Graphene oxide-assisted synthesis of LiMn2O4 nanopowder

Łukasz Majchrzycki,Monika Michalska,Mariusz Walkowiak,Zbigniew Wiliński,Ludwika Lipińska

doi:10.2478/pjct-2013-0038

Abstract

Abstract The article reports sol-gel synthesis of nanosized spinel-type lithium manganese oxide LiMn2O4 (LMO) carried out in the presence of graphene oxide (GO) and its electrochemical lithium insertion ability. The synthesis was performed in an aqueous environment with lithium acetate and manganese acetate used as precursors and citric acid as a chelating agent. The material was characterized by X-ray diffraction, SEM microscopy, Raman spectroscopy and cyclic voltammetry. The calcination step totally eliminated graphene from the final product, nevertheless its presence during the synthesis was found to affect the resulting LiMn2O4 morphology by markedly reducing the size of grains. Moreover, potentials of electrochemical lithium insertion/deinsertion reactions have been shifted, as observed in the cyclic voltammetry measurements. Along with the diminished grain size the voltammetric curves of the graphene oxide-modified material exhibit higher oxidation and lower reduction peak currents. The study demonstrates that GO mediation/assistance during the sol-gel synthesis fosters more nanostructured powder and changes the electrochemical characteristics of the product

Highlights

Lithium-ion batteries (LIBs) are commonly used in portable electronic devices because of their high voltage and high energy density
In this study we report on the preparation and characterization of spinel-structure LiMn2O4 (LMO) with nanometric particles, synthesized by the sol-gel method with graphene oxide (GO) used as a mediator/nanostructure promotor
We have been able to demonstrate that the presence of GO significantly affected the morphology of the main product, clearly leading to obtaining LMO with grain size reduced to nano-scale

Summary

INTRODUCTION

Lithium-ion batteries (LIBs) are commonly used in portable electronic devices because of their high voltage and high energy density. The electrochemical properties of this material strongly depend on its physicochemical characteristics, such as crystallinity, particle size, specific surface area[9] and character of chemical bonding[10] These properties can be controlled by the conditions of the fabrication process. Vast majority of scientific works indicate that much higher temperatures (typically 500–750oC) are needed to obtain spinel phase with satisfactory lithium insertion ability[9]. We have been able to demonstrate that the presence of GO significantly affected the morphology of the main product, clearly leading to obtaining LMO with grain size reduced to nano-scale This effect of nanoparticle stabilization by GO in solution followed by its removal is referred to within this work as GO mediation in the process of LMO sol-gel synthesis

Preparation of GO

Material characterization

Structure and morphology

Electrochemical performance

CONCLUSIONS

LITERATURE CITED