# Pisiform Homojunction with Energy Band Bending Induced via Co-Implantation Design Enabling Fast-Charging Sodium-Sulfur Battery

## TL;DR

A new battery design using a 'homojunction' concept improves charging speed and performance in sodium-sulfur batteries.

## Contribution

The novel 'induced-homojunction' concept is first applied to sodium-sulfur batteries to enhance fast-charging capabilities.

## Key findings

- The battery retains 88.8% capacity at 1 A g−1 and maintains stable discharge capacity even at 5 A g−1.
- The v6Fe–Mo2C/C@S cathode achieves 1508 mAh g−1 at 0.1 A g−1 and 1337 mAh g−1 at 1 A g−1.
- The design enables rapid carrier transmission and efficient polysulfide capture, suppressing shuttling effects.

## Abstract

A novel “induced-homojunction” concept is first applied to achieve fast-charging Na–S batteries.Homojunction interface regulation enables high-efficiency NaPSs capture and fast conversion reaction kinetics.Na–S battery shows high specific capacity and superior rate performance with ultrahigh capacity retention up to 88.8% at 1 A g−1. And the battery delivers a stable discharge capacity independently from the charging rate (even at 5 A g−1).

A novel “induced-homojunction” concept is first applied to achieve fast-charging Na–S batteries.

Homojunction interface regulation enables high-efficiency NaPSs capture and fast conversion reaction kinetics.

Na–S battery shows high specific capacity and superior rate performance with ultrahigh capacity retention up to 88.8% at 1 A g−1. And the battery delivers a stable discharge capacity independently from the charging rate (even at 5 A g−1).

The online version contains supplementary material available at 10.1007/s40820-026-02163-2.

A novel “induced-homojunction” concept proposed here is of great significance to alleviate the severe shuttling effects and poor rate-capability behavior, where the sandwiched p-n Mo2C homojunction/carbon composite is constructed by the co-implantation design of Fe and Mo-vacancy (v6Fe–Mo2C/C), enabling heterogeneous variation in n/p-type characteristics among adjacent crystal structure. Encouringly, the p-n homojunction formation with continuous band bending favors the rapid carrier transmission across the interface to endow reactive sites with high activity and strengthen polysulfides capture, hence promoting original S–S bonds cleavage, which is regarded as the critical step to suppress the shuttling-behavior and trigger conversion reactions occurrence. Crucially, high-speed ions/electrons transport effectively driven by the formed large-range internal-electric-field during the energy band alignment, ensures they timely reach the above-mentioned highly active sites and react fully, enabling the ultrafast conversion kinetics process. A conspicuous sulfur utilization (1508 mAh g−1 at 0.1 A g−1) and especially the superior rate performance (1337 mAh g−1 at 1 A g−1) are presented by the battery with v6Fe–Mo2C/C@S cathode. And the battery delivers a stable discharge capacity independently from the charging rate (even at 5 A g−1). This “induced-homojunction” concept achieves the significant reaction kinetics advantage to provide new insight for the exploitation of fast-charging Na–S batteries.

The online version contains supplementary material available at 10.1007/s40820-026-02163-2.