Laser-induced zero-, one-, and two-dimensional all carbon composites for ultra high-rate flexible supercapacitor electrodes

In this work, we report a flexible, all‑carbon ternary nanocomposite electrode for ultra-high-rate flexible supercapacitors, synthesized through a rapid, binder-free, two-stage CO₂ laser irradiation protocol that simultaneously reduces graphene oxide and graphitizes carbon nanodots on a flexible stainless-steel substrate. The composite integrates three carbon allotropes of complementary dimensionality 0D carbon nanodots (CNDs), 1D carbon nanotubes (CNTs), and 2D reduced graphene oxide (rGO) into a synergistic architecture in which the CNTs act as a conductive scaffold preventing rGO restacking and absorbing mechanical strain, while the CNDs bridge the interfacial gaps between the 1D and 2D phases and serve as a structural “softener” against bending stress. Through a systematic comparative study spanning five compositions and an exceptionally broad scan-rate window (20–10,000 mV s⁻¹), we show that the optimized rGO/CNT/CND10 electrode retains ∼40% of its low-rate capacitance at 10,000 mV s⁻¹ relative to only 4–6% for pristine rGO and ∼ 13% for the binary rGO/CNT at a scan rate at which most reported carbon-based flexible electrodes lose their capacitive signature entirely. The optimized electrode also exhibits a characteristic RC time constant of τ ≈ 11 ms (vs. ∼35 ms for pristine rGO), and maintains its capacitive response, minimum phase angle, and charge-transfer resistance under severe mechanical deformation. The electrode further retains ∼80% of its capacitance over 1000 charge–discharge cycles and preserves its voltametric response after 1000 bending cycles. The compositional control of the 0D/1D/2D carbon architecture thus provides a clear design route to flexible electrodes that retain capacitive function under both ultra-high scan rates and severe mechanical deformation.