Poly(vinylidene fluoride)-Based Al Ion Conductive Solid Polymer Electrolyte for Al Battery

Al ion conductive solid polymer electrolyte is prepared using poly(vinylidene fluoride) (PVdF) and AlCl3 as a host polymer and Al ion salt, respectively. AlCl3 salt can be dissolved into PVdF and uniformly distributed in the polymer up to F/Al ratio is 8. With further increase in the AlCl3 content, a phase separation of AlCl3 and PVdF is observed. It is noted that melting and amorphization temperatures of PVdF are also affected by the content of AlCl3. The melting temperature and promotion of crystallization of PVdF decrease with increase in AlCl3 until F/Al to be 8. With further increase in AlCl3, the melting and crystallization temperature increase. Through FT-IR characterization, it is observed that characteristic frequency peaks relating CF vibration shift with addition of AlCl3, indicating that Al cation interacts with F in the PVdF host. The highest conductivity is 4.4 × 10−4 S cm−1 at room temperature is achieved at F/Al ratio equaling 8. The cation transference number of this Al polymer electrolyte is 0.24 which is close to that of PVdF-based Li ion conductive polymer. The electrochemical stable window of the PVdF-AlCl3 polymer at F/Al ratio of 8 is 0 ∼ 2.4 V vs. Al3+/Al. The electrochemical stable window covers redox voltages of most reported cathode materials for rechargeable Al batteries, implying that this PVdF-based polymer electrolyte can be a good candidate for the Al batteries.