Rb掺杂Li4Ti5O12作为锂离子电池负极材料的合成及电化学性能

合成了不同Rb掺杂量的钛酸锂（Li_4-xRb_xTi₅O₁₂; x = 0.010, 0.015, 0.020）作为锂离子电池的负极材料。测试结果显示,Rb离子掺杂有效增强了钛酸锂的电子电导率。相同的测试条件下,相比于未掺杂样品和高Rb含量掺杂样品（x = 0.015, 0.020）,适量的Rb掺杂钛酸锂（Li_3.99Rb_0.01Ti₅O₁₂; x = 0.010）表现出最优的电化学性能。Li_3.99Rb_0.01Ti₅O₁₂材料表现出161.2 mA∙h/g的初始容量,且在1 C下经过1000次循环后容量保持率可达90.9%。此外,全电池Li_3.99Rb_0.01Ti₅O₁₂ // LiFePO₄在0.5 C条件下首次放电容量为144 mA∙h/g,经过150次循环后,容量保持率为78.8%。     

Capacitive performance and cycling stability of NixCo1-x(OH)2 xerogels

研究了Ni_xCo_1-x(OH)₂干凝胶中钴含量对其电性能及循环稳定性的影响。用溶胶-凝胶法制备了Ni_xCo_1-x(OH)₂干凝胶材料,用液氮吸附、XPS和XRD研究了含钴Ni(OH)₂干凝胶的组成和结构,用恒电流技术研究了它们的电容性能。结果表明,Ni_xCo_1-x(OH)₂干凝胶具有较高的比表面积和丰富的中孔;添加钴改善了Ni_xCo_1-x(OH)₂干凝胶的倍率性能,当钴含量达到24%时效果最佳;充放电后Co_xNi_1-x(OH)₂干凝胶的晶态结构仍是β-Ni(OH)₂晶相结构,钴含量20%以上的Co_xNi_1-x(OH)₂干凝胶充放电后微晶尺寸变化不明显;组成的活性炭/ Ni_0.76Co_0.24(OH)₂干凝胶电容器20 mA/cm²充放电循环时,库仑效率达到95%以上,循环100000次以上,电容器的比容量仍保持在90%以上。在长循环过程中,Ni_0.76Co_0.24(OH)₂干凝胶的微晶尺寸变化不大,微晶晶胞a轴逐渐变大、c轴逐渐缩小,晶胞参数趋向理想的β-Ni(OH)₂晶体。     

Synthesis of LiNi0.8Co0.2O2 cathode material through sintering in an air environment and electrochemical properties characterization

制备锂离子电池正极材料LiNi_0.8Co_0.2O₂通常需要在纯氧气气氛下进行烧结.本工作以硫酸镍,硫酸钴和氢氧化钠为原料,采用并流共沉淀法制备了高密度Ni_0.8Co_0.2(OH)₂前驱体,再采用高温固相反应法在空气中烧结制备了锂离子电池LiNi_0.8Co_0.2O₂正极材料.采用X射线衍射(XRD),扫描电镜(SEM),恒流充放电测试(ECT),循环伏安(CV)与比表面积(BET)测试等方法对目标样品进行了表征,详细考察了烧结条件对材料结构,微观形貌及电化学性能的影响.结果表明,锂/(钴+镍)摩尔比为1.13∶1时,在管式炉中和空气气氛下于第一段烧结温度700 ℃保温9 h,于第二段烧结温度750 ℃保温12 h,合成的材料比表面积适中(0.78 m²/g),具有规则的六边形α-NaFeO₂层状结构,晶粒分布均匀,电化学性能最优.在0.5 C充放电倍率下和2.7~4.3 V电压范围内,其首次放电比容量达到153.0 mA·h/g,循环20次后放电比容量仍为150.7 mA·h/g,容量保持率达到98.5%,显示了优异的循环稳定性能,可用做高能量密度动力电池正极材料.     

