Electrospun polyimide-based fiber membranes as polymer electrolytes for lithium-ion batteries

Polymer electrolytes based on electrospun polyimide (PI) membranes are incorporated with electrolyte solution containing 1 mol L−1 LiPF6/ethylene carbonate/ethylmethyl carbonate/dimethyl carbonate to examine their potential application for lithium ion batteries. The as-electrospun non-woven membranes demonstrate a uniformly interconnected structure with an average fiber diameter of 800 nm. The membranes, showing superior thermal stability and flame retardant property compared to the commercial Celgard® membranes, exhibit high porosity and high uptake when activated with the liquid electrolyte. The resulting PI electrolytes (PIs) have a high ionic conductivity up to 2.0 × 10−3 S cm−1 at 25 °C, and exhibit a high electrochemical stability potential more than 5.0 V (vs. Li/Li+). They also possess excellent charge/discharge performance and capacity retention. The initial discharge capacities of the Li/PIs/Li4Ti5O12 cells are 178.4, 167.4, 160.3, 148.3 and 135.9 mAh g−1 at the charge/discharge rates of 0.2 C, 1 C, 2 C, 5 C and 10 C, respectively. After 200 cycles at 5 C, a capacity around ∼146.8 mAh g−1 can be still achieved. The PI-based polymer electrolytes with strong mechanical properties and good electrochemical performance are proved to be promising electrolytes for lithium ion batteries.