铝离子电池电解液的研究进展

得益于铝负极的高质量/体积能量密度、低成本与高安全性,可充铝离子电池成为极具前景的下一代储能电池体系.铝离子电池主要是基于铝负极、正极材料及1-乙基-3-甲基咪唑氯化物([EMIm]Cl)基的离子液体电解液.目前,储铝正极材料的性能优化已取得了系列进展,但铝离子电池的实际应用受到了[EMIm]Cl基电解液的高成本、腐蚀...     

新型锂盐氟代磺酰亚胺锂电解液对锂离子电池性能的影响CSCD

采用新型锂盐双(氟代磺酰)亚胺锂(Li FSI)代替六氟磷酸锂(Li PF_6)作为锂离子电池的电解液锂盐,配制不同浓度的Li FSI/EC+EMC+DMC(质量比1∶1∶1)电解液,用循环伏安、电化学阻抗(EIS)、恒流充放电等实验并结合Li^+迁移数、电导率和黏度等物化参数的测试,研究新型锂盐浓度和电解液物化参数对电池倍率性能的影响。结果表明与同浓度的Li PF_6电解液相比,Li FSI电解液具有更高的离子传导能力和电导率及锂离子迁移数;在0.8~1.6 mol/L的浓度范围内,含Li FSI电解液的电池相对含Li PF_6电解液的电池表现出更好的电化学性能,更适用于高性能锂离子电池;1.2 mol/L为Li FSI电解液的最优浓度,此时其电导率和锂离子迁移数均达到最大值(κ=12.39 ms/cm,t_+=0.6327),制备的锂离子电池电化学阻抗最小,倍率性能最佳。     

直接甲醇燃料电池中聚苯胺载Pt电极的制备与性能测定

利用循环伏安方法电聚合导电高分子聚苯胺,应用到直接甲醇燃料电池(DMFC)中制备聚苯胺载Pt电极。电极的制备分两个步骤,首先电聚合载体聚苯胺,然后沉积催化剂Pt。聚苯胺载Pt电极的制备,提高了Pt的分散度,增加了Pt在电催化体系中的利用率。聚苯胺载铂电极(Pt/PANI/C)与直接碳载铂电极(Pt/C)通过比较甲醇的电催化氧化活性可知,Pt/PANI/C电极催化氧化甲醇的最大电流为50.7mA.cm-2,为Pt/C电极最大氧化电流7.6mA.cm-2的6.7倍。扫描电镜表征Pt/PANI/C电极上的铂颗粒大小为0.4μm左右。     

磷酸铁锂快充电解液的设计

锂离子电池被广泛应用于电子消费品、动力电池和储能等领域。在动力电池领域,磷酸铁锂和三元锂是两种常用的锂离子电池正极材料。磷酸铁锂由于电子电导率和离子扩散系数低的缺点,其快充性能一直不佳。电解液作为锂离子电池中离子传输的载体,在电池正负极之间起着离子传导的作用,也是磷酸铁锂电池获得快充能力的重要保证。在正负极材料、隔膜材料选型的基础上,基于电解液添加剂的机理分析,优化电解液设计,开发了一款性能良好的磷酸铁锂/石墨电池快充电解液。快充电解液以碳酸乙烯酯(EC)和碳酸甲乙酯(EMC)作为溶剂(质量比为3∶7),以1M的双氟磺酰亚胺锂(LiFSI)为锂盐,以2%碳酸亚乙烯酯(VC)、1%硫酸乙烯酯(DTD)、1%氟代碳酸乙烯酯(FEC)、0.5%三(三甲基硅烷)磷酸酯(TMSP)和0.5%丙烯酸卡必酯(EOEOEA)为添加剂。在4C充电倍率条件下,该电解液25℃常温循环寿命超过1500次,45℃高温循环也超过了1000次,具有很好的实际应用价值。     

