Exfoliated Graphene Oxide/MoO2 Composites as Anode Materials in Lithium-Ion Batteries: An Insight into Intercalation of Li and Conversion Mechanism of MoO2

Facile preparation of MoO3@Mo2CTxnanocomposite with high lithium storage performance byin situoxidation

In this work, a new MoO3@Mo2CTxnanocomposite was prepared from two-dimensional (2D) Mo2CTxMXene byin situoxidization in air, which exhibited wonderful lithium-storage performance as anodes of lithium-ion batteries (LIBs). The precursor Mo2CTxwas synthesized from Mo2Ga2C by selective etching of NH4F at 180 °C for 24 h. Thereafter, the Mo2CTxwas oxidized in air at 450 °C for 30 min to obtain MoO3@Mo2CTxnanocomposite. In the composite,in situgenerated MoO3nanocrystals pillar the layer structure of Mo2CTxMXene, which increases the interlayer space of Mo2CTxfor Li storage and enhances the structure stability of the composite. Mo2CTx2D sheets provide a conductive substrate for MoO3nanocrystals to enhance the Li+accessibility. As anodes of LIBs, the final discharge specific capacity of the MoO3@Mo2CTxcomposite was 511.1 mAh g-1at a current density of 500 mA g-1after 100 cycles, which is about 36.7 times that of pure Mo2CTxMXene (13.9 mAh g-1) and 3.2 times that of pure MoO3(159.9 mAh g-1). In the composites, both Mo2CTxand MoO3provide high lithium storage capacity and can enhance the performance of each other. Moreover, this composite can be made by a facile method ofin situoxidation. Therefore, the MoO3@Mo2CTxMXene nanocomposite is a promising anode of LIB with high performance.

A Laser-Induced Mo2 CTx MXene Hybrid Anode for High-Performance Li-Ion Batteries

MXenes, a fast-growing family of two-dimensional (2D) transition metal carbides/nitrides, are promising for electronics and energy storage applications. Mo2 CTx MXene, in particular, has demonstrated a higher capacity than other MXenes as an anode for Li-ion batteries. Yet, such enhanced capacity is accompanied by slow kinetics and poor cycling stability. Herein, it is revealed that the unstable cycling performance of Mo2 CTx is attributed to the partial oxidation into MoOx with structural degradation. A laser-induced Mo2 CTx /Mo2 C (LS-Mo2 CTx ) hybrid anode has been developed, of which the Mo2 C nanodots boost redox kinetics, and the laser-reduced oxygen content prevents the structural degradation caused by oxidation. Meanwhile, the strong connections between the laser-induced Mo2 C nanodots and Mo2 CTx nanosheets enhance conductivity and stabilize the structure during charge-discharge cycling. The as-prepared LS-Mo2 CTx anode exhibits an enhanced capacity of 340 mAh g-1 vs 83 mAh g-1 (for pristine) and an improved cycling stability (capacity retention of 106.2% vs 80.6% for pristine) over 1000 cycles. The laser-induced synthesis approach underlines the potential of MXene-based hybrid materials for high-performance energy storage applications.

MoO2 Nanoclusters Embedded in Hierarchical Nitrogen Doped Carbon Nanoflower as Electrocatalytic Mediators in Aqueous Zinc-Tellurium Batteries: Enhancing Electrochemical Kinetics of Tellurium Redox Reaction

Aqueous zinc-ion batteries (AZIBs) are considered to be one of the most promising devices for large-scale energy storage systems owing to their high theoretical capacity, environmental friendliness, and safety. However, the ionic intercalation or surface redox mechanisms in conventional cathode materials generally result in unsatisfactory capacities. Conversion-type aqueous zinc-tellurium (Zn-Te) batteries have recently gained widespread attention owing to their high theoretical specific capacities. However, it remains an enormous challenge to improve the slow kinetics of the aqueous Zn-Te batteries. Here, MoO2 nanoclusters embedded in hierarchical nitrogen-doped carbon nanoflower (MoO2 /NC) hosts are successfully synthesized and loaded with Te in aqueous Zn-Te batteries. Benefitting from the highly dispersed MoO2 nanoclusters and hierarchical nanoflower structure with a large specific surface area, the electrochemical kinetics of the Te redox reaction are significantly improved. As a result, the Te-MoO2 /NC electrode exhibits superior cycling stability and a high specific capacity of 493 mAh g-1 at 0.1 A g-1 . Meanwhile, the conversion mechanism is systematically explored using a variety of ex situ characterization methods. Therefore, this study provides a novel approach for enhancing the kinetics of the Te redox reaction in aqueous Zn-Te batteries.

