Zinc-ion batteries built on water-based electrolytes featuring compelling price-points, competitive performance, and enhanced safety represent advanced energy storage chemistry as a promising alternative to current lithium-ion battery systems. Attempts to develop rechargeable aqueous zinc-ion batteries (ZIBs) can be traced to as early as the 1980s; however, since 2015, the research activity in this field has surged throughout the world. Despite the achievements made in exploring electrode materials so far, significant challenges remain at the material level and even on the whole aqueous ZIBs system, leading to the failure of ZIBs to meet commercial requirements. This review aims to discuss how to pave the way for developing aqueous ZIBs. The current research efforts related to aqueous ZIBs electrode materials and electrolytes are summarized, including an analysis of the problems encountered in both cathode/anode materials and electrolyte optimization. Some concerns and feasible solutions for achieving practical aqueous ZIBs are discussed in detail. We would like to point out that merely improving the electrode materials is not enough; synergistic optimization strategies toward the whole battery system are also deeply needed. Finally, some perspectives are provided on the subsequent optimization design for further research efforts in the aqueous ZIB field.

Issues and opportunities facing aqueous zinc-ion batteries

Aqueous zinc ion batteries (ZIBs) are truly promising contenders for the future large-scale electrical energy storage applications due to their cost-effectiveness, environmental friendliness, intri...

Active Materials for Aqueous Zinc Ion Batteries: Synthesis, Crystal Structure, Morphology, and Electrochemistry

The zinc metal is recognized as one of the most promising anodes for Zn-based batteries in an energy-storage system. However, the deposition and transfer of bivalent Zn2+ into the host structure suffer from sluggish kinetics accompanying the side-reactions at the interface. Herein, we report a new class of Zn anodes modified by a three-dimensional (3D) nanoporous ZnO architecture coating on a Zn plate (designated as Zn@ZnO-3D) prepared by in situ Zn(OH)42− deposition onto the surface. This novel structure has been proven to accelerate the kinetics of Zn2+ transfer and deposition via the electrostatic attraction toward Zn2+ rather than the hydrated one in the electrical double layer. As a consequence, it achieves an average 99.55% Zn utilization and long-time stability for 1000 cycles. Meanwhile, the Zn@ZnO-3D/MnO2 cell shows no capacity fading after 500 cycles at 0.5 A g−1 with a specific capacity of 212.9 mA h g−1. We believe that the mechanistic insight into the kinetics and thermodynamic properties of the Zn metal and the understanding of structure–interface–function relationships are very useful for other metal anodes in aqueous systems.

Manipulating the ion-transfer kinetics and interface stability for high-performance zinc metal anodes

Aqueous zinc-ion batteries have rapidly developed recently as promising energy storage devices in large-scale energy storage systems owing to their low cost and high safety. Research on suppressing zinc dendrite growth has meanwhile attracted widespread attention to improve the lifespan and reversibility of batteries. Herein, design methods for dendrite-free zinc anodes and their internal mechanisms are reviewed from the perspective of optimizing the host-zinc interface and the zinc-electrolyte interface. Furthermore, a design strategy is proposed to homogenize zinc deposition by regulating the interfacial electric field and ion distribution during zinc nucleation and growth. This Minireview can offer potential directions for the rational design of dendrite-free zinc anodes employed in aqueous zinc-ion batteries.

Interfacial design of dendrite‐free zinc anodes for aqueous zinc‐ion batteries

Aqueous Zn batteries that provide a synergistic integration of absolute safety and high energy density have been considered as highly promising energy-storage systems for powering electronics. Despite the rapid progress made in developing high-performance cathodes and electrolytes, the underestimated but non-negligible dendrites of Zn anode have been observed to shorten battery lifespan. Herein, this dendrite issue in Zn anodes, with regard to fundamentals, protection strategies, characterization techniques, and theoretical simulations, is systematically discussed. An overall comparison between the Zn dendrite and its Li and Al counterparts, to highlight their differences in both origin and topology, is given. Subsequently, in-depth clarifications of the specific influence factors of Zn dendrites, including the accumulation effect and the cathode loading mass (a distinct factor for laboratory studies and practical applications) are presented. Recent advances in Zn dendrite protection are then comprehensively summarized and categorized to generate an overview of respective superiorities and limitations of various strategies. Accordingly, theoretical computations and advanced characterization approaches are introduced as mechanism guidelines and measurement criteria for dendrite suppression, respectively. The concluding section emphasizes future challenges in addressing the Zn dendrite issue and potential approaches to further promoting the lifespan of Zn batteries.

Dendrites in Zn-Based Batteries.

The development of low-cost and high-safety zinc-ion batteries (ZIBs) has been extensively discussed and reviewed in recent years, but the work on the comprehensive discussion and perspectives in developing zinc-ion electrolytes is still relatively lacking. Faced with critical challenges and bottlenecks practically, the viability of ZIBs critically depends on the development of suitable electrolytes and their practical considerations. In this review, a systematic summary with regard to the basic characteristics of zinc-ion electrolytes facing different issues from optimization strategies to the fundamental science of electrolyte/electrode interfaces (EEIs), particularly in the feasible modifications and advanced characterizations of EEIs, has been put forward. Due to the lack of consideration of the practical issues in major academic studies, we have particularly highlighted aspects that mainly focus on the choice of the electrolyte system, dosage of liquid and fluid electrolytes, status of gel and all-solid electrolytes, together with other concerns related to the electrolytes. The final section proposes significant perspectives to guide and promote the development of zinc-ion electrolytes.

Fundamentals and perspectives in developing zinc-ion battery electrolytes: a comprehensive review

Aqueous zinc-ion batteries are largely restricted by the unsatisfactory performance of zinc (Zn) anodes, including their poor stability and irreversibility. In particular, the mechanism behind the electrochemical contrast caused by the surface crystal plane, which is a decisive factor of the electrochemical characteristics of the hostless Zn anode, is still relatively indistinct. Hence, new insight into a novel anode with a surface-preferred (002) crystal plane is provided. The interfacial reaction and morphology evolution are revealed by theoretical analysis and post-mortem/operando experimental techniques, indicating that Zn anodes with more exposed (002) basal planes exhibit free dendrites, no by-products, and weak hydrogen evolution, in sharp contrast to the (100) plane. These features benefit the Zn (002) anode by enabling a long cyclic life of more than 500 h and a high average coulombic efficiency of 97.71% for symmetric batteries, along with delivering long cycling stability and reversibility with life spans of over 2000 cycles for full batteries. This work provides new insights into the design of high-performance Zn anodes for large-scale energy storage and can potentially be applied to other metal anodes suffering from instability and irreversibility.

Shan Guo

Papers

Manipulating the ion-transfer kinetics and interface stability for high-performance zinc metal anodes

Fundamentals and perspectives in developing zinc-ion battery electrolytes: a comprehensive review

Surface-Preferred Crystal Plane for a Stable and Reversible Zinc Anode

Fundamentals and perspectives of electrolyte additives for aqueous zinc-ion batteries

Oxygen Defects in β-MnO2 Enabling High-Performance Rechargeable Aqueous Zinc/Manganese Dioxide Battery