Recent advances in the synthesis of mesoporous materials and their application to lithium-ion batteries and hybrid supercapacitors

Effect of Sodium Phosphate Coating on Cu and Mg-Substituted P2-Na0.67Ni0.33Mn0.67O2 for Improving the Cycling Performance of Sodium-Ion Capacitors

Sodium-ion capacitors (SICs) bridge the performance gaps between batteries and supercapacitors by providing a high energy and power density in a single configuration. As battery-type active materials, sodium preintercalated layered metal oxides are desirable owing to their unique crystal structure, simple synthesis process, and high working voltage. However, their poor cyclic stability and low kinetics limit their application. Herein, we report increased rate capability and cycle stability achieved by introducing transition metal substitution and surface coating strategies. By substituting a portion of Ni and Mn with Cu and Mg (the sample name was denoted as NMCM), the P2-O2 transition which occurs at high voltages was alleviated. Additionally, a thin and uniform sodium phosphate coating layer suppressed surface side reactions occurring during charge-discharge processes, as observed through ex-situ X-ray photoelectron spectroscopy and ex-situ transmission electron microscopy. Compared to the pristine sample, the capacity improved by 48% at a high current density of 4 A g-1. After 100 cycles, the sodium-phosphate-coated sample (NMCM@P) retained about 90% of its capacity, whereas NMCM had a capacity retention of 63%. When evaluating the longer stability of SIC full cells, NMCM@P exhibited an outstanding stability of 71% after 5000 cycles. This was higher than that of NMCM, which retained only 17% of its initial capacity.

NiO/Ni Nanowafer Aerogel Electrodes for High Performance Supercapacitors

Transition metal oxide aerogels are a fascinating class of compounds that have received considerable attention in the last decade owing to their unique and exceptional properties, including high porosity, large surface area, and ultralow density. In this study, α-Ni(OH)₂ aerogels and annealed NiO/Ni aerogels were used to design and fabricate a two-electrode supercapacitor device. The physicochemical properties of the as-synthesized aerogels were characterized through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, the Brunauer-Emmett-Teller theory, and X-ray photoelectron spectroscopy studies. The annealed NiO/Ni aerogels showed a (specific capacitance of 1060 F/g) specific capacity of 422 C/g at 1 A/g current density and with good cycling stability (up to 10,000 cycles). The supercapacitor also demonstrated an energy density of 32.4 Wh/kg and power density of 1800 W/kg at a current density of 2 A/g. The specific capacitance of NiO/Ni aerogels was more than twice that of the α-Ni(OH)₂ aerogels. The practical applications of the aerogel were demonstrated by fabricating a two-electrode device.

Nanofibers Comprising Interconnected Chain-Like Hollow N-Doped C Nanocages as 3D Free-Standing Cathodes for Li-S Batteries with Super-High Sulfur Content and Lean Electrolyte/Sulfur Ratio

The development of a suitable cathode host that withstands high sulfur content/loading and low electrolyte/sulfur (E/S) ratio is particularly important for practically sustainable Li-S batteries. Herein, a facile approach is utilized to prepare free-standing 3D cathode substrates comprising nitrogen-doped carbon (N-C) scaffold and metal-organic framework derived interconnected chain-like hollow N-C nanocages, forming a highly porous N-C nanofiber (HP-N-CNF) framework. The N-C skeleton provides highly conductive pathways for fast lithium ion/electron diffusion. The hollow interconnected N-C nanocages not only offer enough space to absorb a high volume of active material but also effectively channelize severe volume stress during the electrochemical performance. The Li-S cell utilizing HP-N-CNF as cathode host displays exceptional battery parameters with high effective sulfur content (83.2 wt%), ultrahigh sulfur loading (14.3 mg cm^-2 ), and low E/S ratio (6.8 μL mg^-1 ). The Li-S cell exhibits a maximum areal capacity of 12.2 mAh cm^-2 which stabilizes at ≈5.5 mAh cm^-2 after the 130th cycle at 0.05 C-rate and is well above the theoretical threshold. Therefore, the proposed unique nanostructure synthesis approach would open new frontiers for developing more realistic and sustainable host materials with feasible battery parameters for various energy storage applications.

