Tin-Decorated Reduced Graphene Oxide and NaLi0.2Ni0.25Mn0.75O as Electrode Materials for Sodium-Ion Batteries.

Pier Paolo Prosini,Fabio Maroni,Cinzia Cento,Francesco Nobili,Gabriele Tarquini,Maria Carewska,Agnese Birrozzi

doi:10.3390/ma12071074

Abstract

A tin-decorated reduced graphene oxide, originally developed for lithium-ion batteries, has been investigated as an anode in sodium-ion batteries. The composite has been synthetized through microwave reduction of poly acrylic acid functionalized graphene oxide and a tin oxide organic precursor. The final product morphology reveals a composite in which Sn and SnO2 nanoparticles are homogenously distributed into the reduced graphene oxide matrix. The XRD confirms the initial simultaneous presence of Sn and SnO2 particles. SnRGO electrodes, prepared using Super-P carbon as conducting additive and Pattex PL50 as aqueous binder, were investigated in a sodium metal cell. The Sn-RGO showed a high irreversible first cycle capacity: only 52% of the first cycle discharge capacity was recovered in the following charge cycle. After three cycles, a stable SEI layer was developed and the cell began to work reversibly: the practical reversible capability of the material was 170 mA·h·g−1. Subsequently, a material of formula NaLi0.2Ni0.25Mn0.75Oδ was synthesized by solid-state chemistry. It was found that the cathode showed a high degree of crystallization with hexagonal P2-structure, space group P63/mmc. The material was electrochemically characterized in sodium cell: the discharge-specific capacity increased with cycling, reaching at the end of the fifth cycle a capacity of 82 mA·h·g−1. After testing as a secondary cathode in a sodium metal cell, NaLi0.2Ni0.25Mn0.75Oδ was coupled with SnRGO anode to form a sodium-ion cell. The electrochemical characterization allowed confirmation that the battery was able to reversibly cycle sodium ions. The cell’s power response was evaluated by discharging the SIB at different rates. At the lower discharge rate, the anode capacity approached the rated value (170 mA·h·g−1). By increasing the discharge current, the capacity decreased but the decline was not so pronounced: the anode discharged about 80% of the rated capacity at 1 C rate and more than 50% at 5 C rate.

Highlights

Lithium-ion batteries (LIBs) represent, without any doubt, the more efficient electrochemical technology for storing electricity
The thermal properties of the Sn-reduced graphene oxide (RGO) material and the percentage of tin and carbon were determined by TGA
Since all the metal in the sample was converted into the corresponding oxide, this percentage represents the total tin content expressed as SnO2

Summary

Introduction

Lithium-ion batteries (LIBs) represent, without any doubt, the more efficient electrochemical technology for storing electricity Their development for large-scale applications is limited by the fact that lithium is not so abundant in the Earth’s crust. Sodium is very abundant; the Earth’s crust contains 2.6% sodium by weight, making it the sixth most abundant element on the Earth For this reason, rechargeable electrochemical cells based on sodium appear very promising for large-scale storage applications [2] and represent a valid alternative to replace the most widespread and costly lithium batteries. Studies of intercalation materials suitable for use as cathodes in SIBs began around the 1980s [4,5], but the rapid development of lithium-ion batteries slowed down the research.

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