Ionics最新文献

As an iron-based fluorophosphate with a two-dimensional layered structure, Na₂FePO₄F (NFPF) has become an ideal cathode material for energy storage applications due to its low cost, high safety, and structural stability. However, the inherently low conductivity and limited kinetic behavior of NFPF result in inferior electrochemical performance, which hinders its commercialization. Herein, we employed a one-step carbon–nitrogen co-doping method to modify NFPF. First, carbon coating effectively enhances the conductivity of the NFPF cathode. Moreover, nitrogen doping introduces additional vacancies and active sites in the carbon layer, providing more Na⁺ diffusion channels. The NFPF/PVP material, synthesized using polyvinylpyrrolidone (PVP) as both the nitrogen and carbon source, delivers a specific capacity of 119 mAh g⁻¹ at 0.1 C, an excellent rate capability of 90 mAh g⁻¹ at 10 C, and unprecedented long-term cycling stability (81.9% capacity retention after 2000 cycles). These properties are significantly superior to those of previously reported NFPF cathode materials. Furthermore, electrochemical impedance spectroscopy (EIS) revealed that the charge transfer resistance of NFPF/PVP (123.59 Ω) is much lower than that of pristine NFPF (500.23 Ω), indicating facilitated charge transfer and faster Na⁺ transport kinetics. The Na⁺ diffusion coefficient of NFPF/PVP (4.78 × 10⁻¹¹ cm² s⁻¹) is two orders of magnitude higher than that of NFPF (3.35 × 10⁻¹³ cm² s⁻¹), further demonstrating that the PVP-derived nitrogen-doped carbon coating effectively improves the reaction kinetics of NFPF. This study provides new strategies and insights for developing cost-effective and high-performance NFPF-based materials.

In this study, a two-step hydrothermal method was used to synthesize a heterostructure Co₃O₄/MnMoO₄ nanorod cluster composite material with a synergistic interface on nickel foam (NF). MnMoO₄ is distributed in short rod-like or granular crystals on the bulk crystal surfaces of Co₃O₄, forming a closely contacted heterostructure, thereby enhancing the electron transport rate at the electrode interface and effectively alleviating issues such as volume expansion and structural collapse during charging and discharging. The rationally designed surface modification structure and abundant Li⁺ reaction sites of Co₃O₄/MnMoO₄ confer excellent rate performance and high capacity. The initial discharge capacity at a current of 0.1 A g⁻¹is approximately 1244 mAh g⁻¹. After 200 cycles, the composite electrode retains a high reversible capacity of approximately 840 mAh g⁻¹. At a high current of 1 A g⁻¹, the reversible capacity is observed to remain at approximately 885 mAh g⁻¹. Furthermore, after 600 cycles at a current density of 1 A g⁻¹, the reversible capacity of the electrode is approximately 306 mAh g⁻¹. These results indicate that Co₃O₄/MnMoO₄ composite materials are a highly promising electrode material.

In this study, the flash points and ionic conductivity of three ternary electrolyte solvents (ethylene carbonate (EC); diethyl carbonate (DEC); and dimethyl carbonate (DMC)) were investigated in lithium-ion batteries. The flash points of the solvent mixtures were experimentally measured and compared with predictions using Raoult’s law and multiple regression analysis. These results indicate that EC increases flash point temperature and ionic conductivity owing to its high dielectric constant and boiling point. In contrast, DMC has a lower flash point because of its low boiling point and high reactivity. The coefficient of determination (R²) and mean absolute error (MAE) suggest that Raoult’s law better predicts overall trends in flash points. Simultaneously, multiple regression analysis provided higher accuracy for specific mixture compositions. Additionally, the ionic conductivities of the ternary electrolyte mixtures were analyzed, demonstrating that DMC maintained high conductivity through polar conformers despite its low dielectric constant. The optimal mixture ratio of EC: DEC: DMC at 7:2:1 achieved a balance with a high flash point (55.5 °C) and high ionic conductivity (9.0 mS cm⁻¹), enhancing battery safety and ionic conductivity. This study highlights the critical role of solvent composition in optimizing lithium-ion battery electrolytes for improved safety and ionic conductivity.

