A controllable preparation of two-dimensional cobalt oxalate-based nanostructured sheets for electrochemical energy storage

An electrospinning deposited cobalt oxide nanofiber gas sensing device: selective enhancement as a thermal electronic nose

Cobalt oxide nanofibers (Co3O4 NFs) were synthesized using a two-step procedure involving electrospinning followed by calcination. The microstructural, morphological, and elemental properties of the nanofibers were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The Co3O4 NFs exhibited high structural integrity, chemical purity, and uniform diameters ranging from 20 to 50 nm. Thermal treatment at 600 °C for 3 hours transformed the electrospun fibers into elongated nanofibers composed of interconnected Co3O4 nanoparticles. The gas sensing properties of the Co3O4 NFs were evaluated for ethanol (C2H5OH) detection over a temperature range of 250 to 450 °C. The sensor demonstrated a significant response to ethanol, highlighting their potential for gas sensing applications. When employed as a thermal electronic nose, the device achieved perfect classification (100% accuracy) for six tested gases and demonstrated effective concentration estimation, with an average error of 28.6%.

Tailoring Intrinsic Oxygen Vacancies in P3-Type Na0.66Mn0.66Mg0.33O1.93 to Enhance Oxygen Redox Activity

Integrating oxygen redox reactions with transition metal redox reactions offers a promising strategy to double or triple the energy density for large-capacity battery cathodes. In this study, we have introduced intrinsic oxygen vacancies (VO) into a P3 layered cathode to modulate the electronic structure of O atoms and enhance oxygen redox activity. Rietveld-refined X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy confirm the successful creation of VO in Na0.66Mn0.66Mg0.33O1.93 (OV-NMM). Density functional theory (DFT) calculations reveal that VO in OV-NMM positively enhances the antibonding interaction between Mn and O, directing excess electrons from O holes toward adjacent Mn t2g and O 2p orbitals. This modification significantly improves the reversibility and accelerates Na+ transport kinetics for O2-/O- redox reactions. Ex situ synchrotron-based XRD demonstrates that VO effectively eliminates the O3 phase, reduces Mg2+ migration, and suppresses irreversible structural changes. XAS of Mn K-edge and O K-edge further illustrate the advantageous role of oxygen vacancies in facilitating oxygen redox reactions. These findings highlight the potential of defect engineering, particularly VO, to boost anionic redox activity for high-capacity energy storage applications.

Application of Conductive MOF in Zinc-Based Batteries

The use of conductive MOFs (c-MOFs) in zinc-based batteries has been a popular research direction. Zinc-based batteries are widely used with the advantages of high specific capacity and safety and stability, but they also face many problems. c-MOFs have excellent conductivity compared with other primitive MOFs, and therefore have better applications in zinc-based batteries. In this paper, the transfer mechanisms of the unique charges of c-MOFs: hop transport and band transport, respectively, are discussed and the way of electron transport is further addressed. Then, the various ways to prepare c-MOFs are introduced, among which solvothermal, interfacial synthesis, and postprocessing methods are widely used. In addition, the applications of c-MOFs are discussed in terms of their role and performance in different types of zinc-based batteries. Finally, the current problems of c-MOFs and the prospects for their future development are presented.

MOFs Containing Solid-State Electrolytes for Batteries

The use of metal-organic frameworks (MOFs) in solid-state electrolytes (SSEs) has been a very attractive research area that has received widespread attention in the modern world. SSEs can be divided into different types, some of which can be combined with MOFs to improve the electrochemical performance of the batteries by taking advantage of the high surface area and high porosity of MOFs. However, it also faces many serious problems and challenges. In this review, different types of SSEs are classified and the changes in these electrolytes after the addition of MOFs are described. Afterward, these SSEs with MOFs attached are introduced for different types of battery applications and the effects of these SSEs combined with MOFs on the electrochemical performance of the cells are described. Finally, some challenges faced by MOFs materials in batteries applications are presented, then some solutions to the problems and development expectations of MOFs are given.

All-Electrochemical Nanofabrication of Stacked Ternary Metal Sulfide/Graphene Electrodes for High-Performance Alkaline Batteries

Energy-storage materials can be assembled directly on the electrodes of a battery using electrochemical methods, this allowing sequential deposition, high structural control, and low cost. Here, a two-step approach combining electrophoretic deposition (EPD) and cathodic electrodeposition (CED) is demonstrated to fabricate multilayer hierarchical electrodes of reduced graphene oxide (rGO) and mixed transition metal sulfides (NiCoMnS_x ). The process is performed directly on conductive electrodes applying a small electric bias to electro-deposit rGO and NiCoMnS_x in alternated cycles, yielding an ideal porous network and a continuous path for transport of ions and electrons. A fully rechargeable alkaline battery (RAB) assembled with such electrodes gives maximum energy density of 97.2 Wh kg^-1 and maximum power density of 3.1 kW kg^-1 , calculated on the total mass of active materials, and outstanding cycling stability (retention 72% after 7000 charge/discharge cycles at 10 A g^-1 ). When the total electrode mass of the cell is considered, the authors achieve an unprecedented gravimetric energy density of 68.5 Wh kg^-1 , sevenfold higher than that of typical commercial supercapacitors, higher than that of Ni/Cd or lead-acid Batteries and similar to Ni-MH Batteries. The approach can be used to assemble multilayer composite structures on arbitrary electrode shapes.