Electrochemomechanical coupled behaviors of deformation and failure in electrode materials for lithium-ion batteries

The growing demands of lithium-ion batteries with high energy density motivate the development of high-capacity electrode materials. The critical issue in the commercial application of these electrodes is electrochemomechanical degradation accompanied with the large volume change, built-in stress, and fracture during lithiation and delithiation. The strong and complex couplings between mechanics and electrochemistry have been extensively studied in recent years. The multi-directional couplings, e.g.,(de)lithiation-induced effects and stress-regulated effects, require cooperation in the interdisciplinary fields and advance the theoretical and computational models. In this review, we focus on the recent work with topics in the electrochemomechanical couplings of deformation and fracture of conventional and alloying electrodes through experimental characterization, theoretical and computational models. Based on the point of view from mechanics, the strategies for alleviating the degradation are also discussed, with particular perspectives for component-interaction patterns in the composite electrodes. With interdisciplinary principles, comprehensive understanding of the electrochemomechanical coupled mechanism is expected to provide feasible solutions for low-cost, high-capacity, high-safety and durable electrodes for lithium-ion batteries.     

电凝聚法处理印染废水过程中铁电极行为的研究

本文对以铁为电极进行电凝聚处理印染废水时pH值对铁电极行为的影响进行了研究。测出在恒电流条件下电解电压,阴极电位和阳极电位随PH值的变化曲线以及不同pH值条件下恒电位极化曲线。据此研究了电解时电极反应和应控制的pH条件。     

充电速率对镍电极析氧性能及充电效率的影响

采用三电极体系 ,通过排水取气法考察了不同充电速率对镍电极析氧特性的影响 ,得出在镍电极充电过程中 ,析氧时间、析氧电位和充电效率随充入容量的变化规律 ,总结出充电速率对充电效率的影响。要想降低析氧速率提高充电效率 ,应该选择合适的添加剂     

Electro-oxidation treatment of Sn/PANI electrode and electrocatalytic activity of Pt/Sn hydroxide/PANI composite electrodes

After being electro-oxidized by cyclic voltammetry（CV） method in 0.5 mol/L H2SO4 solution or in 0.2 mol/L H2O2＋0.5 mol/L H2SO4 solution, the Sn/polyaniline （PANI） electrodes were modified with Pt microparticles by pulse galvanostatic method, thus Pt/Sn hydroxide/PANI electrodes were prepared. The electrocatalytic activities of the Pt/Sn/PANI electrode and Pt/Sn hydroxide/PANI electrode for formaldehyde electro-oxidation were investigated by CV method. The effects of deposition charges （Qdep） of PANI, Sn and Pt, scan rate and formaldehyde concentration on the electrocatalytic activity of Pt/Sn hydroxide/PANI electrode were also studied. The results show that the electrocatalytic activities of the Pt/Sn hydroxide/PANI electrodes are much higher than those of the Pt/Sn/PANI electrode.     

低碳高效的太阳能级硅制备新技术

对固态二氧化硅在850℃氯化钙熔盐中的伏安行为分析的基础上,通过系统研究了二氧化硅粉末压片在850℃氯化钙熔盐中恒电位电解产物的物相和纯度,确定了通过熔盐电解法制备单质硅的电位范围.实验结果表明,熔盐电解二氧化硅制备单质硅合适的电解电位范围为0.65V(vs.Ca/Ca2+)至1.15V.通过在此电位范围内恒电位电解产物纯度和能量效率分析,明确了熔盐电解制备单质硅最优化的电解电位为0.85V,此时电解产物纯度高达99.41%,电流效率为79.3%,电解能耗为11.5kWh/kg Si.上述结果表明,熔盐电解法制备单质硅与传统碳热还原法相比在能量效率和产物纯度上具有优势.通过电解产物杂质来源的分析,提出进一步提高产物纯度以达到太阳能级硅要求的措施,为通过熔盐电解法直接制备太阳能级硅提供了科学基础.     

液晶模板法制备Co3O4分级多孔结构薄膜和赝电容性能研究

采用液晶模板法制备Co3O4纳米薄膜,用循环伏安法和恒流充放电测试方法,表征分析其微观结构和电化学性能。结果表明：Co3O4薄膜是多晶体,呈分级多孔结构,该结构有利于电子和离子的扩散,可显著改善超级电容器的比电容,增强电容保持能力,是一种优良的超级电容器电极材料。     

液晶模板法制备Co3O4分级多孔结构薄膜和赝电容性能研究

采用液晶模板法制备Co3O4纳米薄膜,用循环伏安法和恒流充放电测试方法,表征分析其微观结构和电化学性能。结果表明:Co3O4薄膜是多晶体,呈分级多孔结构,该结构有利于电子和离子的扩散,可显著改善超级电容器的比电容,增强电容保持能力,是一种优良的超级电容器电极材料。     

Comparative study of oxidation ability between boron-doped diamond （BDD） and lead oxide （PbO_2） electrodes