Preparation of LiNi0.80Co0.15Al0.05O2 cathode material via Li-rich method

本文采用共沉淀法制备球形Ni_0.80Co_0.15Al_0.05(OH)_2.05前驱体,经预氧化后,采用富锂配比在氧气和空气气氛下烧结合成LiNi_0.80Co_0.15Al_0.05O₂正极材料.用X射线衍射,扫描电镜和恒电流充放电测试等方法对该材料的结构,形貌及电化学性能进行表征.结果表明:当锂配比为1.15时,氧气和空气中烧结合成的LiNi_0.80Co_0.15Al_0.05O₂正极材料的形貌,结构和电化学性能相当.富锂配比方法可在空气气氛下制备出电化学性能优异的LiNi_0.80Co_0.15Al_0.05O₂正极材料.0.1 C放电克比容量在200 mA·h/g以上,首次效率在87%左右;1 C放电克比容量在168 mA·h/g以上;800周循环容量保持率在80%以上.     

Preparation,electrochemical performance and phase transition of high voltage LiNi0.5Mn1.5O4 cathode material

尖晶石LiNi_0.5Mn_1.5O₄因其可在4.7 V高电位下工作并有良好的循环特性,已成为最具潜力的高能量密度锂离子电池正极材料。本文首先采用喷雾干燥辅助烧结法制备了LiNi_0.5Mn_1.5O₄正极材料,考察了热处理条件对材料结构与性能的影响。用XRD、SEM和FT-IR等技术对所制备的LiNi_0.5Mn_1.5O₄材料的结构和表面形貌进行表征,利用原位XRD技术研究了LiNi_0.5Mn_1.5O₄正极材料在充放电过程中结构相变规律。结果表明,所制备的LiNi_0.5Mn_1.5O₄材料均具有Fd-3m空间群的立方相尖晶石型结构,并具有优异的电化学性能,其0.1 C时首次放电容量为132 mA·h/g,首轮库仑效率93.48%,高倍率下该材料的电化学性能优越。原位XRD测量结果分析表明,尖晶石型LiNi_0.5Mn_1.5O₄材料在充电过程中存在4个显著的相变过程,在嵌脱锂过程中,从四面体相向立方相结构相变过程是可逆的。     

High specific capacity composite cathode materials for lithium-sulfur batteries

Li与S完全反应生成Li₂S时,单质硫正极的理论比容量为1675 mA·h/g,比LiFePO₄,LiCoO₂等正极材料的比容量高很多.单质S价格低,无毒,是一种理想的正极材料,然而其导电性较低,循环比容量衰减较快,因此需要改善S正极材料的导电性来提高其电化学性能.本文综述了硫基复合正极材料的制备方法,结构与形貌,电化学性能.探讨了S与多孔碳,碳纳米管,石墨烯和聚吡咯等复合的正极材料的电化学性能,并对硫基正极材料的发展趋势进行了展望.     

The cycle life investigation for spinel LiNi0.5Mn1.5O4 full cells

分别以石墨和钛酸锂为负极活性物质,制备了尖晶石镍锰酸锂的32131型圆柱锂离子电池.石墨负极电池和钛酸锂负极电池容量分别为7.5 A·h和5.5 A·h,质量能量密度分别达到152 W·h/kg和81 W·h/kg.常温充放电循环测试结果表明,石墨和钛酸锂两种负极体系电池循环寿命将分别达到400次和1000次,这种循环寿命的差别主要体现在负极上,即正极材料中溶解的Mn在石墨负极表面沉积并持续催化SEI膜生成,减少了电池中可使用的活性Li⁺,进而导致电池寿命快速衰减;相比而言,钛酸锂负极表面不存在明显SEI,同时正极过量设计电池也使得钛酸锂体系电池的镍锰酸锂与电解液间的界面副反应低于石墨体系的负极过量设计电池.     

铁酸铜尖晶石催化甲醛氧化的性能研究

通过溶胶-凝胶-自蔓延燃烧法制备了系列Cu_xFe_3-xO₄尖晶石催化剂。采用XRD和XPS表征方法对催化剂晶相结构及表面元素价态进行了分析,考察了Cu_xFe_3-xO₄催化甲醛的氧化效率。采用密度泛函理论探究了甲醛吸附在CuFe₂O₄表面的最稳定构型和吸附机理。结果表明,Cu_xFe_3-xO₄催化剂主要由Cu-Fe尖晶石相和部分CuO、Fe₂O₃相组成。Cu_0.5Fe_2.5O₄催化甲醛氧化效率最佳,在温度高于250℃时氧化效率达到90%以上。甲醛在CuFe₂O₄(100)表面的吸附属于化学吸附,吸附能为 -107.15 kJ/mol。     

Simulation of the effects of electrode parameters on all-vanadium redox flow battery performance