Theoretical study on discharge behavior of LiFePO4 battery

使用多孔电极理论对LiFePO4（LFP）锂离子电池的放电行为进行了详细探讨,发现随着放电过程进行,电极内部的电化学反应从隔膜侧向集流体侧移动,并且移动过去之后LFP基本完成放电过程,放电截止时电化学反应截止在电极的某个位置,并不是所有的LFP颗粒都完成了放电。随后对放电速率、电极电导率和电解液扩散系数对放电过程的影响进行了研究。随着放电倍率增加,电化学反应推进的距离不断减少,并且峰值不断增大,峰值区域变窄。提高电极电导率可以保证电化学反应从隔膜侧开始进行,但是继续提高电极电导率并不能进一步将电化学反应的峰值向电极深处推进。较高的扩散系数可以保证所有的活性材料都能发生电化学反应。以上结论可对高性能LFP锂离子电池的设计和制备提供了有效的指导作用。     

离子液体对玉米秸秆组分的溶解选择性

为实现生物质原料的组分分离,研究了1-丁基-3-甲基咪唑甲酸盐([BMIM][HCOO])、1-丁基-3-甲基咪唑乙酸盐([BMIM][CH3COO])、1-丁基-3-甲基咪唑丙酸盐([BMIM][CH3CH2COO])、1-丁基-3-甲基咪唑二氰胺盐([BMIM][N(CN)2])4种离子液体在固液比为1∶20、温度为20~140℃下,对玉米秸秆各组分的溶解能力。结果表明:玉米秸秆在离子液体的溶解率随温度的增加而增加;4种离子液体中,[BMIM][CH3CH2COO]对玉米秸秆中纤维素和半纤维素的溶解能力最强,在140℃下溶解率分别达74.04%和79.22%,[BMIM][N(CN)2]对玉米秸秆中的木质素的溶解能力最强,在140℃下溶解率达75.15%;这4种离子液体对纤维素和半纤维素的溶解选择性均较低,[BMIM][N(CN)2]在140℃下对玉米秸秆中的木质素的选择溶解性系数可达2.03,显示出良好的分离性能。     

PEO基Li_(1.5)Al_(0.5)Ge_(1.5)(PO_4)_3固体复合电解质的制备

以聚环氧乙烷(PEO)为黏结剂,离子导电性的Li1.5Al0.5Ge1.5(PO4)3(LAGP)为主相,乙腈为溶剂,按照EO/Li,摩尔比为13,变化Li N(CF3SO2)2(Li TFSI)中Li+与LAGP中Li+的比例,通过溶液浇注法制备得到LAGP-PEO(Li TFSI)固体复合电解质。用X射线衍射、扫描电镜(SEM)和电化学阻抗(EIS)等方法对固体复合电解质的形貌、结构和电导率进行表征。结果表明,LAGP可与PEO(Li TFSI)部分络合并均匀分散于PEO(LITFSI)内,整个体系内存有三个主体相,即PEO(Li TFSI)的复合相、LAGP晶相以及PEO与两种锂盐的过渡相。通过阻抗谱图发现,当质量比w(LAGP)∶w(PEO)=6∶4时,LAGP-PEO(Li TFSI)固体复合电解质具有最高的室温电导率,为2.68×10?5 S/cm,在333 K时,达到1.86×10?4 S/cm,接近LAGP的电导率水平。这说明固体复合电解质中加入LAGP即降低了PEO的结晶度,LAGP自身的电导率也有一定贡献。     

LiI-Urea二元离子液体基电解质导电性能研究

简单配位合成LiI-Urea二元离子液体并向其中添加第三组分I2得到二元离子液体基电解质.采用FITR和紫外分光光度计表征了离子液体的结构及电解质的组成.采用线性扫描伏安法测试了电解质中I-3的极限电流密度,以此计算得到I-3的扩散系数.测试了电解质的电导率,探讨了电解质的组成与电导率之间的关系.结果表明,LiI/Urea的配比影响两组分之间的络合作用,从而影响I-3的扩散系数及电解质的电导率.室温下,两组分的摩尔比为n(LiI/Urea) =0.225时,I-3的扩散系数为2.29×10-6cm2·s-1,电导率达到2.63×10-3 S·cm-1,满足染料敏化太阳电池实用要求.     

