A Dendrite-Free Zinc Bromine Hybrid Supercapacitor with High Power and Energy Density

Metallic zinc is a highly promising candidate for an anode material in hybrid supercapacitors because of its exceptional characteristics. However, zinc anodes are prone to rapid performance deterioration due to the extensive growth of Zn dendrites and the occurrence of unfavorable side reactions. Herein, ammonium acetate (NH 4 OAc) was introduced as a dual-functional additive to address these problems in a zinc bromine hybrid supercapacitor; thanks to the “shielding effect” and “pH buffer effect”, the Zn anode displayed a high Coulombic efficiency (CE) of 99.2%, and the Zn//Zn symmetric cell cycled a long time over 380 h at 0.5 mA cm –2 . The assembled Zn//Br supercapacitor achieves a high energy density of 62.9 Wh kg –1 even under a high power density of 27,600 W kg –1; furthermore, it demonstrates an exceptional stability over 25,000 cycles.