A non-conventional fluorinated separator in high-voltage graphite/LiNi0.4Mn1.6O4 cells

Graphite/LiNi0.4Mn1.6O4 cells assembled with a new reinforced polyvinylidene fluoride (pVDF)- nano crystalline cellulose (NCC) separator and EC–DMC 1 M LiFAP electrolyte with additives were tested by deep charge-discharge cycles at different C-rates and by the FreedomCAR DOE protocol to simulate the dynamic functioning of the batteries in power-assist full hybrid electric vehicles (HEVs). The results of this study evidence the beneficial impact of the pVDF-NCC macroporous membrane with respect to the polypropylene monolayer Celgard®2400 separator on the high C-rate cell performance. The deep charge-discharge of the cell with pVDF-NCC at C/1 effective rate provided 101 Wh kg-1 to be compared with 85 Wh kg-1 of the cell with Celgard®2400 (the cell weight was considered twice the composite electrode weight of both electrodes). Also Hybrid Pulse Power Characterization tests based on the FreedomCAR protocol at 5C and 10C demonstrated the superior performance of the cells with pVDF-NCC with respect to that of the cells with Celgard®2400 even if both cells exceed the FreedomCAR goals of power and energy for minimum and maximum power-assist HEV.