Double-Shelled Hollow SiO2@N-C Nanofiber Boosts the Lithium Storage Performance of [PMo12O40]3−

Polyoxometalates (POMs)-based materials, with high theoretical capacities and abundant reversible multi-electron redox properties, are considered as promising candidates in lithium-ion storage. However, the poor electronic conductivity, low specific surface area and high solubility in the electrolyte limited their practical applications. Herein, a double-shelled hollow PMo₁₂−SiO₂@N−C nanofiber (PMo₁₂−SiO₂@N−C, where PMo₁₂ is [PMo₁₂O₄₀]³⁻, N−C is nitrogen-doped carbon) was fabricated for the first time by combining coaxial electrospinning technique, thermal treatment and electrostatic adsorption. As an anode material for LIBs, the PMo₁₂−SiO₂@N−C delivered an excellent specific capacity of 1641 mA h g⁻¹ after 1000 cycles under 2 A g⁻¹. The excellent electrochemical performance benefited from the unique double-shelled hollow structure of the material, in which the outermost N−C shell cannot only hinder the agglomeration of PMo₁₂, but also improve its electronic conductivity. The SiO₂ inner shell can efficiently avoid the loss of active components. The hollow structure can buffer the volume expansion and accelerate Li⁺ diffusion during lithiation/delithiation process. Moreover, PMo₁₂ can greatly reduce charge-resistance and facilitate electron transfer of the entire composites, as evidenced by the EIS kinetics study and lithium-ion diffusion analysis. This work paves the way for the fabrication of novel POM-based LIBs anode materials with excellent lithium storage performance.     

Filling Polyoxoanions into MIL-101(Fe) for Adsorption of Organic Pollutants with Facile and Complete Visible Light Photocatalytic Decomposition

Transition metal-substituted polyoxometalates (POMs) were filled into a metal–organic framework (MOF) to construct a series of POM@MOF composites (PMo₁₂O₄₀@MIL-101, PMo₁₁VO₄₀@MIL-101, PMo₁₀V₂O₄₀@MIL-101). The composite materials possess ultra-high adsorption ability, especially for PMo₁₀V₂O₄₀@MIL-101, with an adsorption capacity of 912.5 mg·g⁻¹ for cationic antibiotic tetracycline in wastewater, much higher than that of isolated MIL-101(Fe) and the commonly used adsorption materials, such as activated carbon and graphene oxide. In particular, they can be used as efficient photocatalysts for the photodegradation of antibiotics under visible light irradiation. The complete photodegradation of the adsorbed species can induce the facile reusability of these composites for multiple cycles. This work opens an avenue to introduce POMs into an MOF matrix for the simultaneous adsorption and photodegradation of antibiotics.     

3D Carbon Foam Supported Edge-Rich N-Doped MoS2 Nanoflakes for Enhanced Electrocatalytic Hydrogen Evolution

Molybdenum disulfide (MoS₂) is one of the most promising alternatives to the Pt-based electrocatalysts for the hydrogen evolution reaction (HER). However, its performance is currently limited by insufficient active edge sites and poor electron transport. Hence, enormous efforts have been devoted to constructing more active edge sites and improving conductivity to obtain enhanced electrocatalytic performance. Herein, the 3D carbon foam (denoted as CF) supported edge-rich N-doped MoS₂ nanoflakes were successfully fabricated by using the commercially available polyurethane foam (PU) as the 3D substrate and PMo₁₂O₄₀³⁻ clusters (denoted as PMo₁₂) as the Mo source through redox polymerization, followed by sulfurization. Owing to the uniform distribution of nanoscale Mo sources and 3D carbon foam substrate, the as-prepared MoS₂-CF composite possessed well-exposed active edge sites and enhanced electrical conductivity. Systematic investigation demonstrated that the MoS₂-CF composite showed high HER performance with a low overpotential of 92 mV in 1.0 m KOH and 155 mV in 0.5 m H₂SO₄ at a current density of 10 mA cm⁻². This work offers a new pathway for the rational design of MoS₂-based HER electrocatalysts.     

