Reduced shuttle effect by dual synergism of lithium–sulfur batteries with polydopamine-modified polyimide separators

Polydopamine (PD) for polyimide (PI) separator coated-modification is investigated for lithium-sulfur (Li–S) battery. The asymmetric single-sided PI-PD separator is achieved by in-situ self-polymerization. According to testing, batteries obtain the best performances when PD loading is 0.8 mg cm−2. Li–S battery with PD as a separator coating shows excellent electrochemical performance and high security. At 0.5C, battery with PI-PD obtains an initial discharge specific capacity of 1404.7 mAh g−1, and it can be retained at 890.5 mAh g−1 after 100 cycles. A high specific capacity of 710 mAh g−1 is obtained at 5 C. The PD modified layer possesses abundant N, O-containing functional groups which has strong chemical adsorption with the polysulfides. At the same time, the PD layer formed on PI is a dense layer which can be used as a physical barrier. That means polysulfides can be effectively suppressed by both chemical adsorption and physical obstruct in batteries with PI-PD separators. Besides, the PI-PD separator improves the safety of battery because the thoroughly thermal runaway temperature of battery with PI-PD can be as high as 300 °C. Therefore, the introduction of PD as a material for coated separator is a promising method using in Li–S battery.