1,3-二氧戊环基LiCF3SO3电解液对锂硫电池正极材料单质硫的电化学性能影响

测试了二元和多元溶剂组分的1,3-二氧戊环基LiCF3SO3电解液的粘度、离子电导率和单质硫的溶解度. 研究结果表明, 由较强的给电子能力溶剂组成的低粘度电解液较容易提高单质硫的氧化还原反应活性和可逆性能, 有利于提高单质硫在2.10 V附近的低放电平台电位和放电比容量. DOL-DME LiCF3SO3电解液能够较好地改善单质硫电极的表面钝化层结构, 促进电活性物质离子扩散和降低界面电荷传递阻抗, 从而表现出很好的放电倍率特性. 在室温下充放电流密度分别为0.1和0.2 mA/cm2时, 单质硫的首次放电比容量为792 mA·h/g, 第29次放电比容量达到412 mA·h/g.     

Li＋在PC＋DMF混合溶剂中优先溶剂化的13C NMR研究

利用¹³C NMR光谱技术研究了Li^＋在碳酸丙烯酯(PC)＋N,N-二甲基甲酰胺(DMF)混合溶剂中的优先溶剂化现象. 根据溶剂分子中碳原子的化学位移随锂盐浓度的变化关系, 确定了与Li^＋发生配位的原子. 碳原子的配位位移值随混合溶剂组成的变化关系表明, 在LiClO₄＋PC＋DMF混合物中, DMF分子对Li^＋的溶剂化作用较PC分子强. 定量计算得到, 在n(PC)∶n(DMF)＝1∶1(摩尔比)的混合溶剂中, PC与DMF分子数在Li^＋第一溶剂化层中的比率为0.12, 说明Li^＋优先被DMF分子溶剂化.     

正交相MoO3的制备、表征及其电化学嵌锂性质

用化学沉淀-水热法在较低的温度下制备了片状正交相MoO3,由XRD、FT-IR、XPS和SEM表征了产物的相态、结构、成分和形貌。电化学测试表明,在0.1mA.cm-2的电流密度和1.2~3.5V电压范围,其初始放电容量为663mA.h.g-1,有望成为理想的锂离子插层材料。     

MnO2上氧气第一个电子转移步骤的从头计算研究

采用裸露簇和嵌入簇模型, 对β-MnO₂ (001), (110), (111)三个晶面以及O₂在(110)晶面的单址吸附模式(Pauling和Griffths模式), 进行从头计算. 从β-MnO₂ (001), (110), (111)三个晶面的电子结构差异以及O₂在(110)晶面吸附的吸附能、几何结构、集居数以及净电荷数分析得到: (001), (110), (111)三个晶面中(110)晶面的催化活性最高, 其活性顺序为(110)＞(111)＞(001). 氧气在(110)晶面的吸附, Pauling和Griffths两种吸附模式均存在, 属于化学吸附中的离子吸附. 氧气与MnO₂固体间发生了单电子转移, 氧气得到电子被还原成O₂^-, 转移电子属于整个体系, 具有离域性.     

层状LiMnO2的溶胶凝胶法合成及其改性

采用溶胶凝胶法合成了锂离子电池正极材料层状锰酸锂(o-L iMnO2),并对其进行了N i2+掺杂改性研究,优化了层状L iMnO2的合成路径及制备条件.采用XRD、充放电实验和交流阻抗测试方法研究了N i2+的掺入对o-L iMnO2充放电容量的影响.结果表明N i2+的掺入明显提高了锰酸锂的放电比容量和循环性能,抑制了循环过程中电池阻抗的增加.     

