The development of potassium‐ion battery (PIB) electrode materials is critical for promoting their use in next‐generation energy storage systems. Although metal–organic frameworks (MOFs) are appealing electrode materials, their performance in PIBs remains unsatisfactory. The low K+ adsorption energy (ΔEa) on the saturated coordination of MOFs can explain the limited capacity. Herein, MXene‐derived MOF nodes (NMD‐MOF) are unlocked and used as anodes in PIB. The NMD‐MOF anode exhibits substantially increased capacity (250 mA h g−1 at 0.05 A g−1), as well as good rate‐performance and excellent capacity retention. Density functional theory calculations reveal that the ΔEa at unlocked node sites is significantly higher than at intact node sites of the pristine MOF. Furthermore, the NMD‐MOF anode and homologous MXene‐derived K+‐intercalated vanadium oxide (MD‐KVO) cathode combine to assemble a PIB, which delivers an encouraging capacity of 63 mA h g−1 at 50 mA g−1 and high energy (143 Wh kg−1) and power density (440 W kg−1). The fabrication of MXene‐derived electrode materials and the unlocking node strategy for binding site activation may spur further research into highly active electrode materials for energy storage devices.
In this paper, the magnetization dynamics of bilayer structured nano-pillars containing a fixed layer with perpendicular magnetic anisotropy (PMA) and a free layer with in-plane magnetic anisotropy (IMA) are studied using the micro-magnetic simulation method. Unlike typical sandwich-structured spin-torque nano-pillar oscillators (STNOs), the proposed structure does not contain any nonmagnetic spacer layer. It is found that a stable oscillation with a significant amplitude can be established fast after driving out the vortex core by an in-plane magnetic pulse field. The oscillation frequency and amplitude can be easily manipulated by adjusting the side-length of the nanopillar, the thickness and saturation magnetization of the IMA layer, and an applied magnetic field along z axis. In an array with an adequate inter-pillar distance, the mutual interaction between the nano-pillars will lead the oscillations to be phase-locked, resulting in a considerable enhancement of total amplitude. As it is easy to fabricate these kinds of bi-layer nano-pillars and assemble them in arrays, they may have widespread applications in STNOs.
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