新一代动力锂离子电池磷酸锰锂正极材料的研究现状与展望

磷酸锰锂（LiMnPO₄）正极材料具有能量密度高、成本低、安全性高和热稳定性好等优点,目前已成为锂电产业界研究的热点,有望成为继磷酸铁锂（LiFePO₄）之后的新一代正极材料. 然而,磷酸锰锂的电子电导率和锂离子扩散率均很低,其电化学性能提高较为困难,至今尚无法制备出满足实际应用的高性能LiMnPO₄正极材料,严重制约了LiMnPO₄材料及其电池的发展. 本文从LiMnPO₄的结构特性出发,对近年来国内外在碳包覆、离子掺杂、纳米化和控制晶体形貌等改性研究、全电池研究、专利情况以及商业化尝试等多方面进行了综述,并对LiMnPO₄的发展进行了展望.     

焙烧温度对锂离子电池正极材料Li2MnSiO4/C 电化学性能的影响

采用液相法合成了Li₂MnSiO₄/C复合正极材料,并研究了不同焙烧温度对材料的结构、形貌和电化学性能的影响.利用热重（TG）分析了材料前驱体的热行为,确定了合成Li₂MnSiO₄/C复合正极材料的焙烧温度范围为600-800℃.X射线衍射（XRD）测试结果表明,不同温度下合成的样品材料均具有正交结构,且空间群为Pmn2₁,同时利用扫描电子显微镜（SEM）对所得样品材料的微观形貌及颗粒大小进行了表征.将所得Li₂MnSiO₄/C复合正极材料组装成扣式电池,并在不同的电流密度下进行充放电测试,结果表明:700℃合成的样品材料电化学性能最佳,具有较高的库仑效率及很好的循环稳定性.     

富锂锰基正极材料的表面改性研究进展

随着电动汽车和储能电站等电力设备的快速发展,对高能量密度的锂离子电池的需求日益增加.高比容量（>250 mAh·g^-1）的富锂锰基正极材料,有望成为锂离子电池实现高比能量（>350 Wh·kg^-1）的关键正极材料.富锂锰基正极材料的Li₂MnO₃相和晶格氧参与电化学反应使其拥有了高容量,但这也导致表面结构和成分容易发生变化,进而造成富锂锰基正极材料存在着诸如首次库伦效率低、倍率性能差和循环后电压和容量衰减严重等问题.因此,本文综述了富锂锰基正极材料的表面包覆、表面掺杂和表面化学处理三种表面改性方法,并进一步讨论了三种表面改性方法对材料性能提升的机制机理和优缺点.在此基础上,介绍了近些年基于多方法的表面联合改性工作.通过对富锂锰基正极材料进行表面联合改性,不仅可以改善其结构稳定性和抑制电极/电解液界面副反应,而且可以缓解其在循环过程中不断发生的结构转变和晶格氧的析出问题.最后,对富锂锰基正极材料表面改性研究方向进行了总结和展望.     

层状KxMnO2基钾离子电池正极材料的研究现状及发展趋势

钾离子电池具有资源丰富、价格便宜等优点,并且与锂离子电池原理相似,是目前取代锂离子电池成为大型储能系统合适的候选者.正极材料对钾离子电池性能起着关键作用,其中层状K_xMnO₂基正极材料因其高比容量、环境友好、成本低廉、独特的二维钾离子扩散通道而备受关注.但大尺寸的K⁺在充放电过程中的反复脱嵌会导致结构破坏,并且Mn³⁺产生的Jahn-Teller效应导致结构畸变,容量快速下降,商业应用难度较大.本文从K_xMnO₂材料层状结构调控出发,系统总结了K_xMnO₂基正极材料的制备方法,重点综述了单金属掺杂、双金属掺杂和碱金属掺杂等三种掺杂改性策略,总结阐述了K_xMnO₂基正极材料在现阶段研究中存在的主要挑战并进一步展望了其未来发展方向,可望为开发高效稳定的钾离子电池提供理论参考.     

