# Composite Polymer Electrolytes with Tailored Ion-Conductive Networks for High-Performance Sodium-Ion Batteries

## TL;DR

This paper introduces a new composite polymer electrolyte that improves the performance of sodium-ion batteries by enhancing ion conductivity and stability.

## Contribution

The novel composite structure combines a perovskite material with a polymer matrix to achieve high ionic conductivity and electrochemical stability.

## Key findings

- The GPE-Eh formulation achieved an ionic conductivity of 2.14 × 10−3 S·cm−1 and a sodium-ion transference number of 0.66.
- GPE-Eh enabled stable sodium plating/stripping for over 600 hours with low polarization in symmetric cells.
- In Na|GPE|NVP cells, GPE-Eh retained ~79% of its capacity after 500 cycles and recovered ~89% after high-rate cycling.

## Abstract

Gel-polymer electrolytes offer a promising route toward safer and more stable sodium-ion batteries, but conventional polymer systems often suffer from low ionic conductivity and limited voltage stability. In this study, we developed composite GPEs by embedding methylammonium lead chloride (CH3NH3PbCl3, MPCl) into a UV-crosslinked ethoxylated trimethylolpropane triacrylate (ETPTA) matrix, with sodium alginate (SA) as an ionic conduction enhancer. Three types of membranes—GPE-P, GPE-El, and GPE-Eh—were synthesized and systematically compared. Among them, the high-MPCl formulation (GPE-Eh) exhibited the best performance, achieving a high ionic conductivity of 2.14 × 10−3 S·cm−1, a sodium-ion transference number of 0.66, and a wide electrochemical window of approximately 4.9 V vs. Na+/Na. In symmetric Na|GPE|Na cells, GPE-Eh enabled stable sodium plating/stripping for over 600 h with low polarization. In Na|GPE|NVP cells, it delivered a high capacity retention of ~79% after 500 cycles and recovered ~89% of its initial capacity after high-rate cycling. These findings demonstrate that the perovskite–polymer composite structure significantly improves ion transport, interfacial stability, and electrochemical durability, offering a viable path for the development of next-generation quasi-solid-state sodium-ion batteries.