Ionic Liquid-Softened Polymer Electrolyte for Anti-Drying Flexible Zinc Ion Batteries
Donghong Wang, Xun Guo, Ze Chen, Yuwei Zhao, Qing Li, Chunyi Zhi
Abstract
Using solid polymer electrolytes has been proven to be an efficient strategy to address the metal dendrites and pursuing high-voltage performance. Polyethylene oxide (PEO), as a popular polymer matrix, hardly works for zinc ion batteries due to its poor zinc ionic conductivity and the poor interfacial adhesion. Here, an ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim]OTF), was applied as a plasticizer to tune the room-temperature ionic conductivity and mechanical properties of PEO membrane electrolyte. Additional nanofillers ZnO were utilized to enhance the plasticity and modulus. With an optimized composition, the membrane exhibits a high modulus and soft mechanics, which can facilitate the reversible stripping/plating of Zn without formation of Zn dendrites. The optimized polymer electrolyte achieved an ionic conductivity of 2.3 × 10–3 S cm–1 at room temperature with a softness of 5.1 mm. By applying the resulted soft membrane electrolyte for a Zn-MnO2 battery, a capacity of 137 mAh g–1 is achieved at 30 mA g–1 even without the contribution from H+. Such an electrolyte also works for Prussian blue analogue cathodes. Importantly, the addition of [Emim]OTF can enhance the soft contact with the electrodes, and a stable output is delivered under severe deformations for the assembled flexible devices.