High‐safety and low‐cost aqueous zinc‐ion batteries (ZIBs) are an exceptionally compelling technology for grid‐scale energy storage, whereas the corrosion, hydrogen evolution reaction and dendrites growth of Zn anodes plague their...

Strategies on regulating Zn2+ solvation structure for dendrites-free and side reactions-suppressed zinc-ion batteries

Reshaping the electrolyte structure and interface chemistry for stable aqueous zinc batteries

Aqueous zinc ion batteries employing metallic zinc anodes and aqueous electrolytes are highly attractive electrochemical energy storage devices owing to their cost effectiveness, intrinsic safety, elemental abundance and competitive gravimetric energy density. Compared with other cathode materials, vanadium-based compounds feature advantages such as higher capacity, higher power density and longer cycle life. Here, a comprehensive review is presented on recent advances of vanadium-based cathodes, focusing on the correlation between the structures and electrode performances as well as energy-storage mechanisms. The structure and electrochemical properties of vanadium-based cathode materials are discussed by categorizing Zn2+ diffusion channels including one-dimensional tunnels, two-dimensional planes, three-dimensional interpenetrating networks and zero-dimensional diffusion channels. Furthermore, the remaining issues of vanadium-based cathodes are highlighted and promising performance-enhancement strategies are overviewed from aspects such as lattice control, vacancy/defect engineering, and pre-intercalation of cations and/or molecules.

Vanadium-based cathodes for aqueous zinc-ion batteries: from crystal structures, diffusion channels to storage mechanisms

The hydrophobic internal cavity and hydrophilic external surface of cyclodextrins (CDs) render promising electrochemical applications. Here, we report a comparative and mechanistic study on the use of CD molecules (α-, β-, and γ-CD) as electrolyte additives for rechargeable Zn batteries. The addition of α-CD in aqueous ZnSO4 solution reduces nucleation overpotential and activation energy of Zn plating and suppresses H2 generation. Computational, spectroscopic, and electrochemical studies reveal that α-CD preferentially adsorbs in parallel on the Zn surface via secondary hydroxyl groups, suppressing water-induced side reactions of hydrogen evolution and hydroxide sulfate formation. Additionally, the hydrophilic exterior surface of α-CD with intense electron density simultaneously facilitates Zn2+ deposition and alleviates Zn dendrite formation. A formulated 3 M ZnSO4 + 10 mM α-CD electrolyte enables homogenous Zn plating/stripping (average Coulombic efficiency ∼ 99.90%) at 1 mA cm-2 in Zn|Cu cells and a considerable capacity retention of 84.20% after 800 cycles in Zn|V2O5 full batteries. This study provides insight into the use of supramolecular macrocycles to modulate and enhance the interface stability and kinetics of metallic anodes for aqueous battery chemistry.

Boosting the Kinetics and Stability of Zn Anodes in Aqueous Electrolytes with Supramolecular Cyclodextrin Additives.

Electrolyte/electrode interfacial electrochemical behaviors and optimization strategies in aqueous zinc-ion batteries

In-situ electrochemical conversion of vanadium dioxide for enhanced zinc-ion storage with large voltage range

Metallic zinc (Zn) is an attractive anode material to use for building an aqueous battery but suffers from dendritic growth and water-induced corrosion. Herein, we report the use of vanillin as a bifunctional additive in aqueous electrolyte to stabilize the Zn electrochemistry. Computational, spectroscopic, and electrochemical studies suggest that vanillin molecules preferentially absorb in parallel on the Zn surface to homogenize the Zn2+ plating and favorably coordinate with Zn2+ to weaken the solvation interaction between H2O and Zn2+, resulting in a compact, dendrite-free Zn deposition and a stable electrode-electrolyte interface with suppressed hydrogen evolution and hydroxide sulfate formation. In the formulated 2 M ZnSO4 electrolyte with 5 mM vanillin, the Zn anode sustains high areal capacity (10 mAh cm-2 at 1 mA cm-2) and remarkable cycling stability (1 mAh cm-2 for 1000 h) in a Zn|Zn cell and high average Coulombic efficiency (99.8%) in a Zn|Cu cell, significantly outperforming the cells without vanillin. Furthermore, the vanillin additive supports stable operation of full Zn|V2O5 batteries and is readily generalized to a Zn(CF3SO3)2-based electrolyte. This work offers a facile and cost-effective strategy of electrolyte design to enable high-performance aqueous Zn batteries.

Stabilizing Zinc Electrodes with a Vanillin Additive in Mild Aqueous Electrolytes.

Metallic lithium is one of the most promising anode materials to build next generation electrochemical power sources such as Li-air, Li-sulfur, and solid-state lithium batteries. The implementation of rechargeable Li-based batteries is plagued by issues including dendrites, pulverization, and an unstable solid electrolyte interface (SEI). Herein, we report the use of nanostructured CuO in situ grown on commercial copper foil (CuO@Cu) via chemical etching as a Li-reservoir substrate to stabilize SEI formation and Li stripping/plating. The lithiophilic interconnected CuO layer enhances electrolyte wettability. Besides, a mechanically stable Li2O- and LiF-rich SEI is generated on CuO@Cu during initial discharge, which permits dense and uniform lithium deposition upon subsequent cycling. Compared with bare Cu, the CuO@Cu electrode exhibits superior performance in terms of Coulombic efficiency, discharge/charge overpotentials, and cyclability. By pairing with the Li-CuO@Cu anodes, full cells with LiFePO4 and LiNi1/3Mn1/3Co1/3O2 cathodes sustain 300 cycles with 98.8% capacity retention at 1 C and deliver a specific capacity of 80 mAh g-1 at 10 C, respectively. This work would shed light on the design of advanced current collectors with SEI modulation to upgrade lithium anodes.

Kang Zhao

Papers

Vanadium-based cathodes for aqueous zinc-ion batteries: from crystal structures, diffusion channels to storage mechanisms

In-situ electrochemical conversion of vanadium dioxide for enhanced zinc-ion storage with large voltage range

Stabilizing Zinc Electrodes with a Vanillin Additive in Mild Aqueous Electrolytes.

Growing Nanostructured CuO on Copper Foil via Chemical Etching to Upgrade Metallic Lithium Anode.