Comparative Study of PEDOT- and PEDOT:PSS Modified δ-MnO₂ Cathodes for Aqueous Zinc Batteries with Enhanced Properties

Chemically synthesized layered manganese dioxide (δ-MnO2) modified by poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) dispersion were used as cathode materials for aqueous Zn-ion batteries (AZIBs). A comparative study of electrochemical properties of cathodes with pristine MnO2 and materials chemically modified by conducting polymers in different forms was performed with cycling voltammetry and galvanostatic charge-discharge curves in Zn2+-containing electrolyte solutions. The results of electrochemical tests indicate the significant improvement in specific capacity of electrodes in the sequence MnO2, MnO2/PEDOT and MnO2/PEDOT:PSS composites. The MnO2/PEDOT:PSS electrode delivered a specific discharge capacity of 278 mAh·g−1 at a current density 0.3 A·g−1 after 100 cycles, whereas for MnO2/PEDOT and MnO2 electrodes the values were 238 and 121 mAh·g−1 (capacity retention is 99%, 99.5% and 89%, respectively). These specific capacity values obtained for manganese dioxide-based cathodes are demonstrating the positive role of intrinsically conducting polymer, especially in case of surface modification of electroactive particles by PEDOT:PSS dispersion.