ZIF-67 derived carbon wrapped discontinuous CoxP nanotube as anode material in high-performance Li-ion battery

Transition metal phosphides (TMPs) are prospective anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities and low redox voltages. Herein, we report a template directing method to develop a tube-sheath hybrid composing of cobalt phosphide particles encapsulated in metal organic frameworks (MOFs) derived N-doped carbon sheaths (Co_xP@NC). The utilization of directing template leads to a homogenous distribution of the subsequently formed cobalt phosphide particles, restrains the aggregation of cobalt phosphides, and thus results in the superb rate capability and cyclability. Contributable to the integrated merits of the interior downsized cobalt phosphide particles and the outer ZIF-67 derived porous carbon sheath, the volume expansion during cycling is effectively suppressed. The Co_xP@NC hybrid shows superb electrochemical performance as anode material for LIB, with good reversible capacity of 928 mAh·g^?1 after 100 cycles at 0.1 A g^?1, and high stability of 526 mAh·g^?1 after 600 cycles at 1.0 A g^?1. This work provides a route for rational design of MOF derived carbon-based anode material for LIB, which could also be applied as a promising platform in diverse field.     

β-MnO2/Metal–Organic Framework Derived Nanoporous ZnMn2O4 Nanorods as Lithium-Ion Battery Anodes with Superior Lithium-Storage Performance

Nanoporous ZnMn₂O₄ nanorods have been successfully synthesized by calcining β-MnO₂/ZIF-8 precursors (ZIF-8 is a type of metal–organic framework). If measured as an anode material for lithium-ion batteries, the ZnMn₂O₄ nanorods exhibit an initial discharge capacity of 1792 mA h g⁻¹ at 200 mA g⁻¹, and an excellent reversible capacity of 1399.8 mA h g⁻¹ after 150 cycles (78.1 % retention of the initial discharge capacity). Even at 1000 mA g⁻¹, the reversible capacity is still as high as 998.7 mA h g⁻¹ after 300 cycles. The remarkable lithium-storage performance is attributed to the one-dimensional nanoporous structure. The nanoporous architecture not only allows more lithium ions to be stored, which provides additional interfacial lithium-storage capacity, but also buffers the volume changes, to a certain degree, during the Li⁺ insertion/extraction process. The results demonstrate that nanoporous ZnMn₂O₄ nanorods with superior lithium-storage performance have the potential to be candidates for commercial anode materials in lithium-ion batteries.     

Binder-free carbon-coated nanocotton transition metal oxides integrated anodes by laser surface ablation for lithium-ion batteries

In this paper, an efficient laser surface ablation strategy for producing binder-free carbon-coated nanocotton CoO-Co integrated anode is reported. The fabrication process introduces in-situ growing nanocotton-like CoO on the surface of Co foil via ablating with a nanosecond laser. After that, coated with dopamine as carbon source, the CoO-Co composite foil is heated in Argon atmosphere to form a CoO@C-Co foil as an anode of LIB. The laser surface ablation exhibits high fabrication speed (~10 minutes) and significantly reduces the processing time. The obtained binder-free CoO@C-Co integrated anode shows a unique cotton-like villous structure with large specific surface area and an active material/current collector integrated architecture, which provides a stabilized rapid electronic conduction path. When tested as an anode for LIBs, the CoO@C-Co integrated anode possesses superior performance: First discharge capacity of 1301.5 mAh g⁻¹ is achieved at a current density of 0.1 A g⁻¹. Also at a high current density of 1.5 A g⁻¹, the second discharge capacity of 791.7 mAh g⁻¹ is achieved. After 800 cycles, reversible capacities of 799.8 mAh g⁻¹ can still be achieved with an average coulombic efficiency of nearly 100%. In addition, this strategy is suitable for the production of other carbon coated transition metal oxides integrated anodes, such as NiO@C-Ni, Fe₂O₃/Fe₃O₄@C-Fe, and CuO/Cu₂O@C-Cu integrated anodes.     

