Vertically-aligned graphene@MnO nanosheets as binder-free high-performance electrochemical pseudocapacitor electrodes

Abstract

Highly efficient energy storage systems are in great demand for power source applications ranging from wearable electronics to hybrid electric vehicles. Graphene-based hybrid structure capacitors are ideal candidates for manufacturing these systems. Herein, we present the design and fabrication of heterostructured composites made of vertically aligned graphene nanosheets (VAGN) and MnO nanoparticles. Electrodes with various MnO mass contents were obtained by depositing nanosized MnO particles onto VAGN under different hydrothermal conditions. The VAGN served as an excellent backbone and electron collector, enhancing the specific capacitance of the VAGN/MnO electrode (37 wt% MnO) to 790 F g À1 at a scan rate of 2 mV s À1 . The electrodes also showed high specific capacitance (381 F g À1 ) with high active material loading content (80 wt% MnO), and outstanding cycling stability (80% retention after 4000 cycles at 10 A g À1 ). These excellent electrochemical performances result from the particular three-dimensional structure of VAGN, which offers convenient access for electrolyte cations participating in the redox reaction of MnO. These composites show enormous potential for use in energy management applications.

Carbon-Anchored MnO Nanosheets as an Anode for High-Rate and Long-Life Lithium-Ion Batteries

“…Then, the cross-linked F127 with well-dispersed structure was in stiu carbonizated into carbon sheets at a high temperature of 700 °C under N 2 atmosphere. If the freeze-drying process was not used, the carbon obtained directly from the carbonizing of F127 exhibits an irregular bulk morphology with rare sheets ( Figure S1 32 The other two obvious peaks at 1321.5 and 1592.0 cm -1 can be ascribed to typical D and G bands of carbon, respectively. [33][34][35][36] Besides, in order to further understand the interaction between MnO and carbon, the X-ray absorption near-edge structure (XANES) spectrum was applied to investigate the electronic structure of the typical MnO/C hybrid (Figure 2c).…”

Vertical‐Aligned Li2S–Graphene Encapsulated within a Carbon Shell as a Free‐Standing Cathode for Lithium–Sulfur Batteries

“…For instance, carbonaceousm aterials (e.g., carbon black, polyacrylonitrile and polypyrrole) have been employeda st he conductive matrix/host to improvet he electrical conductivity of Li 2 Sa nd enhanceg ood electrochemical performance. Moreover, the strong p-p interactions and the van der Waals force between the planar basal planes would cause restacking of the rGO, [40][41][42] greatly reducing the active sites and transfer channels for ions/electrons. [35][36][37][38] Wu et al prepared reduced grapheme oxide (rGO)-Li 2 Sc omposites through av ersatile solution-based method and achieved pronounced electrochemical performance.…”

Integration of MnO@graphene with graphene networks towards Li-ion battery anodes

“…Core-shell structures hardly suppress the volume changes in anodes during battery cycling. TMO/ graphene composites have been suggested as advanced anodes, [20][21][22][23] since elastic graphene sheets can accommodate the volume changes during battery cycling, although they usually show poor electrical conductivity, because there are junction contact resistances and structural defects in ultrathin nanosheets derived from the chemical synthesis process. 30 Thus, it is still a big challenge to construct MnO-based anodes that address both the electrical conductivity and the volume change problems.…”

“…Two intrinsic problems exist, however, for MnO-based anodes, low electrical conductivity and large volume changes during battery cycling, which lead to low coulombic efficiency and cyclability. To solve these problems, much effort has been devoted to constructing MnO@C coreshell composites, [14][15][16][17][18][19] MnO/graphene composites, [20][21][22][23] and MnO/ carbon composites, [24][25][26][27][28][29] which could potentially accommodate the volume changes. Core-shell structures hardly suppress the volume changes in anodes during battery cycling.…”