“Breathing” Mechanism of Polymer Pillar In/Out of Lattice Enabling High‐Loading Cathodes for Aqueous Zinc Batteries
Wenjun Zhao, Quanwei Jiang, Yijie Jiang, Sibo Wang, Wanlong Wu, Jie Liu, Hua‐Yu Shi, Xiaoxia Liu, Xiaoqi Sun
Abstract
Abstract Vanadium oxide cathodes for aqueous zinc batteries require enhanced kinetics at high rates and high loadings. Herein, a polyacrylamide (PAM) intercalated layered vanadium oxide (PAM‐VO) is prepared. It undergoes a unique “breathing” mechanism during discharge and charge, with the PAM pillar presenting bi‐functional roles to promote reaction kinetics. Specifically, water molecules co‐intercalate with Zn 2+ during discharge and facilitate cation diffusion in lattices. Interestingly, it also leads to the swelling of hydrophilic PAM, which further induces partial layer exfoliation and pillar release. It in situ generates cation‐conducting hydrogel around parent particles, thereby facilitating cation transport at grain boundaries. A reversible change is noted during charge so that the integrity and stability of the cathode are retained. Thanks to the rapid cation transport both in lattices and at grain boundaries, the PAM‐VO cathode achieves 545 mAh g −1 capacity at 0.2 A g −1 and retains 190 mAh g −1 at a high current density of 50 A g −1 , superior to 270 and 3 mAh g −1 , respectively, obtained with a regular water‐pillared cathode. A high area capacity of 17.5 mAh cm −2 is also realized at a high PAM‐VO loading of 45.4 mg cm −2 . The excellent performance further enables an Ah‐level pouch cell.