Scalable Dry Production Process of a Superior 3D Net‐Like Carbon‐Based Iron Oxide Anode Material for Lithium‐Ion Batteries

Carbon‐based transition‐metal oxides are considered as an appropriate anode material candidate for lithium‐ion batteries. Herein, a simple and scalable dry production process is developed to produce carbon‐encapsulated 3D net‐like FeO_x /C materials. The process is simply associated with the pyrolysis of a solid carbon source, such as filter paper, adsorbed with ferrite nitrate. The carbon derived from filter paper induces a carbothermal reduction to form metallic Fe, the addition of carbon and iron increase the conductivity of this material. As expected, this 3D net‐like FeO_x /C composite delivers an excellent charge capacity of 851.3 mAh g⁻¹ after 50 cycles at 0.2 A g⁻¹ as well as high stability and rate performance of 714.7 mAh g⁻¹ after 300 cycles at 1 A g⁻¹. Superior performance, harmlessness, low costs, and high yield may greatly stimulate the practical application of the products as anode materials in lithium‐ion batteries.     

Building Hierarchical Microcubes Composed of One-Dimensional CoSe2@Nitrogen-Doped Carbon for Superior Sodium Ion Batteries

Designing and synthesizing highly stable anode materials with high capacity is critical for the practical application of sodium ion batteries (SIBs), however, to date, this remains an insurmountable barrier. The introduction of hierarchical architectures and carbon supports is proving an effective strategy for addressing these challenges. Thus, we have fabricated a hierarchical CoSe₂@nitrogen-doped carbon (CoSe₂@NC) microcube composite using the Prussian blue analogue Co₃[Co(CN)₆]₂ as template. The rational combination of the unique hierarchical construction from one to three dimensions and a nitrogen-doped carbon skeleton facilitates sodium ion and electron transport as well as stabilizing the host structure during repeated discharge/charge processes, which contributes to its excellent sodium storage capability. As expected, the as-prepared CoSe₂@NC composite delivered remarkable reversible capacity and ultralong cycling lifespan even at a high rate of 2.0 A g⁻¹ (384.3 mA h g⁻¹ after1800 loops) when serving as the anode material for SIBs. This work shows the great potential of the CoSe₂-based anode for practical application in SIBs, and the original strategy may be extended to other anode materials.     

Controlled synthesis of core-shell Fe2O3@N-C with ultralong cycle life for lithium-ion batteries

Development of low-cost electrode materials with long cycle life and high volumetric capacity is important for large-scale applications of lithium-ion batteries （LIBs）.Here,an electrode made from Fe₂O₃encapsulated with N-doped carbon （Fe₂O₃@N-C） via ZIF-8 coating and carbonization process is reported.A cavity was generated between the Fe₂O₃and N-C material during the carbonization process that is conducive to alleviating the volum...     

Synthesis of carbon nanofibers@MnO2 3D structures over copper foil as binder free anodes for lithium ion batteries

A 3D structured composite of carbon nanofibers@MnO₂ on copper foil is reported here as a binder free anode of lithium ion batteries, with high capacity, fast charge/discharge rate and good stability. Carbon nanofiber yarns were synthesized directly over copper foil through a floating catalyst method. The growth of carbon nanofiber yarns was significantly enhanced by mechanical polishing of the copper foils, which can be attributed to the increased surface roughness and surface area of the copper foils. MnO₂ was then grown over carbon nanofibers through spontaneous reduction of potassium permanganate by the carbon nanofibers. The obtained composites of carbon nanofibers@MnO₂ over copper foil were tested as an anode in lithium ion batteries and they show superior electrochemical performance. The initial reversible capacity of carbon nanofibers@MnO₂ reaches up to around 998 mAh·g^?1 at a rate of 60 mmA·g^?1 based on the mass of carbon nanofibers and MnO₂. The carbon nanofibers@MnO₂ electrodes could deliver a capacity of 630 mAh·g^?1 at the beginning and maintain a capacity of 440 mmAh·g^?1 after 105 cycles at a rate of 600 mA·g^?1. The high initial capacity can be attributed to the presence of porous carbon nanofiber yarns which have good electrical conductivity and the MnO₂ thin film which makes the entire materials electrochemically active. The high cyclic stability of carbon nanofibers@MnO₂ can be ascribed to the MnO₂ thin film which can accommodate the volume expansion and shrinking during charge and discharge and the good contact of carbon nanofibers with MnO₂ and copper foil.     

