Insights into the application of cerium dioxide nanoparticle-modified cobalt phosphide as an efficient electrocatalyst for high-performance lithium–sulfur batteries

Abstract

Developing high-efficiency catalysts is an effective strategy to boost the hysteretic polysulfide conversion behavior of lithium–sulfur (Li–S) batteries. Cobalt phosphide (CoP) is a typical promising catalyst due to its inherent advantages such as good electron conductivity, facile synthesis route and moderate catalytic capability and binding energy to polysulfide. However, the design and fabrication of highly active CoP remains a challenge. Herein, aiming to optimize the catalytic activity of CoP, the regulation of the electronic structure of CoP by cerium dioxide (CeO₂) was explored, and the sulfur conversion capability and the electrochemical performance in Li–S batteries using the obtained CoP/CeO₂ nanocomposites were demonstrated. Microstructure analysis demonstrates that CeO₂ nanoparticles can embed in CoP and increase its exposed active sites, and the introduced CeO₂ can adjust the electronic structure and optimize the charge transfer and polysulfide conversion behavior of CoP. Although DFT indicates a moderate adsorption energy of CoP/CeO₂ towards Li₂S₆, practical catalytic activity depends strictly on the amount of CeO₂, and the optimum amount is ∼10 mol%. A Li–S battery with a CoP/CeO₂-10-modified separator exhibits a high specific capacity of 1400 mA h g⁻¹ at 0.1C, an excellent rate performance of 722 mA h g⁻¹ at 3C and a long-term cycling durability of 535 mA h g⁻¹ at 1C after 1000 cycles. This work expands the range of CoP-based catalysts based on CeO₂ in Li–S batteries.