Electron-rich hybrid matrix to enhance molybdenum oxide-based anode performance for Lithium-Ion batteries

Although MoO₂-based electrodes have been intensively studied as potential candidate anodes for lithium-ion batteries (LIBs) based on their high theoretical capacity (840 mAh g^-1 and 5447 mAh cm^-3), common issues such as severe volume variation, electrical conductivity loss, and low ionic conductivity, are prevalent. In this study, we demonstrate enhanced Li-ion kinetics and electrical conductivity of MoO₂-based anodes with ternary MoO₂-Cu-C composite materials. The MoO₂-Cu-C was synthesized via two-step high energy ball milling where Mo and CuO are milled, followed by the secondary milling with C. With the introduction of the Cu-C hybrid matrix in MoO₂ nanoparticles via the element transfer method using mechanochemical reactions, the sluggish Li-ion diffusion and unstable cycling behavior were significantly improved. The inactive Cu-C matrix contributes to the increase in electrical and ionic conductivity and mechanical stability of active MoO₂ during cycling, as characterized by various electrochemical analyses and ex situ analysis techniques. Hence, the MoO₂-Cu-C anode delivered promising cycling performance (674 mAh g^-1 (at 0.1 A g^-1) and 520 mAh g^-1 (at 0.5 A g^-1), respectively, after 100 cycles) and high-rate property (73% retention at 5 A g^-1 as comparison with the specific capacity at 0.1 A g^-1). The MoO₂-Cu-C electrode is a propitious next-generation anode for LIBs.

Ultrathin Graphene Oxide-Based Nanocomposite Membranes for Water Purification

Two-dimensional graphene oxide (GO)-based lamellar membranes have been widely developed for desalination, water purification, gas separation, and pervaporation. However, membranes with a well-organized multilayer structure and controlled pore size remain a challenge. Herein, an easy and efficient method is used to fabricate MoO₂@GO and WO₃@GO nanocomposite membranes with controlled structure and interlayer spacing. Such membranes show good separation for salt and heavy metal ions due to the intensive stacking interaction and electrostatic attraction. The as-prepared composite membranes showed high rejection rates (˃70%) toward small metal ions such as sodium (Na⁺) and magnesium (Mg²⁺) ions. In addition, both membranes also showed high rejection rates ˃99% for nickel (Ni²⁺) and lead (Pb²⁺) ions with good water permeability of 275 ± 10 L m^-2 h^-1 bar^-1. We believe that our fabricated membranes will have a bright future in next generation desalination and water purification membranes.

Graphene: Chemistry and Applications for Lithium-Ion Batteries

In the present era, different allotropes of carbon have been discovered, and graphene is the one among them that has contributed to many breakthroughs in research. It has been considered a promising candidate in the research and academic fields, as well as in industries, over the last decade. It has many properties to be explored, such as an enhanced specific surface area and beneficial thermal and electrical conductivities. Graphene is arranged as a 2D structure by organizing sp2 hybridized C with alternative single and double bonds, providing an extended conjugation combining hexagonal ring structures to form a honeycomb structure. The precious structure and outstanding characteristics are the major reason that modern industry relies heavily on graphene, and it is predominantly applied in electronic devices. Nowadays, lithium-ion batteries (LIBs) foremostly utilize graphene as an anode or a cathode, and are combined with polymers to use them as polymer electrolytes. After three decades of commercialization of the lithium-ion battery, it still leads in consumer electronic society due to its higher energy density, wider operating voltages, low self-discharge, noble high-temperature performance, and fewer maintenance requirements. In this review, we aim to give a brief review of the domination of graphene and its applications in LIBs.

Construction of a ternary MoO2/Ni/C hybrid towards lithium-ion batteries as a high-performance electrode

The high lithium storage performance of 3D flower-like MoO2/Ni/C through a temperature annealing strategy is benefitted from the high capacitive contribution, high electrical conductivity, and good structural stability.

