Unique Core–Shell Nanorod Arrays with Polyaniline Deposited into Mesoporous NiCo₂O₄ Support for High-Performance Supercapacitor Electrodes

Abstract

Polyaniline (PANI), one of the most attractive conducting polymers for supercapacitors, demonstrates a great potential as high performance pseudocapacitor materials. However, the poor cycle life owing to structural instability remains as the major hurdle for its practical application; hence, making the structure-to-performance design on the PANI-based supercapacitors is highly desirable. In this work, unique core-shell NiCo2O4@PANI nanorod arrays (NRAs) are rationally designed and employed as the electrode material for supercapacitors. With highly porous NiCo2O4 as the conductive core and strain buffer support and nanoscale PANI layer as the electrochemically active component, such a heterostructure achieves favorably high capacitance while maintaining good cycling stability and rate capability. By adopting the optimally uniform and intimate coating of PANI, the fabricated electrode exhibits a high specific capacitance of 901 F g(-1) at 1 A g(-1) in 1 M H2SO4 electrolyte and outstanding capacitance retention of ∼91% after 3000 cycles at a high current density of 10 A g(-1), which is superior to the electrochemical performance of most reported PANI-based pseudocapacitors in literature. The enhanced electrochemical performance demonstrates the complementary contributions of both componential structures in the hybrid electrode design. Also, this work propels a new direction of utilizing porous matrix as the highly effective support for polymers toward efficient energy storage.

Rational Design of Metal‐Organic Framework Derived Hollow NiCo2O4 Arrays for Flexible Supercapacitor and Electrocatalysis

“…A Pt plate is used as the counter electrode, and an Hg/HgO is used as the reference electrode. [44][45][46] From the CV curves of CC@ NiCo 2 O 4 , the peak positions only shift a little when the scan rate increased from 5 to 100 mV s −1 , indicating that the electrode has very good reversibility. For comparison, the solid Co 3 O 4 nanowalls on carbon cloth (noted as CC@Co 3 O 4 ) obtained by directly annealing the Co-MOF precursor in air is also tested, and detailed characterization of the solid Co 3 O 4 nanowalls can be found in Figure S3 (Supporting information).…”

NiCo2S4@NiMoO4 Core-Shell Heterostructure Nanotube Arrays Grown on Ni Foam as a Binder-Free Electrode Displayed High Electrochemical Performance with High Capacity

“…Transition metal oxides have several advantages over other pseudocapacitive materials owning the properties of low toxicity, low cost, and natural abundance [11]. Among these transition metal oxides studied so far, ternary metal oxides, like NiCo 2 O 4 [12], CuCo 2 O 4 [13], NiMoO 4 [14], CoMoO 4 [15], and so on, can provide much higher electrical conductivity and richer electrochemical active sites than their single components, and they have been widely studied in the electrochemical energy field [12–15]. Although great progress has been made on ternary metal oxides electrodes to improve their electrochemical performance, these electrode materials still suffer from insufficient conductivity, slow ion diffusion rates, and serious volume change during the electrochemical procedure, which limit their further application for improving the performance of supercapacitors [16, 17].…”

Phase Transitions of Polyaniline Induced by Electrochemical Treatment

“…Potential‐induced phase changes in an electroactive material can be connected with several factors: a cracking of a material can lead to a dramatic rise in the electrode resistance and a rapid loss in the cycling stability . Moreover, the electrical conductivity of PANI becomes lower at a reduced state, which causes large electrode polarization and poor rate capability . To determine the resistivity of the PANI film (the reciprocal of conductivity), we performed electrochemical impedance spectroscopy measurements under various constant potentials: from 0 to 0.7 V, and the results are presented in Figure S5 in the Supporting Information.…”

“…To overcome the poor mechanical stability of PANI during electrochemical processes, 3D PANI networks (semiconducting polymer gels) have been prepared . Additionally, to improve the mechanical stability and performance of polyaniline, the polymer was deposited as a thin layer on top of a NiCo 2 O 4 /carbon cloth substrate, and it was demonstrated that in such a case, the overall morphology of polyaniline did not change, even after 500 repeated cycles . Polypyrrole, another member of the semiconducting polymer family, combined with cellulose similarly exhibited excellent cycling stability with no changes in the morphology of the electrode material after 4000 galvanostatic cycles …”