Journal
ELECTROCHIMICA ACTA
Volume 106, Issue -, Pages 483-493Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2013.05.111
Keywords
Li-ion batteries; Cathodes; Irreversible capacity; Electrolyte decomposition
Categories
Funding
- European Unions [265644 Green Car]
- University of Rome Sapienza
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The accumulation of irreversible capacity in the first cycle and upon cycling has been studied for LiNi0.5Mn1.5O4-based cathodes (LNMO), bare and coated with ZnO. Materials have been synthesized at 800 degrees C and characterized by X-ray diffraction and transmission electron microscopy (TEM). The precipitation of a continuous ZnO film on the surface of LNMO has been highlighted by TEM. Galvanostatic cycling at room temperature and at 60 degrees C, linear sweep voltammetry (LSV), impedance spectroscopy and TEM techniques have been used to investigate the materials and the irreversible capacity accumulation upon cycling. Our study confirms that continuous parasitic processes occur upon cycling beyond the first charge/discharge. Anodic LSV test shows that side oxidation processes start on the surface of a LNMO electrode at potential slightly above the Ni2+/Ni4+ redox couple. At the end of charge an uniform and continuous thin film (3-4 nm) forms of on the bare LNMO. This film likely modifies upon cycling and it is apparently unable to passivate the LNMO surface preventing further decompositions. On the contrary the material coated with ZnO shows rough surfaces without large morphological alteration upon charge and cycling. The ZnO coating confirms its ability to mitigate the irreversible charge consumption. (C) 2013 Elsevier Ltd. All rights reserved.
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