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.