Poly(3,4-ethylenedioxythiophene) Decorated FeS2@C Hollow Nanospheres Toward High Performance Lithium–Sulfur Batteries

Abstract

Lithium–sulfur batteries are particularly prominent among many energy storage devices due to their excellent theoretical specific capacity (1675 mAh g^–1) and energy density (2600 kW h^–1), low cost, and environmental friendliness. However, such outstanding devices suffer from the low conductivity of elemental sulfur and discharge product, the drastic volume changes during charge and discharge processes, and the shuttle effect caused by soluble lithium polysulfides (LiPSs) dissolved in the electrolyte. In this work, we design and synthesize a poly(3,4-ethylenedioxythiophene) (PEDOT) decorated FeS₂@C hollow nanospheres to act as the sulfur host to alleviate the above issues. The excellent catalytic properties of FeS₂ together with the superior electrical conductivity and chemical adsorption capacity of the PEDOT coating are combined together to hinder the shuttle effect at the same time. Through the phase structure and morphology characterization, the optimized parameters of PEDOT coating have been confirmed to be 100 μL EDOT monomer addition and polymerization for 10 min. Based on the Li₂S₆ adsorption, cyclic voltammetry (CV) test of the symmetric cells, and Li₂S nucleation experiment, the PEDOT@FeS₂@C-4 wt % cathode was proved to exhibit the highest catalytic activity on LiPSs. Through the CV curves with different scan rates and the charge–discharge curves collected with the help of the galvanostatic intermittent titration technique (GITT), it is proved that appropriate PEDOT coating thickness is the key to improve the adsorption/catalytic ability on LiPSs. As a result, the PEDOT@FeS₂@C/S-4 wt % cathode can exhibit the highest initial capacity of 1435 mAh g^–1 at 0.1 C and remain at 893 mAh g^–1 after 100 cycles. Moreover, the capacity decay rate of the PEDOT@FeS₂@C/S-4 wt % cathode was confirmed to be 0.07% per cycle after 500 cycles at 1 C, also demonstrating an excellent cyclic stability.