The continuous shuttling of dissolved polysulfides between the electrodes is the primary cause for the rapid decay of lithium−sulfur batteries. Modulation of the separator− electrolyte interface through separator modification is a promising strategy to inhibit polysulfide shuttling. In this work, we develop a graphene oxide and ferrocene comodified polypropylene separator with multifunctionality at the separator−electrolyte interface. The graphene oxide on the functionalized separator could physically adsorb the polysulfide while the ferrocene component could effectively facilitate the conversion of the adsorbed polysulfide. Due to the combination of these beneficial functionalities, the separator exhibits an excellent battery performance, with a high reversible capacity of 409 mAh g −1 after 500 cycles at 0.2 C. We anticipate that the combinatorial separator functionalization proposed herein is an effective approach for improving the performance of lithium−sulfur batteries.
Summary
A series of different α‐Fe2O3 nanoparticles composites containing different amounts of graphene coatings have been successfully prepared using a simple electrostatic self‐assembly (ESA) method. The structure and electrochemical properties of these α‐Fe2O3@graphene composites have been investigated. The α‐Fe2O3 nanoparticles composite containing 40 wt% graphene coating exhibits the highest specific capacity (385 mAh g−1) under 1000 mA g−1, resulting in superior cycle stability with no downward trend after 500 cycles. These results demonstrate that graphene coatings can be used to enhance the electrochemical properties and morphological stability of α‐Fe2O3 nanoparticles as anodic materials for high performance lithium‐ion batteries (LIBs). The low‐energy self‐assembly method employed in the paper has good potential for the broad‐scale preparation of other graphene‐modified materials because of its simplicity and the relatively low temperature conditions.
Conducting Nafion/SiO2 composite membranes were successfully prepared using a simple electrostatic self-assembly method, followed by annealing at elevated temperatures of 240, 270, and 300 °C. Membrane performance was then investigated in vanadium redox flow batteries (VRB). These annealed composite membranes demonstrated lower vanadium permeability and a better selectivity coefficient than pure Nafion membranes. The annealing temperature of 270 °C created the highest proton conductivity in the Nafion/SiO2 composite membranes. The microstructures of these membranes were analyzed using transmission electron microscopy, small-angle X-ray scattering, and positron annihilation lifetime spectroscopy. This study revealed that exposure to high temperatures resulted in an increase in the free volumes of the composite membranes, resulting in improved mechanical and chemical behavior, with the single cell system containing composite membranes performing better than systems containing pure Nafion membranes.
Summary
We report a novel porous and high‐specific surface area carbon support material (C‐framework) for PEMFC by the salt‐recrystallization‐fixing HKUST‐1 template. We believe this will be a universal method to convert high‐temperature unstable MOF materials, such as HKUST‐1. NaCl crystals serve as completely closed nanoreactors, which facilitate graphitization and structure inheritance. Electrochemical evaluation showed that the C‐framework loaded with Pt nanoparticles exhibits high ORR activity and excellent electrochemical performance in acidic electrolytes. The PEMFC performance reached a maximum power density of 780 mW/cm2 under the H2/air testing condition in ultra‐low Pt loading (cathode 0.1 mg/cm2).
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