Freestanding Fe_0.4Co_8.6S₈Nanotube/Nanosheet Arrays on Carbon Cloth as a Host for High-Performance Li/SeS₂Batteries

To inhibit the shuttle effect and promote the electrochemical performance of the Li/SeS2 batteries, the three-dimensional (3D) conductive composite of freestanding Fe0.4Co8.6S8 nanotube/nanosheet arrays on carbon cloth (CC@Fe0.4Co8.6S8) is designed and synthesized to host SeS2. The integrated host appears in the form of the Fe0.4Co8.6S8 nanosheets growing on the surface of nanotubes supported by carbon cloth, which provides a great surface area and offers secondary protection from nanosheets against shuttle of polyselenides/sulfides on the basis of nanotubes. Such enhanced physical confinement, along with chemical immobilization of the polar Fe0.4Co8.6S8, ensures high capability to adsorb polyselenides/sulfides. The well-constructed conductive network facilitates the fast redox reaction to lessen the dissolution and diffusion of polyselenides/sulfides. It was demonstrated by the adsorption test and explained by the systematic self-discharge experiments. As a result, upon the elevated current density and/or SeS2 loading, the deliberately designed architecture of CC@Fe0.4Co8.6S8 can exhibit large reversible capacity as well as great energy density. Specifically, with the areal loading of 2 mg cm-2, the CC@Fe0.4Co8.6S8/SeS2 electrode delivers high discharge capacity of 888 mAh g-1 at 1.0 A g-1 and excellent rate capability (585 mAh g-1 at 4.0 A g-1). In addition, with the areal loading increasing to 3.6 mg cm2, the cathode still reaches an ultrahigh capacity of 703 mAh g-1 at 1.0 A g-1. Upon further increasing SeS2 loading to 4.8 mg cm2, the corresponding areal energy density reaches 8.05 mWh cm-2 at 0.2 A g-1. This contribution adopts a less complex structure to address the issues in Li/SeS2 batteries. The effectiveness of shuttle inhibition is explained quantitatively through a systematic study on self-discharge phenomena, besides the electrochemical performance.