Li_4SiO_4-Li_3VO_4赝二元系和Li_4GeO_4-Li_4SiO_4-Li_3VO_4赝三元系中新的锂离子导体

本文在室温到300℃的温度范围内研究了Li_4SiO_4-Li_3VO_4和Li_4GeO_4-Li_4SiO_4-Li_3VO_4体系中的离子导电性,发现γ_(II)相固溶体Li_(3 x)V_(1-x)Si_xO_4是好的锂离子导体。所研究的成分中Li_(3.3)V_(0.7)Si_(0.3)O_4的离子电导率最高,室温下为1×10~(-5)Q~(-1)·cm~(-1),在42—192℃的电导激活能为0.36eV,电子电导率可以忽略,因而这是迄今所发现的最好的锂离子导体之一。粗略确定了Li_4GeO_4-Li_4SiO_4-Li_3VO_4三元系中电导率高的范围,发现在Li_(3.5)V_(0.5)Ge_(0.5)O_4中Si部分取代Ge可以使电导率进一步提高,Li_(3.5)V_(0.5)Ge_(0.4)Si_(0.1)O_4的室温电导率可达1.3×10~(-5)Q~(-1)·cm~(-1),电导激活能为0.40eV。     

二硫化钦作为锉离子电池负极材料的特性

采用固相法合成了纯六方相的TiS₂粉体. X射线衍射(XRD)、扫描电子显微镜(SEM)结果表明该材料具有特征层状结构, 其颗粒大小在10-20 μm之间. 作为锂离子电池负极材料, TiS₂在3.00 V(vs. Li⁺/Li)以下有3个明显的放电平台, 首次可逆容量达668 mAh·g^-1, 在第一个放电电压范围(3.00-1.40 V)内具有优异的循环可逆性. 深度放电时由于Li₂S的生成和材料颗粒严重破碎, 在低于0.50 V时材料的循环性能不佳. 通过减小材料颗粒度和提高导电剂含量, TiS₂的电化学性能得到显著改善.     

Liquid-phase synthesis of Li2S and Li3PS4 with lithium-based organic solutions

Sulfide solid electrolytes are widely regarded as one of the most promising technical routes to realize all-solid-state batteries (ASSBs) due to their high ionic conductivity and favorable deformability. However, the relatively high price of the crucial starting material, Li₂S, results in high costs of sulfide solid electrolytes, limiting their practical application in ASSBs. To solve this problem, we develop a new synthesis route of Li₂S via liquid-phase synthesis method, employing lithium and biphenyl in 1, 2-dimethoxyethane (DME) ether solvent to form a lithium solution as the lithium precursor. Because of the comparatively strong reducibility of the lithium solution, its reaction with sulfur proceeds effectively even at room temperature. This new synthesis route of Li₂S starts with cheap precursors of lithium, sulfur, biphenyl and DME solvent, and the only remaining byproduct (DME solution of biphenyl) after the collection of Li₂S product can be recycled and reused. Besides, the reaction can proceed effectively at room temperature with mild condition, reducing energy cost to a great extent. The as-synthesized Li₂S owns uniform and extremely small particle size, proved to be feasible in synthesizing sulfide solid electrolytes (such as the solid-state synthesis of Li₆PS₅Cl). Spontaneously, this lithium solution can be directly employed in the synthesis of Li₃PS₄ solid electrolytes via liquid-phase synthesis method, in which the centrifugation and heat treatment processes of Li₂S are not necessary, providing simplified production process. The as-synthesized Li₃PS₄ exhibits typical Li⁺ conductivity of 1.85×10^-4 S·cm^-1 at 30 ℃.     

聚吡咯-过渡金属-氧配合物储锂材料的结构与性能研究

目前锂离子电池电极材料主要使用无机材料. 近年来有机物电极材料虽有报道,但这些材料大都比容量低、倍率性能差. 本文介绍一类新型有机金属配合物聚吡咯-过渡金属-氧储锂材料的合成、结构及电化学性能. 结合扩展X-射线吸收精细结构谱分析和密度泛函理论计算,发现这类材料呈现多层结构特征,层内稳定的过渡金属-吡咯N的配位作用及循环过程中层间过渡金属-氧键的可逆断裂和结合使该类材料具有很高的储锂容量和循环稳定性,且聚吡咯导电网络使得该材料具有良好的倍率性能. 这类新材料将有望成为锂离子电池的高比容量负极材料.     

