The mechanical strength of separators should be strong enough
to suffer mechanical handling during cell winding and assembly.
As can be seen fromFig. 5a and b, the SiO2/PEI-PU membranes are
not mechanical broken after being folded and twisted several
times, implying their potential applications in cells. Meanwhile,
the stress-strain curves of as-prepared PEI-PU and SiO2/PEI-PU
membranes are showed inFig. 5c. It can be seen that both PEI-PU
and SiO2/PEI-PU composite membranes show a linear elastic
deformation in thefirst stage due to the non-bonding structure of
PEI-PUfibers slipping through frictional entanglement at lower
stress[20,36], and then the stress-strain curves exhibit a quasilinear elastic increase until the fibers break. This phenomenon
could be explained by the two-step break mechanism. As seen
from the FE-SEM images, both PEI-PU and SiO2/PEI-PU composite
membranes possess the bonding and non-bonding structures,
which could cause different structural transformations in the
strain process. When a small external load is applied, the
nonaligned nanofibers in membranes are forced to be aligned
along the stress direction, resulting in the first linear elastic
behavior[20,36]. With the continual increase in tensile stress, the
curve shows a quasi-linear elasticity due to the slip of PEI-PUfibers
along stress direction. Andfinally, the break of relevant membranes is resulted from the break offibers between the bonding
points[37]. As shown inTable 1, the tensile strength of SiO2/PEI-PU
composite membranes (15.65 MPa) is much higher than that of
PEI-PU membranes (8.74 MPa), which could be due to the
formation of more bonding structure between the adjacent layers
after coating. Consequently, the above results suggest that the
SiO2/PEI-PU composite membranes possess robust mechanical
property, which could be applied as promising materials for
potential applications in high-performance LIBs
The mechanical strength of separators should be strong enoughto suffer mechanical handling during cell winding and assembly.As can be seen fromFig. 5a and b, the SiO2/PEI-PU membranes arenot mechanical broken after being folded and twisted severaltimes, implying their potential applications in cells. Meanwhile,the stress-strain curves of as-prepared PEI-PU and SiO2/PEI-PUmembranes are showed inFig. 5c. It can be seen that both PEI-PUand SiO2/PEI-PU composite membranes show a linear elasticdeformation in thefirst stage due to the non-bonding structure ofPEI-PUfibers slipping through frictional entanglement at lowerstress[20,36], and then the stress-strain curves exhibit a quasilinear elastic increase until the fibers break. This phenomenoncould be explained by the two-step break mechanism. As seenfrom the FE-SEM images, both PEI-PU and SiO2/PEI-PU compositemembranes possess the bonding and non-bonding structures,which could cause different structural transformations in thestrain process. When a small external load is applied, thenonaligned nanofibers in membranes are forced to be alignedalong the stress direction, resulting in the first linear elasticbehavior[20,36]. With the continual increase in tensile stress, thecurve shows a quasi-linear elasticity due to the slip of PEI-PUfibersalong stress direction. Andfinally, the break of relevant membranes is resulted from the break offibers between the bondingpoints[37]. As shown inTable 1, the tensile strength of SiO2/PEI-PUcomposite membranes (15.65 MPa) is much higher than that ofPEI-PU membranes (8.74 MPa), which could be due to theformation of more bonding structure between the adjacent layersafter coating. Consequently, the above results suggest that theSiO2/PEI-PU composite membranes possess robust mechanicalproperty, which could be applied as promising materials forpotential applications in high-performance LIBs
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