Co3O4 Hollow Nanoparticles Embedded in Mesoporous Walls of Carbon Nanoboxes for Efficient Lithium Storage

Confining nanostructured electrode materials in porous carbon represents an effective strategy for improving the electrochemical performance of lithium-ion batteries. Herein, we report the design and synthesis of hybrid hollow nanostructures composed of highly dispersed Co₃O₄ hollow nanoparticles (sub-20 nm) embedded in the mesoporous walls of carbon nanoboxes (denoted as H-Co₃O₄@MCNBs) as an anode material for lithium-ion batteries. The facile metal–organic framework (MOF)-engaged strategy for the synthesis of H-Co₃O₄@MCNBs involves chemical etching-coordination and subsequent two-step annealing treatments. Owing to the unique structural merits including more active interfacial sites, effectively alleviated volume variation, good and stable electrical contact, and easy access of Li⁺ ions, the H-Co₃O₄@MCNBs exhibit excellent lithium-storage performance in terms of high specific capacity, excellent rate capability, and cycling stability.     

Supercritical Carbon Dioxide Assisted Deposition of Fe3O4 Nanoparticles on Hierarchical Porous Carbon and Their Lithium‐Storage Performance

A composite of highly dispersed Fe₃O₄ nanoparticles (NPs) anchored in three‐dimensional hierarchical porous carbon networks (Fe₃O₄/3DHPC) as an anode material for lithium‐ion batteries (LIBs) was prepared by means of a deposition technique assisted by a supercritical carbon dioxide (scCO₂)‐expanded ethanol solution. The as‐synthesized Fe₃O₄/3DHPC composite exhibits a bimodal porous 3D architecture with mutually connected 3.7 nm mesopores defined in the macroporous wall on which a layer of small and uniform Fe₃O₄ NPs was closely coated. As an anode material for LIBs, the Fe₃O₄/3DHPC composite with 79 wt % Fe₃O₄ (Fe₃O₄/3DHPC‐79) delivered a high reversible capacity of 1462 mA h g^?1 after 100 cycles at a current density of 100 mA g^?1, and maintained good high‐rate performance (728, 507, and 239 mA h g^?1 at 1, 2, and 5 C, respectively). Moreover, it showed excellent long‐term cycling performance at high current densities, 1 and 2 A g^?1. The enhanced lithium‐storage behavior can be attributed to the synergistic effect of the porous support and the homogeneous Fe₃O₄ NPs. More importantly, this straightforward, highly efficient, and green synthetic route will definitely enrich the methodologies for the fabrication of carbon‐based transition‐metal oxide composites, and provide great potential materials for additional applications in supercapacitors, sensors, and catalyses.     

A Simple Prelithiation Strategy To Build a High‐Rate and Long‐Life Lithium‐Ion Battery with Improved Low‐Temperature Performance

Lithium‐ion batteries (LIBs) are being used to power the commercial electric vehicles (EVs). However, the charge/discharge rate and life of current LIBs still cannot satisfy the further development of EVs. Furthermore, the poor low‐temperature performance of LIBs limits their application in cold climates and high altitude areas. Herein, a simple prelithiation method is developed to fabricate a new LIB. In this strategy, a Li₃V₂(PO₄)₃ cathode and a pristine hard carbon anode are used to form a primary cell, and the initial Li⁺ extraction from Li₃V₂(PO₄)₃ is used to prelithiate the hard carbon. Then, the self‐formed Li₂V₂(PO₄)₃ cathode and prelithiated hard carbon anode are used to form a 4 V LIB. The LIB exhibits a maximum energy density of 208.3 Wh kg⁻¹, a maximum power density of 8291 W kg⁻¹ and a long life of 2000 cycles. When operated at −40 °C, the LIB can keep 67 % capacity of room temperature, which is much better than conventional LIBs.     

