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3020070 
Journal Article 
The role of re-aggregation on the performance of electrochemically exfoliated many-layer graphene for Li-ion batteries 
Sole, C; Drewett, NE; Liu, Fei; Abdelkader, AmrM; Kinloch, IanA; Hardwick, LJ 
2015 
1 
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry
ISSN: 0022-0728 
753 
35-41 
WOS:000362614700007 
Two potential pathways for Li+ diffusion occur within graphitic carbon with typically in-plane diffusion dominating (similar to 10(-7) cm(2) s(-1)) over diffusion along the crystallite grain boundaries (similar to 10(-11) cm(2) s(-1)). Reducing the flake thickness of microcrystalline graphite powders via electrochemical exfoliation offers a method to overcome the latter, sluggish grain boundary Li+ diffusion, thereby increasing the overall rate capability of the graphite negative electrode in a the Li-ion battery. Six micron particulate graphite was electrochemically exfoliated to give flakes of which similar to 90% had a thickness of <10 graphene layers. This exfoliated material was then prepared as an ink and allowed to dry prior to forming a battery electrode. Analysis of the electrode and dried exfoliated powder using powder X-ray diffraction, scanning electron microscopy and Brunauer-Emmett-Teller isotherm analysis show that the material has, apart from a significant reduction of the rhombohedral fraction from 41% to 14%, near-identical properties to that of original starting graphite powder. Thus, once the exfoliated powder has been dried from the exfoliation process, as anticipated, major restacking of the multi-layer graphene flakes had occurred. Likewise there was no significant improvement in using the exfoliated material at high rates of delithiation and lower specific capacity, when tested within a half cell vs. lithium metal. In situ Raman analysis showed that the exfoliated material displayed similar spectral features to the pristine sample during lithiation, as did multi point measurements on differently disordered areas shown from the varying I-D/I-G-band intensity ratios, indicating that local surface disorder does not influence the course of lithium insertion. The re-aggregation of graphenic material is widely recognised, but seldom evaluated. This work shows the importance of keeping graphenic material dispersed at all stages of production. (C) 2015 The Authors. Published by Elsevier B.V. 
In situ Raman microscopy; Li-ion battery; Graphite electrode; Exfoliation; Restacking