Polyethylene glycol intercalation for MoS₂ enables fast zinc-ion storage via pseudocapacitance

Molybdenum disulfide (MoS₂) has significant potential in aqueous zinc-ion batteries (AZIBs) due to its unique layered structure and adjustable layer spacing. However, the electrochemical performance remains unsatisfactory primarily due to the limited interlayer spacing. Here, a composite material consisting of MoS₂ nanosheets with expanded interlayer spacing and intercalated surfactant polyethylene glycol (PEG) is proposed as a cathode material for AZIBs. The results indicate that PEG is intercalated into the layered structure of MoS₂, resulting in a significant expansion of the MoS₂ layer spacing (from 0.62 to 0.95 nm). The PEG effectively mitigates the agglomeration during MoS₂ growth, promotes the 2H to 1T phase conversion in MoS₂ (about 60% of 1T phase content), provides more active sites for electrochemical reactions, reduces electron transfer resistance, and shortens diffusion distance of zinc ions. During the process of charging and discharging, the intercalated PEG molecules serve as “pillars” to provide structural support for MoS₂ layers, thereby enhancing their stability. The pseudocapacitive behavior of the MoS₂-PEG is promoted by the combination of these aforementioned advantages. Consequently, the MoS₂-PEG composite electrode exhibited a discharge capacity of 123.4 mAh·g⁻¹ at a current density of 1.0 A g⁻¹ and maintained a capacity retention of 83.5% after 200 cycles, while pure MoS₂ only displayed a reversible capacity of 71.5 mAh·g⁻¹ under identical conditions. This study provides a reference for the development of MoS₂ as a cathode material for AZIBs.