Delocalized electronic engineering of TiNb2O7 enables low temperature capability for high-areal-capacity lithium-ion batteries

Abstract High areal capacity and low-temperature ability are critical for lithium-ion batteries (LIBs). However, the practical operation is seriously impeded by the sluggish rates of mass and charge transfer. Herein, the active electronic states of TiNb 2 O 7 material is modulated by dopant and O-vacancies for enhanced low-temperature dynamics. Femtosecond laser-based transient absorption spectroscopy is employed to depict carrier dynamics of TiNb 2 O 7 , which verifies the localized structure polarization accounting for reduced transport overpotential, facilitated electron/ion transport, and improved Li + adsorption. At high-mass loading of 10 mg cm −2 and −30 °C, TNO - x @N microflowers exhibit stable cycling performance with 92.9% capacity retention over 250 cycles at 1 C (1.0-3.0 V, 1 C = 250 mA g −1 ). Even at −40 °C, a competitive areal capacity of 1.32 mAh cm −2 can be achieved. Such a fundamental understanding of the intrinsic structure-function put forward a rational viewpoint for designing high-areal-capacity batteries in cold regions.