Mn 2+ -Doped MoS 2 /MXene Heterostructure Composites as Cathodes for Aqueous Zinc-Ion Batteries.

Typical layered transition-metal chalcogenide materials, especially MoS, are gradually attracting widespread attention as aqueous Zn-ion battery (AZIB) cathode materials by virtue of their two-dimensional structure, tunable band gap, and abundant edges. The metastable phase 1T-MoS exhibits better electrical conductivity, electrochemical activity, and zinc storage capacity compared to the thermodynamically stable 2H-MoS. However, 1T-MoS is still limited by the phase stability and layered structure destruction for AZIB application. Thus, a three-dimensional interconnected network heterostructure (Mn-MoS/MXene) consisting of Mn-doped MoS and MXene with a high percentage of 1T phase (82.9%) was synthesized by hydrothermal methods and investigated as the cathode for AZIBs. It was found that S-Mn-S covalent bonds between MoS interlayers and Ti-O-Mo bonds at heterogeneous interfaces can act as "electron bridges" to facilitate electron and charge transfer. And the doping of Mn and the combination of MXene not only expanded the interlayer spacing of MoS but also maintained the metastable structure of 1T-MoS nanosheets, acting to reduce the activation energy for Zn intercalation and enhance specific capacity. The obtained Mn-MoS/MXene contains more 1T-MoS and provides an improved specific capacity of 191.7 mAh g at 0.1 A g. Compared with Mn-MoS and pure MoS, it also exhibits enhanced cycling stability with a capacity retention of 80.3% after 500 cycles at 1 A g. Besides, the conductivity of Mn-MoS/MXene is significantly improved, which induces a lower activation energy of the zinc ions during intercalation/deintercalation.