Pushing the cycling stability limit of hierarchical metal oxide core/shell nanoarrays pseudocapacitor electrodes by nanoscale interface optimization

Abstract

Three-dimensional hierarchical metal oxide core/shell nanowire arrays (HMONAs) have become promising pseudocapacitive materials due to their integrated smart architectures. However, these core/shell nanostructures have unsatisfactory structural stability and frequently suffer destruction during their fabrication process and their charge-discharge cycles, thus limiting their application lifespan. Herein, a general strategy based on the minimization of the lattice mismatch between the shell and the backbone at the nanoscale interface has been proposed to improve the cycling stability of the HMONAs. This strategy is achieved by a facile hydrothermal pretreatment under mild acidic condition, where a selective dissolution process occurs for interface optimization. To prove the concept, three typical HMONAs, α-MnO nanotube@δ-MnO nanosheet core/shell arrays, α-MnO nanotube@NiO nanosheet core/shell arrays and CoO@MnO core/shell nanoarrays, were synthesized for interface optimization. It was found that these thermodynamically unstable nanostructures in the shells of HMONAs can be selectively dissolved under a hydrothermal process, leading to enhanced stability of HMONAs. The comparison study indicates that all treated HMONAs exhibit excellent capacitance retention of 93.2% (MnO@MnO), 94.3% (MnO@NiO) and 95.3% (CoO@MnO) after 5000 cycles, which are 22.9%, 9.3% and 20.1% higher, respectively, than those of the untreated HMONAs. Furthermore, the symmetrical supercapacitors based on treated MnO@MnO nanoarrays electrodes also demonstrate 92% capacitance retention after 5000 cycles, showing better comprehensive performance than their untreated counterpart (78% capacitance retention). The general strategy of nanoscale interface optimization provides new opportunities in pushing the cycling stability limit of HMONAs.

NiCo2S4 Nanotrees Directly Grown on the Nickel NP-Doped Reduced Graphene Oxides for Efficient Supercapacitors

“…Even after tests of 10,000 charge/discharge cycles, specific capacitance was retained as 91.6% (see Figure S4 for comparative performance of similar electrode materials). This enhanced cyclic stability can be attributed to the enhanced interfacial compatibility between the vertically grown NiCo 2 S 4 and the rGOs thanks to the doped Ni ions, with increased conductivity from the contributions of rGOs [23]. Figure 6b displays Nyquist plots of the NiCo 2 S 4 /Ni-rGO before and after 10,000 cycles of charge/discharge in the frequency range of 0.01 Hz to 100 kHz.…”

Interfacial Titanium Diffusion Self-Adapting Layer in Ultrathin Epitaxial MnO2/TiO2 Heterostructures

“…The red dashed line in Figure c shows the tendency of the out-of-plane lattice parameter to increase with the thickness of the MnO 2 film ( a 0 = b 0 = 0.442 nm, c 0 = 0.287 nm) with the tensile strain grown on the substrate . However, the strain effect caused by the lattice mismatch between MnO 2 and substrate usually weakens the electrochemical performance . To obtain a high specific capacitance in thinner samples, a self-adapting layer was designed by taking advantage of the easy diffusion of metal at high temperature in vacuum to alleviate the constraint strain on thin films.…”

Novel dealloying-fabricated NiCo2S4 nanoparticles with excellent cycling performance for supercapacitors

“…As a form of energy storage equipment, supercapacitors have been the focus of research due to their extremely high power density, superior cycle stability and long life span and devices have demonstrated excellent electrochemical performances [2][3][4]. Depending on the distinctions of charge storage mechanism, supercapacitors generally include electrochemical double layer capacitors (EDLCs) [5] and pseudocapacitors [6][7][8][9]. Due to the superior electrical conductivity and enhanced stability of cobalt sulfides (CoS 2 ) [10], nickel sulfides (NiS, NiS 2 ) [11][12][13][14] and nickel cobalt sulfides [15], these transition metal sulfur compounds are investigated as novel pseudocapacitor electrode materials.…”