Poly(vinyl alcohol)/Melamine Composite Containing LATP Nanocrystals as a High-Performing Nanofibrous Membrane Separator for High-Power, High-Voltage Lithium-Ion Batteries

Electrolyte uptake and thermal stability of separators are important factors in Li-ion battery application. Here, a poly(vinyl alcohol)/melamine composite nanofiber membrane containing LATP nanocrystals (PVAM composite membrane) is prepared by the electrospinning method and is used as the separator in a high-power, high-voltage Li-ion battery. The performance of the homemade membrane is benchmarked with a commercial polyethylene (PE) separator. The characteristic properties such as morphology, porosity, electrolyte contact angle, electrolyte uptake/retention, and thermal shrinkage of the PVAM composite membranes are systematically investigated. The results demonstrate that electrospun PVAM composite membranes offer notable advantages including high porosity, low thermal shrinkage, high electrolyte uptake, and high ionic conductivity. A lithium half-cell using spinel-type Li4Ti5O12 (LTO) anode and a PVAM composite nanofiber membrane exhibits superior rate capability and cycling performance compared to the corresponding device fabricated using the commercial PE separator. The results show improved capacity retention in the PVAM-based cell (95% for 800 cycles) compared to the PE separator-based cell (∼49% for 500 cycles). A full cell constructed with a spinel-type LiNi0.5Mn1.5O4 (LNMO) cathode, a PVAM composite membrane, and an LTO anode also exhibits higher capacity retention (∼98%) than that fabricated using the PE separator (∼93%) for 100 cycles at a 1C rate. The superior electrolyte wettability, high porosity, and three orders of magnitude higher ionic conductivity of PVAM composite membrane provide faster Li+-ion transport than the commercial analogue, making it an excellent membrane for high-power, high-voltage LNMO//LTO battery application.