Lithiated Nafion ionomer film is applied as functional separator for Li-S cells. The ionomer electrolyte is composed of the lithiated Nafion ionomer film and liquid electrolyte. The Li-ion conductivity of the ionomer electrolyte is 2.1 x 10(-5) S cm(-1) at room temperature. The Li-ion transference number and the elemental sulfur permeability of the ionomer electrolyte shows the polysulfide anions can transport through the ionomer film hardly. The CV result reveals the ionomer electrolyte is electrochemically stable and workable for lithium and sulfur electrodes. The initial discharge capacities of the Li-S cells with ionomer film and with liquid electrolyte are nearly the same. However, the discharge capacity of the Li-S cell with the ionomer film at the 50th cycle is found to be 815 mAh g(-1), and the coulombic efficiencies are above 97% along with cycles, showing an improvement in cycle performance as well as in coulombic efficiency, compared with the Li-S cell with liquid electrolyte of which the discharge capacity is 552 mAh g(-1), at the 50th cycles, and the coulombic efficiencies are lower than 97% along with cycles. (C) 2012 Elsevier B.V. All rights reserved.