Porous carbon/Co3S4 hollow polyhedron as sulfur carrier to enhance cyclic stability for lithium-sulfur batteries

Abstract

The lithium-ion battery is subject to the limited theoretical specific capacity of electrode materials, which is difficult to achieve capacity breakthrough. However, the theoretical specific capacity of the sulfur cathode for lithium-sulfur battery is 1675 mAh g−1 and the energy density is 2600 Wh kg−1. However, lithium-sulfur batteries suffer from three problems: “shuttle effect,” sulfur electron/ion insulation, and volume expansion. Moreover, the carbon materials or metal sulfides alone cannot achieve the dual effects of excellent conductivity and chemisorption as sulfur carriers. Therefore, 350 nm and 1 μm of polyhedron with mesoporous carbon and Co3S4 were prepared (denoted as C/Co3S4@S (S) for the small one and C/Co3S4@S (L) for the large one, respectively) using PVP modified self-assembled Co-MOFs as a sacrificial template. The C/Co3S4 (S) carrier provided a sulfur-filled channel, and shortened the electron transport path with excellent conductivity. Simultaneously, the polar Co3S4 chemisorption of polysulfide and hollow structure provided a sufficient storage for sulfur. As the cathode of lithium-sulfur battery, C/Co3S4@S (S) exhibited an initial capacity of 1153 mAh g−1 at 0.5 C, and the capacity decay rate per cycle is only 0.057% during 500 cycles at 1 C, compared to 1 μm C/Co3S4@S (L) efficiently improved the cycle stability.