Hong Kong University’s Engineering team unveils a breakthrough in battery tech

A breakthrough for batteries: A research team at the University of Hong Kong’s (HKU) Department of Mechanical Engineering conducted a study to develop a high-performance quasi-solid-state magnesium-ion battery (QSMB) that offers a solution to the limitations of conventional lithium-ion (Li-ion) batteries, Media OutReach writes. Magnesium batteries emerged in recent years as a promising alternative to lithium batteries due to their relatively higher capacity potential as a result of the metal having twice as many electrons as lithium.

How do Mg-ionbatteries work? Mg-ion batteries function similarly to Li-ion ones. Magnesium ions move between a negative anode — typically made of magnesium metal — and a positive cathode, made of a metal-oxide material allowing electrons to flow to generate electricity. Mg-ions have double the electrons of Li-ions giving them a higher energy density potential. Yet they had to overcome several technical challenges before becoming a commercial competitor with Li-ion batteries.

So why isn’t magnesium used more in batteries? Magnesium-ions (Mg-ion) carry a lot of electric charge which can result in a lot of unwanted interactions with surrounding materials. This overreaction hampers the process of storing charge which limits the lifetime of the batteries. “Hydrogen ions, or protons, are smaller and lighter compared to the metal ions. Because of their size, protons can easily get into the battery's cathode structure. However, this creates a problem because protons and Mg ions compete for space, which severely limits how much energy the battery can store and how long it can last," said the first author of the study, PhD student Sarah Leong.

Enter QSMB: The QSMB model uses a polymer-enhanced electrolyte which helps control the competition between protons and metal ions. The model has a high voltage plateau and energy density which the study says surpassed current Mg-ion batteries and almost matched Li-ion ones. Even under subzero temperatures and after running 900 charging and discharging cycles, the model was still able to retain 90% of its ability to store energy.

Why does this matter? Li-ion batteries in EVs have a few challenges including the sustainability impacts and limited availability of elements like cobalt limiting their scalability. They also can't provide the higher energy densities needed to expand power storage to long-haul trucks, rail, marine, and aviation. Mg-ion batteries can solve some of these due to their lower cost, higher sustainability, and performance in energy storage. Magnesium is also more abundant than lithium which allows for better supply chains.