Effect of the degree of porosity on the performance of poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) blend membranes for lithium-ion battery separators

Porous polymer membranes based on poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) copolymers, P(VDF-TrFE)/PEO, are prepared through elimination (from partial to total) of PEO, leading to interconnected micropores in the polymer blends. Electrolyte uptake, thermal and mechanical properties depend on the amount of PEO present in the polymer blend. Further, the degree of crystallinity of PEO and the elastic modulus (E') of the polymer blend decrease with increasing PEO removal. Electrical properties of the polymer blend membranes are influenced by the porosity and are dominated by diffusion. The temperature dependence of the ionic conductivity follows the Arrhenius behavior. The ionic conductivity is the highest for the membranes with a volume fraction of pores of 44% (i.e., 90% PEO removal), reaching a value of 034 mS cm(-1) at room temperature. Battery performance was determined by assembling Li/C-LiFePO4 swagelok cells. The polymer blends with 90% PEO removal exhibit rate (124 mAhg(-1) at C/5 and 47 mAhg(-1) at 2C) and cycling capabilities suitable for lithium ion battery applications. JLGR acknowledges the support of the Ministerio de Economia y Competitividad, MINECO, through the MAT2013-46467-C4-1-R project (including FEDER financial support). CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. Gören, A.; Costa, CM.; Tamaño Machiavello, MN.; Cintora-Juarez, D.; Nunes-Pereira, J.; Tirado, J.; Silva, MM... (2015). Effect of the degree of porosity on the performance of poly(vinylidene fluoride-trifluoroethylene)/poly(ethylene oxide) blend membranes for lithium-ion battery separators. Solid State Ionics. 280:1-9. https://doi.org/10.1016/j.ssi.2015.08.003