Nanostructured Molybdenum-Oxide Anodes for Lithium-Ion Batteries: An Outstanding Increase in Capacity

This work aimed at synthesizing MoO₃ and MoO₂ by a facile and cost-effective method using extract of orange peel as a biological chelating and reducing agent for ammonium molybdate. Calcination of the precursor in air at 450 °C yielded the stochiometric MoO₃ phase, while calcination in vacuum produced the reduced form MoO₂ as evidenced by X-ray powder diffraction, Raman scattering spectroscopy, and X-ray photoelectron spectroscopy results. Scanning and transmission electron microscopy images showed different morphologies and sizes of MoO_x particles. MoO₃ formed platelet particles that were larger than those observed for MoO₂. MoO₃ showed stable thermal behavior until approximately 800 °C, whereas MoO₂ showed weight gain at approximately 400 °C due to the fact of re-oxidation and oxygen uptake and, hence, conversion to stoichiometric MoO₃. Electrochemically, traditional performance was observed for MoO₃, which exhibited a high initial capacity with steady and continuous capacity fading upon cycling. On the contrary, MoO₂ showed completely different electrochemical behavior with less initial capacity but an outstanding increase in capacity upon cycling, which reached 1600 mAh g^-1 after 800 cycles. This outstanding electrochemical performance of MoO₂ may be attributed to its higher surface area and better electrical conductivity as observed in surface area and impedance investigations.

Liquid-Metal-Assisted Deposition and Patterning of Molybdenum Dioxide at Low Temperature

Molybdenum dioxide (MoO2), considering its near-metallic conductivity and surface plasmonic properties, is a great material for electronics, energy storage devices and biosensing. Yet to this day, room-temperature synthesis of large area MoO2, which allows deposition on arbitrary substrates, has remained a challenge. Due to their reactive interfaces and specific solubility conditions, gallium-based liquid metal alloys offer unique opportunities for synthesizing materials that can meet these challenges. Herein, a substrate-independent liquid metal-based method for the room temperature deposition and patterning of MoO2 is presented. By introducing a molybdate precursor to the surrounding of a eutectic gallium-indium alloy droplet, a uniform layer of hydrated molybdenum oxide (H2MoO3) is formed at the interface. This layer is then exfoliated and transferred onto a desired substrate. Utilizing the transferred H2MoO3 layer, a laser-writing technique is developed which selectively transforms this H2MoO3 into crystalline MoO2 and produces electrically conductive MoO2 patterns at room temperature. The electrical conductivity and plasmonic properties of the MoO2 are analyzed and demonstrated. The presented metal oxide room-temperature deposition and patterning method can find many applications in optoelectronics, sensing, and energy industries.

Nanocomposite of ultra-small MoO2 embedded in nitrogen-doped carbon: In situ derivation from an organic molybdenum complex and its superior Li-Ion storage performance

MoO₂ is a promising anode material for lithium-ion batteries, however, the lithiation of bulk MoO₂ is usually limited to addition-type reaction at room temperature, and the conversion reaction is hindered because of the sluggish kinetics. Herein, a nanocomposite of MoO₂ embedded in nitrogen-doped carbon (MoO₂/NC) is synthesized through the in situ thermolysis of an organic molybdenum complex MoO₂(acac)(phen) (acac = acetylacetone, phen = 1,10-Phenanthroline). Owing to the fact that [MoO₂]²⁺ can be strongly chelated by phen, the molybdenum source in the MoO₂(acac)(phen) precursor is highly dispersed, leading to the formation of ultra-small MoO₂ nanoparticles in the nanocomposite, which can facilitate the conversion reaction. Moreover, the NC matrix can guarantee a high electrical conductivity and effectively accommodate the volume changes triggered by the conversion reaction. Consequently, the MoO₂/NC nanocomposite exhibits outstanding electrochemical properties, including large reversible capacity of 950 mA h g^-1 at 0.1 A g^-1, high-rate capability of 605 mA h g^-1 at 2 A g^-1, and excellent cycling stability over 500 cycles as an anode material for lithium-ion batteries.

