Novel N-doped carbon nanotubes impregnated Mn spheres with polydopamine coating as an efficient polysulfide immobilizer for Li-S batteries

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage and conversion devices due to the high theoretical capacity and cost-effectiveness of sulfur. However, they still suffer from sluggish redox kinetics and the shuttle effect caused by complex polysulfides. In this work, graphitic carbon nitride (g-C 3 N 4 ) is utilized as a template and further hydrothermally treated with an Mn source and glucose. The pyrolysis of g-C 3 N 4 gives rise to N-doped carbon nanotubes, producing abundant sites for physical confinement and chemical adsorption of polysulfides, while glucose carbonization brings forth amorphous carbon and Mn source produces metal spheres. Afterward, polydopamine (PDA) induces N-doped carbon coating and promotes interface connection as well as electron immigration. This synergistic design possesses a high surface area of micropores and mesopores to aggregate sulfur and accelerate redox kinetics. As a result, the N-doped carbon nanotube with Mn spheres and PDA coating@sulfur (CN/Mn-PDA@S) exhibits a high reversible capacity of 813.5 mAh g −1 at 1 C with a decay rate of 0.064% per cycle and remarkable capacity retention at 2 C with rate performance up to 4 C. Therefore, the novel design of N-doped carbon nanotubes with Mn spheres and PDA coating serves as an efficient polysulfide immobilizer for Li-S batteries. • G-C 3 N 4 nanotubes were used as a template and then hydrothermally treated with Mn. • Polydopamine (PDA) coating facilitates a heterojunction metal-free interface. • N-doped carbon nanotubes exhibit rich sites for chemical adsorption of polysulfides. • N-doped carbon nanotubes/Mn spheres/PDA coating act as an efficient polysulfide immobilizer.