A perpendicular micro-hole array for efficient ion transport in a thick, dense MoS2-based capacitive electrode

Two-dimensional (2D) nanosheets with a high electrochemical capacitance, density, and electrical conductivity are promising for assembling thick and dense films for supercapacitors with a high volumetric energy density. However, 2D nanosheet-based films with cascading nanochannel networks are not ideal for efficient ion transport due to the tortuous pathways. We used a micro-stamping method to create a perpendicular micro-hole array in a thick, dense MoS2-based electrode without lowering its density. Our nuclear magnetic resonance measurement and computational simulations reveal that the micro-hole array can serve as ion reservoirs and provide shortcuts in the cascading nanochannel network, greatly improving the ion accessibility to MoS2-based electrodes in both the adsorption and charging processes. A MoS2-based film electrode with 2-3 times the density of a conventional carbon electrode, shows almost thickness independent capacitance performance with a mass loading up to 18.6 mg cm−2. The electrode has a volumetric capacitance of 469.5 F cm−3 and the assembled device a volumetric energy density of 80.5 Wh L−1 in an ionic liquid electrolyte. This micro-stamping strategy is easy to scale up and may pave the way for the development of 2D materials-based compact energy storage systems.