Hierarchical three-dimensional Fe3O4@porous carbon matrix/graphene anodes for high performance lithium ion batteries

MOF-Derived Long Spindle-like Carbon-Coated Ternary Transition-Metal-Oxide Composite for Lithium Storage

Fe₃O₄ is a promising alternative for next-generation lithium-ion batteries (LIBs). However, its poor cycle stability due to the large volume effect during cycling and poor conductivity hinders its application. Herein, we have successfully designed and prepared a carbon-coated ternary transition-metal-oxide composite (noted as (FeCoNi)₃O₄@C), which is derived from FeCoNi-MOF-74 (denoted as FeCoNi-211-24). (FeCoNi)₃O₄@C perfectly inherited the long spindle-shaped precursor structure, and (FeCoNi)₃O₄ particles grew in situ on the precursor surface. The ordered particles and the carbon-coated structure inhibited the agglomeration of particles, improving the material's cycle stability and conductivity. Therefore, the electrode exhibited excellent electrochemical performance. Specifically, (FeCoNi)₃O₄@C-700 presented excellent initial discharge capacity (763.1 mAh g^-1 at 0.2 A g^-1), high initial coulombic efficiency (73.8%), excellent rate capability, and cycle stability (634.6 mAh g^-1 at 0.5 A g^-1 after 505 cycles). This study provides a novel idea for developing anode materials for LIBs.

Facile synthesis of a rod-like porous carbon framework confined magnetite nanoparticle composite for superior lithium-ion storage

This work demonstrates a streamlined method to engineer a rod-like porous carbon framework (RPC) confined magnetite nanoparticles composite (Fe₃O₄/RPC) starting from metallic iron and gallic acid (GA) solution. First, a mild redox reaction was triggered between Fe and GA to prepare a rod-shaped metal-organic framework (MOF) ferric gallate sample (Fe-GA). Then, the Fe-GA sample was calcinated to obtain a prototypic RPC supported metal iron nanoparticle intermediate sample (Fe/RPC). Finally, the Fe₃O₄/RPC composite was synthesized after a simple hydrothermal reaction. The Fe₃O₄/RPC composite exhibited competitive electrochemical behaviors, which has a high gravimetric capacity of 1140 mAh·g^-1 at a high charge and discharge current of 1000 mA·g^-1 after 300 cycles. The engineered RPC supportive matrix not only offers adequate voids to buffer the volume expansion from inside well-dispersed Fe₃O₄ nanoparticles, but also facilitates both the ionic and electronic transport during the electrochemical reactions. The overall material synthesis involves of no hazardous or expensive chemicals, which can be regarded to be a scalable and green approach. The obtained samples have a good potential to be further developed for wider applications.

Microalgae-Templated Spray Drying for Hierarchical and Porous Fe3O4/C Composite Microspheres as Li-ion Battery Anode Materials

A method of microalgae-templated spray drying to develop hierarchical porous Fe₃O₄/C composite microspheres as anode materials for Li-ion batteries was developed. During the spray-drying process, individual microalgae serve as building blocks of raspberry-like hollow microspheres via self-assembly. In the present study, microalgae-derived carbon matrices, naturally doped heteroatoms, and hierarchical porous structural features synergistically contributed to the high electrochemical performance of the Fe₃O₄/C composite microspheres, enabling a discharge capacity of 1375 mA·h·g^-1 after 700 cycles at a current density of 1 A/g. Notably, the microalgal frameworks of the Fe₃O₄/C composite microspheres were maintained over the course of charge/discharge cycling, thus demonstrating the structural stability of the composite microspheres against pulverization. In contrast, the sample fabricated without microalgal templating showed significant capacity drops (up to ~40% of initial capacity) during the early cycles. Clearly, templating of microalgae endows anode materials with superior cycling stability.

Fe3O4@Carbon Nanofibers Synthesized from Cellulose Acetate and Application in Lithium-Ion Battery

Fe₃O₄@CNF anode material for Li-ion batteries (LIBs) was designed and fabricated using lyotropic cellulose acetate as the carbon nanofiber (CNF) phase and Fe(acac)₃ as the Fe₃O₄ phase through the electrospinning approach. Because the CNFs could retard the change of Fe₃O₄ volume during the electrochemical cycling and improve the electrical conductivity and the introduction of Fe₃O₄ could offer a larger specific surface area and more mesopores to promote electrolyte penetration and Li⁺ diffusion, the Fe₃O₄@CNFs electrode showed high reversible capacities (RCs) of 773.6 and 596.5 mAh g^-1 after 300 cycles and capacity residuals of 98.0 and 99.0% at high current densities 1 and 2 A g^-1, respectively. This simple method to fabricate Fe₃O₄@CNFs composite as anode material can be widely applied to fabricate metal oxides and bio-carbon composite nanofibers for high-performance energy storage materials.

