硫掺杂碳包覆Fe_(0.95)S_(1.05)纳米球复合材料的储钠性能

Sulfur-Doped Carbon-Coated Fe_(0.95)S_(1.05) Nanospheres as Anodes for High-Performance Sodium Storage

铁硫化物因其较高的理论容量,被认为是一种很有前途的钠离子电池负极材料。然而,铁硫化物在充放电过程中存在较大的体积变化,导致其倍率性能和稳定性较差。本文通过简单的一步法策略,制备了一种具有三维簇状结构的硫掺杂碳包覆的Fe_(0.95)S_(1.05)纳米球(Fe_(0.95)S_(1.05)@SC),并研究了其储钠性能。硫掺杂碳层可提高材料的导电率,缓解Fe_(0.95)S_(1.05)纳米球在反应过程中产生的体积膨胀,故提升了材料的稳定性。Fe_(0.95)S_(1.05)@SC的相互贯通的簇状结构,为电子和离子的传输提供了通道,使材料具备优异的倍率性能。在半电池体系中,Fe_(0.95)S_(1.05)@SC在0.1A·g^(-1)下循环100圈后,保留614.7 m Ah·g^(-1)的高比容量,10 A·g^(-1)下比容量仍可以达到235.7 m Ah·g^(-1)。在全电池体系中,在0.1和10 A·g^(-1)时,Fe_(0.95)S_(1.05)@SC的可逆容量分别为482.8和288.3 m Ah·g^(-1)。该材料具有良好电化学性能,在钠离子电池中具有广阔的应用前景。

Sodium-ion batteries(SIBs),featuring with adequate sodium resources,relatively high safety,and similar chemical properties between sodium and lithium,have been considered one of the most potential candidates to lithium-ion batteries(LIBs).However,the larger radii of sodium ions(vs.lithium ions)lead to sluggish diffusion kinetics of sodium ions,low storage capacity,and adverse volume variation during sodiation and desodiation.In particular,anode materials work well in LIBs have been proved ineffective in SIBs.Therefore,the development of cheap anode materials with remarkable performance is critical to the commercialization of SIBs.Despite the good conductivity and robust stability of carbon materials,they usually showcase moderate discharge capacity and poor rate performance in SIBs.Iron sulfides are considered promising anode materials for SIBs due to their high theoretical capacity.Nevertheless,iron sulfides exhibit severe volumetric expansion during charge and discharge,resulting in low rate performance and poor stability.In this regard,hybridizing carbon materials with iron sulfides to configure composite materials is an important way to improve the electrochemical performance of SIBs.Here,three-dimensional clusterstructured sulfur-doped carbon-coated Fe_(0.95)S_(1.05)nanospheres(Fe_(0.95)S_(1.05)@SC)are crafted by one-step annealing of ferrocene and sulfur powder,of which the implementation as anode of sodium ion batteries is reported.Scanning electron microscopy(SEM),transmission electron microscope(TEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)results confirm the successful synthesis of the Fe_(0.95)S_(1.05)@SC composite.The coated sulfur-doped carbon layer can improve the conductivity of the Fe_(0.95)S_(1.05)material and alleviate corresponding volume expansion during the reaction process,thus delivering a robust electrochemical stability.The interconnected cluster structures of Fe_(0.95)S_(1.05)@SC provide channels for the transport of electrons and ions,enabling the material excellent rate performance.Thanks to the unique structures of as-made Fe_(0.95)S_(1.05)@SC,when acting as anodes of SIBs,it demonstrates stable cycling performance and high rate performance.The electrochemical reaction process on Fe_(0.95)S_(1.05)@SC electrode is studied by cyclic voltammetry,validating that this electrode has good electrochemical reversibility.During the first few cycles of charging and discharging process,stable solid electrolyte interphase(SEI)layer forms on the surface of the carbon layer,which helps to avoid the direct exposure of Fe_(0.95)S_(1.05)to the electrolyte and prevent the material from inactivation by the dissolution or escape of the sulfur element within Fe0.95S1.0.In the half-battery system,after 100 cycles at 0.1 A·g^(-1),the high specific capacity of 614.7 m Ah·g^(-1)for Fe_(0.95)S_(1.05)@SC is retained,and the specific capacity at 10 A·g^(-1)can still reach 235.7 m Ah·g^(-1).In the full battery system,the reversible capacity at 0.1 and 10 A·g^(-1)is 482.8 and 288.3 m Ah·g^(-1),respectively.The as-made Fe_(0.95)S_(1.05)@SC with excellent electrochemical properties holds promise as anodes for sodium-ion batteries.