钠离子电池新型Cu基隧道型氧化物正极材料研究

成本较为低廉的钠离子电池成为储能领域的新秀,备受关注.以Na₂CO₃,CuO,Fe₂O₃,MnO₂和TiO₂为原料,通过简单的固相反应法合成了一系列新型Cu基隧道结构化合物.通过X射线衍射（XRD）、扫描电子显微镜（SEM）和电化学性能测试对所得样品的结构、形貌以及电化学性能进行了表征.XRD结果表明材料结构与Na_0.44MnO₂一样为隧道结构,空间群为pbam.室温下的电化学性能测试表明Mn替代的样品在1.5~4.1 V的范围内表现出了90 mAh/g的比容量,循环稳定,倍率性能较好,1C容量保持率仍为74%.XPS结果验证了Cu在充放电过程中参与了变价.原位XRD结果表明Na_0.66Cu_0.17Mn_0.33Ti_0.5O₂电极材料在1.5~4.1 V的范围内可以保持稳定的隧道型结构.本工作首次报道了Cu在隧道型结构材料中的变价行为,为进一步设计隧道结构的材料以及钠离子电池正极材料提供新思路.     

稳定富锂层状氧化物正极材料的结构与性能

因高能量密度和高能量转换效率,锂离子电池已被广泛应用于便携式电子设备和电动交通中。富锂层状结构氧化物以高达300 mAh·g^-1的可逆容量成为能量密度350 Wh·kg^-1及以上动力锂离子电池的重要候选正极材料。但是,欲使这类材料获得实际应用,就必须解决循环过程中结构衰退带来的一系列问题。本文重点介绍近几年来笔者所领导的研究组通过元素筛选实现材料的表面和体相掺杂,通过全新的结构设计稳定材料结构和性能方面的努力。同时,为使读者对国内外重要研究组在相关方面的研究进展也有所了解,我们也将从元素替代、结构一体化表面修饰(包括多层表面修饰和浓度梯度材料)、表面包覆和表面掺杂等方面介绍他们的重要研究成果。最后,将对该类材料的未来发展方向作出展望并给出我们的一些思考。     

A high-performance rechargeable Li–O_2 battery with quasi-solid-state electrolyte

A novel transparent and soft quasi-solid-state electrolyte(QSSE) was proposed and fabricated, which consists of ionic liquid(PYR_(14)TFSI) and nano-fumed silica. The QSSE demonstrates high ionic conductivity of 4.6×10~(-4) S/cm at room temperature and wide electrochemical stability window of over 5 V. The Li–O_2 battery using such quasi-solidstate electrolyte exhibits a low charge-discharge overpotential at the first cycle and excellent long-term cyclability over 500 cycles.     

锂离子电池中的尺寸效应与表界面问题研究

文章介绍了锂离子电池中的尺寸效应与表界面问题的研究.从热力学与动力学方面讨论了小尺寸材料与体材料性质的区别以及作为储能材料的优缺点.从实际考虑,建议发展动力学稳定的纳米结构电极材料.     

A New Method for Generating Hydrogen from Water

A new method for generating hydrogen by the reaction of Al powder with water using iodine as additive is developed. 12 can penetrate through the surface oxide layer on aluminium to form AlI3. High solubility of AlI3 in water is benefited to activate Al surface. It is found that the production of hydrogen becomes significant above 60℃ and obeys a logarithm rule. The pH value which is determined mainly by the kinetics of hydration spontaneously. varies from 5 to 3 then back to 4.5 during the reaction, reaction of AlI3 and the reaction of Al and HI produced     

全钒氧化还原液流电池用Nafion/有机硅复合膜

采用原位化学反应的方法制备了Nafion/有机硅复合膜, 并对所制备复合膜的离子交换容量(IEC)、电导率和水渗透率等进行了测试. 结果表明, 所制备复合膜具有优异的阻水性能. 以Nafion/有机硅复合膜作为离子交换膜的钒电池的库仑效率(CE)和能量效率(EE)都得到了大幅度提高. 此外, 以所制备复合膜为离子交换膜的VRB单电池充放电80次后性能几乎无衰减, 说明所制备Nafion/有机硅复合膜即使在强酸和强氧化性的钒电池体系中也可以稳定使用, 表明Nafion/有机硅复合膜是一种性能优异的适用于全钒氧化还原液流电池的新型质子交换膜.