High Areal Capacity and Long Cycle Life Flexible Mild Quasi‐Solid‐State Ag–Zn Battery with Dendrite‐Free Anode

Silver‐zinc (Ag–Zn) batteries are a promising battery system for flexible electronics owing to their high safety, high energy density, and stable output voltage. However, poor cycling performance, low areal capacity, and inferior flexibility limit the practical application of Ag–Zn batteries. Herein, we develop a flexible quasi‐solid‐state Ag–Zn battery system with superior performance by using mild electrolyte and binder‐free electrodes. Copper foam current collector is introduced to impede the growth of Zn dendrite, and the structure of Ag cathode is engineered by electrodeposition and chloridization process to improve the areal capacity. This novel battery demonstrates a remarkable cycle retention of 90% for 200 cycles at 3 mA cm −2 . More importantly, this binder‐free battery can afford a high capacity of 3.5 mAh cm −2 at 3 mA cm −2 , an outstanding power density of 2.42 mW cm −2 , and a maximum energy density of 3.4 mWh cm −2 . An energy management circuit is adopted to boost the output voltage of a single battery, which can power electronic ink display and Bluetooth temperature and humidity sensor. The developed battery can even operate under the extreme conditions, such as being bent and sealed in solid ice. This work offers a path for designing electrodes and electrolyte toward high‐performance flexible Ag–Zn batteries.