Electrochemical properties of non-aqueous electrolytes containing spiro-type ammonium salts

Electrochemical properties of organic solvent electrolytes containing salt additive were investigated by means of cyclic voltammetry, ionic conductivity and charge–discharge curve. The electrolyte was prepared by a mixture of propylene carbonate (PC) and dimethyl carbonate (DMC), tetraethylammonium tetrafluoroborate (TEABF4) and spiro-1,1′-bipyrolidinium tetrafluoroborate (SBPBF4) as a salt additive. The aim of this paper is to evaluate the effect of spiro-type quaternary ammonium salt on electrochemical properties. The bulk resistance of the mixture electrolytes and interfacial resistance were investigated using an AC impedance method. The result shows that SBPBF4 has good solubility in PC/DMC and the ionic conductivity is comparable to TEABF4 in PC/DMC. From the experimental results, by using the SBPBF4 salt, the interfacial resistance was decreased and capacity and ionic conductivity were increased. These results may be due to the higher mobility or ion dissociation of the SBP cation with smaller ion size than the TEA cation against the meso- or micro-pores of the activated carbons electrode.