PREPARATION AND ELECTROCHEMICAL CHARACTERISTICS OF POLYMER ELECTROLYTE MEMBRANES BASED ON SAN/PVDF-HFP BLENDS

A copolymer of poly(acrylonitrile-co-styrene) (SAN) was synthesized via an emulsion polymerization method. Novel polymer electrolyte membranes cast from the blends of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), SAN and fumed silica (SiO2) are microporous and can be used in polymer lithium-ion batteries. The membrane shows excellent characteristics such as high ionic conductivity and good mechanical strength when the mass ratio between SAN and PVDF-HFP and SiO2 is 3.5/31.5/5. The ionic conductivity of the membrane soaked in a liquid electrolyte of 1 mol/L LiPF6/EC/DMC/DEC is 4.9×10-3 S cm-1 at 25℃. The membrane is electrochemical stable up to 5.5 V versus Li /Li in the liquid electrolyte. The influences of SiO2 content on the porosity and mechanical strength of the membranes were studied. Polymer lithium-ion batteries based on the membranes were assembled and their performances were also studied.     

Electrochemical properties of LiMn<Subscript>2−<Emphasis Type="Italic">y</Emphasis></Subscript>Me<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>O<Subscript>4</Subscript> (Me = Cr,Co, Ni) spinels as cathodic materials for lithium-ion batteries

A number of spinel phases with a general formula LiMn_2?y Me _y O (Me = Cr, Co, Ni) was synthesized using the melt-impregnation and sol-gel methods. All synthesized materials were subjected to electrochemical testing of their suitability as cathodes in lithium-ion batteries. Cyclic voltammograms were used in the testing. The cathode materials prepared using the melt-impregnation method showed the highest initial discharge capacity (up to 120 mA h/g) and stable operation during the cycling. The partial substitution of chromium and cobalt atoms for manganese gives positive effect: the spinel structure is stabilized during the cycling. The double doping of the Li-Mn-O system with small amounts of Co and Ni results in the stabilizing of the discharge capacity. An overstoichiometry excess of lithium in Co- or Cr-doped spinels also favors the increasing of the discharge capacity and slows down its decaying during the cycling.     

金属锂二次电池锂负极改性

本文综述了金属锂二次电池中提高锂负极性能的研究进展。分别介绍了以下改性方法:对金属锂表面进行预处理,使其表面预先形成性能良好的固体电解质界面膜,或直接在其表面制备保护膜;在电解液中加入添加剂对锂电极进行表面改性;采用新型有机溶剂、离子液体、聚合物电解质、玻璃态固体电解质、塑晶固体电解质等电解质体系提高界面相容性;改进金属锂电极的制备工艺,如制备金属锂粉末多孔电极和电沉积锂电极、制备全固态薄膜锂电池以及利用物理方法处理锂电极。并在此基础上对今后的发展趋势进行了展望。     

新型添加剂全氟辛酸铵对提高锂离子电池安全性能的研究

报导可显著提高锂离子电池安全性的新型电解液添加剂全氟辛酸铵(APC). UL 94 可燃性试验显示添加0.70 wt% APC能使有机电解液的火焰传播速率下降33%. 差示扫描量热法(DSC)测试表明APC显著减弱了嵌锂碳电极和电解液之间的放热反应, 并将其热不稳定温度由138.0 ℃提高到167.5 ℃. 交流阻抗检测显示APC的加入明显降低了碳材料电极的界面阻抗, 并且提高了在储存过程中其固态电解质界面(SEI)层的稳定性. 添加APC还能有效地提高Li/MCMB电池充放电循环性能和库仑效率.     

Structure of (Me<Subscript>2</Subscript>Cu)Li · 3DME and its oligomers [(Me<Subscript>2</Subscript>Cu)Li · 3DME]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 2–5): a theoretical study

The structures of monomeric lithium dimethylcuprate solvated by three 1,2-dimethoxyethane (DME) molecules (Me₂Cu)Li · 3DME and its oligomers [(Me₂Cu)Li · 3DME] _n (n = 2–5) in the gas phase were studied using the density functional theory. The structures of these systems are compared with that of (Me₂Cu)Li · 3DME in the crystal. It is shown that numerous C-H…Cu and C-H…C hydrogen bonds, as well as C-H…H dihydrogen bonds between DME molecules, which solvate lithium cations, and corresponding dimethylcuprate anions significantly affect the formation and structure of these compounds in the gas and solid phases. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 470–481, March, 2008.