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Aqueous rechargeable sodium‐ion batteries have attracted increasing attention for large‐scale energy storage applications due to their intrinsic safety and sufficient sodium reserves. The tunnel‐type Na0.44MnO2 has been widely investigated as a promising cathode because of its low cost and high theoretical capacity (120 mAh g−1). However, a capacity higher than 45 mAh g−1 for Na0.44MnO2 in aqueous electrolyte is difficult to obtain. Here, it is found that there is a competitive insertion reaction between H+ and Na+, and the diffusion energy barriers of Na+ are increased along with high Na content in Na0.44MnO2, but the opposite is true for protons. By decreasing the diffusion energy barrier of Na+ and increasing the diffusion energy barrier of protons, a high reversible capacity of 101 mAh g−1 for Na0.44MnO2 in aqueous electrolytes is achieved for the first time. Coupled with a quinone anode, the full cell delivers a high energy density of 60 Wh kg−1 and retains 85% of its capacity for 1200 cycles at a 1 C rate. [ABSTRACT FROM AUTHOR]

Aqueous sodium–zinc hybrid ion batteries are attracting extensive attention due to high energy density, low cost, and environmental friendliness. Unfortunately, there are still some drawbacks associated with the low voltage and cycle performance degradation that limit their practical application. Here, a concentrated aqueous electrolyte with solvation‐modulated Zn2+ is reported that reduces the hydrogen evolution reaction on the surface of Zn metal, avoiding the generation of ZnO and uneven deposition. Accordingly, the Zn anode exhibits 1600 h Zn plating/stripping and ≈99.96% Coulombic efficiency after 700 cycles. In addition, solvation‐modulated Na+ promotes the excellent structural stability of zinc hexacyanoferrate (ZnHCF) due to the rhombohedral–rhombohedral rather than rhombohedral–cubic phase transition. A ZnHCF//Zn full cell delivers an average voltage of 1.76 V and 98% capacity retention after 2000 cycles at 5 C rates. [ABSTRACT FROM AUTHOR]

A fast ion conductor, NaTi2(PO4)3 (NTP), is hydrothermally synthesized as a solid‐state electrolyte protection layer on the surface of Zn anodes (NTP@Zn). NTP has fast ionic conductivity compared with other insoluble phosphates, such as TiP2O7 (TPO) and Zn3(PO4)2 (ZPO), which is demonstrated by the density‐functional theory calculation and cyclic voltammetry tests. X‐ray photoelectron spectrometer, X‐ray powder diffraction, and HRTEM analyses show that the internal transport/mobility of Zn2+ can be achieved in NTP layer as an "ion passable fence." The NTP layer with a thickness of 20–25 µm not only prevents side reactions and zinc dendrites, but also improves the reversibility of Zn deposition and electrochemical performance. The NTP@Zn/MnO2 battery represents the best long‐life performance among Zn/MnO2 batteries to date, which successfully retains a considerable capacity of 105 mA h g−1 with a CE nearly 100% after 10 000 charge/discharge cycles at 10 C (≈1.5 A g−1). Each cycle capacity attenuation rate is only 0.004%. This work represents an advanced step toward long‐life Zn metal anodes for aqueous zinc‐ion batteries. [ABSTRACT FROM AUTHOR]

Aqueous lithium/sodium‐ion batteries (AIBs) have received increasing attention because of their intrinsic safety. However, the narrow electrochemical stability window (1.23 V) of the aqueous electrolyte significantly hinders the development of AIBs, especially the choice of electrode materials. Here, an aqueous electrolyte composed of LiClO4, urea, and H2O, which allows the electrochemical stability window to be expanded to 3.0 V, is developed. Novel [Li (H2O)x(organic)y]+ primary solvation sheath structures are developed in this aqueous electrolyte, which contribute to the formation of solid–electrolyte interface layers on the surfaces of both the cathode and anode. The expanded electrochemical stability window enables the construction of full aqueous Li‐ion batteries with LiMn2O4 cathodes and Mo6S8 anodes, demonstrating an operating voltage of 2.1 V and stability over 2000 cycles. Furthermore, a symmetric aqueous Na‐ion battery using Na3V2(PO4)3 as both the cathode and anode exhibits operating voltage of 1.7 V and stability over 1000 cycles at a rate of 5 C. [ABSTRACT FROM AUTHOR]