as zinc-ion and aluminium-ion batteries,’ he said. ‘We believe that this study will pave the way for the next generation of energy-storage solutions that are not only efficient but also environmentally friendly.’
The research has been published in Science Advances.