Hydrogen‐Free and Dendrite‐Free All‐Solid‐State Zn‐Ion Batteries

An ionic‐liquid‐based Zn salt electrolyte is demonstrated to be an effective route to solve both the side‐reaction of the hydrogen evolution reaction (HER) and Zn‐dendrite growth in Zn‐ion batteries. The developed electrolyte enables hydrogen‐free, dendrite‐free Zn plating/stripping over 1500 h cycle (3000 cycles) at 2 mA cm–2 with nearly 100% coulombic efficiency. Meanwhile, the oxygen‐induced corrosion and passivation are also effectively suppressed. These features bring Zn‐ion batteries an unprecedented long lifespan over 40 000 cycles at 4 A g–1 and high voltage of 2.05 V with a cobalt hexacyanoferrate cathode. Furthermore, a 28.6 µm thick solid polymer electrolyte of a poly(vinylidene fluoride‐hexafluoropropylene) film filled with poly(ethylene oxide)/ionic‐liquid‐based Zn salt is constructed to build an all‐solid‐state Zn‐ion battery. The all‐solid‐state Zn‐ion batteries show excellent cycling performance of 30 000 cycles at 2 A g–1 at room temperature and withstand high temperature up to 70 °C, low temperature to –20 °C, as well as abuse test of bending deformation up to 150° for 100 cycles and eight times cutting. This is the first demonstration of an all‐solid‐state Zn‐ion battery based on a newly developed electrolyte, which meanwhile solves the deep‐seated hydrogen evolution and dendrite growth problem in traditional Zn‐ion batteries. Zn anodes persistently suffer from deep‐seated issues of the parasitic hydrogen evolution reaction (HER) and dendrite growth. Meanwhile, hydrogel‐based Zn batteries suffer from poor mechanical properties and dehydration. An ionic‐liquid‐based Zn salt electrolyte to solve both the side‐reaction of the HER and Zn‐dendrite growth is developed. Furthermore, a solid polymer electrolyte is constructed to build an all‐solid‐state Zn‐ion battery.