Pseudocapacitive Charge Storage in Thick Composite MoS 2 Nanocrystal-Based Electrodes

TLDR: In this article, the pseudocapacitive intercalation-based charge storage reaction of MoS2 is investigated, which is extremely fast and highly reversible, and a composite electrode comprised of a poly(acrylic acid) binder, carbon fibers, and carbon black additives is utilized.

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−1power density).