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.