铝掺杂及钨酸锂表面包覆双效提升富锂锰基正极材料的循环稳定性

采用溶胶-凝胶法合成Al掺杂富锂锰基Li_1.2Mn_0.54-xAl_xNi_0.13Co_0.13O₂（x=0、0.03）锂离子电池正极材料,之后采用一步液相法制备Li₂WO₄包覆层,系统地研究了Al掺杂和Li₂WO₄包覆双效改性对富锂锰基正极材料电化学性能的影响.结果表明,Al掺杂后明显提升富锂锰基正极材料的循环稳定性,包覆层Li₂WO₄明显改善其倍率性能和放电平台电压衰减问题.Li₂WO₄包覆量为5% Li_1.2Mn_0.51Al_0.03Ni_0.13Co_0.13O₂正极材料在2.0~4.8 V充放电电压区间及1000 mA·g^-1电流密度下比容量仍高达110 mAh·g^-1左右,同时在100 mA·g^-1的电流密度下循环300次容量保持率为78%,而且循环过程中放电平台电压衰减也明显减缓.该工作为解决锂离子电池富锂锰基正极材料循环稳定性和平台电压衰减提供了新的思路.     

Fe对NaNbO3的晶格掺杂和同步异质结改性及其光催化性能

运用溶剂热法及继之的高温晶化法制备钙钛矿结构NaNbO₃,并在此基础上同步获得了NaNbO₃晶格内Fe³⁺的掺杂和NaNbO₃晶格外α-Fe₂O₃的异质结复合.观察到了同步改性NaNbO₃对水体罗丹明B（RhB）光催化降解效率的显著提升,最适Fe含量的改性NaNbO₃对罗丹明B 1 h内的降解率可达95%,表观一级动力学速率常数为改性前NaNbO₃的近7倍.运用X射线衍射（XRD）、扫描电子显微（SEM）、X光电子能谱（XPS）、光致发光（PL）光谱、低温N₂吸附-脱附（BET法）,电子自旋共振光谱（ESR）,紫外-可见漫反射光谱（DRS）及光致电流检测等表征和测量探明改性体系的组成及结构,并表明Fe³⁺对Nb⁵⁺的掺杂取代可通过杂质能级形成、电子和空穴捕获以及溶氧吸附的促进从而有利于对罗丹明B的光催化降解;适量α-Fe₂O₃晶格外复合改性NaNbO₃可通过NaNbO₃与α-Fe₂O₃异质结间电子的跃迁和流动提高复合催化剂的光量子效率.Fe对NaNbO₃晶格内外改性促活的实质可能在于光生载流子迁移的促进和对其复合的抑制.     

氟化石墨材料的改性及其电化学性能研究

本文以商用氟化石墨为原料,通过水合肼还原的方法对氟化石墨（CF_x）进行改性处理,系统研究了不同水合肼用量对材料电化学性能的影响. 采用XRD、SEM、EDS、XPS、交流阻抗（EIS）和恒流放电测试技术,对改性氟化石墨材料的物相及电化学性能进行了分析研究. 结果表明,采用改性氟化石墨材料制备的锂/氟化碳（Li/CF_x）电池的电压滞后现象得到明显改善,且不同水合肼用量对材料的电化学性能有重要影响. H-CF_x-2（CF_x：C₂H₆O：N₂H₄·H₂O 的比例为1：2：1）材料的综合性能最佳,在0.1C 倍率下,材料的克比容量达到794.5 mAh·g^-1,平台电压为2.53V,电压滞后现象的低波电压为2.37 V.     

喷雾干燥-高温烧结的NaMnPO4制备及其电化学性能

采用喷雾干燥制备前驱体,经高温烧结制得有电化学活性的钠离子电池NaMnPO₄正极材料. X射线衍射分析（XRD）证明,合成的NaMnPO₄材料系正交晶系、Pmnb空间群的磷钠锰矿（Natrophilite）型材料. 扫描电镜（SEM）及透射电镜（TEM）结果显示,喷雾干燥得到的前驱体为空心球粒子,经高温烧结后,该材料由粒径几十纳米的NaMnPO₄纳米晶一次颗粒及无定形碳网络结构相互连接组成的微米级二次颗粒构成. 电化学测试表明,NaMnPO₄/C复合结构显著改善了材料的离子电导与电子电导,首次报道电流密度为7.75 mA·g^-1、电压范围为1.0 ~ 4.5 V (vs. Na⁺/Na)时,钠离子电池NaMnPO₄正极材料的可逆放电比容量达90 mAh·g^-1.     

