Bottom-up Approach Design, Band Structure, and Lithium Storage Properties of Atomically Thin γ-FeOOH Nanosheets

Toward Rapid-Charging Sodium-Ion Batteries using Hybrid-Phase Molybdenum Sulfide Selenide-Based Anodes

To attain both high energy density and power density in sodium-ion (Na⁺ ) batteries, the reaction kinetics and structural stability of anodes should be improved by materials optimization. In this work, few-layered molybdenum sulfide selenide (MoSSe) consisting of a mixture of 1T and 2H phases is designed to provide high ionic/electrical conductivities, low Na⁺ diffusion barrier, and stable Na⁺ storage. Reduced graphene oxide (rGO) is used as a conductive matrix to form 3D electron transfer paths. The resulting MoSSe@rGO anode exhibits high capacity and rate performance in both organic and solid-state electrolytes. The ultrafast Na⁺ storage kinetics of the MoSSe@rGO anode is attributed to the surface-dominant reaction process and broad Na⁺ channels. In situ and ex situ measurements are conducted to reveal the Na⁺ storage process in MoSSe@rGO. It is found that the MoS and MoSe bonds effectively limit the dissolution of the active materials. The favorable Na⁺ storage kinetics of the MoSSe@rGO electrode are ascribed to its low adsorption energy of -1.997 eV and low diffusion barrier of 0.087 eV. These results reveal that anion doping of metal sulfides is a feasible strategy to develop sodium-ion batteries with high energy and power densities and long life-span.

Synthesis and Electrochemical Property of FeOOH/Graphene Oxide Composites

A facile ultrasonication method was used to uniformly mix nanospindle-shaped FeOOH (80–100 nm) and a conductive matrix of graphene oxide (GO) to form FeOOH/GO composites. No carbon peak was observed in the X-ray diffraction pattern, indicating that the graphene oxide did not stack together and that the dispersion of graphene was very high. X-ray photoelectron spectroscopy (XPS) tests showed that the formation of Fe-O-C bonds played a positive role in electron transport, revealing that it has a certain impact on the electrochemical performance of FeOOH/GO. The FeOOH/GO was further characterized by TGA, and the content of GO in the synthesized sample was 6.68%. Compared with that of FeOOH, the initial discharge capacity of FeOOH/GO could reach 1437.28 mAh/g. Additionally, compared to that of pure FeOOH, the reversibility of the electrochemical reaction of FeOOH/GO was improved, and the impedance value was reduced. Finally, FeOOH/GO was used directly as a lithium-ion battery (LIB) anode material to improve the kinetics of the Lithium ions insertion/extraction process and improve ionic conductivity.

Stereoassembled V2O5@FeOOH Hollow Architectures with Lithiation Volumetric Strain Self-Reconstruction for Lithium-Ion Storage

Vanadium oxides have recently attracted widespread attention due to their unique advantages and have demonstrated promising chemical and physical properties for energy storage. This work develops a mild and efficient method to stereoassemble hollow V₂O₅@FeOOH heterostructured nanoflowers with thin nanosheets. These dual-phased architectures possess multiple lithiation voltage plateau and well-defined heterointerfaces facilitating efficient charge transfer, mass diffusion, and self-reconstruction with volumetric strain. As a proof of concept, the resulting V₂O₅@FeOOH hollow nanoflowers as an anode material for lithium-ion batteries (LIBs) realize high-specific capacities, long lifespans, and superior rate capabilities, e.g., maintaining a specific capacity as high as 985 mAh g⁻¹ at 200 mA g⁻¹ with good cyclability.

β-FeOOH: a new anode for potassium-ion batteries

β-FeOOH is employed as an anode for potassium-ion batteries, exhibiting high capacity and good cycling stability. The K⁺ storage mechanism of β-FeOOH is being investigated.

Uniform gallium oxyhydroxide nanorod anodes with superior lithium-ion storage

Exploration of a novel metal oxyhydroxide material provides potential candidates for lithium ion battery (LIB) anodes. In the present work, uniform GaOOH nanorods have been successfully synthesized via a simple hydrothermal method and employed as an anode material for LIBs for the first time. The obtained GaOOH nanorods show a high-purity phase with an average length of ∼1.4 μm and a width of ∼100 nm. As an anode, it delivers a stable capacity of ∼1089 mA h g^-1 at a 0.5 A g^-1 current density upon 300 cycles and a high rate capacity of ∼639 mA h g^-1 at 2 A g^-1, where the pseudocapacitance plays a dominant role with a capacity contribution ratio of about 83% at 2.0 mV s^-1. This enhanced storage performance can be attributed to a 1D nanostructure with efficient electron and ion transfer as well as strain relaxation upon multiple-cycling.

