Improving Electrochemical Performance and Safety of Lithium–Sulfur Batteries by a “Bulletproof Vest”

In the field of high-density energy storage, lithium–sulfur (Li–S) batteries have attracted more and more attention because of their high specific capacity and affordable cost. However, their actual implementation is hindered by the dissolution of polysulfides and severe safety concerns caused by flammable electrolytes. Herein, we report the preparation of an interlayer that can effectively suppress polysulfide shuttling and increase the working temperature range. In this work, polyamide nanofibers (ANFs) are used as the substrate material to prepare the Ni(OH)2@ANFs-Ni (NAFN) film that works as the interlayer on the “outside” of the cathode in situ. The experimental results show that Li–S batteries containing NAFN as the interlayer can achieve excellent outstanding stability in a long cycle life. After 800 cycles at 1 C, the capacity remains at 482 mA h/g, with a decay rate of 0.047%. At high temperature (60 °C), after 500 cycles at 1 C, its capacity is 622 mA h/g with a decay rate of 0.079%. Therefore, the flexible design of the NAFN interlayer provides the growth of high-performance Li–S batteries with novel insights. The ultrathin, microporous structure of the interlayer tightly wraps the cathode material, just like the addition of a “bulletproof vest” inside the Li–S batteries. The plentiful amide functional groups of the “bulletproof vest” enable the strong complexation reaction with polysulfides to suppress the polysulfides’ shuttling effect and ensure a facile Li+ transfer. At the same time, the nickel hydroxide is able to accelerate the redox kinetics via reaction with polysulfides to produce the intermediate thiosulfate groups. Also, the ANFs as the heat-resistant material ensure the stability of the batteries at high temperatures.