A Flexible Film toward High‐Performance Lithium Storage: Designing Nanosheet‐Assembled Hollow Single‐Hole Ni–Co–Mn–O Spheres with Oxygen Vacancy Embedded in 3D Carbon Nanotube/Graphene Network

Abstract

Ternary transition metal oxides (TMOs) are highly potential electrode materials for lithium ion batteries (LIBs) due to abundant defects and synergistic effects with various metal elements in a single structure. However, low electronic/ionic conductivity and severe volume change hamper their practical application for lithium storage. Herein, nanosheet‐assembled hollow single‐hole Ni–Co–Mn oxide (NHSNCM) spheres with oxygen vacancies can be obtained through a facile hydrothermal reaction, which makes both ends of each nanosheet exposed to sufficient free space for volume variation, electrolyte for extra active surface area, and dual ion diffusion paths compared with airtight hollow structures. Furthermore, oxygen vacancies could improve ion/electronic transport and ion insertion/extraction process of NHSNCM spheres. Thus, oxygen‐vacancy‐rich NHSNCM spheres embedded into a 3D porous carbon nanotube/graphene network as the anode film ensure efficient electrolyte infiltration into both the exterior and interior of porous and open spheres for a high utilization of the active material, showing an excellent electrochemical performance for LIBs (1595 mAh g−1 over 300 cycles at 2 A g−1, 441.6 mAh g−1 over 4000 cycles at 10 A g−1). Besides, this straightforward synthetic method opens an efficacious avenue for the construction of various nanosheet‐assembled hollow single‐hole TMO spheres for potential applications.

Tungsten Oxide/Reduced Graphene Oxide Aerogel with Low‐Content Platinum as High‐Performance Electrocatalyst for Hydrogen Evolution Reaction

“…The enlarged interlayer distance of the reduced GO nanosheets compared to that of pristine graphite (∼0.34 nm at 2θ ≈26°) can be ascribed to the existence of residual oxygen contained in the reduced GO interlayers. [40,41] Moreover, the electron paramagnetic resonance (EPR) spectroscopy of the WGA shows an obvious signal at g = 2.006, which can be attributed to an unpaired electron trapped in oxygen vacancy sites of tungsten trioxide, [42,43] hence demonstrating the presence of oxygen vacancy sites in the WO 3-x nanowires (Figure 1d). Information on the specific surface areas and porosities of the as-prepared WGA and GA were obtained by the analysis of their N 2 physisorption isotherms (Figure S2a and S2b).…”

Highly Efficient Capacitive Deionization Enabled by NiCo4MnO8.5 Electrodes

“…The subpeaks related to Co 2+ are located at ≈780.9 and 796.2 eV, while the subpeaks associated with Co 3+ are captured at ≈779.8 and 794.7 eV. [ 29 , 30 ] Figure 2e shows the Mn 2p spectrum, evidencing two characteristic peaks at 642.3 and 654.2 eV which correspond to Mn 2p 3/2 and Mn 2p 1/2 , respectively. The subpeaks at ≈653.5 and 641.8 eV can be attributed to the presence of Mn 2+ , while the subpeaks at ≈655.5 and 643.9 eV are related to Mn 3+ .…”

“…The subpeaks at ≈653.5 and 641.8 eV can be attributed to the presence of Mn 2+ , while the subpeaks at ≈655.5 and 643.9 eV are related to Mn 3+ . [ 30 , 31 ] The spectrum of O 1s (Figure 2f ) reveals the electron states of three kinds of oxygen. Specifically, the peak at 529.4 eV represents the metal‐oxygen bonds while the peak at 531.2 eV is usually associated with the surface species, i.e., hydroxyls.…”

Recent Developments of Two-Dimensional Anode Materials and Their Composites in Lithium-Ion Batteries

“…The diffusion of ions and electrons in 2D materials is almost independent of other conditions, which can transport rapidly in the channel. Therefore, 2D nanomaterials have gradually become promising candidates for LIBs. − …”