Stabilizing high-rate potassium storage by ferromagnetism.

In this work, pre-magnetized ε-FeO was used as prototype electrode material to reveal the synergetic effect between ferromagnetism and electrochemical performance. Upon high-rate potassiation, ε-FeO was unable to fully participate in conversion reaction due to "potassiation retardation". The higher the rate was, the less complete the conversion reaction became.