【作者】 李泽胜；

【导师】 王红强； 李庆余；

【作者基本信息】 广西师范大学 ， 物理化学， 2010， 硕士

【摘要】 迫于石油危机和环境保护的压力,各国政府都在大力发展新能源汽车产业。而高能量、高功率储能装置是新能源汽车最关键的技术之一。超级电容器(电化学电容器)是一种很有前景的储能器件,具有充放电性能优异,脉冲功率性能良好、使用寿命长、价格适中和环境友好等优势,在新能源汽车和其他行业用储能装置中占有一席之地。基于目前超级电容器用两大类电极材料――炭材料和金属氧化物各自的优势,本文将理论比容量高、价格适中、资源丰富、环境友好的金属氧化物——二氧化锰(MnO2)和导电性好、比表面积大、球形度良好的中间相碳微球基球形活性炭——活性中间相碳微球(AMCMB)设计成为新型的纳米金属氧化物/球形活性炭(MnO2 /AMCMB)复合材料,研究其制备方法、微观结构和电化学性能,以获得更高性能的超级电容器电极材料,推动高能量、高功率储能装置技术向前发展。第一,首次选取具有不同粒径规格的中间相碳微球MCMB作为混合前躯体,应用KOH化学活化法成功制备了粒度分布较广、球形度良好、比表面积和中孔孔容含量高的活性中间相碳微球AMCMB;并对比研究了其在30% KOH水系电解液和1 mol/L LiPF6/(DMC+EC)有机系电解液中的电容性能。结果表明,所制备的AMCMB粒径在5-40μm之间,大小分布相对均匀,比表面积达到3290.4m2 g-1,具有5-20nm的中孔结构,中孔孔容含量高达64.5%;AMCMB电极在1 mol/L LiPF6/(DMC+EC)有机电解液中的能量密度高达68.13 Wh/kg,是30% KOH水系电解液的8倍。为制备性能优异的MnO2 /AMCMB高能量高功率复合电极材料奠定了基础。第二,分别采用常温液相氧化还原化学反应法、常温液相化学共沉淀法和低温固相热分解法,成功制备了三种国内外尚未报道的,具有不同形貌的纳米MnO2与球形活性炭AMCMB的新型复合物:MnO2纳米粒/AMCMB(GMAM)复合物,MnO2纳米片/AMCMB(FMAM)复合物和MnO2纳米针/AMCMB(NMAM)复合物。以1 mol/L LiPF6/(DMC+EC)有机溶液为电解液,以MnO2/AMCMB复合物为电极,组装成对称超级电容器,研究了不同形貌的纳米MnO2对MnO2/AMCMB复合物的电容性能的影响。研究结果表明,所制备的GMAM复合物的MnO2粒径为100-200nm,FMAM复合物的MnO2粒径为200×80×20nm,NMAM复合物的MnO2粒径为(2-3)μm×(20-30)nm,其中NMAM的一维MnO2的纳米尺度最小,纳米化程度最高;在保持功率密度高的特性的同时,GMAM、FMAM和NMAM复合物都具有较高的能量密度,分别为98.2 Wh kg-1、106.3 Wh kg-1和127.4 Wh kg-1;三者中NMAM复合物电极具有更加优异的功率特性和更高的库仑效率,所制备的超级电容器具有替代传统二次电池的潜力。而且,使用常温液相氧化还原化学反应法、常温液相化学共沉淀法和低温固相热分解法工艺都简单易行,因此GMAM、FMAM和NMAM等复合电极材料极具产业化前景。第三,通过改变MCMB活化条件,在无需外添加商品CNT的条件下,成功制备了AMCMB-CNT新型混合物,并进一步制备了MnO2/(AMCMB-CNT)新型复合物。同时,以该复合物为电极,组装成对称超级电容器研究了其在1 mol/L LiPF6/(DMC+EC)有机电解液中的电容性能。研究结果表明,所制备的MnO2/(AMCMB-CNT)复合物属于二重复合物,即MnO2/AMCMB和MnO2/CNT二重复合物。该复合物中AMCMB上的MnO2粒度分布较广,约在40-160 nm之间,峰值为110nm;而CNT上MnO2粒度分布相对较窄,大多数集中在40-50 nm,且粒径比前者小;MnO2/(AMCMB-CNT)二重复合物的能量密度为113.7Wh kg-1,相比MnO2/AMCMB(GMAM)一重复合物电容器,该二重复合物具有更加优异的电化学性能。第四,通过水热合成法成功制备了极为有趣同时具有粒度分布较广和球形度良好的MnO2纳米丝球,并分别以MnO2纳米丝球和球形AMCMB为正负极,组装成不对称电容器,研究了其在1 mol/L的Et4NBF4/AN有机电解液中的电容性能。研究结果表明,所制备的MnO2纳米丝球呈现良好的球状分布,直径在5~20μm,大小分布相对均匀。MnO2球为丝状球体,单丝直径约80nm,长度在3~5μm之间;而且球体并非实心球,而是由无数纳米丝聚集而成的松散球体,其比表面积高达352 m2 g-1; AMCMB||MnO2混合超级电容器具有高达128 Wh kg-1能量密度,该数值已经相当接近锂离子电池的能量密度水平,1200次充放电循环后该混合超级电容器容量保持率在86%以上,而且功率性能十分优异。总体研究结果表明,将具有良好纳米结构的MnO2与具有良好球形度的AMCMB相结合,充分利用球形活性炭和纳米金属氧化物各自的优点,以及有机电解液超级电容器高工作电压的优势,达到了同时提高超级电容器的工作电压和能量密度,并保持良好的功率特性的目的,实现了预定的研究目标,为其工业应用奠定了理论和实验基础。更多还原

【Abstract】 Forced by the pressure of the oil crisis and environmental protection, governments all over the world are seeking to develop new energy automotive industry. The high-energy, high power energy storage device has become one of the most critical technologies in this industry. Supercapacitor (electrochemical capacitor) is a promising energy storage device, with features of excellent charge and discharge performance, good pulsed power performance, long life, affordable and environmentally friendly, which is expected to play the major role in the new energy automotive industry and other industry as energy