Electrochemical properties of Sn-Co electrodes with various binder materials for sodium ion batteries

Introduction

With the rapid advancement of technology in our time, we know that lithium-ion batteries (LIBs) are used for power storage in mobile devices, electrical products and electric vehicles, and the demand for them is likely to increase. However, lithium is expensive because it is not an abundant metal. Sodium, on the other hand, is abundant and inexpensive, and interest in sodium ion batteries (SIBs) has been growing. Materials that have been investigated for use as SIB anodes include hard carbon, tin, tin-based materials, antimony-based materials, germanium, and oxide materials. However, few materials can meet the requirements of both high capacity and good cycling performance. In a previous study, we focused on Sn-Co and found that it exhibited better cycling performance than tin electrodes. In addition, to improve the cyclability of alloy anodes for Li-ion batteries in recent years, various binders such as polyacrylic acid (PAA), sodium polyacrylate (PAANa), sodium carboxymethylcellulose (CMC), and polyimide (PI) have been investigated. In this study, the electrochemical performance of negative electrodes with PAA, PAANa, CMC, and PI as binder materials was investigated to further improve recyclability. In addition, the study of the volume and adhesion strength variations of the electrodes with the binders reveals their relationship with the cycling performance.

Applications

This paper focuses on the charge and discharge performance of Sn-Co anode materials with various binders [polyvinylidene fluoride (PVdF), polyacrylic acid (PAA), sodium polyacrylate (PAANa), sodium carboxymethylcellulose (CMC), and polyimide (PI)] for sodium ions, and studied the cells to determine the correlation between the cycling performance and the performance of the electrodes with binders, compared with PVdF, PAANa or PI, Sn-Co electrodes with PAA or CMC binders exhibited better cycling performance (discharge capacity over 400 mAh/g for up to 20 cycles) using PAA or CMC due to the volume of the electrode occurring during cycling as shown by in situ optical microscopy.

Image 1 shows the change in WE volume during the first cycle by direct observation using an in situ optical microscope (Lasertec Corp., ECCS B310). The expansion and contraction rates of WEs were estimated in linear analysis mode. The cross section of the semicircular cell of WE/separator/CE (Na) was monitored by using an optical microscope in the same way as previously reported through a viewing window made of sapphire. Discharge-charge tests were performed under the same conditions as described above for button cells, and the results were similar to those for button cells.

Source

Authors: Yuhki Yui , Masahiko Hayashi , Katsuya Hayashi , Jiro Nakamura

Institution: NTT Device Technology Labs., NTT Corporation, Atsugi, Kanagawa, Japan b Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan c NTT Network Technology Labs.

Published: Received 17 July 2015; Received in revised form 24 November 2015; Accepted 2 January 2016

Keywords: sodium ion battery, anode, binder, tin-cobalt, in-situ optical microscopy, Secas

Journal: Elsevier B.V. All rights reserved.

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