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3D-printing has emerged as a promising method for the fabrication of high loading electrodes to increase the energy density of the lithium-ion batteries (LIBs). The formulation and preparation of the printing inks, however, are not trivial and have a significant impact on the electrochemical and structural properties of the 3D-printed electrodes. Here, a comprehensive investigation is conducted to quantify the impact of binder formulation on the performance of the 3D-printed lithium iron phosphate (LFP) electrodes with active-material loadings beyond 25 mg/cm². This is showcased with the commonly used binders of carboxymethyl cellulose (CMC) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and by highlighting their impact on the printability, microstructure, and cycling behavior of the LFP electrodes made thereof. To do so, a combination of the electrochemical and microstructural characterization techniques is employed to reveal the synergistic effect of the CMC and PEDOT:PSS binders on the mechanical integrity, electrical conductivity, tortuosity, and cycling performance of the 3D-printed LFP electrodes. The results underscore the significance of the binder in optimizing the 3D-printing process for the manufacturing of the energy-dense electrodes.

In this work, a novel Zn₂GeO₄/VS₂ composite electrode was synthesized via a simple hydrothermal method to enhance the electrochemical performance of lithium-ion batteries (LIBs). Comprehensive structural and morphological analyses were carried out using XRD, BET, SEM, TEM, XPS, and FTIR, confirming the successful formation of a well-integrated composite structure. The Zn₂GeO₄ electrode delivers an initial discharge capacity of 578.62 mAh g⁻¹ and retains about 127 mAh g⁻¹ after 400 cycles at a current density of 0.1 A g⁻¹, whereas the Zn₂GeO₄/VS₂ electrode shows an initial discharge capacity of 340 mAh g⁻¹ and maintains nearly the same capacity (340 mAh g⁻¹) at 0.1 A g⁻¹ with enhanced cycling stability over 400 cycles. The electrode exhibited a first-cycle irreversible capacity loss (ICL) of approximately 39%, primarily attributed to solid electrolyte interphase (SEI) formation and initial structural rearrangements. The enhanced performance is attributed to the synergistic interaction between Zn₂GeO₄ and VS₂, which improves lithium-ion diffusion, structural integrity, and electrical conductivity during repeated charge–discharge cycles. This study demonstrates that integrating Zn₂GeO₄ with a 2D layered material like VS₂ is a promising strategy for developing high-performance LIB anodes. Thus, the VS₂-modified Zn₂GeO₄ provides a practical pathway for designing next-generation electrode materials with enhanced capacity and long-term stability Zn₂GeO₄ by incorporating VS₂ nanosheets.

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A concentrated lithium salt solution is widely used as an electrolyte of lithium-ion batteries. We have previously reported that simple and flexible ditopic receptors bearing anion and cation recognition sites forms LiCl complex resulting in the highly concentrated solution in acetonitrile. In this study, we conducted a novel in-situ synthesis by mixing receptor precursors, LiCl, and solvent. We found that the concentration of the receptor•LiCl complex increased from 0.25 M to 3 M, twelve times higher than the conventional simple mixing in acetonitrile. The ionic conductivity of the 3 M solution was successfully measured to be 1.41 × 10⁻² mS cm⁻¹ at 25 °C. We elucidated that the in-situ electrolyte preparation enables us to obtain homogeneous and stable solutions even with high LiCl concentration. Moreover, the oxidation decomposition potential was 6 V vs. Li/Li⁺. This study presents a novel method for the preparation of highly concentrated electrolytes. We could obtain the electrolyte by one-pot synthesis and mixing, which means that in-situ preparation can have a cost-effective advantage.

Lithium-sulfur batteries are promising due to their high energy density, but the shuttle effect of lithium polysulfides (LiPS) limits their performance. In this study, PbTiO₃@Au (PTO@Au) composites were designed to enhance LiPS conversion through spontaneous polarization and surface catalysis. The incorporation of 3 wt% PTO@Au-1.0 in the sulfur cathode significantly improved reaction kinetics, reduced polarization, and suppressed the shuttle effect. This configuration achieved an initial capacity of 572.1 mAh·g⁻¹ at 200 mA·g⁻¹ and retained 405.7 mAh·g⁻¹ at 900 mA·g⁻¹, with a 92.8% capacity retention after 100 cycles. The results, supported by transient photovoltage (TPV) and electrochemical impedance spectroscopy (EIS), demonstrate that combining spontaneous polarization and catalytic action can overcome key challenges in Li-S batteries, offering a promising strategy for improving their performance.

