Stabilizing effects of atomic Ti doping on high-voltage high-nickel layered oxide cathode for lithium-ion rechargeable batteries

High-voltage high-nickel lithium layered oxide cathodes show great application prospects to meet the ever-increasing demand for further improvement of the energy density of rechargeable lithium-ion batteries (LIBs) mainly due to their high output capacity. However, severe bulk structural degradation and undesired electrode–electrolyte interface reactions seriously endanger the cycle life and safety of the battery. Here, 2 mol% Ti atom is used as modified material doping into LiNi_0.6Co_0.2Mn_0.2O₂ (NCM) to reform LiNi_0.6Co_0.2Mn_0.18Ti_0.02O₂ (NCM-Ti) and address the long-standing inherent problem. At a high cut-off voltage of 4.5 V, NCM-Ti delivers a higher capacity retention ratio (91.8% vs. 82.9%) after 150 cycles and a superior rate capacity (118 vs. 105 mAh·g⁻¹) at the high current density of 10 C than the pristine NCM. The designed high-voltage full battery with graphite as anode and NCM-Ti as cathode also exhibits high energy density (240 Wh·kg⁻¹) and excellent electrochemical performance. The superior electrochemical behavior can be attributed to the improved stability of the bulk structure and the electrode–electrolyte interface owing to the strong Ti–O bond and no unpaired electrons. The in-situ X-ray diffraction analysis demonstrates that Ti-doping inhibits the undesired H2-H3 phase transition, minimizing the mechanical degradation. The ex-situ TEM and X-ray photoelectron spectroscopy reveal that Ti-doping suppresses the release of interfacial oxygen, reducing undesired interfacial reactions. This work provides a valuable strategic guideline for the application of high-voltage high-nickel cathodes in LIBs.