Ionics最新文献

High-capacity silicon anode is one of the ideal anode materials for the next generation, but the volume expansion effect and low conductivity hinder its development. In this study, a simple and low-cost method was employed to prepare micron-sized silicon raw materials. Subsequently, a hard carbon-coated structure was combined with the metal modification method to successfully prepare hard carbon–coated silver-modified silicon particle material. Due to the hard carbon coating structure, Si/Ag@HC materials can effectively alleviate the volume expansion of silicon, and the modification of metallic silver can not only improve the conductivity of silicon, but also further enhance the ability to limit the volume expansion effect. The Si/Ag@HC maintains a specific capacity of 997.05 mAh g⁻¹ after 200 cycles at a current density of 0.5C, and it also shows an excellent rate performance of over 600 mAh g⁻¹ at a current density of 2C.

In this study, the structural, electrochemical and optical properties of Lithium manganese oxide (LiMn₂O₄) were studied through first-principles calculations based on density functional theory (DFT) using generalized gradient approximation (GGA). The LiMn₂O₄ compound is metallic and The MnO₂ has a direct band gap equal to 0.42 eV using the GGA-PBE (Perdew-Burke-Ernzerhof) approach, 0.21 eV using the GGA-mBJ (modified Becke-Johnson) approach and 2.21 eV using the DFT + U (Density Functional Theory for the Hubbard model) approach. The insertion and extraction of lithium ions induce slight changes in the crystal volume of MnO₂. In addition, the valence state of manganese shifts from + 4 to + 3.5 upon lithium insertion in MnO₂. The spin polarisation (SP%) of LiMn₂O₄ is 24% at the Fermi level (E_F). We found that The Curie temperature (T_c) of LiMn₂O₄ equals 924 K using the GGA-PBE method, 955 K using the GGA-mBJ method and 1290 K using the DFT + U method. The calculations show that the typical full-cycle LiMn₂O₄ battery balancing voltage (V_cell) is 3.4 V and the cell capacity is 148 mAh.g⁻¹. We also found that the energy density of the cell is 504 Wh.kg⁻¹. We determined the optical properties of the two materials in particular absorption and conductivity. The static dielectric constants e₁(0) of LiMn₂O₄ and MnO₂ compounds are 39.64 and 9.08 respectively. The LiMn₂O₄ compound shows an excellent absorption capacity in the UV region, indicating its potential application in optical memory devices. The high reflectivity in low energy ranges opens the possibility of using LiMn₂O₄ as a coating material to reduce solar heating. The calculated formation energies confirmed that the LiMn₂O₄ and MnO₂ compounds are thermodynamically stable. This means that LiMn₂O₄ is more suitable for use in batteries and optoelectronic applications.

The performance of fuel cells is influenced by numerous factors, with operating temperature being particularly crucial. This study aims to analyze fuel cell performance across various temperatures and optimize operational parameters at the optimal temperature to enhance both performance and lifespan. The research identifies 69.9 °C as the optimal temperature for fuel cells, with an efficient operating temperature range of 60–80 °C. Additionally, the optimal flow rate range is determined to be 1000–1600 ml/min. It is also noted that the influence of back pressure on fuel cell performance diminishes when it exceeds 2.5 bar. Furthermore, this study employs a Gaussian process regression model to optimize fuel cell performance under different combinations of temperature, flow rate, and back pressure. The regression analysis predicts that the optimum operating temperature is 71 °C, with an optimal back pressure range of 0.9–1.4 bar and a flow rate range of 1310–1600 ml/min.

