MoS2 Nanosheets with Conformal Carbon Coating as Stable Anode Materials for Sodium-Ion Batteries

Ultrafast microwave synthesis of MoSSe@ graphene composites via dual anion design for long-cyclable Li-S batteries

Lithium-sulfur batteries (LSBs) have been increasingly recognized as a promising candidate for the next-generation energy-storage systems. This is primarily because LSBs demonstrate an unparalleled theoretical capacity and energy density far exceeding conventional lithium-ion batteries. However, the sluggish redox kinetics and formidable dissolution of polysulfides lead to poor sulfur utilization, serious polarization issues, and cyclic instability. Herein, sulfiphilic few-layer MoSSe nanoflake decorated on graphene (MoSSe@graphene), a two-dimensional and catalytically active hetero-structure composite, was prepared through a facile microwave method, which was used as a conceptually new sulfur host and served as an interfacial kinetic accelerator for LSBs. Specifically, this sulfiphilic MoSSe nanoflake not only strongly interacts with soluble polysulfides but also dynamically promotes polysulfide redox reactions. In addition, the 2D graphene nanosheets can provide an extra physical barrier to mitigate the diffusion of lithium polysulfides and enable much more uniform sulfur distribution, thus dramatically inhibiting polysulfides shuttling meanwhile accelerating sulfur conversion reactions. As a result, the cells with MoSSe@graphene nanohybrid achieved a superior rate performance (1091 mAh/g at 1C) and an ultralow decaying rate of 0.040 % per cycle after 1000 cycles at 1C.

Optimized Pinecone-Squama-Structure MoS2-Coated CNT and Graphene Framework as Binder-Free Anode for Li-Ion Battery with High Capacity and Cycling Stability

Extensive research has been conducted on the development of high-rate and cyclic stability anodes for lithium batteries (LIBs) due to their high energy density. Molybdenum disulfide (MoS₂) with layered structure has garnered significant interest due to its exceptional theoretic Li⁺ storage behavior as anodes (670 mA h g^-1). However, achieving a high rate and long cyclic life of anode materials remains a challenge. Herein, we designed and synthesized a free-standing carbon nanotubes-graphene (CGF) foam, then presented a facile strategy to fabricate the MoS₂-coated CGF self-assembly anodes with different MoS₂ distributions. Such binder-free electrode possesses the advantages of both MoS₂ and graphene-based materials. Through rational regulation of the ratio of MoS₂, the MoS₂-coated CGF with uniformly distributed MoS₂ exhibits a nano pinecone-squama-like structure that can accommodate the large volume change during the cycle process, thereby significantly enhancing the cycling stability (417 mA h g^-1 after 1000 cycles), ideal rate performance, and high pseudocapacitive behavior (with a 76.6% contribution at 1 mV s^-1). Such a neat nano-pinecone structure can effectively coordinate MoS₂ and carbon framework, providing valuable insights for the construction of advanced anode materials.

3D tremella-like nitrogen-doped carbon encapsulated few-layer MoS2 for lithium-ion batteries

MoS₂ is regarded as an attractive anode material for lithium-ion batteries due to its layered structure and high theoretical specific capacity. Its unsatisfied conductivity and the considerable volume change during the charge and discharge process, however, limits its rate performance and cycling stability. Herein, 3D tremella-like nitrogen-doped carbon encapsulated few-layer MoS₂ (MoS₂@NC) hybrid is obtained via a unique strategy with simultaneously poly-dopamine carbonization, and molybdenum oxide specifies sulfurization. The three-dimensional porous nitrogen-doped carbon served both as a mechanical supporting structure for stabilization of few-layers MoS₂ and a good electron conductor. The MoS₂@NC exhibits enhanced high rate performance with a specific capacity of 208.7 mAh g^-1 at a current density of 10 A g^-1 and stable cycling performance with a capacity retention rate of 85.7% after 1000 cycles at 2 A g^-1.

SiOC functionalization of MoS2 as a means to improve stability as sodium-ion battery anode

The development of feasible, scalable, and environmentally-safe electrode materials that provide stable cycling performance are critical for success of beyond lithium rechargeable batteries and supercapacitors. With respect to the sodium-ion battery (SIB) anodes constituting of transition metal dichalcogenides such as molybdenum disulfide (MoS₂), poor cycle stability and fast capacity degradation, due to low electronic conductivity and dissolution of chemical species in the electrolyte, hinders use of these promising layered materials as SIB anodes. Herein we report chemical functionalization in MoS₂ nanosheets with polymer-derived silicon oxycarbide or SiOC with the aim to preserve MoS₂ from dissolution in the SIB organic electrolyte, without compromising its role in sodiation and desodiation processes. Our results suggest that a MoS₂-SiOC composite electrode is effective in bringing improved cycle stability to sodium-ion cycling over neat MoS₂ even after 100 cycles.

A composite of ultra-fine few-layer MoS2 structures embedded on N,P-co-doped bio-carbon for high-performance sodium-ion batteries

Highly dispersed ultra-fine few-layer MoS₂ embedded on N/P co-doped bio-carbon composite (MoS₂-N/P-C) was synthesized and it delivers excellent high-rate long term cycling performance (175 mA h g⁻¹ after 2000 cycles at 5 A g⁻¹).

