非水体系中钒酸锂/聚吡咯复合正极材料的制备及性能研究

采用乙醇作为介质,FeCl₃为氧化剂,对甲苯磺酸钠为掺杂剂,通过吡咯单体在钒酸锂表面的氧化聚合制备出了钒酸锂/聚吡咯(LiV₃O₈/PPy)复合材料。采用X-射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)对复合材料的结构与形貌进行表征。用恒流充放电测试、循环伏安(CV)和交流阻抗(EIS)等研究了聚吡咯包覆量对材料电化学性能的影响。结果表明：在钒酸锂表面均匀地包覆了一层厚度约10nm的聚吡咯,但并没有改变钒酸锂的晶型结构。当聚吡咯包覆量为6% 时,复合材料的电化学性能最好,在0.1C充放电倍率下,首次放电比容量为274mAh/g,循环100次后样品的放电比容量为239.4mAh/g,容量保持率为87.4%,而未包覆PPy的LiV₃O₈,其首次放电比容量为227.4mAh/g,循环100次后样品的放电比容量为160.1mAh/g,容量保持率仅为70.4%。LiV₃O₈/PPy复合正极材料的电化学性能得到了明显提高。     

成分设计优化TiC/Hastelloy复合材料的抗氧化性能

TiC/Hastelloy复合材料是极具应用前景的中温固体氧化物燃料电池连接体材料,而抗氧化性能是影响其应用的关键性能之一。通过无压反应渗透工艺分别制备出含有50vol%和58vol%金属基体的TiC/Hastelloy复合材料。高金属含量使复合材料中的Cr含量增加,促进连续Cr₂O₃氧化层的形成,抑制Ni和Ti原子的外扩散,进而优化复合材料的抗氧化性能。氧化膜中Ti和Ni的氧化物含量降低,复合材料的氧化增重由2.03 mg·cm^-2降低到0.55 mg·cm^-2。同时,为了抑制Cr挥发,在含有58vol%金属基体的TiC/Hastelloy复合材料中引入Co。在氧化过程中,Co和金属基体中的Fe在Cr₂O₃氧化层中具有较快的扩散速率,可以在Cr₂O₃氧化层外侧原位形成CoFe₂O₄层。     

磷酸铁锂正极墨水配制及其电化学性能研究

磷酸铁锂(LiFePO₄, LFP)作为锂离子电池正极材料因其放电容量大、价格低廉和对环境无污染受到广泛关注。本研究旨在制备出适用于微电子打印机的性能优良的磷酸铁锂及相应复合材料正极墨水。通过配制不同浓度的磷酸铁锂墨水并制备成电极,研究最优浓度墨水制备成电极的电化学性能。研究表明,倍率为0.1 C时,打印浓度为10%的磷酸铁锂电极放电比容量高达142 mAh·g^-1,基于磷酸铁锂具有较差的导电性,选择加入少量还原氧化石墨烯提高其导电性。还原氧化石墨烯质量分数为0.6%时,磷酸铁锂和还原氧化石墨烯复合材料放电比容量达152.1 mAh·g^-1,库伦循环效率为99.2%,说明引入还原氧化石墨烯有利于提高材料整体性能。     

CC/PANI/TiO2复合材料的制备及其光催化性能研究

先采用原位聚合的方法在碳布上负载聚苯胺,然后利用溶剂热法在制备的碳布/聚苯胺(CC/PANI)复合材料上生长二氧化钛纳米片,得到了可便捷分离的CC/PANI/TiO₂复合光催化材料。通过SEM、XRD、UV、FTIR、XPS等手段对所制备的样品进行了形貌和结构表征,并比较了CC/PANI/TiO₂复合材料和纯TiO₂紫外-可见光条件下催化降解RhB的活性差异,结果表明CC/PANI/TiO₂复合材料具有比TiO₂更优异的光催化活性。光致发光光谱说明CC/PANI/TiO₂复合材料的发光强度比纯TiO₂的弱,有效抑制了光生载流子的复合;瞬态光电流响应和电化学阻抗谱(EIS)证明CC/PANI/TiO₂纳米复合材料更有效促进电子-空穴对分离和提高转移效率;活性物质捕捉实验证实?OH和?O_2^-是复合材料光催化降解RhB过程中的主要活性物质。CC/PANI/TiO₂复合材料循环利用6次后,仍然具有较高的催化活性,显示了其在污水处理领域中的良好应用前景。     

