# Development of a Reflective Electrochromic Zinc-Ion Battery Device for Infrared Emissivity Control Using Self-Doped Polyaniline Films

## TL;DR

This paper introduces a new type of battery device that can control infrared emissivity and visible color, useful for smart camouflage and displays.

## Contribution

A reflection-type electrochromic zinc-ion battery using self-doped polyaniline for IR emissivity control and visible color change.

## Key findings

- The device achieves emissivity modulation ranges of 0.28 (3–5 μm) and 0.19 (8–14 μm).
- It shows a visible color change from earthy yellow to deep green.
- The battery maintains 80% capacity after 5000 cycles.

## Abstract

Electrochromic devices (ECDs) capable of modulating both visible color and infrared (IR) emissivity are promising for applications in smart thermal camouflage and multifunctional displays. However, conventional transmissive ECDs suffer from limited IR modulation due to the low IR transmittance of transparent electrodes. Here, we report a reflection-type electrochromic zinc-ion battery (HWEC-ZIB) using a self-doped polyaniline nanorod film (SP(ANI-MA)) as the active layer. By positioning the active material at the device surface, this structure avoids interference from transparent electrodes and enables broadband and efficient IR emissivity tuning. To prevent electrolyte-induced IR absorption, a thermal lamination encapsulation method is employed. The optimized device achieves emissivity modulation ranges of 0.28 (3–5 μm) and 0.19 (8–14 μm), delivering excellent thermal camouflage performance. It also exhibits a visible color change from earthy yellow to deep green, suitable for various natural environments. In addition, the HWEC-ZIB shows a high areal capacity of 72.15 mAh cm−2 at 0.1 mA cm−2 and maintains 80% capacity after 5000 cycles, demonstrating outstanding electrochemical stability. This work offers a versatile device platform integrating IR stealth, visual camouflage, and energy storage, providing a promising solution for next-generation adaptive camouflage and defense-oriented electronics.