Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have been considered as attractive alternatives for next-generation battery systems, which have promising application potential due to their earth abundance of potassium and sodium, high capacity and suitable working potential, however, the design and application of bi-functional high-performance anode still remain a great challenge up to date. Bismuth sulfide is suitable as anode owing to its unique laminar structure with relatively large interlayer distance to accommodate larger radius ions, high theoretical capacity and high volumetric capacity etc. In this study, dandelion-like Bi2S3/rGO hierarchical microspheres as anode material for PIBs displayed reversible capacity, and 206.91 mAh·g−1 could be remained after 1,200 cycles at a current density of 100 mA·g−1. When applied as anode materials for SIBs, 300 mAh·g−1 could be retained after 300 cycles at 2 A·g−1 and its initial Coulombic efficiency is as high as 97.43%. Even at high current density of 10 A·g−1, 120.3 mAh·g−1 could be preserved after 3,400 cycles. The Na3V2(PO4)3@rGO//Bi2S3/rGO sodium ion full cells were successfully assembled which displays stable performance after 60 cycles at 100 mA·g−1. The above results demonstrate that Bi2S3/rGO has application potential as high performance bi-functional anode for PIBs and SIBs.
The Caputo and Caputo–Fabrizio derivative are applied to study a second‐grade nanofluid over a vertical plate. A comparative analysis is presented to study the unsteady free convection of a second‐grade nanofluid with a new time–space fractional heat conduction. The governing equations with mixed time–space fractional derivatives are non‐dimensionalized and solved numerically, and a comparison between the Caputo and the Caputo–Fabrizio models is made. It is found that the temperature is higher for the Caputo–Fabrizio fractional model than the Caputo model, but the higher velocity only exists near the vertical plate for the Caputo–Fabrizio model than the Caputo model. Moreover, the velocity for the Caputo model will exceed the Caputo–Fabrizio model as y evolves. 相似文献