Synthesis of carbon nanoparticle ionic liquid hybrids and the application in supercapacitor

以1-甲基-3-乙基咪唑四氟硼酸离子液体和果糖为原料,微波作用下一步制得一种新型碳点离子液体复合物,用此复合物代替部分导电剂和粘结剂制成新型炭基超级电容器,并与传统的炭基超级电容器进行了比较研究.结果表明:所制复合物中有大量直径小于4nm的碳纳米粒子,70℃时电导率达到13.26×10-3S·cm-1,所制超级电容器充放电效率由传统炭基超级电容器的89.1％提高到97.3％,比电容由115.7 F·g-1提高到251.1 F·g-1,内阻由1.95 Ω降低为1.23 Ω,且循环性能显著提高.     

[Pmim][SCN]离子液体电解质的合成和性质研究

采用两步法合成了1-戊基-3-甲基咪唑硫氰酸盐([Pmim][SCN])新型离子液体电解质,测定了该电解质的物理化学性质。并用这种新型离子液体电解质与活性炭电极组装成模拟超级电容器,研究了所制超级电容器的电化学性能。结果表明:所制离子液体电导率较高,密度和表面张力都随温度升高而减小,模拟超级电容器的工作电压可达4.0 V,比电容可达421.05 F/cm3,充放电效率为96.3%,且该离子液体具有很好的与常见有机溶剂互溶的能力,具有成为超级电容器用电解质的应用潜力。     

1-丁基-3-甲基咪唑离子液体在超级电容器中的应用

两步法合成了1-丁基-3-甲基咪唑三氟乙酸盐(BMI-CF3CO2)、1-丁基-3-甲基咪唑六氟磷酸盐(BMI-PF6)及1-丁基-3-甲基咪唑四氟硼酸盐(BMI-BF4)三种离子液体,研究了这三种离子液体所制超级电容器的电化学性能。结果表明:BMI-CF3CO2在电化学稳定性及充放电效率等方面优于BMI-PF6和BMI-BF4;BMI-CF3CO2离子液体电解液电势窗口达到4.0V,所制备的超级电容器在3.6V电压下循环寿命超过1000次。     

功能性离子液体[C_nmim][SCN]的超电容性质研究

通过两步法合成了三种新型"绿色"功能性离子液体电解质(液)1-烷基-3-甲基咪唑硫氰酸盐([C3-5mim][SCN]),测定了离子液体的特征红外光谱和电导率。以离子液体作为超级电容器的工作电解液,采用循环伏安、交流阻抗、恒流充放电等方法研究了其电化学性能。结果表明:咪唑阳离子上具有较短烷基侧链的离子液体表现出更好的电化学稳定性及综合性能,具有成为新一代高性能超级电容器电解质(液)的应用潜力。     

超级电容器混合型电解液(EMIES+LiClO_4)的热力学和电化学性质

介绍了一种新型离子液体混合电解质(液),由离子液体1-乙基-3-甲基咪唑硫酸乙酯盐(EMIES)与高氯酸锂盐按照不同配比混合制备而成。测定了这种新型混合电解质(EMIES+Li Cl O_4)的一系列热力学性质,如:电导率、密度、表面张力等,发现其黏度和电导率随温度的变化呈相反趋势。锂盐的加入带来了混合电解液电导率的非线性变化,而当其中高氯酸盐的摩尔比为0.05时,电解液具有最佳电导率和黏度。进而,用此浓度的混合电解液与活性炭电极组装成超级电容器,采用交流阻抗、恒流充放电及循环伏安等测试手段对其性能进行测试与研究。结果表明:这种离子液体混合电解液电化学窗口达到5.1 V,单电极比电容为458.65 F·cm~(-3),充放电测试1000次以后,比电容只下降了1.9%。表明该混合电解液具有良好的电容特性、可逆性及循环特性,具备成为高性能超级电容器电解液的应用潜力。     

