NiFe2O4 porous nanorods/graphene composites as high-performance anode materials for lithium-ion batteries

High-Entropy Oxide for Highly Efficient Luminol-Dissolved Oxygen Electrochemiluminescence and Biosensing Applications

The luminol-dissolved O₂ (DO) electrochemiluminescence (ECL) sensing system has recently gained growing interest; however, the drawback of the ultra-low ECL signal response greatly hinders its potential quantitative applications. In this work, for the first time, we explored the use of high entropy oxide (HEO) comprising five metal ingredients (Ni, Co, Cr, Cu, and Fe), to accelerate the reduction reaction of DO into reactive oxygen species (ROS) for boosting the ECL performance of the luminol-DO system. Benefiting from the existing abundant oxygen vacancies induced by the unique crystal structure of the HEO, DO could be efficiently converted into ROS, thus significantly boosting the performance of the corresponding ECL sensor (with an ∼240-fold signal enhancement in this study). As a proof of concept, under optimal conditions, the developed HEO-involved luminol-DO ECL sensing system was successfully applied for efficient biosensing of dopamine and alkaline phosphatase with a fine linear range from 1 pM to 10 nM and from 0.01 to 100 U/L as well as a low limit of detection of 5.2 pM and 0.008 U/L, respectively.

The Effect of Annealing Temperature on the Synthesis of Nickel Ferrite Films as High-Capacity Anode Materials for Lithium Ion Batteries

Anode materials providing a high specific capacity with a high cycling performance are one of the key parameters for lithium ion batteries' (LIBs) applications. Herein, a high-capacity NiFe2O4(NFO) film anode is prepared by E-beam evaporation, and the effect of the heat treatment is studied on the microstructure and electrochemical properties of LIBs. The NiFe2O4 film annealed at 800 °C (NFO-800) showed a highly crystallized structure and different surface morphologies when compared to the electrode annealed at a lower temperature (NFO-600, NFO-700). In the electrochemical measurements, the high specific capacity (1804 mA g-1) and capacity retention ratio (95%) after 100 cycles were also achieved by the NFO-800 electrode. The main reason for the good electrochemical performance of the NFO-800 electrode is a high structure integrity, which could improve the cycle stability with a high discharge capacity. The NiFe2O4 electrode with an annealing process could be further proposed as an alternative ferrite material.

High-Capacity Anode Material for Lithium-Ion Batteries with a Core-Shell NiFe2O4/Reduced Graphene Oxide Heterostructure

A novel composite consisting of transition-metal oxide and reduced graphene oxide (rGO) has been designed as a highly promising anode material for lithium-ion batteries (LIBs). The anode material for LIBs exhibits high-rate capability, outstanding stability, and nontoxicity. The structural characterization techniques, such as X-ray diffraction, Raman spectra, and transmission electron microscopy, indicate that the material adopts a unique core-shell structure with NiFe₂O₄ nanoparticles situated in the center and an rGO layer coated on the surface of NiFe₂O₄ particles (denoted as NiFe₂O₄/rGO). The NiFe₂O₄/rGO material with a core-shell structure exhibits an excellent electrochemical performance, which shows a capacity of 1183 mA h g^-1 in the first cycle and maintains an average capacity of ∼1150 mA h g^-1 after 900 cycles at a current density of 500 mA g^-1. This work provides a broad field of vision for the application of transition-metal-oxide materials in electrodes of lithium-ion batteries, which is of great significance for further development of lithium-ion batteries with excellent performance.

Ice-interface assisted large-scale preparation of polypyrrole/graphene oxide films for all-solid-state supercapacitors

In this paper, large-scale, self-standing polypyrrole/graphene oxide (PPy/GO) nanocomposite films were prepared by an environmentally friendly and easy-to-operate confined polymerization method, and were also assembled as electrode materials for symmetric all-solid-state supercapacitors. In this paper, large-scale, self-standing polypyrrole/graphene oxide (PPy/GO) nanocomposite films were prepared by an environmentally friendly and easy-to-operate confined polymerization method, and were also assembled as electrode materials for symmetric all-solid-state supercapacitors. The morphology, chemical structure and electrochemical property were characterized by field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS), respectively. The lamellar structure of GO and both strong interaction with ice and pyrrole could promote polymerization of pyrrole and improve the compactness of the film. With the aid of GO, the conjugation length of PPy increased, the resistance of the material decreased, and the electrochemical energy storage of the composite film was significantly enhanced. In the case of 2.5 wt% GO, the prepared PPy/GO nanocomposite supercapacitor exhibited a high area specific capacitance of 97.3 mF cm^-2 at 1 mA cm^-2. Furthermore, the PPy/GO film supercapacitor also showed excellent cycling stability and good flexibility.

Preparations of NiFe2O4 Yolk-Shell@C Nanospheres and Their Performances as Anode Materials for Lithium-Ion Batteries

At present, lithium-ion batteries (LIBs) have received widespread attention as substantial energy storage devices; thus, their electrochemical performances must be continuously researched and improved. In this paper, we demonstrate a simple self-template solvothermal method combined with annealing for the synthesis of NiFe2O4 yolk-shell (NFO-YS) and NiFe2O4 solid (NFO-S) nanospheres by controlling the heating rate and coating them with a carbon layer on the surface via high-temperature carbonization of resorcinol and formaldehyde resin. Among them, NFO-YS@C has an obvious yolk-shell structure, with a core-shell spacing of about 60 nm, and the thicknesses of the NiFe2O4 shell and carbon shell are approximately 15 and 30 nm, respectively. The yolk-shell structure can alleviate volume changes and shorten the ion/electron diffusion path, while the carbon shell can improve conductivity. Therefore, NFO-YS@C nanospheres as the anode materials of LIBs show a high initial capacity of 1087.1 mA h g-1 at 100 mA g-1, and the capacity of NFO-YS@C nanospheres impressively remains at 1023.5 mA h g-1 after 200 cycles at 200 mA g-1. The electrochemical performance of NFO-YS@C is significantly beyond NFO-S@C, which proves that the carbon coating and yolk-shell structure have good stability and excellent electron transport ability.

Construction of heterostructured NiFe2O4-C nanorods by transition metal recycling from simulated electroplating sludge leaching solution for high performance lithium ion batteries

NiFe2O4 has been regarded as one of the promising candidates for lithium-ion battery (LIB) anode materials due to its high theoretical specific capacity. However, the large volume expansion and pulverization of NiFe2O4 during the charge/discharge process result in severe capacity fading. Herein, heterostructured NiFe2O4-C nanorods have been successfully fabricated by recovering transition metals from simulated electroplating sludge leaching solution. The constructed NiFe2O4-C heterointerface plays a vital role in accommodating volume change, stabilizing the reaction products and providing rapid electron and Li+ ion transportation ability, resulting in a high and stable Li+ accommodation performance. The fabricated NiFe2O4-C nanorods demonstrate a high specific capacity (889.9 mA h g-1 at 100 mA g-1), impressive rate capability (861.5, 704.5, 651.4, 579.6 and 502.1 mA h g-1 at 0.2, 0.6, 1.0, 2.0 and 5.0 A g-1) and cycling stability (650.2 mA h g-1 at 2 A g-1 after 500 cycles). This work exemplifies a facile and effective approach for the fabrication of high performance LIB electrode materials by recycling metals from electroplating sludge in an application-oriented manner.