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.

Keywords:

• Mesoporous carbon
• Co₃S₄
• lithium-sulfur batteries
• shuttle effect
• cathode

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

This project was supported by the National Natural Science Foundation of China (Grant Nos. 51578448, 51308447), Natural Science Basic Research Plan in Shaanxi Province of China (Program No. 2017ZDJC-18) and Technology Foundation for Selected Overseas Chinese Scholar, Ministry of Human Resources and Social Security of the People's Republic of China (Shan Ren She Han [2016]789).