Designing conductive polymers as multifunctional electrochemical components for batteries and supercapacitors: Recent advances, mechanisms and design principles

Rapid development of electrified transport and other technologies including grid-scale renewables and wearable electronics has created a need for extensive electrochemical energy storage systems that provide high volumetric and gravimetric energy density, fast charge and discharge, and long life. Conductive polymers (CPs) offer the capability for electrochemical active, structural, and architecturally tunable materials in both batteries and supercapacitor systems. This review assesses advances in CPs (post 2020) focusing on the design of CPs including molecular design, hierarchy, doping, and nanostructures to improve conductivity, redox activity, and structural ability. CPs, via pseudocapacitance related to CPs, alleviates the solid-state diffusion limitation. In batteries, CPs have been used for the entrapment of sulfur and the immobilization of polysulfides in lithium-sulfur batteries, for stabilization of lithium and sodium battery electrolytes and cell interfaces, and for the creation of compliant solid electrolytes in battery systems. In supercapacitors, CPs have been used in highly effective nanocomposite systems incorporating carbon materials, transition-metal oxides, and MXenes, to provide high capacitance, improved cycling life, and enhanced rate of discharge. The cross-chemistry comparisons (batteries and supercapacitors) reveal design principles including selective doping, tailoring porosity and morphology, and engineered hybrid interfaces for improved charge transport and mechanical stability. These innovations place CPs as enablers of modern energy storage systems.