Spherical MoS_2/Carbon Composite with Improved Electrochemical Performance for Sodium-Ion Battery Anode

摘要

Lithium-ion batteries (LIBs) with high energy density and long cycle life have been widely applied as the power sources in a variety of fields from portable electronic devices to large-scale energy storage systems (ESSs). Particularly in recent years, owing to the rapid growth of global electric vehicle and ESS markets, the cost of lithium source has risen sharply and many researchers predict a lithium shortage in the near future. In this regard, sodium-ion batteries (SIBs) have recently attracted growing attention because of low price and huge natural abundance of sodium, compared to lithium. However, the larger ionic radius of sodium ion (1.02 A) than that of lithium (0.76 A) results in poor. electrochemical behaviors, which makes it difficult to find suitable anode materials for SIBs. Among many proposed anode materials for SIBs, molybdenum disulfide (MoS_2) is one of promising sodium-ion host materials because of its 2D-layered structure and high theoretical capacity of 670 mA h g~(-1). Despite these advantages, when used as an anode for SIBs, MoS_2 exhibits several problems associated with low cycling stability and poor rate performance caused by large volume change during sodium insertion and extraction and low electrical conductivity. In order to solve the aforementioned drawbacks of MoS_2, herein, we present a spherical-shaped MoS_2/carbon (MoS_2/C) composite as a high-performance anode for SIBs. The spherical MoS_2/C composites were synthesized by a facile and simple in situ wet chemical method using furfural as a surfactant as well as a carbon source. The as-prepared MoS_2/C composite showed uniform distribution of MoS_2 particles in the mesoporous carbonaceous matrix, which not only effectively alleviates large volume variation during repeated cycling, but also ensures high electrical conductivity. Owing to these benefits of good dispersion of active materials and the introduction of multifunctional matrix, the spherical MoS_2/C composite electrodes demonstrated improved electrochemical performance such as enhanced cycle stability and superior rate capability. Furthermore, we believe that our facile and effective approach to synthesize MoS_2/C composites can be extended to design and develop various transition metal-chalcogenides as promising and desirable anode candidates for SIBs.