不同形貌磷化钴超级电容材料的制备与性能研究

利用水热合成与低温磷化法,通过改变原料与水热温度进行形貌控制,分别制备出磷化钴(CoP)纳米片与纳米花形貌的材料。结果表明,CoP纳米片与纳米花的最佳制备温度均为120℃。实验发现,磷化钴形貌对其电化学特性有着显著影响。对纳米片与纳米花形貌的磷化钴样品进行超级电容性能测试发现,在电流密度为1 A/g时测得的比电容分别为453.2 F/g与584.4 F/g。纳米花形貌的CoP不仅具有更高的比电容,其倍率稳定性也更加优异于纳米片形貌的CoP。在电流密度增加到20 A/g时,纳米花形貌的CoP的比电容仍能保留59.6%,达到347.8 F/g,表现出很好的应用潜力。     

聚苯胺纳米纤维的界面聚合法合成及电化学电容行为

利用盐酸和四氯化碳的水／油两相界面，通过界面聚合法合成具有良好纳米纤维结构的聚苯胺，用这种聚苯胺纳米纤维为活性物质制备电极，以1mol／LH2SO4水溶液为电解液组装超级电容器，通过恒电流充放电、循环伏安、交流阻抗等技术研究其电化学电容行为。研究结果表明，合成的聚苯胺的直径为50～100nm，长度为500nm至几微米不等，且纤维之间相互交织缠绕，形成网状形貌；聚苯胺纳米纤维电极材料的功率特性与循环性能优于用传统化学氧化法合成的颗粒状聚苯胺材料的性能，在5mA放电电流下，其比电容可达317F／g，20mA放电电流下比电容仍维持300F／g左右，500次循环容量衰减在4％以内。     

三维多级纳米结构CoNi2S4的构筑及其超级电容性能

针对超级电容器电极材料比电容量和倍率性能低的问题,提出构筑三维(3D)多级纳米结构电极材料的思路,以提供更多的电化学反应活性位点。以过渡双金属CoNi₂S₄为研究对象,通过引入结构导向剂,在两步水热法条件下,自组装形成具有3D多级纳米结构的电极材料。该结构由无数纳米纤维从内芯到外表面相互交织而成,构成稳定的直径约为2μm的纳米球。该3D多级纳米结构的比表面积为22.9 m²/g,且分布了孔径为5～20 nm的纳米孔。作为超级电容器电极材料,CoNi₂S₄材料表现出1 299.4 F/g的比电容,即使在50 A/g的超高电流密度下,该电极材料的比电容仍可保留23.8%,显示出优良的比电容量和倍率性能。     

纳米Nix Co1-xO的制备及超级电容的性能

以NiSO4.6H2O和Co(NO3)2.6H2O为原料,采用共沉淀-焙烧相结合的方法进行超级电容器用电极材料NixCo1-xO的制备研究.结合恒流充放电、XRD和SEM测试手段,考察了Ni/Co物质的量比、沉淀剂、氨水添加剂对合成产物物理及电化学性能的影响.实验结果表明:n(Ni)∶n(Co)=9∶1,采用NaOH作为沉淀剂,并且适量添加NH3.H2O的条件下,获得纳米级NixCo1-xO,该材料的综合电化学性能最佳,200周期的比电容达到39.37 F/g,1 000次充放电后电容保持率在90%以上.     

微波活化甘蔗渣合成活性炭及其电化学电容特性

以甘蔗渣为原料,ZnCl2为活化剂,分别采用微波加热活化和管式炉加热活化制备了一系列活性炭材料,并研究了微波活化法制备的活性炭在水或离子液体电解液体系中的电容特性.氮气吸附测试表明:活化剂的浓度与活性炭的孔结构密切相关,加热方式对孔径结构的影响不大,但微波活化法在加热效率和均匀性方面具有明显的优势.当活化剂的浓度从20wt%增大到60wt%时,活性炭的平均孔径从2.5nm逐渐增大到7.0nm.电化学测试表明:在离子液体中炭材料的电容性能与其孔径大小密切相关,孔径尺寸越大,其电容性能越好.离子液体电容器能提供远高于水相电容器的能量密度.AC60在功率密度为2.5kW/kg时,仍能提供9.2Wh/kg的能量密度.     

