Unraveling the Nature of Anomalously Fast Energy Storage in T-Nb₂O₅

Abstract

While T-NbO has been frequently reported to display an exceptionally fast rate of Li-ion storage (similar to a capacitor), the detailed mechanism of the energy storage process is yet to be unraveled. Here we report our findings in probing the nature of the ultrafast Li-ion storage in T-NbO using both experimental and computational approaches. Experimentally, we used in operando Raman spectroscopy performed on a well-designed model cell to systematically characterize the dynamic evolution of vibrational band groups of T-NbO upon insertion and extraction of Li ions during repeated cycling. Theoretically, our model shows that Li ions are located at the loosely packed 4g atomic layers and prefer to form bridging coordination with the oxygens in the densely packed 4h atomic layers. The atomic arrangement of T-NbO determines the unique Li-ion diffusion path topologies, which allow direct Li-ion transport between bridging sites with very low steric hindrance. The proposed model was validated by computational and experimental vibrational analyses. A comprehensive comparison between T-NbO and other important intercalation-type Li-ion battery materials reveals the key structural features that lead to the exceptionally fast kinetics of T-NbO and the cruciality of atomic arrangements for designing a new generation of Li-ion conduction and storage materials.

Novel Sub‐5 nm Layered Niobium Phosphate Nanosheets for High‐Voltage, Cation‐Intercalation Typed Electrochemical Energy Storage in Wearable Pseudocapacitors

“…[20,21] 2) The enhanced ionicity of NbO bond: as theoretically predicted by the previous work, the enhanced ionicity of NbO bond with the existence of [PO 4 ] 3− group in the present 2NbOPO 4 ·H 3 PO 4 ·H 2 O crystal can efficiently produce a high operating voltage window up to 1.0 V. [16][17][18][19] 3) The outstanding structure stability of the layered 2NbOPO 4 ·H 3 PO 4 ·H 2 O ensure the long-term charge/ discharge cycling stability. However, our NPene sheets can greatly utilizes the bulk of electrode material in charge storage through fast intercalation of cations (H + or Li + ), resulting in a high specific capacitance and energy density.…”

“…[15] More importantly, it has been theoretically predicted a much higher potential (≈1.0 V in aqueous electrolyte) in layered phosphates than in most of the traditional pseudocapacitive materials due to the enhanced iconicity of metaloxygen bond with the existence of [PO 4 ] 3− group. [20,21] Especially, the pseudocapacitance occurs in the T-Nb 2 O 5 bulk rather than the surface or near-surface of the electrode, resulting high specific capacitances and energy density. A unique Li + -intercalation pseudocapacitance has been found in T-Nb 2 O 5 (40 µm thick) electrode, which holds a great perspective on the development of electrochemical electrodes.…”

Exploiting the Condensation Reactions of Acetophenone to Engineer Carbon‐Encapsulated Nb2O5 Nanocrystals for High‐Performance Li and Na Energy Storage Systems

“…The carbon content of the composites was varied between 0 and 16 wt% by changing the Nb 2 O 5 /TPB ratio, which was achieved by removing the desired amount of TPB with acetone. [48][49][50][51][52][53] They are dominated by the intense band (at 693 cm −1 ) arising from the symmetrical TO stretch of NbO bonds in the low distorted corner-or edgesharing bipyramidal units of the oxide lattice; [48,50,52] weaker bands are further detected at 122, 227, 308, 465, and 809 cm −1 . Small carbonencapsulated Nb 2 O 5 NCs (NP-X where X is the carbon content samples) were synthesized by reaction of NbCl 5 with acetophenone ( Figure 1c).…”

Niobium‐Based Oxides Toward Advanced Electrochemical Energy Storage: Recent Advances and Challenges

“…It is found that the Nb‐ions are surrounded by either six or seven O‐ions, which constitutes the edge/corner‐sharing distorted NbO 6 and NbO 7 polyhedra . According to the atomic arrangement of T‐Nb 2 O 5 , its crystal structure can be regarded as two alternating atomic layers, including the loosely packed 4g layer and the denser 4h layer ( Figure a) . Owing to the capacious atomic accommodation space, the 4g layer provides preferential storage and transport sites for Li‐ions.…”

“…Moreover, the calculated energy migration barriers for Li‐ions through Path A or Path B are ranged from 0.25 to 0.33 eV, further confirming the structural merit of T‐Nb 2 O 5 for superior Li‐ion transport character. These two Li‐ion diffusion paths are both within the 4g layer, resulting in the formation of a quasi‐2D network for Li‐ion transport …”