Nature of Zinc‐Derived Dendrite and Its Suppression in Mildly Acidic Aqueous Zinc‐Ion Battery

Abstract

Aqueous zinc‐ion batteries (ZIBs) are attractive in energy storage due to the use of aqueous electrolytes that ensures safety and ease of handling all parts in air. However, catastrophic zinc dendritic growth on zinc metal anodes impedes their practical application. Herein, Zn3(PO4)3·4H2O (ZP)‐coated zinc metal anode is introduced to effectively suppress the dendrite growth and the chemical state of the dendrites that are composed of metallic Zn0, ZnO, and Zn(OH)2 is elucidated first. Significant improvement is observed for the ZP‐coated zinc metal symmetric cell. Operando synchrotron tomography demonstrates that the ZP‐coating layer ensures uniform deposition of zinc‐derived compounds by the ZP layer that scarifies itself through decomposition to P2O5, Zn0, and Zn(OH)2. Meanwhile, the local reaction between P2O5 and H2O reproduces H3PO4, which provides a condition to reproduce Zn3(PO4)2·4H2O via a reaction between H3PO4 and metallic Zn on the Zn metal anode. This cyclic reformation of Zn3(PO4)2·4H2O progressively prevents dendrites over the long‐term, even at high rates. The compatibility is verified in NaV3O8||ZP‐coated zinc anode cell over 1000 cycles. As a result, this finding presents a practical way for uniform deposition of Zn that can be applicable to aqueous and nonaqueous ZIBs.

Ionic Liquid “Water Pocket” for Stable and Environment‐Adaptable Aqueous Zinc Metal Batteries

“…X-ray diffraction (XRD) was performed on the Zn plates after a prolonged store time of 18 days (Figure S24, Supporting Information), it is revealed that xZnCO 3 •yZn(OH) 2 •zH 2 O, rather than the popularly observed Zn x OTf y (OH) 2x−y •nH 2 O (ZOTH), was formed for Zn soaked in 3 m Zn(OTf) 2 . [5,7,10,33] And, contrary to our expectations, in IL-AE the thin passivation layer is identified as ZOTH. This result does not undermine the general conclusion that ZOTH is detrimental to Zn reversibility, but provides a new thought about the role of ZOTH that, under certain conditions, a uniform ZOTH may contribute to the enhanced Zn stability against the electrolyte.…”

Synergistic Cooperation of Zn(002) Texture and Amorphous Zinc Phosphate for Dendrite-Free Zn Anodes

“…The chemical composition of the ZPO layer is verified by X-ray photoelectron spectra (XPS). In the Zn 2p spectrum (Figure i), the peak at 1022.1 eV originates from the Zn–O bond. , In the P 2p spectrum (Figure j), the peak at 133.4 eV comes from the P–O bond. , After Ar-ion sputtering, two peaks remain almost the same, excluding the simple adsorption of ZPO on Zn foils. In the XRD patterns (Figure S4a), the Zn(002) texture becomes more and more obvious when the annealing temperature increases from room temperature to 415 °C.…”

High reversibility at high current density: the zinc electrodeposition principle behind the “trick”

“…In addition to the Zn electrodeposition mechanism discussed earlier, high current density operations have a significant impact on suppressing the HER and subsequently on the generation of LDH species. [39][40][41][42] At higher current densities, a more uniform Zn electrodeposition layer is formed on current collectors, such as Cu, SS, and Ti substrates, which triggers the severe HER on the surface, as per the classic hydrogen evolution materials' volcano curve (Fig. 6b).…”