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。     

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。     

稀土镧掺杂层状锰酸锂正极材料的制备与性能

采用溶胶凝胶法制备层状LiMnO2,并掺杂不同比例的稀土元素进行改性.XRD分析结果表明,掺杂镧元素的层状锰酸锂呈斜方晶系,纯度较高.SEM照片显示这种产物为层状结构,且粒度大小分布较为均匀.用循环充放电测试考察了产物的电化学性能,结果显示掺杂6%La的层状锰酸锂正极材料的初次放电比容量为128 mAh/g,但循环稳定性较差;而掺杂了4%La的层状锰酸锂则表现了良好的循环稳定性,首次放电比容量达到了102 mAh/g,多次充放电之后容量基本没有衰减,仍然能保持较高的比容量.从交流阻抗数据分析,掺镧量为4%的样品扩散阻抗较小,充放电可逆性较好.     

尖晶石锰酸锂制备及其电化学性能的研究

锰酸锂被认为是取代商品锂离子电池正极材料LiCoO2的候选材料,以二氧化锰、碳酸锂为原料,在空气气氛下进行烧结,控制烧结温度和时间,制备锂离子电池正极材料锰酸锂。用X射线衍射仪、电子扫描电镜对产物的结构特征、微观表面形貌和恒流充放电性能进行了表征。结果表明:所制得的正极材料为尖晶石型锰酸锂,结晶度高、无杂质相、材料颗粒的粒径均匀,首次充放电比容量为117.3 mAh/g(0.2C,3.3～4.4V);50次循环后,放电比容量为107.9 mAh/g,不可逆容量损失为9.4 mAh/g,比容量保持率为92.0%,得到了很好的综合电化学性能。     

Ni-B-C对La0.94Mg0.06Ni3.49Co0.73Mn0.12Al0.20储氢合金电化学性能的影响研究

为提高新型AB₃型储氢合金La_0.94Mg_0.06Ni_3.49Co_0.73Mn_0.12Al_0.20的电化学性能,将球磨法制备的Ni-B-C粉末按不同重量比添加到合金中。采用X-射线粉末衍射仪(XRD)和扫描电子显微镜(SEM)分析合金的相结构和表面形貌,添加Ni-B-C粉末后,合金相结构没有变化,仍由LaNi₅相和La₂Ni₇相两个相组成,但合金表面出现了细小颗粒。添加Ni-B-C粉末后,合金电极的最大放电容量和放电容量保持率均提高。当添加重量百分比为10%的Ni-B-C粉末后,电极的最大放电容量从346 mAh/g增加到363 mAh/g,50个循环后的放电容量保持率从70%提高到77%,交换电流密度I₀与极限电流密度I_L分别为106 mA/g和987 mA/g。动电位极化测试表明,电极的抗腐蚀能力也有所增强。研究结果表明,Ni-B-C可以提高AB₃型储氢合金的综合电化学性能。     

Cr3+掺杂LiNi0.5Mn1.5O4材料的制备及性能研究

采用高温固相法合成了Cr₃₊掺杂的LiNi_0.5Mn_1.5O₄正极材料,研究了掺杂量对材料物理性能和电化学性能的影响。利用XRD、SEM对材料的结构和形貌进行了表征,结果显示样品具有棱边清晰的尖晶石形貌。讨论了不同Cr₃₊掺杂量对LiCr_xNi_0.5-0.5xMn_1.5-0.5xO₄(x=0,0.05,0.1,0.15,0.2)正极材料性能的影响。充放电测试、循环伏安和交流阻抗测试结果表明：当Cr₃₊的掺杂量为x=0.1时(LiCr_0.1Ni_0.45Mn_1.45O₄)正极材料的性能最好,0.1C、0.5C、1C、2C及5C的首次放电比容量依次为131.54mAh g_-1、126.84mAh g_-1、121.28mAh g_-1、116.49mAh g_-1和96.82mAh g_-1,1C倍率下循环50次,容量保持率仍为96.5%。     

