Synthesis of hierarchical MgO based on a cotton template and its adsorption properties for efficient treatment of oilfield wastewater

A biomorphic MgO nanomaterial was fabricated via a facile and low-cost immersion method using cotton as the template. The obtained materials were characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and N₂ adsorption–desorption analysis. The as-prepared MgO retained the structure of cotton, with a porous hierarchical structure and a high specific surface area, which endowed it with great potential due to its excellent adsorption properties for the adsorption of additives in oil field wastewater. It also exhibited the maximum adsorption capacity of 391.36 mg g⁻¹ for sulfonated lignite. The adsorption process of sulfonated lignite on biomorphic MgO was systematically investigated and was found to obey the pseudo-second-order rate equation and the Langmuir adsorption model. The negative values of Gibbs free energy change (ΔG) showed that the adsorption process was feasible and spontaneous. The endothermic process was depicted with a positive value for ΔH.

A biomorphic MgO nanomaterial was fabricated via a facile and low-cost immersion method using cotton as the template.     

Enhanced lithium storage performance of V2O5 with oxygen vacancy

Orthorhombic phase V₂O₅ nanosheets with a high V⁴⁺ content (V-V₂O₅) have been fabricated via a facile sol–gel method and freeze-drying technology followed with a vacuum annealing process. XPS tests demonstrated that the content of V⁴⁺ in the as-prepared V-V₂O₅ sample was 7.4%, much higher than that (4.7%) in the V₂O₅ sample annealed in air. Compared with the V₂O₅ annealed in air, the V-V₂O₅ sample exhibited better cycling stability, higher lithium storage activity, and smaller electrochemical reaction resistance when evaluated as a cathode active material for lithium ion batteries. For example, the specific capacity of the V-V₂O₅ and V₂O₅ electrodes after 100 cycles at 200 mA g⁻¹ are 224.7 and 199.2 mA h g⁻¹, respectively; after 200 cycles at 3 A g⁻¹ are 150 and 136.7 mA h g⁻¹, respectively.

Orthorhombic phase V₂O₅ nanosheets with a high V⁴⁺ content (V-V₂O₅) have been fabricated via a facile sol–gel method and freeze-drying technology followed with a vacuum annealing process.     

Free-standing lithiophilic Ag-nanoparticle-decorated 3D porous carbon nanotube films for enhanced lithium storage

Lithium metal batteries are promising candidates for next generation high energy batteries. However, an undesirable dendrite growth hinders their practical applications. Herein, a three-dimensional (3D) porous carbon nanotube film decorated with Ag nanoparticles (CNT/Ag) has been synthesized via the thermal decomposition reaction of AgNO₃ into Ag nanoparticles, and then is transformed into a 3D porous CNT/Ag/Li film via thermal infusion to obtain a high-performance free-standing lithium host. This as-formed 3D CNT/Ag/Li host can effectively restrain the dendrite growth by guiding Li deposition via the highly lithiophilic Ag nanoparticle seeds and lowering local current density of the highly conductive matrix. The as-prepared CNT/Ag/Li electrode exhibits long-term cycling stability over 200 cycles at a current density of 1 mA cm⁻² with an areal capacity of 1.0 mA h cm⁻². Moreover, the full cell paired with a sulfur/C cathode shows good cycling stability. Therefore, the 3D porous CNT/Ag/Li film formed via a facile three-step fabrication process can enlarge the cycle lifetime of a lithium metal anode.

A 3D porous CNT/Ag/Li film as a high-performance free-standing lithium host has been synthesized via combining a thermal decomposition process and thermal infusion process.     

Enhanced thermal conductivity of nanocomposites with MOF-derived encapsulated magnetic oriented carbon nanotube-grafted graphene polyhedra

It remains a challenge to develop highly polymer-based nanocomposite thermal interface materials, which can effectively remove heat developed during the miniaturization of electronic instruments. It has been reported that a large number of graphene-based nanocomposites exhibit excellent performance. However, it is still an issue to construct thermal conductive pathways by orientation arrangements with a low filler volume fraction. Herein, a high-thermal conductivity filler of magnetic carbon nanotube-grafted graphene polyhedra (Co@Co₃O₄-G) was exploited via the annealing of metal–organic frameworks (ZIF-67). Co@Co₃O₄-G can improve the thermal conductivity of nanocomposites obviously by forming oriented pathways for phonon transport in an external magnetic field. Therefore, the resulting nanocomposite displayed a high thermal conductivity of 2.11 W m⁻¹ K⁻¹ for only 8.7 vol%, which is 10 times higher than that of the pure epoxy resin. Core-shell magnetic cobalt oxide (Co@Co₃O₄) was encapsulated in situ in the nanoarchitecture to avoid falling off. Moreover, the equilibrium molecular dynamics (EMD) simulation verifies that Co@Co₃O₄-G had high thermal conductivity to effectively improve the heat dissipation of nanocomposites. This strategy provides an approach for developing high-performance thermal management materials and opens up the possibility for the pioneering applications of encapsulated magnetic-oriented thermal conductive fillers.

