Flexible and free-standing LiFePO4/TPU/SP cathode membrane prepared via phase separation process for lithium ion batteries

A series of flexible and free-standing cathodes with different mass ratios of LiFePO4, thermoplastic polyurethane (TPU) and super P (SP) (LFP/TPU/SP) are fabricated by a phase separation process. The obtained cathode membranes show highly porous and interwoven network structure, and possess excellent cycling stability and rate capability. The electrolyte uptake, electrochemical impedance spectra (EIS) and the apparent Li+ diffusion coefficient (DLi+) tests indicate that the porous polyurethane networks promote the electrolyte infiltration and accelerate Li ions transformation. Compared with the traditional cathode, the cathode prepared at the LFP/TPU/SP ratio of 4:5:1 (wt:wt) presents a much better rate capability than the traditional one. It delivers a discharge capacity of 153 and 93 mA h g−1 at 0.2C and 10C rates, respectively. The phase separation process is inexpensive and environmentally friendly, which provides a promising way to fabricate flexible and free-standing cathode.