锂离子电池用聚合物电解质的最新进展II.含液聚合物电解质

由于干态聚合物电解质目前还不能满足聚合物锂离子电池的应用要求,人们致力于开发含液体增塑剂的聚合物电解质,包括凝胶型和微孔型两类体系。本文综述了含液聚合物电解质的最新进展,重点论述了各种新体系和新方法。     

锂离子电池正极材料LiMn2O4的研究进展

具有尖晶石相的LiMn2O4因价格低、无毒、无环境污染、制备简单、研究较成熟,因此有着很好的应用前景,被看作最有可能成为新一代商用锂离子二次电池正极材料.由于LiMn2O4电化学循环稳定性能不好,表现在可逆容量衰减较大,尤其在高温下(>55℃)使用衰减更严重,从而限制了它的商业化应用.经过近十几年的研究,人们对其衰减机理有了比较清晰的了解,提出了造成容量衰减的几种可能原因如Jahn-Teller畸变效应、Mn2+在电解质中的溶解、出现稳定性较差的四方相以及电解质的分解等.通过掺杂、表面包覆、制备工艺的改进,人们已能制得循环稳定性能较好的尖晶相材料.本文结合我们研究小组的最新研究成果对锂离子二次电池正极材料LiMn2O4的最新研究进展进行综述和评论.     

锂铁氧体纳米晶的磁性能研究

我们用ＰＥＧ凝胶法合成出的ＬｉＦｅ＿５Ｏ＿３纳米晶，用ＸＲＤ和ＴＥＭ观测其粒径和形貌。用振动样品磁强计考察其比饱和磁化强度σ＿ｓ，随粒径口变化，得到样品的σ＿ｓ随Ｄ的减小而下降。     

熔融碳酸盐燃料电池阴极材料的导电性

通过交流阻抗方法研究了熔融碳酸盐燃料电池阴极材料锂镍氧化物、锂钴氧化物和锂铁氧化物的导电性能。结果表明:锂镍氧化物电极的导电性最好,锂钴氧化物电极的导电性次之,锂铁氧化物电极的导电性最差;它们的导电性都随着温度的升高而按指数规律增加;在合成锂钴氧化物(或锂铁氧化物)的过程中,使Li2CO3轻微过量,可以提高锂钴氧化物(或锂铁氧化物)电极的导电性,而且在同一温度下,随着nLi∶nCo(或nLi∶nFe,摩尔比)值的增大,锂钴氧化物(或锂铁氧化物)电极的导电性显著增加。     

聚苯醚磺酸锂／共聚醚复合物的离子导电性研究

合成了３种不同磺化度的聚苯醚磺酸锂（ＳＰＰＯＬｉ）与Ｐ（ＭＥＯ１６－ＡＭ）／ＳＰＰＯＬｉ复合物。研究了复合物的离子导电性与磺化度，组成比及增塑剂含量的关系。含４０％（ｍａｓｓ）增塑剂的复合物具有单离子导电特征，锂离子迁移数高达０．９７，室温电导率达２×１０－５Ｓ／ｃｍ。     

添加剂对尖晶石型锰酸锂性质表征的影响

以LiOH·H_20和MnO_2为原料,分别掺入H_2BO_3、Al_2O_3、SiO_2和P_2O_5等添加剂,用固相分段法制备尖晶石型锰酸锂。结果表明,SiO_2和P_2O_5可以有效地改善LiMn_2O_4的电化学性能,H_3BO_3对锰酸锂的电化学性能影响不大,而Al_2O_3破坏了LiMn_2O_4的电化学性能。面扫描结果显示,Si或P元素各自都均匀地分散于LiMn_2O_4的物相中。从元素电负性和原子半径的角度分析了B、Si、P和Al元素对尖晶石型LiMn_2O_4结构和性能的影响。     

锂离子电池正极材料锂锰氧化物的固相合成研究进展

阐述了固相合成反应的原理，综述了锂锰氧化物的几种固相合成方法，并着重介绍了熔融渍法，多步加热法，机械化学法和微波化学法等在锂锰氧化物合成中的研究进展。     

Conceptual design of a high-efficiency absorption cooling cycle

The search for high-efficiency, gas-fired cooling cycles has led to the development of dual-loop absorption machines with cooling coefficients of performance (COPs) in the 1.2 to 1.7 range. This increased performance may call for high generator temperatures, new working fluids or new materials of construction. In most cases, two different sets of working fluids are required. The conceptual design presented here is aimed at obtaining high efficiencies with relatively low temperatures, employing only one set of fluids. The concept consists of two loops coupled in a configuration aimed at minimizing the loss of thermodynamic availability incurred when transferring refrigerant between the loops. The working fluid pair is a solution of lithium bromide-water. The calculated COPs are of the order of 1.8. The cycle relies on an elaborate evaporator-absorber combination. The paper presents the conceptual design, the critical assumptions, and the performance calculations for the concept.     

In-chain functionalization by alternating anionic copolymerization of styrene and 1-(4-dimethylaminophenyl)-1-phenylethylene

Anionic copolymerizations of styrene (M₁) with excess 1-(4-dimethyl-aminophenyl)-1-phenylethylene (M₂) were conducted in benzene at 25°C for 24h, using sec-butyllithium as initiator. Narrow molecular weight distribution copolymers with M?;_n = 16.1 × 10³ g/mol (M?_w/M?_n = 1.04) and 38.2 × 10³g/mol (M?_w/M?_n = 1.05), and 24 and 38 moles of M₂ per macromolecule, respectively, were characterized by size exclusion chromatography, ¹H NMR spectroscopy and DSC. The monomer reactivity ratio, r₁ = 5.6, was obtained from the copolymer composition at complete consumption of M₁, assuming that the rate constant k₂₂ =0,i.e. r₂ =0. The polymers exhibited T_g values of 128 and 119°C, respectively, which correspond to an estimated T_g = 217°C for the hypothetical homopolymer of M₂.