Development of AlN-loaded PET separators from waste water bottle plastics with superior thermal characteristics for next-generation lithium-ion batteries

Preventing short circuit hazard due to lithium (Li) dendrite formation across a separator from the anode of a lithium-ion battery (LIB) throughout operation is important; however, conventional separator materials cannot fulfil the increasing safety standards of next-generation LIBs. Thus, developing separator materials with high Li dendrite suppression ability in order to prevent short circuit is of paramount importance for realising next-generation LIBs. In this study, aluminum nitride-loaded polyethylene terephthalate (PET/AlN) composites with micro-/nanoarchitecture were synthesized using PET that was recycled from commercial waste bottles via an electrospinning strategy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) suggested that AlN nanoparticles were encapsulated in PET micro-/nanoarchitecture fibres. Thermogravimetric analysis indicated that the AlN content in the composite materials was about 4-5 wt%. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy confirmed the PET polymer structure of PET/AlN composites. The PET/AlN 4 wt% separator exhibited a porosity of 69.23%, according to the n-butanol uptake test, and a high electrolyte uptake of 521.69%. Most importantly, electrochemical results revealed that when evaluated at a current density of 0.5C, PET/AlN 4 wt% composites could deliver a reversible specific capacity of 238.2 mA h g⁻¹ after 100 cycles. When C-rate capability tests were conducted at high charge-discharge densities of 0.2, 0.5, 1, 2, and 4C, the PET/AlN 4 wt% composite manifested average specific capacities of about 225.3, 218.4, 191.0, 127.5, and 28.1 mA h g⁻¹, respectively. The excellent electrochemical performance of the PET/AlN 4 wt% composite could probably be attributed to the combined benefits of AlN nanoparticles and the micro-/nanoarchitecture. These unique features of PET/AlN were advantageous for effective Li ion transport in repeated charge-discharge cycles and strong hydrothermal stability, thereby resulting in safety, high capacity and excellent C-rate performance. Overall, this study demonstrated the excellent electrochemical performance of PET/AlN composites as stable separator materials for advanced LIBs.