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The Role of Reduced Graphite Oxide in Transition Metal Oxide Nanocomposites Used as Li Anode Material: An Operando Study on CoFe 2 O 4 /rGO
Author(s) -
Permien Stefan,
Indris Sylvio,
Neubüser Gero,
Fiedler Andy,
Kienle Lorenz,
Zander Stefan,
Doyle Stephen,
Richter Björn,
Bensch Wolfgang
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201603160
Subject(s) - materials science , oxide , cyclic voltammetry , nanoparticle , nanocomposite , x ray absorption spectroscopy , raman spectroscopy , spinel , graphite oxide , graphite , amorphous solid , chemical engineering , transition metal , metal , absorption spectroscopy , inorganic chemistry , electrochemistry , nanotechnology , electrode , chemistry , metallurgy , crystallography , catalysis , organic chemistry , physics , engineering , quantum mechanics , optics
A composite consisting of CoFe 2 O 4 spinel nanoparticles and reduced graphite oxide (rGO) is studied as an anode material during Li uptake and release by applying synchrotron operando X‐ray diffraction (XRD) and operando X‐ray absorption spectroscopy (XAS), yielding a comprehensive picture of the reaction mechanisms. In the early stages of Li uptake, a monoxide is formed as an intermediate phase containing Fe 2+ and Co 2+ ions; this observation is in contrast to reaction pathways proposed in the literature. In the fully discharged state, metallic Co and Fe nanoparticles are embedded in an amorphous Li 2 O matrix. During charge, metallic Co and Fe are oxidized simultaneously to Co 2+ and Fe 3+ , respectively, thus enabling a high and stable capacity to be achieved. Here, evidence is presented that the rGO acts as a support for the nanoparticles and prevents the particles from contact loss. The operando investigations are complemented by TEM, Raman spectroscopy, galvanostatic cycling, and cyclic voltammetry.