以全钒液流电池为研究对象,利用电池内部传递与反应相耦合的机理模型,模拟电池二维,等温,稳态条件下,电池充电过程电极参数对电池内部极化的影响规律,包括碳毡电极的几何结构参数(厚度Lt和压缩比CR),电学特性参数(比表面积a和电导率)和操作参数(充电电流密度i)的影响.数值模拟结果给出Lt从1.5 mm增至3.5 mm,端电压仅降低3 mV;CR从0.1增至0.5,端电压降低16 mV;a从3.5×10⁴ m²/m³增至3.5×106 m²/m³,端电压降低30 mV;从18.9 S/m增至164.4 S/m,端电压降低87 mV,并给出多孔电极内部过电势在不同条件下不同的二维分布特点;i从100 mA/cm²增至150 mA/cm²,端电压增大57 mV,若同比增大比表面积a,则端电压只增大46 mV.将数值模拟与宏观实验相对比,取得良好的一致性,表明了数值模拟与分析的可靠性.通过增大CR,a,可以明显提高电池性能,为进一步提高电极材料的性能,设计电极结构参数,选择操作参数提供了重要依据.     

加热和水处理共同调控PbI2薄膜形貌及其在钙钛矿太阳电池中的应用研究

该文研究加热和水处理共同作用对PbI₂薄膜形貌的调控和对钙钛矿太阳电池性能的影响。使用的钙钛矿体系为（FAPbI₃）_1-x（MAPbBr₃）_x,并在两步法工艺基础上对PbI₂薄膜进行不同时间加热和短时间水处理可将PbI₂薄膜制备成多孔结构。将双重处理后的PbI₂薄膜制备成钙钛矿薄膜后,可发现钙钛矿薄膜质量明显提升,表现在：钙钛矿的晶粒尺寸明显增大、结晶性增强、吸光能力提升、载流子传输更快。且此种方式能有效调控钙钛矿薄膜中的PbI₂残留量。在器件效率方面,只对PbI₂薄膜进行加热处理制备的电池的开路电压、短路电流、填充因子和效率分别为1.05 V、23.12 mA/cm²、73.81%和17.92%,而在最优双重处理工艺下制备的电池的这4个相应的参数分别为1.09 V、24.75 mA/cm²、77.85%和21.10%。     

Structural and electrochemical properties of Li1+xNi0.5Mn0.5O2+δ (0 ≤ x ≤ 0.7) cathode materials for lithium-ion batteries

A comparative analysis of the properties of LiNi_0.5Mn_0.5O₂ and Li_1+xNi_0.5Mn_0.5O₂ (0.2 ≤ x ≤ 0.7) powders, obtained by the freeze drying method, was performed. Lattice parameters of Li_1+xNi_0.5Mn_0.5O₂ decreased considerably with growing amounts of Li until x = 0.3; at x > 0.5 trace amounts of Li₂MnO₃ are observed by X-ray diffraction (XRD) patterns. X-ray photoelectron spectroscopy (XPS) analysis displayed an increase of Ni³⁺/Ni²⁺ ratio at 0.3 < x < 0.5, while Mn 2p spectra were almost identical in all samples. Rechargeable capacity values (V = 2.5–4.6 V) increased systematically with x reaching its maximum (185–190 mAh g⁻¹) at x = 0.5. Samples with superstoichiometric lithium content also demonstrated good C rate characteristics.     

Predictions of the optimum ternary alkali-carbonate electrolyte composition for MCFC by computational calculation

Various kinds of phase diagrams for Li–Na–K ternary carbonate systems were plotted and the vapor pressures of chemical species such as alkali cations and oxygen molecule at various compositions and various temperatures were calculated by computational manipulation of thermodynamic databases. The liquidus temperature of (Li_0.52Na_0.48)₂CO₃–(Li_0.62K_0.32)₂CO₃, (Li_0.62K_0.32)₂CO₃–(Li_0.44Na_0.30K_0.26)₂CO₃, and (Li_0.44Na_0.30K_0.26)₂CO₃–(Li_0.52Na_0.48)₂CO₃ binary systems decrease with the increase of Li₂CO₃ content without any ternary intermediate compound. Total vapor pressure of alkali metal species governed by the summation of the vapor pressure of free Na and K and the vapor pressure of alkali metal species starts to decrease abruptly when the content of (Li_0.52Na_0.48)₂CO₃ is over 70 mol% in (Li_0.52Na_0.48)₂CO₃–(Li_0.62K_0.32)₂CO₃ system while over 50 mol% in (Li_0.44Na_0.30K_0.26)₂CO₃–(Li_0.52Na_0.48)₂CO₃ system. On the contrary, the equilibrium vapor pressure of oxygen molecule abruptly increases at the same composition range.     