不同锂源对高温固相法制备NCM811正极材料储锂性能的影响

采用4种不同的锂盐(LiOH.H₂O、Li₂CO₃、LiNO₃、CH₃COOLi),以高温固相法制备了LiNi_0.8Co_0.1Mn_0.1O₂正极材料。利用X射线粉末衍射(XRD)和场发射电子显微镜(FESEM)对所制LiNi_0.8Co_0.1Mn_0.1O₂材料的微观结构进行了表征,发现所有合成的LiNi_0.8Co_0.1Mn_0.1O₂样品尺寸均为微米级大小,具有层状结构(R-3m空间群)。电化学测试结果表明采用不同锂源制备的LiNi_0.8Co_0.1Mn_0.1O₂样品的电化学性能差别很大。其中采用LiOH?H₂O为锂源,经500 °C预烧结6 h后,在800 °C下烧结16 h获得的样品锂镍混排程度最低,电化学性能最佳。例如,在0.1 C(1 C=180 mA/g)倍率下其可逆比容量高达206.2 mA.h/g,在10 C大倍率下,其可逆比容量仍保持有80.9 mA.h/g;在0.5 C倍率下100次充放电循环过程中,最高放电比容量为176.2 mA.h/g,平均放电比容量为140.1 mA.h/g。动力学及电极稳定性分析发现,LiOH?H₂O制备的样品的电化学可逆性最好,Li^₊扩散系数最大,充放电循环过程中结构稳定性最好。     

RMI法制备穿刺C/C-SiC复合材料的微结构及烧蚀性能研究

以无纬布/网胎0°/90°叠层穿刺预制体为增强体,采用化学气相渗(Chemical vapor infiltration,CVI)、树脂浸渍碳化(Polymer infiltration carbonization,PIC)与反应熔渗(Reactive melt infiltration,RMI)复合工艺制备穿刺C/C-SiC复合材料,研究其微观组织及在C₂H₂-O₂焰中的烧蚀行为。结果表明：无纬布、穿刺纤维束由CVI+PIC制备的碳基体填充而形成致密C/C区域,RMI生成的SiC主要位于网胎层中,其含量37.3wt%。复合材料表面因过量硅化而形成了SiC富集层。烧蚀距离20mm、O₂:C₂H₂=2:1时,烧蚀600s后材料X-Y、Z向线烧蚀率分别为：0.8×10^_-4 mm/s、3.6×10^_-4 mm/s,比PIP工艺制备C/C-SiC材料烧蚀率小一个数量级。烧蚀面SiC富集层保护及被动氧化作用是材料具有优异抗氧化烧蚀性能的主要原因。随烧蚀距离由20mm向10mm减小,复合材料烧蚀率先缓慢变化后快速增大,烧蚀率快速增长阶段复合材料发生主动氧化烧蚀。     

基于碳纳米管宏观膜的高比容量及高电化学稳定性钛酸锂负极

通过对预先将钛酸锂(Li₄Ti₅O₁₂,LTO)材料组装的电池进行预充电脱锂(活化)的方式改变其结构,增强嵌锂能力,制备出高比容量Li₄Ti₅O₁₂;然后以CMF(碳纳米管宏观膜)为集流体,替代金属箔集流体改善活性物质与集流体的结合界面,提高其电化学稳定性,最终得到具有高比容量及高稳定性的LTO电极。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学测试等表征技术进行表征。结果表明：经过预脱锂活化后的LTO可容纳锂离子的空位增加,晶面间距发生显著的增大,经测试其在1C倍率能发挥192.7 mAh/g的比容量,比正常的Li₄Ti₅O₁₂材料提高约30 mAh/g;引入的CMF集流体能增强与活性材料的结合力,减小其在大电流下产生的接触阻抗,使其在5C倍率下仍具有150 mAh/g的比容量,表现出优异的倍率性能。     

非晶TiO2 纳米管形貌对其作为超级电容器电化学性能的影响

采用改进的两步电化学阳极氧化和电化学氢化法制备了不同管径、长度和壁厚的氢化无定型TiO₂纳米管阵列（H@am-TNAs）。结果表明,电化学氢化对TiO₂纳米管阵列的结构影响不大。经过电化学氢化后,纳米管在100 mV·s^-1时的比电容为4.05 mF·cm^-2,比未氢化的管长和管径相同的TiO₂纳米管的比电容大20倍。纳米管的比电容不仅与管长有关,还受管径的影响。通过指数函数拟合,纳米管的长径比呈线性关系。面积电容/长径比达到0.056,几乎相当于锐钛矿相TiO₂纳米管。阳极化处理后的纳米管具有最小的电荷转移阻力和最佳的离子扩散/输运动力学,具有最高的面积容量。此外,为了研究H@am-TNAs纳米管的电化学性能的润湿性,相同的H@am-TNAs电极在C-V和C-P测试前,在电解液中浸泡不同时间,结果表明,比电容随着浸泡时间的增加而减小。     