Recent Advances and Perspectives of Carbon-Based Nanostructures as Anode Materials for Li-ion Batteries

Rechargeable batteries are attractive power storage equipment for a broad diversity of applications. Lithium-ion (Li-ion) batteries are widely used the superior rechargeable battery in portable electronics. The increasing needs in portable electronic devices require improved Li-ion batteries with excellent results over many discharge-recharge cycles. One important approach to ensure the electrodes' integrity is by increasing the storage capacity of cathode and anode materials. This could be achieved using nanoscale-sized electrode materials. In the article, we review the recent advances and perspectives of carbon nanomaterials as anode material for Lithium-ion battery applications. The first section of the review presents the general introduction, industrial use, and working principles of Li-ion batteries. It also demonstrates the advantages and disadvantages of nanomaterials and challenges to utilize nanomaterials for Li-ion battery applications. The second section of the review describes the utilization of various carbon-based nanomaterials as anode materials for Li-ion battery applications. The last section presents the conclusion and future directions.

Exploring the sodium ion storage mechanism of gallium sulfide (Ga2S3): a combined experimental and theoretical approach

Developing sodium ion battery (SIB) anode materials of a low-cost and high-capacity nature for future large-scale applications still involves challenges. Herein, we have reported gallium sulfide (Ga2S3) as a novel SIB anode material for the first time. Ga2S3 nanorods have been synthesized via the facile hydrothermal preparation of a GaOOH precursor with subsequent H2S annealing. Mixed with graphene upon electrode preparation, this Ga2S3 electrode maintains a reversible specific capacity of 476 mA h g-1 after 100 cycles at a current density of 0.4 A g-1, with a coulombic efficiency of over 99%. Ex situ XRD analysis and theoretical calculations are employed to comprehensively elucidate the detailed sodium ion storage mechanism of Ga2S3, which is composed of initial Na+ intercalation, a subsequent multi-step conversion reaction between S and Na+, and an eventual alloying reaction between Ga and Na+ with the end product of Na7Ga13. Further kinetics analysis has demonstrated that the conversion reaction is the rate-limiting step due to a multi-step reaction with the intermediate phase of GaS. Moreover, the appearance of liquid metal Ga, as confirmed via TEM observations and theoretical calculations, can serve as a self-healing agent that repairs cracks in the electrode. Our findings shed light on the further design of Ga-based materials, and they also can be extended to solid-state-battery systems.

Self-Assembly of Transition Metal Oxide Nanostructures on MXene Nanosheets for Fast and Stable Lithium Storage

Recently, a new class of 2D materials, i.e., transition metal carbides, nitrides, and carbonitrides known as MXenes, is unveiled with more than 20 types reported one after another. Since they are flexible and conductive, MXenes are expected to compete with graphene and other 2D materials in many applications. Here, a general route is reported to simple self-assembly of transition metal oxide (TMO) nanostructures, including TiO₂ nanorods and SnO₂ nanowires, on MXene (Ti₃ C₂ ) nanosheets through van der Waals interactions. The MXene nanosheets, acting as the underlying substrate, not only enable reversible electron and ion transport at the interface but also prevent the TMO nanostructures from aggregation during lithiation/delithiation. The TMO nanostructures, in turn, serve as the spacer to prevent the MXene nanosheets from restacking, thus preserving the active areas from being lost. More importantly, they can contribute extraordinary electrochemical properties, offering short lithium diffusion pathways and additional active sites. The resulting TiO₂ /MXene and SnO₂ /MXene heterostructures exhibit superior high-rate performance, making them promising high-power and high-energy anode materials for lithium-ion batteries.

Rapid Amorphization in Metastable CoSeO3·H2O Nanosheets for Ultrafast Lithiation Kinetics

The realization of high-performance anode materials with high capacity at fast lithiation kinetics and excellent cycle stability remains a significant but critical challenge for high-power applications such as electric vehicles. Two-dimensional nanostructures have attracted considerable research interest in electrochemical energy storage devices owing to their intriguing surface effect and significantly decreased ion-diffusion pathway. Here we describe rationally designed metastable CoSeO₃·H₂O nanosheets synthesized by a facile hydrothermal method for use as a Li ion battery anode. This crystalline nanosheet can be steadily converted into amorphous phase at the beginning of the first Li⁺ discharge cycling, leading to ultrahigh reversible capacities of 1100 and 515 mAh g^-1 after 1000 cycles at a high rate of 3 and 10 A g^-1, respectively. The as-obtained amorphous structure experiences an isotropic stress, which can significantly reduce the risk of fracture during electrochemical cycling. Our study offers a precious opportunity to reveal the ultrafast lithiation kinetics associated with the rapid amorphization mechanism in layered cobalt selenide nanosheets.

