Ionic conductivity and diffusion coefficients of lithium salt polymer electrolytes measured with dielectric spectroscopy Antoni Munar a, ⁎, Andreu Andrio a , Rosa Iserte b , Vicente Compañ c, b a Universitat Jaume-I, Avda de Vicent Sos Banyat s/n, 12072, Castelló de la Plana, Spain b Instituto Tecnológico de la Energía (ITE), Avda Juan de la Cierva, 24, 46980 Paterna, Spain c Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain abstract article info Article history: Received 23 February 2011 Received in revised form 22 April 2011 Available online 27 May 2011 JEL classification: 60.66.30.H 80.82.35.Rs 80.82.47.Aa 130.200 Conductivity 130.200 Dielectric properties Relaxation Electric module 350 Polymers and organics Keywords: Ionic conductivity; Mobility; Polymer; Lithium battery Ionic conductivity, diffusion coefficients, mobility and ionic concentration for lithium salts dissolved in polymer electrolytes are determined by the modeling of the dielectric loss and spectra. Cation and anion diffusion coefficients are quantified using the Trukhan model depending on the assumed ratio of the cation to anion diffusion coefficients. Measurements are performed for polymer electrolytes consisting of polyethylene oxide (PEO) with dissolved LiClO 4 salts for different sample thicknesses and temperatures ranging from 5 to 105 °C, which comprises both the crystalline and amorphous phases of the composite electrolyte. A good phenomenological description of the dielectric loss spectra is obtained for both the semi-crystalline and amorphous phases. The fraction of mobile ions is estimated to vary from 0.002% at 25 °C (semi-crystalline phase) up to 0.05% at 80 °C (amorphous phase). © 2011 Elsevier B.V. All rights reserved. 1. Introduction Dry conductive polymer electrolytes are considered as an alterna- tive to liquid or gel polymer electrolytes in lithium secondary batteries for hybrid and electric vehicles and have been subject of intense study during the last years [1–3]. However, the complete characterization of the ionic conductivity still remains an open question [2,3]. Such difficulties arise in part because of the different effects that must be taken into account when measuring the ionic conductivity. The conductivity mechanisms fundamentally depend on the polymer phase [2], where the most significant contribution to conductivity occurs in the amorphous phase, due to the segmental motion of the polymer chains. With a varying degree, conductivity is also observed for other semi-crystalline phases below de glass transition tempera- ture (t g ) [2]. Besides that in dielectric measurements, depending on the temperature, the separation between glass-rubber relaxation and relaxation due to free charges can be difficult due to their simultaneous presence [4–6]. From the experimental point of view, electrode effects caused by image charges in the electrodes can greatly contribute to obscure the measurements, especially at low frequencies [7]. Further- more, in typical polymer electrolytes a large fraction of ions may be bound up in ion pairs or clusters, and therefore the total concentration of charge carriers is difficult to quantify [8]. In this paper we take into account the above mentioned effects and model the dielectric loss spectra of polymer electrolytes consisting of polyethylene oxide (PEO) with dissolved LiClO 4 salts. We consider the macroscopic polarization of mobile ion charges, the influence of possible glass-rubber relaxations and other electrode effects. We measure the ionic conductivity and the relaxation polarization due to mobile ionic charges. Also, we propose a method to estimate the values of cation and anion diffusion coefficients together with the free ion concentration assuming that the diffusion coefficient values for both the cation and anion of the dissolved salt are of the same order of magnitude, which is in agreement with reported measurements from other methods [16,17]. In this case, the tan δ data can be analyzed with the Trukhan model [4,5] and the diffusion coefficients and ionic concentration of free charge carriers can be estimated. The measurements are performed for temperatures ranging from 0 to 105 °C and are check against different sample thicknesses. Journal of Non-Crystalline Solids 357 (2011) 3064–3069 ⁎ Corresponding author. Tel.: + 34 618094929. E-mail address: munar@uji.es (A. Munar). 0022-3093/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2011.04.012 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol