Issue 5, 2013

Surface aging at olivine LiFePO4: a direct visual observation of iron dissolution and the protection role of nano-carbon coating

Abstract

LiFePO4 has attracted much attention as a potential cathode material for advanced lithium-ion batteries due to its superior thermal stability. In spite of this, LiFePO4 still suffers from fast capacity fading at high temperature and/or moisture-contaminated electrolyte. The influence of moisture and the detailed corrosion mechanism is still not clear. Here, for the first time, we present a direct visual observation of the surface corrosion process at olivine LiFePO4 stored in moisture-contaminated electrolyte, and found the direct relationship between iron dissolution and LiFePO4 corrosion. By using the LiFePO4 ingot sample with a flat surface as model materials, iron dissolution and surface chemistry change can be clearly observed and identified by field-emission scanning electron microscopy (SEM), time-of-flight-secondary ion mass spectroscopy (TOF-SIMS), and X-ray absorption near-edge structure (XANES). These iron dissolutions at some corrosion sites evoked the overall LiFePO4 surface corrosion. A significant improvement of the surface stability of LiFePO4 was obtained by nano-carbon coating, and the carbon surface layer protects LiFePO4 from direct contact with corrosive medium, effectively restraining the surface corrosion and preserving the initial surface chemistry of LiFePO4.

Graphical abstract: Surface aging at olivine LiFePO4: a direct visual observation of iron dissolution and the protection role of nano-carbon coating

Article information

Article type
Paper
Submitted
01 oct. 2012
Accepted
09 nov. 2012
First published
23 nov. 2012

J. Mater. Chem. A, 2013,1, 1579-1586

Surface aging at olivine LiFePO4: a direct visual observation of iron dissolution and the protection role of nano-carbon coating

J. Wang, J. Yang, Y. Tang, R. Li, G. Liang, T. Sham and X. Sun, J. Mater. Chem. A, 2013, 1, 1579 DOI: 10.1039/C2TA00521B

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