| As international tensions lead to a growing energy crisis,it has prompted the rapid development of new energy technologies.Up to now,lithium-ion batteries have become the mainstream battery technology for electric cars,smartphones,laptops and other portable electronic devices.It is especially important to develop lithium-ion batteries with higher performance,safety,environmental protection and long service life.However,traditional graphite anode materials have a low theoretical capacity(372 m Ah g-1)and are unable to meet the high specific capacity and high energy density storage device requirements needed in modern life.Two-dimensional materials with graphite-like structures,such as tin sulfides（Sn Sx,x=1,2）,have been considered promising lithium-ion battery anode materials due to their abundant sources and high theoretical specific capacity(645 and 782m Ah g-1).However,the large volume change caused by the Li-Sn alloying reaction results in a short cycle life and rapid capacity decay of lithium-ion batteries,greatly limiting the large-scale practical application of tin sulfides.Therefore,this study composite tin sulfides with different fiber materials,taking advanta ge of the low cost,rich pore structure,and large specific surface area of fiber materials,to min imize the volume effect during the charging and discharging process and improve its electroch emical performance.This study mainly uses the solvothermal method combined with high-te mperature calcination technology to prepare Sn S2/hollow carbon fiber（CKF）,Sn Sx/flexible ca rbon nanoweb（CNWF）,and Sn S2/graphene/CNWF composite electrode materials.The morp hology and structural characterization of the composite materials were systematically studied,and their lithium storage performance was investigated.The main research contents are as foll ows:Three different loading amounts of Sn S2/CKF composite materials were prepared by combining the solvothermal method and high-temperature calcination technology.The structure and morphology of Sn S2/CKF were analyzed using characterization techniques such as X-ray diffraction（XRD）,thermal gravimetric analysis（TG）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and X-ray photoelectron spectroscopy（XPS）.The results showed that Sn S2nanosheets were uniformly fixed on the fiber surface,and the different loading amount composite materials maintained a good fiber morphology and abundant pore structure.When used as a lithium-ion battery anode material,the one-dimensional fiber structure can effectively shorten the lithium-ion and electron transport paths,increase the contact area between the electrolyte and electrode material,and promote ion and electron transport.The first charge/discharge specific capacities of Sn S2/CKF-1,Sn S2/CKF-2,and Sn S2/CKF-3 composite electrodes were 990/110,1200/1357,and 950/1167m Ah g-1,respectively.After 200 cycles,the reversible specific capacities were 606,778,and576m Ah g-1,respectively.Among them,the Sn S2/CKF-2 composite anode material exhibited the best electrochemical performance,mainly due to the more uniform loading and distribution of Sn S2.To avoid shortening the fiber diameter during the grinding process and to study the flexible electrode,this study used a three-dimensional nonwoven fabric as a substrate and combined solvent thermal and calcination techniques to uniformly load tin-based sulfides on the fiber surface,obtaining Sn S2/CNWF composite fibers and Sn S/CNWF composite fiber materials with different loading amounts.The morphology and structural characteristics of the composite fibers were analyzed using physical characterization techniques such as XRD,TG,SEM,DTG,and TEM.The electrochemical results showed that the negative electrode material Sn S2/CNWF-2 exhibited the best lithium storage performance among the four samples.The first week charge-discharge specific capacity at a current density of 0.1 A g-1was 1227/1657m Ah g-1,and the first cycle coulombic efficiency was 74%.After 200 cycles,the reversible specific capacity was 809 m Ah g-1.When the Sn S2/CNWF-2 composite material was assembled into a flexible battery,it exhibited high mechanical flexibility and electrochemical performance,recovered its original shape after bending,and was not affected,demonstrating the high practical application value of the composite material.Finally,the combination of Sn S2/CNWF and graphene was achieved by hydrothermal method and different encapsulation methods,resulting in the production of Sn S2/graphene/CNWF and graphene/Sn S2/CNWF composite electrode materials.The morphology and structural characteristics of these materials were analyzed through a series of physical characterization techniques.The negative electrode material Sn S2/graphene/CNWF exhibited the best electrochemical performance in half-cell testing,with a first-week charge-discharge specific capacity of 1503/2824 m Ah g-1at a current density of 0.1 A g-1.After 200 cycles,the reversible specific capacity was 1207 m Ah g-1.Large-rate cycling performance testing was also conducted,with reversible specific capacities of 650,370,and368 m Ah g-1achieved after cycling 200 times at current densities of 1,2,and 5 A g-1,respectively,demonstrating excellent large-rate cycling performance.Based on these findings,the Sn S2/graphene/CNWF negative electrode material was assembled with LICo O2positive electrode material into a full battery to explore the practical application prospects of the negative electrode material.The full battery exhibited a first-week charge-discharge specific capacity of 1682 and 1831 m Ah g-1,respectively,at a current density of 0.1 A g-1,with a first-week Coulombic efficiency of 91.8%.After 150 cycles,the reversible specific capacity was 480 m Ah g-1.The excellent electrochemical performance is attributed to the three-dimensional network structure composed of layered graphene and carbon fibers,which provides dual buffering effects and more buffering space for the volume expansion of active materials during charge-discharge processes. |
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