Synthesis of porous CoMoO4 nanorods as a bifunctional cathode catalyst for a Li-O2 battery and superior anode for a Li-ion battery

Amorphous Co-Mo-S nanospheres fabricated via room-temperature vulcanization for asymmetric supercapacitors

Ternary metal sulfides employed in supercapacitors exhibit better electrochemical performances than their counterpart oxides due to their superior conductivity. However, the insertion/extraction of electrolyte ions can lead to a significant volume change in electrode materials, which can result in poor cycling stability. Herein, novel amorphous Co-Mo-S nanospheres were fabricated through a facile room-temperature vulcanization method. It involves the conversion of crystalline CoMoO4 by reacting it with Na2S at room temperature. In addition to the conversion of the crystalline state into an amorphous structure with more grain boundaries, which is beneficial for the transport of electron/ion and can accommodate the volume change generated by the insertion/extraction of electrolyte ions, the production of more pores led to an increased specific surface area. The electrochemical results indicate that the as-prepared amorphous Co-Mo-S nanospheres had a specific capacitance of up to 2049.7F/g@1 A/g together with good rate capability. The amorphous Co-Mo-S nanospheres can be used as the cathode of supercapacitors and assembled with an activated carbon anode into an asymmetric supercapacitor possessing a satisfactory energy density of 47.6 Wh kg-1@1012.9 W kg-1. One of the prominent features exhibited by this asymmetric device is its remarkable cyclic stability, with a capacitance retention of 107% after 10,000 cycles.

Three-dimensional nano assembly of nickel cobalt sulphide/polyaniline@polyoxometalate/reduced graphene oxide hybrid with superior lithium storage and electrocatalytic properties for hydrogen evolution reaction

Engineering hierarchical nanostructures with enhanced charge storage capacity and electrochemical activity are vital for the advancement of energy devices. Herein, a highly ordered mesoporous three-dimensional (3D) nano-assembly of Nickel Cobalt Sulphide/Polyaniline @Polyoxometalate/Reduced Graphene Oxide (NiCo₂S₄/PANI@POM/rGO) is prepared first time via a simple route of oxidative polymerization followed by a hydrothermal method. Morphological analysis of the resulting hybrid reveals the sheet-like structures containing a homogeneous assembly of PANI@POM and NiCo₂S₄ on the graphene exterior maintaining huge structural integrity, large surface area and electrochemically active centres. The electrochemical analysis of the nanohybrid as the anode of the lithium-ion battery (LIB) has delivered ultra-huge reversible capacity of 735.5 mA h g^-1 (0.1 A g^-1 after 200 cycles), superb capacity retention (0.161% decay/per cycle at 0.5 A g^-1 for 1000 cycles), and significant rate capability (355.6 mA h g^-1 at 2 A g^-1). The hydrogen evolution reaction (HER) measurement also proves remarkable activity, extremely low overpotential and high durability. The extraordinary performance of the nanohybrid is due to the presence of abundant electroactive centres, high surface area and a large number of ion exchange channels. These outstanding results prove the advantages of a combination of NiCo₂S₄, graphene sheets, and PANI@POM in energy devices.

Tuning the oxygen vacancy of mixed multiple oxidation states nanowires for improving Li-air battery performance

Mixed multiple oxidation states CoMoO₄ nanowires (electrocatalysts) with tunable intrinsic oxygen vacancies were fabricated. CoMoO₄ with proper oxygen vacancy can be employed to construct a Li-air battery with a high capacity and stable cyclability. This is possible because CoMoO₄ contains surface oxygen vacancies, which result in the unit of CoMo bond, that is important for electrocatalysts used in Li-air batteries. Both the experimental and theoretical results demonstrate that the surface oxygen vacancies containing CoMoO₄ nanowires have a higher electrocatalytic activity. This shows that the highly efficient electrocatalysts used for Li-air batteries were designed to modify the redox properties of the mixed metal oxide in the catalytic active sites. This successful material design led to an improved strategy for high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities based on the fast formation and extinction of ORR products.

