l -Cysteine Intercalation Inducing 1T-Rich MoS 2 Hybrids as High-Performance Cathodes for Reversible Zinc-Ion Storage

Due to the high energy density, inherent safety, and cost-effectiveness, aqueous zinc-ion batteries (AZIBs) have been recognized as promising solution for energy storage. Compared to the 2H phase of MoS 2, the metallic 1T phase counterpart holds greater potential for application in AZIBs, owing to its higher electrical conductivity and favorable two-dimensional channel structure. Herein, a facile one-step hydrothermal approach was employed to synthesize stable and 1T-rich MoS 2 hybrids (MoS 2 - l -Cys) using l -cysteine as an intercalation modifier. This approach simultaneously induces a spontaneous phase transition from the semiconducting 2H to metallic 1T phase and expands the interlayer spacing of MoS 2 . The metallic 1T phase of MoS 2 promotes electrons transfer, while the expanded interlayer spacing accelerates the Zn 2+ ions’ diffusion kinetics and exposes more active sites. These synergistic effects collectively boost charge transfer kinetics of the Zn 2+ ions’ redox reaction, thereby dramatically improving the electrochemical performance of AZIBs. Therefore, the discharge specific capacity of the MoS 2 - l -Cys electrode is as high as 279.0 mAh g –1 with outstanding rate capability. Furthermore, the MoS 2 - l -Cys electrode exhibits exceptional cycling stability, with a capacity retention of 91.4% after 1000 cycles at 4 A g –1, due to that the expanded interlayer spacing can effectively mitigate volume variations of MoS 2 - l -Cys during cycling. This work systematically elucidates the crucial role of l -cysteine intercalation-induced phase transition in optimizing reaction kinetics, providing a viable and effective strategy for developing MoS 2 -based cathodes for high-performance AZIBs.