A novel binary electrolyte composed of the planar structured 1-allyl-3-methylimidazolium dicyanamide (AMIM-DCA) ionic liquid (IL) mixed with acetonitrile-based iodide/tri-iodide electrolyte was prepared for sustainable dye-sensitized solar cells (DSSCs). Under a 2.56 mW.cm⁻² light-emitting diode (LED), binary electrolyte cells (20 wt% AMIM-DCA) showed a significant increase in open-circuit voltage (V_oc) (628 mV, i.e., + 26.7% compared to cells without IL) and electron lifetime (43 ms, compared to 19 ms for cells without IL), which means a reduction in the dark current. Meanwhile, the short-circuit photocurrent density (J_sc) decreased due to the increase in viscosity, a result consistent with the increase in charge transfer resistance (R_ct) at the photoanode/electrolyte interface. The conversion efficiency (η) of cells with 20 wt% IL (η = 2.59%) increased by 20% compared to cells without IL (η = 2.16%). The AMIM-DCA ionic liquid, being placed by its positive cation (AMIM⁺) near the photoanode, competes with the oxidant I₃⁻ and reduces the dark current. The fill factor (ff) also reached 58.5% with 20 wt% IL, compared to 49.4% without IL. The IL improved the stability of the cells under solar irradiation: the reduced volatility of the electrolyte compensates for the quality of the sealing. Operating temperatures increase the fluidity of the binary electrolyte over time, thereby increasing the J_sc and η (+ 45.4% after 30 min of solar irradiation). This indicates better thermal stability and extended cell lifecycle.

Manganese-based aqueous zinc-ion batteries have attracted significant attention and research in the academic community due to their good cycling stability and high capacity. It has been found that manganese-based aqueous zinc-ion batteries exhibit excellent safety in energy storage applications. In this study, cobalt-modified manganese-based composites were synthesized via the hydrothermal method. The optimal synthesis route was achieved by optimizing the amount of cobalt, hydrothermal conditions, and calcination conditions. The manganese-based material prepared under the optimal conditions exhibited maximum capacity of 425.35 mAh/g at current density of 50 mA/g, and capacity of 296.05 mAh/g at current density of 100 mA/g. The SEM characterization revealed that the material had a microstructure of cubic blocks with surface protrusions, featuring triangular and trapezoidal cross-sections of the protrusions. The EDS analysis indicated that the main components on the material surface were Mn, C, and O element. The infrared and Raman spectroscopy confirmed the presence of Mn–O bonds and carbonate structures in the material. After refinement and quantitative analysis, the XRD analysis identified the main components of the composite material as MnCO₃, Mn₃N₂, and Mn₂O₃, with a small amount of cobalt oxide present.

This work reports the synthesis and comprehensive physicochemical characterization of ethyl-dimethyl-(ferrocenylmethyl)ammonium bis(trifluoromethylsulfonyl)imide ([Fc1N112][NTf₂]) ionic liquid—a promising electrolyte component of redox-flow batteries. The structure of [Fc1N112][NTf₂] was analyzed by XRD, NMR, and XPS. The ionic conductivities of [Fc1N112][NTf₂] solutions in acetonitrile were measured in the temperature range of 298–348 K and analyzed using the Casteel-Amis, Arrhenius, and Vogel-Fulcher-Tamman equations. The thermo-gravimetric analysis confirmed the high thermal stability of [Fc1N112][NTf₂] up to 570 K. The densities of the [Fc1N112][NTf₂] binary solutions were measured, and the coefficients of thermal expansion were calculated. Electrochemical stability of [Fc1N112][NTf₂] was tested by cyclic voltammetry using [EMIm][NTf₂] as a supporting electrolyte. A large electrochemical stability window of 5.38 V was detected.

Graphene-based membranes have extensive applications, including nanofiltration separation performances, but the efficient water flux and rejection rates are greatly challenging. The present study includes the synthesis of zirconium oxide (ZrO₂) nanoparticles and their use as the pillars among reduced graphene oxide (rGO) sheets of ZrO₂/rGO membranes. The citrus peel extract was used as the reducing and stabilizing agent in the nanoparticles synthesis and GO reduction. These nanoparticles enhanced both the water flux to 229 L m⁻² h⁻¹ bar⁻¹ and the rejection rate of molecular and salt species as 98% depending upon the size exclusion effect. Due to the outstanding chemical nature of ZrO₂/rGO membranes, these are highly stable in aqueous media including acidic and alkaline nature. Depending upon the performance of presently synthesized membranes, it can be anticipated that the deposited metal oxide/rGO membranes are highly advantageous industrially due to their efficient permeation and rejection activities.

