In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

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A review of electrode materials for electrochemical supercapacitors

Li-ion battery materials: present and future

Herein we report on the synthesis of two-dimensional transition metal carbides and carbonitrides by immersing select MAX phase powders in hydrofluoric acid, HF. The MAX phases represent a large (>60 members) family of ternary, layered, machinable transition metal carbides, nitrides, and carbonitrides. Herein we present evidence for the exfoliation of the following MAX phases: Ti2AlC, Ta4AlC3, (Ti0.5,Nb0.5)2AlC, (V0.5,Cr0.5)3AlC2, and Ti3AlCN by the simple immersion of their powders, at room temperature, in HF of varying concentrations for times varying between 10 and 72 h followed by sonication. The removal of the “A” group layer from the MAX phases results in 2-D layers that we are labeling MXenes to denote the loss of the A element and emphasize their structural similarities with graphene. The sheet resistances of the MXenes were found to be comparable to multilayer graphene. Contact angle measurements with water on pressed MXene surfaces showed hydrophilic behavior.

Two-dimensional transition metal carbides.

Graphene oxide: preparation, functionalization, and electrochemical applications.

Capacitive energy storage is technologically attractive because of its short charging times and its ability to deliver more power than batteries. The capacitive charge-storage properties of mesoporous films of MoO3 with iso-oriented grains now lead to pseudocapacitive materials that offer increased energy density while still maintaining high power density.

Ordered mesoporous [alpha]-MoO3 with iso-oriented nanocrystalline walls for thin-film pseudocapacitors

Nitrogen-doped carbon materials

Carbon foam: Preparation and application

Carbon materials for electrodes of capacitive deionization (CDI) process are reviewed. Electrochemical cells are briefly explained by classifying into conventional, membrane and flow-electrode CDI cells. CDI performance of carbon materials, porous carbons, including activated carbons (ACs), activated carbon fibers (ACFs), templated nanoporous carbons, carbon aerogels, carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphenes, have been reviewed in detail. The feasibility of CDI techniques is then discussed on the basis of the experimental results reported.

Carbon electrodes for capacitive deionization

A review of the control of pore structure in MgO-templated nanoporous carbons

New carbon materials have recently been derived from graphene theoretically and experimentally, hydrogenated graphene (graphane), fluorinated graphene (fluorographene), oxidized graphene (graphene oxide), and graphene introduced by acetylenic chains (graphyne and graphdiyne), which may be called graphene derivatives. Here, we review these graphene derivatives by emphasizing the experimental results.

Michio Inagaki

Papers

Nitrogen-doped carbon materials

Carbon foam: Preparation and application

Carbon electrodes for capacitive deionization

A review of the control of pore structure in MgO-templated nanoporous carbons

Graphene derivatives: graphane, fluorographene, graphene oxide, graphyne and graphdiyne