| 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 200?m,>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. |
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