LAUSR

Hysteresis is a general phenomenon regularly observed in various materials. Usually, hysteretic behavior is an intrinsic property that cannot be circumvented in the non-equilibrium operation of the system. Herein, we show that, at least with regard to the hysteretic behavior of phase-separating battery materials, it is possible to enter (deeply) the hysteretic loop at finite battery currents. This newly observed electric response of the electrode, which is inherent to phase-separating materials, is, for the first time, related to its microscopic origin arising from a (significant) share of the active material residing in an intraparticle phase-separated state. This intriguing observation was further generalized by revealing that a phase-separating material can feature (significantly) different chemical potentials at the same bulk lithiation level and temperature when exposed to the same finite current and external voltage hysteresis. Therefore, the intraparticle phase-separated state significantly affected the DC and AC characteristics of the battery. The experimental evidence for entering the intraparticle phase-separated state is supported by thermodynamic reasoning and advanced modeling. The current findings will help advance the understanding, control, diagnostics, and monitoring of batteries composed of phase-separating materials while also providing pertinent motivation for the enhancement of battery design and performance. This article is protected by copyright. All rights reserved.