# Combined In Situ EQCM‐Raman Study of Zn Storage Mechanism in Polyaniline for Zinc‐Ion Battery

## TL;DR

This study uses a new combined technique to understand how zinc is stored in polyaniline for batteries, showing that doping improves battery performance and stability.

## Contribution

A novel in situ EQCM-Raman method is introduced to study Zn storage in polyaniline for Zn-ion batteries.

## Key findings

- Anionic doping of polyaniline enhances structural stability and Zn cycling capability.
- Doped polyaniline retains 85% of its initial capacity after 300 cycles at 1 A g−1.
- XPS studies show doping reduces PANI oxidation, improving battery performance.

## Abstract

Zinc‐ion batteries (ZIBs) have attracted increasing attention as safe, cost‐effective, and environmentally friendly alternatives to lithium‐ion batteries for large‐scale energy storage. Among various cathode materials for Zn batteries, polyaniline (PANI) is a potential material that presents benefits such as high conductivity and pseudocapacitive behavior. However, it often suffers from limited cycling stability and structural degradation during repeated charge–discharge processes. Here, in situ electrochemical quartz crystal microbalance (EQCM)‐Raman technique is combined to understand the Zn storage behavior in PANI wherein limited Zn insertion is observed along with detachment of the polymer from the substrate. Through anion doping of PANI, the structural stability is enhanced, and the overall Zn cycling capability is improved. Ex situ X‐ray photoelectron spectroscopy (XPS) studies further reveal that doping of PANI significantly reduces the oxidation of PANI, which leads to an improved battery performance. The doped‐PANI shows a high specific capacity of 310 and 235 mAh g−1 at 0.25 and 1 A g−1, respectively, and retains 85% of its initial capacity after 300 cycles at 1 A g−1. These results reveal that it is important to understand the storage mechanism to develop useful strategies to improve ZIBs performance.

A new combined EQCM‐Raman analysis method of Zn storage mechanism in polyaniline is presented, from which changes in the polyaniline structure due to Zn insertion/extraction and doping/dedoping are revealed. By anionic doping of polyaniline, the capacity and stability of Zn‐ion batteries showed substantial improvement.