UCLA

The growing market for energy storage devices raises the demand for lithium ion batteries (LIBs) with higher energy density and power density. Enhanced LIB performance requires the improvement of the electrode materials, so that the use of conductive polymer binders becomes an important option when the choice of active materials is limited. Compared to a traditional binder, such as PVDF, the advanced polymer binders exhibit not only electrochemical stability and adhesion strength, but also ionic/electronic conductivity for a thick electrode and/or a high-capacity electrode. Such considerations make the 3,4-propylenedioxythiophene-2,5-dicarboxylic acid family (ProDOT) and poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis (dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} family (P(NDI2OD-T2)) of polymers attractive candidates for the LIB binders.Various experiments were designed and conducted on the selected binder candidates in order to evaluate different aspects of polymer behavior. The material properties are investigated based on thin film three-electrode systems, while the half-cell and full-cell experiments represent how the binder influences the electrodes and practical batteries, respectively. According to those experiments, the Hexyl-ProDOT polymer shows excellent mixed ionic/electronic conductivity and surface-controlled electrochemical reaction mechanism, which significantly enhances the performance of LiNi0.8Co0.15Al0.05O2 (NCA) electrode and improves the NCA-Nb2O5 battery. However, the effectiveness of P(NDI2OD-T2) is limited by its poor stability at low voltage.