Construction of point-line-plane (0-1-2 dimensional) Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-SnO<Subscript>2</Subscript>/graphene hybrids as the anodes with excellent lithium storage capability

The assembly of hybrid nanomaterials has opened up a new direction for the construction of high-performance anodes for lithium-ion batteries (LIBs). In this work, we present a straightforward, eco-friendly, one-step hydrothermal protocol for the synthesis of a new type of Fe₂O₃-SnO₂/graphene hybrid, in which zero-dimensional (0D) SnO₂ nanoparticles with an average diameter of 8 nm and one-dimensional (1D) Fe₂O₃ nanorods with a length of ~150 nm are homogeneously attached onto two-dimensional (2D) reduced graphene oxide nanosheets, generating a unique point-line-plane (0D-1D-2D) architecture. The achieved Fe₂O₃-SnO₂/graphene exhibits a well-defined morphology, a uniform size, and good monodispersity. As anode materials for LIBs, the hybrids exhibit a remarkable reversible capacity of 1,530 mA·g^?1 at a current density of 100 mA·g^?1 after 200 cycles, as well as a high rate capability of 615 mAh·g^?1 at 2,000 mA·g^?1. Detailed characterizations reveal that the superior lithium-storage capacity and good cycle stability of the hybrids arise from their peculiar hybrid nanostructure and conductive graphene matrix, as well as the synergistic interaction among the components.

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Antipulverization Electrode Based on Low‐Carbon Triple‐Shelled Superstructures for Lithium‐Ion Batteries

The realization of antipulverization electrode structures, especially using low‐carbon‐content anode materials, is crucial for developing high‐energy and long‐life lithium‐ion batteries (LIBs); however, this technology remains challenging. This study shows that SnO₂ triple‐shelled hollow superstructures (TSHSs) with a low carbon content (4.83%) constructed by layer‐by‐layer assembly of various nanostructure units can withstand a huge volume expansion of ≈231.8% and deliver a high reversible capacity of 1099 mAh g^?1 even after 1450 cycles. These values represent the best comprehensive performance in SnO₂‐based anodes to date. Mechanics simulations and in situ transmission electron microscopy suggest that the TSHSs enable a self‐synergistic structure‐preservation behavior upon lithiation/delithiation, protecting the superstructures from collapse and guaranteeing the electrode structural integrity during long‐term cycling. Specifically, the outer shells during lithiation processes are fully lithiated, preventing the overlithiation and the collapse of the inner shells; in turn, in delithiation processes, the underlithiated inner shells work as robust cores to support the huge volume contraction of the outer shells; meanwhile, the middle shells with abundant pores offer sufficient space to accommodate the volume change from the outer shell during both lithiation and delithiation. This study opens a new avenue in the development of high‐performance LIBs for practical energy applications.     

Etching‐Assisted Crumpled Graphene Wrapped Spiky Iron Oxide Particles for High‐Performance Li‐Ion Hybrid Supercapacitor

From graphene oxide wrapped iron oxide particles with etching/reduction process, high‐performance anode and cathode materials of lithium‐ion hybrid supercapacitors are obtained in the same process with different etching conditions, which consist of partially etched crumpled graphene (CG) wrapped spiky iron oxide particles (CG@SF) for a battery‐type anode, and fully etched CG for a capacitive‐type cathode. The CG is formed along the shape of spikily etched particles, resulting in high specific surface area and electrical conductivity, thus the CG‐based cathode exhibits remarkable capacitive performance of 210 F g^?1 and excellent rate capabilities. The CG@SF can also be ideal anode materials owing to spiky and porous morphology of the particles and tightly attached crumpled graphene onto the spiky particles, which provides structural stability and low contact resistance during repetitive lithiation/delithiation processes. The CG@SF anode shows a particularly high capacitive performance of 1420 mAh g^?1 after 270 cycles, continuously increases capacity beyond the 270th cycle, and also maintains a high capacity of 170 mAh g^?1 at extremely high speeds of 100 C. The full‐cell exhibits a higher energy density up to 121 Wh kg^?1 and maintains high energy density of 60.1 Wh kg^?1 at 18.0 kW kg^?1. This system could thus be a practical energy storage system to fill the gap between batteries and supercapacitors.     