Tuning Pseudocapacitance via C-S Bonding in WS2 Nanorods Anchored on N,S Codoped Graphene for High-Power Lithium Batteries

Pseudocapacitance plays an important role in high-power lithium-ion batteries (LIBs). However, it is still lack of effective methods to tailor the pseudocapacitance contribution in electrode materials for LIBs. Herein, pseudocapacitance tuned by the strength of C-S bonding has been rendered in WS₂ nanorods anchored on the N,S codoped three-dimensional graphene hybrid (WS₂@N,S-3DG) for the first time. The pseudocapacitive contributions in the charge storage can be enhanced effectively with the increased strength of C-S bonding. As expected, the enhanced extrinsic pseudocapacitance makes WS₂@N,S-3DG a fascinating electrode material for high-power LIBs, with a high reversible capacity of 509 mA h g^-1 over 500 cycles at a current density as high as 2 A g^-1. These encouraging results of pseudocapacitance tailored by chemical bonding provide new opportunities for designing advanced electrode materials.

Engineering 2D Nanofluidic Li-Ion Transport Channels for Superior Electrochemical Energy Storage

Rational surface engineering of 2D nanoarchitectures-based electrode materials is crucial as it may enable fast ion transport, abundant-surface-controlled energy storage, long-term structural integrity, and high-rate cycling performance. Here we developed the stacked ultrathin Co₃ O₄ nanosheets with surface functionalization (SUCNs-SF) converted from layered hydroxides with inheritance of included anion groups (OH^- , NO₃^- , CO₃^2- ). Such stacked structure establishes 2D nanofluidic channels offering extra lithium storage sites, accelerated Li-ion transport, and sufficient buffering space for volume change during electrochemical processes. Tested as an anode material, this unique nanoarchitecture delivers high specific capacity (1230 and 1011 mAh g^-1 at 0.2 and 1 A g^-1 , respectively), excellent rate performance, and long cycle capability (1500 cycles at 5 A g^-1 ). The demonstrated advantageous features by constructing 2D nanochannels in nonlayered materials may open up possibilities for designing high-power lithium ion batteries.

Band Gap Engineering of Hexagonal SnSe2 Nanostructured Thin Films for Infra-Red Photodetection

We, for the first time, provide the experimental demonstration on the band gap engineering of layered hexagonal SnSe₂ nanostructured thin films by varying the thickness. For 50 nm thick film, the band gap is ~2.04 eV similar to that of monolayer, whereas the band gap is approximately ~1.2 eV similar to that of bulk for the 1200 nm thick film. The variation of the band gap is consistent with the the theoretically predicted layer-dependent band gap of SnSe₂. Interestingly, the 400–1200 nm thick films were sensitiveto 1064 nm laser iradiation and the sensitivity increases almost exponentiallly with thickness, while films with 50–140 nm thick are insensitive which is due to the fact that the band gap of thinner films is greater than the energy corresponding to 1064 nm. Over all, our results establish the possibility of engineering the band gap of SnSe₂ layered structures by simply controlling the thickness of the film to absorb a wide range of electromagnetic radiation from infra-red to visible range.

Self-Templated Formation of Uniform F-CuO Hollow Octahedra for Lithium Ion Batteries

Novel F-CuO and FeOOH hollow octahedra are developed through a facile structure-evolution reaction. The formation of interior voids within the hierarchical octahedra is motivated by the Cl^- ions based etching, under a precise control over reaction agents and conditions. Owing to the synergistic effect of unique structural features and favorable composition, the hollow octahedra exhibit superior lithium-storage properties.

High Pseudocapacitance in FeOOH/rGO Composites with Superior Performance for High Rate Anode in Li-Ion Battery

Capacitive storage has been considered as one type of Li-ion storage with fast faradaic surface redox reactions to offer high power density for electrochemical applications. However, it is often limited by low extent of energy contribution during the charge/discharge process, providing insufficient influences to total capacity of Li-ion storage in electrodes. In this work, we demonstrate a pseudocapacitance predominated storage (contributes 82% of the total capacity) from an in-situ pulverization process of FeOOH rods on rGO (reduced graphene oxide) sheets for the first time. Such high extent of pseudocapacitive storage in the FeOOH/rGO electrode achieves high energy density with superior cycling performance over 200 cycles at different current densities (1135 mAh/g at 1 A/g and 783 mAh/g at 5 A/g). It is further revealed that the in-situ pulverization process is essential for the high pseudocapacitance in this electrode, because it not only produces a porous structure for high exposure of tiny FeOOH crystallites to electrolyte but also maintains stable electrochemical contact during ultrahigh rate charge transfer with high energy density in the battery. The utilization of in-situ pulverization in an Fe-based anode to realize high surface pseudocapacitance with superior performance may inspire future design of electrode structures in Li-ion batteries.