Template-free fabrication of 1D core-shell MoO2@MoS2/nitrogen-doped carbon nanorods for enhanced lithium/sodium-ion storage

A universal anode material of 1D core-shell MoO₂@MoS₂/nitrogen-doped carbon (MoO₂@MoS₂/NC) nanorods has been elaborately synthesized via a facile fabrication route for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), in which MoO₂ core not only acts as a conductive backbone for efficient electron transport, but creates structural disorders in MoS₂ nanosheets to prevent aggregation and expose more active sites for alkali-ions. Meanwhile, the MoO₂ core is tightly encapsulated by the parallelly aligned MoS₂ nanosheets to constrain the size of crystals, which greatly shortens the ionic diffusion path and accelerates diffusion rate, thus ensuring fast reaction kinetics. Additionally, the resilient and conductive N-doped carbon matrix in the hybrid could maintain the structural integrity and enhance the electrical conductivity of the electrodes, improving the rate capability and life span. The flexible 1D nanorods could contract freely during the charge/discharge process, further assuring the structural stability of the electrodes. Benefiting from the above-mentioned advantages, the MoO₂@MoS₂/NC electrodes still remains a specific capacity of 583.5 mA h g^-1 after 1500 cycles at a high current density up to 10 A g^-1 in LIBs, and a capacity of 419.8 mA h g^-1 is steadily kept over 800 cycles at 2 A g^-1 in SIBs.

Walnut-like MoO2 with interconnected skeleton and opened muti-channel for fast sodium storage

Molybdenum dioxide (MoO₂) has attracted lots of theoretical interest as an anode material for sodium ion batteries (SIBs) due to its high theoretical capacity (836 mA h g^-1) and metallic electrical conductivity (1.9 × 10² S cm^-1). The insertion reaction, forming Na_0.98MoO₂ and the reversible conversion reaction, forming Mo and Na₂O from Na_0.98MoO₂ contribute capacities of 209 and 627 mA h g^-1, respectively, the latter occupies 75% of the totally theoretical capacity. However, intrinsic slow kinetics in bulk MoO₂ severely restricts the redox conversion reaction. In the present work, a walnut-like MoO₂ architecture (W-MoO₂) with opened multi-channel and interconnected skeleton was prepared in a tube furnace, providing an interconnected ion/electron dual-pathway, which effectively facilitates Na⁺ diffusion and reduces the internal resistance of the cells. The W-MoO₂ anode demonstrates an enhanced reversible sodium storage capacity of 354.7 mA h g^-1 at 0.5 A g^-1.

A Review of Recent Advancements in Electrospun Anode Materials to Improve Rechargeable Lithium Battery Performance

Although lithium-ion batteries have already had a considerable impact on making our lives smarter, healthier, and cleaner by powering smartphones, wearable devices, and electric vehicles, demands for significant improvement in battery performance have grown with the continuous development of electronic devices. Developing novel anode materials offers one of the most promising routes to meet these demands and to resolve issues present in existing graphite anodes, such as a low theoretical capacity and poor rate capabilities. Significant improvements over current commercial batteries have been identified using the electrospinning process, owing to a simple processing technique and a wide variety of electrospinnable materials. It is important to understand previous work on nanofiber anode materials to establish strategies that encourage the implementation of current technological developments into commercial lithium-ion battery production, and to advance the design of novel nanofiber anode materials that will be used in the next-generation of batteries. This review identifies previous research into electrospun nanofiber anode materials based on the type of electrochemical reactions present and provides insights that can be used to improve conventional lithium-ion battery performances and to pioneer novel manufacturing routes that can successfully produce the next generation of batteries.

Synthesizing High-Capacity Oxyfluoride Conversion Anodes by Direct Fluorination of Molybdenum Dioxide (MoO2 )

High-capacity metal oxide conversion anodes for lithium-ion batteries (LIBs) are primarily limited by their poor reversibility and cycling stability. In this study, a promising approach has been developed to improve the electrochemical performance of a MoO2 anode by direct fluorination of the prelithiated MoO2 . The fluorinated anode contains a mixture of crystalline MoO2 and amorphous molybdenum oxyfluoride phases, as determined from a suite of characterization methods including X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, and scanning transmission electron microscopy. Electrochemical measurements indicate that fluorination facilitates the conversion reaction kinetics, which leads to increased capacity, higher coulombic efficiency, and better cycling stability as compared to the nonfluorinated samples. These results suggest that fluorination after prelithiation not only favors formation of the oxyfluoride phase but also improves the lithium-ion diffusivity and reversibility of the conversion reaction, making it an attractive approach to address the problems of conversion electrodes. These findings provide a new route to design high-capacity negative electrodes for LIBs.

