Janus separator with high-temperature resistance and dendrite suppression for advanced Li-ions batteries

Undesirable thermal runaway and short circuits induced by thermal instability, limited wettability, and susceptibility to lithium dendrite penetration of commercial polyolefin separators have posed severe safety issues for Li-ion batteries (LIBs). Herein, we present a heat- and dendrite-resistant Janus separator (AH@PP) for advanced LIBs that incorporates coating of aramid nanofiber (ANF) network combined with hydroxyapatite (HAP) nanoparticles on one side of PP separator. The robust (7 GPa of modulus), thin and nanoporous ANF/HAP network is in contact with lithium anode and serves as a protective layer to prevent lithium dendrite penetration, while the porous bare PP adheres to the cathode side to preserve the Li-ions transport channels. The obtained AH@PP separator shows improved wettability, more superior mechanical strength and excellent thermostability than conventional PP separators. The LIB with a mass-loading of 14.7 mg cm−2 equipped with the AH@PP separator provides a high initial capacity of 140.9 mAh g−1 as well as an exceptional preservation capacity (118.2 mAh g−1 at 0.5C after 250 cycles). Excitingly, the AH@PP separator exhibits exceptional voltage stability at elevated temperatures of 110 °C and facilitates reliable operation of pouch cell of various configurations. This work presents a cost-effective method to enhanced separators for next-generation LIBs.