Oxygen-Vacancy Abundant Nanoporous Ni/NiMnO₃/MnO₂@NiMn Electrodes with Ultrahigh Capacitance and Energy Density for Supercapacitors

Abstract

High-performance energy storage devices (HPEDs) play a critical role in the realization of clean energy and thus enable the overarching pursuit of nonpolluting, green technologies. Supercapacitors are one class of such lucrative HPEDs; however, a serious limiting factor of supercapacitor technology is its sub-par energy density. This report presents hitherto unchartered pathway of physical deformation, chemical dealloying, and microstructure engineering to produce ultrahigh-capacitance, energy-dense NiMn alloy electrodes. The activated electrode delivered an ultrahigh specific-capacitance of 2700 F/cm3 at 0.5 A/cm3. The symmetric device showcased an excellent energy density of 96.94 Wh/L and a remarkable cycle life of 95% retention after 10,000 cycles. Transmission electron microscopy and atom probe tomography studies revealed the evolution of a unique hierarchical microstructure comprising fine Ni/NiMnO3 nanoligaments within MnO2-rich nanoflakes. Theoretical analysis using density functional theory showed semimetallic nature of the nanoscaled oxygen-vacancy-rich NiMnO3 structure, highlighting enhanced carrier concentration and electronic conductivity of the active region. Furthermore, the geometrical model of NiMnO3 crystals revealed relatively large voids, likely providing channels for the ion intercalation/de-intercalation. The current processing approach is highly adaptable and can be applied to a wide range of material systems for designing highly efficient electrodes for energy-storage devices.

Single-step, in-situ fabrication of flower-like NiCuMn hybrid oxyhydroxide electrodes for enhanced supercapacitor performance

“…Ni 2 O 3 (Ni 3+ -855.9 ± 0.2 eV) was observed with shakeup satellite peak for both the specimen. The presence of metallic nickel was also found on the AsC specimen and additionally NiO (Ni 2+ -854.3 ± 0.2 eV) was observed in the AsC OP @5 specimen [25]. The Cu-2p spectra confirms the presence of CuO (Cu 2+ -933.5 ± 0.2 eV) and Cu 2 O (Cu + -932.5 ± 0.2 eV) for both the AsC and AsC OP @5 specimen [26,27].…”

Flexible, Thermally Stable, and Ultralightweight Polyimide-CNT Aerogel Composite Films for Energy Storage Applications

“…The water contact angle measurements for the aerogels, shown in Figure S9, confirmed their superhydrophilic nature, indicating excellent contact between the electrode and the electrolyte. This is crucial for good electrochemical performance as it minimizes the contact and charge transfer resistance . The nanoporous structure of the electrodes, as observed from the SEM images, ensures a small ion diffusion path.…”

“…This is crucial for good electrochemical performance as it minimizes the contact and charge transfer resistance. 75 The nanoporous structure of the electrodes, as observed from the SEM images, ensures a small ion diffusion path. The presence of CNTs enhances the electrical conductivity of the samples, thus providing them with excellent electrochemical performance.…”

The role of Mn in widening the potential window of solid solution derived electrodes for aqueous supercapacitors

“…21 Some research studies and our previous studies have found that NiMnO-based electrodes derived from solid solution alloys could display this special electrochemical performance and facilitate the capacitance enhancement. [22][23][24] Nevertheless, just chemical synthesis or doping cannot achieve continuous redox reactions. 25,26 The reason why this kind of electrode can exhibit such a special electrochemical performance and its energy storage mechanism are still unknown.…”