Nanofiller-incorporated hybrid electrolytes for lithium batteries

Abstract

The development of lithium metal batteries (LMBs) is hampered by their safety issues mainly caused by dendrite formation. A simple, effective and economical way for the suppression of detrimental effect of lithium (Li) dendrite growth is highly desirable. In this thesis, facile strategies to improve the performance of LMBs by structuring electrolyte are presented. Ionic liquid (IL) was firstly grafted to mesoporous silica nanoparticles (MSNs) to form IL-tethered nanoparticles (MSN-IL-TFSI). The effects of the contents of MSN-IL-IL-TFSI on electrochemical properties of the hybrid electrolytes were studied systematically. The advantageous effect exerted by the hybrid electrolytes on Li electrodeposition was confirmed by galvanostatic polarization. To further improve lithium ion transference number, IL-decorateed PMMA nanoparticles (PMMA-IL-TFSI) were used to immobilize anions to prepare single-ion conducting polymer electrolytes (SIPEs). The effective suppression of lithium dendrite growth using this SIPE further confirmed that lithium ion transference number is one of the determined factors for the alleviation of lithium dendrite nucleation. Furthermore, IL was applied as additive/plasticizer to fabricate solid polymer electrolytes (SPEs). Owing to the significant contribution of ILs, the obtained SPEs exhibited excellent mechanical properties without sacrificing ionic conductivity, as well as promising potential for the use in wearable/flexible lithium batteries. In addition, the as-synthesized PMMA-IL-TFSI nanoparticles were blended with a mixture of propylene carbonate (PC)/ methyl acetate (MA) to develop a new electrolyte system. Electrochemical properties and mechanism for the enhancement of low-temperature performances at low temperature were investigated in detail. Finally, Li-ion conductive LLZO nanofibers were incorporated with PVDF-HFP matrix to design a new type of solid polymer electrolyte. Owing to the continuous pathways provided by LLZO nanofibers, the developed SPE exhibited very high room-temperature ionic conductivity, making it a good example for the development of solid polymer electrolytes combined inorganic Li-ion conductive ceramics with polymer matrices.

Date of Award	2018
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology