Controllable Design of MoS₂ Nanosheets Anchored on Nitrogen‐Doped Graphene: Toward Fast Sodium Storage by Tunable Pseudocapacitance

Abstract

Transition-metal disulfide with its layered structure is regarded as a kind of promising host material for sodium insertion, and intensely investigated for sodium-ion batteries. In this work, a simple solvothermal method to synthesize a series of MoS nanosheets@nitrogen-doped graphene composites is developed. This newly designed recipe of raw materials and solvents leads the success of tuning size, number of layers, and interplanar spacing of the as-prepared MoS nanosheets. Under cut-off voltage and based on an intercalation mechanism, the ultrasmall MoS nanosheets@nitrogen-doped graphene composite exhibits more preferable cycling and rate performance compared to few-/dozens-layered MoS nanosheets@nitrogen-doped graphene, as well as many other reported insertion-type anode materials. Last, detailed kinetics analysis and density functional theory calculation are also employed to explain the Na - storage behavior, thus proving the significance in surface-controlled pseudocapacitance contribution at the high rate. Furthermore, this work offers some meaningful preparation and investigation experiences for designing electrode materials for commercial sodium-ion batteries with favorable performance.

Heterostructured TiO2 Spheres with Tunable Interiors and Shells toward Improved Packing Density and Pseudocapacitive Sodium Storage

“…[18][19][20] This effect is able to enhance both of the rate performance and capacity reversibility of advanced energy storage devices. [23][24][25][26][27] As far as we know, the relationship between pseudocapacitance and interior/shell adjustments of spherical materials has rarely been involved. [21,22] Very recently, several previous works present some effective approaches for promoting the pseudocapacitive Li + /Na + storage through structural design and optimization of electrode materials, such as oxygen vacancy creation of metal oxides, size-decreasing, and active facets exposing of nanosheets, interlayer spacing expansion of 2D materials.…”

“…After the first several cycles, the curves illustrate apparent high voltage plateaus and become well overlapped, suggesting much safer sodium storage by avoiding the dendritic growth, as well as favorable capacity reversibility. [24][25][26][27][28][29][35][36][37][38][39][40] The irreversible loss of capacity in these anodes can in some cases be offset by prelithiation/sodiation technologies. [41,42] Figure 3d demonstrates the cycling properties of the three as-prepared TiO 2 samples at low rate of 0.2 A g −1 .…”

Hierarchical Hollow‐Nanocube Ni−Co Skeleton@MoO3/MoS2 Hybrids for Improved‐Performance Lithium‐Ion Batteries

“…Additionally,ahigh specific surfacea rea of the nanostructured materials could form multiple SEI layers,which retarded electrolyte permeation and accelerated decompositiono ft he electrolyte. [28,35,52,[55][56][57] 3) The Li x MoS 2 intermediate phase, with metallicf eatures, could hugelyb oost the reaction kinetics. The dramatici ncrease in specific capacity may mainly be attributed to the following reasons:1 )Electrochemical delamination of the layered structure and expansion of the interlayers pacing decreased the diffusion resistanceo fl ithium ions.…”

Fe3O4/Nitrogen‐Doped Carbon Electrodes from Tailored Thermal Expansion toward Flexible Solid‐State Asymmetric Supercapacitors

“…[41] In addition, the abundant pores on in H-NCMs had also been retained even after annealing at 900 °C ( Figure 2f). [20] In addition, energy-dispersive X-ray (EDX) elemental distribution of NCM-A600 displayed the Fe, C, N, O element had been fully preserved and evenly distributed, as shown in Figure 2h-k and Figure S8 (Supporting Information), which implied a high density of potential active sites. [20] In addition, energy-dispersive X-ray (EDX) elemental distribution of NCM-A600 displayed the Fe, C, N, O element had been fully preserved and evenly distributed, as shown in Figure 2h-k and Figure S8 (Supporting Information), which implied a high density of potential active sites.…”

“…[17] NCMbased SCs can bridge the gap between conventional capacitors and cells, have been widely used in various areas due to their rapid energy transfer, long cycle life, sustained stability, and a wide range of working temperatures. [18] Moreover, after combination of transition metal compounds (TMCs) including metal oxides (e.g., MnO 2 , Fe 2 O 3 , CuO), [19] metal sulfides (MoS 2 ), [20] metal nitrides (e.g., TiN, Fe 2 N), [21] metal-organic frameworks, [22] and metal hydroxide (e.g., Ni(OH) 2 ), [23] the key faradic capacitance of NCM electrodes can be prominently enhanced. Among the TMCs, ferroferric oxide (Fe 3 O 4 ) is particularly promising since: [24] 1) a higher conductivity than other TMCs (σ = 2 × 10 4 S m −1 ); 2) a relatively low potential and a high theoretical capacity (≈346.5 mAh g −1 ) on the basis of the possible variation of iron's valence states (Fe 3+ ↔ Fe 0 ) in alkaline aqueous solution, which can deliver large voltage windows (≤−1.3 V vs Ag/AgCl) and high pseudocapacitance attributions; 3) ecofriendliness during the synthesis process, natural abundance, and compatibility.…”