A Single-Lithiun-Ion Conductor Coordinated Porous Pvfm-Peg Based Membrane and Plasticizer As Electrolyte for Lithium Ion Batteries

Abstract

Polymer electrolyte comprised of lithium dissolved in polymer matrix has draw great attention due to its safety as well as processability, flexibility and lightweight. The dissociation of binary lithium salt in polar polymer matrix gives rise to so called bi-ionic conductors in which both cations and anions migrate as charge carriers. But unfortunatelly, a serious concentration polarization takes place in bi-ionic conductors due to the buildup of the anions at the electrode/electrolyte interface[1]. In order to solve the above problem, a single ion conductive polymer electrolyte has been proposed, in which the counter anions are tethered to the polymer backbone or immobilized in a matrix, eliminating polarization loss and enabling the passage of larger currents through the cells[2]. Until recently, single ion polymer electrolytes reported show low ambient temperature ionic conductivities (<10-6S·cm-1) due to the strong interaction between cations and their immobile matrixes[3]. A single-ion conductive hybrid electrolyte of porous PVFM-PEG based membrane and the optimized PC/EC (1/1, vol) mixed solvent as plasticizer was fabricated. The membrane and its electrolyte were characterized using scanning electron microscopy (SEM), stress-stain test, linear sweep voltammetry (LSV), ionic conductivity and lithium ion transference number measurement. The results indicate the combination of optimized PC/EC (1/1 in vol) plasticizer and porous PVFM-PEG based membranes[4] contributes to a considerable enhancement of room-temperature conductivity to 1.59×10-4S/cm. At the same time, lithium ion transference number of hybrid electrolyte based on the porous PVFM-PEG electrolyte membranes increased to 0.76. The assembled cells from the hybrid electrolyte also show wide electrochemical stability window and excellent cyclability.Reference [1] Bouchet R, Maria S, Meziane R, et al. Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries[J]. Nature materials, 2013, 12(5): 452-457. [2] Sinha K, Wang W, Winey K I, et al. Dynamic Patterning in PEO-Based Single Ion Conductors for Li Ion Batteries[J]. Macromolecules, 2012, 45(10): 4354-4362. [3] Kobayashi N, Uchiyama M, Tsuchida E. Poly [lithium methacrylate-co-oligo (oxyethylene) methacrylate] as a solid electrolyte with high ionic conductivity[J]. Solid State Ionics, 1985, 17(4): 307-311. [4] Fang Lian, Hong-yan Guan, Yan Wen, Xiao-rong Pan, Polyvinyl formal based single-ion conductor membranes as polymer electrolyte for lithium ion batteries, Journal of membrane science 2014, 469, 67-72