# Sulfonylimide-Based Single-Ion-Conducting Porous Organic Polymer Electrolytes for Enhanced Performance of Solid-State Lithium Batteries

## TL;DR

A new type of solid-state electrolyte is developed to improve lithium battery performance by reducing polarization and enhancing stability.

## Contribution

A novel lithium sulfonylimide-based single-ion-conducting porous organic polymer electrolyte is designed to suppress anion mobility and enhance Li+ transport.

## Key findings

- The Li-SSP composite electrolyte shows high ionic conductivity (4.04 × 10–4 S cm–1) and a Li+ transference number of 0.70.
- Li||Li symmetric cells using Li-SSP demonstrate stable plating/stripping for over 400 h with low overpotential.
- LiFePO4 half-cells with Li-SSP deliver high capacity retention (96.1% after 300 cycles) and reduced interfacial resistance.

## Abstract

The development of
solid-state electrolytes with high ionic conductivity
and interfacial stability is vital for next-generation lithium-ion
batteries. Concentration polarization in conventional electrolytes
accelerates solid electrolyte interphase (SEI) and cathode electrolyte
interphase (CEI) growth, thereby limiting cycle life and reliability.
Here, we report a lithium sulfonylimide-based single-ion-conducting
porous organic polymer (Li-SSP) electrolyte designed to suppress anion
mobility and enhance Li+ transport. The Li-SSP was synthesized
via Sonogashira coupling of 4-bromo-N-((4-aminophenyl)­sulfonyl)­benzenesulfonamide
with 1,3,5-triethynylbenzene. Fourier-transform infrared spectroscopy
confirmed its chemical structure, while Brunauer–Emmett–Teller
analysis revealed coexisting mesoporous and microporous architectures
with a high surface area of 271 m2 g–1. The immobilized anionic groups in the porous framework provide
continuous Li+ conduction pathways, effectively reducing
concentration polarization and improving electrochemical stability.
The lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI)/poly­(vinylidene
fluoride-co-hexafluoropropylene) (PVDF-HFP)/Li-SSP
composite electrolyte exhibits a high ionic conductivity of 4.04 ×
10–4 S cm–1 at 30 °C and
a high Li+ transference number of 0.70, significantly higher
than that of LiTFSI/PVDF-HFP electrolytes (0.18). A Li||Li symmetric
cell demonstrates stable Li plating/stripping for over 400 h with
low overpotential, confirming excellent interfacial compatibility.
A LiFePO4 half-cell with the Li-SSP composite electrolyte
delivers high capacities of 148.1 mAh g–1 at 0.2
C and 86.7 mAh g–1 at 5 C, along with 96.1% capacity
retention after 300 cycles at 0.5 C. Scanning electron microscopy,
transmission electron microscopy, and X-ray photoelectron spectroscopy
analyses further confirm the formation of thinner and chemically stable
CEI films, resulting in reduced interfacial resistance. These results
highlight that rational design of Li-SSP electrolytes enables high
Li+ transference, robust interfacial stability, and extended
cycle life, offering a promising pathway toward safe and durable solid-state
lithium-ion batteries.