原位固化对硅氧负极性能的影响北大核心CSCD

利用聚合物单体与引发剂在加热情况下能自发聚合的特点,在硅负极电解液中引入高离子电导率单体和引发剂,注液后采用热聚合的方式制备了原位固化的硅负极电芯。通过充放电设备测试了电芯的循环、倍率等性能,通过扫描电子显微镜(SEM)、X射线衍射光谱仪(XRD)、电化学工作站以及压汞仪等表征测试手段,对硅负极极片形貌和电化学性能进行表征。结果表明,固化后电芯常温0.5 C循环次数为349周,相比于液态电芯的230周,循环次数提升51.74%,同时固化后硅负极极片膨胀率相比液态电芯降低4.6%,极片孔隙率降低3.8%,且减少了循环后EIS和DCIR的增长,电芯性能明显优于液态电芯。从极片表征结果看出,固化可以改善硅负极极片界面,在硅负极表面和极片孔隙内形成一层聚合物电解质层,避免硅负极在嵌锂时膨胀粉化脱落,并稳定极片离子和电子导电网络。本研究有助于推动硅负极应用,为高能量密度电池技术的研发提供实验依据。     

钒电池五价钒溶液的电导性质

全钒氧化还原液流电池被认为是满足风能、太阳能等新能源最有可行性的大规模储能技术之一。钒电池电解液既是导电介质又是能量存储的关键材料,是钒电池储能与能量转化的核心。对钒电池电解液热力学性质的研究,有助于深入认识溶液的本质特性,对钒电池的容量、能量密度以及系统稳定性的提高均具有极大意义。采用电导法测量了温度范围在278.15~318.15 K,不同浓度的V(Ⅴ)硫酸水溶液三元体系的电导率,通过多项式拟合及外推法,将V(Ⅴ)+H2SO4+H2O三元体系的电导率外推得到V(Ⅴ)水溶液二元体系电导率,并计算了离子的极限摩尔电导率、Stocks半径、迁移数、扩散系数和溶液电导活化能等参数并讨论了浓度、温度对这些性质的影响规律。     

Importance of ionic liquid-doped solid polymer (PVPI) electrolyte

The aim of the present work is to synthesize a porous nanocrystalline TiO₂ electrode and to use a new kind of solid polymer electrolyte, poly(N-methyl 4-vinylpyridine iodide), doped with an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethane sulphonyl)imide, for dye-sensitized solar cell (DSSC) applications. The fabrication process of nanoporous TiO₂ electrode and electrical, structural and photoelectrochemical properties of polymer electrolytes are presented in detail. A novel DSSC has also been fabricated, which shows overall efficiency of 0.56% at one sun condition.     

Preparation and characterization of a micro-porous polymer electrolyte with cross-linking network structure for dye-sensitized solar cell

A PVdF-HFP/PEG/PEGDMA cross-linking film has been prepared as the electrolyte for dye-sensitized solar cell (DSSC). The film can be made porous by controlling the evaporation behavior of solvents. Room temperature ionic conductivity of the micro-porous film exceeds 1 mS/cm. In addition, we also evaluated the significance of cell gap in DSSC by analyzing the impedance spectroscopy of the cell with polymer electrolyte. Finally, by decreasing the film thickness, the DSSC equipped with 11 μm, micro-porous and cross-linked film showed a conversion efficiency over 4% and 5% under 1 and 0.16 Sun, respectively.     