Rational design of walnut-like ZnO/Co3O4 porous nanospheres with substantially enhanced lithium storage performance

Rational fabrication and smart design of multi-component anode materials to achieve desirable reversible capacities and exceptional cyclability are significant for lithium-ion batteries (LIBs). Herein, walnut-like ZnO/Co₃O₄ porous nanospheres were prepared by a facile solvothermal method, which were then applied as a mechanically stable anode material for LIBs. The rationally designed hybridized electrode brings favorable structural features, particularly ZnO/Co₃O₄ porous nanospheres with abundant vacant space and enhanced surface area, enhancing lithium/electron transport and relieving volumetric stresses during the cycling process. Moreover, several in situ hybridized anode materials with electrochemical cooperation further overcome the challenge of capacity decay and conductivity deficiency. The as-obtained ZnO/Co₃O₄ delivered a much better lithium storage performance compared with ZnO, Co₃O₄, and their physical mix. We believe that the novel design criteria will bring opportunities in exploration and promote the practical application of transition metal oxides.

Defects enriched cobalt molybdate induced by carbon dots for a high rate Li-ion battery anode

A defects-enriched CoMoO₄/carbon dot (CD) with CoMoO₄around 37 nm is achieved via hydrothermal reaction by introducing CDs to buffer large volume changes of CoMoO₄during lithiation-delithiation and enhance rate performance. The phase, morphology, microstructure, as well as the interface of the CoMoO₄/CD composites were investigated by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. When employed as Li-ion battery anode, the CoMoO₄/CD exhibits a reversible capacity of ∼531 mAh g^-1after 400 cycles at a current density of 2.0 A g^-1. Under the scan rate at 2 mV s^-1, the CoMoO₄/CD shows accounts for 81.1% pseudocapacitance. It may attribute to the CoMoO₄with surface defects given more reaction sites to facilitate electrons and lithium ions transfer at high current densities. Through galvanostatic intermittent titration technique, the average lithium ion diffusion coefficient calculated is an order of magnitude larger than that of bulk CoMoO₄, indicating that the CoMoO₄/CD possesses promising electrons and lithium ions transportation performance as anode material.

POM-Based MOF-Derived Co3O4/CoMoO4 Nanohybrids as Anodes for High-Performance Lithium-Ion Batteries

Polyoxometalate (POM)-based metal-organic framework (MOF)-derived Co₃O₄/CoMoO₄ nanohybrids were successfully fabricated by a facile solvothermal method combined with a calcination process, in which a Co-based MOF, that is, ZIF-67 acts as a template while a Keggin-type POM (H₃PMo₁₂O₄₀) serves as a compositional modulator. The materials were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS) mapping, and electrochemical measurements. When the Co₃O₄/CoMoO₄ nanohybrids were applied as anode materials for lithium-ion batteries (LIBs), they display large lithium storage capacity (around 900 mAh g^-1 at 0.1 A g^-1) and high cycling stability, and they can also exhibit good rate performances. This work might shed some light on the POM-based MOF host-guest synthesis strategy for the preparation of polymetallic oxides for enhanced electrochemical energy storage and further applications.

Synergizing Phase and Cavity in CoMoOx Sy Yolk-Shell Anodes to Co-Enhance Capacity and Rate Capability in Sodium Storage

Sodium-ion batteries (SIBs) have been recognized as the promising alternatives to lithium-ion batteries for large-scale applications owing to their abundant sodium resource. Currently, one significant challenge for SIBs is to explore feasible anodes with high specific capacity and reversible pulverization-free Na⁺ insertion/extraction. Herein, a facile co-engineering on polymorph phases and cavity structures is developed based on CoMo-glycerate by scalable solvothermal sulfidation. The optimized strategy enables the construction of CoMoO_x S_y with synergized partially sulfidized amorphous phase and yolk-shell confined cavity. When developed as anodes for SIBs, such CoMoO_x S_y electrodes deliver a high reversible capacity of 479.4 mA h g^-1 at 200 mA g^-1 after 100 cycles and a high rate capacity of 435.2 mA h g^-1 even at 2000 mA g^-1 , demonstrating superior capacity and rate capability. These are attributed to the unique dual merits of the anodes, that is, the elastic bountiful reaction pathways favored by the sulfidation-induced amorphous phase and the sodiation/desodiation accommodatable space benefits from the yolk-shell cavity. Such yolk-shell nano-battery materials are merited with co-tunable phases and structures, facile scalable fabrication, and excellent capacity and rate capability in sodium storage. This provides an opportunity to develop advanced practical electrochemical sodium storage in the future.

