Relaxation of the Interface Resistance between Solid Electrolyte and 5 V-Class Positive Electrode.

Nakayama, Ryo; Nishio, Kazunori; Imazeki, Daisuke; Nakamura, Naoto; Shimizu, Ryota; Hitosugi, Taro · Nano Lett · 2021

basic_science · Level V

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Abstract

Solid-state Li batteries using 5 V-class positive electrode materials display a higher energy density. However, the high resistance at the interface of the electrolyte and positive electrode (interface resistance, <i>R</i><sub>i</sub>) hinders their practical applications. Here, we report the relaxation of <i>R</i><sub>i</sub> between a solid electrolyte (Li<sub>3</sub>PO<sub>4</sub>) and a 5 V-class electrode (LiCo<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub>). Although <i>R</i><sub>i</sub> is small at the Mn<sup>3+/4+</sup> redox voltage of 4.0 V vs Li/Li<sup>+</sup> (11 Ω cm<sup>2</sup>), it rapidly increases by more than 2 orders of magnitude as the voltage increases above the Co<sup>3+/4+</sup> redox voltage of 5.2 V vs Li/Li<sup>+</sup>. After the applied voltage is reduced to 4.0 V vs Li/Li<sup>+</sup>, <i>R</i><sub>i</sub> decays to the original value after 3 h. The relaxation of <i>R</i><sub>i</sub> after exposure to high voltages suggests that the increase in <i>R</i><sub>i</sub> above 5 V vs Li/Li<sup>+</sup> is attributable to the formation of an interfacial layer at the LPO/LCMO interface.