Critical Role of Ti⁴⁺ in Stabilizing High-Voltage Redox Reactions in Li-Rich Layered Material

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, Ti⁴⁺ -substituted Li₂ IrO₃ (Li₂ Ir_0.75 Ti_0.25 O₃ ) 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 Ti⁴⁺ 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 Li₂ IrO₃ , thereby facilitating the oxidation of oxygen. This work unravels the role of Ti⁴⁺ in stabilizing the cathode framework, providing insight for a fundamental design approach for advanced Li-rich layered oxide battery materials.