RECHARGEABLE BATTERY MATERIALS

Rechargeable Battery Materials

Abstract

Two aliphatic thioether polymers, poly[methanetetryl-tetra(thiomethylene)] (PMTTM) and poly(2,4-dithiopentanylene) (PDTP) were conceived, synthesized, distinuished and checked as cathode hardworking materials. The chemical structure of polymers was verified by FT-IR, FT-Raman, and XPS spectral analysis. Both polymers were found to have electrochemical undertaking as cathode components for rechargeable lithium electric battery by the electrochemical tests. The specific capacity of PMTTM was 504 mA h g-1 at the third cycle and faded to 200 mA h g-1 after 10 cycles; PDTP showed low and stable specific capacity around 100 mA h g-1 even after 50 cycles. The specific capability of completely saturated aliphatic thioether polymers demonstrated that thioether bonds offered power storage. It was suggested that thioether bond was oxidized to form thioether cations with the help of ether solvents.

Rechargeable Battery Materials

1. Introduction

Since Liu and Visco et al. [1] and [2] found organic disulfide mixtures could be used as cathode hardworking components for rechargeable lithium battery in the late of 1980s, many researches have been focused on the development of organic disulfide components [3], [4]H. Tsutsumi, K. Okada, K. Fujita and T. Oishi, J. Power causes 68 (1997), pp. 735-738. Abstract | PDF (301 K) | View Record in Scopus | Cited By in Scopus (7)[4], [5], [6], [7], [8], [9], [10], [11], [12], [13] and [14]. The electrode reactions of the disulfide compounds are based on the reversible cleavage-combination of S-S bond. However, we discovered lately that two organic thioether compounds, poly[1,4-di(1,3-dithiolan-2-yl)benzene] and poly(2-phenyl-1,3-dithiolane), could furthermore store power as cathode active materials [15], and thioether function group was proposed as a functional assembly to offer electrode reactions: C-S-C ? C-S+-. Both the two polymers are created of conjugated polyphenylene chains with thiolane as pendents. Since polyphenylene is well known cathode active material with specific capacity of tens mA hg-1 [16], it is essential to examine whether the thioether structure alone is enough to offer specific capacity in polymers. To enquire the redox function of thioether assemblies, two novel aliphatic thioether polymers, poly[methanetetryl-tetra(thiomethylene)] (PMTTM) and poly(2,4-dithiopentanylene) (PDTP), were designed, synthesized, and their electrochemical activity was furthermore tested. There are three kinds of bonds in PMTTM and PDTP: C-C, C-H, and C-S-C bonds. Since the saturated C-C and C-H bonds cannot afford redox reaction, thioether bond is the only possible electrochemical active function group among them. Therefore, we can approximate the electrochemical undertaking of thioether function assembly by electrochemical behaviors of PMTTM and PDTP.

2. Experimental

2.1. Materials

Sodium, anhydrous ethanol, perbromomethane and bibromomethane were AR purity and ethane-1,2-dithiol was 98% purity. All reagents were utilised as received except otherwise indicated.

The synthetic routes and structures of the polymers are described in Scheme 1a. Ausual synthetic method of PMTTM was recounted as below. In a three-neck flask equipped with gas conductor, condenser, and magnetic stirrer, sodium granules (2.0 g, 87 mmol) were added to 30 ml anhydrous ethanol and mixed under nitrogen atmosphere at room warmth till sodium disintegrated completely. Ethane-1,2-dithiol (3.0 ml, 35 mmol) was added to the solution and the reactants were ...