posted on 2022-12-21, 20:05authored byJohn B. Cook, Jesse S. Ko, Terri C. Lin, Daniel D. Robertson, Hyung-Seok Kim, Yan Yan, Yiyi Yao, Bruce S. Dunn, Sarah H. Tolbert
Sodium-ion intercalation pseudocapacitance promises fast
energy
storage that is cheaper than lithium-ion-based systems. MoS2 is an attractive sodium-ion host due to its large van der Waals
gaps, high Na+ mobility, and high electronic conductivity
in the 1T phase. In this paper, we have quantified high levels (>90%)
of pseudocapacitive charge storage in 30 μm thick MoS2 nanocrystal-based composite electrodes, which can be charged to
almost 50% of their 1C capacity in just under 40 s. In addition, very
little decay is observed in the delivered capacity (retention of 97%)
after 1800 cycles at a rate of 20C. Synchrotron-based operando X-ray diffraction shows that the pseudocapacitive performance is
enabled through suppression of the trigonal 1T-MoS2 to
triclinic NaxMoS2 phase transition
in MoS2 nanocrystals during charge–discharge.