Swollen Ammoniated MoS₂ with 1T/2H Hybrid Phases for High-Rate Electrochemical Energy Storage

Abstract

Because of its lamellar structure similar to that of graphite, molybdenum disulfide has been widely explored as a lithium-ion battery and supercapacitor electrode material, but its energy storage ability is strongly hindered by the poor electrical/ionic conductivity and transfer among the intrinsic lamellar structures. Herein we propose a novel swollen ammoniated MoS2 with 1T/2H hybrid phases (MoS2-A), which possesses a high concentration of 1T phase and unique expanded lamellar structures, as a supercapacitor electrode material. The obtained MoS2-A reveals superior charge-storage performance with distinct pseudocapacitive behavior, including surface redox reaction and diffusive intercalation, and even when the scan speed is increased 100-fold from 1 to 100 mV s–1, the retention ratio of the specific capacitance can still reach 58.5%, demonstrating a superhigh rate capability. Moreover, this supercapacitor electrode also exhibits good cycling stability with a retention ratio of 95.4% after 2000 cycles. The outstanding electrochemical performance of MoS2-A should be ascribed to the existence of the metallic 1T phase, which favors high electrical conductivity, and the swollen lamellar structures possessing an enlarged interlayer space of 0.99 nm created by in situ intercalated species, facilitating the fast and reversible diffusive intercalation of electrolyte ions.