MoS₂@Polyaniline for Aqueous Ammonium‐Ion Supercapacitors

Abstract

Ammonium‐ion aqueous supercapacitors are raising notable attention owing to their cost, safety, and environmental advantages, but the development of optimized electrode materials for ammonium‐ion storage still lacks behind expectations. To overcome current challenges, here, a sulfide‐based composite electrode based on MoS2 and polyaniline (MoS2@PANI) is proposed as an ammonium‐ion host. The optimized composite possesses specific capacitances above 450 F g−1 at 1 A g−1, and 86.3% capacitance retention after 5000 cycles in a three‐electrode configuration. PANI not only contributes to the electrochemical performance but also plays a key role in defining the final MoS2 architecture. Symmetric supercapacitors assembled with such electrodes display energy densities above 60 Wh kg−1 at a power density of 725 W kg−1. Compared with Li+ and K+ ions, the surface capacitive contribution in NH4+‐based devices is lower at every scan rate, which points to an effective generation/breaking of H‐bonds as the mechanism controlling the rate of NH4+ insertion/de‐insertion. This result is supported by density functional theory calculations, which also show that sulfur vacancies effectively enhance the NH4+ adsorption energy and improve the electrical conductivity of the whole composite. Overall, this work demonstrates the great potential of composite engineering in optimizing the performance of ammonium‐ion insertion electrodes.

Defect and interlayer spacing engineering of vanadium selenide for boosting sodium-ion storage

“…The interlayer spacing variation may be ascribed to the ammonium ions during the synthesis process, and this phenomenon is also demonstrated in other TMDCs. 30–32 Furthermore, the large radius of V 3+ (0.064 nm) than that of V 4+ (0.058 nm) also contributes to the expansion of interlayer spacing. To further clarify the variation of interlayer spacing, X-ray diffraction (XRD) and Raman measurements were performed on VSe 2− x /NC and pure VSe 2 .…”

Identifying the Role of the Cationic Geometric Configuration in Spinel Catalysts for Polysulfide Conversion in Sodium–Sulfur Batteries

“…To investigate the kinetics of conversion of long-chain polysulfides to short-chain sodium sulfide, electrochemical impedance spectroscopy (EIS) measurements were performed on CNF/Co 3 O 4 /S, CNF/CoFe 2 O 4 /S, and CNF/FeCo 2 O 4 /S electrodes at temperatures of 300, 315, and 330 K, respectively (Figures a, S33–S36, Tables S3, and S4). EIS data were fitted using the equivalent circuit presented in Figure a. ,− Within the model circuit, the CR element CPE Surf – R surf accounts for the deposition of adsorbed sodium polysulfide on the electrode surface and provides the first semicircle in the Nyquist plot of the EIS spectrum. The CR element CPE ct - R ct corresponds to the charge transfer process during polysulfide conversion and provides a second semicircle in the EIS spectrum.…”

A Layered Bi2Te3@PPy Cathode for Aqueous Zinc‐Ion Batteries: Mechanism and Application in Printed Flexible Batteries

“…The growing demand for renewable energy sources has created an urgent need for reliable and safe energy storage solutions. [ 1–6 ] Rechargeable aqueous zinc‐ion batteries (ZIBs) possess numerous advantages, including the high theoretical capacity of the zinc metal anode (5851 mAh mL −1 in volume and 820 mAh g −1 in mass), the abundance of zinc in the earth's crust (79 ppm), the small ionic radius of Zn 2+ (0.74 Å), the use of non‐toxic aqueous electrolyte, the possibility of fabrication in air, and excellent stability and reversibility. [ 7–12 ] These key traits make ZIBs highly promising as energy storage systems, especially for applications where cost and safety are major concerns, from large systems for the integration of renewables to small designs for wearable electronics.…”