  Nonvolatile resistive-switching (RS) memories promise to revolutionize
hardware architectures with in-memory computing. Recently, ion-interclation
materials have attracted increasing attention as potential RS materials for
their ion-modulated electronic conductivity. In this Letter, we propose RS by
multiphase polarization (MP) of ion-intercalated thin films between
ion-blocking electrodes, in which interfacial phase separation triggered by an
applied voltage switches the electron-transfer resistance. We develop an
electrochemical phase-field model for simulations of coupled ion-electron
transport and ion-modulated electron-transfer rates and use it to analyze the
MP switching current and time, resistance ratio, and current-voltage response.
The model is able to reproduce the complex cyclic voltammograms of lithium
titanate (LTO) memristors, which cannot be explained by existing models based
on bulk dielectric breakdown. The theory predicts the achievable switching
speeds for multiphase ion-intercalation materials and could be used to guide
the design of high-performance MP-based RS memories.
