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.

The graphene-based microsupercapacitors (MSCs) suffer from graphene aggregation issue in electrodes. It reduces the electrolyte ions transportation in the electrodes to degrade the charge storage ability of MSCs, hampering their practical application. Increasing the electrolyte ions transportation in the electrodes can boost the charge storage ability of MSCs. Herein, we design and experimentally realize pillar array structure of graphene electrodes for MSCs by direct ink writing technology. The graphene electrodes with pillar array structure increase the contact area with electrolyte and short the electrolyte ions transport path, facilitating electrolyte ions transport in electrodes. The MSCs exhibit high areal capacitance of 25.67 mF·cm^–2, high areal energy density of 20.54 μWh·cm^–2, and high power density of 1.45 mW·cm^–2. One single MSCs can power timer for 10 min and pressure sensor more than 160 min, showing high practical application possibility. This work provides a new avenue for developing high performance MSCs.

The electrochemical performance of microsupercapacitors with graphene electrodes is reduced by the issue of graphene sheets aggregation, which limits electrolyte ions penetration into electrode. Increasing the space between graphene sheets in electrodes facilitates the electrolyte ions penetration, but sacrifices its electronic conductivity which also influences the charge storage ability. The challenging task is to improve the electrodes’ electronic conductivity and ionic diffusion simultaneously, boosting the device’s electrochemical performance. Herein, we experimentally realize the enhancement of both electronic conductivity and ionic diffusion from 2D graphene nanoribbons assisted graphene electrode with porous layer-upon-layer structure, which is tailored by graphene nanoribbons and self-sacrificial templates ethyl cellulose. The designed electrode-based device delivers a high areal capacitance of 71 mF cm⁻² and areal energy density of 9.83 μWh cm⁻², promising rate performance, outstanding cycling stability with 97% capacitance retention after 20 000 cycles, and good mechanical properties. The strategy paves the way for fabricating high-performance graphene-based MSCs.