Nano-Sized Structurally Disordered Metal Oxide Composite Aerogels as High-Power Anodes in Hybrid Supercapacitors

Abstract

A general method for preparing nano-sized metal oxide nanoparticles with highly disordered crystal structure and their processing into stable aqueous dispersions is presented. With these nanoparticles as building blocks, a series of nanoparticles@reduced graphene oxide (rGO) composite aerogels are fabricated and directly used as high-power anodes for lithium-ion hybrid supercapacitors (Li-HSCs). To clarify the effect of the degree of disorder, control samples of crystalline nanoparticles with similar particle size are prepared. The results indicate that the structurally disordered samples show a significantly enhanced electrochemical performance compared to the crystalline counterparts. In particular, structurally disordered Ni FeO @rGO delivers a capacity of 388 mAh g at 5 A g, which is 6 times that of the crystalline sample. Disordered Ni FeO @rGO is taken as an example to study the reasons for the enhanced performance. Compared with the crystalline sample, density functional theory calculations reveal a smaller volume expansion during Li insertion for the structurally disordered Ni FeO nanoparticles, and they are found to exhibit larger pseudocapacitive effects. Combined with an activated carbon (AC) cathode, full-cell tests of the lithium-ion hybrid supercapacitors are performed, demonstrating that the structurally disordered metal oxide nanoparticles@rGO||AC hybrid systems deliver high energy and power densities within the voltage range of 1.0-4.0 V. These results indicate that structurally disordered nanomaterials might be interesting candidates for exploring high-power anodes for Li-HSCs.

Niobium‐Based Oxides Toward Advanced Electrochemical Energy Storage: Recent Advances and Challenges

“…HSCs are made up of capacitor‐type cathode and battery‐type anode. However, the slow redox reactions derived from battery‐type anodes hinder the electrochemical performances of the overall HSCs . Superior intercalation‐type anode materials own fast charge–discharge storage capability, which is expected to settle the problem.…”

Black Titania with Nanoscale Helicity

“…In contrast to the white TiO 2 /C, a longer slope with a short plateau during charging is observed for the black TiO 2− x /C, suggesting a more efficient Li + insertion within the black TiO 2− x ‐based nanostructure . The structurally disordered outer layer in the black TiO 2− x may also significantly contribute to the enhanced electrochemical performance compared to the crystalline white TiO 2 counterpart as amorphous regions suffer lower polarization and volume expansion during cycling . Ex situ PXRD analyses (Figure d) of the discharged black TiO 2− x /C showed broader diffraction peaks with lower intensity for the black anatase TiO 2− x component in comparison with the bare black TiO 2− x .…”

An advanced cathode material for high-power Li-ion storage full cells with a long lifespan

“…[1][2][3][4][5] Inspired by this trend, the development of high-rate Li-ion battery (LIB) anode materials has progressed at an unprecedentedly high speed over the last decade. [6][7][8][9][10][11][12][13][14] However, the research on high-power cathodes, as the pairing counterpart of the anodes, is signicantly lagging behind.…”

“…[19][20][21][22] The high rate capability of AC as the cathode resulted in the emergence of high-power supercapacitors (SCs) and Li-ion hybrid supercapacitors (Li-HSCs). 11,[23][24][25][26][27][28][29][30] As the capacitive storage mechanism is a surface effect, the energy storage capability of AC is limited by its accessible surface area. Therefore, the high power density of SCs and HSCs comes at the cost of low energy density.…”

“…Furthermore, conventional strategies for improving the ionic diffusion kinetics of electrode materials usually involve nanoscaling and complex nanostructural design to shorten the diffusion distance, 11,[42][43][44][45][46][47][48] which oen complicates large-scale manufacturing. Even without downsizing the particles, anode materials of niobium oxide 49 and niobium tungsten oxides 50 have been reported to possess fast ion storage kinetics mainly related to the crystal structure rather than to the diffusion length.…”