SnS nanoparticles anchored on nitrogen-doped carbon sheets derived from metal-organic-framework precursors as anodes with enhanced electrochemical sodium ions storage

In-depth insight into the effects of oxygen vacancies on the excellent Li+-storage performances of Cu2Nb34O87-x/N-doped carbon composite

Wadsley-Roth phase niobates demonstrate significant Li+-storage advantages. Even though their Nb5+ can fully transform into Nb4+ during lithiation process, however, only partial Nb4+ can further convert to Nb3+, leading to much lower practical capacities than the theoretical values according to the two-electron transfer per Nb5+. The specific mechanism to improve their conversion ratio of Nb4+ to Nb3+ during lithiation process has rarely been reported so far. Herein, the ultrafine oxygen-deficient Cu2Nb34O87-x nanoparticles are closely connected by the N-doped carbon-based 3D conductive framework to form a cloud-like Cu2Nb34O87-x/N-doped carbon composite (denoted as VU-CNO-NC) with nanoaggregate structure and porous structure. Based on density functional theory (DFT) calculations and ex situ X-ray photoelectron spectrometer (XPS), the oxygen vacancies in VU-CNO-NC can catalyze the conversion of Nb4+ to Nb3+ during lithiation process, which significantly enhance the conversion ratio of Nb4+ to Nb3+ to generate much higher capacity. This effect of oxygen vacancies has rarely been reported so far. Moreover, the oxygen vacancies, ultrafine primary nanoparticles, 3D conductive framework, porous structure, and nanoaggregate structure synergistically endow VU-CNO-NC with fast Li+-storage kinetics and highly stable structure. Consequently, VU-CNO-NC not only shows high capacity (287 mAh g-1 after 500 cycles at 1 C and 181 mAh g-1 after 1000 cycles at 10 C) and excellent rate performance as anode material of lithium-ion batteries, but also endows hybrid lithium-ion capacitor with high energy density (126 Wh kg-1 at 175 W kg-1) and remarkable capacity retention (87.3 % after 9000 cycles at 2 A g-1), demonstrating great application prospect.

Interface engineering of metal sulfides-based composites enables high-performance anode materials for sodium-ion batteries

Metal sulfides (MSs) have attracted much attention as anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity. However, the unsatisfactory electrochemical performance induced by the huge volume change and sluggish kinetics hampered the practical application of SIBs. Herein, guided by the heterostructure interface engineering, novel multicomponent metal sulfide-based anodes, including SnS, FeS, and Fe3N embedded in N-doped carbon nanosheets (SnS/FeS/Fe3N/NC NSs), have been synthesized for high-performance SIBs. The as-prepared SnS/FeS/Fe3N/NC NSs with abundant heterointerfaces and high conductivity of N-doped carbon nanosheet matrix can shorten the Na+ diffusion path and promote reaction kinetics during the sodiation/desodiation process. Moreover, the presence of Fe3N can promote the reversible conversion of SnS and FeS during the cycling process. As a consequence, when evaluated as anode materials for SIBs, the SnS/FeS/Fe3N/NC NSs can maintain a high sodium storage capacity of 473.6 mAh g-1 after 600 cycles at 2.0 A g-1 and can still provide a high reversible capacity of 537.4 mAh g-1 even at 5.0 A g-1 This discovery offers a novel strategy for constructing metal sulfide-based anode materials for high-performance SIBs.

Flexible Self-Supporting MOF-Based Bean Pod Cube Hollow Nanofibers for Ultralong Cycling and High Rate Na Storage

Sodium-ion batteries (SIBs) have garnered significant attention due to their potential as an emerging energy storage solution. Tin sulfide (SnS) has emerged as a promising anode material for SIBs due to its impressive theoretical specific capacity of 1022 mA h g-1 and excellent electrical conductivity. However, its practical application has been hindered by issues such as large volume expansion, which adversely affects cycling stability and rate performance during the charge/discharge processes. In this study, a novel approach to address these issues by synthesizing the bean pod cube hollow metal-organic framework (MOF)-SnSx/NC@N-doped carbon nanofibers through a process involving electrospinning, PDA coating, and calcination. The Sn-MOF serves as a self-sacrificing template, facilitating the simultaneous dissociation of MOF and polymerization of dopamine, leading to the creation of hollow intermediates that retain tin components. Subsequent sulfidation results in the integration of the hollow MOF-SnSx/NC nanoparticles within 3D nitrogen-doped carbon nanofibers, forming the distinctive bean pod cube composite structure. This unique configuration effectively shortens the diffusion path and mitigates volume expansion for sodium ions, ultimately yielding an exceptional high rate performance of 130 mA h g-1 (10 A g-1) and an ultralong cycling performance of 328 mA h g-1 even after 3500 cycles (2 A g-1) as the anode for SIBs.

