Precisely Designed Ultra-Small CoP Nanoparticles-decorated Hollow Carbon Nanospheres as Highly Efficient Host in Lithium-Sulfur Batteries.

Abstract

Designing porous carbon materials with metal phosphides as host materials holds promise for enhancing the cyclability and durability of lithium-sulfur (Li-S) batteries by mitigating sulfur poisoning and exhibiting high electrocatalytic activity. Nevertheless, it is urgent to precisely control the size of metal phosphides to further optimize the polysulfide conversion reaction kinetics of Li-S batteries. Herein, a subtlety regulation strategy was proposed to obtain ultra-small CoP nanoparticles-decorated hollow carbon nanospheres (CoP@C) by using spherical polyelectrolyte brush (SPB) as the template with stabilizing assistance from polydopamine coating, which also works as carbon source. Leveraging the electrostatic interaction between SPB and Co2+, ultra-small Co particles with sizes measuring 5.5 ± 2.6 nm were endowed after calcination. Subsequently, through a gas-solid phosphating process, these Co particles were converted into CoP nanoparticles with significantly finer sizes (7.1 ± 3.1 nm) compared to state-of-the-art approaches. By uniformly distributing the electrocatalyst nanoparticles on hollow carbon nanospheres, CoP@C facilitated the acceleration of Li ion diffusion and enhanced the conversion reaction kinetics of polysulfides through adsorption-diffusion synergy. As a result, Li-S batteries utilizing the CoP@C/S cathode demonstrated an initial specific discharge capacity of 850.0 mAh g-1 at 1.0 C, with a low-capacity decay rate of 0.03% per cycle.