Mesoporous MoS2 as a Transition Metal Dichalcogenide Exhibiting Pseudocapacitive Li and Na-Ion Charge Storage

The ion insertion properties of MoS2 continue to be of widespread interest for energy storage. While much of the current work on MoS2 has been focused on the high capacity four-electron reduction reaction, this process is prone to poor reversibility. Traditional ion intercalation reactions are highlighted and it is demonstrated that ordered mesoporous thin films of MoS2 can be utilized as a pseudocapacitive energy storage material with a specific capacity of 173 mAh g(-1) for Li-ions and 118 mAh g(-1) for Na-ions at 1 mV s(-1). Utilizing synchrotron grazing incidence X-ray diffraction techniques, fast electrochemical kinetics are correlated with the ordered porous structure and with an iso-oriented crystal structure. When Li-ions are utilized, the material can be charged and discharged in 20 seconds while still achieving a specific capacity of 140 mAh g(-1). Moreover, the nanoscale architecture of mesoporous MoS2 retains this level of lithium capacity for 10 000 cycles. A detailed electrochemical kinetic analysis indicates that energy storage for both ions in MoS2 is due to a pseudocapacitive mechanism.