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Graphene Wrapped Fe3O4 Nanoparticles as Stable and High Performance Anodes for Lithium Ion Batteries

Abstract This chapter deals with the investigation of lithium storage in rGO/Fe3O4 nanocomposites prepared by a simple precipitation method followed by annealing at different temperatures and environments such as 80 °C in air, 600 °C in Ar, 700 °C in Ar and 700 °C in Ar–H2. The sample obtained at 80 °C exhibit a high surface area of 30 m2 g−1. Electrochemcial properties of the different rGO wrapped magnetite nanoparticles were investigated by cyclic voltammetry and galvanostatic cycling and EIS studies. They exhibit stable and high capacity and minimal capacity fading. In addition, they exhibit good rate capability. The rGO/Fe3O4 composite obtained at 700 °C in Ar–H2 exhibits the best rate capability with a high reversible capacity of 480 mAh g−1 at a high current density of 3000 mA g−1.

8.1

Introduction

In the recent years, various iron based oxides such as Fe2O3 [1–3], Fe3O4 [4–6], MFe2O4 (M = Ni, Co, Mn, Zn) [7–12], etc., have attracted huge interest as anode materials for Lithium ion batteries as a replacement for commercial graphite. Lithium storage occurs in these oxides via conversion (redox) mechanism in which the oxides reversibly react with lithium forming Li2O along with metal nanoparticles [13]. These Fe based oxides have great advantages as anode materials due to their high reversible capacities, environmental benignity, low cost and abundance [2]. However, their commercialization has been hindered by their poor Lithium cycling, high operating potentials and large polarization due to the poor lithiation/de-lithiation kinetics which need to be addressed for utilization of these oxides as commercial anodes. Magnetite phase (Fe3O4) is one of the attractive anodes and it exhibits a normal spinel structure in which the divalent and trivalent ions occupy the tetrahedral and octahedral sites respectively. It undergoes reversible lithium storage via a conversion reaction described by the Eq. 8.1. It has a theoretical capacity of 926 mAh g−1, assuming 8 mol of Li uptake/extraction per mole of Fe3O4.

© Springer Science+Business Media Singapore 2016 A.S. Hameed, Phosphate Based Cathodes and Reduced Graphene Oxide Composite Anodes for Energy Storage Applications, Springer Theses, DOI 10.1007/978-981-10-2302-6_8

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8 Graphene Wrapped Fe3O4 Nanoparticles as Stable …

Fe3 O4 þ 8 Li $ 3 Fe þ 4 Li2 O

ð8:1Þ

Lithium storage properties of the iron oxide a-Fe2O3 has been reported to improve when they are prepared in the form of nanoparticles, owing to the good Li transport as well as they ease the strain of the conversion reaction [14]. This motivated the study of Fe3O4 nanoparticles prepared by various synthetic routes like solvothermal [15, 16], hydrothermal [17, 18], carbothermal reduction [19], sol gel [20], electrospinning [21], etc., for anode application in LIBs. In addition, different strategies were used to improve the electronic conductivity of the material which include carbon coating [22, 23] and