Electrically Conductive Functional Polymers and Application Progress in Lithium Batteries

Electrically conductive functional polymers (ECFPs) have attracted much attention not only for their electron conductivity but also for their versatile properties, including redox activity, flexibility, and designability. These attributes are expected to enhance the energy density and mechanical compatibility of lithium batteries while mitigating the safety risks associated with such batteries. Furthermore, ECFPs are key candidates as active materials, current collectors, coatings, binders, and additives in energy storage and conversion systems, especially for the development of flexible batteries, dry electrodes, and solid-state batteries. However, their low electron conductivity, poor environmental stability, instability of dopants, and high costs limit their usage in production and large-scale applications. In this review, the two major electrically conductive functional polymer species with conjugated and radical structures are focused on to reveal their conductivity mechanisms. Moreover, the current strategies for improving the performance of these polymers are summarized, which include molecular design to optimize conjugated structures for enhanced conductivity, the addition of hydrophobic groups or protective coatings to improve environmental resistance, a side-chain design that is self-doping to introduce high-stability dopants, and the development of multifunctional systems through compositing with two-dimensional carbon-based materials. Additionally, green processes and renewable resource applications are also introduced with the aim of creating cost-effective and sustainable preparation technologies. The advancement of ECFPs in structural and performance engineering and optimization strategies will facilitate their potentially expansive applications in energy storage and conversion devices.