Silane Modification of Mesoporous Materials for the Optimization of Antiviral Drug Adsorption and Release Capabilities in Vaginal Media

Three different functionalities have been incorporated into mesoporous materials by means of a coupling reaction with the siloxanes 3-glycidoxypropyl-trimethoxysilane (GLYMO), 3-methacryloxypropyl-trimethoxysilane (MEMO), and 3-mercaptopropyl-trimethoxysilane (MPTMS). The disposition of the different functional groups, as well as the interaction mechanism, with the mesoporous substrate has been identified. The amount of the antiviral drug acyclovir (ACV) adsorbed depends not only on the available surface area but also on the chemical or physicochemical interactions between functionalities. The drug adsorption isotherm of the materials functionalized with GLYMO and MPTMS follow mechanisms dependent on the different surface coverage and the possibilities to establish physicochemical interactions between the drug molecule and the functionalities. On the contrary, when functionalizing with MEMO, the dominant adsorption mechanism is characteristic of chemically bonded adsorbates. The ACV release kinetics is best fitted to the Weibull model in all the functionalized materials. When the MTPMS is used as a functionalizing agent, the drug diffusion occurs at low kinetics and homogeneously along the mesoporous channels.

Rational Design of Perforated Bimetallic (Ni, Mo) Sulfides/N-doped Graphitic Carbon Composite Microspheres as Anode Materials for Superior Na-Ion Batteries

Highly conductive 3D ordered mesoporous Ni₇ S₆ -MoS₂ /N-doped graphitic carbon (NGC) composite (P-NiMoS/C) microspheres are prepared as anode materials for Na-ion batteries. The rationally designed nanostructure comprises stable Ni₇ S₆ - and MoS₂ -phases along with the homogeneously distributed ordered mesopores (ϕ = 50 nm) over the external and internal structures generated through thermal decomposition of polystyrene nanobeads (ϕ = 100 nm). Therefore, the P-NiMoS/C microspheres deliver initial discharge capacities of 662, 419, 373, 300, 231, 181, and 146 mA h g^-1 at current densities of 0.5, 1, 2, 4, 6, 8, and 10 A g^-1 , respectively. Furthermore, P-NiMoS/C exhibits a stable discharge capacity of 444 mA h g^-1 at the end of the 150th cycle at a current density of 0.5 A g^-1 , indicating higher cycling stability than the filled, that is, non-mesoporous, Ni₃ S₂ -MoS₂ /NGC (F-NiMoS/C) microspheres and filled carbon-free Ni₃ S₂ -MoS₂ (F-NiMoS) microspheres. The superior electrochemical performance of P-NiMoS/C microspheres is attributed to the rapid Na⁺ ion diffusion, alleviation of severe volume stress during prolonged cycling, and higher electrical conductivity of NGC, which results in fast charge transfer during the redox processes. The results in the present study can provide fundamental knowledge for the development of multicomponent, porous, and highly conductive anodes for various applications.

Graphene-Based Two-Dimensional Mesoporous Materials: Synthesis and Electrochemical Energy Storage Applications

Graphene (G)-based two dimensional (2D) mesoporous materials combine the advantages of G, ultrathin 2D morphology, and mesoporous structures, greatly contributing to the improvement of power and energy densities of energy storage devices. Despite considerable research progress made in the past decade, a complete overview of G-based 2D mesoporous materials has not yet been provided. In this review, we summarize the synthesis strategies for G-based 2D mesoporous materials and their applications in supercapacitors (SCs) and lithium-ion batteries (LIBs). The general aspect of synthesis procedures and underlying mechanisms are discussed in detail. The structural and compositional advantages of G-based 2D mesoporous materials as electrodes for SCs and LIBs are highlighted. We provide our perspective on the opportunities and challenges for development of G-based 2D mesoporous materials. Therefore, we believe that this review will offer fruitful guidance for fabricating G-based 2D mesoporous materials as well as the other types of 2D heterostructures for electrochemical energy storage applications.

Synthesis and Characterization of π-SnS Nanoparticles and Corresponding Thin Films

Tin sulfide polymorph (π-SnS) nanoparticles exhibit promising optoelectrical characteristics for photovoltaic and hydrogen production performance, mainly because of the possibility of tuning their properties by adjusting the synthesis conditions. This study demonstrates a chemical approach to synthesize π-SnS nanoparticles and the engineering of their properties by altering the Sn precursor concentration (from 0.04 M to 0.20 M). X-ray diffraction and Raman studies confirmed the presence of pure cubic SnS phase nanoparticles with good crystallinity. SEM images indicated the group of cloudy shaped grains, and XPS results confirmed the presence of Sn and S in the synthesized nanoparticles. Optical studies revealed that the estimated energy bandgap values of the as-synthesized π-SnS nanoparticles varied from 1.52 to 1.68 eV. This work highlights the effects of the Sn precursor concentration on the properties of the π-SnS nanoparticles and describes the bandgap engineering process. Optimized π-SnS nanoparticles were used to deposit nanocrystalline π-SnS thin films using the drop-casting technique, and their physical properties were improved by annealing (300 °C for 2 h).