Trifunctional DOPO‐Engineered Polypropylene Separator With Li⁺‐Concentrating Interfaces for High‐Safety Lithium‐Ion Batteries Under Extreme Conditions
Wende Yi, Wufei Tang, Weikang Su, Keren Shi, Qiaowei Xiao, Z. Wang, Xiaoyu Li, Jing Mu, Huiqin Yao, Zhihan Peng
Abstract
Abstract This study develops a cross‐linked polymer modified polypropylene (PP) separator for lithium‐ion batteries, using DOPO (9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide). The separator features surface‐rich polar functional groups (such as ‐NH 2 ) and bonded structures (P‐O, P = O), enhancing Li + ion migration via dipole‐dipole interactions. The modified separator demonstrates improved microstructural stability, thermal stability (>90 °C), and mechanical strength (>200 MPa). Batteries using this separator maintain excellent capacity retention (105.2 mAh g −1 ) after high‐temperature cycling (130 °C at 2C) and show good flame retardancy (self‐extinguishing). Density functional theory (DFT) calculations explain the Li + enrichment mechanism and the separator's thermal/flame‐retardant properties. This work pioneers the multifunctional use of DOPO in lithium‐ion battery separators, combining flame retardancy, enhanced Li + conductivity, and improved stability, offering a novel approach to producing safer, high‐performance separators for large‐scale applications.