In-situ synthesis of FeS/N, S co-doped carbon composite with electrolyte-electrode synergy for rapid sodium storage

Construction of three-dimensional hierarchical nest-like NiS2 with efficient stress dissipation for superior sodium storage

Transitional metal sulfides (TMSs) with high theoretical capacities are promising anode materials for sodium-ion batteries (SIBs). However, the low conductivity and large volume change during charge/discharge processes lead to poor rate capability and inferior cycling stability. In this work, we constructed three-dimensional hierarchical NiS2 microspheres by hydrothermal method followed by sulfurization. With polyvinylpyrrolidone (PVP) as a directing agent, NiS2 nanosheets orderly stack concentrically with an opening in the center, giving rise to a nest-like structure. By using PVP with different molecular weight, different morphologies of flower-like or solid NiS2 microspheres can be obtained. Finite element analysis (FEA) suggests that the unique nest-like structure can effectively dissipate the stress and suppress the volume variation during sodium insertion, thus giving rise to greatly enhanced reversible capacity and cycling stability for sodium storage, as compared to the other two samples with different organized structure.

Experimental and Theoretical Insights on Interface Engineered FeS/rGO as Anode for Fast-Charging Lithium- and Sodium-Ion Batteries

Interface engineering facilitates the development of stable energy storage devices that can endure the severe changes encountered during operation. In the context of fast-charging anodes for lithium- and sodium-ion batteries (LIBs and SIBs), the interface needs to promote charge/ion transfer processes, enhance Li-/Na-ion storage capacity, and ensure good reversibility in order to function efficiently at high rates. Herein, a simple synthetic strategy is reported to design interfaces between transition metal sulfides and carbonaceous supports to generate high-performance fast-charging anodes. FeS/rGO nanostructures are synthesized via a simple solid-state annealing method by employing FeOOH/rGO, a metastable precursor, which is annealed at 600 °C in the presence of H₂S gas. Interface engineering between FeS and rGO significantly improved the electrochemical performance, particularly demonstrated by stable capacities at high rates (625 mAh g⁻¹ at 5 A g⁻¹ for LIBs and 708 mAh g⁻¹ at 10 A g⁻¹ for SIBs). The high-rate charge storage is primarily governed by capacitive processes. Density functional theory (DFT) calculations attributed the enhanced performance of the FeS/rGO anode to a lower diffusion energy barrier for Li- and Na-ion diffusion at the interface along with the presence of a built-in electric field at the heterointerface.

An innovative double-Shell layer nitrogen and sulfur co-doped carbon-Encapsulated FeS composite for enhanced lithium-Ion battery performance

FeS, with its high theoretical capacity and natural abundance, holds significant promise as an anode material for lithium-ion batteries (LIBs). However, its practical application is constrained by poor electrical conductivity and substantial volume expansion during cycling, which impair charge-discharge efficiency and cycling stability. To overcome these challenges, we developed a nitrogen and sulfur co-doped carbon-encapsulated FeS composite with a hollow double-layer structure (HDL-FeS@NSC). Utilizing sulfur spheres as a sacrificial template, our inside-out synthesis strategy produces a unique material design. The HDL-FeS@NSC composite exhibits significant improvements in electrochemical performance compared to pure FeS. These enhancements are due to its increased specific surface area, which facilitates lithium-ion diffusion; a shortened Li+ diffusion pathway; structural stability that mitigates volume expansion; and an optimized carbon layer that boosts conductivity. The HDL-FeS@NSC-70 anode demonstrates a specific capacity of 879.6 mAh/g after 600 cycles at 1.0 A/g and retains 558.0 mAh/g at 5.0 A/g. Additionally, the lithium storage mechanism has been thoroughly investigated using in-situ techniques. These results suggest that the HDL-FeS@NSC composite anode has the potential to significantly enhance lithium-ion battery performance, offering a promising solution for next-generation energy storage systems.

Large-Scale Synthesis of N,S Codoped Carbon-Modified Fe0.975S Composites as a Novel Anode for Lithium/Sodium Ion Batteries with Enhanced Performance

To overcome obstacles hindering the commercialization of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), we introduce a cost-effective single-step sulfurization strategy for synthesizing iron sulfide (Fe0.975S) nanohybrids, augmented by N,S codoped carbon. The resulting N,S codoped carbon-coated Fe0.975S (Fe0.975S@NSC) electrode exhibits exceptional potential as a highly reversible anode material for both LIBs and SIBs. With impressive initial discharge and charge capacities (1658.2 and 1254.9 mAh g-1 for LIBs and 1450.9 and 1077.1 mAh g-1 for SIBs), the electrode maintains substantial capacity retention (900 mA h g-1 after 1000 cycles for LIBs and 492.5 mA h g-1 after 600 cycles for SIBs at 1.0 A g-1). The LiMn2O4//Fe0.975S@NSC and Na3V2(PO4)3//Fe0.975S@NSC full batteries can maintain excellent reversible capacity and robust cycling stability. Ex situ and in situ X-ray diffraction, density functional theory (DFT) calculations, and kinetics analysis confirm the promising energy storage potential of the Fe0.975S@NSC composite.