Preparation and characterization of PEO based Li1.5Al0.5Ge1.5(PO4)3 solid composite electrolyte

以聚环氧乙烷（PEO）为黏结剂,离子导电性的Li_1.5Al_0.5Ge_1.5(PO₄)₃（LAGP）为主相,乙腈为溶剂,按照EO/Li,摩尔比为13,变化LiN(CF₃SO₂)₂（LiTFSI）中Li⁺ 与LAGP中Li⁺ 的比例,通过溶液浇注法制备得到LAGP-PEO(LiTFSI)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(LiTFSI)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(LiTFSI)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(LiTFSI) 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。     

Al2O3/SiOxNy/SiNx叠层钝化膜对PERC太阳电池性能及LID效应的研究

由于等离子体增强化学的气相沉积（PECVD）法制备的SiO_xN_y薄膜中含有大量H原子,因而具有优异的表面钝化性能。通过在PERC太阳电池的Al₂O₃/SiN_x背钝化叠层中间插入一层SiO_xN_y薄膜,形成Al₂O₃/SiO_xN_y/SiN_x结构,可避免SiN_x所带的固定正电荷对Al₂O₃负电荷场钝化效应的负面影响。试验结果表明,硅片少子寿命从原来的130 μs提高至162 μs,电池转换效率增加0.09%。同时,基于Al₂O₃/SiO_xN_y/SiN_x背钝化的PERC太阳电池的LID也得到了改善,由对照组的1.83%下降到实验组的1.09%。     

镍钴锰酸锂电极材料改性研究进展

镍钴锰酸锂（LiNi_xCo_yMn_1-x-yO₂,NCM）是一种具有高使用容量的三元正极材料,但存在元素混排、相变、热稳定性差、微裂纹等缺陷,导致电池出现容量衰减和安全问题,影响其广泛应用。针对目前三元材料存在的问题,归纳总结了特殊结构与形貌、掺杂、替代、包覆、修饰、复合等改性方法的最新研究进展,探讨了不同方法对材料电化学性能、循环稳定性和安全性的影响,分析比较了不同方法的优缺点。结合材料、电化学、热和力等多学科知识及本课题组利用负热膨胀材料对能源材料改性的研究成果,提出了原位利用电极循环过程中的热调控形变和界面行为改善材料性能的新思路,为解决电池的热失控和应力等安全问题提供参考。     

Selective removal of CO from hydrogen-rich stream over CuO/CexSn1−xO2–Al2O3 catalysts

The solid solutions of Ce_xSn_1−xO₂ incorporated with alumina to form Ce_xSn_1−xO₂–Al₂O₃ mixed oxides, by the suspension/co-precipitation method, were used to prepare CuO/Ce_xSn_1−xO₂–Al₂O₃ catalysts for the selective oxidation of CO in excess hydrogen. Incorporating Al₂O₃ increased the dispersion of Ce_xSn_1−xO₂, but did not change their main structures and did not weaken their redox properties. Doping Sn⁴⁺ into CeO₂ increased the mobility of lattice oxygen and enhanced the activity of the 7%CuO/Ce_xSn_1−xO₂–Al₂O₃ catalyst in the selective oxidation of CO. The selective oxidation of CO was weakened as the doped fraction of Sn⁴⁺ exceeded 0.5. Incorporating appropriate amounts of Sn⁴⁺ and Al₂O₃ could obtain good candidates 7%CuO/Ce_xSn_1−xO₂–Al₂O₃(20%), 1–x=0.1–0.5, for a preferential oxidation (PROX) unit in a polymer electrolyte membrane fuel cell system for removing CO. Its activity was comparable with, and its selectivity was much larger than, that of the noble catalyst 5%Pt/Al₂O₃.     

