Regulating Dendrite-Free Zn Deposition by a Self-Assembled OH-Terminated SiO₂ Nanosphere Layer toward a Zn Metal Anode

Abstract

Zn dendrite growth during repeated plating and stripping of a Zn metal anode often causes short-circuiting by puncturing the separator. Herein, we propose a separator modification strategy to regulate the Zn-ion flux and achieve uniform Zn deposition through the OH-terminated SiO₂ nanosphere coating. The interspaces between the uniform SiO₂ nanospheres construct a network of Zn-ion transport channels, and the negatively charged hydroxyl groups on the surface of SiO₂ nanospheres can electrostatically attract the Zn ions to direct the ion migration. The negative charges on SiO₂ nanospheres are retained at a higher pH, which enables the SiO₂ coating to consistently regulate the Zn-ion flux in the operating pH range of the Zn stripping/plating process. With a uniform Zn deposition guided by the SiO₂ coating, the dendrite formation is suppressed and the side reactions are alleviated. As a result, the Zn||Zn symmetric cell achieves a cyclic life of 1000 h at both 3 and 5 mA cm^-2. Meanwhile, the Zn||Cu asymmetric cell is able to maintain a Coulombic efficiency of 99.62% at 1 mA cm^-2 for 2000 cycles, which outperforms many previously reported strategies.