B参杂对NiO/Ni(OH)2电极材料电容性能的影响

通过化学镀再电化学氧化的方法在铜片表面制备出带有微米微坑和微米微球的均一NiO/Ni(OH)₂和B参杂的NiO/Ni(OH)₂(B)两种电极材料,采用扫描电镜(SEM/EDX)、X射线衍射(XRD)、X射线光电子能谱(XPS)和电化学技术对所制备的两种电极材料进行表征和电化学性能测试。SEM、XRD和XPS的测试结果表明, 所制备的两种电极材料由Ni、NiO和Ni(OH)₂组成,并且NiO/Ni(OH)₂(B)中B的参杂量可达14.6wt%。循环伏安测量和恒电流充放电试验表明,两种电极材料均具有较高的电化学活性和可逆性;在1 A/g的充放电电流密度下, 两种NiO/Ni(OH)₂和NiO/Ni(OH)₂(B)电极材料经历10000次充放电循环后分别给出了1380 和1930F/g的比电容, 显示出较高的比电容特性和良好的电化学稳定性;电化学阻抗谱表明NiO/Ni(OH)₂(B)电极材料较NiO/Ni(OH)₂电化学反应电阻降低了约2个数量级;Ragone曲线揭示了所制备的两种电极材料具有较高的功率密度和较低的能量密度。B的参杂使得NiO/Ni(OH)₂(B)电极材料表面氧化物含量增大并且形成微米微球形貌,增大了电极表面积以及与电解液的接触和润湿作用,降低了电极材料表面能带带隙能,从而导致较小的电化学反应电阻和电导率的提高是其显示优异赝电容性能的主要原因。     

纳米多孔铜银/二氧化锰复合电极材料的制备及储能研究

以Cu-Zr-Ag非晶合金作为前驱体,利用快速凝固技术和脱合金相结合的方法制备纳米多孔铜银双金属(NP-CuAg),通过化学沉淀法使MnO₂在NP-CuAg上形核生长,成功制备出NP-CuAg和MnO₂的复合电极材料(NP-CuAg/MnO₂)。利用XRD、SEM分析材料的相组成及微观形貌,通过循环伏安法和恒流充放电法研究复合电极材料的电容特性。结果表明：兼具三维连续纳米孔洞结构及优异导电性的NP-CuAg作为依附载体可大幅度提高MnO₂颗粒的分散度和电极材料导电性,使其电化学性能得以充分发挥。复合电极材料的比电容值随着前驱体合金中银含量的增加而提高,前驱体合金中Ag含量为10 at.%时电容值可达392.86 F/g。封装成可反复充放电的纽扣型电化学储能器件,可成功对LED灯泡供电。     

Synthesis of porous nano/micro structured LiFePO4/C cathode materials for lithium-ion batteries by spray-drying method

In order to enhance electrochemical properties of LiFePO₄ (LFP) cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The results show that the spherical precursors with the sizes of 0.5–5 μm can be completely converted to LFP/C when the calcination temperature is higher than 500 °C. The LFP/C microspheres obtained at calcination temperature of 700 °C are composed of numerous particles with sizes of ～20 nm, and have well-developed interconnected pore structure and large specific surface area of 28.77 m²/g. The specific discharge capacities of the LFP/C obtained at 700 °C are 162.43, 154.35 and 144.03 mA·h/g at 0.5C, 1C and 2C, respectively. Meanwhile, the capacity retentions can reach up to 100% after 50 cycles. The improved electrochemical properties of the materials are ascribed to a small Li⁺ diffusion resistance and special structure of LFP/C microspheres.     

