Bifunctional polyoxometalate clusters-modified single-walled carbon nanotubes for high-energy–density micro-supercapacitors

The rapid advancement of wearable electronics has pushed the urgent demand for flexible power sources with high energy density and fast integrations. Herein, we created high-energy–density micro-supercapacitors (MSCs) based on phosphomolybdic acid (PMo₁₂) clusters anchored single-walled carbon nanotubes (SWCNTs) via the electrostatic assembly. The SWCNT microelectrodes for MSCs were directly fabricated by an aerosol process without any solvent-based treatment. The PMo₁₂ clusters were found to not only increase the electrical conductivity of SWCNT thin-film electrodes, but also offer significant pseudo-capacitance of MSCs. The MSCs based on PMo₁₂-modified SWCNTs demonstrated an areal capacitance of 10.2 mF cm⁻² when scanned at 5 mV s⁻¹, coupled with a notable energy density of 0.71 μWh cm⁻² at a power density of 7 μW cm⁻², being much higher than the one without PMo₁₂ modification. The density functional theory simulation further reveals the enhancement of electrical conductivity and areal capacitance induced by PMo₁₂ modifications. Moreover, our strategy is highly scalable for integrations via series or parallel connections, which could deliver higher voltage output or areal capacitance. This work demonstrates great potential for high-performance MSCs toward wearable electronics applications.