Immobilization of Anions on Polymer Matrices for Gel Electrolytes with High Conductivity and Stability in Lithium Ion Batteries

This study reports on a high ionic-conductivity gel polymer electrolyte (GPE), which is supported by a TiO2 nanopartide-decorated polymer framework comprising poly-(acrylonitrile-co-vinyl acetate) blended with poly(methyl methacrylate), i.e., PAVM:TiO2. High conductivity GPE-PAVM:TiO2 is achieved by causing the PAVM:TiO2 polymer framework to swell in 1 M LiPF6 in carbonate solvent. Raman analysis results demonstrate that the poly(acrylonitrile) (PAN) segments and TiO2 nanoparticles strongly adsorb PF6- anions, thereby generating 3D percolative space-charge pathways surrounding the polymer framework for Lit-ion transport. The ionic conductivity of GPE-PAVM:TiO2 is nearly 1 order of magnitude higher than that of commercial separator-supported liquid electrolyte (SLE). GPE-PAVM:TiO2 has a high Lit transference number (0.7), indicating that most of the PF6- anions are stationary, which suppresses PF6- decomposition and substantially enlarges the voltage that can be applied to GPE-PAVM:TiO2 (to 6.5 V vs Li/Li+). Immobilization of PF6- anions also leads to the formation of stable solid-electrolyte interface (SEI) layers in a full-cell graphitelelectrolytelLiFePO(4) battery, which exhibits low SEI and overall resistances. The graphitelelectrolyte LiFePO4 battery delivers high capacity of 84 mAh g(-1) even at 20 degrees C and presents 90% and 71% capacity retention after 100 and 1000 charge discharge cycles, respectively. This study demonstrates a GPE architecture comprising 3D space charge pathways for Lit ions and suppresses anion decomposition to improve the stability and lifespan of the resulting LIBs.