Henan Normal University

About: Henan Normal University is a education organization based out in Xinxiang, China. It is known for research contribution in the topics: Catalysis & Ionic liquid. The organization has 10863 authors who have published 11077 publications receiving 166773 citations.

Temperature Effects on the Electrochemical Behavior of Spinel LiMn2O4 in Quaternary Ammonium-Based Ionic Liquid Electrolyte

Abstract: Temperature dependence of the physiochemical characteristics of a room-temperature ionic liquid consisting of trimethylhexylammonium (TMHA) cation and bis(trifluoromethane) sulfonylimide (TFSI) anion containing different concentrations of LiTFSI salt was examined. Electrochemical properties of a spinel LiMn(2)O(4) electrode in 1 M LiTFSI/TMHA-TFSI ionic electrolyte were investigated at different temperatures by using cyclic voltammetry, galvanostatic measurements, and electrochemical impedance spectroscopy. The Li/ionic electrolyte/LiMn(2)O(4) cell exhibited satisfactory electrochemical properties with a discharge capacity of 108.2 mA h/g and 91.4% coulombic efficiency in the first cycle under room temperature. At decreased temperature, reversible capacity of the cell could not attain a satisfactory value due to the high internal resistance of the cell and the large activation energy for lithium ion transfer through the electrode/electrolyte interface. Anodic electrolyte oxidation results in the decrease of coulombic efficiency with increasing temperature. Irreversible structural conversion of the spinel LiMn(2)O(4) in the ionic electrolyte, possibly associated with the formation of TMHA intercalated compounds and/or Jahn-Teller distortion, was considered to be responsible for the electrochemical decay with increasing cycles.

Marriage of an Ether-Based Electrolyte with Hard Carbon Anodes Creates Superior Sodium-Ion Batteries with High Mass Loading.

Abstract: Inferior rate performance, insufficient cycle life, and low mass loading have restricted the practical application of hard carbon (HC) anodes in sodium-ion batteries (NIBs). Here, a compatible strategy is developed by matching HC anodes with an ether-based electrolyte. Systematical investigation reveals that good compatibility of the electrode-electrolyte systems forms thinner but a more sustainable solid-electrolyte interphase and delivers a higher ionic conductivity and Na+ ion diffusion coefficient than the commonly used ester-based electrolytes. Therefore, an excellent electrochemical performance is demonstrated with a long cycle life (∼196 mA h/g and 90% capacity retention after 2000 cycles at 1 A/g), a super rate capability (∼51% capacity retention at 10 A/g) at a mass loading of 1.5 mg/cm2, and a high initial Coulombic efficiency of 85.9%. More importantly, a high reversible areal capacity of 4.3 mA h/cm2 can be achieved at an ultrahigh mass loading of 17 mg/cm2, superior to all reported HC anodes. Our findings not only shed light on the design of high-performance battery systems but also promise a commercial transformation from the lab test to mass production of NIBs.

ZnO–ZnS heterostructures with enhanced optical and photocatalytic properties

Abstract: ZnO–ZnS heterostructures were fabricated via using ZnO rods as template in different Na2S aqueous solutions. These heterostructures are 5–6 μm in length and formed by coating ZnO rod with a layer of porous ZnS shell comprising primary crystals about 10 nm in diameter. Subsequently, intact ZnS polycrystalline tubes were obtained by removing the ZnO cores with 25% (wt) ammonia. The as-prepared products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR), and electrochemical impedance spectroscopy (EIS). It was found that the electron transfer between ZnS shell and ZnO core strongly affect the photoluminescence and photocatalytic performances of these heterostructures. The rapid transfer of photo-induced electrons from the ZnS shell to the ZnO core leads to enhanced ultraviolet emission. However, if this correlation was destroyed, then the corresponding heterostructure exhibits improved photocatalytic efficiency due to the reduced volume recombination of the charge carries and the multiple reflection effect. Finally, a model based on band-gap alignment was proposed to elucidate the underlying mechanism of the enhanced UV emission and photocatalytic activity of these unique heterostructures.