A 3D Trilayered CNT/MoSe₂/C Heterostructure with an Expanded MoSe₂ Interlayer Spacing for an Efficient Sodium Storage

Abstract

attention because of its low cost and abundant supply of sodium. [1][2][3] However, because of its narrow interlayer spacing ≈0.34 nm, the larger size of Na + compared to Li + makes it difficult if not unsuitable for intercalation in graphite, which is commercially employed for LIB. [4][5][6] Further, the large radius of Na + in SIB electrodes produces sluggish electrochemical kinetics, provides higher diffusion barriers, and causes large volume expansion which leads to low rate capability and poor cyclic stability. [7,8] The ionization potential of Na + is also lower than Li + which results in a lower operating voltage and consequently, a lower energy density. [9] A lot of efforts in the development of advanced anode materials for SIBs have been proposed to address these issues.Recently, 2D transition metal dichalcogenides (TMDCs) have received considerable attention in electrochemical energy storage and conversion devices due to their layered structure, and the favorable electronic, chemical, and mechanical properties and stability. [10][11][12] TMDCs such as MoS 2 are often considered a promising anode candidate for LIBs. [13] However, when MoS 2 is employed in SIBs, it displays a lower capacity and a poor cyclic stability as a result of the low intrinsic conductivity and the small interlayer distance (≈0.62 nm). [14] In contrast, MoSe 2 possesses a slightly larger interlayer distance (≈0.64 nm) and better electrical conductivity due to small bandgap (≈1.1 eV). Moreover, it possesses higher theoretical capacity (≈422 mAh g −1 ) [10,15] than graphite (≈35 mAh g −1 ) [6] which makes it one of the most promising TMDC candidates for SIBs. However, the practical applications of MoSe 2 as an anode is limited by capacity fading due to the large volume expansion during long charging/discharging processes and the poor rate capability due to the low intrinsic electrical conductivity. [10] Modifying the nanostructure of the SIB electrodes can often solve some of these problems. For example, expanding the interlayer distance of MoSe 2 can lead to an improvement of the Na + storage and reducing the Na + diffusion barrier energy can enhance the reaction kinetics for the Na + intercalation/deintercalation. [16] Due to the high surface energy and weak van der Waal interactions between layers, Freestanding composite structures with embedded transition metal dichalcogenides (TMDCs) as the active material are highly attractive in the development of advanced electrodes for energy storage devices. Most 3D electrodes consist of a bilayer design involving a core-shell combination. To further enhance the gravimetric and areal capacities, a 3D trilayer design is proposed that has MoSe 2 as the TMDC sandwiched in-between an inner carbon nanotube (CNT) core and an outer carbon layer to form a CNT/ MoSe 2 /C framework. The CNT core creates interconnected pathways for the e − /Na + conduction, while the conductive inert carbon layer not only protects the corrosive environment between the electrolyte and MoSe 2 but also is fully tunable fo...

Hierarchical Tubular‐Structured MoSe2 Nanosheets/N‐Doped Carbon Nanocomposite with Enhanced Sodium Storage Properties

“…The peaks at 0.53 and 0.20 Vw ere attributed to Na + insertion into the MoSe 2 interlayer to form Na x MoSe 2 and ac onversion reactiont of orm Mo nanocrystals and the Na 2 Se matrix, as well as the formationo fasolid-electrolytei nterphase (SEI) layer,r espectively. [21][22][23]40] The peak at 0.01 Vw as attributedt oN a + insertion into NC. [25,64,65] In the first anodic scan, three peaks at 0.10, 1.77, and 2.17 were observed.…”

“…Recently, several research groups have attempted to maximize the sodium‐ion storage properties of anodes by integrating the two strategies mentioned above . This could significantly improve the structural and physical properties of electrode materials to achieve high electrochemical performance.…”

“…[6][7][8] Var-ious strategies have been proposed to address these issues. [4,[9][10][11] The incorporation of MoSe 2 into conductive carbon materials has been demonstrated as an effective method to address the aforementioned disadvantages; [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] this enhances the electrical conductivity and inhibits volumec hange of the electrode materials and stackingb etween interlayers. In addition, the introduction of nitrogen into the carbon materialc an modulate the electronic structure and increase chemical activity,w hich can further enhancet he sodium storage properties of the electrode materials.…”

“…[34][35][36][37][38] Recently,s everal research groups have attempted to maximize the sodium-ion storage properties of anodesb yi ntegrating the two strategiesm entioned above. [18][19][20][21][22][23][24][25][26][27][28][39][40][41][42][43] This could significantly improve the structural and physicalp ropertieso f electrode materials to achieve high electrochemical performance. For example, Tu and co-workersp repared 3D carbon-MoSe 2 -reducedg raphene oxide composites through a facile hydrothermalm ethod.…”

Construction of 1T‐MoSe2/TiC@C Branch–Core Arrays as Advanced Anodes for Enhanced Sodium Ion Storage

“…[11] Because of the low intrinsic conductivity of 2H-MoS 2 and its small interlayer distance ( % 0.62 nm), 2H-MoS 2 anodesdisplay lower capacity and poor cycling stability. [12,13] In contrast, 1T-MoSe 2 possessesaslightly larger interlayer distance ( % 0.64 nm), better electrical conductivity due to as mall band gap ( % 1.1 eV), [14] andh igh theoretical capacity ( % 422 mAh g À1 ). [15] Therefore, 1T-MoSe 2 shows greater applica-The use of active sites and reaction kinetics of MoSe 2 anodes for sodium ion batteries( SIBs) are highlyr elated to the phase components (1T and 2H phases)a nd electrode architecture.…”