Polyoxometalates-Based Metal–Organic Frameworks Made by Electrodeposition and Carbonization Methods as Cathodes and Anodes for Asymmetric Supercapacitors

Hybrid materials have obtained well-deserved attention for energy storage devices, because they show high capacitances and high energy densities induced by the synergistic effect between complementary components. Polyoxometalate-based metal–organic frameworks (POMOFs) possess the abundant redox-active sites and ordered structures of polyoxometalates (POMs) and metal–organic frameworks (MOFs), respectively. Here, an asymmetric supercapacitor (ASC) NENU-5/PPy/60//FeMo/C was fabricated in which both its electrodes are prepared from POMOF precursors. A typical POMOF material, NENU-5, was first connected with polypyrrole (PPy) through electrodeposition to form the cathode material NENU-5/PPy. Another representative POMOFs material, PMo₁₂@MIL-100, was carbonized to obtain the anode material FeMo/C. Cathode NENU-5/PPy exhibited an extraordinary capacitance of 508.62 F g⁻¹ (areal capacitance: 2034.51 mF cm⁻²). In addition, anode FeMo/C shows excellent cyclic stability attributed to its unique structure. Finally, benefiting from the outstanding capacitances and structural merits of the anode and cathode, assembled asymmetric supercapacitor NENU-5/PPy/60//FeMo/C achieves an energy density of 1.12 mWh cm⁻³ at a power density output of 27.78 mW cm⁻³, as well as a notable life of 10 000 cycles with an capacity retention of 80.62 %. Thus, the unique ASC is strongly competitive in high capacitance, long cycle life, and high energy-required energy storage devices.     

Heightened Integration of POM‐based Metal–Organic Frameworks with Functionalized Single‐Walled Carbon Nanotubes for Superior Energy Storage

To increase the conductivity of polyoxometalate‐based metal–organic frameworks (POMOFs) and promote their applications in the field of energy storage, herein, a simple approach was employed to improve their overall electrochemical performances by introducing a functionalized single‐walled carbon nanotubes (SWNT‐COOH). A new POMOF compound, [Cu₁₈(trz)₁₂Cl₃(H₂O)₂][PW₁₂O₄₀] (CuPW), was successfully synthesized, then the size‐matched functionalized SWNT–COOH was introduced to fabricate CuPW/SWNT–COOH composite (PMNT–COOH) by employing a simple sonication‐driven periodic functionalization strategy. When the PMNT–COOH nanocomposite was used as the anode material for Lithium‐ion batteries (LIBs), PMNT–COOH( 3 ) (CuPWNC:SWNT‐COOH=3:1) showed superior behavior of energy storage, a high reversible capacity of 885 mA h g^?1 up to a cycle life of 170 cycles. The electrochemical results indicate that the uniform packing of SWNT–COOH provided a favored contact between the electrolyte and the electrode, resulting in enhanced specific capacity during lithium insertion/extraction process. This fabrication of PMNT–COOH nanocomposite opens new avenues for the design and synthesis of new generation electrode materials for LIBs.     

Lithium Germanate (Li2GeO3): A High‐Performance Anode Material for Lithium‐Ion Batteries

A simple, cost‐effective, and easily scalable molten salt method for the preparation of Li₂GeO₃ as a new type of high‐performance anode for lithium‐ion batteries is reported. The Li₂GeO₃ exhibits a unique porous architecture consisting of micrometer‐sized clusters (secondary particles) composed of numerous nanoparticles (primary particles) and can be used directly without further carbon coating which is a common exercise for most electrode materials. The new anode displays superior cycling stability with a retained charge capacity of 725 mAh g^?1 after 300 cycles at 50 mA g^?1. The electrode also offers excellent rate capability with a capacity recovery of 810 mAh g^?1 (94 % retention) after 35 cycles of ascending steps of current in the range of 25–800 mA g^?1 and finally back to 25 mA g^?1. This work emphasizes the importance of exploring new electrode materials without carbon coating as carbon‐coated materials demonstrate several drawbacks in full devices. Therefore, this study provides a method and a new type of anode with high reversibility and long cycle stability.     

