Rational design and synthesis of sandwich-like reduced graphene oxide/Fe2O3/N-doped carbon nanosheets as high-performance anode materials for lithium-ion batteries

Lithium Storage Behavior of Expanded Microcrystalline Graphite/Fe2O3 Anode for Lithium-Ion Batteries

Driven by the pressing need for improved performance of lithium-ion batteries in electric vehicles and portable electronics, this research aims to develop novel high-performance anode materials. Innovatively, expanded microcrystalline graphite (EMG) is used as the matrix material. Through a simple synthesis strategy, Fe2O3 nanoparticles are successfully introduced to prepare expanded microcrystalline EMG/Fe2O3 composites. The study systematically investigates the effects of different doping ratios on the electrochemical performance of the materials. The experimental results demonstrate that the EMG/Fe2O3-2 composite material exhibits the most excellent lithium storage performance: the initial discharge specific capacity is 1114.10 mAh·g-1, and after 100 cycles, the discharge specific capacity remains at 1007.05 mAh·g-1, with a capacity retention rate as high as 90.39%. The outstanding electrochemical performance is mainly attributed to the following factors. On the one hand, the porous structure of EMG not only provides an effective buffering space for the volume expansion of Fe2O3, but its complex conductive network also significantly enhances the charge transport efficiency of the composite material. On the other hand, the high theoretical specific capacity of Fe2O3 nanoparticles, combined with the EMG matrix, forms a synergistic effect that enhances the specific capacity of the composite material. This thesis not only elucidates the synergistic mechanism between EMG and Fe2O3 but also provides new strategies and perspectives for the performance breakthrough of lithium-ion battery anode materials.

Decorating Phosphorus Anode with SnO2 Nanoparticles To Enhance Polyphosphides Chemisorption for High-Performance Lithium-Ion Batteries

Phosphorus has been regarded as one of the most promising next-generation lithium-ion battery anode materials, because of its high theoretical specific capacity and safe working potential. However, the shuttle effect and sluggish conversion kinetics hamper its practical application. To overcome these limitations, we decorated SnO₂ nanoparticles at the surface of phosphorus using an electrostatic self-assembly method, in which SnO₂ can participate in the discharge/charge reaction, and the Li₂O formed can chemically adsorb and suppress the shuttle of soluble polyphosphides across the separator. Additionally, the Sn/Li-Sn alloy can enhance the electrical conductivity of the overall electrode. Meanwhile, the similar volume changes and simultaneous lithiation/delithiation process in phosphorus and SnO₂/Sn are beneficial for avoiding additional particle damage near two-phase boundaries. Consequently, this hybrid anode exhibits a high reversible capacity of ∼1180.4 mAh g^-1 after 120 cycles and superior high-rate performance with ∼78.5% capacity retention from 100 to 1000 mA g^-1.

Fe2O3nanoparticles anchored on thermally oxidized MWCNTs as anode material for lithium-ion battery

Thermally oxidized MWCNTs (OMWCNTs) are fabricated by a thermal treatment of MWCNTs at 500 °C for 3 h in an oxygen-containing atmosphere. The oxygen content of OMWCNTs increases from 1.9 wt% for MWCNTs to 8.3 wt%. And the BET specific surface area of OMWCNTs enhances from 254.2 m²g^-1for MWCNTs to 496.1 m²g^-1. The Fe₂O₃/OMWCNTs nanocomposite is prepared by a hydrothermal method. Electrochemical measurements show that Fe₂O₃/OMWCNTs still keeps a highly reversible specific capacity of 653.6 mA h g^-1after 200 cycles at 0.5 A g^-1, which shows an obviously higher capacity than the sum of that of single Fe₂O₃and OMWCNTs. The OMWCNTs not only buffer the volume changes of Fe₂O₃nanoparticles but also provide high-speed electronic transmission channels in the charge-discharge process. The thermal oxidation method of OMWCNTs avoids using strong corrosive acids such as nitric acid and sulfuric acid, which has the advantages of safety, environmental protection, macroscopic preparation, etc.

Rationally engineering a hierarchical porous carbon and reduced graphene oxide supported magnetite composite with boosted lithium-ion storage performances

Ferric gallate (Fe-GA), an ancient metal-organic framework (MOF) material, has been recently employed as an eco-friendly and cost-effective precursor sample to synthesize a porous carbon confined nano-iron composite (Fe/RPC), and the Fe element in the Fe/RPC sample could be further oxidized to Fe₃O₄ nanocrystals in a 180 °C hydrothermal condition. On this foundation, this work reports an optimized approach to engineering a hierarchical one-dimensional porous carbon and two-dimensional reduced graphene oxide (RGO) supporting framework with Fe₃O₄ nanoparticles well dispersed. Under mild hydrothermal condition, the redox reaction between metal iron atoms from Fe/RPC and surface functional radicals from few-layered graphene oxide sheets (GO) is triggered. As a result, reinforced microstructure and improved atomic efficiency have been achieved for the Fe₃O₄@RPC/RGO sample. The homogeneously dispersed Fe₃O₄ nanoparticles with controlled size are anchored on the surface of the larger sized RGO coating layers while the smaller sized RPC domains are embedded between the RGO sheets as spacer. Challenges including spontaneous aggregation of RPC, over exposure of Fe₃O₄ nanoparticles and excessive restacking of RGO have been significantly inhibited. Furthermore, micro-sized carbon fiber (CF) is chosen as a structural reinforcement additive during electrode fabrication, and the Fe₃O₄@RPC/RGO sample delivers a good specific capacity of 1170.5 mAh·g^-1 under a current rate of 1000 mA·g^-1 for 500 cycles in the half cell form. The reasons for superior electrochemical behaviors have been revealed and the lithium-ion storage performances of the Fe₃O₄@RPC/RGO sample in the full cell form have been preliminarily investigated.