聚乙酰苯胺/氧化石墨烯纳米复合材料制备及其超级电容性能

采用改进的Hummers方法制备氧化石墨,在乙醇溶液中超声分散120 min得到氧化石墨烯悬浮液。采用滴涂法在玻碳电极表面得到氧化石墨烯薄膜,通过电化学技术在氧化石墨烯薄膜上沉积得到聚乙酰苯胺纳米线,成功制备了聚乙酰苯胺/氧化石墨烯纳米复合材料(PAANI/GO)。利用扫描电镜、循环伏安法和恒电流充放电测试技术对合成材料的形貌和充放电性能进行表征和测试。结果表明,直径为80 nm的聚乙酰苯胺纳米线均匀分散在氧化石墨烯表面,制备的复合材料在1 mol/L高氯酸溶液中,当循环伏安扫速为10 m V/s时,可以获得706 F/g的比电容,PAANI的比电容为285 F/g。聚乙酰苯胺/氧化石墨烯纳米复合材料具有优异的充放电稳定性,当恒电流为1A/g时,循环充放电1 000次比电容是初始值的90%。     

超级电容串联均压研究

超级电容器因其具有比功率高、充电速度快以及循环使用寿命长等特点,成为近年来重要的储能设备之一。超级电容器串联使用时,单体状态的一致性问题是制约其使用寿命和故障率高的主要因素。对超级电容组进行均衡管理具有十分重要的意义,本文针对超级电容器在串联应用中存在的问题,介绍了几种均压控制的方法,实现了串联超级电容器组的电压均衡,使超级电容器组延长有效使用寿命,提高超级电容器的工作可靠性。     

聚苯胺/碳纳米纤维超级电容器电极材料的制备及其性能

采用化学氧化原位聚合法制备聚苯胺纳米棒(PANI)、PANI和氮掺杂碳纳米纤维(NCNFs)的复合材料(PANI/NCNFs)。扫描电镜(SEM)结果表明, PANI纳米棒均匀生长在NCNFs的表面,制备的复合材料直径约为150～200 nm。恒流充放电结果表明,当放电电流密度为0.2 A/g时, PANI/NCNFs-1、PANI/NCNFs-2和PANI/NCNFs-3(苯胺浓度分别为0.256、0.337、0.160 mol/L制备)可以获得877、693和563 F/g的比电容。PANI/NCNFs复合材料具有优异的比电容和倍率性能,该材料在电化学储能器件领域具有广阔的应用前景。     

基于飞渡电容的超级电容组动态均衡控制算法

超级电容器具有充电速度快、比功率高、循环寿命长、低温特性好等优点,其缺点是能量密度比化学电池低.这种特点使得超级电容器用于城市短距离公交车比较适合.但是由于单体之间的差异,在经过多个循环的深度充/放电后,单体电容之间的电压差将会加大,这将加速性能较弱的单体电容器的老化.为了保护超级电容器,提高其有限容量的利用率,研究了基于飞渡电容的超级电容组动态均衡算法.首次将飞渡电容式动态均衡管理系统用于超级电容公交车,该系统可以工作于动态和静态两种模式下,给出了电容组处于充、放电和静置三种状态下的均衡控制算法及其实验结果.实际运行结果表明,系统的均衡精度满足超级电容组运行要求.     

Preparation of activated carbons from mesophase pitch and their electrochemical properties

The influences of molar ratio of KOH to C and activated temperature on the pore structure and electrochemical property of porous activated carbon from mesophase pitch activated by KOH were investigated. The surface areas and the pore structures of activated carbons were analyzed by nitrogen adsorption, and the electrochemical properties of the activated carbons were studied using two-electrode capacitors in organic electrolyte. The results indicate that the maximum surface area of 3 190 m2/g is obtained at molar ratio of KOH to C of 5:1, the maximum specific capacitance of 122 F/g is attained at molar ratio of KOH to C of 4:1, and 800 ℃ is the proper temperature to obtain the maximum surface area and capacitance.     

82B高碳钢热变形行为研究

采用单道次热压缩实验方法,在Thermomaster-Z型热模拟试验机上模拟高碳钢高速线材热轧变形过程动态再结晶行为,测定82B高碳钢在变形温度为800～1 100℃、变形速率为0.1～50 s-1、变形程度为0～0.60条件下的真应力-应变曲线,利用曲线特征值确定高应变速率下的变形激活能,根据实验结果分析动态再结晶变形条件,建立动态再结晶状态图。     

Preparation and electrochemical characterization of activated carbons by chemical-physical activation

A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m²/g and 0.308 4 cm³/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance. Foundation item: Project(2007BAE12B01) supported by the National Key Technology Research and Development Program of China     

Electrochemical behavior of CoCl2 in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

The electrochemical behavior of CoCl2 in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) was investigated by cyclic voltammetry. The cyclic voltammograms were obtained from electrochemical measurement under different temperatures, and the reversible behavior for Co2 /Co3 redox couple on glassy carbon electrode in [bmim]PF6 was confirmed by the characteristic of the peak currents. The diffusion coefficients (about 10-11m2/s) of Co2 in [bmim]PF6 under different temperatures were evaluated from the dependence of the peak current density on the potential scan rates in cyclic voltammograms. It is found that the diffusion coefficient increases with increasing temperature. Diffusion activation energy of Co2 in [bmim]PF6 is also calculated to be 23.4kJ/mol according to the relationship between diffusion coefficient and temperature.     