Crystallization of TiO2-MoS2 Hybrid Material under Hydrothermal Treatment and Its Electrochemical Performance

Hydrothermal crystallization was used to synthesize an advanced hybrid system containing titania and molybdenum disulfide (with a TiO₂:MoS₂ molar ratio of 1:1). The way in which the conditions of hydrothermal treatment (180 and 200 °C) and thermal treatment (500 °C) affect the physicochemical properties of the products was determined. A physicochemical analysis of the fabricated materials included the determination of the microstructure and morphology (scanning and transmission electron microscopy—SEM and TEM), crystalline structure (X-ray diffraction method—XRD), chemical surface composition (energy dispersive X-ray spectroscopy—EDS) and parameters of the porous structure (low-temperature N₂ sorption), as well as the chemical surface concentration (X-ray photoelectron spectroscop—XPS). It is well known that lithium-ion batteries (LIBs) represent a renewable energy source and a type of energy storage device. The increased demand for energy means that new materials with higher energy and power densities continue to be the subject of investigation. The objective of this research was to obtain a new electrode (anode) component characterized by high work efficiency and good electrochemical properties. The synthesized TiO₂-MoS₂ material exhibited much better electrochemical stability than pure MoS₂ (commercial), but with a specific capacity ca. 630 mAh/g at a current density of 100 mA/g.

Interfacial Superassembly of Grape-Like MnO-Ni@C Frameworks for Superior Lithium Storage

Despite the excellent electrochemical performance of MnO-based electrodes, a large capacity increase cannot be avoided during long-life cycling, which makes it difficult to seek out appropriate cathode materials to match for commercial applications. In this work, a grape-like MnO-Ni@C framework from interfacial superassembly with remarkable electrochemical properties was fabricated as anode materials for lithium-ion batteries. Electrochemical analysis indicates that the introduction of Ni not only contributes to the excellent rate capability and high specific capacity but also prevents further oxidation of MnO to the higher valence states for ultrastable long-life cycling performance. Furthermore, thermodynamic calculation proves that the ultrastable long cycling life of the Ni-Mn-O system originated from a buffer composition region to stabilize the MnO structure. Because of the unique grape-like structure and performance of the Ni-Mn-O system, the MnO-Ni@C electrode displayed an invertible specific capacity of 706 mA h g^-1 after 200 cycles at a current density of 0.1 A g^-1 and excellent cycling stability maintained a capacity of 476.8 mA h g^-1 after 2100 cycles at 1.0 A g^-1 without obvious capacity change. This new nanocomposite material could offer a novel fabrication strategy and insight for MnO-based materials and other metal oxides as anodes for improved electrochemical performance.

Encapsulating N-Doped Carbon Nanorod Bundles/MoO2 Nanoparticles via Surface Growth of Ultrathin MoS2 Nanosheets for Ultrafast and Ultralong Cycling Sodium Storage

Conversion-type anode materials possess high theoretical capacity for sodium-ion batteries (SIBs), owing to multi-electron transmission (2-6 electrons). Mo-based chalcogenides are a class of great promise, high-capacity host materials, but their development still undergoes serious volume changes and low transport kinetics during the cycling process. Here, MoO₂ nanoparticles anchored on N-doped carbon nanorod bundles (N-CNRBs/MoO₂) are synthesized by a facile self-polymerized route and a following annealing. After hydrothermal sulfuration, N-CNRBs/MoO₂ composites are encapsulated by surface growth of ultrathin MoS₂ nanosheets, acquiring hierarchical N-CNRBs/MoO₂@MoS₂ composites. Serving as the SIB anode, the N-CNRBs/MoO₂@MoS₂ electrode exhibits significantly improved sodium-ion storage properties. The reversible capacity is up to 554.4 mA h g^-1 at 0.05 A g^-1 and maintains 249.3 mA h g^-1 even at 10.0 A g^-1. During 5000 cycles, no obvious capacity decay is observed and the reversible capacities retain 334.8 mA h g^-1 at 3.0 A g^-1 and 301.4 mA h g^-1 at 5.0 A g^-1. These properties could be ascribed to the vertical encapsulation of MoS₂ nanosheets on high-crystalline N-CNRBs/MoO₂ substrates. The hierarchical architecture and unique heterostructure between MoO₂ and MoS₂ synergistically facilitate sodium-ion diffusion, relieve volume changes, and boost pseudocapacitive charge storage of N-CNRBs/MoO₂@MoS₂ electrode. Therefore, the rational growth of nanosheets on complex substrates shows promising potential to construct anode materials for high-performance batteries.