Nano‐Architectured Composite Anode Enabling Long‐Term Cycling Stability for High‐Capacity Lithium‐Ion Batteries

Failure mechanisms associated with silicon‐based anodes are limiting the implementation of high‐capacity lithium‐ion batteries. Understanding the aging mechanism that deteriorates the anode performance and introducing novel‐architectured composites offer new possibilities for improving the functionality of the electrodes. Here, the characterization of nano‐architectured composite anode composed of active amorphous silicon domains (a‐Si, 20 nm) and crystalline iron disilicide (c‐FeSi₂, 5–15 nm) alloyed particles dispersed in a graphite matrix is reported. This unique hierarchical architecture yields long‐term mechanical, structural, and cycling stability. Using advanced electron microscopy techniques, the nanoscale morphology and chemical evolution of the active particles upon lithiation/delithiation are investigated. Due to the volumetric variations of Si during lithiation/delithiation, the morphology of the a‐Si/c‐FeSi₂ alloy evolves from a core‐shell to a tree‐branch type structure, wherein the continuous network of the active a‐Si remains intact yielding capacity retention of 70% after 700 cycles. The root cause of electrode polarization, initial capacity fading, and electrode swelling is discussed and has profound implications for the development of stable lithium‐ion batteries.     

In situ synthesis of SnO2/graphene nanocomposite and their application as anode material for lithium ion battery

SnO₂/graphene nanocomposite was prepared via an in situ chemical synthesis method. The nanocomposite was characterized by X-ray diffraction, filed emission scanning electron microscope and transmission electron microscope, which revealed that tiny SnO₂ nanoparticles could be homogeneously distributed on the graphene matrix. The electrochemical performance of the SnO₂/graphene nanocomposite as anode material was measured by galvanostatic charge/discharge cycling. The SnO₂/graphene nanocomposite showed a reversible capacity of 665 mAh/g after 50 cycles and an excellent cycling performance for lithium ion battery, which was ascribed to the three-dimensional architecture of SnO₂/graphene nanocomposite. These results suggest that SnO₂/graphene nanocomposite would be a promising anode material for lithium ion battery.     

Graphene‐Bonded and ‐Encapsulated Si Nanoparticles for Lithium Ion Battery Anodes

Silicon (Si) has been considered a very promising anode material for lithium ion batteries due to its high theoretical capacity. However, high‐capacity Si nanoparticles usually suffer from low electronic conductivity, large volume change, and severe aggregation problems during lithiation and delithiation. In this paper, a unique nanostructured anode with Si nanoparticles bonded and wrapped by graphene is synthesized by a one‐step aerosol spraying of surface‐modified Si nanoparticles and graphene oxide suspension. The functional groups on the surface of Si nanoparticles (50–100 nm) not only react with graphene oxide and bind Si nanoparticles to the graphene oxide shell, but also prevent Si nanoparticles from aggregation, thus contributing to a uniform Si suspension. A homogeneous graphene‐encapsulated Si nanoparticle morphology forms during the aerosol spraying process. The open‐ended graphene shell with defects allows fast electrochemical lithiation/delithiation, and the void space inside the graphene shell accompanied by its strong mechanical strength can effectively accommodate the volume expansion of Si upon lithiation. The graphene shell provides good electronic conductivity for Si nanoparticles and prevents them from aggregating during charge/discharge cycles. The functionalized Si encapsulated by graphene sample exhibits a capacity of 2250 mAh g^?1 (based on the total mass of graphene and Si) at 0.1C and 1000 mAh g^?1 at 10C, and retains 85% of its initial capacity even after 120 charge/discharge cycles. The exceptional performance of graphene‐encapsulated Si anodes combined with the scalable and one‐step aerosol synthesis technique makes this material very promising for lithium ion batteries.     

Graphene oxide-decorated Fe<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> microflowers as a promising anode for lithium and sodium storage

Mixed transition metal oxides (MTMOs) have received intensive attention as promising anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In this work, we demonstrate a facile one-step water-bath method for the preparation of graphene oxide (GO) decorated Fe₂(MoO₄)₃ (FMO) microflower composite (FMO/GO), in which the FMO is constructed by numerous nanosheets. The resulting FMO/GO exhibits excellent electrochemical performances in both LIBs and SIBs. As the anode material for LIBs, the FMO/GO delivers a high capacity of 1,220 mAh·g^–1 at 200 mA·g^–1 after 50 cycles and a capacity of 685 mAh·g^–1 at a high current density of 10 A·g^–1. As the anode material for SIBs, the FMO/GO shows an initial discharge capacity of 571 mAh·g^–1 at 100 mA·g^–1, maintaining a discharge capacity of 307 mAh·g^–1 after 100 cycles. The promising performance is attributed to the good electrical transport from the intimate contact between FMO and graphene oxide. This work indicates that the FMO/GO composite is a promising anode for high-performance lithium and sodium storage.

