Interface and Defect Engineered Titanium-Base Oxide Heterostructures Synchronizing High-Rate and Ultrastable Sodium Storage

Sodium-ion batteries are a promising large-scale electrochemical energy storage system because of their excellent cost advantage compared with lithium-ion batteries. However, the lack of high safety, low cost, and long service life anode materials hinder its actual development. Here, a sodium titanate/titanium dioxide/C (C-NTC) heterostructure composite is reported with oxygen vacancies (OVs) that delivers a high specific capacity of 92.6 mAh g^-1 at 5 A g^-1 after 35 000 cycles (100% capacity retention) and excellent rate performance of 54 mAh g^-1 at 20 A g^-1 when tested in combination with a Na-metal anode. Moreover, sodium-ion full batteries assembled with C-NTC as the anode and Na₃V₂(PO₄)₃@C-BN as the cathode demonstrates a high specific capacity after 5500 cycles. Electrochemical kinetic tests and density functional theory measurements confirm that the synergistic effect of heterostructure and OVs accelerate the ion/electron transfer kinetics, the stable frame structure, and solid electrolyte interphase layer ensuring the long cycle life. Ex-situ X-ray photon spectroscopy reveals that the generation of Ti⁰ by disproportionation reactions may be responsible for the degradation of Ti-based oxide performance, which provides unique insight and guidance for the design of titanium-based electrodes with ultra-long cycle life.