Tungsten trioxide (WO₃) is recognized as one of the promising materials for catalyst support. However, its practical application is still restricted by the low specific surface area and the relatively low conduction band level. An efficient hydrothermal and room temperature plasma technique was employed to synthesize WO₃ nanoparticles (designated as WO₃-Ar), resulting in a higher surface area and the creation of substantial oxygen vacancies on the WO₃ surface. Subsequently, Pd and Ag nanoparticles were deposited onto the WO₃ nanoparticles, which are characterized by a high specific surface area and numerous oxygen vacancies, through hydrogen reduction (PdAg/WO₃-Ar). Electrochemical tests indicate that the PdAg/WO₃-Ar catalysts exhibit superior electrocatalytic efficiency compared to the PdAg/C catalyst. The significantly higher electrocatalytic activity is attributed to several factors: (1) The oxygen vacancy defects and the high unique specific surface area of WO₃-Ar facilitate the anchoring of Pd–Ag nanoparticles and enhance the electrocatalytic performance of Pd–Ag nanoparticles in PdAg/WO₃-Ar catalysts. (2) A catalyst-support interaction exists between Pd–Ag and WO₃-Ar, which significantly boosts the catalytic performance of the PdAg/WO₃-Ar catalyst.

Lithium-iron phosphate batteries play a core role in electric vehicles, providing power energy, promoting industrial development, and protecting the environment. To analyze the effect of temperature on the charge-discharge cycle performance of lithium-iron phosphate batteries for electric vehicles, this study selects experimental materials and equipment and, after selecting performance evaluation indicators, explains the testing methods for different indicators. Subsequently, a charging and discharging experimental platform is built, and the charging and discharging strategies of the battery at different temperatures are designed. The results demonstrated that as the amount of charge and discharge cycles increased, the battery capacity retention rates corresponding to −35 ℃, −25 ℃, and 45 ℃ were gradually decreasing, while the battery capacity retention rate remained basically unchanged at room temperature of 25 ℃. In the second cycle, the discharge energy densities corresponding to the four temperatures were 121.17 Wh/kg, 124.68 Wh/kg, 127.58 Wh/kg, and 126.13 Wh/kg, and the corresponding coulombic efficiency decreases were 4.8%, 4.2%, 0.12%, and 2.3%. As the temperature increased, the battery capacity retention rate, discharge energy density, and coulombic efficiency all increased first and then decreased. The research results can provide information support on temperature effects for the improvement of electric vehicle performance, promoting the enhancement of electric vehicle range.

Proton exchange membrane fuel cells (PEMFCs) are electrochemical devices that directly convert the chemical energy of hydrogen into electricity, with water as the only by-product. The bipolar plate is one of the important parts of the fuel cell, which plays roles such as connecting single cells in series, guiding gases, and providing support. The flow-field structure on the bipolar plate directly affects the distribution of reactant gases, water management, and the overall efficiency of the cell. Therefore, the design and optimization of the flow-field of the bipolar plate are one of the important methods to improve the performance of PEMFCs. This paper focuses on the optimization and improvement of a rhombic flow field with an intersecting structure. The straight edges of the diamond are changed into three different curved-edge structures that curve inward. Through simulation calculations, the oxygen distribution, water distribution, and polarization curves inside the cell after modification are analyzed. The results show that the curved flow field with a circumscribed circle structure is superior to the rhombic flow field in terms of oxygen content, uniformity, water discharge, and output power, but it also has a higher pressure drop. The elliptical flow field is superior to the rhombic flow field in terms of the uniformity of oxygen output and output power, but it also has a higher pressure drop and water accumulation. The parabolic flow field is superior to the rhombic flow field in terms of oxygen uniformity and output power, is similar to the rhombic flow field in terms of water discharge, and has a higher pressure drop than the rhombic flow field.