An international research team, co-led by The University of Texas at Austin, has found a number of transition-metal oxides with up to three times the energy storage capability of materials in commercially available lithium-ion batteries
The team found metal oxides possess unique ways to store energy beyond classic electrochemical storage mechanisms, which could lead to smaller, more powerful batteries.
At the centre of the findings are transition-metal oxides, which are compounds that include oxygen bonded with transition metals such as iron, nickel and zinc.
The research was published in the journal Nature Materials.
The team started with transition-metal oxides materials (common in minerals) such as Fe3O4, CoO, NiO.
Professor Guihua Yu, Materials Science and Engineering, Mechanical Engineering Texas Materials Institute, UT Energy Institute, told BEST the key finding in this work was revealing a clear mechanism of why this class of metal oxide materials showed unusually high capacity compared to current commercial ones (LiCoO2, LiFePO4, NMC).
He said: “Classic mechanisms for working battery electrode materials are mainly based on intercalation (Li ions intercalate in and out of a material’s crystal lattices without structure changes, such as LiCoO2 cathode, graphite anode) or conversion (materials react with Li ions and convert to different materials with different crystal structures).
“The ‘space charge storage mechanism’ we experimentally confirmed in this study for metal oxides materials shows another interesting and powerful way to rapidly and reversibly store electrons (energy).
“This ‘spin capacitance’ results from nanosized metal particles (such as Fe), which are formed from reduction of metal oxides when reacts with Li ions.”
Energy can be stored inside the metal oxides— as opposed to typical methods that see lithium ions move in and out of these materials or convert their crystal structures for energy storage.
The researchers reported that additional charge capacity could be stored at the surface of iron nanoparticles formed during a series of conventional electrochemical processes.
According to the research, a broad range of transition metals can unlock this extra capacity because they share the ability to collect a high density of electrons.
Yu said, these materials aren’t yet ready for prime time, primarily because of a lack of knowledge about them, but the findings should go a long way in shedding light on the potential of these materials.
The key technique employed in this study, named in-situ magnetometry, is a real-time magnetic monitoring method to investigate the evolution of a material’s internal electronic structure.
It is able to quantify the charge capacity by measuring variations in magnetism. This technique can be used to study charge storage at a very small scale that is beyond the capabilities of many conventional characterisation tools.
The research team are from the following institutes: UT, the Massachusetts Institute of Technology, the University of Waterloo in Canada, Shandong University of China, Qingdao University in China and the Chinese Academy of Sciences participated in the project.