铁基载氧体的污泥化学链气化过程中氮迁移热力学模拟与实验研究

基于吉布斯自由能最小化原理,采用HSC Chemistry 6.0软件,对污泥化学链气化过程中NO_x前驱物（NH₃和HCN）与Fe₂O₃载氧体的氧化还原行为进行了热力学模拟。基于污泥热解实验中NO_x前驱物的含量,计算载氧体与污泥的摩尔比（OC/SS）对NH₃、HCN以及NH₃和HCN混合气氧化过程的影响。热力学模拟结果表明：Fe₂O₃能显著促进NO_x前驱物的氧化和裂解,主要生成N₂,几乎无NO_x生成;当NH₃、HCN以及混合气（NH₃和HCN）分别作为还原剂时,其最优OC/SS分别为0.02、0.04和0.05;由于HCN还原性强于NH₃,其氧化速率较快。基于Fe₂O₃/Al₂O₃混合物（FeAl）载氧体,实验对比了污泥化学链气化与污泥热解过程中NO_x前驱物的释放特性,发现Fe₂O₃能显著降低烟气中NO_x前驱物的产率,NH₃和HCN产率分别下降32%和62%。实验结果与热力学模拟结果一致。     

Preparation of spinel LiMn2O4 by supercritical hydrothermal method with heat-treatment

利用超临界水热结合后续煅烧处理的方法制备了锂离子电池正极材料LiMn₂O₄,并详细讨论了超临界水热反应过程中反应压力、反应温度和后续处理煅烧温度对LiMn₂O₄材料晶型、颗粒形貌和电化学性能的影响。实验结果表明,LiMn₂O₄材料在400 ℃、30 MPa下反应15 min,后续经过700 ℃煅烧3 h得到的样品具有结晶度良好、颗粒分布均匀等优点。LiMn₂O₄材料制备的扣式电池表现出优异的电化学性能,0.1 C倍率下初始放电比容量为125 mA·h/g;1 C下循环50周同样表现出良好的电化学性能。     

地热驱动氨水吸收式动力/制冷复合循环参数优化分析

针对中低品位地热驱动的氨水吸收式动力/制冷复合循环的热力学性能展开分析与优化,在Kalina循环的基础上利用氨水变温蒸发的特性,将正向动力子过程与逆向制冷子过程耦合,对外实现动力与冷量的联供。本文对影响复合循环热力性能的工质对浓度x_w/x_b、氨水发生温度（露点温度）t₁₄、循环倍率K以及分流比n四个重要参数展开了分析优化。研究表明,在x_w/x_b=0.50/0.32、t₁₄=180℃、K=2.80和n=0.505的优化工况下,复合循环的热效率和?效率分别可达19.38%和59.77%,较氨水动力循环分别高出3.71%和4.74%,较水蒸气朗肯循环分别高出8.54%和35.81%。     

Electrochromic properties of lithiated Co-oxide (LixCoO2) and Ni-oxide (LixNiO2) thin films prepared by the sol–gel route

Layered Li_xCoO₂ and Li_xNiO₂ thin films (x1) were prepared by a peroxo wet chemistry route from Li(I), Co(II) and Ni(II) acetate precursors and the addition of H₂O₂. Structural changes during the processing of xerogel to final oxide were followed by X-ray diffraction and infrared spectroscopy. Electrochromic properties were determined with in-situ potentiodynamic, potentiostatic and galvanostatic spectroelectrochemical measurements. Single dipped films with composition Li_0.99Co_1.01O₂ or Li_0.94Ni_1.06O₂ exhibited stable voltammetric response in 1 M LiClO₄/propylene carbonate electrolyte after about 60 cycles. The total charge exchanged in a reversible charging/discharging cycle was about ±30 mC cm⁻² for Li_0.99Co_1.01O₂ and ±20 mC cm⁻² for Li_0.94Ni_1.06O₂ oxide films. Galvanostatic measurements showed that about 1/2 (x0.5) and 2/3 (x0.3) of Li⁺ ions could be reversibly removed from the structure of Li_0.99Co_1.01O₂ and Li_0.94Ni_1.06O₂ films, respectively. Practical applicability of Li_0.99Co_1.01O₂ and Li_0.94Ni_1.06O₂ oxide films was studied in electrochromic devices with WO₃(H⁺)Li⁺ormolyteLi_0.99Co_1.01O₂ and WO₃(H⁺)Li⁺ormolyteLi_0.94Ni_1.06O₂ configuration. The monochromatic transmittance T_s (λ=633 nm) of dark blue coloured devices was extremely low (T_s3%), whereas in bleached state the value reached around T_s70%.