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<p>Lithium iron sulfide (Li<sub>2</sub>FeS<sub>2</sub>) exhibits unique characteristics, including multielectron redox behavior and abundant valence states, making it a promising candidate for electrode material in lithium-ion batteries. However, the sluggish charge transfer kinetics, low stability, and slow rate performance hamper its practical application. Herein, we propose a strategy to boost the electrochemical performance of Li<sub>2</sub>FeS<sub>2</sub> by substituting F dopants with S sites through a two-step solid-state process. The effects of F dopants on material characteristics and electrochemical behaviors are investigated. Experimental results show that F dopants significantly enhance diffusion kinetics and rate performance, indicating improved interfacial activity in Li<sub>2</sub>FeS<sub>2−x</sub>F<sub>x</sub>. Theoretical calculations confirm that F substitution occurs at the S site, enhancing charge mobility. After 100 cycles, the optimized Li<sub>2</sub>FeS<sub>2-x</sub>F<sub>x</sub> cathode exhibits a specific capacity of 250 mAh g<sup>−1</sup>, higher than pristine Li<sub>2</sub>FeS<sub>2</sub>. The improved electrochemical properties, diffusion kinetics, capacity, and rate performance are attributed to the enhanced structural stability from a stronger metal–fluorine bond compared to metal–sulfur, and increased Li<sup>+</sup> ion diffusion due to a greater electronegativity difference.</p>

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Improved electrochemical kinetics and rate performance of lithium-ion batteries by Li2FeS2−xFx cathode materials

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月8日

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  • Adane Gebresilassie Hailemariam,
  • Mohammad Qorbani,
  • Tadios Tesfaye Mamo,
  • Raghunath Putikam,
  • Chih-Yang Huang,
  • Khasim Saheb Bayikadi,
  • Heng-Liang Wu,
  • Ming-Chang Lin,
  • Li-Chyong Chen,
  • Kuei-Hsien Chen

摘要

Lithium iron sulfide (Li2FeS2) exhibits unique characteristics, including multielectron redox behavior and abundant valence states, making it a promising candidate for electrode material in lithium-ion batteries. However, the sluggish charge transfer kinetics, low stability, and slow rate performance hamper its practical application. Herein, we propose a strategy to boost the electrochemical performance of Li2FeS2 by substituting F dopants with S sites through a two-step solid-state process. The effects of F dopants on material characteristics and electrochemical behaviors are investigated. Experimental results show that F dopants significantly enhance diffusion kinetics and rate performance, indicating improved interfacial activity in Li2FeS2−xFx. Theoretical calculations confirm that F substitution occurs at the S site, enhancing charge mobility. After 100 cycles, the optimized Li2FeS2-xFx cathode exhibits a specific capacity of 250 mAh g−1, higher than pristine Li2FeS2. The improved electrochemical properties, diffusion kinetics, capacity, and rate performance are attributed to the enhanced structural stability from a stronger metal–fluorine bond compared to metal–sulfur, and increased Li+ ion diffusion due to a greater electronegativity difference.