导电Ti3O5包覆纳米铝粉的制备及其作为双离子电池负极材料的电化学性能研究

铝被认为是下一代电池最有前途的负极材料之一, 本文中采用导电的Ti₃O₅作为外壳包覆纳米铝粉来制备Al@Ti₃O₅核壳结构材料, 并将其作为负极材料应用到双离子电池(DIB)中。使用中间相炭微球(MCMB)作为正极材料,Al@Ti₃O₅作为负极材料制作Al@Ti₃O₅-MCMB双离子电池。电池的放电平台可达4.5V, 在电流倍率0.5C下(电流基于正极石墨的理论比容量计算,1C=372mAhg^_-1)放电比容量达到130.6mAhg^_-1,比能量密度为278.8Whkg^_-1。并且在高倍率5C下循环1000次过程中容量基本保持110mAhg^_-1不变,循环后容量保持率达到92.9%。     

用于锂离子电池的多孔珊瑚状硅/碳复合负极材料的合成、表征及电化学性能(英文)

利用PVA碳源包覆、HF酸刻蚀和沥青二次包覆方法制备多孔珊瑚状硅/碳复合负极材料,得到沥青含量分别为30%、40%和50%(质量分数)的3种硅/碳复合材料样品。采用XRD和SEM分别对复合材料的组成和形貌进行表征,并采用电化学测试手段对其性能进行测试。结果表明,经二次沥青包覆后,复合材料的电化学性能得到明显提高。当二次包覆的沥青含量为40%时,在100 m A/g的电流密度下,该样品第二次充放电循环的放电容量达到773 m A·h/g,经60次循环后,放电容量仍然保持在669 m A·h/g,其容量损失率仅为0.23%/cycle。因此,调整二次包覆碳含量可明显改善复合材料的循环稳定性。     

新型锂蓄电池正极复合材料的制备和电化学性能研究

采用升华硫与多壁碳纳米管在一定条件下合成了一种新型纳米含硫复合材料。通过扫描电子显微镜（SEM）和BET比表面积等分析测试手段对复合材料的物理化学性能进行表征，利用循环伏安、交流阻抗和电池充放电对材料的电化学性能进行了测试。结果表明：此复合材料表现出了很好的电化学性能，其初始放电比容量达700mAh／g，在室温下经过60次循环之后电池放电比容量仍稳定在464mAh／g，容量保持率大于66％。     

氮掺杂及PEG包覆对CNT/S材料储锂性能的影响

以硫代氨基脲为氮源,用高温退火法对碳纳米管实现氮掺杂,利用PEG对掺氮复合材料(NCNT/S)进行外包覆。采用X射线衍射仪(XRD),扫描电子显微镜(SEM),X射线光电子能谱仪(XPS)对复合材料进行了表征。结果表明高温退火使氮有效地掺入碳纳米管中,而碳纳米管仍保持原本征形貌。电化学测试表明:掺氮后复合电极首次放电比容量明显提高,达到882.5 mAh·g~(-1),90次循环过后具有89.46%的容量保持量,而PEG包覆使掺氮复合电极首次放电比容量提高至1109.7 mAh·g~(-1),经过90次循环放电比容量仍保持在995.2 mAh·g~(-1)。这说明掺氮和PEG包覆均能很好地改善复合材料的电化学性能。     

Effects of K2O-Li2O doping on surface and catalytic properties of Fe2O3/Cr2O3 system

The effects of K₂O and Li₂O-doping (0.5, 0.75 and 1.5 mol%) of Fe₂O₃/Cr₂O₃ system on its surface and the catalytic properties were investigated. Pure and differently doped solids were calcined in air at 400-600 °C. The formula of the un-doped calcined solid was 0.85Fe₂O₃:0.15Cr₂O₃. The techniques employed were TGA, DTA, XRD, N₂ adsorption at −196 °C and catalytic oxidation of CO oxidation by O₂ at 200-300 °C. The results revealed that DTA curves of pure mixed solids consisted of one endothermic peak and two exothermic peaks. Pure and doped mixed solids calcined at 400 °C are amorphous in nature and turned to α-Fe₂O₃ upon heating at 500 and 600 °C. K₂O and Li₂O doping conducted at 500 or 600 °C modified the degree of crystallinity and crystallite size of all phases present which consisted of a mixture of nanocrystalline α- and γ-Fe₂O₃ together with K₂FeO₄ and LiFe₅O₈ phases. However, the heavily Li₂O-doped sample consisted only of LiFe₅O₈ phase. The specific surface area of the system investigated decreased to an extent proportional to the amount of K₂O and Li₂O added. On the other hand, the catalytic activity was found to increase by increasing the amount of K₂O and Li₂O added. The maximum increase in the catalytic activity, expressed as the reaction rate constant (k) measured at 200 °C, attained 30.8% and 26.5% for K₂O and Li₂O doping, respectively. The doping process did not modify the activation energy of the catalyzed reaction but rather increased the concentration of the active sites without changing their energetic nature.     

