Pseudocapacitive Charge Storage in Thick Composite MoS2 Nanocrystal‐Based Electrodes. Issue 2 (7th October 2016) - Cook, John B.
Abstract : A synthesis methodology is demonstrated to produce MoS2 nanoparticles with an expanded atomic lamellar structure that are ideal for Faradaic‐based capacitive charge storage. While much of the work on MoS2 focuses on the high capacity conversion reaction, that process is prone to poor reversibility. The pseudocapacitive intercalation‐based charge storage reaction of MoS2 is investigated, which is extremely fast and highly reversible. A major challenge in the field of pseudocapacitive‐based energy storage is the development of thick electrodes from nanostructured materials that can sustain the fast inherent kinetics of the active nanocrystalline material. Here a composite electrode comprised of a poly(acrylic acid) binder, carbon fibers, and carbon black additives is utilized. These electrodes deliver a specific capacity of 90 mAh g −1 in less than 20 s and can be cycled 3000 times while retaining over 80% of the original capacity. Quantitative kinetic analysis indicates that over 80% of the charge storage in these MoS2 nanocrystals is pseudocapacitive. Asymmetric full cell devices utilizing a MoS2 nanocrystal‐based electrode and an activated carbon electrode achieve a maximum power density of 5.3 kW kg −1 (with 6 Wh kg −1 energy density) and a maximum energy density of 37 Wh kg −1 (with 74 W kg −1 power density). Abstract : MoS2 nanocrystals are synthesized by the thermal sulfurization of hydrothermally prepared MoO2 nanocrystals . Composite electrodes are formulated to show high levels of pseudocapacitive charge storage in traditional slurry‐based systems. These electrodes can be charged and discharged to 50% of their theoretical capacity in just 20 s and can be reversibly cycled 3000 times with greater than 80% capacity retention.