Prolonging rechargeable aluminum batteries life with flexible ceramic separator

Rechargeable aluminum batteries (RABs) are attracting significant attention for their high theoretical capacity and abundant reserves. However, the poor mechanical performance of glass fiber (GF) separators and the formation of Al dendrite severely hinder the practical cycle life of these batteries. Herein, a flexible ceramic separator was developed with simple coating technique, effectively improving the cycling stability of RABs. Compared with the commercial GF separator, this flexible ceramic separator has less thickness and superior electrolyte wettability, resulting in improved interfacial compatibility and minimized interfacial resistance. Moreover, its exceptional flexibility and toughness (stress of 39.34 MPa) coupled with uniform nanopore structure, which can effectively resist the penetration of dendrites. As expected, this ceramic flexible separator facilitates stable cycling of the symmetric battery for over 1762 h at 2 mA/cm² and 2 mAh/cm². It also permits the pouch Al//flake graphite full battery to achieve a coulombic efficiency of up to 90% even after 115 cycles. Apparently, this work developed the simple separator manufacturing strategy that provides an effective method to improve the cycling stability of RABs and extends the application to other types of batteries.