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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 (Ti₃C₂) 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.     

A Robust and Conductive Black Tin Oxide Nanostructure Makes Efficient Lithium‐Ion Batteries Possible

SnO₂‐based lithium‐ion batteries have low cost and high energy density, but their capacity fades rapidly during lithiation/delithiation due to phase aggregation and cracking. These problems can be mitigated by using highly conducting black SnO_2?x , which homogenizes the redox reactions and stabilizes fine, fracture‐resistant Sn precipitates in the Li₂O matrix. Such fine Sn precipitates and their ample contact with Li₂O proliferate the reversible Sn → Li _x Sn → Sn → SnO₂/SnO_2?x cycle during charging/discharging. SnO_2?x electrode has a reversible capacity of 1340 mAh g^?1 and retains 590 mAh g^?1 after 100 cycles. The addition of highly conductive, well‐dispersed reduced graphene oxide further stabilizes and improves its performance, allowing 950 mAh g^?1 remaining after 100 cycles at 0.2 A g^?1 with 700 mAh g^?1 at 2.0 A g^?1. Conductivity‐directed microstructure development may offer a new approach to form advanced electrodes.     

Adjusting the Chemical Bonding of SnO2@CNT Composite for Enhanced Conversion Reaction Kinetics

Carbon nanotubes (CNTs) with excellent electron conductivity are widely used to improve the electrochemical performance of the SnO₂ anode. However, the chemical bonding between SnO₂ and CNTs is not clearly elucidated despite it may affect the lithiation/delithiation behavior greatly. In this work, an SnO₂@CNT composite with Sn? C and Sn? O? C bonds as a linkage bridge is reported and the influence of the Sn? C and Sn? O? C bonds on the lithium storage properties is revealed. It is found that the Sn? C bond can act as an ultrafast electron transfer path, facilitating the reversible conversion reaction between Sn and Li₂O to form SnO₂. Therefore, the SnO₂@CNT composite with more Sn? C bond shows high reversible capacity and nearly half capacity contributes from conversion reaction. It is opposite for the SnO₂@CNT composite with more Sn? O? C bond that the electrons cannot be transferred directly to CNTs, resulting in depressed conversion reaction kinetics. Consequently, this work can provide new insight for exploration and design of metal oxide/carbon composite anode materials in lithium‐ion battery.     

Surface Coating Constraint Induced Anisotropic Swelling of Silicon in Si–Void@SiO x Nanowire Anode for Lithium‐Ion Batteries

Here a simple and an environmentally friendly approach is developed for the fabrication of Si–void@SiO_x nanowires of a high‐capacity Li‐ion anode material. The outer surface of the robust SiO_x backbone and the inside void structure in Si–void@SiO_x nanowires appropriately suppress the volume expansion and lead to anisotropic swelling morphologies of Si nanowires during lithiation/delithiation, which is first demonstrated by the in situ lithiation process. Remarkably, the Si–void@SiO_x nanowire electrode exhibits excellent overall lithium‐storage performance, including high specific capacity, high rate property, and excellent cycling stability. A reversible capacity of 1981 mAh g^?1 is obtained in the fourth cycle, and the capacity is maintained at 2197 mAh g^?1 after 200 cycles at a current density of 0.5 C. The outstanding overall properties of the Si–void@SiO_x nanowire composite make it a promising anode material of lithium‐ion batteries for the power‐intensive energy storage applications.     

SnO2-reduced graphene oxide nanoribbons as anodes for lithium ion batteries with enhanced cycling stability

A nanocomposite material of SnO2-reduced graphene oxide nanoribbons has been developed. In this composite, the reduced graphene oxide nanoribbons are uniformly coated by nanosized SnO2 that formed a thin layer of SnO2 on the surface. When used as anodes in lithium ion batteries, the composite shows outstanding electrochemical performance with the high reversible discharge capacity of 1,027 mAh/g at 0.1 A/g after 165 cycles and 640 mAh/g at 3.0 A/g after 160 cycles with current rates varying from 0.1 to 3.0 A/g and no capacity decay after 600 cycles compared to the second cycle at a current density of 1.0 A/g. The high reversible capacity, good rate performance and excellent cycling stability of the composite are due to the synergistic combination of electrically conductive reduced graphene oxide nanoribbons and SnO2, The method developed here is practical for the large-scale development of anode materials for lithium ion batteries.     

