Excellent cycling stability of spherical spinel LiMn2O4 by Y2O3 coating for lithium-ion batteries

The Y₂O₃ nano-film is coated on the surface of the spherical spinel LiMn₂O₄ by precipitation method and subsequent heat treatment at 550 °C for 5 h in air. The structure and performance of the bare LiMn₂O₄ and Y₂O₃-coated LiMn₂O₄ are characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis X-ray spectroscopy, galvanostatic charge–discharge, cyclic voltammetry, and impedance spectroscopy. It has been found that the addition of Y₂O₃ does not change the bulk structure of LiMn₂O₄, and the thickness of the Y₂O₃ coating layer is approximate to 3.0 nm. The 1 wt% Y₂O₃-coated LiMn₂O₄ electrode reveals excellent cycling performance with 80.3 % capacity retention after 500 cycles at 1 C at 25 °C. When cycling at elevated temperature 55 °C, the as-prepared sample still shows 76.7 % capacity retention after 500 cycles. These remarkable improvements indicate that thin Y₂O₃ coating on the surface of LiMn₂O₄ is an effective way to improve the electrochemistry performance. Besides, the suppression of Mn dissolution into the electrolyte via the Y₂O₃ coating layer can be accounted for the improved performances.     

Supercapacitive behaviors of the nitrogen-enriched activated mesocarbon microbead in aqueous electrolytes

The activated nitrogen-enriched novel carbons (a-NENCs) have been prepared by direct carbonization of polyaniline/activated mesocarbon microbead composites and further activated by 16 M?HNO₃. The electrochemical performances and supercapacitive behaviors of the a-NENCs in 6 M KOH, 1 M?H₂SO₄, and 0.5 M?K₂SO₄ solutions are evaluated by cyclic voltammetry, galvanostatic charge/discharge, electrochemical impedance spectroscopy, cyclic life, leakage current, and self-discharge measurements. The results demonstrate that the supercapacitors perform definitely supercapacitive behaviors; especially in 6 M KOH electrolyte, the supercapacitor represents much better electrochemical performance with more excellent reversibility, shorter relaxation time of 1.11 s, and nearly ideal polarizability. The maximum specific capacitance of the supercapacitors using a-NENCs as active electrode material is 85.1 F?g^?1 at a rate of 500 mA?g^?1 in 6 M?KOH. These outcomes indicate that the 6 M?KOH aqueous solution is a promising electrolyte for the supercapacitor with a-NENCs as electrode material.     

The effects of preparation temperature on microstructure and electrochemical performance of calcium carbide-derived carbon

Calcium carbide-derived carbons (CCDCs) produced by chlorination of CaC₂ at various temperatures (400–800 °C) possess highly controllable microstructure and porosity, allowing them to serve as excellent electrode materials for the application of supercapacitor. This paper focused on the effect of pore size and specific surface area (SSA) of CCDC on its electrochemical behavior. Microstructure and micropore characteristics of CCDC were characterized by N₂ adsorption/desorption isotherms, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that SSA and average pore size increased with the increase of synthesis temperature from 400 °C to 600 °C, and then decreased when temperature reached to 800 °C. Meanwhile, a correlation between specific capacitance and SSA of micropores (less than 2 nm in diameter) has been studied. It has been found that the supercapacitor using the CCDC prepared at 600 °C as electrode material in 6 M KOH showed the maximum specific capacitance and energy density (53.61 F g^?1 and 7.08 W h kg^?1), outstanding rate capability, lower IR drop and 96 % retention of initial capacity over 5,000 cycles.     

八面沸石在精细有机合成中催化作用的研究 ⅩⅥ.脱铝超稳Y沸石催化苯甲醛与1,2-丙二醇的缩醛化反应

八面沸石在精细有机合成中催化作用的研究＊．脱铝超稳Ｙ沸石催化苯甲醛与１，２┐丙二醇的缩醛化反应袁先友张敏尹笃林＊＊伏再辉李谦和（湖南师范大学精细催化合成研究所，长沙４１００８１）关键词八面沸石，催化，苯甲醛，丙二醇，缩醛化反应缩醛（酮）类香料具有比其...     

超级电容器用碳化物骨架碳/导电聚合物复合材料的研究进展

碳化物骨架碳是近年来开发的一种具有纳米结构的新型多孔碳材料。由于该材料比表面积大、孔径大小可调、表面化学结构稳定以及成本较低等优点,被认为是超级电容器的理想电极材料之一。骨架碳材料与金属氧化物的复合,或者与导电聚合物的复合,能够将双电层电容与法拉第电容结合,既可提高超级电容器的比电容,改变其充放电电压,又可以提高其循环...     

Influence of NiCl2 modification on the electrochemical performance of LiV3O8 cathode for lithium ion batteries

The 5.0, 8.0, and 10.0 wt% NiCl₂-modified LiV₃O₈ materials are successfully prepared and the effects of NiCl₂ modification on the electrochemical performance of LiV₃O₈ cathode have been investigated. The structural and surface morphologic properties of synthesized materials are characterized by X-ray diffraction and scanning electron microscopy. The electrochemical properties are investigated by charge–discharge testing and cyclic voltammetry. It is found that 8.0 wt% NiCl₂-modified LiV₃O₈ shows excellent electrochemical properties. The initial discharge capacity of 8.0 wt% NiCl₂-modified LiV₃O₈ is much higher than that of pristine LiV₃O₈, and can attain 336.7 mAh g^?1 at the current rate of 0.5 C (300 mA g^?1 is assumed to be 1 C rate). Additionally, NiCl₂ modification significantly improves the cyclability of LiV₃O₈. The NiCl₂ modification is shown to be able to suppress the capacity fade of LiV₃O₈ without specific capacity expense by suppressing the characteristic phase transitions during cycling.     

Internal in situ gel polymer electrolytes for high-performance quasi-solid-state lithium ion batteries

Journal of Solid State Electrochemistry - The performance of solid-state lithium ion battery mainly depends on the performance of the electrolyte and the interface between the electrolyte and the...     

沉积钴镀层的粘接式氢氧化镍电极电化学性能研究

研究了在碱性可充电电池正极活性物质－球型氢氧化镍粒子表面化学镀钴后氢氧化镍电极的性能。通过比较充放电曲线和循环伏安试验结果,讨论了电极的放电容量、活性物质利用率和Ｎｉ（ＯＨ）２／ＭｉＯＯＨ氧化还原可逆性。实验还发现镀钴后的氢氧化镍电极有更好的充放电性能和优良的电极特性。测定了化学镀钴前后氢氧化镍电极的交流阻抗,表明镀钴后氢氧化镍的基体之间的有较低接触电阻。此外,本文还对钴镀层改进氢氧化镍性能的机理