MOF-derived Se doped MnS/Ti₃C₂T_x as cathode and Zn-Ti₃C₂T_x membrane as anode for rocking-chair zinc-ion battery

Mn-based zinc ion battery has the advantages of low cost and high performance, which makes it the promising energy storage system. However, the poor conductivity and the agglomeration in the synthesis process of manganese-based materials restrict the performance of batteries. Herein, the Se-doped MnS/Ti₃C₂T_x (Se-MnS/Ti₃C₂T_x) composite material derived from Mn-based metal-organic framework is reported. Electrochemical tests show that Se-doped could generate S defects and enhance the electrochemical activity of MnS. At the same time, the introduction of Ti₃C₂T_x substrate is conducive to exposing more sulfur defects and improving the utilization rate of defects. In the mechanism study, it is found that Se-MnS/Ti₃C₂T_x is transformed into S/Se co-doped Mn₃O₄ at the first charge, which innovatively elucidated the behavior of S/Se during activation. In the electrochemical performance test, the specific capacity can reach 74.7 mAh·g⁻¹ at 5.0 A·g⁻¹. In addition, the Zn-Ti₃C₂T_x membrane electrode is prepared by vacuum filtration as the zinc-poor anode, which is assembled into the rocking chair full battery to avoid dendrite growth and exhibit excellent rate performance. The addition of Zn²⁺ weakens the electrostatic repulsion between the interlayers of MXene, and the formation of the folded morphology aids the penetration of the electrolyte. At 1.0 A·g⁻¹, the capacity can reach 50.6 mAh·g⁻¹. This work is helpful to promote the research and development of the reaction mechanism of manganese based rocking chair batteries.