A high-thermal conductivity filler of magnetic carbon nanotube-grafted graphene polyhedra is exploited via annealing of a metal–organic framework (ZIF-67).     

The pioneering role of metal–organic framework-5 in ever-growing contemporary applications – a review

MOF-5 with a Zn(ii) cluster and terephthalic acid is a distinctive porous material among the metal–organic frameworks (MOFs), with unique physical, chemical and mechanical properties. MOF-5 based composites possess ample applications in modern chemistry. Huge surface area, suitable pore dimensions and scope of tunability make MOF-5 noteworthy in advanced materials. The extensive features of MOF-5 provided an opportunity for researchers to explore atomic/molecular scale materials. Various MOF-5 based composites have been designed with revamped properties appropriate to the application by altering and fabricating MOF-5 in situ or using a post-synthetic approach. Surface modification via the dispersion and impregnation of active substances into the pores of MOF-5 enhances its applicability. The boundless topologies and morphologies of MOF-5 combined with other chemical entities has provided opportunities in various fields, including catalysis, gas storage and sensors. The present review illuminates the leading role of MOF-5 and its composites in contemporary applications based on the current literature in heterogeneous catalysis, H₂ and CO₂ storage and sensors.

MOF-5 with a Zn(ii) cluster and terephthalic acid is a distinctive porous material among the metal–organic frameworks (MOFs), with unique physical, chemical and mechanical properties.     

A detailed atomistic molecular simulation study on adsorption-based separation of CO2 using a porous coordination polymer

Emission of CO₂ is considered as one of the sources of global warming. Besides its currently inevitable production via several processes such as fuel consumption, it also exists in some other gaseous mixtures like biogas. Separation of carbon dioxide using solid adsorbents, for example porous coordination polymers and metal–organic frameworks, is an interesting active area of separation science. In particular, we performed detailed molecular simulations to investigate the response of a recently reported cobalt-based, pillared-layer, porous polymer on the CO₂ separation from biogas, natural gas, and flue gas. The effect of the coordinated water molecules to the open metal sites on the corresponding properties was studied and revealed enhanced results even in comparison with HKUST-1. Additionally, our results provide insights on the role of –NO₂ groups on the applications examined herein. Overall this study offers valuable insights about secondary building units of the examined materials which we expect to prove useful in the enhancement of carbon dioxide separation and capture.

We examined a new pillared-layered Co-nitroimidazolate dicarboxylate porous coordination polymer for potential use in adsorption-based CO₂ capture     

TiO2-coated LiCoO2 electrodes fabricated by a sputtering deposition method for lithium-ion batteries with enhanced electrochemical performance

We fabricated lithium cobalt oxide (LiCoO₂, LCO) electrodes in the absence and presence of TiO₂ layers as cathodes for lithium-ion batteries (LIBs) using a sputtering deposition method under an Ar atmosphere. In particular, TiO₂ coating layers on sputtered LCO electrodes were directly deposited in a layer-by-layer form with varying TiO₂ sputtering times from 60 to 120 s. These sputtered electrodes were heated at 600 °C in an air atmosphere for 3 h. The thicknesses of TiO₂ layers in TiO₂-coated LCO electrodes were controlled from ∼2 to ∼10 nm. These TiO₂-coated LCO electrodes exhibited superior electrochemical performance, i.e. high capacities (93–107 mA h g⁻¹@0.5C), improved retention of >60% after 100 cycles, and high-rate cycling properties (64 mA h g⁻¹@1C after 100 cycles). Such an improved performance of TiO₂-coated LCO electrodes was found to be attributed to relieved volumetric expansion of LCO and protection of LCO electrodes against HF generated during cycling.

We fabricated lithium cobalt oxide (LiCoO₂, LCO) electrodes in the absence and presence of TiO₂ layers as cathodes for lithium-ion batteries (LIBs) using a sputtering deposition method under an Ar atmosphere.     

