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

Abstract 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 Na 3 V 2 (PO 4 ) 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 Ti 0 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.