Mechanistic Study of Interfacial Modification for Stable Zn Anode Based on a Thin Separator.

The interface plays a pivotal role in stabilizing metal anode. Extensive studies have been made but systematic research is lacking. In this study, preliminary studies are conducted to explore the prime conditions of interfacial modification to approach the practical requirements. Critical factors including reaction kinetics, transport rate, and modulus are identified to affect the Zn anode morphology significantly. The fundamental principle to enhance the Zn anode stability is systematically studied using the TEMPO-oxidized cellulose nanofiber (TOCNF) coating layer with thin a separator. Its advantageous mechanical properties buffer the huge volume variation. The existence of hydrophilic TOCNF in the Zn anode interface enhances the mass transfer process and alters the Zn2+ distribution with a record high double-layer capacitance (390 uF cm-2 ). With the synergetic effect, the modified Zn anode works stably under 5 mA cm-2 with a thin nonwoven paper as the separator (thickness 113 µm). At an ultra-high current density of 10 mA cm-2 , this coated anode cycles for more than 300 h. This strategy shows an immense potential to drive the Zn anode forward toward practical applications.

Dendrite Issues for Zinc Anodes in a Flexible Cell Configuration for Zinc-Based Wearable Energy-Storage Devices.

A key application of aqueous rechargeable Zn-based batteries (RZBs) is flexible and wearable energy storage devices (FESDs). Current studies and optimizations of Zn anodes have not considered the special flexible working modes needed. In this study, we present the Zn accumulation on the folded line and curve areas of flexible anodes. The correlation between the bending radius and the lifespan of symmetric cells is proposed. The interface contact of hydrogel electrolytes when working in a bending mode is another key factor affecting cell lifespan. After detailed analysis, the ideal cell configuration is shown to be hydrogel electrolytes with suitable chemistry, satisfactory mechanical properties, and high adhesivity. Thus a water in salt (WIS) hydrogel is proposed that demonstrates a highly stable cell performance. This work provides a new perspective in Zn anode research for the development of FESDs.

Hydrogen-Substituted Graphdiyne Ion Tunnels Directing Concentration Redistribution for Commercial-Grade Dendrite-Free Zinc Anodes.

Current aqueous Zn batteries (ZBs) seriously suffer from dendrite issues caused by rough electrode surfaces. Despite significant efforts in prolonging lifespan of these batteries, little effort has been devoted to dendrite elimination in commercial-grade cathode loading mass. Instead, demonstrations have only been done at the laboratory level (≤2 mg cm-2 ). Additionally, new dilemmas regarding change of the proton-storage behavior and interface pulverization have emerged in turn. Herein, hydrogen-substituted graphdiyne (HsGDY), with sub-ångström level ion tunnels and robust chemical stability, is designed as an artificial interface layer to address these issues. This strategy prolongs the symmetric cell lifespan to >2400 h (100 days), which is 37 times larger than without protection (63 h). The simulation of dual fields reveals that HsGDY can redistribute the Zn2+ concentration field by spatially forcing Zn2+ to deviate from the irregular electric field. During practical use, the as-assembled full batteries deliver a long lifespan 50 000 cycles and remain stable even at a commercial-grade cathode loading mass of up to 22.95 mg cm-2 . This HsGDY-protection methodology represents great progress in Zn dendrite protection and demonstrates enormous potential in metal batteries.

Do Zinc Dendrites Exist in Neutral Zinc Batteries: A Developed Electrohealing Strategy to In Situ Rescue In-Service Batteries.

The dendritic issue in aqueous zinc-ion batteries (ZBs) using neutral/mild electrolytes has remained an intensive controversy for a long time: some researchers assert that dendrites severely exist while others claim great cycling stability without any protection. This issue is clarified by investigating charge/discharge-condition-dependent formation of Zn dendrites. Lifespan degradation (120 to 1.2 h) and voltage hysteresis deterioration (134 to 380 mV) are observed with increased current densities due to the formation of Zn dendrites (edge size: 0.69-4.37 µm). In addition, the capacity is also found to remarkably affect the appearance of the dendrites as well. Therefore, at small current densities or loading mass, Zn dendrites might not be an issue, while the large conditions may rapidly ruin batteries. Based on this discovery, a first-in-class electrohealing methodology is developed to eliminate already-formed dendrites, generating extremely prolonged lifespans by 410% at 7.5 mA cm-2 and 516% at 10 mA cm-2 . Morphological analysis reveals that vertically aligned Zn dendrites with sharp tips gradually become passivated and finally generate a smooth surface. This developed electrohealing strategy may promote research on metal dendrites in various batteries evolving from passive prevention to active elimination, rescuing in-service batteries in situ to achieve elongated lifetime.