Sinterability and dielectric properties of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 composite ceramics

The composite ceramics of Ba_0.55Sr_0.4Ca_0.05TiO₃-CaTiSiO₅-Mg₂TiO₄ (BSCT-CTS-MT) were prepared by the conventional solid-state route. The sintering performance, phase structures, morphologies, and dielectric properties of the composite ceramics were investigated. The BSCT-CTS-MT ceramics were sintered at 1100 °C and possessed dense microstructure. The dielectric constant was tailored from 1196 to 141 as the amount of Mg₂TiO₄ increased from 0 to 50 wt%. The dielectric constant and dielectric loss of 40 wt% Ba_0.55Sr_0.4Ca_0.05TiO₃-10 wt% CaTiSiO₅-50 wt% Mg₂TiO₄ was 141 and 0.0020, respectively, and the tunability was 8.64% under a DC electric field of 8.0 kV/cm. The Curie peaks were broadened and depressed after the addition of CaTiSiO₅. The optimistic dielectric properties made it a promising candidate for the application of tunable capacitors and phase shifters.     

Low temperature sintering and microwave dielectric properties of (Mg0.7Zn0.3)0.95Co0.05TiO3 ceramics with BaCu(B2O5) additions

The effects of BaCu(B₂O₅) additives on the sintering temperature and microwave dielectric properties of (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics were investigated. The (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics were not able to be sintered below 1000 °C. However, when BaCu(B₂O₅) were added, they were sintered below 1000 °C and had the good microwave dielectric properties. It was suggested that a liquid phase with the composition of BaCu(B₂O₅) was formed during the sintering and assisted the densification of the (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics at low temperature. BaCu(B₂O₅) powders were produced and used to reduce the sintering temperature of the (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics. Good microwave dielectric properties of Q × f = 35,000 GHz, ?_r = 18.5.0 and τ_f = −51 ppm/°C were obtained for the (Mg_0.7Zn_0.3)_0.95Co_0.05TiO₃ ceramics containing 7 wt.% mol% BaCu(B₂O₅) sintered at 950 °C for 4 h.     

Sol-gel synthesis of Bi3.25La0.75Ti3O12 nanotubes

Ferroelectric Bi_3.25La_0.75Ti₃O₁₂ (BLT) nanotubes were synthesized by sol-gel technique using nanochannel porous anodic aluminum oxide (AAO) templates, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). BLT nanotubes with diameter of around 240 nm and the wall thickness of about 25 nm exhibited a single orthorhombic perovskite structure and highly preferential crystal growth along the [1 1 7] orientation, which have smooth wall morphologies and well-defined diameters corresponding to the diameter of the applied template. The formation mechanism of BLT nanotubes was discussed.     

Preparation and characteristic of spherical Li3V2(PO4)3

Spherical Li₃V₂(PO₄)₃ was synthesized by using N₂H₄ as reducer. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that single-phase, spherical and well-dispersed Li₃V₂(PO₄)₃ has been successfully synthesized in our experimental process. Electrochemical behaviors have been characterized by charge/discharge measurements. The initial discharge capacities of Li₃V₂(PO₄)₃ were 123 mAh g⁻¹ in the voltage range of 3.0–4.3 V and 132 mAh g⁻¹ in the voltage range of 3.0–4.8 V.     

