Bi-functional poly(vinylidene difluoride) coated Al anodes for highly rechargeable aqueous Al-ion batteries

Aqueous rechargeable aluminum (Al) ion batteries have attracted much attention due to the high abundance of Al metal and high volumetric energy density (8040 mAh cm−3). However, Al anode suffers from hydrogen evolution side reactions in aqueous electrolyte due to its low equilibrium redox potential. Here, we developed a poly(vinylidene difluoride) (PVDF) coating that can inhibit free H2O/O2 and alleviate the corrosion problem. Theoretical calculations verify that PVDF and Al3+ have a strong interaction through the F-Al bond towards the observed uniform Al deposition. As a result, the cell of PVDF-Al/K2CoFe(CN)6 achieved 98.2% Coulombic efficiency after 400 cycles at a current density of 100 mA g−1. This work presents an effective and facile strategy to the development of high-performance and low-cost aqueous Al-ion batteries.