Mechanically Robust and Safe Separators Based on Inorganic Nanofibers for Lithium-Ion Batteries

Commercial polyolefin separators suffer from inferior electrolyte affinity, low thermal stability, and other serious safety concerns. Ceramic separators are promising alternatives to alleviate these issues, but the fragile structure restricts practical applications. A mechanically robust, high-safety, and flame-retardant composite separator (BHLP) of a hierarchical cross-linked architecture is constructed based on a multibond reinforcement mechanism. The inorganic and organic components of the separator are tightly integrated through electrostatic forces, hydrogen bonds, and chemical bonds. The as-prepared separator exhibits high tensile strength (16.28 MPa), which is approximately 1.7 times that of the PP separator in the transverse direction. Benefiting from the excellent thermal stability and high aspect ratio of hydroxyapatite nanowires, the thermal shrinkage of the BHLP separator is negligible after heating at 200 °C for 1 h and it features with has a highly porous nanostructure, good electrolyte affinity, and high ionic conductivity (0.87 mS cm–1). The LiNi0.8Co0.1Mn0.1O2||graphite full cell with the BHLP separator performs a high specific discharge capacity (184.7 mA h g–1) at 0.1C and outstanding cycling stability with the capacity retention of 93.9% over 100 cycles at room temperature.