High capacity silicon/carbon composite anode materials for lithium ion batteries

Silicon/carbon composite materials are prepared by pyrolysis of pitch embedded with graphite and silicon powders. As anode for lithium ion batteries, its initial reversible capacity is 800–900 mAh/g at 0.25 mA/cm² in a voltage range of 0.02/1.5 V vs. Li. The material modification by adding a small amount of CaCO₃ into precursor improves the initial reversibility (η₁=84%) and suppresses the capacity fade upon cycling. A little higher insertion voltage of the composites than commercial CMS anode material improves the cell safety in the high rate charging process.     

Synthesis and Electrochemical Performance of Electrostatic Self-Assembled Nano-Silicon@N-Doped Reduced Graphene Oxide/Carbon Nanofibers Composite as Anode Material for Lithium-Ion Batteries

Silicon-carbon nanocomposite materials are widely adopted in the anode of lithium-ion batteries (LIB). However, the lithium ion (Li⁺) transportation is hampered due to the significant accumulation of silicon nanoparticles (Si) and the change in their volume, which leads to decreased battery performance. In an attempt to optimize the electrode structure, we report on a self-assembly synthesis of silicon nanoparticles@nitrogen-doped reduced graphene oxide/carbon nanofiber (Si@N-doped rGO/CNF) composites as potential high-performance anodes for LIB through electrostatic attraction. A large number of vacancies or defects on the graphite plane are generated by N atoms, thus providing transmission channels for Li⁺ and improving the conductivity of the electrode. CNF can maintain the stability of the electrode structure and prevent Si from falling off the electrode. The three-dimensional composite structure of Si, N-doped rGO, and CNF can effectively buffer the volume changes of Si, form a stable solid electrolyte interface (SEI), and shorten the transmission distance of Li⁺ and the electrons, while also providing high conductivity and mechanical stability to the electrode. The Si@N-doped rGO/CNF electrode outperforms the Si@N-doped rGO and Si/rGO/CNF electrodes in cycle performance and rate capability, with a reversible specific capacity reaching 1276.8 mAh/g after 100 cycles and a Coulomb efficiency of 99%.     

Porous Si-Cu3Si-Cu Microsphere@C Core–Shell Composites with Enhanced Electrochemical Lithium Storage

Low-cost Si-based anode materials with excellent electrochemical lithium storage present attractive prospects for lithium-ion batteries (LIBs). Herein, porous Si-Cu₃Si-Cu microsphere@C composites are designed and prepared by means of an etching/electroless deposition and subsequent carbon coating. The composites show a core–shell structure, with a porous Si/Cu microsphere core surrounded by the N-doped carbon shell. The Cu and Cu₃Si nanoparticles are embedded inside porous silicon microspheres, forming the porous Si/Cu microsphere core. The microstructure and lithium storage performance of porous Si-Cu₃Si-Cu microsphere@C composites can be effectively tuned by changing electroless deposition time. The Si-Cu₃Si-Cu microsphere@C composite prepared with 12 min electroless deposition delivers a reversible capacity of 627 mAh g⁻¹ after 200 cycles at 2 A g⁻¹, showing an enhanced lithium storage ability. The superior lithium storage performance of the Si-Cu₃Si-Cu microsphere@C composite can be ascribed to the improved electronic conductivity, enhanced mechanical stability, and better buffering against the large volume change in the repeated lithiation/delithiation processes.     

Porous Si coated with S-doped carbon as anode material for lithium ion batteries

A novel porous Si/S-doped carbon composite was prepared by a magnesiothermic reaction of mesoporous SiO₂, subsequently coating with a sulfur-containing polymer-poly(3,4-ethylene dioxythiophene), and a post-carbonization process. The as-prepared Si composite was homogeneously coated with disordered S-doped carbon with 2.6 wt.%?S in the composite and retained a high surface area of 58.8 m²?g^?1. The Si/S-doped carbon composite exhibited superior electrochemical performance and long cycle life as an anode material in lithium ion cells, showing a stable reversible capacity of 450 mAh g^?1 even at a high current rate of 6,000 mA?g^?1.