NEW MATERIAL FOR LITHIUM-ION BATTERIES WITH BETTER PERFORMANCE

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Cerdanyola del Vallès, 9 June 2022. With the increment of electric and hybrid electric vehicles, there is an increasing need for electrical energy storage devices. To meet these requirements, next-generation lithium-ion batteries that utilize high-energy cathode materials are crucially needed. Among various types of cathode materials, Lithium- and Manganese-rich layered oxides (LMLOs) are one of the most promising candidates owing to their high capacity - the total amount of electricity generated in the battery - and low cost.

Traditionally, this kind of battery material is polycrystalline LMLOs (LMLO-PC). A polycrystal is formed by many individual smaller crystals with random orientations, known as grains or crystallites. Although this microstructure boosts the diffusion of lithium-ions inside the battery materials, they are prone to fast degradation caused by mechanical stresses during battery operation, which seriously hinders their practical application.

Researchers have developed a new approach to synthesis of a single-crystalline lithium- and manganese-rich layered oxide (LMLO-SC) battery material via a lithium/sodium ion exchange reaction. This is a type of chemical reaction in which sodium-containing substances react with lithium salt solutions to selectively remove sodium ions and replace them with lithium ions from the solution. Therefore, the obtained lithium-containing materials possess a crystallographic structure, particle morphology, and size similar to their sodium analogues.

For this work specifically, researchers have used single-crystalline sodium- and manganese-rich layered oxide as a starting material. This approach allows preparing electrodes that keep reasonably high ionic conductivity while being extremely stable with respect to internal stresses compared to its polycrystalline counterpart. As a result, batteries based on the new material can operate for much more charge-discharge cycles than traditional ones without noticeable capacity loss. The new material has potential applications in the field of batteries for electronics, electric cars, etc.

The electrodes were investigated using in situ synchrotron-based X-ray radiation diffraction (sXRD) and X-ray absorption spectroscopy (XAS) at the MSPD beamline in the ALBA Synchrotron and the X-ray radiation source PETRA-III (DESY). The combination of these techniques with transmission electron microscopy (TEM) and electrochemical tests, allowed for the systematic study on the crystal structure, morphology, and electrochemistry of single-crystalline LMLO and its polycrystalline counterpart.

This work is a collaboration between the Xi'an Jiaotong University (China), the Institute for Applied Materials-KIT, the Institute of Nanotechnlogy-KIT and the Deutsches Elektronen-Synchrotron- DESY (Germany), and the ALBA Synchrotron.

Figure. Schematic diagram of the synthesis of polycrystal and single-crystal lithium- and manganese-rich layered oxide - Li[Li_0.2Ni_0.2Mn_0.6]O₂ - cathode materials. Corresponding SXRD, SEM and TEM data.

Reference:  Xiaoxia Yang, Suning Wang, Duzhao Han, Kai Wang, Akhil Tayal, Volodymyr Baran, Alexander Missyul, Qiang Fu, Jiangxuan Song, Helmut Ehrenberg, Sylvio Indris, and Weibo Hua. Structural Origin of Suppressed Voltage Decay in Single-Crystalline Li-Rich Layered Li[Li_0.2Ni_0.2Mn_0.6]O₂ Cathodes. Small (2022). DOI: 10.1002/smll.202201522

With the collaboration of Fundación Española para la Ciencia y la Tecnología. The ALBA Synchrotron is part of the of the Unidades de Cultura Científica y de la Innovación (UCC+i) of the FECYT and has received support through the FCT-20-15798 project.