Nano‐Interfacial Supramolecular Adhesion of Metal–Organic Framework‐Based Separator Enables High‐Safety and Wide‐Temperature‐Range Lithium Batteries

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-08, Vol.20 (33), p.e2400980-n/a
• Main Authors: Gao, You, Liu, Qing‐Song, Long, Man‐Cheng, Zhu, Guo‐Rui, Wu, Gang, Wang, Xiu‐Li, Wang, Yu‐Zhong
• Format: Article
• Language: English
• Subjects: Adhesion; Cycles; Electrolytic cells; high safety; High temperature; Ion currents; Lithium batteries; lithium battery; Membranes; Metal-organic frameworks; metal–organic framework; Polyolefins; Porosity; separator; Separators; Thermal stability; wide temperature range
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202400980

Polyolefin separators are the most commonly used separators for lithium batteries; however, they tend to shrink when heated, and their Li+ transference number (t Li+) is low. Metal–organic frameworks (MOFs) are expected to solve the above problems due to their high thermal stability, abundant pore structure, and open metal sites. However, it is difficult to prepare high‐porosity MOF‐based membranes by conventional membrane preparation methods. In this study, a high‐porosity free‐standing MOF‐based safety separator, denoted the BCM separator, is prepared through a nano‐interfacial supramolecular adhesion strategy. The BCM separator has a large specific surface area (450.22 m2 g−1) and porosity (62.0%), a high electrolyte uptake (475 wt%), and can maintain its morphology at 200 °C. The ionic conductivity and t Li+ of the BCM separator are 1.97 and 0.72 mS cm−1, respectively. Li//LiFePO4 cells with BCM separators have a capacity retention rate of 95.07% after 1100 cycles at 5  C, a stable high‐temperature cycling performance of 300 cycles at 80 °C, and good capacity retention at −40 °C. Li//NCM811 cells with BCM separators exhibit significantly improved rate performance and cycling performance. Pouch cells with BCM separators can work at 120 °C and have good safety at high temperature. A high‐porosity free‐standing MOF‐based separator is prepared through a nano‐interfacial supramolecular adhesion strategy with calcium alginate as the binder, bacterial cellulose as the skeleton and metal‐organic framework (MOF) as the matrix. This separator can capture water and exhibit high electrolyte uptake, good ionic conductivity, large Li+ transference number, and excellent thermotolerance, which endow lithium batteries with superior electrochemical performance and safety.