Phosphorus-Doped Carbon Nitride/Cellulose Nanofibril Composite Membrane Interlayer for Synergistic Regulation of Zn Deposition in Aqueous Zinc-Ion Batteries

In this study, a novel composite membrane composed of phosphorus-doped carbon nitride (PCN) and cellulose nanofibril (CNF), namely PCN@CNF, was developed as an interlayer for aqueous zinc-ion batteries (AZIBs) with the objective of addressing critical issues such as zinc dendrite growth and side reactions. PCN was prepared via one-step calcination of sodium dihydrogen phosphate (NaH2PO4) and melamine (C3H6N6), while PCN@CNF composite was fabricated through ultrasonic-assisted vacuum filtration. The resultant PCN@CNF membrane exhibits a densely packed structure and excellent mechanical properties, along with abundant nitrogen and phosphorus functionalities that impart strong zincophilicity. Owing to these features, the PCN@CNF interlayer effectively suppresses zinc dendrite formation and side reactions in AZIBs by synergistically regulating the zinc-ion flux and homogenizing the distribution of electric and ionic fields at the electrode/electrolyte interface. Remarkably, Zn||Zn symmetric cells incorporating the PCN@CNF interlayer demonstrated stable cycling for over 800 h at 5 mA cm–2 and 5 mAh cm–2. Furthermore, Zn||Cu asymmetric cells achieved an average Coulombic efficiency of 99.25% over 500 h. In addition, electrochemical evaluations of Zn-MnO2 full cells confirmed that the PCN@CNF interlayer significantly enhances both specific capacity and long-term cycling stability. Besides, pouch batteries assembled with PCN@CNF could work normally even under some extreme conditions, demonstrating superb safety in real-world practice.