石墨烯-Li2MnSiO4复合正极材料的合成与电化学性能研究

采用水热辅助溶胶凝胶法成功合成了石墨烯-Li₂MnSiO₄锂离子电池复合正极材料. 利用XRD,SEM及TEM等手段表征了复合正极材料的组成和形貌,并测试了不同氧化石墨烯复合量正极材料样品（质量分数为2%,4%,6%,8%,10%,及未复合氧化石墨烯）的电化学性能. 研究结果表明,石墨烯与Li₂MnSiO₄材料均匀地复合在一起;添加适量的氧化石墨烯能促使Li₂MnSiO₄粒子的分布趋向疏松,并形成微孔结构;氧化石墨烯复合量为6%时形成的石墨烯- Li₂MnSiO₄样品电化学性能最佳,扣除碳含量后,以10 mA/g为电流密度,首周放电比容量为166 mAh/g,循环20周后放电比容量仍保持在101 mAh/g. 此外,与石墨烯复合后的Li₂MnSiO₄材料倍率性能也得到了明显的改善. 石墨烯的存在提高了复合材料的导电性,提升了Li₂MnSiO₄正极材料的可逆嵌脱锂容量.     

锂离子电池富锂锰基正极材料的研究进展

随着新能源如电动汽车、储能电站的蓬勃发展,人们对下一代高性能锂离子电池的能量密度、功率密度和循环寿命提出了更高的要求. 而富锂锰基正极材料xLi₂MnO₃·(1-x)LiMO₂（0 < x < 1,M = Mn、Co、Ni…）具有可逆比容量高（240 ~ 280 mAh·g^-1,2.0 ~ 4.8 V）、电化学性能较佳、成本较低等优点,已吸引了研究者的关注,有望成为下一代锂离子电池用正极材料. 本实验室采用固相法和溶胶-凝胶法制备不同的富锂锰基正极材料,其中,溶胶-凝胶法制得的Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂电极首周期放电比容量277.3 mAh·g^-1,50周期循环后容量272.8 mAh·g^-1,容量保持率98.4%. 本文重点结合本实验室的研究工作,对新型富锂锰基正极材料xLi₂MnO₃·(1-x)LiMO₂的结构、合成、电化学性能改性和充放电机理等进行总结与评述.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

Synthesis of phenolic components of Grains of Paradise

Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.     

Summary of development of the theory of stability of colloids and thin films

In this review, the research of the author in the field of colloidal systems is summarized. The factors influencing colloidal stability are systematized and analyzed. Examples are presented to illustrate the practical utilization of the theory of stability of colloids and thin films.This review was prepared on the basis of the works of the author, which were awarded the State Premium for 1991 in the field of science and technology, chemistry section.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1708–1717, August, 1992.     

Study of hydration of two cements of different strengths

Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M_o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700^oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.     

氯氧化镁生成热的研究

用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。     

Thermodynamics of the formation of oxosulfides of rare-earth elements

The enthalpies of solution of several oxosulfides of rare-earth elements and the high-temperature enthalpies of oxosulfides and oxosulfates of lanthanum and yttrium were measured using solution calorimetry and high-temperature microcalorimetry techniques. Standard enthalpies of formation and some thermodynamic properties of oxosulfides and oxosulfates were calculated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2 pp. 294–297, February, 1997.     

探究“铁的锈蚀条件”实验创新设计

设计了铁的锈蚀实验,说明了铁钉的处理方法,增加了温度、酸、碱的影响条件,实现了铁跟蒸馏水及空气中氧气快速反应而生锈,使实验在5 min左右就能够得到准确的结果。