FRICTION WELDING OF Zr55Al10Ni5Cu30 BULK METALLIC GLASS

采用摩擦焊对Zr₅₅Al₁₀Ni₅Cu₃₀块体金属玻璃进行了焊接, 当焊机主轴转速为4.0×10³---5.0×10³ r/min, 摩擦压力为80---100 MPa, 摩擦时间为0.2---0.4 s, 顶锻压力和保压时间分别为200 MPa和2 s时, 能够成功实施Zr₅₅Al₁₀Ni₅Cu₃₀金属玻璃的焊接. 用SEM, XRD和TEM观察分析未检测到晶化相, 焊缝处金属仍保持非晶状态. 金属玻璃的塑性在玻璃转变点T_g附近随温度变化很大, 在T_g以上具有良好的塑性变形能力, 这是实施摩擦焊焊接的重要基础.     

废旧锂离子电池中Li, Fe和V的回收及xLiFePO4-yLi3V2(PO4)3的制备

由于LiFePO_4和Li_3V_2(PO_4)_3材料的特征相近,制备方法类似,提供了一种从废旧LiFePO_4和Li_3V_2(PO_4)_3混合电池中回收Li、Fe和V,再制备xLiFePO_4-yLi_3V_2(PO_4)_3的方法。在空气气氛中600℃热处理1h后,去除粘结剂PVDF使活性物质与集流体分离。调节Li、Fe、V和P摩尔比,球磨、锻烧,配制不同比例的xLiFePO_4-yLi_3V_2(PO_4)_3(x:y=5:1,7:1,9:1)复合电极材料。表征了其形貌、结构和电化学性能,结果表明,回收制备的复合材料将同时具备LiFePO_4和Li_3V_2(PO_4)_3两种材料的电化学性能,能显著改善LiFePO_4的倍率性能。     

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。     

二维ZnO/ Bi3.9Zn0.4V1.7O10.5纳米异质结构的制备及其可见光催化活性

表面建造是提高半导体光催化活性的一种有效方法。本文利用Zn5(CO3)2(OH)6纳米片为基底沉积了BiVO4再通过煅烧成功制备了二维ZnO/Bi3.9Zn0.4V1.7O10.5复合纳米片。通过X射线衍射,透射电镜和元素映像技术表征了所制样品。结果显示随着锌与铋的原子比的上升,ZnO多孔片状的表面逐渐变成Bi3.9Zn0.4V1.7O10.5物质。但其比例高于1:0.02时,在片状Bi3.9Zn0.4V1.7O10.5的区域表面又生长出BiVO4纳米颗粒。漫反射光谱测试显示出ZnO/Bi3.9Zn0.4V1.7O10.5复合物随着锌与铋的原子比的上升其在400~600 nm可见光区的吸收逐渐增强。所制样品在可见光（波长大于420 nm）进行了光催化降解罗丹明B的测试,结果表明在所制样品中,锌与铋的原子比为1:0.0133的ZnO/Bi3.9Zn0.4V1.7O10.5纳米片虽然其可见光的吸收并没有明显增强但却表现出最佳的光催化活性。荧光与电化学测试得出了低含量BZVO的ZnO纳米片可见光催化活性的提高主要是因为表面ZnO/Bi3.9Zn0.4V1.7O10.5异质结构提高了光生载流子的分离与传送。这种二维材料的表面建造有利于光催化的进行。因此,此法可应用于其它二维纳米材料的建造以提高光催化活性。     

Synthesis and characterization of Y3Al5O12 and ZrO2-Y2O3 thermal barrier coatings by combustion spray pyrolysis

Y₃Al₅O₁₂ and ZrO₂-Y₂O₃ (8 mol% YSZ) coatings for potential application as thermal barrier coatings were prepared by combustion spray pyrolysis. Thermal cycling of as deposited coatings on stainless steel and FeCrAlY bond coat substrates was carried out at 1000 °C and 1200 °C to determine the thermal fatigue response. Structural and morphological studies on Y₃Al₅O₁₂ and 8 mol% YSZ coatings before and after thermal cycling have been carried out. It has been noted that the coatings on FeCrAlY substrates remain intact after 50 cycles between room temperature and 1200 °C, whereas the coatings on stainless steel show some minor damage such as peeling off near the periphery after 50 cycles at 1000 °C. Thermal diffusivity values of Y₃Al₅O₁₂ and 8 mol% YSZ films were measured by using photo thermal deflection spectroscopy and the values are lower than those of coatings produced by conventional techniques such as EBPVD and APS.