固相-水热法制备LiFePO4-Li3V2（PO4）3复合材料及其电化学性能（英文）

分别采用固相-水热法和球磨法制备磷酸亚铁锂-磷酸钒锂复合正极材料(LiFePO4-Li3V2(PO4)3)。电化学性能测试表明,LiFePO4-Li3V2(PO4)3复合正极材料的电化学性能远远高于 LiFePO4和 Li3V2(PO4)3单独作为正极材料的性能,并且以固相-水热法制备的复合材料性能优于以球磨法制得的复合材料。研究发现 LiFePO4-Li3V2(PO4)3复合材料有 4 个氧化还原峰,相当于 LiFePO4 和 Li3V2(PO4)3 氧化还原峰的叠加。采用固相-水热法制备的LiFePO4-Li3V2(PO4)3 复合材料形貌较为规则,且有新相物质产生,这是导致其电化学性能较好的原因。     

Improvement of electrochemical and electrical properties of LiFePO<Subscript>4</Subscript> coated with citric acid

LiFePO₄ was synthesized using hydrothermal method and coated with different amounts of citric acid as carbon source.The samples were characterized by X-ray powder diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscope（TEM）,surface area measurement—Brunauer–Emmett–Teller（BET）,discharge capability,cyclic voltammetry（CV）,and electrochemical impedance spectroscopy（EIS）.The results show that the quality and thickness of the carbon coating on the surface of LiFePO₄ particles are very important.The optimum carbon content（about 30 wt%）can lead to a more uniform carbon distribution.Electrochemical results show that the samples containing 20 wt%,30 wt%,40 wt%,and50 wt% carbon deliver a discharge capacity of 105,167,151,and 112 mAhg^-1,respectively,at the rate of 0.1C.The increase of carbon content leads to the decrease of discharge capacity of LiFePO₄/C,owing to the fact that excess carbon delays the diffusion of Li⁺ through the carbon layers during charge/discharge procedure.The LiFePO₄/C with low carbon content exhibits poor electrochemical performance because of its low electrical conductivity.Therefore,the amount of carbon must be optimized in order to achieve excellent electrochemical performance of LiFePO₄/C for its application in a lithium ion battery.     

Synthesis of Li excess LiFePO4/C using iron chloride extracted from steel scrap pickling

Olivine-type Li rich Li_1+xFePO₄/C composites are synthesized by a solid state reaction process using premilled Li₂CO₃ and pre-synthesized amorphous FePO₄·xH₂O powders. The amorphous FePO₄·xH₂O powders are prepared from an industrial waste liquid (by-product), a FeCl₃ (38%) solution, via a precipitation process. In addition, lithium carbonate is pre-milled using a high energy nano mill to control particle sizes and shape differences for enhancing the reaction activity in the starting materials. The main purpose of this study is to investigate the effect of excess Li on the electrochemical properties of LiFePO₄ cathode materials. The pre-synthesized FePO₄ powders are mixed with pre-milled lithium carbonate and glucose (8 wt%) using a ball-mill process. The structural characteristics of the Li_1+xFePO₄/C composites are examined by XRD and SEM. To investigate the effect of excess Li content on the electrochemical properties in Li_1+xFePO₄/C composites, a Li[LiPF₆ (Ethylene carbonate + Dimethyl carbonate)] Li_1+xFePO₄/C model cell is used. It is demonstrated that the 1% Li rich Li/[Li_1.01FePO₄/C] cell exhibits the best electrochemical performance and delivers an initial discharge capacity of 161 mAhg^?1, which is 25 mAhg^?1 higher than that of the Li/[LiFePO₄/C] cell.     

Pb-Co阳极在含氯硫酸电解液中的电化学行为

采用粉末冶金法制备了不同Co含量(0.5%,1.0%,2.0%,质量分数)的Pb-Co阳极,并与传统的Pb-Ca-Sn阳极进行了对比试验。通过电化学测试研究了阳极在160 g/L H₂SO₄、500 mg/L Cl^-电解液中的电化学行为,研究了恒电流极化72 h后阳极氧化层的物相组成、表面形貌和元素分布。随着Co含量的增加,Pb-Co阳极的电位、电荷传递电阻和析氧过电位逐渐降低。恒电流极化72 h后,Pb-2%Co阳极的析氧过电位比Pb-Ca-Sn阳极低101 mV。此外,在Cl-的存在下,电荷传递得到改善,析氧反应受到抑制,阳极氧化层恶化。     

Structure and electrochemical properties of the Fe substituted Ti–V-based hydrogen storage alloys

