An integrated flexible self-healing Zn-ion battery using dendrite-suppressible hydrogel electrolyte and free-standing electrodes for wearable electronics

Among many aqueous batteries, flexible zinc-ion (Zn-ion) battery becomes the focus owing to the merits of low cost, non-toxicity, and safety. Here, a Zn dendrite-suppressible hydrogel electrolyte with both flexible and self-healing properties is developed via photoinitiated polymerization. The cross-linked structure of the polyacrylamide-N,N'-methylenebisacrylamide (PAM-MBA)-Zn/Mn hydrogel endows an enlarged chemical stable window, high ionic conductivity, and low polarization potential. After cycling at the current density of 0.5 mA·cm⁻² for 250 h, Zn‖Zn symmetrical cell based on PAM-MBA-Zn/Mn electrolyte delivers a low polarization of 40 mV. The suppressed dendrite growth is ascribed to the uniform Zn deposition/stripping on anode. The galvanostatic intermittent titration technique curves display that the Zn-ion battery constructed by the PAM-MBA-Zn/Mn hydrogel electrolyte, free-standing FeVO₄/carbon cloth cathode, and Zn nanosheets/carbon cloth anode presents low reaction resistance and fast diffusion coefficient, indicating good endurance of cycling at high current densities. The battery with PAM-MBA-Zn/Mn hydrogel electrolyte presents a good flexible and self-healing performance. After bending 0°, 60°, 90°, and 180° for 30 times, batteries deliver stable capacities. Even cutting into ten pieces, the battery could self-heal and display a potential retention of 93.7% compared to the fresh cell. A good rate-performance is also achieved. After cutting/healing three times during cycling, capacity recovers well compared to the first-time cutting/healing. Moreover, the battery exhibits good flexibility using in an electric watch, indicating a promising potential for wearable electronics.