Metal-organic framework derived amorphous VOx coated Fe3O4/C hierarchical nanospindle as anode material for superior lithium-ion batteries

Lithium-ion batteries (LIBs) are widely regarded as a promising electrochemical energy storage device, due to their high energy density and good cycling stability. To date, the development of anode materials for LIBs is still confronted with many serious problems, and much effort is required for constructing more ideal anode materials. Herein, starting with metal-organic frameworks (MOFs), an amorphous VO_x coated Fe₃O₄/C hierarchical nanospindle has been successfully synthesized. The obtained Fe₃O₄/C@VO_x nanospindle has a uniform particle size of ∼100 nm in diameter and ∼400 nm in length and consists of ultrafine Fe₃O₄ nanoparticles (∼5 nm) embedded in a porous carbon matrix as the core and an amorphous VO_x layer as the shell. Notably, as the anode material for LIBs, Fe₃O₄/C@VO_x delivers a high coulombic efficiency (74.2%) and a large capacity of 845 mA h g^-1 after 500 cycles at 1000 mA g^-1. A prominent discharge reversible capacity of 340 mA h g^-1 is also still retained at 5000 mA g^-1. More importantly, the presented facile MOF-derived route could be easily extended to other functional materials for widespread applications.

Rational Construction of 2D Fe3 O4 @Carbon Core-Shell Nanosheets as Advanced Anode Materials for High-Performance Lithium-Ion Half/Full Cells

Transition metal oxides have vastly limited practical application as electrode materials for lithium-ion batteries (LIBs) due to their rapid capacity decay. Here, a versatile strategy to mitigate the volume expansion and low conductivity of Fe₃ O₄ by coating a thin carbon layer on the surface of Fe₃ O₄ nanosheets (NSs) was employed. Owing to the 2D core-shell structure, the Fe₃ O₄ @C NSs exhibit significantly improved rate performance and cycle capability compared with bare Fe₃ O₄ NSs. After 200 cycles, the discharge capacity at 0.5 A g^-1 was 963 mA h g^-1 (93 % retained). Moreover, the reaction mechanism of lithium storage was studied in detail by ex situ XRD and HRTEM. When coupled with a commercial LiFePO₄ cathode, the resulting full cell retains a capacity of 133 mA h g^-1 after 100 cycles at 0.1 A g^-1 , which demonstrates its superior energy storage performance. This work provides guidance for constructing 2D metal oxide/carbon composites with high performance and low cost for the field of energy storage.

Facile Synthesis of Flower-Like MnCo2 O4 @PANi-rGO: A High-Performance Anode Material for Lithium-Ion Batteries

Flower-like MnCo₂ O₄ was prepared in a self-assembly process and used in the formation of MnCo₂ O₄ @polyaniline (MnCo₂ O₄ @PANi) that proceeds by a simple in situ polymerization. The MnCo₂ O₄ @PANi-reduced graphite oxide (MnCo₂ O₄ @PANi-rGO) composite was then synthesized by introducing rGO into MnCo₂ O₄ @PANi. This modification improves the overall electronic conductivity of the MnCo₂ O₄ @PANi-rGO because of the dual conductive functions of rGO and PANi; it also provides a buffer for the changes in electrode volume during cycling, thus improving the lithium-storage performance of MnCo₂ O₄ @PANi-rGO. The electrochemical performance of the samples was evaluated by charge/discharge cycling testing, cyclic voltammetry, and electrochemical impedance spectroscopy. MnCo₂ O₄ @PANi-rGO delivers a discharge capacity of 745 mAh g^-1 and a Coulombic efficiency of 100 % after 1050 cycles at a current density of 500 mA g^-1 , and is a promising anode material for lithium-ion batteries.

Recent Advance in Co3O4 and Co3O4-Containing Electrode Materials for High-Performance Supercapacitors

Among the popular electrochemical energy storage devices, supercapacitors (SCs) have attracted much attention due to their long cycle life, fast charge and discharge, safety, and reliability. Transition metal oxides are one of the most widely used electrode materials in SCs because of the high specific capacitance. Among various transition metal oxides, Co3O4 and related composites are widely reported in SCs electrodes. In this review, we introduce the synthetic methods of Co3O4, including the hydrothermal/solvothermal method, sol-gel method, thermal decomposition, chemical precipitation, electrodeposition, chemical bath deposition, and the template method. The recent progress of Co3O4-containing electrode materials is summarized in detail, involving Co3O4/carbon, Co3O4/conducting polymer, and Co3O4/metal compound composites. Finally, the current challenges and outlook of Co3O4 and Co3O4-containing composites are put forward.

Chemical bowling-assisted synthesis of Fe3O4@starch-derived carbon composites as anode materials with superior cycling stability for lithium-ion batteries

Fe₃O₄@starch-derived carbon composites (Fe₃O₄@C-SD composites) were produced via chemical bowling, an economic and a scalable method, and a subsequent calcination with starch as the carbon resource and iron(iii) nitrate as the iron resource.

