Polysulfide-inhibiting, thermotolerant and nonflammable separators enabled by DNA co-assembled CNT/MXene networks for stable high-safety Li–S batteries

Lithium–sulfur (Li–S) batteries are considered as next-generation power sources for portable electronic devices and electric vehicles. However, the shuttle effect of lithium polysulfides (LiPSs) and safety concerns of thermal runaway triggered by combustible battery components are still critical obstacles, severely limiting their practical application. Herein, we report a multifunctional separator composed of deoxyribonucleic acid (DNA)-carbon nanotube (CNT) and Ti3C2Tx MXene hybrid-modified polypropylene (PP) (denoted as DNA-CNT/MXene/PP) via a facile vacuum filtration approach. Through constructing the multi-synergistic interactions among DNA, CNT and MXene, the optimized 3D interconnected networks not only produce excellent physical plugging/chemical anchoring capability for the shuttled polysulfides and improved electrolyte wettability, but also exhibit high-temperature tolerance (even at 180 °C) and flame retardancy. Consequently, using the DNA-CNT/MXene/PP separator, the Li–S batteries exhibited outstanding ability to operate over wide temperatures range from 25 to 100 °C. Specifically, at room temperature, the sulfur cathode with the assistance of the DNA-CNT/MXene interface delivered an initial discharge capacity of 798 mAh g−1 and retained 592 mAh g−1 with an extremely low-capacity decay rate of 0.13% per cycle at 1 C. Another exciting feature of applying modified separators was that the Li–S batteries exhibited 79% capacity retention over 200 cycles at an elevated temperature of 75 °C. This paper provides an innovative concept for designing stable high-safety Li–S batteries.