Hierarchical porous separator with excellent isotropic modulus enabling homogeneous Zn2+ flux for stable aqueous Zn battery

Low-cost, high-safety aqueous Zn-ion batteries show promise for large-scale energy storage, but the unsatisfactory cycling stability of Zn anodes and the lack of a suitable hydrophilic separator for rechargeable aqueous Zn batteries limit their practical applications. In this work, we report a scalable method for the preparation of a homogenous polyvinylidene fluoride-lithium bistrifluoromethanesulfonimide (LiTFSI) (PVDF-Li)-based separator for aqueous Zn batteries. The homogenously mixed LiTFSI salt interrupted the crystalline framework of PVDF with excellent mechanical strength and led to hierarchical pore structures for the rapid and uniform Zn2+ flux through the separator. Meanwhile, the PVDF-Li separator exhibited excellent wettability toward aqueous Zn electrolytes. With the advanced PVDF-Li separator, the Zn dendrite growth can be suppressed greatly, showing an improved cycle life. The Zn||V2O5 full cell with PVDF-Li separator exhibited a 27% higher initial capacity (324 mA h g(-1)) and considerably better capacity retention than the traditional glass fiber separator due to the uniform reaction on the V2O5 cathode and Zn anode sides. This work provides new insights into the development of high-performance aqueous batteries by regulating the reactions on the cathode and anode through functional separators.