The electrochemical oxidation capabilities of two high-performance electrodes,the boron-doped diamond film on Ti(Ti/BDD)and the lead oxide film on Ti(Ti/PbO2),were discussed.Hydroxyl radicals(·HO)generated on the electrode surface were detected by using p-nitrosodimethylaniline(RNO)as the trapping reagent.Electrochemical oxidation measurements,including the chemical oxygen demand (COD)removal and the current efficiency(CE),were carried out via the degradation ofp-nitrophenol(PNP)under the galvanostatic condition.The results indicate that an indirect reaction,which is attributed to free hydroxyl radicals with high activation,conducts on the Ti/BDD electrode,while the absorbed hydroxyl radicals generated at the Ti/PbO2 surface results in low degradation efficiency.Due to quick mineralization which combusts PNP to CO2 and H2O absolutely by the active hydroxyl radical directly,the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO2 electrode,notwithstanding the number of hydroxyl radicals produced on PbO2 is higher than that on the BDD surface.     

基于细观结构的沥青碎石封层路面力学行为分析

为了认识沥青碎石封层的力学行为与破坏机理,采用有限元软件建立沥青碎石封层细观结构二维有限元模型,分析在竖向荷载作用下封层内部细观结构应力、应变和位移的力学行为特性。分析结果显示：轮迹内侧边缘碎石竖向位移最大,偏转角度最小;相反,轮迹外边缘碎石偏转角度最大,并向两侧逐渐递减。沥青层内的水平应变主要为压应变,轮迹外侧沥青和胶浆层接触面上剪应变最大。黏结层的水平变形、剪切变形均不同程度大于沥青层,黏结层与胶浆层交界处具有最大等效Mises应力,易发生剪切破坏。胶浆层的中心主要为受压变形,胶浆层两侧边缘处主要表现为较高剪切变形。     

石墨烯化石墨/聚苯胺电极的制备及电容特性

通过电解剥落得到的表面石墨烯化的石墨电极(graphene layers/graphite plate, GL/GP)为基底,在硫酸介质中以苯胺为单体,采用循环伏安法(cyclic voltammetry, CV)制备了表面石墨烯化的石墨/聚苯胺(graphene layers/graphite plate/polyaniline, GL/GP/PANI)电极,并探究聚合圈数对GL/GP/PANI电极比电容的影响。利用场发射扫描电镜(scanning electron microscope, SEM)对电极材料的形貌进行表征。在0.5 M H₂SO₄电解液中,对合成的电极材料进行循环伏安、恒电流充放电(chronopotentiometry, CP)和电化学稳定性测试。结果表明,在表面石墨烯化的石墨电极上合成的PANI具有棒状结构,电流密度为0.085 mA/cm²时, GL/GP/PANI电容器的比电容可达1 042.8 F/g。提供了一种新的超级电容材料基底电极的构建方式。     

锂离子电池硅电极新型粘合剂的研究进展

硅(Si)作为目前理论容量最高的一种负极材料,被认为是最有前景的一种锂离子电池负极材料,但较大的体积膨胀和较差的导电性限制了其在锂离子电池当中的应用。在硅电极体系中,选择一种合适的粘合剂对于硅电极的机械完整性和电子完整性起着至关重要的作用。总结了硅负极材料的容量衰减机理,介绍了粘合剂结构的不同对硅电极性能的影响以及新型的导电粘合剂在硅电极方面的应用。     

电纺聚乙烯醇纳米纤维膜无酶过氧化氢传感器的制备

用静电纺丝的方法将聚乙烯醇（PVA）静电纺丝到裸铂电极表面,分别采用扫描电镜法、循环伏安法、电流时间曲线法、交流阻抗等方法对该电极进行表征.研究了过氧化氢在该聚乙烯醇修饰电极的电化学行为.实验结果表明：聚乙烯醇纳米纤维膜呈现出理想的疏松多孔的网状结构,极大地增大了电极的有效表面积;在pH=7.4的磷酸盐缓冲溶液中相比裸铂电极,聚乙烯醇纳米纤维膜修饰电极对过氧化氢的响应电流有明显的提高,过氧化氢的浓度在7.8～2 900μmol/L范围内,与其还原电流呈良好的线性关系,检测限达1.1μmol/L.该聚乙烯醇修饰电极可以作为电化学无酶传感器用于低浓度过氧化氢的检测.     

