Electrolytes play a key role in determining the electrochemical performance, safety, and lifespan of potassium-based batteries, making their selection and optimization a critical area of research. This study systematically investigates the effects of two major potassium-based battery electrolytes, potassium hexafluorophosphate (KPF₆) and potassium difluorosulfonimide (KFSI) in ethylene carbonate/diethyl carbonate (EC/DEC) solvents, on battery performance, solid electrolyte interphase (SEI) stability, aluminum (Al) current collector corrosion behavior, electrochemical stability window, and dendrite growth issue. Experimental results reveal that KFSI electrolyte significantly outperforms KPF₆ in terms of cycling stability, rate capability, and Coulombic efficiency (CE), primarily due to the formation of a high-quality SEI on electrode surface. Through X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses, we construct the SEI structure for both electrolytes, and find that the SEI formed by KFSI is more uniform and stable. Additionally, KPF₆ exhibits weaker corrosivity towards the Al current collector compared to KFSI due to the formation of an AlF₃ layer with higher oxidation stability on Al surface. Furthermore, in-situ optical microscopy observations indicate that the dendrite growth in KFSI electrolyte is more uniform, preventing the aggregates. These findings provide essential experimental evidence and theoretical support for optimizing the electrolyte in potassium-based batteries.

The effect of crystallinity degree of MoSe₂ on the potassium ions storage performance in potassium-ion batteries (PIBs) has been largely overlooked in the energy communities. In this study, we experimentally realize MoSe₂ grown on graphene nanoribbons (MoSe₂-GNR) with tunable crystallinity by tailoring the thermal annealing temperature, and further investigate the effect of crystallinity degree in MoSe₂-GNR on the potassium ions storage performance. The spectral, electrochemical, and microscopy experiments indicate that high-temperature thermal annealing results in a high crystallinity degree of MoSe₂-GNR with decreased interlayer spacing of (002). The MoSe₂-GNR with high crystallinity degree exhibits a high capacity, but suffers from reduced cycling stability. What is more, the in-situ X-ray powder diffractometer (in-situ XRD) and in-situ Raman experiments reveal the phase transition in MoSe₂ triggered by potassium ions insertion/extraction during the potassium ions storage. The work sheds light on the development of MoSe₂-based anode materials for PIBs.