Hydrogen-bond regulation in organic/aqueous hybrid electrolyte for safe and high-voltage K-ion batteries

High reliability and proven ultra-long life make aqueous batteries ideal for grid energy storage. However, the narrow electrochemical stability window (ESW) caused by the high activity of H2O severely hampers their practical applications. Here, hydrogen-bond (H-bond) regulation is applied using succinonitrile (SCN) to reconstruct the binding state of H2O molecules, in which the "free H2O" with strong H-bond network is converted to the "immobilized H2O" restricted by SCN molecules, thus inhibiting the activity of H2O. The designed 5.6 m KFSI-SCN-H2O hybrid electrolyte exhibits an expanded ESW over 4.0 V, particularly with a high anodic limit above 5.1 V, which is the highest among the reported aqueous K-ion electrolytes. Moreover, the electrolyte possesses non-flammability, improved conductivity, and a wider applicable temperature range. As a result, the assembled KVPO4F||PTCDI full cell exhibits excellent cycling stability over 10 000 cycles with a low capacity decay of 0.0025% per cycle and provides a competitive energy density of about 100 W h kg-1. This work provides insights into how the H-bond regulation strategy inhibits the activity of H2O in organic/aqueous hybrid electrolytes, offering a promising pathway to achieve higher-energy-density aqueous batteries without compromising safety. Hydrogen-bond regulating organic/aqueous hybrid electrolyte with immobilized H2O provides new insights into realizing high-voltage aqueous batteries without compromising safety.