Synthesis of well-defined Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods/N-doped graphene for lithium-ion batteries

The geometric size and distribution of magnetic nanoparticles are critical to the morphology of graphene (GN) nanocomposites, and thus they can affect the capacity and cycling performance when these composites are used as anode materials in lithium-ion batteries (LiBs). In this work, Fe₃O₄ nanorods were deposited onto fully extended nitrogen-doped GN sheets from a binary precursor in two steps, a hydrothermal process and an annealing process. This route effectively tuned the Fe₃O₄ nanorod size distribution and prevented their aggregation. The transformation of the binary precursor was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). XPS analysis indicated the presence of N-doped GN sheets, and that the magnetic nanocrystals were anchored and uniformly distributed on the surface of the flattened N-doped GN sheets. As a high performance anode material, the structure was beneficial for electron transport and exchange, resulting in a large reversible capacity of 929 mA·h·g^–1, high-rate capability, improved cycling stability, and higher electrical conductivity. Not only does the result provide a strategy for extending GN composites for use as LiB anode materials, but it also offers a route for the preparation of other oxide nanorods from binary precursors.

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SnO2 Anode Surface Passivation by Atomic Layer Deposited HfO2 Improves Li‐Ion Battery Performance

For the first time, it is demonstrated that nanoscale HfO₂ surface passivation layers formed by atomic layer deposition (ALD) significantly improve the performance of Li ion batteries with SnO₂‐based anodes. Specifically, the measured battery capacity at a current density of 150 mAg^?1 after 100 cycles is 548 and 853 mAhg^?1 for the uncoated and HfO₂‐coated anodes, respectively. Material analysis reveals that the HfO₂ layers are amorphous in nature and conformably coat the SnO₂‐based anodes. In addition, the analysis reveals that ALD HfO₂ not only protects the SnO₂‐based anodes from irreversible reactions with the electrolyte and buffers its volume change, but also chemically interacts with the SnO₂ anodes to increase battery capacity, despite the fact that HfO₂ is itself electrochemically inactive. The amorphous nature of HfO₂ is an important factor in explaining its behavior, as it still allows sufficient Li diffusion for an efficient anode lithiation/delithiation process to occur, leading to higher battery capacity.     

3D composites of ZnSnO<Subscript>3</Subscript> nanoplates/reduced graphene oxide aerogels as an advanced lithium-ion battery anode

Zinc-based bimetal oxides have received considerable attention as anode for lithium-ion batteries (LIBs). A one-pot self-assembly hydrothermal method is developed for the fabrication of 3D hierarchical structure aerogels from zinc stannate (ZnSnO₃) and reduced graphene oxide (rGO). 3D interconnected porous structure with ZnSnO₃ hexagon nanoplates uniformly dispersed on graphene sheets has been constructed successfully, in which the crystalline hexagon nanoplates ZnSnO₃ are firstly used to prepare ZnSnO₃-based anode materials for LIBs. The as-prepared ZnSnO₃ nanoplates/reduced graphene oxide aerogels (ZnSnO₃–rGAs) electrode demonstrates an excellent reversible capacity (780 mAh g^?1) after 200 cycles at a certain current density (100 mA g^?1) and still delivers a specific capacity of 460 mAh g^?1 even at 1000 mA g^?1. The superior performance of lithium storage is attributed to the 3D porous hierarchical structure and the synergistic effects of uniform hexagon nanoplates ZnSnO₃ and rGO sheets.     

In situ synthesis of SnO2 nanosheet/graphene composite as anode materials for lithium-ion batteries

A novel SnO₂/graphene composite has been synthesized via an in situ chemical synthesis method, in which single crystal SnO₂ nanosheets are uniformly grown on graphene support. The as-prepared products were characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscope, Thermogravimetric analyses and Nitrogen adsorption/desorption. When used as an anode material for lithium ion batteries, the SnO₂/graphene composite exhibits an enhanced reversible lithium storage capacity and good cyclic performance. The first discharge and charge capacities are 1,366 and 975 mAh g^?1, respectively. After 100 cycles, the reversible discharge capacity is still maintained at 451 mAh g^?1 at the current densities of 100 mA g^?1, indicating that it’s a promising anode material for high performance lithium ion batteries.     