A quasi solid-state dye-sensitized solar cell containing binary ionic liquid and polyaniline-loaded carbon black

A quasi solid-state dye-sensitized solar cell (DSSC) is fabricated using 1-propyl-3-methylimidazolium iodide (PMII) and polyaniline-loaded carbon black (PACB) as the composite electrolyte. The electrolyte without added iodine is sandwiched between TiO₂ working electrode and platinum counter electrode (CE). A power conversion efficiency (η) of 5.81% is achieved with this type of cell. With the addition of 1-ethyl-3-methylimidazolium thiocyanate (EMISCN), a low-viscosity ionic liquid (IL), the cell with the binary ionic liquid (bi-IL) renders an efficiency of 6.15%, the best for any quasi solid-state DSSC without the addition of iodine. To fabricate a low cost DSSC using the bi-IL, the platinum layer of the counter electrode is replaced with a polymer layer, 3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4] dioxepine (PProdot-Et₂) through electrodeposition, and the corresponding DSSC shows an efficiency of 5.27%. At-rest stability of the quasi solid-state DSSC with bi-IL is compared with that of a liquid electrolyte DSSC at room temperature; the power conversion efficiency of the former shows a decrease of hardly 3% after 1000 h, while that of the latter shows a decrease of about 30%. The quasi solid-state cell shows unfailing durability at 70 °C.     

Influence of polymer concentration and dyes on photovoltaic performance of dye-sensitized solar cell with P(VdF-HFP)-based gel polymer electrolyte

A series of gel polymer electrolytes (GPEs) is synthesized using Poly(vinylidenefluoride-hexafluoropropylene) P(VdF-HFP) as the host matrix and propylene carbonate (PC)–diethyl carbonate (DEC) as plasticizers to fabricate dye-sensitized solar cells. Equal amounts of PC and DEC are used to comprehend high dielectric constant and low viscosity of the electrolyte. The as-prepared GPEs are characterized by XRD, FTIR and SEM. Their thermal properties and ionic conductivities are investigated by TGA/DSC analyses and AC impedance measurements, respectively. The optimized gel polymer electrolyte gives a maximum ionic conductivity of 5.25 × 10⁻³ S cm⁻¹ at room temperature. The formation of porous structure in the electrolyte film supports the entrapment of large volumes of liquid electrolyte inside its cavities. The role of N3 and N719 dyes are also investigated for better photovoltaic performance of DSSC. The overall light-to-electrical-energy conversion efficiencies of 3.95% and 4.41% are obtained for N3 and N719 dyes, respectively, under 100 mW cm⁻² irradiation, which are comparable to those obtained from the corresponding liquid electrolyte cell.     

Analysis and assessment of dye‐sensitized solar cell at different materials parameters and environmental conditions

The dye‐sensitized solar cell (DSSC) provides a clean, renewable, and cheap energy source. Since the beginning of the 1990s, DSSC has seen enormous development because of an increase in world energy consumption and the concerns about the environmental impact associated with combustion of fossil fuels. However, the efficiency of the DSSC to be a competitive energy source has not been achieved. In this work, we analyzed the effect of various materials parameters and environmental conditions on the performance of DSSC. To maintain the optimum performance for DSSCs and to enhance the energy and exergy efficiency in practical application environments, it is recommended to have the porous thin film TiO₂ at porosity of 0.40, thin film thickness of porous TiO₂ at 0.0005 cm, thickness of redox electrolyte at 0.0002 cm, diffusion coefficient of 0.0002 cm² s^?1, electron diffusion length of 0.0013 cm, and operating temperature of 300 K with light intensity of 100 mW cm^?2. Copyright © 2016 John Wiley & Sons, Ltd.     

Study of the carbon material electrolyte interface

The formation mechanism of the passivation film on the surface of carbon-based electrodes during the first electroreduction was studied by chronopotentiometry and impedance spectroscopy. Two types of electrolytes are compared: ethylene carbonate-based liquid and poly (ethylene oxide)-based solid state electrolytes. The differences in stability towards reduction and in mobility of the solvent molecules in these electrolytes suggest two different mechanisms of reduction: (i) decomposition of the solvent in the liquid electrolyte system, and (ii) formation of an immobilized dense layer in the solid electrolyte system. The chemical diffusion coefficient was also determined by impedance spectroscopy at increased amounts of lithium in the carbon electrode. The film formation and the diffusion are correlated.     

