Unraveling the "Gap-Filling" Mechanism of Multiple Charge Carriers in Aqueous Zn-MoS2 Batteries.

The utilization rate of active sites in cathode materials for Zn-based batteries is a key factor determining the reversible capacities. However, a long-neglected issue of the strong electrostatic repulsions among divalent Zn2+ in hosts inevitably causes the squander of some active sites (i.e., gap sites). Herein, we address this conundrum by unraveling the "gap-filling" mechanism of multiple charge carriers in aqueous Zn-MoS2 batteries. The tailored MoS2 /(reduced graphene quantum dots) hybrid features an ultra-large interlayer spacing (2.34 nm), superior electrical conductivity/hydrophilicity, and robust layered structure, demonstrating highly reversible NH4 + /Zn2+ /H+ co-insertion/extraction chemistry in the 1 M ZnSO4 +0.5 M (NH4 )2 SO4 aqueous electrolyte. The NH4 + and H+ ions can act as gap fillers to fully utilize the active sites and screen electrostatic interactions to accelerate the Zn2+ diffusion. Thus, unprecedentedly high rate capability (439.5 and 104.3 mAh g-1 at 0.1 and 30 A g-1 , respectively) and ultra-long cycling life (8000 cycles) are achieved.

Acceleration or retardation by a magnetic field of the anodic processes of iron in molybdate-bearing chloride solutions.

The modulation by a horizontal magnetic field of the anodic processes of iron in molybdate-bearing chloride solutions is determined. The magnetic field can accelerate or retard the anodic reaction depending on the rate-controlling steps at specified electrode potentials. The anodic current density arising from uniform dissolution from open or semi-open pits is increased by the magnetic field. The current density originating from occluded pits can be decreased by the magnetic field, where autocatalysis has a dominant effect on the pitting rate. The effect of the magnetic field on the pitting corrosion is a combination of the influence on electrochemical reactions at the interfaces of the pits and the disturbance of the autocatalysis process inside the pit enclave through the magnetohydrodynamic (MHD) effect. Micro-MHD effects for specific locations and macro-MHD effects for pitting systems are recommended to illustrate the magnetic effect on localized corrosion phenomena at various combinations of potentials and solution compositions.