Screening Selection of Hydrogen Evolution-Inhibiting and Zincphilic Alloy Anode for Aqueous Zn Battery

The hydrogen evolution reaction (HER) and Zn dendrites growth are two entangled detrimental effects hindering the application of aqueous Zn batteries. The alloying strategy is studied to be a convenient avenue to stabilize Zn anodes, but there still lacks global understanding when selecting reliable alloy elements. Herein, it is proposed to evaluate the Zn alloying elements in a holistic way by considering their effects on HER, zincphilicity, price, and environmental-friendliness. Screening selection sequence is established through the theoretical evaluation of 17 common alloying elements according to their effects on hydrogen evolution and Zn nucleation thermodynamics. Two alloy electrodes with opposite predicted effects are prepared for experimental demonstration, i.e., HER-inhibiting Bi and HER-exacerbating Ni. Impressively, the optimum ZnBi alloy anode exhibits one order of magnitude lower hydrogen evolution rate than that of the pure Zn, leading to an ultra-long plating/stripping cycling life for more than 11 000 cycles at a high current density of 20 mA cm-2 and 81% capacity retention for 170 cycles in a Zn-V2O5 pouch cell. The study not only proposes a holistic alloy selection principle for Zn anode but also identifies a practically effective alloy element.

Suppressing metal corrosion through identification of optimal crystallographic plane for Zn batteries

Direct use of metals as battery anodes could significantly boost the energy density, but suffers from limited cycling. To make the batteries more sustainable, one strategy is mitigating the propensity for metals to form random morphology during plating through orientation regulation, e.g., hexagonal Zn platelets locked horizontally by epitaxial electrodeposition or vertically aligned through Zn/electrolyte interface modulation. Current strategies center around obtaining (002) faceted deposition due to its minimum surface energy. Here, benefiting from the capability of preparing a library of faceted monocrystalline Zn anodes and controlling the orientation of Zn platelet deposits, we challenge this conventional belief. We show that while monocrystalline (002) faceted Zn electrode with horizontal epitaxy indeed promises the highest critical current density, the (100) faceted electrode with vertically aligned deposits is the most important one in suppressing Zn metal corrosion and promising the best reversibility. Such uniqueness results from the lowest electrochemical surface area of (100) faceted electrode, which intrinsically builds upon the surface atom diffusion barrier and the orientation of the pallets. These new findings based on monocrystalline anodes advance the fundamental understanding of electrodeposition process for sustainable metal batteries and provide a paradigm to explore the processing-structure-property relationships of metal electrodes.

Two-Dimensional Organic-Inorganic Heterostructure as a Multifunctional Protective Layer for High Performance Zinc Metal Anode

Dendrite growth and side reactions of Zn metal anodes remain unresolved obstacles for practical application of aqueous Zn ion batteries. Herein, a two-dimensional (2D) organic-inorganic heterostructure with controlled thickness was constructed as a protective layer for a Zn metal anode. The reduction of uniformly distributed polyoxometalate in the layer causes a negative charge density gradient, which can accelerate zinc ion transfer, homogenize zinc deposition, and shield sulfates at the electrode interface, while the exposed hydrophobic alkyl chain of the layer can isolate the direct contact of water with the Zn anode. As a result of the synergetic effect, this 2D organic-inorganic heterostructure enables high Zn plating/stripping reversibility, with high average Coulombic efficiencies of 99.97% for 3700 cycles at 2 mA cm^-2. Under high Zn utilization conditions, a high areal-capacity full cell with hundreds of cycles was demonstrated.

