Layered perovskite LiEuTiO4 as a 0.8 V lithium intercalation electrode

Abstract

∼1 V lithium intercalation materials are promising anodes for lithium-ion batteries, because such materials give consideration to both the tolerance of lithium plating (e.g., graphite with ∼0.1 V versus Li⁺/Li easily results in lithium plating due to a too low potential) and the energy density of the batteries (e.g., Li₄Ti₅O₁₂ with ∼1.55 V decreases the battery voltage, and thus reduces the energy density). Herein, the layered perovskite compound LiEuTiO₄ with a 0.8 V lithium intercalation/deintercalation potential plateau was successfully synthesized by the ion-exchange reaction with NaEuTiO₄ prepared via a sol–gel method. LiEuTiO₄ can deliver a high capacity of 219.2 mA h g⁻¹ (2nd discharge) at a rate of 100 mA g⁻¹. Even after 500 cycles, the discharge capacity remains at ∼217 mA h g⁻¹ and the Coulombic efficiency is 99.2%. To our knowledge, the cycle stability of LiEuTiO₄ exceeds all previous ∼1 V electrodes. Different from the common lithium intercalation Ti-based electrodes (such as Li₄Ti₅O₁₂) based on the reduction of the Ti⁴⁺ to Ti³⁺, electrochemical lithium intercalation into LiEuTiO₄ leads to the reduction of the Eu³⁺ to Eu²⁺.