Flexible WS₂@CNFs Membrane Electrode with Outstanding Lithium Storage Performance Derived from Capacitive Behavior

Abstract

characteristics such as quantum confinement and surface effect, indicating great promise as LIB electrodes. [3,4] As a typical TMDs, WS 2 has gained tremendous attention because it possesses a higher theoretical specific capacity (433 mA h g −1 ) and a larger interlayer spacing of 0.64 nm than graphite, which contributes to more space for lithium-ion transport, consequently leading to superior property. [5,6] However, large volume change during charge/discharge process and poor conductivity lead to the decay of capacity and inferior rate performance, limiting its application in energy storage system. [7,8] To address this issue, many efforts have been devoted to the structure design such as hybridization with carbon materials and nanoengineering (such as WS 2 nanoplates in nitrogen-doped CNFs, WS 2 nanowires, WS 2 @graphene composites), [6,9,10] which are effective to buffer interior stress resulted from volume expansion, reduce structural pulverization, shorten ions transfer path, and inhibit agglomeration of materials. Moreover, electrospinning is one of the most effective ways to fabricate flexible membrane structures combining active materials with carbonaceous materials without complicated preparation process and the addition of binder that is electrically insulated and obstructive to ion transportation. [11] For instance, Zhang has reported flexible NiS/CNF and WS 2 /GCNF hybrids via electrospinning as anodes for LIBs with enhanced lithium storage property. [5,12] However, the electrochemical performance of most WS 2 composites reported is still limited by the sluggish reaction kinetics and inferior long-term stability.Capacitive processes that are related to atoms on or near the surface possess faster reaction kinetics and more stable cyclability, when compared with diffusion-controlled storage processes (insertion, conversion, and alloying) in traditional Li-ion storage applications. [13,14] Thus far, in addition to some active materials such as MnO 2 , Nb 2 O 5 , and RuO 2 with intrinsic capacitive behavior, extrinsic capacitive behavior with fast kinetics is also favorable for insertion-(TiO 2 , LiCoO 2 , LiMn 2 O 4 , etc.), conversion-(MoO 2 , V 2 O 5 , etc.), and alloying-type active materials for LIBs via surface and nanostructure engineering to create more reaction sites. [13,15,16] Thus, the design of LIB anode materials with capacitive behavior to induce outstanding electrochemical properties is increasingly imperative. However, Flexible electrodes have recently elicited attention due to their potential to be woven into textiles as flexible power supplies for wearable electronic devices. However, contemporary flexible electrodes generally suffer from the limited reaction kinetics and inferior stability. Here, a flexible WS 2 @CNFs membrane electrode is facilely fabricated via hydrothermal method and subsequent electrospinning to embed WS 2 nanosheets into interconnected framework of carbon nanofibers (CNFs). Benefitting from 3D porous architecture and good conductivity of CNFs, WS 2 @CNFs composit...

Molybdenum and tungsten chalcogenides for lithium/sodium-ion batteries: Beyond MoS2

“…2.1. WS 2 for lithium-ion batteries WS 2 with sandwiched S-W-S layers (interlayer spacing 0.618 nm) stacked together via weak van der Waals interaction has received tremendous attention for next-generation rechargeable LIBs due to its higher intrinsic electrical conductivity compared to MoS 2 , competitive theoretical capacity of 433 mA h g −1 (based on 4 mol of Li-ion insertion), and a high density of 7.6 g cm −3 resulting in a volumetric energy density 4 times higher than that of graphite [69,[74][75][76][77][78] . However, the electrical conductivity of pristine TMDs and electrode stability need to be further improved for practical application in high power/density energy storage devices.…”

“…The design of flexible electrodes with high conductivity, stable structure, superior electrochemical performance and robust mechanical property is of strong demand [106] . The incorporation with carbon fiber cloth is a facile and effective route, which includes carbon cloth, biomaterial-derived carbon paper or electrospun nonwoven conductive matrices [75,77,127] . For example, Hao's group designed a flexible anode for LIBs with metallic 1T@2H WS 2 nanosheet arrays stably anchored on cotton cloth-derived interlinked carbon fiber cloth (CFC).…”

Vertically Oriented Graphene Nanosheets for Electrochemical Energy Storage

“…Although widely used in portable electronic devices, some critical issues remain with LIB, e. g., low rate performance, poor cyclic stability, and safety problems, [71–73] that limit the development in the commercial market of electrical vehicles [7] . The key to high energy‐density LIB with a long cycle life and good safety is the development of high‐performance electrodes (anodes and cathodes) that can improve the performance of LIB to meet the increasing demand for energy in modern life [6,74,75] …”

Few-layer WS2nanosheets with oxygen-incorporated defect-sulphur entrapped by a hierarchical N, S co-doped graphene network towards advanced long-term lithium storage performances

“…16,17 What is worse, WS 2 is especially easy to restack through van der Waals interactions between S-W-S layers, which severely compromises the electrochemical properties. 18 To address the aforementioned disadvantages, one effective strategy is to combine WS 2 with carbonaceous material supports (carbon, 19 graphene, 20 carbon nanobers 21 and carbon nanotubes, 22 etc.). These carbonaceous materials possess not only the high electron conductivity to accelerate electron transfer, but also provide large specic surface area to accommodate the large volume expansion and promote electrolyte penetration during lithium storage processes.…”