In this paper we present our studies on the properties of battery electrolyte based on EC/DMC (ethylene carbonate/dimethyl carbonate, w/w ratio 2:5) and PEODME (poly(ethylene oxide) dimethyl ether) (M-w=500) doped with LiCF3SO3-lithium trifluoromethanesulfonate (LiTf) and modified with TPFPB (tris(pentafluorophenyl)borane) as a potential anion trapping agent. We were particularly interested how this compound behaves in different solvents, e.g. battery mixture EC/DMC and model polymeric matrix PEODME. We also verified stability of the proposed solutions by means of DSC and FTIR, determined influence on conductivity and lithium transference numbers by impedance spectroscopy, and finally attempted to define mechanism of influence of boron addition on different systems. (C) 2010 Elsevier B.V. All rights reserved.