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.     

锂离子蓄电池铁基电极材料研究进展

铁基材料具有环保、价格低廉、安全性好、电化学性能较优的特点,已成为近年来的研究热点。对用于锂离子电池正负极的铁基材料的研究现状进行了综述,并对这些材料进行了展望。其中,LiFePO4各项性能优良,将是最有前途的正极材料,随着进一步的研究,其它铁基材料以其价廉的优势也将展示更广阔的应用前景。     

己二腈对高电压锂离子电池性能的影响

用线性扫描伏安(LSV)和交流阻抗谱研究己二腈(ADN)用作电解液添加剂的电化学行为,用X射线能谱(EDS)对电池正负极表面进行元素分析,考察己二腈作为电解液添加剂对以钴酸锂为正极的4.4 V锂离子电池性能的影响。含0.5%己二腈电解液能在正极表面形成腈键参与的吸附结构,并使4.4 V电池的高温存储厚度膨胀率从86.6%下降到13.1%。     

基于磁流变制动器的自供能式汽车线控制动系统的设计与分析

磁流变液是近年来研究的热点,如今汽车线控技术的不断成熟和发展,利用传感器,控制元件,电子元件驾驶员动作转化为电信号,通过电线传递指令来操纵汽车,而不再需要传统的复杂的机械和液压连接装置.针对新型智能流体材料——磁流变液,我们将其应用于汽车线控制动系统中.利用磁流变液的这一特性设计出的制动器,再辅以合理的控制和信息反馈系统,可以实现制动力与地面附着力的快速匹配,甚至可以完成连续精准无脉动的ABS制动过程,从而代替传统液压机械式ABS,有利于实现底盘集成控制,大幅改善车辆制动性能.     

混合超级电容器用锂离子电池材料的进展

综述了锂离子电池正极材料(LiCoO2,LiMn2O4)、负极材料(石墨,Li4Ti5O12,TiO2)和电解质锂盐(LiPF6,LiBF4,LiClO4)用于混合超级电容器领域的研究进展.     

Effect of activated carbon and electrolyte on properties of supercapacitor

Effect of activated carbon and electrolyte on electrochemical properties of organic supercapacitor was investigated. The results show that specific surface area and mesoporosity of activated carbon influence specific capacitance. If specific surface area is larger and mesoporosity is higher, the specific capacitance will become bigger. Specific surface area influences resistance of carbon electrode and consequently influences power property and pore size distribution. If specific surface area is smaller and mesoporosity is higher, the power property will become better. Ash influences leakage current and electrochemical cycling stability. If ash content is lower, the performance will become better. The properties of supercapacitor highly depend on the electrolyte. The compatibility of electrolyte and activated carbon is a determining factor of supercapacitor＇s working voltage. LiPF6/（EC＋EMC＋DMC） is inappropriate for double layer capacitor. MeEt3NPF4/PC has higher specific capacitance than Et4NPF4/PC because methyl＇s electronegativity value is lower than ethyl and MeEt3N^＋ has more positive charges and stronger polarizability than Et4N^＋ when an ethyl is substituted by methyl.     

1-丙烯-1,3-磺酸内酯对高电压锂离子电池的影响

用循环伏安和交流阻抗谱测试研究1-丙烯-1,3-磺酸内酯(PST)用作电解液添加剂的电化学行为,用X射线能谱对电极表面元素进行分析,考察添加剂PST对4.4 V高电压钴酸锂锂离子电池的影响。PST能在电池电极表面形成固体电解质相界面膜,抑制溶剂分子在负极的共嵌和还原分解,改善锂离子电池的循环性能和高温性能,但使低温性能劣化。     

超级电容器水系中性电解液的研究

采用商用超级电容器活性炭,制备了双电层电容器,用循环伏安、交流阻抗和恒流充放电等表征方法研究了活性炭电极在不同中性电解液中的电化学性能。结果表明：活性炭的比电容依KOH、氯化物、硫酸盐、硝酸盐溶液顺序递减,依铵盐、钠盐、钾盐顺序递增;循环性能氯化物和硝酸盐溶液中较差,硫酸盐和KOH溶液中较好,硝酸盐不适合做超级电容器电解质,而（NH4）2SO4和KCl有望成为优良的电解质。     

硝酸氧化热处理对活性炭的影响

通过HNO3氧化和100～700℃不同温度热处理,在活性炭表面产生了不同含量的含氧官能团,用Boehm滴定法测定了官能团的含量和种类,用循环伏安、交流阻抗和恒流充放电方法调查了有机体系中含氧官能团对活性炭电容行为的影响。结果表明：较高的HNO3浓度氧化产生较多的热解产物为CO2的基团,热处理降低含氧官能团特别是羧基等热解产物为CO2的基团的含量。比电容与官能团总数没有关联,但与[酚羟基]＋[羰基]-[羧基]-[内酯基]（[X]表示X的含量）成正相关。氧化提高了比电容,但同时增加了内阻,500℃时热处理的试样获得最高比电容,从原始样的146 F/g增加到163 F/g。     

乙二醇双(丙腈)醚对高电压锂离子电池的影响

用线性扫描伏安(LSV)和电化学阻抗谱(EIS)研究乙二醇双(丙腈)醚(DENE)作为锂离子电池电解液添加剂的电化学行为;对电极表面形貌和元素进行SEM和X射线能谱(EDS)分析;对钴酸锂(LiCoO_2)正极进行XRD分析;考察DENE对4.45 V高电压LiCoO_2锂离子电池的影响。DENE能在高温环境下抑制正极过渡金属溶出、保护负极固体电解质相界面膜,电池60℃存储30 d的厚度膨胀率从76.8%下降到12.3%,以0.50 C在55℃下循环(3.00~4.45 V)200次,容量保持率从58.5%提高到86.3%。