Metal Oxides and Oxysalts as Anode Materials for Li Ion Batteries

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

Design and fabrication of electrochemical energy storage systems with both high energy and power densities as well as long cycling life is of great importance. As one of these systems, Battery-supercapacitor hybrid device (BSH) is typically constructed with a high-capacity battery-type electrode and a high-rate capacitive electrode, which has attracted enormous attention due to its potential applications in future electric vehicles, smart electric grids, and even miniaturized electronic/optoelectronic devices, etc. With proper design, BSH will provide unique advantages such as high performance, cheapness, safety, and environmental friendliness. This review first addresses the fundamental scientific principle, structure, and possible classification of BSHs, and then reviews the recent advances on various existing and emerging BSHs such as Li-/Na-ion BSHs, acidic/alkaline BSHs, BSH with redox electrolytes, and BSH with pseudocapacitive electrode, with the focus on materials and electrochemical performances. Furthermore, recent progresses in BSH devices with specific functionalities of flexibility and transparency, etc. will be highlighted. Finally, the future developing trends and directions as well as the challenges will also be discussed; especially, two conceptual BSHs with aqueous high voltage window and integrated 3D electrode/electrolyte architecture will be proposed.

https://www.onlinelibrary.wiley.com/doi/epdf/10.1002/advs.201600539

Battery-Supercapacitor Hybrid Devices: Recent Progress and Future Prospects.

The world is recently witnessing an explosive development of novel electronic and optoelectronic devices that demand more-reliable power sources that combine higher energy density and longer-term durability. Supercapacitors have become one of the most promising energy-storage systems, as they present multifold advantages of high power density, fast charging-discharging, and long cyclic stability. However, the intrinsically low energy density inherent to traditional supercapacitors severely limits their widespread applications, triggering researchers to explore new types of supercapacitors with improved performance. Asymmetric supercapacitors (ASCs) assembled using two dissimilar electrode materials offer a distinct advantage of wide operational voltage window, and thereby significantly enhance the energy density. Recent progress made in the field of ASCs is critically reviewed, with the main focus on an extensive survey of the materials developed for ASC electrodes, as well as covering the progress made in the fabrication of ASC devices over the last few decades. Current challenges and a future outlook of the field of ASCs are also discussed.

Asymmetric Supercapacitor Electrodes and Devices.

Nanostructured Fe2O3–graphene composite was successfully fabricated through a facile solution-based route under mild hydrothermal conditions. Well-crystalline Fe2O3 nanoparticles with 30–60 nm in size are highly encapsulated in graphene nanosheet matrix, as demonstrated by various characterization techniques. As electrode materials for supercapacitors, the as-obtained Fe2O3–graphene nanocomposite exhibits large specific capacitance (151.8 F g−1 at 1 A g−1), good rate capability (120 F g−1 at 6 A g−1), and excellent cyclability. The significantly enhanced electrochemical performance compared with pure graphene and Fe2O3 nanoparticles may be attributed to the positive synergetic effect between Fe2O3 and graphene. In virtue of their superior electrochemical performance, they will be promising electrode materials for high-performance supercapacitors applications.

Nanostructured Fe2O3–graphene composite as a novel electrode material for supercapacitors

In situ polymerization and mechanical, thermal properties of polyurethane/graphene oxide/epoxy nanocomposites

Graphene oxide (GO)/nitrile rubber (NBR) nanocomposites with various contents of GO were prepared by a solution-mixing method,in this study. The GO sheets were exfoliated from natural fake graphite by an improved Hummers method and could be further dispersed homogeneously in NBR matrix. The thickness and size of the GO sheets were observed by atomic force microscopy and transmission electron microscopy. The tribological properties of the GO/NBR nanocomposites were evaluated on a ring-block MRH-3 wear tester under dry sliding and water-lubricated conditions. The worn surface morphologies of the GO/NBR nanocomposites were observed by a scanning electron microscopy. It was found that under dry sliding, both the friction coefficient (COF) and specific wear rate of the nanocomposites decreased dramatically at first, then increased with increasing GO contents, while under water-lubricated condition, both the COF and specific wear rate of the nanocomposites decreased with increasing GO contents. Finally, the friction and wear mechanisms of the GO/NBR nanocomposites were tentatively proposed.

https://link.springer.com/content/pdf/10.1007%2Fs10853-011-5846-4.pdf

Preparation and tribological properties of graphene oxide/nitrile rubber nanocomposites

The full exfoliation graphene oxide (GO) nanosheets were synthesized by an improved Hummers’ method. The phenylethynyl terminated thermosetting polyimide (PI) and PI/GO nanocomposites were prepared via a polymerization of monomer reactants process. Thermogravimetric analysis indicated that the incorporation of GO increased the thermal stability of the PI at low filling content. The friction and wear testing results of the PI and PI/GO nanocomposites under dry sliding condition against GCr15 steel showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The friction and wear properties of the PI and PI/GO nanocomposites were investigated on a model ring-on-block test rig under dry sliding conditions against the GCr15 steel. Experimental results showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The optimum GO content of nanocomposite for tribological properties is 3 wt%, which could be a potential candidate for tribo-material under dry sliding condition against GCr15 steel.

In situ synthesis and thermal, tribological properties of thermosetting polyimide/graphene oxide nanocomposites

In this work, we describe our efforts to produce Mn 3 O 4 –graphene nanocomposites based on a convenient andfeasible solution based synthetic route under mild conditions. According to transmission electron microscopy (TEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) results porous Mn 3 O 4 nanocrystals (NCs), 20–40 nm in size, are uniformly deposited on both sides of the graphene nanosheet (GNS) matrix. Significantly, the as-prepared Mn 3 O 4 –graphene nanocomposites exhibit remarkable pseudocapacitive activity including high specific capacitance (236.7 F g –1 at 1 A g –1 ), good rate capability (133 F g –1 at 8 A g –1 ), and excellent cyclability (the specific capacitance only decreases by 6.32 % of the initial capacitance after 1000 cycles). The excellent pseudocapacitive performance of the Mn 3 O 4 –graphene nanocomposites electrode is probably due to the positive synergistic effects between the Mn 3 O 4 and GNS. Namely, the intimate combination of the conductive graphene network with uniformly dispersed porous Mn 3 O 4 NCs not only greatly improves the electrochemical utilization of Mn 3 O 4 , but also increases the double-layer capacitance of the graphene sheets. These characteristics make this nanocomposite a very promising electrode material for high performance supercapacitors.

Li Yuqi

Papers

Nanostructured Fe2O3–graphene composite as a novel electrode material for supercapacitors

In situ polymerization and mechanical, thermal properties of polyurethane/graphene oxide/epoxy nanocomposites

Preparation and tribological properties of graphene oxide/nitrile rubber nanocomposites

In situ synthesis and thermal, tribological properties of thermosetting polyimide/graphene oxide nanocomposites

Facile Synthesis of Porous Mn3O4 Nanocrystal–Graphene Nanocomposites for Electrochemical Supercapacitors

Li Yuqi

Papers

Nanostructured Fe2O3–graphene composite as a novel electrode material for supercapacitors

In situ polymerization and mechanical, thermal properties of polyurethane/graphene oxide/epoxy nanocomposites

Preparation and tribological properties of graphene oxide/nitrile rubber nanocomposites

In situ synthesis and thermal, tribological properties of thermosetting polyimide/graphene oxide nanocomposites

Facile Synthesis of Porous Mn3O4 Nano­crystal–Graphene Nanocomposites for Electrochemical Supercapacitors

Facile Synthesis of Porous Mn3O4 Nanocrystal–Graphene Nanocomposites for Electrochemical Supercapacitors