PEDOT: PSS as a Functional Binder for Cathodes in Lithium Ion Batteries

Abstract

The application areas of rechargeable Li-ion batteries continue to grow, hence improvement in their energy density, rate capability and cycle life is necessary. A typical cathode contains usually redox active transition metal oxides as active materials, conductive additives to ensure electronic conductivity and binder supporting matrix. In this work we report the behavior and properties of carbon black free LiFePO 4 composite electrode, where poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) is accomplishing a dual role of binder and conducting additive. The effect of the polymer amount on the morphometric properties of the electrodes was studied using SEM, mercury porosimetry and high resolution X-ray computed tomography. The electrochemical performance and the cycling stability of the composite electrodes were compared to the behavior of conventional cathodes with carbon additives and PVDF binder. With increasing PEDOT:PSS content a decrease in the overvoltage and correspondingly an improvement in the rate capability is observed. Composite cathodes containing 8% PEDOT:PSS show comparable electrode capacity and better cyclic stability than conventional composite cathode.

New functional conducting poly-3,4-ethylenedioxythiopene:polystyrene sulfonate/carboxymethylcellulose binder for improvement of capacity of LiFePO4-based cathode materials

“…1c) verifies that the film structure remained unchanged. 10 20 wt.% PEDOT:PSS suggested earlier in [17], showed the best discharge capacities of about 118 mAh g -1 at 0.2 C, which are comparable with traditional PVDF-bound electrodes and are 20% lower than the values obtained in this work for C2.…”

“…Additional improvement of the electrochemical properties of LFP-based cathode materials with the use of conducting polymer coatings [9][10][11][12][13][14][15][16][17][18][19][20], and in particular, poly-3,4-ethylenedioxythiopene [12,[13][14][15] was proposed.…”

“…Conducting polyelectrolyte dispersion PEDOT:PSS, which can act both as electronconducting additive and as a binder, turned out especially attractive, providing enhanced electrochemical performance of the electrodes [16][17]19]. In the most cases of proposed 1 Corresponding author.…”

“…Tel/fax: +7 (812) 4286900, E-mail address: vkondratiev@mail.ru 2 LFP/PEDOT or LFP/PEDOT:PSS composites, however, large amounts either of carbon additives and inactive binders or conducting polymer were needed to produce mechanically stable electrodes with good electrochemical performance. Therefore, the values of capacities of LFP/PEDOT referred to the total weight of the composite electrodes including LFP and additives are relatively low (75-130 mAh g -1 at 0.1 C) [13][14][15]17].…”

“…This complex water-based additive, where PEDOT:PSS played dual role as conductive and binder additive [16,17,19] and carboxymethylcellulose (CMC) as additional binder [21] and thickening agent with good ionic conductivity [22]. It is more consistent with aqueous dispersion of PEDOT:PSS than the usual binder PVDF, that was used in [18].…”