Nearly monodispersed MoS2 hierarchical architectures as superior anodes for electrochemical lithium-storage

In this paper, we developed a facile approach to synthesize well-dispersed 3D hierarchical porous MoS₂ architectures with assistance of polyacrylate and demonstrated their applications in lithium ion batteries (LIBs). It was confirmed that the uniform flower-like MoS₂ architectures were assembled by nanosheets comprising about ∼10 stacking layers. Polyacrylate was revealed to have a significant impact on controlling the formation of the uniform hierarchical flower-like architectures with desirable dispersity. It was believed that the polyacrylate could direct assembly of the MoS₂ nanosheets into hierarchical structures and could well stabilize and disperse MoS₂ architectures. Furthermore, a stable cycling capability (839 mAh g^-1 at 0.1 A g^-1 after 120 cycles) and superior rate ability of the MoS₂ architectures were achieved as anodes for LIBs. This remarkably enhanced electrochemical property could be ascribed to their beneficial structural features and surface-dominated capacitive contribution.

An ultra-small few-layer MoS2-hierarchical porous carbon fiber composite obtained via nanocasting synthesis for sodium-ion battery anodes with excellent long-term cycling performance

Rational fabrication of anode electrodes for sodium-ion batteries remains a challenge due to the problem of sluggish Na+ diffusion kinetics, large volume expansion etc. Significant efforts, such as fabricating carbon composites and novel nanostructures, have been devoted to the development of anode materials. Herein, an ultra-small few-layer MoS2 nanostructure confined on a hierarchical porous carbon fiber composite was synthesized through the nanocasting route using a novel hierarchical porous carbon fiber as the template. As an anode material, the composite displays outstanding electrochemical performance for sodium-ion batteries. For instance, it delivers high reversible capacities (491 mA h g-1 after 50 cycles at 0.1 A g-1), high rate performance (387 mA h g-1 at 2 A g-1) and long-term cycling stability (234 mA h g-1 at 1 A g-1 after 3000 cycles). Note that it shows one of the best long-term cycling properties reported to date for MoS2-based anode materials for sodium-ion batteries. This regulation strategy may offer new insights into the fabrication of high-performance anode materials for sodium-ion batteries.

Unveiling the structural evolution of 1T SnS2 anode upon lithiation/delithiation by TEM

Pure 1T SnS₂ was synthesized by the hydrothermal method and its atomic image was obtained. The Li-storage performance and its structure evolution were revealed by ex situ TEM.

Ultrafast Sodium/Potassium-Ion Intercalation into Hierarchically Porous Thin Carbon Shells

The large-scale application of sodium/potassium-ion batteries is severely limited by the low and slow charge storage dynamics of electrode materials. The crystalline carbons exhibit poor insertion capability of large Na⁺ /K⁺ ions, which limits the storage capability of Na/K batteries. Herein, porous S and N co-doped thin carbon (S/N@C) with shell-like (shell size ≈20-30 nm, shell wall ≈8-10 nm) morphology for enhanced Na⁺ /K⁺ storage is presented. Thanks to the hollow structure and thin shell-wall, S/N@C exhibits an excellent Na⁺ /K⁺ storage capability with fast mass transport at higher current densities, leading to limited compromise over charge storage at high charge/discharge rates. The S/N@C delivers a high reversible capacity of 448 mAh g^-1 for Na battery, at the current density of 100 mA g^-1 and maintains a discharge capacity up to 337 mAh g^-1 at 1000 mA g^-1 . Owing to shortened diffusion pathways, S/N@C delivers an unprecedented discharge capacity of 204 and 169 mAh g^-1 at extremely high current densities of 16 000 and 32 000 mA g^-1 , respectively, with excellent reversible capacity for 4500 cycles. Moreover, S/N@C exhibits high K⁺ storage capability (320 mAh g^-1 at current density of 50 mA g^-1 ) and excellent cyclic life.

Nitrogen-Doped Carbon Coated WS2 Nanosheets as Anode for High-Performance Sodium-Ion Batteries

Due to the cost-effectiveness of sodium source, sodium-ion batteries (SIBs) have attracted considerable attention. However, SIBs still have some challenges in competing with lithium-ion batteries for practical applications. Particularly, the high rate capability and cycling stability are posing big problems for SIBs. Here, nitrogen-doped carbon-coated WS₂ nanosheets (WS₂/NC) were successfully synthesized by a high-temperature solution method, followed by carbonization of polypyrrole. When used as anode electrodes for SIBs, WS₂/NC composite exhibited high-rate capacity at 386 and 238.1 mAh g⁻¹ at 50 and 2,000 mA g⁻¹, respectively. Furthermore, even after 400 cycle, the composite electrode could still deliver a capacity of ~180.1 mAh g⁻¹ at 1,000 mA g⁻¹, corresponding to a capacity loss of 0.09% per cycle. The excellent electrochemical performance could be attributed to the synergistic effect of the highly conductive nature of the nitrogen-doped carbon-coating and WS₂ nanosheets. Results showed that the WS₂/NC nanosheets are promising electrode materials for SIBs application.

Synthesis and electrochemical sodium-storage of few-layered MoS2/nitrogen, phosphorus-codoped graphene

Few-layered molybdenum disulfide/nitrogen, phosphorus co-doped graphene composites are synthesized by a quaternary phosphonium salt-assisted hydrothermal and annealing procedure. The prepared composites are analyzed by x-ray powder diffraction, x-ray photoelectron spectra, scanning electronic microscopy, transmission electronic microscopy, Raman spectra and nitrogen adsorption and desorption. Experimental results indicate that the MoS₂ nanosheets are of few-layered and defective structures and are well anchored on flexible conductive nitrogen, phosphorus co-doped graphene to constitute mesoporous composites with increased surface areas. Benefiting from the structural merits as well as surface-dominated pseudocapacitive contribution, the composite electrode presents a high electrochemical sodium storage capacity that arrives at 542 mAh g^-1 at a current density of 100 mA g^-1 with an excellent cyclability. Moreover, a superior high-rate capability can also be achieved.