三氟乙酸离子液体/四氟硼酸螺环季铵盐混合电解液的超级电容性质研究

采用两步法合成功能化离子液体1-甲基-3-丁基咪唑三氟乙酸盐离子液体([Bmim][CF_3CO_2]),并将其与有机电解质四氟硼酸螺环季铵盐([(C_4H_8)_2N][BF_4])组成不同浓度配比的新型混合电解液。采用活性炭为电极,组装成超级电容器,通过循环伏安、恒流充放电、交流阻抗等方法对其电化学性能进行了研究。结果显示:混合电解液的浓度为2.06 mol/L时的性能最优,这种新型的混合电解液25℃时电导率为3.99×10~(–3) S/cm,电化学窗口可达2.7 V,内阻0.96?,经过1 000次充、放电循环后仍可保留98%的初始比电容,说明该混合电解液具有突出的电化学性能和巨大的市场应用潜力。     

电子百科

高能镍碳超级电容器高能镍碳超级电容器是一种军民两用的新型动力电源。可解决电动汽车动力问题,还可在水面舰艇、潜艇、新型飞机、导弹以及航天领域中应用。这种新型结构的高能镍碳超级电容器由中国工程院周国泰院士领衔的科研团队历时3年刻苦攻关成功开发的。经检测试用显示,超级电容器具有能量密度大、功率密度高、充放电效率高、高低温性能好、循环寿命长、安全环保、性价比高等诸多特点,有效解决了国内电动汽车电源技术瓶颈问题。     

双电层电容器中单/双面涂覆电极的电化学性能比较

以KOH为活化剂,采用微波加热石油焦一步法制备了微孔活性炭。采用循环伏安和恒流放电法研究了双电层电容器中单面和双面涂覆的活性炭电极电化学性能。活性炭的亚甲基蓝吸附值为247.8mg·g–1,N2吸/脱附结果表明,活性炭比表面积为1037m2·g–1,微孔孔容为0.54m3·g–1。结果表明,1000次循环后,双面涂覆电极的比容、比容保持率和两电极电容器的能量密度保持率分别为227.3F·g–1、96.6%和97.4%均高于单面涂覆电极;而双面涂覆电极的内阻仅为0.42Ω,小于单面涂覆电极的内阻。     

新型LiFePO_4/AC混合超级电容器的制备和性能研究

以橄榄石型磷酸亚铁锂(LiFePO4)为正极,活性炭(AC)为负极,制备了LiFePO4/AC混合超级电容器。通过充放电、倍率和漏电流测试,系统研究了所制混合超级电容器的电化学性能。结果表明,在正负极活性物质质量比为0.8∶1.0的条件下,混合超级电容器综合性能最佳:比容量为25.38 mAh.g–1,比能量为3.21 Wh.kg–1,分别是活性炭超级电容器的2.83倍和2.17倍,且在大倍率充放电下循环稳定性好、漏电流小,在1600 s后漏电流为0.25 mA。     

熔盐处理对MnO2电化学性能的影响

采用固相法制备了MnO2,用KCl-LiCl熔盐体系对样品进行处理后,MnO2的结晶程度增加。XRD测试表明,产物为α-MnO2与γ-MnO2的混合晶相,循环伏安测试表明熔盐处理后材料具有典型的超级电容特性,其等效串联电阻(RESR)由0.26Ω减小到0.25Ω,电极电阻(RE)由0.57Ω减小到0.37Ω,单电极放电比容量由100.94F·g–1提高了28.34%达129.54F·g–1。样品在恒电流充放电循环100次后,比容量衰减不大,充放电效率接近100%。     

用于超电容器的高性能活性炭研究

运用化学活化法制备了超电容器用高比表面积活性炭。利用碘吸附、亚甲蓝吸附和BET测试,对样品的孔隙性进行了分析。以制备的活性炭为超电容器电极材料,利用循环伏安和恒流充放电测试其电容特性。结果表明,实验研制的活性炭的比表面积为173m2·g–1,平均孔径为2.36nm,绝大部分孔径都在5nm以内;在10–2A·cm–2的电流密度下活性炭的比容达180F·g–1,基于研制的活性炭的超电容器具有良好的功率特性。     