Highly uniform nitrogen-doped carbon decorated MoO2 nanopopcorns as anode for high-performance lithium/sodium-ion storage

Molybdenum dioxides (MoO₂) featuring low cost and high theoretical capacity endow them competitive anode materials for lithium-ion batteries (LIBs)/sodium-ion batteries (SIBs). However, the low electrical conductivity and severe volume expansion occurring during the ion insertion/extraction process hamper their practical application. Herein, a novel dual-annealing design has been developed for the synthesis of highly uniform MoO₂ nanopopcorns decorated with nitrogen-doped carbon shell (MoO₂/NC). Owing to the unique structural characteristics and vital amorphous NC component, the MoO₂/NC nanopopcorn hybrid composite exhibits stabilized charge storage capacity of 1073 mAh g^-1 after 200 cycles for LIBs, while 301 mAh g^-1 after 500 cycles for SIBs at 0.5 A g^-1. Furthermore, when the current density increases to 5 A g^-1, the specific capacity could still maintain 630 mAh g^-1 and 174 mAh g^-1 for LIBs and SIBs, respectively, which disclose the outstanding rate capability of MoO₂/NC nanopopcorn anode.

Multiple Anionic Transition-Metal Oxycarbide for Better Lithium Storage and Facilitated Multielectron Reactions

As an important class of multielectron reaction materials, the applications of transition-metal oxides (TMOs) are impeded by volume expansion and poor electrochemical activity. To address these intrinsic limitations, the renewal of TMOs inspires research on incorporating an advanced interface layer with multiple anionic characteristics, which may add functionality to support properties inaccessible to a single-anion TMO electrode. Herein, a transition-metal oxycarbide (TMOC, M = Mo) with more than one anionic species was prepared as an interface layer on a corresponding oxide. A multiple anionic TMOC possesses advantages of structural stability, abundant active sites, and elevated metal cation valence states. Such merits mitigate volume changes and enhance multielectron reactions significantly. The TMOC nanocomposite has a well-maintained capacity after 1000 cycles at 2 A·g^-1 and fully resumed rate performance. In situ synchrotron X-ray powder diffraction (SXRPD) analysis unveils negligible volume expansions occurring upon oxycarbide layer coupling, with lattice spacing variation less than 1% during cycling. The lithium storage mechanism is further inspected by combined analysis of kinetics, SXRPD, and first-principles calculations. Superior to TMO, multielectron reactions of the TMOC electrode have been boosted due to easier rupture of the metal-oxygen bond. Such improvements underscore the importance of incorporating an oxycarbide configuration as a strategy to expand applications of TMOs.

One-dimensional architecture with reduced graphene oxide supporting ultrathin MoO2 nanosheets as high performance anodes for lithium-ion batteries

Two-dimensional (2D) materials have been widely studied and used as anode materials for lithium ion batteries (LIBs) because of their high specific surface area and intrinsic mechanical flexibility which could offer numerous active sites and protect effect for LIBs. However, 2D nanosheets are easy to stack and partially lose surface area for Li-ion storage thus greatly affecting their electrochemical performance. Here, we develop a simple strategy to obtain a nanosheets-based one-dimensional structure hybrid by in situ reduction from MoO₃ nanorods to MoO₂ nanosheets and nanoparticles which are anchored on a 1D reduced graphene oxide skeleton (MoO₂-rGO). It was demonstrated that the primary MoO₂ nanosheets and nanoparticles are uniformly dispersed on the reduced graphene oxide nanosheets, which are further assembled into a 1D loosened nanostructure. The loosened nanosheets offer more accessible surface area and facilitate transport of electrons and Li-ions. Moreover, MoO₂ nanoparticles effectively avoid agglomeration from nanosheets. Results show that MoO₂-rGO hybrid demonstrates an enhanced cyclic life, high stability and prominent rate performance when evaluated as anode material for LIBs. The first discharge capacity can reach 1256.4 mAh g^-1 and provide a highly reversible capacity of 1003.7 mA h g^-1 after 100 cycles at 0.1 A g^-1, which makes MoO₂-rGO a promising candidate for LIBs. The excellent performance can be attributed to the unique 1D loosened structure consists of MoO₂ and conducting rGO nanosheets, which facilitates fast transfer of Li-ion and electron, and the reduced graphene oxide nanosheets acting as a skeleton provide a continuous conductive network and simultaneously strengthen the structural stability.

