Significantly enhanced energy density of magnetite/polypyrrole nanocomposite capacitors at high rates by low magnetic fields

Abstract

One great challenge existing in electrochemical capacitors (ECs) is to achieve high energy densities at high rates. Currently, most research efforts are focused on development of new electrode materials or modification of the microstructure of traditional electrode materials. Herein, we propose a new strategy for significant enhancement of the energy density of ECs at high rates, in which an external magnetic field is exerted. Results indicate that exertion of a magnetic field can increase the energy density of nanocomposite capacitors significantly. In particular, the energy densities of the magnetite/ polypyrrole nanocomposite capacitors containing different content magnetite nanoparticles achieve an increase of more than 10 times at a high current density of 10 A/g, compared to the counterparts without a magnetic field. The possible mechanism is that the magnetic field induces electrolyte ion movement enhancement and charge transfer resistance reduction, which remarkably cause the increase of capacitance and energy density. This work provides an innovative strategy to significantly enhance the rate capabilities of current ECs by a simple physical process rather than chemical process.

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