devices.Based on the advantages of current two categories of supercapacitor electrode material-- carbon and metal oxides, in this article, manganese dioxide (MnO2), one of the affordable, abundant resources, environmentally friendly and high theoretical specific capacity metal oxide, and activated mesocarbon microbead (AMCMB) with good conductivity and large specific surface area and good sphericity, were designed into a new type of nano-metal oxide/ spherical activated carbon (MnO2/AMCMB) composite materials. The preparation method, microstructure and electrochemical properties of composite materials were demonstrated, in order to obtain high performance supercapacitor electrode materials, and promote the development of high-energy, high-power energy storage technology.Firstly, for the first time, a high surface area activated mesocarbon microbead AMCMB with wide size distribution and good sphericity were successfully prepared, by selecting MCMB with different particle sizes as the mixed precursor, using KOH chemical activation. In addition, a comparative performance study was conducted in symmetrical supercapacitor for the AMCMB electrodes in 30% KOH water electrolyte and 1 mol/L LiPF6/(DMC+EC) organic electrolyte. The as-prepared AMCMB has good spherical degree and diameter between 5-40μm, the particle size distribution is relatively uniform, the specific surface is 3290.4 m2g-1, with a 5-20nm of the pore structure as well as a high mesopore content of 64.5%. The energy density of as-prepared AMCMB electrode in 1 mol/L LiPF6/(DMC+EC) organic electrolyte is up to 68.13 Wh/kg, which is 8 times as much as that in 30% KOH electrolyte. This is expected to lay the foundation for excellent performance of MnO2/AMCMB high-energy electrode materials.Secondly, three preparation methods with industrial prospects--room-temperature liquid phase redox method, liquid chemical precipitation method and low-temperature solid phase synthesis method, were applied to prepare three novel spherical MnO2/AMCMB composites in different morphologies: granular MnO2/AMCMB(GMAM) composite, flake-like MnO2/AMCMB(FMAM) and needle-like MnO2/AMCMB(NMAM) composite. The effects on capacitive performance of MnO2 morphologies were studied in 1 mol/L LiPF6/(DMC+EC) organic electrolyte in symmetrical supercapacitor. The as-prepared GMAM composite has MnO2 particle size of 100-200nm, FMAM composite has MnO2 particle size of 200×80×20nm, NMAM composite has MnO2 particle size of (2-3)μm×(20-30) nm, in which NMAM one-dimensional MnO2 has the smallest nano-scale and the highest nano-level degree. For the as-prepared MnO2/AMCMB composite electrode, the energy density of GMAM, FMAM, and NMAM are 98.2 Wh kg-1, 106.3 Wh kg-1 and 127.4 Wh kg-1, in which the NMAM composite electrode has more excellent power characteristics and higher coulomb efficiency. Supercapacitors