Single crystal H-Nb2O5 growing along the [001] crystal direction for ultrafast lithium storage

Abstract

Nb₂O₅ has been deemed as a promising anode candidate for lithium ion batteries due to its fast charge–discharge capability, excellent structural stability, and high safety. Compared with the widely studied orthorhombic Nb₂O₅ (T-Nb₂O₅), the two-phase transition process during the charge/discharge processes in monoclinic Nb₂O₅ (H-Nb₂O₅) results in inadequate cycle stability and rate performance. Herein, the Li storage performance of H-Nb₂O₅ is optimized by constructing single-crystalline structure via a simple and efficient one-pot annealing process. It has been demonstrated that the single-crystalline structure can more effectively maintain the structural integrity as well as suppress the continuous side reactions at the electrode/electrolyte interface in the charge–discharge processes. Besides, the growth along the [001] crystal direction can ensure that Li ions can penetrate directly into the center from the surface in the single-crystalline H-Nb₂O₅, resulting in a significantly improved Li⁺ diffusion kinetics. As a result, the single-crystalline H-Nb₂O₅ exhibits ultrahigh rate performance (119.8 mA h g⁻¹ at 100C) and long cycle durability with a high capacity of 115.6 mA h g⁻¹ at 25C for 3000 cycles. Besides, single-crystalline H-Nb₂O₅ can deliver a remarkable areal capacity of 2.96 mA h cm⁻² at a high mass loading of 12 mg cm⁻². The Li-ion capacitor paired with commercial activated carbon cathode also exhibits an exceptional energy density of 48.4 W h kg⁻¹ at a high power density of 5.45 kW kg⁻¹. This work will further tap the commercial potential of the single-crystalline H-Nb₂O₅ for fast lithium storage devices.