# Correlated Dual‐Gradient Electrodes Enabling Spatially Synchronized Sulfur Redox in High‐Mass‐Loading Li–S Batteries Under High Current Densities

## TL;DR

A new electrode design for lithium-sulfur batteries improves performance by synchronizing sulfur reactions across the electrode, enabling high energy and power density.

## Contribution

A dual-gradient electrode with spatially synchronized redox reactions is introduced to address polarization issues in high-mass-loading Li–S batteries.

## Key findings

- The Li2S@Fe2O3/Fe-N-C electrode achieves 22.7 mAh cm−2 at 0.1 C and 15.7 mAh cm−2 at 5 C.
- The design retains 82% capacity over 1100 cycles at 4 C and delivers 403 Wh kg−1 in a single-layer pouch cell.
- The dual-gradient structure reduces concentration, ohmic, and electrochemical polarization in thick electrodes.

## Abstract

The practical deployment of Li–S batteries is hindered by sluggish redox kinetics and poor ion transport in high‐mass‐loading sulfur cathodes, especially under fast‐charging and high‐power‐density conditions. Conventional electrocatalyst‐based strategies partially mitigate electrochemical polarization by lowering reaction energy barriers but fail to address concentration and ohmic polarization, which become more pronounced in thick electrodes. Here, a coupled material‐architecture approach is demonstrated by integrating electrocatalysts into a low‐tortuosity, correlated dual‐gradient electrode, fabricated via programmable high‐resolution stereolithography and pyrolysis‐induced carbonization. The microscale pore gradient is deliberately correlated with the active‐material gradient to spatially synchronize redox progression across electrode depth, thereby homogenizing cathode utilization and alleviating concentration polarization. Pyrolysis generates additional nanoscale pores, establishing a hierarchical structure and transforming polymer‐salt precursors into a conductive carbon framework embedding Li2S@Fe2O3/Fe‐N‐C, enhancing ion accessibility and minimizing ohmic polarization, while Fe2O3/Fe‐N‐C accelerates polysulfide conversion, reducing electrochemical polarization. Benefiting from this synergy, the Li2S@Fe2O3/Fe‐N‐C electrode delivers high‐areal‐capacities of 22.7 mAh cm−2 (1048 mAh g−1) at 0.1 C, 15.7 mAh cm−2 (725 mAh g−1) at 5 C, and retains 82% capacity over 1100 cycles at 4 C. A single‐layer pouch cell achieves a specific energy of 403 Wh kg−1, demonstrating the promise of this dual‐gradient strategy for real‐world high‐energy and high‐power Li–S batteries.

Coupling a dual‐gradient carbonized framework with Fe2O3/Fe‐N‐C catalytic sites enables spatially synchronized sulfur redox across the entire electrode thickness in high‐mass‐loading Li–S batteries. This synergistic structural–catalytic design effectively mitigates concentration, ohmic, and electrochemical polarization, thereby achieving high‐capacity utilization rates under both high areal mass loading and fast‐charging conditions, advancing the practical realization of high‐energy‐ and high‐power‐density Li–S batteries.