To elucidate the effects of Fe on the Ti–V-based hydrogen storage electrode alloys, the Ti_0.8Zr_0.2V_2.7−xMn_0.5Cr_0.8Ni_1.0Fe_x (x = 0.0–0.5) alloys were prepared and their structures and electrochemical properties were systematically investigated. XRD results show that all the alloys consist of a C14 Laves phase with hexagonal structure and a V-based solid solution phase with bcc structure. With increasing Fe content, the abundance of the C14 Laves phase gradually decreases from 43.4 wt% (x = 0.0) to 28.5 wt% (x = 0.5), on the contrary, that of the V-based solid solution phase monotonously increases from 56.6 wt% to 71.5 wt%. In addition, SEM observation finds that the grain size of the V-based solid solution phase is first gradually reduced and then enlarged with increasing x. Electrochemical investigations indicate that the substitution of Fe for V markedly improves the cycling stability and the high rate dischargeability of the alloy electrodes, but decreases the maximum discharge capacity and the activation performance. Further electrochemical impedance spectra, the linear polarization curve and the potentiostatic step discharge measurements reveal that the electrochemical kinetics of the alloy electrodes should be jointly controlled by the charge-transfer reaction rate on the alloy surface and the hydrogen diffusion rate in the bulk of the alloys. For the alloy electrodes with the lower Fe content (x = 0.0–0.2), the hydrogen diffusion in the bulk of the alloys should be the rate-determining step of its discharge process, and while x increases from 0.3 to 0.5, the charge-transfer reaction on the alloy surface becomes to the rate-determining step, which induces that the electrochemical kinetics of the alloy electrodes is firstly improved and then decreased with increasing Fe content.     

Electrochemical performance of C-La<Superscript>3+</Superscript> codoped LiFePO<Subscript>4</Subscript> synthesized by microwave heating

La³⁺ was selected to elevate the lattice electronic conductivity of LiFePO₄, and LiFePO₄/(C+La³⁺) cathode powders were synthesized by microwave heating using a domestic microwave oven for 35 min. The microstructures and morphologies of the synthesized materials were investigated by XRD and SEM. The electrochemical performances were evaluated by galvanostatic charge-discharge. The electrochemical performance of LiFePO₄ with different La³⁺ contents was studied. Results indicated that the initial specific discharge capacity of LiFePO₄/(C+La³⁺) composites with 2% La³⁺ (116.3 mAh/g) was better than that of LiFePO₄/C (105.4 mAh/g). The addition of La³⁺ further improved the electrochemical properties. So the codoping is an effective method to improve the electrochemical performance.     

碳黑含量对放电等离子烧结Fe-Cr-C/TiCN复合材料组织和耐磨性的影响

采用机械合金化和放电等离子烧结法制备了不同碳含量的Fe-Cr-C/TiCN复合材料。通过扫描电镜、X射线衍射、维氏硬度和球-盘式摩擦试验,系统地研究了碳含量对Fe-Cr-C/TiCN复合材料组织和磨损性能的影响。结果表明,在含碳量为1.0%~5.0%（质量分数,下同）的烧结样品中形成了(Cr, Fe)₇C₃碳化物,而当碳含量达到4.0%~5.0%时,出现了(Cr, Fe)₃C相。碳含量对Fe-Cr-C/TiCN复合材料的组织均匀性和致密化有着较为重要的影响,当烧结温度为~1000 ℃时,致密度由未加碳时的95.0%提高到的99.7%（含碳量为3.0%）,说明已实现了完全致密化。当含碳量为3.0%时,维氏硬度达到11 940 MPa。此外,添加适量的碳（3.0%）有助于获得良好的磨损性能,即摩擦系数波动范围小,平均摩擦系数为0.320,磨损率为6.8×10^-4 mm³·N^-1·m^-1。     

Characterization and electrochemical properties of carbon-coated Li4Ti5O12 prepared by a citric acid sol-gel method

Since carbon coating can effectively improve electrical wiring of Li₄Ti₅O₁₂ and thus enhance its high rate performance, a novel and simple citric acid sol-gel method for in situ carbon coating is employed in this study. The effects of the amount of the carbon source in the starting xerogel on the particle size, the resistance and the electrochemical performance of the synthesized Li₄Ti₅O₁₂ samples are systematically studied. The physical and electrochemical properties of the obtained samples have been characterized by XRD, TG-DSC, SEM, TEM, BET, A.C. impedance, galvanostatically charge-discharge and cyclic voltammetry tests. The results show that the initial amount of the carbon source in the starting xerogel is a critical factor which determines the content of the coated carbon and the pore volume, therefore governs the high rate performance of the Li₄Ti₅O₁₂/C composites. The Li₄Ti₅O₁₂/C composite with in situ carbon coating of 3.5 wt% exhibits the best electrochemical performance which delivers delithiation capacities of 143.6 and 133.5 mAh g⁻¹ with fairly stable cycling performance even after 50 cycles at 0.5C and 1C rate, respectively.