Quasi solid state polymer electrolyte with binary iodide salts for photo-electrochemical solar cells

Quasi-solid-state polymer electrolytes can be used in dye sensitized solar cells (DSSCs) in order to overcome various problems associated with liquid electrolytes. Prior to fabricating commercially viable solar cells, the efficiency of quasi solid state DSSCs needs to be improved. Using electrolytes with a binary iodide mixture is a novel technique used to obtain such efficiency enhancement. In this work we report both conductivity and solar cell performance enhancements due to incorporation of a mixture containing LiI and tetrahexylammonium iodide in a quasi-solid-state electrolyte. The conductivity of the electrolyte increases with added amounts of LiI and thus the highest conductivity, 3.15 × 10⁻³ S cm⁻¹ at 25 °C, is obtained for the electrolyte 100 wt% LiI. The predominantly ionic behavior of the electrolytes was established from dc polarization measurements. The iodide ion conductivity, measured using iodine pellet electrodes decreased somewhat with increasing amount of LiI even though the overall conductivity increased. However, the highest efficiency was obtained for the DSSC containing a polymer electrolyte with Hex₄N⁺I^¯:LiI = 1:2 mass ratio. This cell had the largest short circuit current density of about 13 mA cm⁻² and more than 4% overall energy conversion efficiency. The results thus show that electrolytes with Hex₄N⁺I^¯/LiI mixed iodide system show better DSSC performance than single iodide systems.     

Electrical and structural properties of ionic liquid doped polymer gel electrolyte for dual energy storage devices

This paper reports the synthesis, characterization and dual electrochemical application of a new kind of ionic liquid (IL) based polymer electrolyte. The ionic liquid 1, 2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI) and polymer Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) have been chosen for present study. The electrical conductivity measurement shows many fold enhancement of ionic conductivity by blending IL into polymer matrix. Scanning electron microscopy (SEM) image confirms the uniform surface morphology of the synthesized thin film and cross-section image shows the interface layer of polymer and electrode. We have fabricated an efficient dye sensitized solar cell (DSSC) and electric double layer capacitor (EDLC) using IL-polymer electrolyte (optimized maximum conductivity) system which further affirms that this material is highly stable and reliable for long duration in energy devices.     

Anchorage of N3 dye-linked polyacrylic acid to TiO2/electrolyte interface for improvement in the performance of a dye-sensitized solar cell

A synthetic route was developed to link N3 dye to polyacrylic acid (PAA) using ethylenediamine (en) as the linker. The resulting complex, PAA–en–N3, was then coated onto a TiO₂ film. The modified TiO₂ film electrode (hereafter PAA–en–N3/TiO₂), when used as the photoanode in a dye-sensitized solar cell (DSSC), exhibited enhanced solar energy conversion efficiency compared with that of the usual DSSC with the N3/TiO₂ film electrode. The increase in efficiency was attributed to the increased open-circuit voltage (V_oc) and short-circuit photocurrent (J_sc). The increase in V_oc was attributed to the formation of a hydrophobic PAA–en–N3 layer on the TiO₂/electrolyte interface, while the increase in J_sc was attributed to the additional dye acquired by the TiO₂ film from the PAA–en–N3 complex.     

Photovoltage enhancement of dye sensitised solar cells by using ZnO modified TiO2 electrode

Abstract

A ZnO modified TiO₂ (ZnO/TiO₂) film was prepared by immersing TiO₂ electrodes in Zn(Ac)₂ aqueous solution. The open circuit voltage of a dye sensitised solar cell (DSSC) with the ZnO/TiO2 film electrode has a dramatic enhancement, compared to the DSSC with the TiO₂ film electrode. However, the short circuit current density of the DSSC with the ZnO/TiO₂ film electrode is lower than that with TiO₂ electrode. The film electrodes were characterised by SEM, EDX and UV-vis, and the photoelectric performance of DSSCs were measured. The photovoltage enhancement is attributed to the formation of a flat-band potential energy barrier by ZnO at TiO₂/electrolyte interface. The decline of the photocurrent with ZnO/TiO₂ film electrode is due to poor dye absorption on larger particles of ZnO.