Selective Preparation of 1T- and 2H-Phase MoS₂ Nanosheets with Abundant Monolayer Structure and Their Applications in Energy Storage Devices

The 1T-phase MoS2 has gained widespread attention because of its superhigh electronic conductivity. However, the comparatively complicated preparation and low-yielding production may hinder its potential applications in the energy storage field; hence, we developed a facile process to selectively prepare 1T- and 2H-phase MoS2 nanosheets with abundant monolayer structure with a large scale by controlling annealing temperature. With the further liquid phase exfoliation and freeze-drying procedure, the proposed nanosheets could maintain monolayer structure in the powder phase, and the existence of monolayers is believed to improve the electrochemical performance. The electrochemical performances of both the supercapacitor and lithium-ion batteries indicate that those prepared 1T-phase MoS2 nanosheets with abundant monolayer structure exhibit superior cycling stability. Specifically, the proposed 1T-phase MoS2 nanosheets could remain 170.4 F g–1 at 10 A g–1, and a capacity retention of 91% is achieved after 5000 cycles at 1 A g–1 in the symmetrical supercapacitor. It also delivers the excellent stability property of lithium ion insertion and extraction, which still maintain a charge capacity of 598 mAh g–1 after 1000 cycles at 1 A g–1 in the evaluation of lithium-ion batteries. The mechanism suggested that the high conductivity and unique electronic structure of 1T-phase MoS2 nanosheets may contribute to the enhancement of electrochemical properties.