Influence of nitrogen hetero-substitution on the electrochemical performance of coal-based activated carbons measured in non-aqueous electrolyte

Nitrogen-containing carbons were prepared by modification of activated carbons. The modified carbons were used as electrode materials with improved electrochemical performance. Precursor anthracite was activated by KOH (KOH: anthracite= 1:1), modified by melamine or urea and then treated at 1173 K to obtain the modified carbons. The porous structure, the chemical composition and the electrochemical characteristics of the carbons were investigated by nitrogen sorption, XPS and electrochemical methods respectively. Electrochemical experiments were performed in an organic electrolytic solution of 1 M (C2H5)4NBF4/PC.The samples modified by the different methods showed differences in chemical composition that introduced varying degrees of electrochemical performance enhancement. The presence of nitrogen enhanced the electron donor properties and the surface wettability of the activated carbons: this ensured a sufficient utilization of the exposed surface for charge storage.     

孔结构对煤基活性炭电化学性能的影响

以煤为前驱体,KOH为活化剂制备系列煤基活性炭电极材料.采用N_2吸附法及电化学测试对活性炭的孔结构和电化学性能进行了表征,研究了孔结构对活性炭电极材料的电化学性能的影响.结果表明,采用化学活化法可制备出比表面积1 048～3 581 m~2/g、中孔率7%～91%的活性炭电极材料.在3 mol/L KOH无机电解液体系及1 mol/L(C_2H_5)_4NBF_4/碳酸丙烯酯(PC)有机电解液体系中,活性炭电极材料的比电容分别达到322 F/g,190 F/g.2～3 nm的中孔对电解质离子在电极材料中的扩散有着重要作用,可以有效降低电解液的扩散阻力,提高电极材料比表面积的利用率,从而增强电容器的电化学性能.     

Comparison of capacitive behavior of activated carbons with different pore structures in aqueous and nonaqueous systems

The pore structures of two activated carbons from sawdust with KOH activation and coconut-shell with steam activation for supercapacitor were analyzed by N2 adsorption method. The electrochemical properties of both activated carbons in 6 mol/L KOH solution and 1 mol/L EtgNPF4/PC were compared, and the effect of pore structure on the capacitance was investigated by cyclic voltammetry, AC impedance and charge-discharge measurements. The results indicate that the capacitance mainly depends on effective surface area, but the power property mainly depends on mesoporosity. At low specific current （1 A/g）, the maximum specific Capacitances of 276.3 F/g in aqueous system and 123.9 F/g in nonaqueous system can be obtained from sawdust activated carbon with a larger surface area of 1 808 m^2/g, butat a high specific current, the specific capacitance of coconut-shell activated carbon with a higher mesoporosity of 75.1% is more excellent. Activated carbon by KOH activation is fitter for aqueous system and that by steam activation is fitter for nonaqueous system.     

Hydrogen absorption behavior of TA15 alloy

The hydrogen absorption kinetics of TA15 titanium alloy at 973-1123 K was studied using a tube-type hydrogen treatment furnace. The hydrogen absorption kinetic curves obtained were analyzed according to a series of mechanism equations to reveal the kinetic parameters and mechanism of the hydrogen absorption process. The results show that both the hydrogen absorption rate and the equilibrium hydrogen pressure increase and the time to reach equilibrium is shortened with increasing temperature. It is found tha...     

乙酰二茂铁的电化学行为及动力学性质研究

在0.2m ol·L-1N a2SO水溶液中,研究了乙酰二茂铁(A cetylferrocene,A F c)在玻碳电极上的循环伏安行4为,同时用电位阶跃计时库仑法(C hronocoulom etry,C C)和电位阶跃计时电流法(C hronoam perom etry,C A)测定了A F c的扩散系数D和电极反应速率常数K.实验结果表明:在所选定的支持电解质中,A F c表现出良好的电化f学氧化还原准可逆性,氧化还原峰电位差ΔE≈70m V,峰电流比Ipa/Ipc≈1.1;A Fc在玻碳电极上的电化学氧化p还原反应为一无质子参与的单电子转移过程,并且为受扩散传质所控制的电化学准可逆过程,其D和K分别f为2.04×10-5cm/s和2.88×10-3/s.2