Synthesis of Na_2MnPO_4 F/C with Different Carbon Sources and Their Performances as Cathode for Lithium Ion Battery

采用湿法球磨和原位热解碳包覆相结合的方法,分别以硬脂酸、柠檬酸、聚乙二醇-6000(PEg-6000)、β-环糊精为碳源,制备了不同结构的nA_2MnPO_4f/C复合材料,并研究了它们作为锂离子电池正极材料的电化学行为.通过X射线衍射(Xrd)、扫描电镜(SEM)、bET比表面积测试、恒流充放电等表征手段,比较和分析了产物的结构、形貌及电化学性能.研究结果表明,由不同碳源制备的材料在形貌和颗粒尺寸上有明显差异,进而对它们的电化学性能造成很大影响.影响电化学性能的关键因素在于材料一次颗粒的大小.其中,以柠檬酸为碳源制备的样品呈现出典型的微纳结构和最小的一次颗粒(10-40 nM).并给出最佳的电化学性能:在1.5-4.8 V电压范围内,以5MA·g~(-1)充放电电流获得的首次放电比容量约为80MAH·g~(-1),且循环稳定性良好.Na_2MnPO_4 F/C composites were synthesized by wet ball milling and in situ pyrolytic carbon coating.Stearic acid,citric acid,poly(ethylene glycol) 6000,and β-cyclodextrin were used as carbon sources in the synthesis process.The structures,morphologies,and electrochemical performances of the as-synthesized Na_2MnPO_4 F/C composites were further investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller surface area analysis,and galvanostatic chargedischarge tests.Distinct differences were observed in the morphologies and sizes of the Na_2MnPO_4 F/C particles obtained from different carbon sources,and this significantly affected their electrochemical performances.It was found that the primary particle size of the Na_2MnPO_4 F/C material is a key factor in the electrochemical performance.The sample synthesized using citric acid as the carbon source had a micro-nano structure,with the smallest primary particle size of 10-40 nm,and displayed the best electrochemical properties.It delivered an initial discharge capacity of 80 mAh·g~(-1) under a current density of 5mA·~(-1) in the voltage range of 1.5-4.8V,and displayed good cycling performance.国家自然科学基金(50574063;21021002;21003102); 四川大学青年科学家基金(2011SCU11081); 高等教育博士点科研基金(20120181120103)资助~

大连极紫外相干光源

先进光源的发展在前沿科学研究中发挥的作用越来越重要。近十年来,飞速发展的自由电子激光技术为科学家们提供了探索未知世界、发现新科学规律和实现技术变革的重要工具。建成的大连极紫外(EUV)相干光源的运行波段为50~150nm,单脉冲能量大于100μJ,且可提供10-12 s和10-13 s量级的超快激光脉冲,是我国第一台自由电子激光用户装置,并且是国际上唯一运行在极紫外波段的自由电子激光用户装置,在世界范围内为用户提供具有高峰值亮度和超短脉冲的极紫外激光。大连EUV相干光源是由国家自然科学基金委资助、由中国科学院大连化学物理研究所和上海应用物理研究所共同承担的重大科学仪器研制项目,目标是打造一个以先进极紫外光源为核心、主要用于能源基础科学研究的光子科学平台