Critical Role of Ti<sup>4+</sup> in Stabilizing High‐Voltage Redox Reactions in Li‐Rich Layered Material
Moses Azong Cho, Seok Hyun Song, Seokjae Hong, Kyoung Sun Kim, Maxim Avdeev, Jonggyu Yoo, Kyung‐Tae Ko, Jihyun Hong, Jongsoon Kim, Seongsu Lee, Hyungsub Kim
Abstract
Abstract Li‐rich layered oxide materials are considered promising candidates for high‐capacity cathodes for battery applications and improving the reversibility of the anionic redox reaction is the key to exploiting the full capacity of these materials. However, permanent structural change of the electrode occurring upon electrochemical cycling results in capacity and voltage decay. In view of these factors, Ti 4+ ‐substituted Li 2 IrO 3 (Li 2 Ir 0.75 Ti 0.25 O 3 ) is synthesized, which undergoes an oxygen redox reaction with suppressed voltage decay, yielding improved electrochemical performance and good capacity retention. It is shown that the increased bond covalency upon Ti 4+ substitution results in structural stability, tuning the phase stability from O3 to O1′ upon de‐lithiation during charging compared with O3 to T3 and O1 for pristine Li 2 IrO 3 , thereby facilitating the oxidation of oxygen. This work unravels the role of Ti 4+ in stabilizing the cathode framework, providing insight for a fundamental design approach for advanced Li‐rich layered oxide battery materials.