CNTs in situ attached to α-Fe2O3 submicron spheres for enhancing lithium storage capacity

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.

Fe2O3/MoO3@NG Heterostructure Enables High Pseudocapacitance and Fast Electrochemical Reaction Kinetics for Lithium-Ion Batteries

Transition metal oxides (TMOs) hold great potential for lithium-ion batteries (LIBs) on account of the high theoretical capacity. Unfortunately, the unfavorable volume expansion and low intrinsic electronic conductivity of TMOs lead to irreversible structural degradation, disordered particle agglomeration, and sluggish electrochemical reaction kinetics, which result in perishing rate capability and long-term stability. This work reports an Fe₂O₃/MoO₃@NG heterostructure composite for LIBs through the uniform growth of Fe₂O₃/MoO₃ heterostructure quantum dots (HQDs) on the N-doped rGO (NG). Due to the synergistic effects of the "couple tree"-type heterostructures constructed by Fe₂O₃ and MoO₃ with NG, Fe₂O₃/MoO₃@NG delivers a prominent rate performance (322 mA h g^-1 at 20 A g^-1, 5.0 times higher than that of Fe₂O₃@NG) and long-term cycle stability (433.5 mA h g^-1 after 1700 cycles at 10 A g^-1). Theoretical calculations elucidate that the strong covalent Fe-O-Mo, Mo-N, and Fe-N bonds weaken the diffusion energy barrier and promote the Li⁺-ion reaction to Fe₂O₃/MoO₃@NG, thereby facilitating the structural stability, pseudocapacitance contribution, and electrochemical reaction kinetics. This work may provide a feasible strategy to promote the practical application of TMO-based LIBs.

Single-Crystal α-Fe2O3 with Engineered Exposed (001) Facet for High-Rate, Long-Cycle-Life Lithium-Ion Battery Anode

Designing electrode materials with engineered exposed facets provides a novel strategy to improve their electrochemical properties. However, the controllability of the exposed facet remains a daunting challenge, and a deep understanding of the correlation between exposed facet and Li⁺-transfer behavior has been rarely reported. In this work, single-crystal α-Fe₂O₃ hexagonal nanosheets with an exposed (001) facet are prepared with the assistance of aluminum ions through a one-step hydrothermal process, and structural characterizations reveal an Al³⁺-concentration-dependent-growth mechanism for the α-Fe₂O₃ nanosheets. Furthermore, such α-Fe₂O₃ nanosheets, when used as lithium-ion battery anodes, exhibit high specific capacity (1261.3 mAh g^-1 at 200 mA g^-1), high rate capability (with a reversible capacity of approximately 605 mAh g^-1 at 10 A g^-1), and excellent cyclic stability (with a capacity of over 900 mAh g^-1 during 500 cycles). The superior electrochemical performance of α-Fe₂O₃ nanosheets is attributed to the pseudocapacitive behavior, Al-doping in the α-Fe₂O₃ structure, and improved Li⁺-transfer property across the (001) facet, as elucidated by first-principles calculations based on density functional theory. These results reveal the underlying mechanism of Li⁺ transfer across different facets and thus provide insights into the understanding of the excellent electrochemical performance.

FeSe2/carbon nanotube hybrid lithium-ion battery for harvesting energy from triboelectric nanogenerators

FeSe2-carbon nanotube (FeSe2-CNT) hybrid microspheres are investigated as anode materials for lithium ion batteries (LIBs), exhibiting a high specific capacity of 571.2 mA h g-1 at 0.5 A g-1 with excellent rate performance and cycling stability. The FeSe2-CNT hybrid LIBs could withstand the high-voltage pulse of triboelectric nanogenerators (TENGs) and be charged by TENGs directly for harvesting energy with high stability.

Hydrothermal synthesis and characterization of α-Fe2O3/C using acid-pickled iron oxide red for Li-ion batteries

To recycle the waste and meet the demand for anode materials for Li-ion battery, α-Fe₂O₃/C for use as anode material is successfully prepared via a simple hydrothermal process using acid-pickled iron oxide red as raw material. The techniques of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy are used to characterize the product. The synthesis conditions, including temperature and time, are optimized by orthogonal experimental design. The optimal reaction temperature, reaction time, Fe₂O₃/SO₄^2- ratio, Fe₂O₃/glucose ratio are 120 °C, 30 h, 20:2 and 1:1, respectively. The sample prepared at optimal conditions exhibits a high initial specific capacity of 1144/1535 mA h g^-1 at 100 mA g^-1 and a superior cycling performance of ˜800 mA h g^-1 after 200 cycles. Accordingly, this method provides information for the synthesis of α-Fe₂O₃/C with acid-pickled iron oxide red for the first time, which may help alleviate the problem of energy shortage and environmental pollution through the rational use of resources.

Effect of Different Binders on the Electrochemical Performance of Metal Oxide Anode for Lithium-Ion Batteries

When testing the electrochemical performance of metal oxide anode for lithium-ion batteries (LIBs), binder played important role on the electrochemical performance. Which binder was more suitable for preparing transition metal oxides anodes of LIBs has not been systematically researched. Herein, five different binders such as polyvinylidene fluoride (PVDF) HSV900, PVDF 301F, PVDF Solvay5130, the mixture of styrene butadiene rubber and sodium carboxymethyl cellulose (SBR+CMC), and polyacrylonitrile (LA133) were studied to make anode electrodes (compared to the full battery). The electrochemical tests show that using SBR+CMC and LA133 binder which use water as solution were significantly better than PVDF. The SBR+CMC binder remarkably improve the bonding capacity, cycle stability, and rate performance of battery anode, and the capacity retention was about 87% after 50th cycle relative to the second cycle. SBR+CMC binder was more suitable for making transition metal oxides anodes of LIBs.

Scalable synthesis of nanometric α-Fe2O3 within interconnected carbon shells from pyrolytic alginate chelates for lithium storage

By combining naturally abundant iron ions and sodium alginate into conventional wet-spinning and pyrolysis processes, α-Fe₂O₃ could be nanostructured and carbon-coated in a facile and scalable technique.

Improved electrochemical performance of CoS2–MWCNT nanocomposites for sodium-ion batteries

The CoS₂–MWCNT electrode delivers superior cyclic stability with a capacity retention of 568 mA h g⁻¹ after 100 cycles in NaSO₃F₃-DGM.