The rational design of carbon coated Fe2(MoO4)3 nanosheets for lithium-ion storage with high initial coulombic efficiency and long cycle life

Binary metal oxides are potential anode materials for lithium-ion storage due to their high theoretical specific capacities. However, the practical applications of metal oxides are limited due to their large volume changes and sluggish reaction kinetics. Herein, carbon coated Fe₂(MoO₄)₃ nanosheets are prepared via a simple method, adopting urea as the template and carbon source. The carbon coating on the surface helps to elevate the conductivity of the active material and maintain structural integrity during the lithium storage process. Combining this with a catalytic effect from the generated Fe, leading to the reversible formation of a solid electrolyte interface layer, a high initial coulombic efficiency (>87%) can be obtained. Based on this, the carbon coated Fe₂(MoO₄)₃ nanosheets show excellent rate capability (a reversible discharge capacity of 983 mA h g^-1 at 5 A g^-1) and stable cycling performance (1376 mA h g^-1 after 250 cycles at 0.5 A g^-1 and 864 mA h g^-1 after 500 cycles at 2 A g^-1). This simple in situ carbonization and template method using urea provides a facile way to optimize electrode materials for next-generation energy storage devices.

MoS2 Nanoflower-Derived Interconnected CoMoO4 Nanoarchitectures as a Stable and High Rate Performing Anode for Lithium-Ion Battery Applications

In recent years, conversion-based mixed transition-metal oxides have emerged as a potential anode for the next generation lithium-ion batteries because of their high theoretical capacity and high rate performance. Herein, an interconnected cobalt molybdenum oxide (CoMoO₄) nanoarchitecture derived from molybdenum sulfide (MoS₂) nanoflowers is investigated as an anode for lithium-ion batteries. The interconnected CoMoO₄ displayed an excellent discharge capacity of 1100 mA h g^-1 over 100 cycles at a current rate of C/5. Moreover, the material exhibited an enhanced electrochemical stability, high rate performance, and delivered high discharge capacities of 600 and 220 mA h g^-1, respectively, at 5 C and 10 C after 500 cycles. The excellent cycling stability and high rate performance of interconnected CoMoO₄ are credited to its unique architecture and porous morphology. The above characteristics and the synergetic effect between the constituting metal ions not only provided a shorter diffusion path for the lithium-ion conduction but also improved the electronic conductivity and mechanical strength of the anode. The field-emission scanning electron microscopy analysis of the electrochemically cycled electrode revealed good structural integrity of the electrode. Further, the practical feasibility of interconnected CoMoO₄ in the full cell was analyzed by integrating it with the LiNi_0.8Mn_0.1Co_0.1O₂ cathode, which demonstrated excellent cycling stability and high rate performance.

Co0.8Zn0.2MoO4/C Nanosheet Composite: Rational Construction via a One-Stone-Three-Birds Strategy and Superior Lithium Storage Performances for Lithium-Ion Batteries

CoMoO₄ has gained great attention as an anode material for lithium-ion batteries owing to its high theoretical capacity of 980 mAh g^-1 and relatively high electrochemical activity. Unfortunately, CoMoO₄ anode also has some drawbacks such as low electronic/ionic conductivity, inferior cyclic stability, and relative severe volumetric expansion during the lithiation/delithiation process, greatly inhibiting its further development and application. Herein, we report Co_0.8Zn_0.2MoO₄/C nanosheet composite constructed via a novel and facile one-stone-three-birds strategy. The preparation of the Co_0.8Zn_0.2MoO₄/C nanosheet is based on the following two-step process: the formation of Co/Zn nanosheet precursors derived from Co/Zn-ZIF rhombic dodecahedra via solvothermal pretreatment, followed by a calcination treatment with molybdic acid (H₂MoO₄) in air. The as-prepared Co_0.8Zn_0.2MoO₄/C is monoclinic crystal structured composite with the in situ formed active carbon, which is well-defined nanosheet with a rough surface and mean thickness of 60-70 nm for a single sheet. This Co_0.8Zn_0.2MoO₄/C nanosheet composite possesses a larger surface area of 37.60 m² g^-1, showing a mesoporous structure. When used as anode materials, the as-obtained Co_0.8Zn_0.2MoO₄/C composite can deliver as high as a discharge capacity of 1337 mAh g^-1 after 300 cycles at 0.2C and still retain the capacity of 827 mAh g^-1 even after 600 cycles at 1C, exhibiting outstanding lithium storage performances. The higher capacity and superior cyclic stability of the Co_0.8Zn_0.2MoO₄/C composite should be ascribed to the synergistic effect of the substitution of Zn²⁺, in situ composited active carbon and the as-constructed unique microstructure for the Co_0.8Zn_0.2MoO₄/C composite. Our present work provides a facile one-stone-three-birds strategy to effectively construct the architectures and significantly enhance electrochemical performances for other transition metal electrode materials.

