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

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.

Automated summary

In this study, the Li storage performance of monoclinic Nb2O5 (H-Nb2O5) was optimized by constructing a single-crystalline structure via a simple and efficient one-pot annealing process. The single-crystalline structure effectively maintained the material integrity and suppressed side reactions, while growth along the [001] crystal direction improved Li+ diffusion kinetics. The resulting single-crystalline H-Nb2O5 exhibited ultrahigh rate performance and long cycle durability, as well as remarkable areal capacity and energy density when paired with a commercial activated carbon cathode.