Design of Self-Aggregating and Recyclable Quasi-Solid-State Electrolyte towards Dendrite-Free Zn Anode

Abstract

Zn-based electrochemistries have received ever-increasing attention given their non-toxicity, easy recycling, biocompatibility, and abundant natural resources, which can solve the fundamental challenges of Li-based batteries and make promises in the application of grid-scale energy storage in the future. In particular, Zn-ion batteries coupled with quasi-solid-state electrolytes such as hydrogel electrolytes rather than conventional liquid electrolytes can bring less dendrite formation, thermal runaways, and electrolyte volatilization along with higher energy density. Herein, my current research work reports a gelatin-based hydrogel electrolyte using commercially available Jell-O powder, which is able to regulate the cycling behavior of Zn anodes by inhibiting the growth of Zn dendrite formation. Numerous characterizations and electrochemical techniques prove that gelatin chains can twin into helical structure and self-assemble to form a 3D triple matrix during sol-gel transition, which promotes better electrochemical performance than single molecules. In the meantime, the Jell-O QSSE can promote the binding of anions in the Zn2+ solvation sheath while reducing the content of free anions, thereby decreasing their contribution to the current density and inhibiting the formation of Zn dendrites. The as-assembled Zn//Zn symmetric cells using Jell-O QSSE can sustain long-term cycling of 2000 h, 1500 h, 250 h, and 120 h at 1, 10, 20, and 50 mA cm-2 with an areal capacity of 1 mAh cm-2, respectively. Moreover, Zn//Cu coin cells show excellent reversibility with a high average CE of 98.61% for more than 100 stable cycles. To validate the practicality of Jell-O QSSE, Zn//MnO2 full cells are assembled, showing an ultrahigh capacity retention of 88.7% after 1000 cycles with a high average CE of 99.64%. Different cathode materials such as sodium vanadate (β-Na0.33V2O5, NVO) was applied as well, which similarly show excellent cycling stability and capacity retention, indicating good compatibility of Jell-O QSSE to various cathode materials. Finally, the recycling of used Jell-O QSSE was demonstrated via a suction filtration method. The filtered Jell-O QSSE was applied again in the assembly of Zn//Zn symmetric cells, showing an excellent cycling stability of more than 1200 h, making Jell-O QSSE much more promising than conventional ZnSO4 electrolyte in the application of aqueous Zn-ion batteries.