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<p>The sluggish bidirectional conversion rate between Li<sub>2</sub>S<sub><i>n</i></sub> (2 ≤ <i>n</i> ≤ 4) and Li<sub>2</sub>S, coupled with the uncontrolled deposition of Li<sub>2</sub>S, significantly impedes the realization of high-performance lithium–sulfur batteries (LSBs). In this study, a metal–organic framework was employed as a precursor for the synthesis of a CoO<sub><i>x</i></sub>–CeO<sub>2−<i>y</i></sub>/C (0 &lt; <i>x</i> &lt; 3/2, 0 &lt; <i>y</i> &lt; 1/2) heterojunction via pyrolysis, which was subsequently introduced onto the cathode side of the polypropylene (PP) separator in LSBs. The modification of CoO<sub><i>x</i></sub>–CeO<sub>2−<i>y</i></sub>/C enhances the kinetics of converting of Li<sub>2</sub>S<sub><i>n</i></sub> to Li<sub>2</sub>S during the discharge process. The Tafel slope for the Li<sub>2</sub>S deposition reaction is reduced to 52.1&#xa0;mV/dec, representing a 56.6% decrease compared to LSBs with bare PP separator. Conversely, during the charging process, the modification lowers the energy barrier for the Li<sub>2</sub>S decomposition reaction, with the activation energy reduced to 6.12&#xa0;kJ/mol, indicating a 70.3% decrease relative to LSBs with PP separator only. Consequently, more Li<sub>2</sub>S is promoted to undergo decomposition. The CoO<sub><i>x</i></sub>–CeO<sub>2−<i>y</i></sub>/C heterojunction facilitates uniform deposition of Li<sub>2</sub>S, featuring fine particles and a uniform distribution, after brief potentiostatic charging for decomposition, thereby effectively mitigating the deactivation of sulfur species. Thanks to the enhanced bidirectional conversion of lithium polysulfides (LiPS) facilitated by the CoO<sub><i>x</i></sub>–CeO<sub>2−<i>y</i></sub>/C modification layer, the (−)Li|CoO<sub><i>x</i></sub>–CeO<sub>2−<i>y</i></sub>/C@PP|S(+) coin cell maintains a Coulombic efficiency of 90.4% after 500 cycles at a current density of 1 C, exhibiting a low capacity-decay rate of only 0.081% per cycle, thereby demonstrating excellent long-cycle stability.</p>

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MOF-Derived CoOx–CeO2−y/C Heterojunction Synergistically Promotes the Deposition and Decomposition of Li2S in Lithium–Sulfur Batteries

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  • 发表日期：

    2025年4月1日

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  • Ke Jia,
  • Yanan Zhang,
  • Rui Zuo,
  • Hongbing Lu,
  • Kemeng Ji,
  • Mingming Chen

摘要

The sluggish bidirectional conversion rate between Li2Sn (2 ≤ n ≤ 4) and Li2S, coupled with the uncontrolled deposition of Li2S, significantly impedes the realization of high-performance lithium–sulfur batteries (LSBs). In this study, a metal–organic framework was employed as a precursor for the synthesis of a CoOx–CeO2−y/C (0 < x < 3/2, 0 < y < 1/2) heterojunction via pyrolysis, which was subsequently introduced onto the cathode side of the polypropylene (PP) separator in LSBs. The modification of CoOx–CeO2−y/C enhances the kinetics of converting of Li2Sn to Li2S during the discharge process. The Tafel slope for the Li2S deposition reaction is reduced to 52.1 mV/dec, representing a 56.6% decrease compared to LSBs with bare PP separator. Conversely, during the charging process, the modification lowers the energy barrier for the Li2S decomposition reaction, with the activation energy reduced to 6.12 kJ/mol, indicating a 70.3% decrease relative to LSBs with PP separator only. Consequently, more Li2S is promoted to undergo decomposition. The CoOx–CeO2−y/C heterojunction facilitates uniform deposition of Li2S, featuring fine particles and a uniform distribution, after brief potentiostatic charging for decomposition, thereby effectively mitigating the deactivation of sulfur species. Thanks to the enhanced bidirectional conversion of lithium polysulfides (LiPS) facilitated by the CoOx–CeO2−y/C modification layer, the (−)Li|CoOx–CeO2−y/C@PP|S(+) coin cell maintains a Coulombic efficiency of 90.4% after 500 cycles at a current density of 1 C, exhibiting a low capacity-decay rate of only 0.081% per cycle, thereby demonstrating excellent long-cycle stability.