Kinetic and Electrochemical Reaction Mechanism Investigations of Rodlike CoMoO4 Anode Material for Sodium-Ion Batteries

Sodium-ion batteries are considered the most promising power source for electrical energy storage systems because of the abundance of sodium and their significant cost advantages. However, high-performance electrode materials are required for their successful application. Herein, we report a monoclinic-type CoMoO₄ material which is synthesized by a simple solution method. An optimized calcination temperature with a high crystallinity and a rodlike morphology of the material are selected after analyzing the as-synthesized powder by temperature-dependent time-resolved X-ray diffraction. The CoMoO₄ rods exhibit initial discharge and charge capacities of 537 and 410 mA h g^-1, respectively, when used as an anode for sodium-ion batteries. The sodium diffusion coefficient in the bimetallic CoMoO₄ anode is measured using the galvanostatic intermittent titration technique and calculated in the range of 1.565 × 10^-15 to 4.447 × 10^-18 cm² s^-1 during the initial cycle. Further, the reaction mechanism is investigated using ex situ X-ray diffraction and X-ray absorption spectroscopy, and the obtained results suggest an amorphous-like structure and reduction/oxidation of Co and Mo during the sodium insertion/extraction process. Ex situ transmission electron microscopy and energy-dispersive spectroscopy images of the CoMoO₄ anode in fully discharged and recharged state reveal the rodlike morphology with homogenous element distribution.

Top-down tailoring of nanostructured manganese molybdate enhances its lithium storage properties

Aggregated manganese molybdate micron-whiskers are tailored to nanospheres by a facile top-down strategy in the aqueous phase at room temperature.

One-dimensional MoO2–Co2Mo3O8@C nanorods: a novel and highly efficient oxygen evolution reaction catalyst derived from metal–organic framework composites

One dimensional MoO₂–Co₂Mo₃O₈@C nanorods were synthesized by using MoO₃@ZIF-67 composites as a precursor and the catalyst Co₂Mo₃O₈ shows excellent OER activity.

Improved Li-storage performance with PEDOT-decorated MnO2 nanoboxes

In this paper, MnO₂ nanoboxes coated with poly(3,4-ethylenedioxythiophene) film (denoted as MnO₂@PEDOT) are investigated as an anode material in lithium-ion batteries. The MnO₂ nanoboxes are developed through the surface chemical oxidation decomposition of MnCO₃ cubes and the subsequent removal of their remaining cores. PEDOT is coated on the surface of MnO₂ nanoboxes via in situ polymerization of 3,4-ethylenedioxythiophene. The charge-discharge tests demonstrate that this special configuration endows the resulting MnO₂@PEDOT with remarkable electrochemical performances, that is a reversible capacity of 628 mA h g^-1 after 850 cycles at a current density of 1000 mA g^-1 and a rate capacity of 367 mA h g^-1 at 3000 mA g^-1. The results indicate that the nanoboxes provide the paths for Li-ion diffusion, the reaction sites for Li-ion intercalation/deintercalation and the space to buffer the volume change during the charge-discharge process, while the conductive polymer ensures the structural stability and improves the electronic conductive property of MnO₂.

Recent advances in understanding of the mechanism and control of Li2O2formation in aprotic Li–O2batteries

This review systematically summarizes the recent advances in the mechanism studies and control strategies of Li₂O₂formation in aprotic Li–O₂batteries.

Synthesis of graphene wrapped porous CoMoO4 nanospheres as high-performance anodes for rechargeable lithium-ion batteries

Herein, we described a facile method to synthesise porous CoMoO₄ nanospheres wrapped with graphene (CoMoO₄@G).