Stable Low‐Current Electrodeposition of α‐MnO₂ on Superaligned Electrospun Carbon Nanofibers for High‐Performance Energy Storage

Abstract

Metal oxide/carbonaceous nanomaterials are promising candidates for energy-storage applications. However, inhomogeneous mass and charge transfer across the electrode/electrolyte interface due to unstable metal oxide/carbonaceous nanomaterial synthesis limit their performance in supercapacitors. Here, it is shown that the above problems can be mitigated through stable low-current electrodeposition of MnO on superaligned electrospun carbon nanofibers (ECNFs). The key to this approach is coupling a self-designed four steel poles collector for aligned ECNFs and a constant low-current (40 µA) electrodeposition technique to form a uniform Na -induced α-MnO film which proceeds by a time-dependent growth mechanism involving cluster-"kebab" structures and ending with a compact, uniform MnO film for high-performance energy storage.

Magnetic Field‐Enhanced 4‐Electron Pathway for Well‐Aligned Co3O4/Electrospun Carbon Nanofibers in the Oxygen Reduction Reaction

“…The growth of the metal oxide film can be analyzed by controlled current electrodeposition kinetics . A general three‐step growth model has been derived according to the measured results, and the Co 3 O 4 thickness ( h ) versus deposition time ( t ) could be best fit as follows [Equation (2); see the Supporting Information for details]: …”

“…The growth of the metal oxide film can be analyzed by controlled current electrodeposition kinetics. [38] Ag eneral three-step growth model has been derived according to the measured results, and the Co 3 O 4 thickness (h)v ersus deposition time (t) could be best fit as follows[ Equation (2);s ee the Supporting Information for details]: [39] h ¼ h max =ð1 þ 10 t 0:5 ÀtÞ ð Þðt > 0Þ ð2Þ with h max % 851 nm and the half-life time constant t 0.5 % 3.59 h. The time-dependent growth analysiss uggests at hree-step kinetics mechanism for the electrodeposition (Figure 3c). The first step involves thin filmf ormation on ab oundary layer distributed alongt he fibers (0-2 h).…”

Block copolymer derived uniform mesopores enable ultrafast electron and ion transport at high mass loadings

“…With a thickness of <10 nm 22 or at a mass loading of <0.35 mg cm −2 on the model supports 23,26 , MnO 2 exhibits fast electron/ion transport and the gravimetric capacitances approach the theoretical limit. Nevertheless, when the conventional lightweight carbon supports are loaded with MnO 2 , they either suffer from a limited surface area for depositing a large amount of MnO 2 thin layers ( e.g ., carbon cloth 11,12 , carbon fibers 16,28–30 and other macroporous carbons 13,14 ), or they lack desirable porous structures that facilitate rapid ion diffusion across long distances to maintain high rate capability ( e.g ., microporous carbons 5,15,31 ).…”

Ordering Heterogeneity of [MnO6] Octahedra in Tunnel-Structured MnO2 and Its Influence on Ion Storage

“…Also illustrated inside the brackets are the angstrom-scale size of each M 3 N, making MnO 2 polymorphs ideal for application in ion transport and storage, such as rechargeable ion batteries. [6][7][8] For larger tunnels such as the 2 3 2 tunnels and 3 3 3 tunnels, the large opening typically requires the presence of hydrated cations (pink spheres) within the tunnel to prevent structural collapse. 9,10 The highly polymorphic nature of tunnel MnO 2 has attracted substantial effort aiming to develop a specific tunnel phase with uniform tunnel size for energy storage applications, and to further establish the tunnel structure-property relationship.…”