A salt-concentrated electrolyte for aqueous ammonium-ion hybrid batteries.

The development of aqueous ammonium-ion batteries (AAIBs) is currently attracting great attention because of the interesting electrochemical features induced by the charge carrier NH4+. One possible way to improve the performance of AAIBs is increasing the salt concentration in the electrolyte. Yet, few studies focus on the complex electrode-electrolyte interface behaviors in highly concentrated electrolytes, which affect the electrochemical performance of AAIBs significantly. Herein, we aim to understand the impact of CH3COONH4 electrolyte concentration on the NH4+ storage performance of a bimetallic hydroxide material. Experimental and theoretical simulation results indicate that the acetate anion will participate in the construction of the solvated NH4+ in a highly concentrated electrolyte, facilitating the adsorption of the solvated NH4+ cluster on the electrode surface. Besides, a new partial de-solvation model is also proposed, demonstrating an energy favorable de-solvation process. Finally, an ammonium-ion hybrid battery is designed, which provides a high average discharge voltage of 1.7 V and good energy density of 368 W h kg(cathode)-1, outperforming most of the state-of-the-art aqueous batteries. This work provides new understanding about the electrode's interfacial chemistry in different concentrated CH3COONH4 electrolytes, establishes a correlation between the electrolyte concentration and the electrode's performances, and demonstrates the superiority of the hybrid ammonium-ion battery design.

Vanadium Oxides with Amorphous-Crystalline Heterointerface Network for Aqueous Zinc-Ion Batteries.

Rechargeable aqueous Zn-VOx batteries are attracting attention in large scale energy storage applications. Yet, the sluggish Zn2+ diffusion kinetics and ambiguous structure-property relationship are always challenging to fulfil the great potential of the batteries. Here we electrodeposit vanadium oxide nanobelts (VO-E) with highly disordered structure. The electrode achieves high capacities (e.g., ≈5 mAh cm-2 , 516 mAh g-1 ), good rate and cycling performances. Detailed structure analysis indicates VO-E is composed of integrated amorphous-crystalline nanoscale domains, forming an efficient heterointerface network in the bulk electrode, which accounts for the good electrochemical properties. Theoretical calculations indicate that the amorphous-crystalline heterostructure exhibits the favorable cation adsorption and lower ion diffusion energy barriers compared to the amorphous and crystalline counterparts, thus accelerating charge carrier mobility and electrochemical activity of the electrode.

Electrodepositing amorphous molybdenum oxides for aqueous NH4+ storage.

The limited choice of anode materials always challenges the development of high performance aqueous ammonium-ion batteries (AAIBs). Herein, we fabricate amorphous molybdenum oxide (MoOx) materials and study the NH4+ storage performances. The results indicate that the optimized electrode exhibits high gravimetric/areal capacities of 175 mA h g-1/1.30 mA h cm-2, outperforming state-of-the-art anode materials for AAIBs. Our findings indicate that the valence state of Mo and the Mo-O-H content in MoOx synergistically control the NH4+ storage performances, offering new understanding for rational design of MoOx materials for energy storage applications.