Silica-based ionogel electrolyte with porous flower-like structure enables safer lithium ion battery

The flammability and leakage of commercial lithium ion battery electrolytes greatly limit the safe application. All solid states electrolytes are considered as promising candidates but with low conductivity and interface issues. Quasi-solid state electrolyte with ionic liquid is believed to be a good choice. In this work, two kinds of ionogel quasi-solid state electrolytes with different lithium trifluoromethanesulfonate (LiOTf) and bis(trifluoromethane)sulfonimide lithium (LiTFSI) salts are firstly synthesized by a fast sol-gel method. Porous silica structure with 1-Butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid confined is constructed. Different lithium salts make a difference on the microstructure of the two ionogel electrolytes. Both ionogel electrolytes exhibit a high ionic conductivity and are applied to the LiFePO4 coin cells. The ionogel electrolyte with LiOTf exhibits a good cycle performance. The extremely rich and cross-linked porous structures provide sufficient channels for ion transportation. This ionogel electrolyte overcomes the disadvantages of electrolyte leakage and flammability while allowing the good electrochemical performances. It can be considered as one of the potential candidates for lithium ion battery electrolyte.