Suppressing the Exacerbated Hydrogen Evolution of Porous Zn Anode with an Artificial Solid-Electrolyte Interphase Layer

Rechargeable Zn batteries are widely studied as aqueous, safe, and environmentally friendly alternatives to Li-ion batteries. The 3D porous Zn anode has been extensively reported for suppressing Zn dendrite growth and accelerating the electrode kinetics. However, we demonstrate herein that the undesirable hydrogen evolution reaction (HER) is also exacerbated for porous Zn electrode. Therefore, a polytetrafluoroethylene (PTFE) coating is further applied on the porous Zn serving as the artificial solid-electrolyte interphase (SEI), which is demonstrated to effectively inhibit the hydrogen evolution and maintain the Zn plating kinetics. By utilizing the synergistic effects of the porous morphology and artificial SEI layer, better performances are obtained over porous Zn or bare Zn foil, including dendrite-free Zn plating/stripping up to 2000 h at 2 mA cm^-2 and extended cycling in the Zn||V₂O₅ cell. This work suggests two complementary strategies for achieving simultaneously dendrite-free and side-reaction-suppressed Zn batteries.

Highly Reversible Zn Electrodeposition Enabled by an Artificial 3D Defect-Rich Conductive Scaffold

Rechargeable Zn metal batteries are attracting intensive attention due to the high capacity and safety of metallic Zn. However, their developments are strongly restricted by the poor reversibility and low areal capacity of anodes, especially at high rates. To achieve homogeneous and rapid Zn deposition is a way to solve these issues intrinsically. Here, we design a three-dimensional (3D) defect-rich conductive scaffold as an ideal substrate for Zn electrodeposition, which is built up of vertically aligned porous vanadium trioxide nanosheet skeleton supporting defective networks to provide fast electron- and ion-transfer paths. The abundant defects act as the energetically favorable nucleation sites inducing the in situ uniform growth of hierarchical Zn nanosheets on the substrate. The as-electrodeposited 3D Zn anodes achieve exceptionally reversible Zn plating/stripping over 5000 h at both moderate and high current densities (6 and 20 mA cm^-2). The 100 A h cm^-2 cumulative capacities at 80% depth of discharge are impressive and magnitude of orders greater than the reported Zn anodes so far. The unique 3D defective structure can be well maintained in thousands of cycles, which ensures a remarkably high Coulombic efficiency of 99.99956%. A full cell assembled with the ZnHCF cathode demonstrates a high-capacity retention of 91.2% at 2 A g^-1 after 20,000 cycles, over 10 times that of a Zn plate anode. This work provides an eligible anode for advanced rechargeable Zn metal batteries.

Resist-Dyed Textile Alkaline Zn Microbatteries with Significantly Suppressed Zn Dendrite Growth

The progress of electronic textiles relies on the development of sustainable power sources without much sacrifice of convenience and comfort of fabrics. Herein, we present a rechargeable textile alkaline Zn microbattery (micro-AZB) fabricated by a process analogous to traditional resist-dyeing techniques. Conductive patterned electrodes are realized first by resist-aided electroless/electrodeposition of Ni/Cu films. The resulting coplanar micro-AZB in a single textile, with an electroplated Zn anode and a Ni_0.7Co_0.3OOH cathode, achieves high energy density (256.2 Wh kg^-1), high power density (10.3 kW kg^-1), and stable cycling performances (82.7% for 1500 cycles). The solid-state micro-AZB also shows excellent mechanical reliability (bending, twisting, tailoring, etc.). The improved reversibility and cyclability of textile Zn electrodes over conventional Zn foils are found to be due to the significantly inhibited Zn dendrite growth and suppressed undesirable side reactions. This work provides a new approach for energy-storage textile with high rechargeability, high safety, and aesthetic design versatility.

Highly Reversible Zinc-Ion Intercalation into Chevrel Phase Mo6S8 Nanocubes and Applications for Advanced Zinc-Ion Batteries

This work describes the synthesis of Chevrel phase Mo6S8 nanocubes and its application as the anode material for rechargeable Zn-ion batteries. Mo6S8 can host Zn(2+) ions reversibly in both aqueous and nonaqueous electrolytes with specific capacities around 90 mAh/g, and exhibited remarkable intercalation kinetics and cyclic stability. In addition, we assembled full cells by integrating Mo6S8 anodes with zinc-polyiodide (I(-)/I3(-))-based catholytes, and demonstrated that such full cells were also able to deliver outstanding rate performance and cyclic stability. This first demonstration of a zinc-intercalating anode could inspire the design of advanced Zn-ion batteries.