Enhanced Cycle Stability of Zinc Sulfide Anode for High-Performance Lithium-Ion Storage: Effect of Conductive Hybrid Matrix on Active ZnS.

Quoc Hanh Nguyen,Jaehyun Hur,Taehyun Park

doi:10.3390/nano9091221

Abstract

Zinc sulfide (ZnS) nanocrystallites embedded in a conductive hybrid matrix of titanium carbide and carbon, are successfully fabricated via a facile high-energy ball-milling (HEBM) process. The structural and morphological analyses of the ZnS-TiC-C nanocomposites reveal that ZnS and TiC nanocrystallites are homogeneously distributed in an amorphous carbon matrix. Compared with ZnS-C and ZnS composites, the ZnS-TiC-C nanocomposite exhibits significantly improved electrochemical performance, delivering a highly reversible specific capacity (613 mA h g−1 over 600 cycles at 0.1 A g−1, i.e., ~85% capacity retention), excellent long-term cyclic performance (545 mA h g−1 and 467 mA h g−1 at 0.5 A g−1 and 1 A g−1, respectively, after 600 cycles), and good rate capability at 10 A g−1 (69% capacity retention at 0.1 A g−1). The electrochemical performance is significantly improved, primarily owing to the presence of conductive hybrid matrix of titanium carbide and amorphous carbon in the ZnS-TiC-C nanocomposites. The matrix not only provides high conductivity but also acts as a mechanical buffering matrix preventing huge volume changes during prolonged cycling. The lithiation/delithiation mechanisms of the ZnS-TiC-C electrodes are examined via ex situ X-ray diffraction (XRD) analysis. Furthermore, to investigate the practical application of the ZnS-TiC-C nanocomposite, a coin-type full cell consisting of a ZnS-TiC-C anode and a LiFePO4–graphite cathode is assembled and characterized. The cell exhibits excellent cyclic stability up to 200 cycles and a good rate performance. This study clearly demonstrates that the ZnS-TiC-C nanocomposite can be a promising negative electrode material for the next-generation lithium-ion batteries.

Highlights

Rechargeable Li-ion batteries (LIBs) have been widely used for mobile portable electronic devices and electric vehicles, owing to their high energy densities, long lifecycles, and low self-discharge rates [1,2,3]
Pure Zn, Ti, and S peaks were observed after the first high-energy ball-milling (HEBM) step, the mixture was completely converted into alloy phases, including Zinc sulfide (ZnS), titanium carbide (TiC), and amorphous C, after the second HEBM step (Figure 1a)
No additional peaks were detected, suggesting there are no impurities in the final product and that the Zn, S, Ti, and C were completely transformed into ZnS and TiC crystallites and amorphous C after the two-step ball-milling process

Summary

Introduction

Rechargeable Li-ion batteries (LIBs) have been widely used for mobile portable electronic devices and electric vehicles, owing to their high energy densities, long lifecycles, and low self-discharge rates [1,2,3]. Its beneficial features including natural abundance, inexpensiveness, and environmental friendliness suggest Zn as a promising material for LIB anodes Despite these merits, Zn-based anodes inevitably undergo large volume expansion (about 70% and 228% for Zn and ZnO anodes, respectively) [26,27] during Li alloying/dealloying, resulting in the particle pulverization of active particles upon extended electrochemical cycling, which lead to poor cycling performance, similar to other Li-alloying materials [12,16]. The synergistic effect between titanium carbide and amorphous carbon in the conductive TiC-C hybrid matrix provides the high electrical conductivity and mitigates particle aggregation, improving the electrochemical performance [33]

Methods

Results

Conclusion