A nano fiber-gel composite electrolyte with high Li+ transference number for application in quasi-solid batteries

As their Li+ transference number (t(Li)+ ), ionic conductivity, and safety are all high, polymer electrolytes play a vital role in overcoming uncontrollable lithium dendrites and low energy density in Li metal batteries (LMBs). We therefore synthesized a three-dimensional (3D) semi-interpenetrating network-based single-ion-conducting fiber-gel composite polymer electrolyte (FGCPE) via an electrospinning, initiation, and in situ polymerization method. The FGCPE provides high ionic conductivity (1.36 mS cm(-1)), high t(Li)+ (0.92), anda high electrochemical stability window (up to 4.84 V). More importantly, the aromatic heterocyclic structure of the biphenyl in the nanofiber membrane promotes the carbonization of the system (the limiting oxygen index value of the nanofiber membrane reaches 41%), giving it certain flame-retardant properties and solving the source-material safety issue. Due to the in situ method, the observable physical interface between electrodes and electrolytes is virtually eliminated, yielding a compact whole that facilitates rapid kinetic reactions in the cell. More excitingly, the LFP/ FGCPE/Li cell displays outstanding cycling stability, with a capacity retention of 91.6% for 500 cycles even at 10C. We also test the FGCPE in high-voltage NMC532/FGCPE/Li cells and pouch cells. This newly designed FGCPE exhibits superior potential and feasibility for promoting the development of LMBs with high energy density and safety.