No abstract

Aqueous zinc (Zn) batteries (AZBs) are widely considered as a promising candidate for next‐generation energy storage owing to their excellent safety features. However, the application of a Zn anode is hindered by severe dendrite formation and side reactions. Herein, an interfacial bridged organic–inorganic hybrid protection layer (Nafion‐Zn‐X) is developed by complexing inorganic Zn‐X zeolite nanoparticles with Nafion, which shifts ion transport from channel transport in Nafion to a hopping mechanism in the organic–inorganic interface. This unique organic–inorganic structure is found to effectively suppress dendrite growth and side reactions of the Zn anode. Consequently, the Zn@Nafion‐Zn‐X composite anode delivers high coulombic efficiency (ca. 97 %), deep Zn plating/stripping (10 mAh cm−2), and long cycle life (over 10 000 cycles). By tackling the intrinsic chemical/electrochemical issues, the proposed strategy provides a versatile remedy for the limited cycle life of the Zn anode.

The formation of dendrites on a zinc (Zn) metal anode has limited its practical applications on aqueous batteries. Herein, an artificial composite protective layer consisting of nanosized metal–organic frameworks (MOFs) to improve the poor wetting effect of aqueous electrolytes on the Zn anode is proposed to reconstruct the Zn/electrolyte interface. In this layer, hydrophilic MOF nanoparticles serve as interconnecting electrolyte reservoirs enabling nanolevel wetting effect as well as regulating an electrolyte flux on Zn anode. This zincophilic interface exhibits significantly reduced charge-transfer resistance. As a result, stable and dendrite-free Zn plating/stripping cycling performance is achieved for over 500 cycles. In addition, especially at higher C-rates, the coating layer significantly reduces the overpotentials in a Zn/MnO2 aqueous battery during cycling. The proposed principle and method in this work demonstrate an effective way to reconstruct a stable interface on metal anodes (e.g., Zn) where a conventional solid-electrolyte interface (SEI) cannot be formed.

Garnet‐type solid‐state electrolytes (SSEs) have been widely studied as a promising candidate for Li metal batteries. Despite the common belief that inorganic SSEs can prevent dendrite propagation, garnet SSEs suffer from relatively low critical current density (CCD) at which the SSEs are abruptly short‐circuited by Li dendrites. In this study, the short‐circuiting mechanism of garnet Li7La2.75Ca0.25Zr1.75Nb0.25O12 (LLCZN) is investigated. It is found that instead of propagating uniaxially from one electrode to other in a dendritic form, metallic lithium is formed within the SSE. This can be attributed to the fact that electrons combine with Li ions at the grain boundary, which exhibits relatively high electronic conductivity, and then reduce Li+ to Li0 to cause short circuits. In order to reduce the electronic conductivity at the grain boundary, a thin layer of LiAlO2 is coated on the grain surface of LLCZN, which results in an improved CCD value. It is also found that under higher external voltages, the electronic conductivity of SSE becomes more significant, which is believed to be the origin of CCD. These findings not only shed light on the short‐circuiting mechanism of garnet‐type SSEs but also offer a novel perspective and useful guidance on their designs and modifications.

Aqueous Zn‐MnO2 batteries using mild electrolyte show great potential in large‐scale energy storage (LSES) application, due to high safety and low cost. However, structure collapse of manganese oxides upon cycling caused by the conversion mechanism (e.g., from tunnel to layer structures for α‐, β‐, and γ‐phases) is one of the most urgent issues plaguing its practical applications. Herein, to avoid the phase conversion issue and enhance battery performance, a structurally robust novel phase of manganese oxide MnO2H0.16(H2O)0.27 (MON) nanosheet with thickness of ≈2.5 nm is designed and synthesized as a promising cathode material, in which a nanosheet structure combined with a novel H+/Zn2+ synergistic intercalation mechanism is demonstrated and evidenced. Accordingly, a high‐performance Zn/MON cell is achieved, showing a high energy density of ≈228.5 Wh kg−1, impressive cyclability with capacity retention of 96% at 0.5 C after 300 cycles, as well as exhibiting rate performance of 115.1 mAh g−1 at current rate of 10 C. To the best current knowledge, this H+/Zn2+ synergistic intercalation mechanism is first reported in an aqueous battery system, which opens a new opportunity for development of high‐performance aqueous Zn ion batteries for LSES.