Single-crystal TiNb2O7 materials via sustainable synthesis for fast-charging lithium-ion battery anodes

Abstract

TiNb 2 O 7 (TNO) has emerged as a promising fast-charging anode for lithium-ion batteries (LIBs). However, research on TNO anode materials has been mostly restricted to synthesis of polycrystalline with limited associated mechanistic studies. Herein, we report a novel scalable aqueous synthesis method yielding sub-micron size single-crystal TNO particles following calcination that enables fast-charging anode fabrication. The sustainable co-precipitation process yields amorphous intermediate hydroxides which upon thermal conversion induced crystallization form single crystals. The obtained TNO monocrystalline anode material under 900 °C calcination (TNO-900C) delivers a high gravimetric capacity (279 mAh/g at 1st cycle) and a high volumetric capacity (351.7 mAh/cm 3 at the initial cycle) at 0.5C rate. Additionally, the TNO anode delivers a remarkable capacity of 223 mAh/g at 5C and a high retention of 81.4 % after 200 cycles. In addition, TNO-900C illustrates outstanding fast-charging performance with a reversible capacity of 200 mAh/g at 10C. The intercalation mechanism and diffusion behavior of the monocrystalline TNO anodes are elucidated by electrochemical kinetic analysis (GITT, CV, and EIS). The remarkable fast charging Li-ion storage performance can be attributed to a high Li + diffusion coefficient (1.37 × 10 −13 cm 2 /s), low polarization, and high structural stability. • Single-crystal TiNb 2 O 7 materials exhibiting remarkable fast-charging performance • Novel synthesis method featuring hydrolytic precipitation and calcination for sustainable production • High Li + diffusion kinetics and redox intercalation mechanism revealed by electrochemical characterization

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