溶剂对离子液体电化学电容器电解液的影响

研究了有机溶剂[乙腈(AN)、丙酮(Acet)]对离子液体1-乙基-3-甲基咪唑四氟硼酸盐[(EMIm)BF4]电导率和电化学性能的影响。混合电解液体系的电导率在离子液体与有机溶剂的摩尔比为4∶6时达最大值。循环伏安和恒流充放电测试结果表明,添加有机溶剂在很大程度上改善了电容器的电容特性。电容器的比电容在(EMIm)BF4与AN或Acet的摩尔比为4∶6时达最大值,分别为233,173F/g。     

A High‐Performance Graphene Oxide‐Doped Ion Gel as Gel Polymer Electrolyte for All‐Solid‐State Supercapacitor Applications

A high‐performance graphene oxide (GO)‐doped ion gel (P(VDF‐HFP)‐EMIMBF₄‐GO gel) is prepared by exploiting copolymer (poly(vinylidene fluoride‐hexafluoro propylene), P(VDF‐HFP)) as the polymer matrix, ionic liquid (1‐ethyl‐3‐methylimidazolium tetrafluoroborate, EMIMBF₄) as the supporting electrolyte, and GO as the ionic conducting promoter. This GO‐doped ion gel demonstrates significantly improved ionic conductivity compared with that of pure ion gel without the addition of GO, due to the homogeneously distributed GO as a 3D network throughout the GO‐doped ion gel by acting like a ion “highway” to facilitate the ion transport. With the incorporation of only a small amount of GO (1 wt%) in ion gel, there has been a dramatic improvement in ionic conductivity of about 260% compared with that of pure ion gel. In addition, the all‐solid‐state supercapacitor is fabricated and measured at room temperature using the GO‐doped ion gel as gel polymer electrolyte, which demonstrates more superior electrochemical performance than the all‐solid‐state supercapacitor with pure ion gel and the conventional supercapacitor with neat EMIMBF₄, in the aspect of smaller internal resistance, higher capacitance performance, and better cycle stability. These excellent performances are due to the high ionic conductivity, excellent compatibility with carbon electrodes, and long‐term stability of the GO‐doped ion gel.     

Material development for dye solar modules: results from an integrated approach

In this paper, we report on the outcome of a German network project conducted with 12 partners from universities and research institutes on the material development of dye solar cells (DSC). We give an overview in the field and evaluate the concept of monolithic DSC further with respect to upscaling and producibility on glass substrates. We have developed a manufacturing process for monolithic DSC modules which is entirely based on screen printing. Similar to our previous experience gained in the sealing of standard DSC, the encapsulation of the modules is achieved in a fusing step by soldering of glass frit layers. For use in monolithic DSC, a platinum free, conductive counter electrode layer, showing a charge transfer resistance of R_CT < 1·5 Ω cm², has been realized by firing a graphite/carbon black composite under an inert atmosphere. Glass frit sealed monolithic test cells have been prepared using this platinum‐free material. A solar efficiency of 6% on a 2·0 cm² active cell area has been achieved in this case. Various types of non‐volatile imidazolium‐based binary ionic liquid electrolytes have been synthesized and optimized with respect to diffusion‐limited currents and charge transfer resistances in DSC. In addition, quasi‐solid‐state electrolytes have been successfully tested by applying inorganic (SiO₂) physical gelators. For the use in semi‐transparent DSC modules, a polyol process has been developed which resulted in the preparation of screen printed, transparent catalytic platinum layers showing an extremely low charge transfer resistance (0·25 Ω cm²). Copyright © 2008 John Wiley & Sons, Ltd.     