An integrated electrode based on nanoflakes of MoS2 on carbon cloth for enhanced lithium storage

Due to its high specific capacity (in theory), molybdenum disulfide (MoS₂) has been recognized as a plausible substitute in lithium-ion batteries (LIBs). However, it suffers from an inferior electric conductivity and a substantial volume change during Li⁺ insertion/extraction. By using a facile hydrothermal method, a flexible free-standing MoS₂ electrode has here been fabricated onto a carbon cloth substrate. The grafting of ultrathin MoS₂ nanoflakes onto the carbon cloth framework (forming CC@MoS₂), was shown to facilitate an improved electron transport, as well as an enhanced Li⁺ transport. As expected, the as-obtained CC@MoS₂ electrode was observed to exhibit an excellent lithium storage performance. It delivers a high discharge specific capacity of 2.42 mA h cm⁻² at 0.7 mA cm⁻² (even after 100 cycles), which is an impressive result.

Integrated carbon cloth@MoS₂ electrode is fabricated via a facile hydrothermal method as a binder-free anode for lithium-ion batteries.     

Temperature modulation of defects in NH2-UiO-66(Zr) for photocatalytic CO2 reduction

Defect engineering can be a promising approach to improve the photocatalytic performance of metal–organic frameworks (MOFs). Herein, a series of defective NH₂-UiO-66(Zr) materials were synthesized via simply controlling the synthesis temperature, with concentrated HCl as the modulator and then these as-prepared samples were used to systematically investigate the effects of their structural defects on photocatalytic CO₂ reduction. Remarkably, these MOFs with defects exhibit significantly enhanced activities in photocatalytic CO₂ reduction, compared with the material without defects. The defect engineering creates active binding sites and more open frameworks in the MOF, and thus facilitates the photo-induced charge transfer and restrains the recombination of photo-generated charges efficiently. The current work provides an instructive approach to improve the photocatalytic efficiency by taking advantage of the structural defects in MOFs, and could also inspire more work on the design of advanced defective MOFs.

NH₂-UiO-66(Zr) materials with structural defects, prepared by simply controlling the synthesis temperature, exhibit significantly enhanced activities in photocatalytic CO₂ reduction.     

C-doped ZnO decorated with Au nanoparticles constructed from the metal–organic framework ZIF-8 for photodegradation of organic dyes

Recently, engineering metal–organic frameworks (MOFs) into metal oxides by solid state thermal decomposition has attracted wide attention for photocatalytic applications. Here, a series of C-doped ZnO materials decorated with Au nanoparticles (Au/C-ZnO) were constructed via controlled pyrolysis of ZIF-8 adsorbing different amounts of HAuCl₄·4H₂O. In this pyrolysis process, ZIF-8 was transformed into C-doped ZnO according to the EDX and XPS analysis. Meanwhile, HAuCl₄·4H₂O was transformed into Au nanoparticles that were uniformly dispersed on the surface of C-ZnO as seen in TEM images. The photocatalytic activity of as-prepared catalysts was evaluated by the degradation of methyl orange under UV-vis light irradiation. It was found that the photocatalytic activity of Au/C-ZnO was better than C-ZnO and pure ZnO. Furthermore, Au/C-ZnO exhibited high photocatalytic stability. After three consecutive cycles, there was no noticeable deactivation in the reaction. This unusual photocatalytic activity was attributed to the synergistic effect of C-doping and Au NPs.

C-doped ZnO decorated with Au nanoparticles (Au/C-ZnO) were prepared via one step pyrolysis of ZIF-8 adsorbing HAuCl₄.     

Nickel-foam-supported β-Ni(OH)2 as a green anodic catalyst for energy efficient electrooxidative degradation of azo-dye wastewater

