Unlock the Potassium Storage Behavior of Single‐Phased Tungsten Selenide Nanorods via Large Cation Insertion

Abstract

of KEES was severely hindered by the lack of suitable anodes that can endure the structure degradation during the reversible insertion of large size of K-ions (1.38 Å). [6][7][8][9] So far, various electrode materials, such as carbonaceous materials, K-alloying materials, metal oxides, and MXene, have been studied widely as battery-type anodes. [10][11][12] However, the research of KEESs is still in its early stages, and the development of suitable anode materials with high-rate capability still remains a great challenge. [13][14][15] 2D layered transition metal dichalcogenides (2D TMDs), including sulfides (e.g., MoS 2 , VS 2 , and ReS 2 ) and selenides (e.g., MoSe 2 , VSe 2 , and NbSe 2 ), have attracted attention as anode materials for K-ion batteries owing to their high theoretical capacities and tunable interlayer spacing. [16,17] Among the 2D TMDs, tungsten selenium (WSe 2 ) exhibits several attractive features for high-capacity and high-rate K storage. [18,19] The relatively large interlayer spacing of 0.678 nm for its (002) plane affords advantages for the (de) insertion of K + and the volume change during repeated cycling. Compared with Li + and Na + (>1.5 V), the relatively low potential plateau of the electrochemical K-(de)intercalation into WSe 2 (<1.0 V) is beneficial for the high working voltage of full cells, thereby improving the energy density of KEESs. [20,21] During the past several years, several precious works involved in the improvement of WSe 2 -based electrodes were mainly focused on constructing reasonable nanostructure and carbon coating. [18][19][20] However, evident structural distortion derived from the large K-ion inserted in these electrodes is still inevitable, particularly after long cycles, resulting in drastically decayed cycling performance. In addition, the sluggish K-ion diffusion in WSe 2 due to the limited interlayer space causes poor rate capability, suggesting that the accommodation of the bulky K + is less favorable than Li + and Na + in such compact layered structures.Clearly, the expansion and improvement of these studies on K-ion storage remain to be promoted, which is crucial in determining whether the KEES goals of high reversible capacity, superior rate capability, and favorable cycling stability can be achieved for WSe 2 materials. Previous research has demonstrated that large cations such as K + , NH 4 + , and polyaniline can be inserted into lattice during the synthesis process of 2D TMDs, layered oxides, oxyhydroxides, and olivines, resulting in increased electrochemically active surface area, lattice spacing Metal chalcogenide anodes with a layered structure have been regarded as potential K-based electrochemical energy storage devices with high energy density for large-scale energy storage applications. However, their development is impeded by the slow K-ion transport kinetics and poor structural stability. In this work, the energy-storage behavior is investigated first and decisively associated them with the capacity-degradation of the promising layer-struct...

Defect-engineered WSxSe2−x nanocrystals anchored on selenized polyacrylonitrile fibers toward high-performance sodium/potassium-ion batteries with a wide working temperature range

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“…As shown in Figure 4c,d, the FCR electrode has an average reaction impedance of 2.65/4.37 (ohm g) during discharge/charge, which is less than the reaction impedance exhibited by the FO electrode (3.44/4.84 ohm g). [31,53,54] FCR electrodes exhibit enhanced interfacial charge transfer, lithiumion migration kinetics, and reduced reaction impedance, mainly due to the built-in electric field created by the construction of the heterostructure to accelerate charge and lithium-ion transfer. At the same time, the increased specific surface, the unique isotropic porous structure, and the reduced particle size shorten the lithium-ion diffusion path, promote electrolyte infiltration, and increase the reactive sites.…”

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