Superior Micro‐Supercapacitors Based on Graphene Quantum Dots

Graphene quantum dots (GQDs) have attracted tremendous research interest due to the unique properties associated with both graphene and quantum dots. Here, a new application of GQDs as ideal electrode materials for supercapacitors is reported. To this end, a GQDs//GQDs symmetric micro‐supercapacitor is prepared using a simple electro‐deposition approach, and its electrochemical properties in aqueous electrolyte and ionic liquid electrolyte are systematically investigated. The results show that the as‐made GQDs micro‐supercapacitor has superior rate capability up to 1000 V s^?1, excellent power response with very short relaxation time constant (τ₀ = 103.6 μs in aqueous electrolyte and τ₀ = 53.8 μs in ionic liquid electrolyte), and excellent cycle stability. Additionally, another GQDs//MnO₂ asymmetric supercapacitor is also built using MnO₂ nanoneedles as the positive electrode and GQDs as the negative electrode in aqueous electrolyte. Its specific capacitance and energy density are both two times higher than those of GQDs//GQDs symmetric micro‐supercapacitor in the same electrolyte. The results presented here may pave the way for a new promising application of GQDs in micropower suppliers and microenergy storage devices.     

Catalytic materials manufactured by the polyol process for monolithic dye‐sensitized solar cells

Three types of screen‐printable catalytic pastes were successfully prepared to be used as counterelectrode for monolithic dye solar cells encapsulated with glass frit. The electroless bottom‐up method or so‐called polyol process has been applied to fabricate thermally stable SnO₂:Sb/Pt and carbon black/Pt nanocomposites. The catalytic and electric properties of these materials were compared with a new platinum‐free type of carbon counterelectrode. The layers containing low platinum amounts (less than 5 µg/cm²) exhibit a very low charge transfer resistance of about 0·4 Ω · cm². Also the conductive carbon layer shows an acceptable charge transfer resistance of 1·6 Ω · cm². Additionally the catalytic layer containing porous carbon black reveals excellent sheet resistance below 5 Ω/□; this feature has enabled to work out a low cost counterelectrode which combined suitable catalytic and conductive properties. The layers have been characterized using following methods: electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE‐SEM), energy filter transmission electron microscopy (EF‐TEM) and inductively coupled plasma mass spectroscopy (ICP‐MS). Copyright © 2008 John Wiley & Sons, Ltd.     

Resistivity and lifetime variation along commercially grown Ga‐ and B‐Doped Czochralski Si ingots and its effect on light‐induced degradation and performance of solar cells

A systematic study of the variation in resistivity and lifetime on cell performance, before and after light‐induced degradation (LID), was performed along ∼900‐mm‐long commercially grown B‐ and Ga‐doped Czochralski (Cz) ingots. Manufacturable screen‐printed solar cells were fabricated and analyzed from different locations on the ingots. Despite the large variation in resistivity (0·57–2·5 Ω cm) and lifetime (100–1000 µ s) in the Ga‐doped Cz ingot, the efficiency variation was found to be ≤ 0·5% with an average efficiency of ∼17·1%. No LID was observed in these cells. In contrast to the Ga‐doped ingot, the B‐doped ingot showed a relatively tight resistivity range (0·87–1·22 Ω cm), resulting in smaller spread in lifetime (60–400 µ s) and efficiency (16·5–16·7%) along the ingot. However, the LID reduced the efficiency of these B‐doped cells by about 1·1% absolute. Additionally, the use of thinner substrate and higher resistivity (4·3 Ω cm) B‐doped Cz was found to reduce the LID significantly, resulting in an efficiency reduction of 0·5–0·6%, as opposed to >1·0% in ∼1 Ω cm ∼17% efficient screen‐printed cells. As a result, Ga‐doped Cz cells gave 1·5 and 0·7% higher stabilized efficiency relative to 1 and 4·3 Ω cm B‐doped Cz Si cells, respectively. Copyright © 2005 John Wiley & Sons, Ltd.