Revealing the Rapid Electrocatalytic Behavior of Ultrafine Amorphous Defective Nb₂O_5–x Nanocluster toward Superior Li–S Performance

Abstract

The notorious shuttling behaviors and sluggish conversion kinetics of the intermediate lithium polysulfides (LPS) are hindering the practical application of lithium sulfur (Li−S) batteries. Herein, an ultrafine, amorphous, and oxygendeficient niobium pentoxide nanocluster embedded in microporous carbon nanospheres (A-Nb 2 O 5−x @MCS) was developed as a multifunctional sulfur immobilizer and promoter toward superior shuttle inhibition and conversion catalyzation of LPS. The A-Nb 2 O 5−x nanocluster implanted framework uniformizes sulfur distribution, exposes vast active interfaces, and offers a reduced ion/electron transportation pathway for expedited redox reaction. Moreover, the low crystallinity feature of A-Nb 2 O 5−x manipulates the LPS chemical affinity, while the defect chemistry enhances the intrinsic conductivity and catalytic activity for rapid electrochemical conversions. Attributed to these superiorities, A-Nb 2 O 5−x @MCS delivers good Li−S battery performances, that is, high areal capacity of 6.62 mAh cm −2 under high sulfur loading and low electrolyte/sulfur ratio, superb rate capability, and cyclability over 1200 cycles with an ultralow capacity fading rate of 0.024% per cycle. This work provides a synergistic regulation on crystallinity and oxygen deficiency toward rapid and durable sulfur electrochemistry, holding a great promise in developing practically viable Li−S batteries and enlightening material engineering in related energy storage and conversion areas.

3D Printing of a V8C7–VO2 Bifunctional Scaffold as an Effective Polysulfide Immobilizer and Lithium Stabilizer for Li–S Batteries

“…It can be observed that both V 8 C 7 and V 8 C 7 -VO 2 display two pairs of redox peaks (Peak i, ii, iii, and iv), indicative of facile conversion between Li 2 S n and Li 2 S. [45] Moreover, the V 8 C 7 -VO 2 cell harvests smaller polarization and higher current intensity in comparison with the bare V 8 C 7 counterpart, implying promoted electrochemical reversibility and conversion efficiency of polysulfides. [46] This trend can also be demonstrated by the enhanced current response in the CV profile at an increased scan rate of 50 mV s −1 (Figure 3c).…”

Engineering the Conductive Network of Metal Oxide‐Based Sulfur Cathode toward Efficient and Longevous Lithium–Sulfur Batteries

“…In addition, the O1 peaks of Nb 2 O 5−x and Nb 2 O 5-x /CNTs shift up to a higher binding energy region, further confirming the oxygendeficient character (Figure 2d). [12] Furthermore, the oxygen deficiency was determined by electron paramagnetic resonance (EPR) measurement. As presented in Figure 2e, the as-prepared Nb 2 O 5−x and Nb 2 O 5−x / CNTs exhibit strong resonance signal at a g-value of 2.003, while minimum resonance can be observed for Nb 2 O 5 .…”

“…[7][8][9] Meanwhile, the strong solvation of the intermediate lithium polysulfides in ether solvents renders their high solubility and mobility in electrolyte as well as the resultant notorious shuttle effect, which gives rise to serious sulfur loss and poor electrochemical reversibility. [10][11][12][13] To address these shortcomings, various approaches have been proposed including hybrid cathode, [14][15][16] separator modification, [17][18][19] electrolyte optimization, [20,21] anode protection, [22,23] etc. Studies have shown that the rational design of sulfur electrode is of particular significance for improving the Li-S battery electrochemistry.…”

Optimization Design and Application of Niobium‐Based Materials in Electrochemical Energy Storage

“…Vacancy in niobium-based materials further enhanced the chemical bonding with LPS and reduced the activation energy of sulfur redox reaction. Chen and co-workers [76] implanted ultrafine Nb 2 O 5Àx nanocluster with amorphous structure and rich oxygen-vacancy into the micropores of carbon nanosphere to form strawberrylike nanostructure, improving the performance of Li-S. Also, amorphous and defective structures elevated the affinity of Nb 2 O 5 to LPS, and oxygen vacancy further increased the catalytic activity of LPS conversion. Furthermore, nanocluster embedded composite structure can be used as nano-reactor to limit sulfur uniform distribution, improve sulfur utilization, provide conductive framework to accelerate electron/ion transfer and rich active interface for LPS restriction and conversion, thereby improving electrochemical performance ( Figure 13).…”