Japanese researchers at Yokohama National University have demonstrated a promising alternative to nickel- and cobalt-based batteries for electric vehicles (EVs).
Their approach uses manganese in the anode to create a cost-effective, sustainable, high-energy density battery.
EV manufacturers prefer nickel and cobalt batteries because they offer higher energy density and can achieve longer driving ranges with smaller battery packs, but both components are expensive to procure and relatively rare, making them unsustainable options if EV use surges around the world.
Lithium-ion (Li-ion) batteries are the preferred rechargeable battery option for most electronic devices, but are at a disadvantage in EVs due to their low energy density. Research and development efforts to improve them have introduced better Li-ion options.
There has also been experimentation with using manganese as an anode material alongside lithium, such as LiMnO2. However, applications have been limited due to poor electrode performance. Researchers at Yokohama National University (YNU) in Japan have addressed this issue in a recent study.
Treatment of monoclinic crystals
After thoroughly studying the different morphologies of LiMnO2 using X-ray diffraction, scanning electron microscopy and electrochemical techniques, YNU researcher Naoaki Yabuuchi and his team discovered that layered domains of the monoclinic system activate the structural transition of LiMnO2 to a spinel-like phase. The monoclinic system is a type of group symmetry for solid crystal structures.
LiMnO2 enhances the performance of the electrode material by promoting the phase transition, without which the performance of the LiMnO2 electrode would be suboptimal.
“Through this discovery, nanostructured LiMnO2 with a monoclinic layered domain structure and high surface area has been directly synthesized using a simple solid-state reaction,” Yabuuchi said in a press release.
This reaction does not have an intermediate step and can be directly synthesized from the two components using a calcination process.
Mn improves performance
Post-synthesis testing revealed that the energy density of the battery using the LiMnO2 electrodes reached 820 watt-hours per kilogram (Wh kg-1), compared to 750 Wh per kilogram for the nickel-based battery. Only the lithium-based battery has a lower energy density of 500 Wh per kilogram.
Using manganese in other polymorphs typically results in half the energy density capacity, the researchers said in an email to Interesting Engineering.
Previous studies using manganese have reported battery voltage degradation, which means a decrease in voltage output over time and poor performance in electronic devices, but with the LiMnO2 electrode the researchers observed no such results.
Manganese dissolution could still occur due to a phase change or reaction with acidic solutions, the press release added, and the researchers plan to address this issue by using a highly concentrated electrolyte solution and a lithium phosphate coating.
The researchers are confident that their work has contributed to the development of a new product that is competitive with existing options, sustainable to produce, and environmentally friendly in the long run. They look forward to commercializing their technology and applying it in the EV industry.
“We have discovered a very inexpensive methodology, which is a key finding of our study,” the team added in an email to IE.
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About the Editor
Ameya Pareja Ameya is a science writer based in Hyderabad, India. A molecular biologist at heart, he put down his micropipette to write science articles during the pandemic and has no plans to go back. He loves writing about genetics, microbiology, technology and public policy.
