Reduced Graphene Oxide Aerogels with Functionalization-Mediated Disordered Stacking for Sodium-Ion Batteries

Jaehyeung Park,Ngoc A Nguyen,Jaswinder Sharma,Lilin He,Harry M Meyer,Jong K Keum,Charl J Jafta,Georgios Polizos,Jianlin Li

doi:10.3390/batteries8020012

Jaehyeung Park, Ngoc A Nguyen + Show 7 more

Open Access

https://doi.org/10.3390/batteries8020012

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Abstract

Surface modified reduced graphene oxide (rGO) aerogels were synthesized using the hydrothermal method. Ethylene diamine (EDA) and α-cyclodextrin (CD) were used to functionalize the surface of the graphene oxide layers. The oxygen reduction and surface modification occurred in-situ during the hydrothermal self-assembly process. The chemical functionality and structure of the resulting ethylene diamine modified (rGO-EDA) and cyclodextrin modified (rGO-CD) aerogels as well as of the pristine unmodified rGO aerogel were studied using XPS, SEM, XRD, and SANS techniques. The overall surface composition showed a significant decrease in the oxygen content for all synthesized aerogels. The surface modified aerogels were characterized by a disordered stacking of the assembled rGO layers. The surface functionalities resulted in a broad distribution of the interlayer spacing and introduced structural heterogeneities. Such disordered structures can enable a better adsorption mechanism of the sodium ions. Coin cells based on the synthesized aerogels and sodium metal were assembled and tested at several charge and discharge rates. The correlation between the surface functionality of the rGO, the induced structural heterogeneities due to the disordered stacking, and the electrochemical performance of sodium-ion batteries were investigated. Operando XRD measurements were carried out during the battery cycling to investigate the adsorption or intercalation nature of the sodiation mechanism.

Highlights

High performance electrochemical energy storage devices are in high demand due to the recent technological advances in the transportation and consumer electrics sectors [1,2,3,4,5]
The walls of the pore channels are made of assembled reduced graphene oxide (rGO) layers
The structure of the assembled layers is dependent on the surface functionality and the spatial heterogeneities that are formed during the assembly process

Summary

Introduction

High performance electrochemical energy storage devices are in high demand due to the recent technological advances in the transportation and consumer electrics sectors [1,2,3,4,5]. Threedimensional (3D) carbon structures such as graphene or reduced graphene oxide (rGO) aerogels are strong candidate materials for electrodes due to their superior electrochemical and mechanical properties as well as due to their high specific surface area [31,32,33,34]. In absence of Na+ intercalation, a disordered assembly of the rGO layers may increase the rGO surface area that is accessible by the Na+ ions This configuration is expected to enhance the Na+ ion adsorption on the interconnected rGO channels and improve the electrochemical performance of the sodium-ion battery. Operando X-ray diffraction (XRD) measurements were performed to investigate if the sodiation of the disordered aerogel electrode occurs through an adsorption or intercalation mechanism

Experimental

Results and Discussion

Conclusions