石墨三维电化学反应器工作性能分析

采用自制石墨三维电化学反应器,考察了在粒子大小、主极板电压及粒子数量变化的情况下其粒子电流以及主极板电流,对石墨三维电化学反应器的工作效率进行了分析,在此基础上,利用二维反应器和石墨三维电化学反应器处理甲硝唑废水和亚甲基蓝废水,考察废水中总有机碳降解率及脱色效果.结果表明：粒子电流与主极板电压、粒子大小成正相关,石墨粒子和钛粒子两者电化学行为相同,但石墨粒子的粒子电流更大,说明在三维电极反应体系中,用石墨做粒子电极是可行的,可通过调整充填粒子大小和粒子数量改变粒子电流,从而提高三维电极反应器降解速率;当石墨三维反应器主极板外电压为t2V、电解质浓度为0.1 mol/L、石墨粒子数量为8时,反应前15 min比二维反应器反应速度快,对甲硝唑有机废水总有机碳去除率比二维电极反应器高14％,对亚甲基蓝废水脱色率比二维反应器高10％,说明设计的石墨三维电化学反应器对甲硝唑和亚甲基蓝废水中总有机碳和色度有很好的降解效果,且优于二维反应器.     

添加锰对氢氧化镍电极行为影响的研究

在室温碱溶液中,添加钴或锰可以改善氢氧化镍电极的性能和反复周期的充放电性。在5mol/L KOH溶液中,与锰共沉积的镍氢氧化物电极具有更高的氧析出过电位。循环伏安法研究的结果表明锰在镍氢氧化物中可能改进电极的寿命和性能。     

交流电场作用下微电极表面电渗流流速的计算

为解决微流体在交流电场作用下电极表面电渗流的流速计算方法,在电极极化产生双电层的基础上,建立了交流电渗等效电路模型,通过对双电层容抗和溶液电阻的计算,得出了微电极表面交流电渗流流速的计算公式,并对各点交流电渗流速与频率的关系进行了分析.结果表明,电极参数为宽80μm,长2 mm,电极间距20μm的对称电极交流电渗,在电极表面上的各点电渗流流速与输入信号频率对数呈正态分布状态.研究结果为交流电渗驱动微流体提供了理论参考依据.     

纳米门炭结构及超级电容特性

以生石油焦为原料,采用KOH活化法制备纳米门炭。采用氮气吸附法、X射线衍射(XRD)和光电子能谱衍射(XPS)对其孔结构、微晶结构和表面性质进行分析,并以其为电极组装超级电容器,测试了电容特性。结果表明:纳米门炭可在3.5V电压下工作,通过首次充电过程中的电化学活化而获得较大的比电容。样品N900比表面积仅为61m2/g,但比电容确高达136.7F/g,能量密度高达58.1Wh/kg。     

Effects of binder strength and aggregate size on the compressive strength and void ratio of porous concrete

To test the influence of binder strength, porous concretes with 4 binder strengths between 30.0-135.0 MPa and 5 void ra tios between 15%-35% were tested. The results indicated that for the same aggregate, the rates of strength reduction due to the in creases in void ratio were the same for binders with different strengths. To study the influence of aggregate size, 3 single size aggre gates with nominal sizes of 5.0, 13.0 and 20.0 mm (Nos. 7, 6 and 5 according to JIS A 5001) were used to make porous concrete. The strengths of porous concrete are found to be dependent on aggregate size. The rate of strength reduction of porous concrete with small aggregate size is found to be higher than that with larger aggregate size. At the same void ratio, the strength of porous concrete with large aggregate is larger than that with small aggregate. The general equations for porous concrete are related to compressive strength and void ratio for different binder strengths and aggregate sizes.     

Electrochemical Intercalation of Lithium into Raw and Mild Oxide-treated Carbon Nanotubes Prepared by CVD

The raw carbon nanotubes ( CNTs ) prepared by chemical vapor deposition ( CVD ) were used in electrochemical lithiation. To remove the impurity the mild oxidation was done on the samples. The electrochemical characteristics of the two samples are investigated by the galvanostatic charge-dischorge measurements and cyclic voltammetry. The structural and interfacial changes of the CNTs electrode were analyzed by XRD and FTIR. The samples show a reversibility of lithium intercalation and de-intercalation. The reversible capacities of the first five cycles are larger than 300 mAh/ g and the irreversible capacity of the first cycle was much larger than that mentioned in literatures. There is no identical change in the structure during the charge and discharge. The reactions at the interface between electrode and the electrolyte are similar to those of other carbonaceous materials.     

循环伏安法研究添加剂对镍电极的影响

利用循环伏安来研究不同添加剂对镍电极性能的影响。本研究循环伏安的扫描速度为 0 .5 m V· s- 1,通过比较含不同添加剂的镍电极的循环伏安图 ,根据氧化峰、还原峰和析氧峰之间的关系可以得出 ,锶、钴、镁和锌是理想的添加剂。这些添加剂在一定程度上改善了活性物质的结构 ,提高镍电极的可逆性 ,增加镍电极的充电效率和放电深度     

石墨与GIC电极在硫酸溶液中的循环伏安特性

为深入认识石墨与石墨层间化合物在Ｈ２ＳＯ４溶液中电化学嵌入／脱嵌行为及有关影响因素,探讨其作为二次电池电极材料的可能性,进行了循环伏安测量与充、放电实验。结果表明,Ｈ２ＳＯ４的浓度对两咱电极的嵌入／脱嵌容量、极化大小以及过氧化物的生成等均有较大的影响;