Progress in Anode Engineering for Rechargeable Zinc-Ion Batteries: Strategies for Dendrite suppression and Host Architectures

Abstract

Zinc-ion rechargeable batteries are becoming a promising source of energy-storage systems to be used in large-scale and stationary applications because of the natural safety inherent in its characteristics, low-price, environmental friendliness, and the fact that zinc metal is naturally available. Their commercial application is essentially constrained by the fact that the electrochemical reversibility and structural integrity of zinc metal anodes is poor when constant plating and stripping are considered. Zinc anodes in aqueous electrolytes have dendritic growth, parasitic hydrogen evolution, spontaneous corrosion, passivation of surfaces and dead zinc, an electrochemically inactive electrochemical by-product, which leads to high rates of capacity degradation, poor coulombic efficiency, and early battery demise. These degradation mechanisms are caused by non-uniform zinc nucleation, anisotropic crystal growth, heterogeneous electric-field and current-density distributions, solvation-desolation dynamics, and unstable zinc-electrolyte interfacial chemistry are triggered by complex and interrelated electrochemical and physicochemical processes. In this review, the current achievements in the study of the basic mechanisms that govern the behavior of zinc anodes in aqueous conditions are critically summarized, with the main focus on the nature of morphological instability and formation of dendrites. The effects of electrolyte composition, water activity, interfacial energy barriers and crystallographic texture in controlling zinc deposition and dissolution are studied.It is on these mechanistic understandings that the recent approaches of stabilizing zinc anodes are thoroughly surveyed, such as electrolyte and solvation-structure engineering, functional electrolyte additives, artificial solid-electrolyte interphase construction, and surface chemistry modulation to regulate zinc nucleation and counteract side reactions. Also, host-structure engineering methods based on porous carbon, metallic scaffolds, three-dimensional conductive scaffolds, and zincophilic composite structures are addressed in the context of ion-flux homogenization, spatial confinement and strain accommodation. The innovations made by methods of operando characterization and theoretical modeling are also mentioned, and the issue of the challenges that still exist concerning the long-term cycling stability, high areal capacity operation, lean electrolyte conditions, and scalability are outlined, which allowed a consistent mechanistic picture of the rational design of dendrite-free and highly reversible zinc metal anodes to the next generation of zinc-ion batteries.