Regulating Dendrite-Free Zn Deposition by a Self-Assembled OH- Terminated SiO2 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 SiO2 nano-sphere 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.