A stable fast-charging TiNb2O7 anode material enabled by strong Ta-O bonds

TiNb 2 O 7 (TNO) is regarded as a potential fast-charging anode for lithium-ion batteries due to its fast reversible phase transition and safe working potential, but it suffers from unsatisfactory electronic conductivity, sluggish ion kinetics, and poor structural stability under high rates. Herein, tantalum (Ta) with strong Ta–O bonds is doped into TNO to enhance its fast-charging property and structural stability. Proper amount of Ta doping not only increases the interlayer spacing for fast Li + transport, but also improves the electrical conductivity, being successfully proved by experimental analyses. Density functional theory (DFT) calculation verifies that the lattice distortion induced by the incorporation of strong Ta-O bonds can effectively strengthen the structural stability. Notably, in situ X-ray diffraction (XRD) technology reveals that Ta doping relieves volumetric strain during lithiation and de-lithiation. Thus, the optimized Ta 0.1 -TNO sample owns impressive long-term cycling stability even at a high current density of 10C, which delivers a high-capacity retention of 85.12% (a capacity decay of less than 0.01% per cycle) after 1500 cycles. This work provides a fast-charging anode material with superior structural stability for lithium-ion batteries. Graphical abstract