Insight into the effect of cerium dioxide nanoparticle modified cobalt phosphide as an efficient electrocatalyst for high-performance lithium-sulfur battery

Abstract

Developing high-efficient catalyst is an effective strategy to boost the hysteretic polysulfide conversion behavior of lithium-sulfur (Li-S) battery. 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 challenging as well. Herein, aiming to optimize the corresponding catalytic activity of CoP, cerium dioxide (CeO2) is explored to regulate the electronic structure of CoP, and the sulfur conversion capability and the electrochemical performance in Li-S battery using the obtained CoP/CeO2 nanocomposites are demonstrated. The microstructure analysis demonstrates that CeO2 nanoparticle can embed in CoP and increase the exposed active sites, the introduced CeO2 can adjust the electronic structure and optimize the charge transfer and polysulfide conversion behavior. Although DFT indicates a moderate adsorption energy of CoP/CeO2 to Li2S6, the practical catalytic activity depends strictly on the amount of CeO2, and the optimum is ~10 mol %. The Li-S battery with CoP/CeO2-10 modified separator exhibits high specific capacity of 1400 mAh g-1 at 0.1 C, excellent rate performance (722 mAh g-1 at 3 C) and long-term cyclic durability (535 mAh g-1 at 1 C after 1000 cycles). This work expands the range of CoP-based catalysts based on CeO2 in Li-S battery.