Biomimetic micro cell cathode for high performance lithium–sulfur batteries

Lithium-sulfur batteries have suffered from shuttle effects and active materials loss for decades, leading to the unsatisfying rate performance and cyclability. Here, inspired by red blood cells, commonly known as an important medium for oxygen transportation, we build a biomimetic micro cell by implement of Aspergillus niger-derived carbon decorated with TiO2-x nanoparticles as an efficient medium for energy storage. Red blood cell-mimetic micro cell can confine active materials inside the large space, with abundant and shortened electron/ion channels endowed by the biconcave structure. Meanwhile, the structure also shows excellent durability, so that once active materials have been loaded, the sufficient reaction sites would facilitate the stable adsorption and conversion of polysulfides for a long-term cycling, enabling to operate like the cell membranes with selective permeability and conversion ability. The as-prepared micro cell cathode demonstrates great application potential, delivering the discharge capacities of 995 and 720 mAh g−1 after 500 and 700 cycles at 0.5 and 2 C, with the capacity retention around 80%. Density functional theory calculations further show that the oxygen defects can enhance the chemisorption ability of polysulfides, as well as expedite redox reactions of polysulfides by facilitating surface ion transportation.