# Functional Polymers for Ionic Thermoelectrics: Multiscale Design Strategies for Ion Dynamics, Mechanics, and Energy Harvesting

## TL;DR

This paper reviews how functional polymers improve ionic thermoelectric devices for energy harvesting by influencing performance at multiple scales.

## Contribution

The paper provides a multiscale analysis of polymer roles in enhancing ionic thermoelectric performance and outlines future research directions.

## Key findings

- Functional polymers significantly influence the performance and mechanical properties of quasi-solid-state ionic thermoelectrics.
- Molecular-, micro-, and macro-scale engineering of polymers are critical for optimizing ion dynamics and energy harvesting.
- Current challenges include improving polymer-ion interactions and scalability for practical energy harvesting applications.

## Abstract

The efficient conversion of dissipated heat into useful electrical energy has emerged as a promising approach for sustainable energy technologies. Ionic thermoelectrics (iTEs) are particularly attractive because they generate substantial thermo‐voltages, effectively harvest low‐grade heat, and offer advantages such as cost‐effectiveness, easy scalability, and remarkable performance. Unlike liquid‐state platforms, quasi‐solid‐state iTEs exhibit properties that are critically governed by the polymer matrix and polymer‐ion interactions, which are closely related to the overall device performance. Consequently, the use of functional polymers effectively improves the characteristics and performance of quasi‐solid‐state iTEs. Therefore, this paper highlights the impact of the polymer matrix on performance and mechanical properties in iTEs from molecular‐, micro‐, to macro‐scale engineering. Particular emphasis is placed on clarifying the role of polymers at various scales to provide an in‐depth understanding of performance enhancement. Furthermore, the current challenges and prospective research directions are discussed, offering guidance toward the development of next‐generation iTE‐based energy harvesting platforms.

This review highlights the impact of the polymers at the molecular‐, micro‐, and macro‐scale engineering. Particular emphasis is placed on their roles at different scales to provide an in‐depth understanding of performance improvement. In addition, current challenges and potential research approaches are discussed, outlining directions for the future development of iTE‐based energy harvesting systems.