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

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 degrees 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 degrees C, and good capacity retention at -40 degrees C. Li//NCM811 cells with BCM separators exhibit significantly improved rate performance and cycling performance. Pouch cells with BCM separators can work at 120 degrees 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. image