A self-regulated interface enabled by trivalent gadolinium ions toward highly reversible zinc metal anodes.

Aqueous zinc-ion batteries (AZIBs) have become an ideal candidate for large-scale energy storage systems owing to their inherent safety and highly competitive capacity. However, severe dendrite growth and side reactions on the surface of zinc metal anodes lead to quick performance deterioration, seriously impeding the commercialization of AZIBs. In this work, a self-regulated zinc metal/electrolyte interface is constructed to solve these problems by incorporating the trivalent Gd3+ additive with a lower effective reduction potential into the aqueous ZnSO4 electrolyte. It is revealed that the inert Gd3+ ions preferentially adsorb on the active sites of the zinc anode, and the induced electrostatic shielding layer is beneficial to uniform Zn deposition. Meanwhile, the adsorbed Gd3+ ions act as a buffer interface to lower the direct contact of the zinc anode with water molecules, thereby suppressing the interfacial parasitic reaction. These features endow the Zn//Zn battery using 0.2 M Gd3+ ions with 2940 h of cycling life at 5 mA cm-2 and a cumulative plating capacity (CPC) of 6.2 Ah cm-2 at 40 mA cm-2. When assembling with a MnO2 cathode, the full cell using the modified electrolyte exhibits a high capacity of 268.9 mAh/g at 0.2 A/g, as well as improved rate capability and cycle stability. The results suggest the great potential of a rare earth ion additive in reinforcing Zn metal anodes for developing practical AZIBs.

Nitrate Radical Induced "Two in One" Interface Engineering toward High Reversibility of Zn Metal Anode.

Advanced interfacial engineering performs a forceful modulation effect on Zn2+ plating/stripping with simultaneous inhibition of hydrogen evolution reaction, chemical corrosion, and dendrite growth, which is responsible for high reversibility of Zn anode. Herein, a "two in one" interface engineering is developed to improve the reversibility of Zn anode, in which multi-functional Zn5 (NO3 )2 (OH)8 ·2H2 O layer and preferential Zn (002) texture are constructed simultaneously. Due to nucleophilicity to Zn2+ arising from electronegativity, the layer can accelerate the desolvation process of [Zn (H2 O)6 ]2+ and transfer kinetics of Zn2+ ions, leading to uniform nucleation and effective inhibition of water-induced side reactions. Meanwhile, the latter is beneficial to guiding   Zn (002)-preferred orientation deposition with compact structure. Consequently, the Zn electrodes with such complementary interface modulation exhibit prominent reversibility. With an area capacity of 1 mAh cm-2 at 1 mA cm-2 , the symmetric cell operates steadily for 4000 h. Highly reversible Zn anode is maintained even at 50 mA cm-2 . For full cells coupled with MnO2 cathode, impressive rate capability and cycling stability with a high capacity beyond 100 mAh g-1 at 1 A g-1 after 2000 cycles are achieved. The results provide new insights into Zn anodes with high reversibility for next-generation aqueous zinc ion batteries.

Water-Processable and Multiscale-Designed Vanadium Oxide Cathodes with Predominant Zn2+ Intercalation Pseudocapacitance toward High Gravimetric/Areal/Volumetric Capacity.

Layered vanadium oxides have great potential as cathode materials for recently surged aqueous zinc-ion batteries (AZIBs). However, achieving high energy/power densities simultaneously is challenging, and side reactions related to more frequently than disclosed Zn2+ /proton co-insertion mechanism aggravate stability concerns. Herein, an engineered binder-free cathode configuration based on water-processable and high packing-density sheet-shaped composites of carbon nanotubes network, surface poly(3,4-ethylenedioxythiophene) (PEDOT) bridging coating, and ultrasmall PEDOT-intercalated V2 O5 nanoflakes is developed, and therein, large pseudocapacitance via predominant (≈91%) Zn2+ intercalation is revealed. Besides competitive gravimetric/areal capacity, the binder-free cathodes exhibit high volumetric capacity of 1106.1 mAh cm-3 and high-rate capability of 180.0 mA g-1 at 30 A g-1 as well as long-cycling stability. Such combined level of performance and unwanted reaction mechanism are attributed to the contained multiscale material/electrode design formula from crystal structure modification to 3D architecture construction of whole electrode, which endows the binder-free cathodes with abundant accessible sites for Zn2+ storage, but the least hydroxyl terminated surface for H+ insertion, as well as highly conductive network for electron transfer and fast Zn2+ diffusion kinetics throughout the electrode. Combined with scalable fabrication protocols, this study opens up great opportunities for high-performance vanadium oxide cathodes practically applicable to AZIBs.