Bimetallic Sulfides Cr<sub>0.99</sub>V<sub>1.8</sub>S<sub>4</sub> with Loosely Packed Structure: Exploring the Boundary of Conversion and Intercalation Sodium-Ion Storage Mechanism.

Hu, Keyan; Chen, Wen; Pan, Youtan; Li, Shuai; Lv, Zhuoran; He, Yuting; Zheng, Chong; Huang, Fuqiang et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Metal sulfide electrodes for sodium-ion batteries face trade-offs among high capacity, fast kinetics, and stability. The challenge lies in breaking and restoring metal-sulfur bonds and allowing rapid ionic transport. Here we explore the boundary of conversion- and intercalation-type metal sulfides to develop ideal sodium-ion storage materials. We focus on sulfides of vanadium and chromium because of their adjacent atomic numbers but different energy storage mechanism. Among various sulfides of vanadium and chromium, a loosely packed bimetallic sulfide, Cr<sub>0.99</sub>V<sub>1.8</sub>S<sub>4</sub>, with cationic vacancies and metallic conductivity (4.28 S m<sup>-1</sup>), shows optimal sodium-ion storage performance: an initial Coulombic efficiency of 95.6%, a reversible capacity of 551 mAh g<sup>-1</sup> at 1.6 C, and maintaining 100% capacity after 600 cycles at a high rate of 16-66 C.