High performance lithium–sulfur batteries with a permselective sulfonated acetylene black modified separator

Abstract

The lithium–sulfur (Li–S) battery is one of the most fascinating candidates for next-generation storage devices due to its remarkably high theoretical energy density of 2600 W h kg⁻¹ and the low cost of the sulfur element. However, its actual application is still hindered by multiple challenges, such as the insulating nature of sulfur, irreversible loss of active material, and degradation of Li–metal anodes. In this paper, a functional sulfonated acetylene black (AB-SO₃⁻) coated separator is designed to improve the overall performance of Li–S batteries. The AB-SO₃⁻ coated separator is highly permselective to lithium ions against polysulfide anions, while the incorporation of AB-SO₃⁻ coated separator does not influence the ion conductivity. Also the AB-SO₃⁻ coating could function as an upper current collector to facilitate electron transport for enhancing the electrochemical utilization of sulfur and ensuring the reactivation of the trapped active material. Therefore, the Li–S cell with the AB-SO₃⁻ coating exhibits significant improvement in both reversible capacity and cycling stability as compared to the cell with the pristine Celgard separator. When the mass of the AB-SO₃⁻ coating is counted into the whole mass of the sulfur cathode, the Li–S cell exhibits a high sulfur content of 70 wt% in the whole sulfur cathode region and 3.0 mg cm⁻² sulfur mass loading. This kind of a cell delivers a high initial capacity of 1262 mA h g⁻¹, and a superior capacity of 955 mA h g⁻¹ was retained after 100 cycles at 0.1C. Consequently, the sulfonated carbon coated separator is promising for the construction of high performance batteries.