Pseudocapacitive Li-ion storage boosts high-capacity and long-life performance in multi-layer CoFe2O4/rGO/C composite

Due to the intrinsic low electrical conductivity and large volume expansion of the CoFe₂O₄ based active materials, designing more novel structures is still one of the most important challenges for its lithium ion battery application. In this work, the CoFe₂O₄/reduced graphene oxide/carbon (CFO/rGO/C) composite with integrated multi-layer structure has been synthesized through a facial two-step hydrothermal method. Benefiting from the introduction of the graphene network and amorphous carbon coating layer, as well as the accompanying synergistic effect, this composite can exhibit fast and reversible lithium intercalation/deintercalation reactions. With the aid of a surface-induced capacitive process, the CFO/rGO/C composite delivers a superior specific capacity (945 mA h g^-1 at 0.1 A g^-1) and excellent long-term cyclic stability (421 mA h g^-1 at 4 A g^-1 with closely 100% Coulombic efficiency after 2000 cycles). Significantly, at a high current density of 1 A g^-1, the reversible capacity exhibits a rapid increasing after 100 cycles and finally shows an ultra-high-capacity of 1430 mA h g^-1 over 500 cycles. This method could be generalized to the preparation of other similar transition metal oxide-based materials for the development of high-performance energy storage systems.

Electrochemistry-related aspects of safety of graphene-based non-aqueous electrochemical supercapacitors: a case study with MgO-decorated few-layer graphene as an electrode material

Composites such as MgO/few-layered graphene can be used as electrode materials in supercapacitors with aqueous electrolytes but not non-aqueous electrolytes.

Amorphous Vanadium Oxide Thin Films as Stable Performing Cathodes of Lithium and Sodium-Ion Batteries

Herein, we report additive- and binder-free pristine amorphous vanadium oxide (a-VOx) for Li- and Na-ion battery application. Thin films of a-VOx with a thickness of about 650 nm are grown onto stainless steel substrate from crystalline V₂O₅ target using pulsed laser deposition (PLD) technique. Under varying oxygen partial pressure (pO₂) environment of 0, 6, 13 and 30 Pa, films bear O/V atomic ratios 0.76, 2.13, 2.25 and 2.0, respectively. The films deposited at 6‑30 Pa have a more atomic percentage of V⁵⁺ than that of V⁴⁺ with a tendency of later state increased as pO₂ rises. Amorphous VOx films obtained at moderate pO₂ levels are found superior to other counterparts for cathode application in Li- and Na-ion batteries with reversible capacities as high as 300 and 164 mAh g^-1 at 0.1 C current rate, respectively. At the end of the 100th cycle, 90% capacity retention is noticed in both cases. The observed cycling trend suggests that more is the (V⁵⁺) stoichiometric nature of a-VOx better is the electrochemistry.

High capacity MoO3/rGO nanocomposite anode for lithium ion batteries: an intuition into the conversion mechanism of MoO3

rGO wrapped MoO₃ NPs were successfully synthesized via simple and scalable steps as potential anode materials for Li-ion batteries.

Fe2Mo3O8/exfoliated graphene oxide: solid-state synthesis, characterization and anodic application in Li-ion batteries

An Fe₂Mo₃O₈/exfoliated graphene oxide (EG) composite with unique morphology is synthesized by a novel solid-state reduction method.

