【作者】 刘凯；

【导师】 汪长安；

【作者基本信息】 清华大学 ， 材料科学与工程， 2017， 博士

【摘要】 能传导锂离子的无机陶瓷电解质和有机聚合物电解质是固体或类固体材料,都能作为正负极之间无孔致密电解质隔层单独或与电解液组合用于锂电池中,尤其是用于被认为是下一代电池的锂金属电池中,可以减少金属锂负极的副反应,并较好地防止锂枝晶穿透,有助于解决锂金属电池的循环稳定性和安全性问题。两者在应用场合上具有互补性,都是被热点研究的新型电解质隔层材料。本论文分为两部分,分别研究这两种电解质。第一部分研究石榴石型锆酸镧锂系的无机陶瓷电解质材料。首先,论文设计了锂-双氧水半燃料电池组件,适用于陶瓷电解质薄片使用性能的表征评价。其次,论文研究了在氧化铝坩埚中烧制钽掺杂锆酸镧锂（LLZTO）电解质时,原料中锂盐过量量对电解质性能的影响。结果表明,烧结时锂元素能诱导坩埚中的铝元素扩散进电解质,并与之形成熔融态物质,促进烧结致密化和锂离子电导率的提高。锂盐过量量在0%⁵0%范围内增大时,熔融态物质增多,电解质的致密度和锂离子电导率都先显著提升,然后分别稳定在88%和4×10^-4 S cm^-1的水平。最后,论文整合并优化配料、掺杂策略和烧结方法,开发了高效率制备高性能石榴石型LLZTO陶瓷电解质薄片的方法。小批量制备了厚度约200μm的电解质薄片,致密度大于94%,室温锂离子电导率达1.02×10^-3 S cm^-1。而针对LLZTO电解质薄片机械强度不足的问题,我们设计并制备了LLZTO膜-氧化铝直通孔支撑体的复合电解质片,兼具LLZTO电解质薄片优异电化学性能和足够大的机械强度。第二部分研究弹性无孔酰胺脲橡胶电解质膜。论文分析了现有多孔隔膜的缺点,针对性的提出了弹性无孔电解质膜的设计,并利用酰胺脲超分子橡胶实现了这一设计。实验验证了酰胺脲橡胶薄膜在碳酸酯有机电解液中有限溶胀吸收电解液后具有超高锂离子电导率,稳定性也较好,可以作为弹性无孔电解质膜使用。论文通过纽扣电池实验,以及透明玻璃毛细管电池原位观察实验,证实了弹性无孔电解质膜在10 mA cm^-2的电流密度以及10 mAh cm^-2的面积容量密度下也能抑制锂枝晶生长和穿透,维持锂金属电池稳定循环。更多还原

【Abstract】 Solid or semi-solid state inorganic ceramic electrolyte and organic polymer electrolyte with high lithium ion conductivity,are promising electrolyte separator materials for lithium battery,especially for lithium metal battery,which is considered as the next-generation battery technology.Compared to the traditional electrolyte separator consisting of porous polyolefin membrane and organic liquid electrolyte,in form of non-porous free-standing thin sheets,both the ceramic and polymer electrolytes can be used with less or without liquid electrolyte in lithium metal batteries,resulting in less side reactions of lithium metal anode and lower risk of being penetrated through by lithium dendrites,so that improving the performance of the lithium metal batteries.The ceramic and polymer electrolyte have good complementarity in term of application,and both are research hotspots in the field of lithium batteries.In the first section of this study,we focus on garnet-type lithium lanthanum zirconium oxide（LLZO）ceramic electrolyte.Firstly,we designed a Li-H₂O₂semi-fuel cell with a special cell structure to estimate the usability of a ceramic electrolyte thin sheet conveniently.Secondly,we studied the influences of excess lithium salt in the raw material on the performances of the garnet-type Ta-doped LLZO（LLZTO）when sintered in an alumina crucible.It is found that,during sintering,the excess Li element can induce the Al element in the crucible to diffuse into the LLZTO sample and form liquid Li-Al-O melt,thereby improving the densification and ionic conductivity of the LLZTO ceramic.With the excess lithium salt increasing from 0%to 50 mol%,the amount of liquid melt increased,and the relative density and ionic conductivity of the LLZTO ceramic also increased and then leveled off at 88%and 4×10^-4 S cm^-1,respectively.Lastly,we integrated and optimized molar ratio of starting materials,doping strategy and sintering program,successfully developed a process to fabricate high-quality LLZTO ceramic electrolyte thin sheets with high efficiency.The thickness,relative density and ionic conductivity of the LLZTO thin sheets were about 200μm,>94%and 1.02×10^-3 S cm^-1,respectively.We measured the mechanical strength of the LLZTO thin sheet and found it was not high enough.To improve the mechanical strength of the electrolyte sheet,we designed a composite electrolyte with LLZTO membrane and honeycomb-like alumina supporter.Test results showed that it combined the excellent electrochemical properties of the LLZTO and the strong mechanical strength of the alumina supporter.In the second section of this study,we research a newly designed non-porous elastic polymer electrolyte based on a supramolecular rubber containing many amide and urea groups（named as amide-urea based rubber）.Aiming at solve or avoid the disadvantages of the traditional porous polymer separator,we proposed a non-porous and highly elastic electrolyte separator design,and realized the design using the amide-urea based rubber.Experiments showed that the rubber membrane can be swelled when immersed in carbonate organic liquid electrolyte,and thus established high lithium ionic conductivity.The swelled rubber membrane also showed good stability,and can be used as electrolyte separator in lithium metal battery.Tests in coin cells and specially designed transparent capillary cells confirmed that the rubber membrane can suppress the growth and penetration of the lithium dendrites even under a high current density of 10 mA cm^-2 and high areal capacity density of 10 mAh cm^-2.更多还原