Electrospinning Preparation And Lithium/sodium Storage Property Of WS₂/CNFs Composites

Transition metal dichalcogenides WS₂, with larger interlayer spacing and larger theory capacity than graphite, is a promising anode material for lithium batteries. However, suffered from drastic volume change and poor conductivity for ions and electrons, WS₂ generally showed a poor cycling stability and rate performance. Reducing the size of materials has been demonstrated an effective way to release the strain caused by ions insertion/ extraction. Simultaneously, a lager specific surface area would accompany with the reduction of sample volume, which can also introduce vast interfacial storage sites for ions and thus greatly contribute to the capacity. Besides, combining WS₂ with carbon materials is a feasible way to promote the conductivity of the materials.In this dissertation, we successfully prepared a hybrid composition by a simple and efficient electrospinning method in which few-/single-layer WS₂ nanoplates were uniformly embedded in CNFs, realizing the size reduction and conductivity enhancement in one-step method. The existence of carbon fibers enhance the conductivity, hinder the aggregation and growth of WS₂, and relieve the structural strain caused by the volume change, which improve the stability of the materials structure. While innumerable pores and large specific surface area brought by the 3D architecture made up of interconnected carbon nanofibers provide fast diffusion of Li+ and electrons. The electrochemical tests show a good electrochemical performance: The samples exhibit a first-cycle discharge/charge capacity of 941/756 mAh/g at 100 mA/g and maintain a capacity of 458 mAh/g after 100 cycles at 1 A/g. When used as anode materials for sodium batteries, it still shows good performance. However, the intercalation for Na+ is more difficult considering its bigger volume, which inducing lower capacity.The concertration and crystallinity of WS₂ in the composites are systematically studied, which are found to strongly influence the final electrochemical performance. Interestingly, the WS₂ samples of appropriate content and lowest crystallinity show the highest performance among all studied samples, which could result from the large interfacial capacity for ions due to their large availability and specific surface area. More interestingly, the inherent flexible attribute of electrospun nanofibers renders them a great potential in the utilization of binder-free anodes without any additives. Similar high discharge/charge specific capacity has been achieved and a promising application in flexible battery devices can be expected.