Achieving stable zinc metal anodes by regulating ion transfer and desolvation behavior

Promoting Migration Kinetic of Desolvated Zn2+ by Functional Interlayer Toward Superior Zn Metal Anode

The development of Zn metal anodes is challenged by non-uniformity of ion flux causing inhomogeneous deposition and strong solvation of Zn(H2O)6 2+ resulting in adverse side reactions. Applying intermediate protecting layers with high affinity to Zn2+ is a popular and effective solution, but it also limits the ion migration. A functional MXene-based interlayer is designed in this work to modify the glass fiber separator achieving balanced adsorption energy and ion migration. By coating porous silica on the MXene surface, the instinct advanatges of MXene are mostly reserved while the adsorption energy to Zn2+ is optimized. Such an interlayer enables high flux and uniformity of desolvated Zn2+, contributing to rapid deposition kinetic for excellent rate performance and inhibited side reactions for long-term cycling stability. As a result, the functionalized Zn metal anode delivers steady plating/stripping cycles for more than 5000 h at 0.1 mA cm-2 and 700 h at 5.0 mA cm-2. The Zn||MnO2 full cells with this separator also exhibit superior rate capabilities (173 mAh g-1 at 2.0 A g-1) and excellent cycle performance (254.7 mAh g-1 after 1000 cycles at 0.5 A g-1). This work provides a feasible strategy for preparing functional interlayers toward superior Zn or other metal anodes.

Dendrite-free zinc metal anode for long-life zinc-ion batteries enabled by an artificial hydrophobic-zincophilic coating

Considering the desired energy density, safety and cost-effectiveness, rechargeable zinc-ion batteries (ZIBs) are regarded as one of the most promising energy storage units in next-generation energy systems. Nonetheless, the service life of the current ZIBs is significantly limited by rampant dendrite growth and severe parasitic reactions occurring on the anode side. To overcome these issues caused by poor interfacial ionic conduction and water erosion, we have developed a facile strategy to fabricate a uniform zinc borate layer at the zinc anode/electrolyte interface (ZnBO). Such protective layer integrates superhydrophobic-zincopholic properties, which can effectively eliminate the direct contact of water molecules on the anode, and homogenize the interfacial ionic transfer, thereby enhancing the cyclic stability of the zinc plating/stripping. As a result, the as-prepared ZnBO-coated anode exhibits extended lifespan of 1200 h at 1 mA cm-2 and demonstrates remarkable durability of 570 h at 20 mA cm-2 in Zn||Zn symmetric cells. Additionally, when coupled to an NH4V4O10 (NVO) cathode, it also delivers a superior cyclability (203.5 mAh/g after 2000 cycles at 5 A/g, 89.3 % capacity retention) in coin full cells and a feasible capacity of 2.5 mAh at 1 A/g after 200 cycles in pouch full cells. This work offers a unique perspective on integrating hydrophobicity and zincophilicity at the anode/electrolyte interface through an artificial layer, thereby enhancing the cycle lifespan of ZIBs.

Superabsorbent starch protective layer modulates zinc anode interface for long-life aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have attracted much attention for their safety, low cost and high theoretical capacity. Nevertheless, Zn dendrites and the adverse reactions such as corrosion, hydrogen evolution and passivation on the anode affect the cycle life and stability of AZIBs. Herein, superabsorbent starch (SS) was employed on Zn foil to form an artificial interface protection layer, which inhibited the formation of dendrites by guiding the uniform deposition of Zn2+. SS with a large amount of oxygen-containing functional group is superabsorbent, which can attract the active water around the hydrated Zn2+, promoting the desolvation process of the hydrated Zn2+ and significantly inhibiting the occurrence of hydrogen evolution reaction. In addition, the inherent pore structure of the SS artificial interfacial layer can induce uniform nucleation of Zn2+ and inhibit the dendrites growth. Moreover, compared to bare Zn//MnO2 cell (44.1 %), the capacity retention of Zn@SS//MnO2 cell remained as high as 87.8 % after 1000 cycles at 1.5 A g-1. The simple method provided a new method for the rapid development of AZIBs.

Boosting the reversibility of Zn anodes via synergistic cation-anion interface adsorption with addition of multifunctional potassium polyacrylate

Rechargeable aqueous Zn batteries have the edge in resource reserve, cost, energy and conversion efficiency due to the inherent features of metal Zn anodes. However, the application of Zn-based batteries is being seriously hindered by Zn dendrites and water-induced side-reactions. Here, potassium polyacrylate (K-PAM) is proposed as the electrolyte additive to form a synergistic cation-anion interface on Zn surface. The carboxyl anions and K+ cations are preferentially adsorbed on the Zn surface due to the intrinsic surfactant characteristics, which could homogenize Zn plating and suppress parasitic reactions. The synergistic regulation of K-PAM additive endows the ZnZn symmetric cells with excellent cyclic durability of 1250 h at 1 mA cm-2, which is significantly better than the polyacrylic acid additive only with carboxyl anions. Moreover, trace K-PAM addition into traditional ZnSO4 electrolyte endows the ZnCu batteries with a considerable average Coulombic efficiency of 99.2 %. Additionally, higher capacity retention and excellent cycling stability of ZnVO2 cells further mark K-PAM as a potentially impressive aqueous electrolyte additive for high-performance Zn-based batteries. This work will provide a promising method for the synergistic regulation with cations and anions of electrolyte additives to improve the stability and reversibility of Zn anodes.