Metal-Organic Assembly Strategy for the Synthesis of Layered Metal Chalcogenide Anodes for Na+ /K+ -Ion Batteries

Layered transition metal chalcogenides (MX, M=Mo, W, Sn, V; X=S, Se, Te) have large ion transport channels and high specific capacity, making them promising for large-sized Na⁺ /K⁺ energy-storage technologies. Nevertheless, slow reaction kinetics and huge volume expansion will induce an undesirable electrochemical performance. Numerous efforts have been devoted to designing MX anodes and enhancing their electrochemical performance. Based on the metal-organic assembly strategy, nanostructural engineering, combination with carbon materials, and component regulation can be easily realized, which effectively boost the performance of MX anodes. In this Review, we present a comprehensive overview on the synthesis of MX nanostructure using the metal-organic assembly strategy, which can realize the design of MX nanostructures, based on self-sacrificial templates, host@guest tailored templates, post-modified layer and derivative templates. The preparation routes and structure evolution are mainly discussed. Then, Mo-, W-, Sn-, V-based chalcogenides used for Na⁺ /K⁺ energy storage are reviewed, and the relationship between the structure and the electrochemical performance, as well as the energy storage mechanism are emphasized. In addition, existing challenges and future perspectives are also presented.

Pd-SnO2/In2O3 with a Unique Structure for the Ultrasensitive Detection of Triethylamine near Room Temperature

Triethylamine (TEA) is a serious threat to people's health, and it is still a challenge to detect TEA at ppb level near room temperature (RT). Herein, we developed a simple, low-cost, low-temperature, and ultra-sensitive TEA sensor based on Pd-SnO₂/In₂O₃ composites. First, SnO₂ nanoparticles were obtained by the pyrolysis of Sn-MOF@SnO₂ precursor (MOF: metal organic framework), and Pd-SnO₂/In₂O₃ composites were prepared by further compounding and doping. The results show that the Pd-SnO₂/In₂O₃ sensor is highly sensitive to TEA gas at near RT (at 60 °C, the sensor response to 10 ppm TEA is 12,000, the response/recovery (res/rec) time is 51 s/493 s, and at 30 °C, the response value also reaches 1380, the res/rec time is 66 s/610 s), along with good selectivity, stability, and moisture resistance. Even at 10 °C operating temperature and 75% relative humidity (RH) in a low-temperature and high-humidity environment, it still maintains a high sensitivity of over 1000 to 10 ppm TEA, which shows great application potential in TEA detection. The reason for the enhanced performance of the 0.5%Pd-SnO₂/In₂O₃ sensor can be attributed to a large number of adsorbed oxygens on the unique structure of the material, the good charge transfer ability of the n-n-type heterojunction between SnO₂ and In₂O₃, the chemical sensitization and electronic sensitization of Pd nanoparticles, and the catalytic spillover effect. This work will provide a new approach for preparing sensors with good comprehensive properties, making full use of the advantages of the material structure-activity relationship.

Nanoconfined bimetallic sulfides (CoSn)S heterostructure in carbon microsphere as a high-performance anode for half/full sodium-ion batteries

The development of high-capacity anode materials is crucial for sodium-ion batteries. Alloy-type anode materials have attracted tremendous attention due to their high theoretical capacities. Nonetheless, the realizations of high capacity and remarkable cycling stability are actually hindered by the sluggish reaction kinetics of sodium storage. Here, we report a binary metal sulfides CoS@SnS heterostructure confined in carbon microspheres (denoted as (CoSn)S/C) through a facile hydrothermal reaction combined with annealing treatment. The (CoSn)S/C with micro/nanostructure can shorten ion diffusion length and increase mechanical strength of electrode. Besides, the heterogeneous interface between CoS and SnS can improve the inherent conductivity and favor the rapid transfer of Na⁺. Benefitting from these advantages, (CoSn)S/C composite exhibits a high reversible capacity of 463 mAh g^-1 and superior durability (368 mAh g^-1 at 2 A g^-1 after 1000 cycles). Notably, the assembled Na₃V₂(PO₄)₃//(CoSn)S/C full cell delivers a reversible capacity of 386 mAh g^-1 at 0.2 A g^-1, proving that the (CoSn)S/C is a promising anode material for sodium-ion batteries. The density functional theory (DFT) calculations unveil the mechanism and significance of the constructed CoS@SnS heterostructure for the sodium storage at atomic level. This work provides an important reference for in-depth understanding of reaction kinetics of bimetallic sulfides heterostructure.