Carbon Quantum Dot-Coated VSe₂ Nanosheets as Anodes for High-Performance Potassium-Ion Batteries

Abstract

Potassium-ion batteries (PIBs) are of great importance in energy storage due to their natural abundance, low cost, and high operating potential compared to lithium and sodium. Herein, we first propose carbon quantum dot coating on VSe 2 nanosheets (VSe 2 @CQDs) as anodes for PIBs with the solvothermal and annealing methods. In the composite, carbon quantum dots are embedded in VSe 2 nanosheets, which inhibit the aggregation and volume expansion of the VSe 2 nanosheets during cycling, resulting in stabilizing the structure and long cycling stability. Besides, with abundant edge positions and surface oxygencontaining functional groups, small-sized carbon quantum dots have strong absorption of K + , enhancing the capacity of the composite. As a result, for PIBs, the composite exhibits a superior reversible capacity of 362 mA h g −1 after 200 cycles at 100 mA g −1 with a high capacity retention of 76.7%, high rate capacity (255 mA h g −1 at 1000 mA g −1 ), and a long-term cycling life of 162 mA h g −1 after 3000 cycles at 500 mA g −1 with a high coulombic efficiency (above 99%). The VSe 2 @CQD composite shows the best performances reported to date for long-term cycling stability, excellent reversible capacity, and rate capacity in TMD-based PIB anodic materials. The excellent performance and simple synthesis indicate the promising VSe 2 @CQD composite as a potential anode material for PIBs.

Metal Selenides Find Plenty of Space in Architecting Advanced Sodium/Potassium Ion Batteries

“…Hybridizing with carbonaceous materials has been deemed as one of the sufficient conceptions to alleviate such plague. [47][48][49] Benefited from the inherent conductivity of VSe 2 , the improved conductivity and structural stability protection offered by the polypyrrole layer, VSe 2 @PPy nanoplates delivered an increased charge transfer rate and cushioned volumetric expansion. Consequently, it showed a satisfactory rate capability of 260 mAh g −1 at 10 A g −1 for SIBs and 148.6 mAh g −1 at 5 A g −1 for PIBs.…”

One-step Solid-State Synthesis of V1.13Se2/V2O3 Heterostructure as a High Pseudocapacitance Anode for Fast-Charging Sodium-Ion Batteries

“…19 This instability results in the agglomeration of VSe 2 into bulk materials. 20 Consequently, during the Na + insertion/extraction processes, VSe 2 experiences substantial volume fluctuations, leading to electrode fragmentation and compromised cycling stability. 21 V 1.13 Se 2 , a nonstoichiometric compound, can be considered a self-intercalating layered material, where excess vanadium is systematically situated amid the continuous Se−V−Se interlayers.…”

“…However, the lower d-orbital energy level of selenium leads to the reduction of V 4+ and the oxidation of Se 2– , causing the inherent instability of VSe 2 . This instability results in the agglomeration of VSe 2 into bulk materials . Consequently, during the Na + insertion/extraction processes, VSe 2 experiences substantial volume fluctuations, leading to electrode fragmentation and compromised cycling stability …”