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Hybrid nanocomposites comprised of metal oxide nanoparticles and three-dimensional (3D) graphene possess the advantages of metal oxide and graphene, which have generated extensive attention. Here, we fabricate flexible micro-supercapacitors (MSCs) based on hybrid materials of single-walled carbon nanotubes (SWCNT)-bridged laser-induced graphene fibers (LIGF) decorated with manganese dioxide (MnO2) nanoparticles. SWCNT is deposited on the LIGF surface and the space between LIGF, which can bridge LIGF to form more conductive paths and provide more active areas to grow with MnO2 nanoparticles. Profiting from the synergistic effect between conductive SWCNT-bridged LIGF network and the MnO2 nanoparticles with high theoretical capacitance, the obtained flexible MSCs based on LIGF-C4/MnO2 hybrid electrodes deliver an outstanding areal capacitance of 156.94 mF cm−2, which is about 8 times higher than that of LIGF-MnO2 based MSC (20 mF cm−2). Additionally, the LIGF-C4/MnO2 MSCs also exhibit considerable areal energy density of 21.8 μWh cm−2, long-term cycling stability, remarkable modular integration capability, and exceptional mechanical flexibility (with 90.5% capacitance retention after 1200 bending cycles). Therefore, the design of hybrid electrode materials proposed in this work offers a facile and novel method to develop flexible energy storage devices with high performance, suggesting great prospects for applications in future various wearable electronics.

Heteroatoms modification of carbon electrodes is an effective strategy to boost its electrochemical performance. In this work, we demonstrate a one-step and scalable method to manufacture phosphorus-doped (P-doped) 3D porous graphene electrodes from a flexible H3PO4-incorporated polyimide (PI)/Polyvinyl alcohol (PVA) composite film via laser direct writing. Benefiting from the synchronous P-doping and activation caused by H3PO4, the optimal P-doped porous graphene-based micro-supercapacitors (MSCs) present an impressive areal capacitance of 55.5 mF cm−2, good long-term cyclability (with ∼85% capacitance retention after 10000 cycles), superior mechanism flexibility, and outstanding capability of modular integration in series and parallel. Furthermore, density functional theory (DFT) calculations were also carried out to prove that P-doping could enhance the affinity towards electrolyte ions on the carbon surface to improve the electrochemical performance. In particular, due to the highly hydrophilic nature and good film-forming properties of PVA, other dopants can be also well dissolved in the PI/PVA slurry to synthesize a dopants-incorporated PI/PVA composite membrane. Hence, this method offers a convenient and potential route to prepare free-standing heteroatom-doped porous graphene electrodes, which has promising applications for various flexible/wearable electronics.