Flexible Supercapacitor-Type Rectifier-free Self-Charging Power Unit Based on a Multifunctional Polyvinylidene Fluoride-ZnO-rGO Piezoelectric Matrix

The development of an effective mechanical to electrical energy conversion device and its functional integration with an energy storage device for self-powered portable gadgets are cutting-edge research fields. However, the generated power and the mechanical stability of these integrated devices are still not efficient to power up portable electronics. We fabricated a rectifier-free piezoelectric nanogenerator (NG) integrated with a supercapacitor (SC). A multifunctional composite matrix was prepared by the incorporation of ultrathin (<10 nm) ZnO nanoflakes and reduced graphene oxide in polyvinylidene fluoride to enhance the piezoelectric output characteristics and mechanical stability of the device while minimizing the additional energy losses during the integration. The as-fabricated SC-based power unit through the energy conversion and storage processes showed a remarkable self-charging performance. We obtained the maximum output voltage, current density, and power density of about 44 V, 1000 nA cm^-2, and 193.6 μW cm^-2 under the applied mechanical force of 10 N, respectively. The self-charging behavior of the device showed that it can store 1.5 × 10^-3 mC within 100 s without resorting to a rectifier. We obtained the total energy density of about 10.34 mW h kg^-1 under palm impact. Our results present a step forward in the development of the NG and SC-based flexible and self-charging devices.

MnO2 encapsulated electrospun TiO2 nanofibers as electrodes for asymmetric supercapacitors

We report a facile technique to fabricate manganese dioxide (MnO₂) encapsulated titanium dioxide (TiO₂) nanofiber heterostructure for its use as an electrode material in aqueous electrolyte based asymmetric supercapacitor (SC). MnO₂ coated TiO₂ nanofibers, prepared by electrospinning and post-hydrothermal process exhibited superior electrochemical properties in aqueous Na₂SO₄ electrolyte. The MnO₂ shell with average thickness of approximately 10 nm contributed to the high electrochemical performance for charge storage by redox reaction and intercalation mechanisms, while the anatase phase TiO₂ core provided an easy pathway for electronic transport with additional electrochemical stability over thousands of charge-discharge cycles. An asymmetric SC designed from the MnO₂-TiO₂ nanofiber electrode and single walled carbon nanotubes electrode showed high operating voltage window (2.2 V) with maximum gravimetric capacitance of 111.5 F g^-1.

Ternary TiO2/SiOx@C nanocomposite derived from a novel titanium-silicon MOF for high-capacity and stable lithium storage

A novel titanium-silicon MOF precursor was first designed and constructed via a facile solvothermal process. After subsequent pyrolysis, the derived ternary TiO₂/SiO_x@C nanocomposite exhibited superior lithium storage performances, which was attributed to their all-in-one architecture of synergistic components, including stable-cycling nanostructured TiO₂, high-capacity SiO_x and high-conductivity carbon matrix.

Synthesis of mesoporous TiO2@C@MnO2 multi-shelled hollow nanospheres with high rate capability and stability for lithium-ion batteries

Mesoporous TiO₂@C@MnO₂ multi-shelled hollow nanospheres (denoted as TiO₂@C@MnO₂ multi-shelled HNSs) prepared by a layer-by-layer deposition growth process exhibit high rate capability and stability.

Facile preparation of a composite of TiO2 nanosheets and polyaniline and its gas sensing properties

Facilely prepared composite of TiO₂ nanosheets and polyaniline as a highly sensitive NH₃ sensor by a combination of electrospinning and hydrothermal synthesis.

A double core–shell modification of bulk TiO2 microspheres into porous N-doped-graphene carbon nanoflakes/N-doped TiO2 microspheres for lithium-ion battery anodes

Nitrogen (N) doping and double core–shell modification of TiO₂ for lithium battery application.

Facile synthesis of porous Fe2TiO5 microparticulates serving as anode material with enhanced electrochemical performances

Porous Fe₂TiO₅ microparticulates exhibited superior electrochemical performances as LIBs anode material due to the synergistic effect of TiO₂ and Fe₂O₃.

Fabrication of coral like carbon black/MnO2nano composites from commercial carbon black and their application in supercapacitors

A carbon black/MnO₂nano-composite (CB/MnO₂) of coral-like architecture was synthesized from a commercially available conductive carbon black (CB) using anin situmethod.