Nano architectured halloysite nanotubes enable advanced composite separator for safe lithium metal batteries

Lithium metal anode has attracted wide attention due to the highest theoretical specific capacity, the lowest anode potential, and low gravimetric density. Nevertheless, the uncontrollable growth of lithium dendrites during the cycling process may pierce through polymer separator and induce safety concerns extremely restricting the further application. In this work, nano architectured halloysite nanotubes (NHNTs) are employed to fabricate high performance poly (vinyl alcohol) composite separator (OPVA/NHNTs separator) that can effectively enhance the electrochemical performance and safety of lithium metal batteries. The results indicate that, compared to Celgard and control OPVA separators, OPVA/NHNTs separator exhibits both high Young's modulus and ion conductivity, which can efficiently retard the growth of lithium dendrites and maintain the electrochemical properties. Additionally, from the comparison between OPVA/HNTs OPVA/NHNTs separator, it can be revealed that in contrast to Monroe-Newman theory, composite separator with only high Young's modulus can hardly retard the growth of lithium dendrites, as high ion conductivity also plays a crucial role in promoting the even distribution of lithium ions, which can effectively suppress the germination of lithium whiskers. This work verifies the importance of nanomaterials in suppressing lithium dendrites and provides a new idea to employ nano science to design and fabricate high-performance polymer composite separators that can meet the electrochemical performance and safety performance of lithium metal batteries.