Promoting polythionate intermediates formation by oxygen-deficient manganese oxide hollow nanospheres for high performance lithium-sulfur batteries

Mediating polysulfides redox by forming surface-bound insoluble intermediates on metal oxides is an efficient strategy to curtail polysulfides shuttling. Herein, the formation of surface-bound insoluble intermediates is further promoted by surface engineering of manganese oxide host via introducing oxygen vacancies. Hollow MnO2 nanospheres are first synthesized via a facial hard-template method, which provide a huge void for sulfur immobilization and volumetric expansion. Surface oxygen vacancies are then introduced by heating the products in a reduction atmosphere. These oxygen vacancies are proposed to accelerate the formation of polythionate intermediates, and which can adsorb polysulfides species more strongly than normal oxide sites and assist in their dissociation to lithium sulfide. The cathode based on oxygen-deficient manganese oxide hollow nano- spheres achieves high initial discharge capacity of 1053 mAh g(-1) at 0.5 C and high reversible capacity of 551 mAh g(-1) at 2 C over 400 cycles, while only initial discharge capacity of 918 mAh g(-1) and reversible capacity of 410 mAh g(-1) are obtained for pristine MnO2. This work provides a novel strategy to establish cathode with engineered surface chemistry of metal oxides for high performance Li-S batteries.