Laterally confined graphene nanosheets and graphene/SnO<Subscript>2</Subscript> composites as high-rate anode materials for lithium-ion batteries

High-rate anode materials for lithium-ion batteries are desirable for applications that require high power density. We demonstrate the advantageous rate capability of few-layered graphene nanosheets, with widths of 100–200 nm, over micro-scale graphene nanosheets. Possible reasons for the better performance of the former include their smaller size and better conductivity than the latter. Combination of SnO₂ nanoparticles with graphene was used to further improve the gravimetric capacities of the electrode at high charge-discharge rates. Furthermore, the volumetric capacity of the composites was substantially enhanced compared to pristine graphene due to the higher density of the composites.     

Hierarchical porous onion-shaped LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> as ultrahigh-rate cathode material for lithium ion batteries

Spinel LiMn₂O₄ is a widely utilized cathode material for Li-ion batteries. However, its applications are limited by its poor energy density and power density. Herein, a novel hierarchical porous onion-like LiMn₂O₄(LMO) was prepared to shorten the Li⁺ diffusion pathway with the presence of uniform pores and nanosized primary particles. The growth mechanism of the porous onion-like LiMn₂O₄ was analyzed to control the morphology and the crystal structure so that it forms a polyhedral crystal structure with reduced Mn dissolution. In addition, graphene was added to the cathode (LiMn₂O₄/graphene) to enhance the electronic conductivity. The synthesized LiMn₂O₄/graphene exhibited an ultrahigh-rate performance of 110.4 mAh·g^–1 at 50 C and an outstanding energy density at a high power density, maintaining 379.4 Wh·kg^–1 at 25,293 W·kg^–1. Besides, it shows durable stability, with only 0.02% decrease in the capacity per cycle at 10 C. Furthermore, the (LiMn₂O₄/graphene)/graphite full-cell exhibited a high discharge capacity. This work provides a promising method for the preparation of outstanding, integrated cathodes for potential applications in lithium ion batteries.

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A Flexible Film with SnS2 Nanoparticles Chemically Anchored on 3D‐Graphene Framework for High Areal Density and High Rate Sodium Storage

The design and construction of flexible electrodes that can function at high rates and high areal capacities are essential regarding the practical application of flexible sodium‐ion batteries (SIBs) and other energy storage devices, which remains significantly challenging by far. Herein, a flexible and 3D porous graphene nanosheet/SnS₂ (3D‐GNS/SnS₂) film is reported as a high‐performance SIB electrode. In this hybrid film, the GNS/SnS₂ microblocks serve as pillars to assemble into a 3D porous and interconnected framework, enabling fast electron/ion transport; while the GNS bridges the GNS/SnS₂ microblocks into a flexible framework to provide satisfactorily mechanical strength and long‐range conductivity. Moreover, the SnS₂ nanocrystals, which chemically bond with GNS, provide sufficient active sites for Na storage and ensure the cycling stability. Consequently, this flexible 3D‐GNS/SnS₂ film exhibits excellent Na‐storage performances, especially in terms of high areal capacity (2.45 mAh cm^?2) and high rates with superior stability (385 mAh g^?1 at 1.0 A g^?1 over 1000 cycles with ≈100% retention). A flexible SIB full cell using this anode exhibits high and stable performance under various bending situations. Thus, this work provide a feasible route to prepare flexible electrodes with high practical viability for not only SIBs but also other energy storage devices.     

Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocrystal anode materials with improved cyclic stability for lithium ion batteries

The cyclic stability of Cr₂O₃ is very poor due to the large volume change during lithiation/delithiation. In this study, we have found that Cr₂O₃ nanocrystals synthesized by using a simple hydrothermal method can improve its cyclic stability. Sample calcined at 430 °C has uniform size, compact structure and high crystallization degree. These Cr₂O₃ nanocrystals exhibit a stable cyclic performance of 185 mAh g^?1 after 100 cycles at 100 mA g^?1. It is useful in real life, such as providing power consumption for minitype device, etc.