Encapsulating sulfur in δ-MnO2 at room temperature for Li-S battery cathode

Abstract Sulfur is a promising alternative lithium battery cathode for its low cost, abundance, and high specific capacity. However, issues of rapid capacity decay and low coulombic efficiency hamper its practical application pace owing to polysulfides dissolution. Despite efforts on hybridizing sulfur with metal oxides to solve these issues are considered to be effective, the synthesis of hybrid materials is always tedious. Herein, S@MnO 2 hybrid material was synthesized via a green method at room temperature. We encapsulate S spheres in poly-dopamine (PDA) by in-situ polymerization of dopamine. The formed PDA shell is served as reducing agent and sacrificial template to transform KMnO 4 into δ-MnO 2 shell without adding any other agents (such as acid). δ-MnO 2 encapsulates the S spheres uniformly and succeeded in entrapping polysulfides when S@MnO 2 used for Li–S battery, endowing the S@MnO 2 cathode with high reversible capacity, improved cycling stability, and satisfied coulombic efficiency. Moreover, this method could be adopted for hybridizing δ-MnO 2 with diverse materials (such as CNTs@MnO 2 ) in mild reaction environment (ambient pressure and temperature), exhibiting an extensive application on constructing Mn-based oxide hybrid functional materials.