Mesoporous Mn₃ O₄ Nanobeads/Graphene Hybrids: Facile Gel-Like Film Synthesis, Rational Structure Design, and Excellent Performance for Lithium Storage

Abstract

721wileyonlinelibrary.com www.particle-journal.com www.MaterialsViews.com COMMUNICATION mechanical fl exibility, and high lithium storage capacity (744 mAh g −1 ). [ 9 ] All these attractive features could greatly improve the electronic conductivity, and increase the surface area of electrodes for higher rate capability. It is reasonable and effi cient to combine the nanotechnology, mesoporous structure, and GNS for high-performance anode materials. [ 10 ] To the best of our knowledge, the preparation of mesoporous Mn 3 O 4 /GNS nanohybrids (M-Mn 3 O 4 /GNS) is still a challenge and no related works were reported up to today. Herein, we introduced a novel and facile gel-like fi lm (GF) synthetic approach toward uniformly dispersed mesoporous Mn 3 O 4 nanobeads (20-50 nm) on the GNS surface. Profi ting from the unique structures, the obtained M-Mn 3 O 4 /GNS exhibited an extremely high reversible capacity (1135 mAh g −1 at 100 mA g −1 after 240 cycles, without any loss) and good rate performances. The GF synthetic method is facile and template-free, and might provide a new path to fabricate mesoporous GNS-based nanocomposites. Moreover, the promising architecture can enlighten us on maximizing the potentials of active materials for lithium storage, supercapacitors, Li-air batteries, and other fi elds with electrochemical catalysts.The M-Mn 3 O 4 /GNS nanohybrids were fabricated by a facile GF method. In conventional methods for GNS-based composites, it is generally necessary and benefi cial to modify the GNS surface with negatively charged groups such as COOH, OH, and NH 2 . [ 11 ] By contrast, the GF method was more facile, without the modifi cation of GNS ahead and involving only two steps: solvothermal and hydrothermal reactions ( Scheme 1 ). During the solvothermal treatment, ethylene glycol functioned as a chelating and dispersing agent at the same time. The C O groups of ethylene glycol possess a pair of electrons and its ability to be a donor of oxygen atoms that enable it to couple with Mn 2+ ions and to form a thermodynamically favorable polymer complex as a Mn-containing gel-like fi lm (MGF) located on the GNS surface. [ 12 ] During the subsequent hydrothermal reaction, the MGF can transform into mesoporous Mn 3 O 4 nanobeads with the help of H 2 O 2 .The morphology and components of the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energydispersive spectrometer (EDS), and Fourier-transform infrared apectroscopy (FT-IR) to confi rm the GF method mentioned above. As shown Figure 1 , all the peaks of GNS, M-Mn 3 O 4 / GNS, nonporous Mn 3 O 4 /GNS (N-Mn 3 O 4 /GNS), and pure Mn 3 O 4 were in good agreement with the standard cards of GNS and tetragonal spinel Mn 3 O 4 (JCPDS 24-0734), indicating that no impurity existed. For MGF/GNS, the sharp peaks located at around 26° belonged to the commercial few-layered GNS,

High Performance Metal Oxide–Graphene Hybrid Nanomaterials Synthesized via Opposite‐Polarity Electrosprays

“…At 0.1 C rate (80 mA g −1 ), the capacity is approximately 875 mAh g −1 , which is near the theoretical limit of Mn 3 O 4 . Our Mn 3 O 4 –graphene hybrid material exhibits good charging/discharging rate capability, delivering a specific capacity of ≈600 mAh g −1 at 1.0 C rate, which is one of the highest capacities for Mn 3 O 4 ‐based materials at 1.0 C reported in the literature to date . At a high rate of 5.0 C, the capacity of the anode can still maintain over 400 mAh g −1 .…”

Graphene‐Encapsulated Nanosheet‐Assembled Zinc–Nickel–Cobalt Oxide Microspheres for Enhanced Lithium Storage

“…More interestingly, the high, reversible capacity and good cycling stability performances are even better than those of many other TMO/GNS hybrid electrodes reported in the literature (Table S2 in the Supporting Information). Additionally, it is striking to note that the measured specific capacities of the composite electrode at 0.1 C are higher than that of the theoretical capacity of bulk ZNCO (975 mA h g −1 ) and GNS (744 mA h g −1 ); this has also been widely observed in other nanostructured TMO/GNS hybrids and TMOs . These results can probably be ascribed to the positive synergistic effect between ZNCO and GNS, the larger electrochemically active surface area of GNS, and the insertion of lithium ions into interfacial storage that originates from the unique mesoporous features of ZNCO microspheres associated with the reversible formation/dissolution of a polymeric gel‐like film resulting from electrolyte degradation …”

Electrochemical performance of Mn 3 O 4 nanorods by N‐doped reduced graphene oxide using ultrasonic spray pyrolysis for lithium storage

“…[7][8][9][10][11] Among metal oxides, manganese oxide (Mn 3 O 4 ) with a theoretical capacity of 936 mAh/g (approximately 3-times higher capacity than commercial graphite anodes), low cost, eco-friendliness, and low oxidation potential (approximately 1.25 V) has attracted favorable attention. [11][12][13][14] Furthermore, it can be widely utilized in various fields, such as supercapacitors, 2,15 H 2 O 2 decomposition catalysts, 16 and oxygen reduction reaction catalysts. 17,18 However, Mn 3 O 4 still has several issues, including (a) intrinsically poor electrical conductivity (10 −7 -10 −8 S/cm) that confines the rate capability, and (b) the severe volume change during the charge/discharge process.…”