Constructing MoO2 Porous Architectures Using Graphene Oxide Flexible Supports for Lithium Ion Battery Anodes

Graphene oxide flexibly supported MoO2 porous architectures (MoO2/GO) by decomposition of the prepared ammonium molybdate/GO preforms is fabricated. Focused ion beam microscope analysis shows that the inside structures of the architectures strongly depend on the percentages of the GO used as flexible supports: micrometer scale MoO2 particulates growing on the GO (micrometer MoO2/GO), 3D honeycomb-like nanoarchitectures (MoO2/GO nanohoneycomb), and layered MoO2/GO architectures are achieved at the percentage of GO at 4.3, 15.2, and 20.8 wt%, respectively. The lithium storage performance of the MoO2/GO architectures strongly depends on their inside structures. At the current density of 100 mA g-1, the capacities of the micrometer MoO2/GO, MoO2/GO nanohoneycomb, and layered MoO2/GO remain at 901, 1127, and 967 mAh g-1 after 100 cycles. The average coulombic efficiencies of micrometer MoO2/GO, MoO2/GO nanohoneycomb, and layered MoO2/GO electrodes are 97.6%, 99.3%, and 99.0%. Moreover, the rate performance shows even cycled at a high current density of 5000 mA g-1, the MoO2/GO nanohoneycomb can deliver the capacity as high as 461 mAh g-1. The MoO2/GO nanohoneycomb exhibits best performance attributed to its unique nanohoneycomb structure constructed with ultrafine MoO2 fixed on the GO flexible supports.

Copper ferrites@reduced graphene oxide anode materials for advanced lithium storage applications

Copper ferrites are emerging transition metal oxides that have potential applications in energy storage devices. However, it still lacks in-depth designing of copper ferrites based anode architectures with enhanced electroactivity for lithium-ion batteries. Here, we report a facile synthesis technology of copper ferrites anchored on reduced graphene oxide (CuFeO₂@rGO and Cu/CuFe₂O₄@rGO) as the high-performance electrodes. In the resulting configuration, reduced graphene offers continuous conductive channels for electron/ion transfer and high specific surface area to accommodate the volume expansion of copper ferrites. Consequently, the sheet-on-sheet CuFeO₂@rGO electrode exhibits a high reversible capacity (587 mAh g⁻¹ after 100 cycles at 200 mA g⁻¹). In particular, Cu/CuFe₂O₄@rGO hybrid, which combines the advantages of nano-copper and reduced graphene, manifests a significant enhancement in lithium storage properties. It reveals superior rate capability (723 mAh g⁻¹ at 800 mA g⁻¹; 560 mAh g⁻¹ at 3200 mA g⁻¹) and robust cycling capability (1102 mAh g⁻¹ after 250 cycles at 800 mA g⁻¹). This unique structure design provides a strategy for the development of multivalent metal oxides in lithium storage device applications.

Formation of Mo-Polydopamine Hollow Spheres and Their Conversions to MoO2 /C and Mo2 C/C for Efficient Electrochemical Energy Storage and Catalyst

Highly uniform hierarchical Mo-polydopamine hollow spheres are synthesized for the first time through a liquid-phase reaction under ambient temperature. A self-assembly mechanism of the hollow structure of Mo-polydopamine precursor is discussed in detail, and a determined theory is proposed in a water-in-oil system. Via different annealing process, these precursors can be converted into hierarchical hollow MoO₂ /C and Mo₂ C/C composites without any distortion in shape. Owing to the well-organized structure and nanosize particle embedding, the as-prepared hollow spheres exhibit appealing performance both as the anode material for lithium-ion batteries and as the catalyst for hydrogen evolution reaction (HER). Accordingly, MoO₂ /C delivers a high reversible capacity of 940 mAh g^-1 at 0.1 A g^-1 and 775 mAh g^-1 at 1 A g^-1 with good rate capability and long cycle performance. Moreover, Mo₂ C/C also exhibits an enhanced electrocatalytic performance with a low overpotential for HER in both acidic and alkaline conditions, as well as remarkable stability.

Co2Mo3O8/reduced graphene oxide composite: synthesis, characterization, and its role as a prospective anode material in lithium ion batteries

Easy solid state synthesis of Co₂Mo₃O₈/reduced graphene oxide composite which exhibited a very high specific capacity (∼954 mA h g⁻¹) when tested as an anode material in lithium ion batteries.

Simple synthesis of MoO2/carbon aerogel anodes for high performance lithium ion batteries from seaweed biomass

We present a simple and eco-friendly method to synthesize MoO₂/carbon aerogel anodes using alginate as the carbon precursor.