Cosolvent electrolyte chemistries for high-voltage potassium-ion battery

The poor oxidation resistance of traditional electrolytes has hampered the development of high-voltage potassium-ion battery technology. Here, we present a cosolvent electrolyte design strategy to overcome the high-voltage limitations of potassium-ion electrolyte chemistries. The cosolvent electrolyte breaks the dissolution limitation of the salt through ion–dipole interactions, significantly enlarging the anion-rich solvation clusters, as verified by the in situ synchrotron-based wide-angle X-ray scattering experiments.Furthermore, the large anion-rich solvation clusters also facilitate the formation of an effective electrode–electrolyte interphase, thereby enhancing compatibility with high-voltage electrodes. The cosolvent electrolyte enables K||Prussian blue cells (2–4.5 V) to operate for >700 cycles with a capacity retention of 91.9%. Our cosolvent electrolyte design strategy paves new avenues for the development of high-voltage potassium-ion batteries and beyond.