Sodium carboxymethylcellulose induced engineering a porous carbon and graphene immobilized magnetite composite for lithium-ion storage

Immobilizing nanosized electrochemically active materials with supportive carbonaceous framework usually brings in improved lithium-ion storage performance. In this work, magnetite nanoparticles (Fe₃O₄) are stabilized by both porous carbon domains (PC) and reduced graphene oxide sheets (RGO) to form a hierarchical composite (Fe₃O₄@PC/RGO) via a straightforward approach. The PC confined iron nanoparticle intermediate sample (Fe@PC) was first fabricated, where sodium carboxymethylcellulose (Na-CMC) was employed not only as a cross-linker to trap ferric ions for synthesizing a Fe-CMC precursor sample, but also as the carbon source for PC domains and iron source for Fe nanoparticles in a pyrolysis process. The final redox reaction between Fe@PC and few-layered graphene oxide (GO) sheets contributed to the formation of Fe₃O₄ nanoparticles with reduced size, avoiding any severe aggregation or excessive exposure. The Fe₃O₄@PC/RGO sample delivered a specific capacity of 522.2 mAh·g^-1 under a current rate of 1000 mA·g^-1 for 650 cycles. The engineered Fe@PC and Fe₃O₄@PC/RGO samples have good prospects for application in wider fields.

Synthesis of Si/Fe2O3-Anchored rGO Frameworks as High-Performance Anodes for Li-Ion Batteries

By virtue of the high theoretical capacity of Si, Si-related materials have been developed as promising anode candidates for high-energy-density batteries. During repeated charge/discharge cycling, however, severe volumetric variation induces the pulverization and peeling of active components, causing rapid capacity decay and even development stagnation in high-capacity batteries. In this study, the Si/Fe2O3-anchored rGO framework was prepared by introducing ball milling into a melt spinning and dealloying process. As the Li-ion battery (LIB) anode, it presents a high reversible capacity of 1744.5 mAh g-1 at 200 mA g-1 after 200 cycles and 889.4 mAh g-1 at 5 A g-1 after 500 cycles. The outstanding electrochemical performance is due to the three-dimensional cross-linked porous framework with a high specific surface area, which is helpful to the transmission of ions and electrons. Moreover, with the cooperation of rGO, the volume expansion of Si is effectively alleviated, thus improving cycling stability. The work provides insights for the design and preparation of Si-based materials for high-performance LIB applications.

Heterogeneous iron oxide nanoparticles anchored on carbon nanotubes for high-performance lithium-ion storage and fenton-like oxidation

In this work, heterogeneous hematite (Fe₂O₃) and magnetite (Fe₃O₄) nanoparticles are jointly engineered on the external surface of multi-walled carbon nanotubes (CNTs) to construct a composite material (Fe₂O₃@Fe₃O₄/CNT). A simple one-step redox reaction is triggered in a hydrothermal reaction system containing functionalized CNT (FCNT) aqueous suspension and iron foils. Both Fe₂O₃ and Fe₃O₄ nanoparticles with controlled size are generated and well dispersed in the interconnected CNT framework. Controlled samples of Fe₂O₃@Fe₃O₄ and Fe₃O₄/CNT have also been prepared and used to investigate the synthetic mechanism and evaluate the lithium-ion storage performances. As an anodic active material for lithium-ion batteries, the Fe₂O₃@Fe₃O₄/CNT composite delivered a high reversible capacity of about 924 mAh·g^-1 for 200 continual charge/discharge cycles under a high current rate of 1000 mA·g^-1. As a catalyst in a Fenton-like reaction for degrading methyl orange (MO) contaminant in waterbody, the Fe₂O₃@Fe₃O₄/CNT composite exhibited an attractive decomposition efficiency (99.5% decomposition within 60 min) and good stability. The beneficial factors contributing to the inspiring performances are discussed. The effective and scalable material design and synthesis method can be regarded to have good potential in other fields.

Helical carbon nanofibers modified with Fe2O3 as a high performance anode material for lithium-ion batteries

Helical carbon nanofibers (HCNFs) modified with Fe2O3 (Fe2O3/HCNFs) with a particle size of about 10-20 nm were first introduced for potential use as a novel anode material for lithium-ion batteries (LIBs). Fe2O3/HCNFs were successfully prepared via a chemical liquid deposition (CLPD) method in this study. HCNFs with a special three-dimensional helical structure improve the conductivity and also provide a strong supporting network space for stress and strain during the volume expansion of Fe2O3 nanoparticles. The Fe2O3/HCNF anode still retains its capacity of 816.3 mA h g-1 after 100 cycles at the current density of 200 mA g-1, which is significantly better than those of contrast samples (only 144.2 mA h g-1 for the bare Fe2O3, 241.2 mA h g-1 for HCNFs and 486.4 mA h g-1 for Fe2O3-HCNFs). These superior properties and facile preparation represent the potential of Fe2O3/HCNF anode materials for LIB application.