Electrochemical performances and Li+-storage mechanism of highly proportional 1T-MoS2/hierarchical porous activated carbon nanocomposites

The metallic phase of molybdenum disulfide (1T-MoS2) shows distinct advantages for lithium storage owing to its superior electronic conductivity, abundance of electroactive sites, and wider interplanar spacing compared to the semiconducting phase (2H-MoS2). However, investigating lithium storage in 1T-MoS2 encounters significant challenges attributed to its thermodynamic instability during synthesis and its transformation to an amorphous structure following the irreversible conversion reaction. This study addresses these challenges by utilizing hierarchical porous activated carbon (HPAC) to achieve the highest reported proportion (85 %) of 1T-MoS2 and by restricting the potential window to induce selective intercalation reaction. Impressively, 1T-MoS2/HPAC anodes exhibit a reversible capacity that surpasses the theoretical capacity (167 mAh/g) at various current densities from 0.1 to 2.0 A/g. This superior performance extends even after 100 cycles, retaining a capacity of 276 mAh/g at 0.1 A/g. The kinetic analysis indicates that the additional capacity originated from non-Faradic lithium storage, reaching 96 % at 5.0 mV/s. Further studies employing ex-situ XRD and in-situ EIS at various lithiation depths unveil the formation of a novel permanent phase after lithiation, characterized by expanded interlayer spacing and improved conductivity compared to the unlithiated material. These findings open promising avenues for developing anode materials for lithium-ion batteries/capacitors applications.