Proton exchange membrane fuel cells (PEMFCs) have emerged as devices to replace high-emission, highly polluting fossil fuels, owing to their clean, low-carbon, and zero-pollution characteristics. However, challenges such as high production costs and maintenance difficulties have impeded their commercialization. Addressing this issue, optimization studies on PEMFC flow fields become crucial. This study proposes a novel central spiral flow field design and establishes a three-dimensional model for central spiral flow field PEMFCs. Utilizing the Taguchi method and setting target functions, a 10-parameter, 3-level optimization study is conducted on the structural and physical parameters of this flow field. The target functions primarily focus on increasing current density while minimizing pressure drop losses. Results indicate that under consistent conditions, the central spiral flow field exhibits superior polarization performance and higher output power compared to traditional basic parallel flow fields. Additionally, the L₂₇(3¹⁰) orthogonal array established through the Taguchi method is analyzed using both the intuitive method and range analysis, leading to the identification of two optimal flow field design schemes. A comparison between the two reveals that the scheme obtained through the intuitive method shows more significant advantages. This scheme is then selected as the optimal central spiral flow field and compared with a parallel flow field under the same conditions. The results indicate that, compared to the parallel flow field, the optimal central spiral flow field increases the limiting current density by 73.8%, the maximum power density by 107%, and the net power at an operating voltage of 0.6 V by 89.4%.

The strong worldwide economic expansion and rapid industrial advancement have led to a pressing energy dilemma. Interestingly, there has been a transition from conventional renewable energy sources to innovative and environmentally friendly alternatives. Supercapacitors are widely acknowledged as a cost-efficient and exceptionally efficient technique for storing energy. The search for an ideal approach to improve energy storage and expand the potential operating range has resulted in the recognition of a mutually beneficial impact on binary metal oxide nanocomposites (NCs). In this context, a hydrothermal approach was used to manufacture a nanocomposite of Nb₂O₅-La₂O₃ which was then ultrasonically characterized to achieve a precise particle structure. Moreover, the vibrational characteristics, crystallographic structure, particle morphology, and size were examined via FT-IR, XRD, FE-SEM, and HR-TEM analysis. The electrochemical analysis demonstrated that the Nb₂O₅-La₂O₃ NCs displayed an impressive specific capacitance of 825 Fg^-1 when subjected to a current density of 1 Ag^-1. In addition, the Trasatti and Dunns plot analysis found that the electrochemical behavior of the Nb₂O₅-La₂O₃ NCs was mostly characterized by 91.9% capacitance and 8.1% diffusion percentages. Notably, the built Nb₂O₅-La₂O₃//AC ASC displayed energy density (53.75 Wh/kg) and a noteworthy power density of 900 W/kg. Evaluating capacitance retention and coulombic efficiency over 10,000 continuous cycles indicated a significant performance with retention rates of 74.7% and 69.6%, respectively. Overall, the binary Nb₂O₅-La₂O₃ NCs are interesting supercapacitor electrodes due to their electrochemical properties.

The combination of Fe₂O₃ with other transition metal oxides can effectively improve the electrochemical performance of Fe₂O₃. Transition metal oxide MnO₂ was used to modify ring-like Fe₂O₃. Core–shell Fe₂O₃@MnO₂ nanoring composites were synthesized by hydrothermal method. The Fe₂O₃@MnO₂ composite exhibits excellent electrochemical performance in cycling and rate performance tests due to the synergistic effect of the Fe₂O₃ ring and MnO₂ shell. After 100 cycles at 0.1 C current density, the specific discharge capacity can reach 893.6 mAh g⁻¹. After cycling at 2 C high current density, when the current density is restored to 0.1 C, the reversible specific capacity can reach 867.1 mAh g⁻¹. The experimental results show that the core–shell composite with other transition metal oxides can effectively improve the cycle stability and rate performance of Fe₂O₃ anode materials.