硫化锌/氮硫共掺杂碳纤维复合材料的制备及其储锂特性

ZnS Encapsulated in N/S Co-Doped Carbon Fiber as a Composite Material for Li Storage

作为锂离子电池负极材料,碳基材料性能稳定但比容量有限,金属硫化物比容量较高但存在结构不稳定、易溶于电解液等问题,通过引入碳材料包裹金属硫化物,可维持结构稳定并防止中间产物的溶解。将硫粉和乙酰丙酮锌加入到聚丙烯腈的有机溶液中,采用静电纺丝法及后续热处理,合成了碳包覆ZnS复合纤维。X射线光电子能谱(XPS)结果表明,硫不仅与锌反应生成了ZnS,还对碳纤维进行了掺杂。在扫描电镜(SEM)和高角环形暗场像(HAADF)测试中可观察到纤维为棒状,外层碳为氮硫共掺杂碳,内部包裹着直径为100 nm左右的ZnS颗粒。在拉曼测试中可以看出:碳的D峰与G峰的强度比(I_(D)/I_(G))达到1.35,表明碳纤维的无序程度较高。热分析结果表明,复合纤维中碳含量约为50%。电化学测试结果表明,ZnS@C在0.1 A/g的电流密度下首圈放电比容量高达834 mAh/g,单圈容量下降率仅有0.25%。在电流密度为1 A/g时,放电比容量可稳定于530 mAh/g,循环500圈基本无容量衰减。在1.0 mV/s扫速下,电极的赝电容贡献率达到77%,表现出良好的赝电容行为和优异的储锂特性。

For anode materials of lithium-ion batteries,the carbon-based ones can exhibit stable but limited specific capacity,while the metal sulfides can deliver much higher capacity but show poor structural stability.By introducing carbon materials to encapsulate the metal sulfides,the structural stability can be maintained and the dissolution of intermediate products can be prevented.In this paper,sulfur and zinc acetylacetonate were added to the organic solution of polyacrylonitrile,and carbon-coated ZnS composite fibers were then synthesized by electrospinning and subsequent heat treatment.Through X-ray photoelectron spectroscopy(XPS)test,it was found that sulfur not only reacted with zinc to generate ZnS,but also doped the carbon fibers.In scanning electron microscope(SEM)and high-angle annular dark-field imaging(HAADF)tests,it could be observed that the rod-shaped fibers were composed of nitrogen/sulfur co-doped out-layer carbon and ZnS particles wrapped in the fibers with a diameter of about 100 nm.In the Raman test,the intensity ratio of D to G peaks(I_(D)/I_(G) ratio)of carbon reached 1.35,indicating a high degree of disorder in the carbon fibers.The thermal analysis results indicated that the carbon content in the composite fiber was about 50%.In the electrochemical test,ZnS@C showed an initial capacity of 834 mAh/g at the current density of 0.1 A/g and the capacity decaying rate was only 0.25%for each cycle.At 1 A/g,the discharge capacity could be stabilized at 530 mAh/g for 500 cycles.At the scan rate of 1.0 mV/s,the capacitive contribution of the electrode could reach 77%,demonstrating good pseudocapacitive behavior and excellent lithium storage characteristics.