Electrochemical oxidative degradation (EOD) is a particularly promising technique for removing organic pollutants from wastewater. However, due to the high overpotential of EOD in conventional anode materials, the energy cost of EOD is usually very high, which greatly promotes the search for highly active, stable, and energy-efficient anodic catalysts. Herein, we demonstrated that nickel-foam-supported (NF-supported) β-Ni(OH)₂ (NF/β-Ni(OH)₂) prepared via a facile hydrothermal method could be used as an energy efficient anode for EOD. The as-prepared 3D porous NF/β-Ni(OH)₂ exhibited high activity toward the electrochemical oxidation of methyl orange (MO) in the low potential region (<1.07 V vs. SCE). This property differs greatly from those of the conventional anode materials that require a high positive potential to keep them active for EOD, making NF/β-Ni(OH)₂ an energy-efficient and active anode material for EOD. With an oxidation current density of 0.25 mA cm⁻², the decolorization of MO was completed within 30 min, and the COD removal after 3h of reaction was 63.0%. The normalized energy consumption for the 3 h degradation of MO was 22.2 kW h (kg COD)⁻¹, which is only a fraction of (or even one tenth of) the values reported in the literature. Moreover, NF/β-Ni(OH)₂ had a good stability and recyclability for EOD. No activity decay was observed during 10 h of EOD and the COD removal remained almost unchanged after four consecutive reaction cycles. We demonstrated experimentally that the NF/β-Ni(OH)₂ anode could generate large amounts of hydroxyl radicals and that the oxidation of MO by hydroxyl radicals was the main mechanism during EOD. We believe that this work opens a new avenue for developing highly active and energy-efficient anode materials that can work in the low potential region for EOD.

A novel NF/β-Ni(OH)₂ catalyst for energy efficient electrochemical degradation of methyl orange was fabricated via a facile hydrothermal method.     

Coherent nanoscale cobalt/cobalt oxide heterostructures embedded in porous carbon for the oxygen reduction reaction

Cost-effective and efficient electrocatalysts for the oxygen reduction reaction (ORR) are crucial for fuel cells and metal–air batteries. Herein, we report the facile synthesis of a Co/CoO/Co₃O₄ heterostructure embedded in a porous carbon matrix by refluxing and annealing. This composite exhibits several structural merits for catalyzing the ORR: (1) the existence of metallic Co and graphitic carbon enhanced the electrical conduction; (2) the porous, loose carbon network facilitated the electrolyte permeation and mass transport; (3) more importantly, the nanosized coherent CoO/Co₃O₄ heterojunctions with structural defects and oxygen vacancies enhanced the charge transport/separation at the interface and adsorption affinity to O₂, thus promoting the ORR kinetics and lowering the reaction barrier. Consequently, the composite electrode manifests high electrocatalytic activity, attaining a current density of 6.7 mA cm⁻² at −0.8 V (vs. Ag/AgCl), which is superior to pure CoO nanoparticles (4.7 mA cm⁻²), and has good methanol tolerance. The present strategy based on heterostructure and vacancy engineering may pave the way for the exploration of more advanced, low-cost electrocatalysts for electrochemical reduction and evolution processes.

Cost-effective and efficient electrocatalysts for the oxygen reduction reaction (ORR) are crucial for fuel cells and metal–air batteries.     

Enhancing performance of Ag–ZnO–Ag UV photodetector by piezo-phototronic effect

In this work, an ultraviolet (UV) photodetector based on a ZnO nanowires (NWs) array with metal–semiconductor–metal Schottky junction structure was successfully fabricated on a flexible polyester fibre substrate by a low-temperature hydrothermal method. Subjected to a 0.2% tensile strain at −1 V, the I_light and sensitivity of the as-prepared UV photodetector are lifted by 82% and 130%, respectively. Furthermore, the response speed and recovery speed are significantly raised under the same tensile strain. The working principle can be explained as that the Schottky barrier height (SBH) is effectively improved by the negative strain-induced polarization at the metal–ZnO interface which is favorable for the separation of photogenerated electron–hole pairs. This work not only provides a facile and promising means to optimize the performance of a ZnO based MSM photodetector by applying a tensile strain but also opens up the way for fabrication and integration of ZnO photodetectors on flexible polyester fiber substrates.

An ultraviolet photodetector based on a ZnO nanowires with metal–semiconductor–metal Schottky structure was fabricated on a flexible polyester fibre substrate.     

Ammonia borane dehydrogenation and selective hydrogenation of functionalized nitroarene over a porous nickel–cobalt bimetallic catalyst

The hydrolysis of ammonia borane is a promising strategy for hydrogen energy exploration and exploitation. The in situ produced hydrogen could be directly utilized in hydrogenation reactions. In this work, a bimetallic nickel–cobalt material with porous structure was developed through the pyrolysis of ZIF-67 incorporated with Ni ions. Through the introduction of Ni(NO₃)₂ as an etching agent, the ZIF-67 polyhedrons were transformed into hollow nanospheres, and further evolved into irregular nanosheets. The bimetallic NiCo phase was formed after pyrolysis in a nitrogen atmosphere at high temperature, with the decomposition and release of organic ligands as gaseous molecules under flowing nitrogen. The obtained bimetallic NiCo porous materials show superior catalytic performance towards hydrolytic dehydrogenation of ammonia borane, thereby nitrobenzene with reducible functional groups can be reduced with high selectivity to the corresponding aniline.

