Thermodynamic and electrochemical properties of co-spun polyvinyl-vinyl alcohol lithium-thermoplastic polyurethane lithium ion battery separator

In order to improve the thermodynamic and electrochemical properties of lithium ion battery separators, polyvinyl-vinyl alcohol lithium(EVOH-Li) and thermoplastic polyurethane (TPU) were used as the raw materials. High voltage electrospinning was used to spin two needles simultaneously. The EVOH-Li-TPU co-spinning separators for lithium ion batteries were prepared. The EVOH-Li has free de-intercalation lithium ions. The ionic conductivity of battery separator is increased. The TPU has good mechanical properties and toughness. The puncture resistance of lithium ion battery separator is increased, and its security is improved. The morphology, mechanical properties, liquid absorption, porosity, thermal properties and electrochemical properties of the EVOH-Li-TPU co-spinning separators were studied, and compared with EVOH-Li and TPU mono-spun membranes. The results show that the tensile strength and elongation at break of the EVOH-Li-TPU co-spinning separator reach to 6.09 MPa and 79.26%, the porosity and liquid absorption reach to 84% and 321%, the ionic conductivity at room temperature is 4.41×10⁻⁴ S/cm, the interfacial impedance is reduced compared with the EVOH-Li and TPU mono-spun membranes, and the electrochemical window is 5.0 V. Comparing with EVOH-Li and TPU single spinning, the properties of EVOH-Li-TPU co-spinning separators is improved.