prepared with these composite electrodes are of highly potential alternative to traditional secondary battery. Moreover, the three preparation methods used are simple and easy, so GMAM, FMAM, and NMAM composite electrode materials have great potential for industrialization.Thirdly, we successfully prepared a novel AMCMB-CNT compound without adding any CNT product by changing the activation conditions of AMCMB, and further prepared a novel MnO2/(AMCMB-CNT) composite. At the same time, the capacitive performance of the MnO2/(AMCMB-CNT) composite electrode was studied in symmetrical supercapacitor assembled studied in 1 mol/L LiPF6/(DMC + EC) organic electrolyte. The as-prepared MnO2/(AMCMB-CNT) composite is a dual-composite, that is the MnO2/AMCMB and MnO2/CNT double composites. The MnO2 on AMCMB has a wide particle size distribution between 40-160 nm with peak at 110nm. The MnO2 on CNT has a narrow particle size distribution, mostly lied in 40-50 nm that is smaller than the former one. The as-prepared MnO2/(AMCMB-CNT) dual-composite has energy density of 113.7 Wh kg-1, which demonstrated more excellent electrochemical performance compared to MnO2/AMCMB(GMAM).Fourthly, an interesting MnO2 nanowire-sphere with wide size distribution and good spherical morphology has been prepared by a hydrothermal method. A novel non-aqueous hybrid supercapacitor was fabricated from two spherical materials of spherical activated mesocarbon microbead (AMCMB) and MnO2 nanowire-sphere as the negative and positive electrodes, respectively, using 1 M Et4NBF4 in acetonitrile (AN) as electrolytes. The as-prepared MnO2 nanowire-sphere showed good spherical distribution of diameter 5~20μm and the size distribution is relatively uniform. The MnO2 nanowire-sphere is the filamentous sphere rather than solid sphere, made up of nanowires with diameter of about 80nm and the length between 3~5μm, the specific surface area of the MnO2 nanowire-sphere is up to 352 m2 g-1. The as-prepared AMCMB||MnO2 hybrid supercapacitor has an energy density up to 128 Wh kg-1, which is quite close to the energy density of lithium-ion battery. After 1200 cycles of charge-decharge, the capacity of the hybrid supercapacitor maintain a rate of >86%, and very excellent power performance.Overall results showed that, the combination of the good-nanostructured MnO2 and AMCMB with high spherical degree, the full use of advantages for spherical activated carbon and nano-metal oxides, and the advantage of the high voltage of organic electrolyte supercapacitor, contributed the objective of improving the voltage and energy density of superapacitors, while maintaining a good power characteristic. In short, this study has achieved the predetermined target and laid the theoretical and experimental foundation for the industrial application of MnO2/AMCMB electrode material.更多还原