Porous nickel–cobalt bimetallic catalyst realizes selective hydrogenation of nitrobenzene with in situ produced hydrogen through hydrolysis of ammonia borane.     

Application of novel metal–organic framework [Zr-UiO-66-PDC-SO3H]FeCl4 in the synthesis of dihydrobenzo[g]pyrimido[4,5-b]quinoline derivatives

In the current paper, we produce a new metal–organic framework (MOF) based on Zr metal, [Zr-UiO-66-PDC-SO₃H]FeCl₄, via an anion exchange method, which is fully characterized by FT-IR, SEM with elemental mapping and EDX, FE-SEM and TEM. Furthermore, the use of [Zr-UiO-66-PDC-SO₃H]FeCl₄ as a porous catalyst was examined for the one-pot synthesis of novel dihydrobenzo[g]pyrimido[4,5-b]quinoline derivatives by reaction of 6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione, 2-hydroxynaphthalene-1,4-dione and various aldehydes at 100 °C with good to excellent yields.

We produce a new metal–organic framework, [Zr-UiO-66-PDC-SO₃H]FeCl₄, via an anion exchange method, and test its use as a porous catalyst.     

A porous nano-adsorbent with dual functional groups for selective binding proteins with a low detection limit

In this study, porous silica nanoparticles functionalized with a thiol group (SiO₂–SH NPs) were synthesized via a one-pot method. Subsequently, iminodiacetic acid was modified, and further adsorption of Ni²⁺ ions was conducted to obtain a SiO₂–S/NH–Ni nano-adsorbent. Then, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TG) and X-ray diffraction (XRD) were employed to characterize its morphology and composition. The results indicate that the SiO₂–S/NH–Ni nano-adsorbent is porous, has an average diameter of 77.1 nm and has a small porous structure of about 3.7 nm in the silica skeleton. The Brunauer–Emmett–Teller (BET) surface area and total pore volume were 537.2 m² g⁻¹ and 3.3 cm³ g⁻¹, respectively, indicating a large BET surface area. The results indicate that the as-prepared SiO₂–S/NH–Ni nano-adsorbent would be suitable to selectively and efficiently bind His-tagged proteins from an E. coli cell lysate. The SDS-PAGE results show that the as-prepared nano-adsorbent presents specifically to both His-tagged CPK4 and His-tagged TRX proteins, indicating the nano-adsorbent can be used to effectively separate His-tagged proteins and is universal to all His-tagged fusion proteins. We also found that the as-prepared nano-adsorbent exhibits a low detection limit (1.0 × 10⁻⁷ mol L⁻¹) and a strong regeneration ability based on four regeneration experiments that were particularly suited to the separation of His-tagged proteins.

Porous nano-adsorbent with dual functional groups for selective binding proteins with a low detection limit.     

Modified SiO hierarchical structure materials with improved initial coulombic efficiency for advanced lithium-ion battery anodes

Silicon-based anode materials are indispensable components in developing high energy density lithium-ion batteries, yet their practical application still faces great challenges, such as large volume change during the lithiation and delithiation process that causes the pulverization of silicon particles, and continuous formation and reformation of the solid electrolyte interfaces (SEI) which results in a low initial coulombic efficiency. As an endeavor to address these problems, in this study, Si/SiO/Li₂SiO₃@C structures were prepared via a facile method using SiO, pitch powder and Li₂CO₃/PVA solution followed by annealing treatment. The Si/SiO/Li₂SiO₃@C composite shows a great improvement in lithium storage where a high discharge capacity of 1645.47 mA h g⁻¹ was delivered with the 1^st C.E. of 69.05% at 100 mA g⁻¹. These results indicate that the designed method of integrating prelithiation and carbon coating for SiO and the as-prepared macro scale Si/SiO/Li₂SiO₃@C structures are practical for implementation in lithium-ion battery technology.

A simple method of prelithiation of SiO along with carbon coating to achieve high performance SiO-based materials.     

