Study On Preparation And Electrochemical Performance Of Sulfide Anode Materials

Lithium-ion batteries play an important role in human’s daily life due to the advantage of high capacity,safety,and convenience.The representative graphite-based commercial lithium-ion battery anode materials doesn’t meet the requirements of large-scale energy storage devices,power energy devices for fast charge and discharge,high energy density and power density,as well as higher safety performance because of the low theoretical specific capacity(～372 m Ah·g^-1).Therefore,it is urgent to develop the alternative anode materials with better performance.Metal sulfides own the high specific capacity and flat charge discharge platform,and have attracted abundant attention However,the poor conductivity,large volume change and the dissolution of lithium polysulfide hinder the commercial development of metal sulfides in the field of lithium-ion batteries.In this work,micro-nano metal sulfide composites with special structures were prepared by a facile and low cost method,and the cycle performance and rate performance were improved.The details are as follows:（1）Preparation of core-shell C@CuS nanocomposites and its lithium-storage performance study.Core-shell C@CuS nanocomposites was successfully prepared by a simple one-step precipitation method.In this process,the carbon spheres act as templates to realize the heterogeneous nucleation and then the CuS nanoparticles were growth on the templates.As the anode material of lithium-ion battery,C@CuS composites show novel cycling performance stability and rate performance.it delivers a reversible capacity of 817.6 m Ah·g^-1 at current density of 100 m A·g^-1 after 100 cycles and superior rate capability of 314 m Ah·g^-1 at 5 A·g^-1.The improvement of lithium-storage performance is attributed to the unique core-shell structure of C@CuS composite.Especially,the carbon core not only improves the conductivity of composite,reduce its volume expansion and prevent the agglomeration of CuS nanoparticles,but also effectively adsorbs polysulfides,and prevent their dissolution.（2）Preparation of core-shell C@SnS₂ nanocomposites and its lithium-storage performance study.C@SnS₂ composite was successfully prepared by one-step hydrothermal method.SnS₂nanosheets in the composites are heterogeneous nucleated and grown on the surface of carbon spheres.The lithium-storage performance of C@SnS₂ composite is obviously better than that of pure SnS₂.C@SnS₂ composite shows superior cycling capability of 817.6 m Ah·g^-1 at 100m Ah·g^-1 after 100 cycles and long-term cycling capacity of 442.3 m Ah·g^-1 at 1 A·g^-1 after 600cycles.The excellent lithium-storage performance is attributed to the synergistic effect between SnS₂ nanosheets and carbon spheres.The carbon spheres not only could effectively adsorb polysulfides to prevent the shuttle effect,but also can facilitate the charge transfer and prevent the aggregation of SnS₂ nanosheets during discharge/charging.In addition,the gap between SnS₂nanosheet and carbon ball can effectively adjust the volume expansion during lithium intercalation.（3）Preparation of FeS₂/Ti₃C₂ nanocomposites and its lithium-storage performance study.Iron oxide/Ti₃C₂ precursor was prepared through precipitation method,and Fe S₂/Ti₃C₂ composite was successfully prepared by later vulcanization treatment.The Fe S₂ nanoparticles are uniformly dispersed on the surface of Ti₃C₂ Mxenes nanosheets.As anode material of lithium ion battery,the Fe S₂/Ti₃C₂ composites show excellent cycle performance and rate performance.The Fe S₂/Ti₃C₂ composite exhibits superior cycling capability of 1083 m Ah·g^-1 at a current density of100 m A·g^-1 after 150 cycles and long-term cycling capacity of 523 m Ah·g^-1 at 1 A·g^-1 after 800cycles.The excellent electrochemical properties of the Fe S₂/Ti₃C₂ composite benefit from the synergistic effect of Fe S₂ nanoparticles and Mxenes nanosheets.The Fe S₂ nanoparticles can prevent the accumulation of Ti₃C₂ Mxenes nanosheets.The Mxenes with excellent mechanical and electrical properties can prevent the aggregation of Fe S₂ nanoparticles,improving the conductivity of composite and alleviating the volume change caused by lithium intercalation during the cycle.