MDI Crosslinked And Modified Electrospun EVOH-SO₃Li/Al₂O₃ Separator For Lithium Ion Batteries

In order to develop a kind of lithium-ion battery separator with high practical value and excellent comprehensive performance,the chemical structure,micro-morphology and a series of physical properties of the MDI-EVOH-SO₃Li/Al₂O₃ composite fiber membrane were compared with commercial Celgard PP separator,EVOH-SO₃Li fiber membrane and MDI-EVOH-SO₃Li fiber membrane in this paper.The optimal adding amount of Al₂O₃ in MDI-EVOH-SO₃Li composite fiber separator was then determined.Finally,the obtained separator was assembled into the battery and tested for electrochemical performance and electrochemical cycle performance.The results indicate that the EVOH-SO₃Li fiber membrane and EVOH-SO₃Li/Al₂O₃ composite fiber membrane can crosslink with MDI,and can maintain the clear three-dimensional network structure after crosslinking.A comparison of the MDI-EVOH-SO₃Li fiber membrane indicates that the comprehensive physical property of MDI-EVOH-SO₃Li/Al₂O₃ composite fiber membrane with the 3 wt%adding amount of Al₂O₃ has best performance,and its electrolyte uptake,porosity,and thermal decomposition temperature rise from246%,62%and 240°C to 422%,80%and 251°C,respectively.The electrochemical performance and electrical cycle performance of the MDI-EVOH-SO₃Li/Al₂O₃ composite fiber membrane are analyzed.When compared with Celgard PP membrane,the electrochemical stability window of the MDI-EVOH-SO₃Li/Al₂O₃ composite fiber membrane increases from 4.5V to interface impedance decreased from 551?to 225?.The above data show that the compatibility between the composite fiber separator and the electrode has also strengthened.After the battery assembled with the obtained separator are tested for electrochemical cycle performance at discharge current densities of 0.2 C,0.5C,1 C,2 C,3 C,and 5 C,the discharge capacity of the composite fiber separator that was compared to Celgard PP separator is maintained at a high level.Additionally,after 100 cycles at the discharge current density of 0.5 C,the discharge capacity of the composite fiber separator battery corresponds to 149.03m Ahg^-1,and the retention rate corresponds to 95.33%;the discharge capacity of Celgard commercial PP separator corresponds to 130.22 m Ahg^-1,and the retention rate corresponds to 91.09%.Hence,the modified fiber membrane prepared in the study exhibites excellent comprehensive performance and is far superior to Celgard commercial PP separator.