Facile synthesis of polyoxometalates tethered to post Fe-BTC frameworks for esterification of free fatty acids to biodiesel

A phosphomolybdic acid (PMA) was sequentially incorporated into highly porous metal–organic frameworks (MOFs, Fe-BTC) by using a facile one-pot synthesis method, and the prepared composite (PMA/Fe-BTC) was employed as an efficient and stable solid acid catalyst for biodiesel production. N₂ adsorption–desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric (TG) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization techniques were employed to reveal the structure–performance relationship. The effects of reaction parameters like catalyst amount, reaction time and temperature were further investigated. This solid acid gave good catalytic performance in the esterification of free fatty acids with methanol, which is attributed to large surface area and thermal stability. The PMA/Fe-BTC was successfully reused for up to six cycles and exhibited high stability. From the kinetic study performed at different reaction temperatures (140 °C, 150 °C and 160 °C) E_a = 49.5 kJ mol⁻¹ was obtained. In addition, due to the high activity presented in various esterifications of free fatty acids, this composite catalytic material has immense potential for industrial biodiesel production.

Phosphomolybdic acid was sequentially incorporated into a highly porous metal–organic framework by a one-pot synthesis method, and the prepared composite was used as an efficient and stable solid acid catalyst for biodiesel production.     

Two-dimensional SnO2 anchored biomass-derived carbon nanosheet anode for high-performance Li-ion capacitors

Lithium-ion capacitors (LICs) combine the advantages of both batteries and supercapacitors; they have attracted intensive attention among energy conversion and storage fields, and one of the key points of their research is the exploration of suitable battery-type electrode materials. Herein, a simple and low-cost strategy is proposed, in which SnO₂ particles are anchored on the conductive porous carbon nano-sheets (PCN) derived from coffee grounds. This method can inhibit the grain coarsening of Sn and the volume change of SnO₂ effectively, thus improving the electrochemical reversibility of the materials. In the lithium half cell (0–3.0 V vs. Li/Li⁺), the as-prepared SnO₂/PCN electrode yields a reversible capacity of 799 mA h g⁻¹ at 0.1 A g⁻¹ and decent long-term cyclability of 313 mA h g⁻¹ at 1 A g⁻¹ after 500 cycles. The excellent Li⁺ storage performance of SnO₂/PCN is beneficial from the hierarchical structure as well as the robust carbonaceous buffer layer. Besides, a LIC hybrid device with the as-prepared SnO₂/PCN anode exhibits outstanding energy and power density of 138 W h kg⁻¹ and 53 kW kg⁻¹ at a voltage window of 1.0–4.0 V. These promising results open up a new way to develop advanced anode materials with high rate and long life.

In this work, we have fabricated lithium-ion capacitor using SnO₂/PCN as anode and waste coffee grounds derived PCN as cathode, which delivers good combination of high energy and power characteristics.     

3D plum candy-like NiCoMnO4@graphene as anodes for high-performance lithium-ion batteries

3D plum candy-like NiCoMnO₄ microspheres have been prepared via ultrasonic spraying and subsequently wrapped by graphene through electrostatic self-assembly. The as-prepared NiCoMnO₄ powders show hollow structures and NiCoMnO₄@graphene exhibits excellent electrochemical performances in terms of rate performance and cycling stability, achieving a high reversible capacity of 844.6 mA h g⁻¹ at a current density of 2000 mA g⁻¹. After 50 cycles at 1000 mA g⁻¹, NiCoMnO₄@graphene delivers a reversible capacity of 1045.1 mA h g⁻¹ while the pristine NiCoMnO₄ only has a capacity of 143.4 mA h g⁻¹. The hierarchical porous structure helps to facilitate electron transfer and Li-ion kinetic diffusion by shortening the Li-ion diffusion length, accommodating the mechanical stress and volume change during the Li-ion insertion/extraction processes. Analysis from the electrochemical performances reveals that the enhanced performances could be also attributed to the reduced charge-transfer resistance and enhanced Li-ion diffusion kinetics because of the graphene-coating. Moreover, Schottky electric field, due to the difference in work function between graphene and NiCoMnO_4, might be favorable for the redox activity of the NiCoMnO₄. In light of the excellent electrochemical performance and simple preparation, we believe that 3D plum candy-like NiCoMnO₄@graphene composites are expected to be applied as a promising anode materials for high-performance lithium ion batteries.

3D plum candy-like NiCoMnO₄ microspheres have been prepared via ultrasonic spraying and subsequently wrapped by graphene through electrostatic self-assembly.