Co3O4 hollow microspheres on polypyrrole nanotubes network enabling long-term cyclability sulfur cathode

Abstract

The advancement of lithium-sulfur batteries has still been thwarted by the shuttle effect and low conductivity, as well as volumetric expansion of sulfur until now. Herein, we designed a sulfur@Co3O4/polypyrrole cathode of lithium-sulfur batteries, in which sulfur was permeated into Co3O4 hollow microspheres and then embedded into the conductive network of polypyrrole (PPy) nanotubes together. The S@Co3O4/PPy cathode showed an impressive long-term cyclability with a retaining discharge capacity of 370.6 mAh g−1 after 1000 cycles at 0.5 C and a low decay rate of 0.034 % per cycle at 1 C over 1900 cycles. Moreover, at high constant current of 3 C or 5 C within 1000 cycles, the batteries still guaranteed an enough capacity output of 180.2 or 135.9 mAh g−1. The long-term cyclability of S@Co3O4/PPy composite was the synergistically attributed to the polar adsorption and encapsulation of Co3O4 hollow microspheres for sulfur particles or polysulfides, and the improving conductivity of PPy nanotubes, which was effective to restrain the shuttle effect, relieve the volumetric expansion and increase the diffusion kinetics.