Facile synthesis of NiCoSe2@carbon anode for high-performance sodium-ion batteries

Sodium-ion batteries offer significant advantages in terms of low-temperature performance and safety. In this study, we present a straightforward synthetic approach to produce bimetallic selenide NiCoSe2 nanoparticles grown on a three-dimensional porous carbon framework for application as anode materials in sodium-ion batteries. This unique architecture enhances reaction kinetics and structural stability. The three-dimensional interconnected porous carbon network establishes a continuous pathway of electronic conductive, while increasing specific surface area and mitigating volume expansion. Consequently, these features expedite ion transfer and enhance electrolyte interaction. Notably, compared to CoSe, NiCoSe2 exhibits reduced ion transport distances and lower sodium diffusion barriers. Leveraging these attributes, NiCoSe2/N, Se co-doped carbon composite materials (NiCoSe2/NSC) demonstrate a high specific capacity of 320.8 mAh/g, even after 1000 cycles at 5.0 A/g, with a capacity retention rate of 85.1%. The study further delves into the revelation of the reaction mechanism and ion transport pathway through in-situ X-ray diffraction (XRD) analysis and theoretical calculations. The development of these anode materials is poised to pave the way for advancements in sodium-ion battery technology.

Fabrication of NiMn2O4/C hollow spheres with a trilaminar shell structure as an anode material for sodium-ion batteries

NiMn2O4/C hollow spheres with sandwich-structured shells were fabricated by a hydrothermal method. Leveraging the mesoporous design of the carbon hollow spheres, NiMn2O4 nanosheets were evenly dispersed on both the inner and outer surfaces of the carbon shells. NiMn2O4/C demonstrated excellent rate capability and prolonged cycling durability for sodium ion storage.

High-Efficiency Electroreduction of Nitrite to Ammonia on Ni Nanoparticles Strutted 3D Honeycomb-Like Porous Carbon Framework

Electroreduction of nitrite (NO2 - ) to ammonia (NH3 ) provides a sustainable approach to yield NH3 , whilst eliminating NO2 - contaminants. In this study, Ni nanoparticles strutted 3D honeycomb-like porous carbon framework (Ni@HPCF) is fabricated as a high-efficiency electrocatalyst for selective reduction of NO2 - to NH3 . In 0.1 M NaOH with NO2 - , such Ni@HPCF electrode obtains a significant NH3 yield of 12.04 mg h-1  mgcat. -1 and a Faradaic efficiency of 95.1 %. Furthermore, it exhibits good long-term electrolysis stability.

Cobalt-Nanoparticles-Decorated 3D Porous Nitrogen-Doped Carbon Network for Electrocatalytic Nitrite Reduction to Ammonia

Electrocatalytic nitrite (NO2-) reduction offers the potential to synthesize high-value ammonia (NH3) while simultaneously removing NO2- pollution from aqueous solutions, but it requires high-efficiency catalysts to drive the complex six-electron reaction. Herein, cobalt-nanoparticle-decorated 3D porous nitrogen-doped carbon network (Co@NC) is proven as a high-efficiency catalyst for the selective electroreduction of NO2- to NH3. Such Co@NC attains a large NH3 yield of 922.7 μmol h-1 cm-2 and a high Faradaic efficiency of 95.4% under alkaline conditions. Furthermore, it shows remarkable electrochemical stability during cyclic electrolysis.

Bimetal Oxide Reduction-Induced Perforation Strategy for Preparing a Multi-Microchannel Graphene-Based Anode Material with Rapid Sodium-Ion Diffusion

A sodium-ion battery, with a wide operating range, is much cheaper and safer than a lithium battery. Graphene is regarded as a promising carbon material in the preparation of anode materials. However, the large two-dimensional (2D) graphene sheets restrain the cross-plane diffusion of electrolyte ions, limiting the further improvement of rate performance. Herein, a nanohybrid of FeCo2Se4 and holey graphene (FeCo2Se4/HG) has been successfully prepared by the synchronism of pore creation and active material growth. Specifically, FeCo-oxide nanoparticles serve as the etching agents, generating in-plane nanoholes and subsequently converted into FeCo2Se4. The nanoholes provide a high density of cross-plane diffusion channels for sodium ions, serving as ionic diffusion shortcuts between different graphene layers to accelerate ion transport across the entire electrode. The unique architecture endows FeCo2Se4/HG with superior rate capability (411.2 mA h g-1 at 20 A g-1) and a specific capacity of 432.4 mA h g-1 at 2.0 A g-1 after 2000 cycles with a capacity retention rate of 92.4%. Therefore, pore engineering makes it possible for holey graphene-based electrodes to achieve outstanding rate performance and superb cycling durability.