Low-Cost,Safe, and Ultra-Long Cycle Life Zn–K Hybrid Ion Batteries

Zinc-ion batteries (ZIBs) are viewed as a promising energy storage system for large-scale applications thanks to the low cost and wide accessibility of Zn-based materials, the high theoretical capacity of Zn anode, and their high level of safety. However, the practical application of ZIBs is hindered by the rapid performance degradation. Herein, a Zn–K hybrid ion battery design is proposed using a high-quality Prussian blue cathode and a nonflammable Zn–K hybrid ion electrolyte. The electrochemical process is divided into two parts, with K⁺ insertion/extraction occurring at the cathode side and Zn²⁺ plating/stripping occurring at the anode side, which avoids structure destruction caused by Zn²⁺ insertion in the cathode. The non-flammable electrolyte not only ensures high safety but also effectively suppresses dendrite growth on the Zn anode. The hybrid cells demonstrate a high capacity of 151.0 mAh g^?1, a high voltage of 1.74 V (vs Zn²⁺/Zn), and an ultra-long cycle life of 15 000 cycles. Combining the nonflammable nature of the electrolyte, the abundance of raw materials, and good electrochemical performance, the Zn–K hybrid ion battery system promises a promising future for renewable energy storage applications.