# Unveiling a Stable Polysulfide Transport Framework in a Fluorine‐Free Li‐S Batteries

## TL;DR

A fluorine-free electrolyte for lithium-sulfur batteries improves performance by creating a stable framework that reduces polysulfide shuttling and enhances cycle life.

## Contribution

A fluorine-free phosphate-based electrolyte enables a new redox mechanism in Li-S batteries, shifting to a Li3PS4-Li2S pathway with improved stability.

## Key findings

- The new electrolyte achieves a stable capacity of 765 mAh g−1 over 200 cycles.
- The Li-P-S framework suppresses polysulfide diffusion and promotes solid-state-like behavior.
- Dynamic phase transitions in Li-P-S complexes drive reversible conversion and sustained performance.

## Abstract

Lithium‐sulfur batteries are limited by severe polysulfide shuttling, unstable lithium interfaces, and parasitic redox reactions, which degrade cycle life and efficiency. These issues stem from the soluble nature of polysulfide intermediates and the poor interfacial control in conventional electrolytes. Herein, we report a fluorine‐free phosphate‐based electrolyte that fundamentally shifts the redox chemistry from the typical S8‐Li2S pathway to a reversible Li3PS4‐Li2S mechanism. This in situ transformation produces Li‐rich thiophosphate phases that suppress polysulfide diffusion, alleviate cathode expansion, and promote solid‐state‐like behavior. Spectroscopic and microscopic analyses revealed dynamic phase transitions within the Li‐P‐S complexes that drive reversible conversion and sustained performance. As a result, the cells delivered a stable capacity of 765 mAh g−1 over 200 cycles. This work presents a fluorine‐free electrolyte design that establishes a new class of solid‐state‐like Li‐S redox chemistry, offering a promising route toward durable, high‐performance lithium‐sulfur batteries.

This work unveils a lithium thiophosphate reaction pathway activated by trigger P2S5 units, which initiate fast self‐assembly and shift the system away from conventional Li‐S reactions. The reversible Li‐P‐S framework delivers stability, safety, and high energy density, while enabling a distinct solid‐liquid hybrid electrochemical mode that provides a viable route for next‐generation sulfur‐based energy storage.