3D printed separator for the thermal management of high-performance Li metal anodes

Lithium (Li) metal anodes with a high theoretical gravimetric capacity and a low redox potential have attracted considerable attention for Li-ion based batteries, including Li-sulfur (Li-S) and Li-oxygen (Li-O2) batteries. The elimination of safety concerns and long cycling stability issues are the main challenges that must be solved to apply Li metal anodes in any application. Herein, we design a novel and safe separator for Li metal batteries by integrating thermally management boron nitride (BN) nanosheets into poly vinylidene fluoride-hexafluoropropene (PVDF-HFP) via an advanced extrusion based 3D printing technique. The BN-separator offers a uniform thermal distribution interface, which enables homogeneous Li nucleation, enhanced suppression of Li dendrite growth, and further improves the overall electrochemical performance. A stable Coulombic efficiency of 92% is maintained after 90 cycles at 1 mA cm−2 by using this novel separator in Li/Cu cells. In contrast, the Coulombic efficiency of the control cells decreases to 70% after 30 cycles at a current density of 1 mA cm−2. In addition, in a Li/Li symmetric configuration, the cells using the 3D printed BN-separator exhibit improved cycling stability with lower voltage polarization over 500 h. Our findings on 3D printing for a thermally managing BN-separator can serve as a general strategy for further advanced rechargeable batteries.