Regulating Dendrite-Free Zn Deposition by a Self-Assembled OH-Terminated SiO 2 Nanosphere Layer toward a Zn Metal Anode.

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 SiO 2 nanosphere coating. The interspaces between the uniform SiO 2 nanospheres construct a network of Zn-ion transport channels, and the negatively charged hydroxyl groups on the surface of SiO 2 nanospheres can electrostatically attract the Zn ions to direct the ion migration. The negative charges on SiO 2 nanospheres are retained at a higher pH, which enables the SiO 2 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 SiO 2 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.