Rational design of multi-walled carbon nanotube@hollow Fe3O4@C coaxial nanotubes as long-cycle-life lithium ion battery anodes

In this work, we report a high-performance anode material created by rationally encapsulating multi-walled carbon nanotubes (MWNTs) within hollow Fe₃O₄ nanotubes followed by applying a carbon coating. When tested for lithium storage, as-prepared MWNT@hollow Fe₃O₄@C coaxial nanotubes present high specific capacity, superior rate performance, and outstanding cycling stability. It is capable of delivering high capacities of 758 mA h g^-1 at 500th cycle at 0.2 A g^-1, and 409 mA h g^-1 after 1000 cycles at a high rate of 1.5 A g^-1. This excellent performance can be attributed to its unique architecture, which provides high electrical conductivity, offers enough void space for volume accommodation, and mitigates the pulverization of Fe₃O₄ during cycles.

Design of highly porous Fe3O4@reduced graphene oxide via a facile PMAA-induced assembly

Advances in the synthesis and processing of graphene-based materials have presented the opportunity to design novel lithium-ion battery (LIB) anode materials that can meet the power requirements of next-generation power devices. In this work, a poly(methacrylic acid) (PMAA)-induced self-assembly process was used to design super-mesoporous Fe3O4 and reduced-graphene-oxide (Fe3O4@RGO) anode materials. We demonstrate the relationship between the media pH and Fe3O4@RGO nanostructure, in terms of dispersion state of PMAA-stabilized Fe3O4@GO sheets at different surrounding pH values, and porosity of the resulted Fe3O4@RGO anode. The anode shows a high surface area of 338.8 m2 g-1 with a large amount of 10-40 nm mesopores, which facilitates the kinetics of Li-ions and electrons, and improves electrode durability. As a result, Fe3O4@RGO delivers high specific-charge capacities of 740 mA h g-1 to 200 mA h g-1 at various current densities of 0.5 A g-1 to 10 A g-1, and an excellent capacity-retention capability even after long-term charge-discharge cycles. The PMAA-induced assembly method addresses the issue of poor dispersion of Fe3O4-coated graphene materials-which is a major impediment in the synthesis process-and provides a facile synthetic pathway for depositing Fe3O4 and other metal oxide nanoparticles on highly porous RGO.

Encapsulation of Fe3O4 between Copper Nanorod and Thin TiO2 Film by ALD for Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are considered to be promising power sources due to their combination of high-rate capacitors and high-capacity batteries. However, development of a high-performance LIC is still restricted by the sluggish intercalation reaction and unsatisfied specific capacities in battery-type bulk anodes. To overcome these issues, herein, we utilize two-step atomic layer deposition (ALD) to realize a uniform coating of FeO _x and TiO₂ on CuO nanorods, which results in the formation of ternary CuO@FeO _x@TiO₂ composite. After further treatment in H₂/Ar atmosphere, the as-derived Fe₃O₄ is encapsulated between conductive Cu nanorod and hollow TiO₂ shell (denoted as Cu@Fe₃O₄@TiO₂). Owing to the rational design, the binder-free Cu@Fe₃O₄@TiO₂ electrode exhibits an ultrahigh Li-ion storage capacity (1585 mA h g^-1 at 0.2 A g^-1), superior rate capability, and excellent cycle performance (no decay after 1000 cycles), which could efficiently boost the energy-storage capability of LICs. By employing an anode of Cu@Fe₃O₄@TiO₂ and a cathode of activated carbon, the as-constructed full LIC device provides high energy//powder densities (154.8 Wh kg^-1 at 200 W kg^-1; 66.2 Wh kg^-1 at 30 kW kg^-1). These superior results demonstrate that ALD-enabled architectures hold great promise for synthesizing high-capacity anodes for LICs.

Cr2O3 nanosheet/carbon cloth anode with strong interaction and fast charge transfer for pseudocapacitive energy storage in lithium-ion batteries

Flexible lithium-ion batteries have attracted considerable interest for next-generation bendable, implantable and wearable electronics devices. Here, we have successfully grown Cr₂O₃ nanosheets on carbon cloth (CC) as freestanding anodes for Li-ion batteries (LIBs). Density functional theory (DFT) calculations verify an optimal structure of two-dimensional Cr₂O₃ nanosheets on the carbon fiber surface and a strong interaction between the O edges of Cr₂O₃ and the carbon. The interconnected Cr₂O₃ nanosheets with a large surface area enable fast charge transfer by efficient contact with electrolyte while the flexible CC substrate accommodates the volume change during cycles, leading to excellent rate capability and cyclic stability through psuedocapacitance-dominant energy storage. Full cells are assembled using the Cr₂O₃-CC anode and a LiFePO₄ cathode, which deliver excellent capacity retention and rate capability. The fully-charged cell is demonstrated to power a red light-emitting diode (LED), verifying the potential of Cr₂O₃-CC as a promising anode material for LIBs.

2D Cr₂O₃ nanosheets are grown on CC with strong interaction and fast charge transfer, and exhibit excellent cyclic performance for LIBs.