Enabling 20 min fast-charging Ah-level pouch cell by tailoring the electronic structure and ion diffusion in TiNb2O7

Abstract

TiNb2O7 has garnered attention as promising anode materials due to its remarkable cycling durability and rate capability, but its practical applications are currently hampered by the sluggish ion/electron kinetics. Herein, we propose a bimetallic synergistic strategy to enhance ionic and electronic transport kinetics, improving electrochemical performance. DFT calculation results further confirm the synergistic effect of Zn and Nb can increase the lattice parameters, promote Li+ diffusion, and enhance electronic conductivity. Benefiting from this, the Zn0.02Ti0.94Nb2.04O7 exhibits excellent cycling stability (a capacity loss of 0.02 % per cycle over 1000 cycles). An Ah-level pouch cell presents potential application with an impressive cycle lifespan, corresponding to an ultra-high retention ratio of 88.6 % (2.34 Ah) over 2700 cycles. Importantly, in-situ XRD and Nano-CT techniques elucidate the positive impact of the incorporation of Zn and Nb on the fundamental ion transport mechanisms, which is verified by the decreased mechanic effects, and promoted Li+-diffusion kinetics. This work offers a straightforward strategy to significantly improve the rate performance and cycling stability of TiNb2O7, establishing guidelines for fabricating fast-charging batteries with long cycling lifespans.