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Trifunctional DOPO-Engineered Polypropylene Separator With Li⁺-Concentrating Interfaces for High-Safety Lithium-Ion
Wende Yi1,2, Wufei Tang1,2, Weikang Su1
1College of Chemistry and Bioengineering, Hunan University of Science and Engineering, Yongzhou, 425199, China.
Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
|October 14, 2025
Summary
This study introduces a novel polymer-modified polypropylene separator for lithium-ion batteries, enhancing safety and performance. The DOPO-modified separator improves ion conductivity, thermal stability, and flame retardancy for advanced battery applications.
Area of Science:
- Materials Science
- Electrochemistry
- Polymer Chemistry
Background:
- Polypropylene (PP) separators are crucial for lithium-ion battery safety and performance.
- Enhancing ion conductivity, thermal stability, and flame retardancy in PP separators remains a key challenge.
- Current separators often compromise between safety features and electrochemical performance.
Purpose of the Study:
- To develop a cross-linked polymer-modified polypropylene separator using DOPO for enhanced lithium-ion battery performance.
- To investigate the impact of DOPO modification on the separator's microstructural, thermal, and mechanical properties.
- To elucidate the mechanisms behind improved Li+ ion migration and flame retardancy.
Main Methods:
- Polymer modification of polypropylene separators using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).
- Characterization of surface functional groups, microstructural stability, thermal stability, and mechanical strength.
- Electrochemical testing of lithium-ion batteries with modified separators, including high-temperature cycling.
- Density Functional Theory (DFT) calculations to model ion migration and flame retardancy.
Main Results:
- The DOPO-modified PP separator exhibited surface-rich polar functional groups and enhanced Li+ ion migration via dipole-dipole interactions.
- Improved microstructural stability, thermal stability (>90 °C), and mechanical strength (>200 MPa) were achieved.
- Batteries demonstrated excellent capacity retention (105.2 mAh g-1) after high-temperature cycling (130 °C at 2C) and good flame retardancy.
- DFT calculations confirmed the Li+ enrichment mechanism and the separator's thermal/flame-retardant properties.
Conclusions:
- DOPO modification offers a multifunctional approach to enhance lithium-ion battery separators.
- The developed separator combines flame retardancy, improved Li+ conductivity, and superior stability.
- This work presents a novel strategy for producing safer, high-performance separators for large-scale lithium-ion battery applications.
